CN115313457B - Battery energy storage system - Google Patents
Battery energy storage system Download PDFInfo
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- CN115313457B CN115313457B CN202210983389.0A CN202210983389A CN115313457B CN 115313457 B CN115313457 B CN 115313457B CN 202210983389 A CN202210983389 A CN 202210983389A CN 115313457 B CN115313457 B CN 115313457B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for AC mains or AC distribution networks
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
- H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
- H02J13/00002—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by monitoring
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
- H02J13/00004—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by the power network being locally controlled
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for AC mains or AC distribution networks
- H02J3/01—Arrangements for reducing harmonics or ripples
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
- H02J7/0014—Circuits for equalisation of charge between batteries
- H02J7/0016—Circuits for equalisation of charge between batteries using shunting, discharge or bypass circuits
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
- H02J7/0014—Circuits for equalisation of charge between batteries
- H02J7/0019—Circuits for equalisation of charge between batteries using switched or multiplexed charge circuits
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
- H02J7/00304—Overcurrent protection
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
- H02J7/00308—Overvoltage protection
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
- H02J7/00309—Overheat or overtemperature protection
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0047—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with monitoring or indicating devices or circuits
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/007—Regulation of charging or discharging current or voltage
- H02J7/00712—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/10—Flexible AC transmission systems [FACTS]
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Charge And Discharge Circuits For Batteries Or The Like (AREA)
Abstract
The invention discloses a battery energy storage system, which comprises a control system and phase circuits, wherein each phase circuit comprises a plurality of subsystems which are sequentially cascaded, and each subsystem comprises: a battery pack; the bridge type current conversion module is provided with an alternating current side and a coupling side; the coupling module is used for coupling and matching the bridge type converter module and the battery pack; the battery balancing module is used for monitoring the working state of each energy storage battery and also used for balancing the electric quantity of each battery in the battery pack in response to the balancing control signal; and the controller is used for controlling at least two of the bridge type converter module, the coupling module and the battery balancing module. The controllers in the subsystems control the working states of the subsystems according to control signals of the control systems. Therefore, adverse effects of the battery with the largest deviation in the battery pack on the energy storage performance of the battery system in the energy storage system are reduced, and reliable and safe operation of the battery energy storage system is guaranteed.
Description
Technical Field
The invention relates to the technical field of energy storage, in particular to a battery energy storage system.
Background
In the existing battery energy storage system, a centralized battery pack formed by a plurality of serial-parallel loops is mostly adopted, and the number of batteries connected in series is large, so that the defects of individual batteries can cause the faults of the whole battery pack, even the energy storage system is burnt and exploded, and serious hidden hazards exist in the service life and safety of the batteries. Each battery remains between 10% and 90% of full capacity, and deep discharge or overcharge can greatly shorten the effective life of the battery. To cope with deep discharge or overcharge, it is often required to provide under-voltage protection (Under Voltage Protection, UVP) and over-voltage protection (Over Voltage Protection, OVP) circuits to help prevent these conditions from occurring.
For a battery pack with a plurality of batteries connected in series, when the battery with the lowest capacity (small storable charge) reaches an OVP threshold, the charging process of the whole battery pack is stopped, and at the moment, other batteries are not fully charged, namely the energy storage system does not reach the maximum allowable capacity; also, when the lowest charged cell reaches the UVP limit, the entire battery pack stops working, and at this time, there is still energy in the battery pack that can power the system, but the energy storage system cannot continue to discharge for safety reasons. It follows that, for a battery system in which a plurality of batteries are connected in series, the weakest battery in the battery pack dominates the performance of the entire battery system.
In order to achieve the direct-current voltage required by the grid-connected inverter, the batteries of the current energy storage system often need 400-500 batteries to be connected in series, so that the number of the batteries connected in series is large, and the conventional equalization circuit (generally only ten batteries can be connected and equalized) cannot realize effective equalization of the electric quantity among each battery.
The existing battery management system is used for managing batteries in three stages of battery packs, battery clusters and battery systems, the battery pack stage usually only has the functions of monitoring and internal equalization, when the battery management system finds that the batteries work abnormally, the battery management system needs to report the battery management system to the system stage and the PCS system through the low-speed bus stage such as a CAN (controller area network) and the like, the operations such as tripping and energy conversion of locking PCS CAN be performed, the control aging is seriously influenced, and the phenomenon of overcharge and overdischarge of the batteries still CAN be caused. It can be seen that in the prior art, the battery pack size of the energy storage system is still large, and the battery life and safety problems are still outstanding.
When a certain part of the battery works abnormally, the whole energy storage system can be caused to stop working.
Therefore, how to fully utilize the performance of the energy storage system and improve the safety of the battery system is a technical problem to be solved.
Disclosure of Invention
Based on the above-mentioned situation, a main object of the present invention is to provide a battery energy storage system, so as to effectively balance the performance states among the batteries, so as to improve the performance and the safety of the whole battery system.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
a battery energy storage system comprising a single-phase or three-phase circuit comprising a control system and phase circuits, each phase circuit comprising a plurality of subsystems serially cascaded, the subsystems comprising:
the battery pack is obtained by connecting N energy storage batteries in series and is used for storing electric energy output by a power grid, wherein N is an integer greater than or equal to 2;
the bridge type conversion module is used for converting alternating current electric energy into direct current electric energy to be stored in the battery pack, or converting electric energy output by the battery pack into alternating current electric energy and combining the alternating current electric energy with a power grid; the bridge type current conversion module is provided with an alternating current side and a coupling side, wherein the alternating current side is used for connecting the subsystems in series in the subsystems; the bridge type current conversion module comprises an energy storage capacitor which is connected with two ends of the coupling side;
The coupling module is connected between the coupling side of the bridge type current conversion module and the battery pack and used for coupling and matching the bridge type current conversion module and the battery pack;
the battery equalization module is connected to the battery pack, and is used for monitoring the working state of each energy storage battery and equalizing the electric quantity of each battery in the battery pack in response to the equalization control signal;
the controller is connected with the control ends of the bridge type converter module, the coupling module and the battery balancing module, and can receive the working state of each energy storage battery monitored by the battery balancing module and control at least two of the bridge type converter module, the coupling module and the battery balancing module;
the control system respectively performs data interaction with controllers in all the subsystems, and the controllers in all the subsystems control bridge type converter modules, coupling modules and/or battery equalization modules in all the subsystems according to control commands of the control system so as to control working states of all the subsystems, wherein:
the control system is responsible for charge and discharge control and balance control among all subsystems, and the controller of each subsystem is responsible for balance control in the subsystem of the controller, wherein:
the control system generates a charge-discharge current reference instruction of a subsystem battery pack according to the average value of the energy storage capacitor voltage in a bridge converter module in an effective subsystem in a phase circuit;
The control system adjusts charge and discharge current instructions of the battery packs of the subsystems according to the quantity of the battery packs of the subsystems, and controls balance of the electric quantity among the battery packs of the subsystems; the electric quantity of the subsystem battery pack is higher, and in a charging state, the charging current instruction is reduced, and in a discharging state, the discharging current instruction is increased; the electric quantity of the subsystem battery pack is lower and is in a charging state, a charging current instruction is increased, and in a discharging state, a discharging current instruction is reduced;
the control system sends a battery pack charging and discharging current instruction to the controllers of all the subsystems, and the controllers of all the subsystems control the magnitude of charging or discharging current to the battery pack through the control coupling module;
and the controller of the subsystem controls the equalization module of the subsystem to realize equalization of the electric quantity of each battery in the subsystem battery pack according to the electric quantity of each battery in the subsystem battery pack.
Optionally, the battery equalization module includes: the N equalization units are in one-to-one correspondence with the N energy storage batteries; a first switching unit; the two input ends of each equalization unit are connected with the positive electrode and the negative electrode of the corresponding energy storage battery respectively, and the two output ends of the equalization units are connected with the positive electrode and the negative electrode of the battery pack;
When the voltage of the anode and the cathode of the ith energy storage battery exceeds a preset threshold, the controller outputs an equalization control signal to a first switch unit of the ith equalization unit; the ith equalization unit exchanges the electric energy of the ith energy storage battery with the electric energy of the battery pack where the ith energy storage battery is located through the input end, wherein i is more than or equal to 1 and less than or equal to N.
Optionally, the equalization unit includes: a mutual inductance coil and a second switch unit;
one end of a primary coil of the mutual inductance coil is connected to the positive electrode of the corresponding energy storage battery, and the other end of the primary coil is connected to the negative electrode of the corresponding energy storage battery through a second switch unit; one end of a secondary coil of the mutual inductance coil is connected to the positive electrode of the battery pack where the corresponding energy storage battery is located, and the other end of the secondary coil of the mutual inductance coil is connected to the negative electrode of the battery pack where the corresponding energy storage battery is located through the first switch unit;
the second switch unit and the first switch unit are conducted in response to the equalization control signal, so that the electric energy of the corresponding energy storage battery exchanges energy with the battery pack where the corresponding energy storage battery is located through the primary coil and the secondary coil of the mutual inductance coil.
Optionally, the subsystem further comprises:
the battery voltage and temperature detection module is used for detecting the battery voltage and the battery temperature of the battery pack, the battery voltage and temperature detection module is connected with the battery pack and the controller, and the controller limits the charge and discharge current of the battery pack according to the temperature and the voltage of the energy storage battery.
Optionally, the control system determines voltages required by a plurality of moments in a power frequency period according to the voltage, active and reactive requirements of the alternating current power grid, and determines the target number of subsystems required to be put into at each moment based on the voltages required by the moment and the voltage values which can be output by the subsystems;
the control system selects a target number of subsystems to enter the input state according to the state that the subsystems needing to be put into operation are in charge or discharge, and other subsystems enter a bypass state; when the subsystem is in a charging state, the control system preferentially selects the subsystem with a lower energy storage capacitor voltage value in the bridge type converter module to enter an input state; when the subsystem is in a discharging state, the subsystem with a higher voltage value of the energy storage capacitor in the bridge type converter module is preferentially selected to enter an input state.
Optionally, the control system generates a charge-discharge current reference instruction of the subsystem battery pack according to the average value of the energy storage capacitor voltage in the subsystem in the phase circuit;
the control system generates correction values of charge and discharge current instructions of the battery packs of the subsystems according to deviation of the electric quantity of the battery packs of the subsystems relative to the average electric quantity of the battery packs of the subsystems;
And adding correction values of the charge-discharge current reference command and the charge-discharge current command corresponding to each subsystem to form a final charge-discharge current command of each subsystem.
Optionally, the coupling module includes: a charge-discharge control unit;
the charge-discharge control unit includes: the first switching MOS tube, the second switching MOS tube (Q2) and the first inductor;
the second pole of the first switching MOS tube is connected with the first pole of the second switching MOS tube, and the connecting point is connected with the first end of the first inductor;
the second pole of the second switching MOS tube is connected to the negative pole end of the bridge type current conversion module and the negative pole end of the battery pack;
the first electrode of the first switching MOS tube is connected to one of the positive electrode end of the coupling side in the bridge type current converting module and the positive electrode end of the battery pack, and the second end of the first inductor is connected to the other one of the positive electrode end of the coupling side in the bridge type current converting module and the positive electrode end of the battery pack;
when the bridge type current conversion module charges the battery pack, the control electrode of the first switching MOS tube and the control electrode of the second switching MOS tube are alternately conducted with the respective first electrode and the second electrode in response to a charging control signal so as to transmit the electric energy output by the bridge type current conversion module to the battery pack;
when the battery pack discharges to the bridge type current conversion module, the control electrode of the first switching MOS tube and the control electrode of the second switching MOS tube are alternately conducted with the first electrode and the second electrode in response to a discharge control signal, so that electric energy released by the battery pack is transmitted to the bridge type current conversion module.
Optionally, when the temperature of the energy storage battery of the battery pack of the subsystem exceeds a certain threshold, or the voltage of any battery of the battery pack of the subsystem exceeds an upper limit threshold or is lower than a lower limit threshold, or the charge and discharge current of the battery pack of the subsystem exceeds a limit value, the subsystem controller outputs or makes a decision by the control system to output a bypass control signal, so that the subsystem bridge conversion module responds to the bypass control signal to short-circuit an alternating current side connected with the power grid to isolate the power grid from the battery pack; or the subsystem controller outputs a breaking signal, and the first switching MOS tube and the second switching MOS tube respectively respond to the breaking signal to break the respective first pole and second pole so as to stop the electric energy transmission of the battery pack; when a subsystem is abnormally bypassed, if the number of the remaining subsystems still meets the operation requirement of the energy storage system, the control system of the energy storage system controls the remaining subsystems to keep running.
Optionally, the coupling module includes: m charge and discharge control units connected in parallel, wherein M is more than or equal to 2, and the working phase of each charge and discharge control unit is different by 360 degrees/M in sequence;
the first poles of the first switching MOS transistors are connected in parallel;
the second poles of the second switching MOS transistors are connected in parallel;
the second ends of the first inductors are connected in parallel.
Optionally, the first pole of the first switching MOS transistor is connected to the positive pole end of the coupling side in the bridge converter module;
the second terminal of the first inductor is connected to the positive terminal of the battery pack.
Optionally, the coupling module further comprises:
the capacitor is connected between the second end of the first inductor and the second pole of the second switching MOS tube;
the second inductor is connected in series between the second end of the first inductor and the positive electrode end of the battery pack.
Optionally, the first pole of the first switching MOS transistor is connected to the positive pole of the battery pack;
the second end of the first inductor is connected to the positive end of the coupling side in the bridge converter module.
Optionally, the coupling module further comprises:
the capacitor is connected between the second end of the first inductor and the second pole of the second switching MOS tube;
the second inductor is connected in series between the second end of the first inductor and the positive end of the coupling side in the bridge type current converting module.
Optionally, the battery energy storage system is a single-phase or three-phase circuit energy storage system;
the bridge type current conversion module is realized by a full-bridge current converter;
each phase circuit comprises a bridge arm which is sequentially cascaded with a plurality of subsystems, wherein two alternating current access ends of the alternating current side of each subsystem are respectively connected with two alternating current access ends of the alternating current side of the adjacent subsystem in series; the first end of the first subsystem is connected with a phase access point of the alternating current power grid, and at least one inductor is connected in series between the subsystems and/or between the first end of the first subsystem and the access point of the alternating current power grid; the second end of the last subsystem is connected with a neutral access point of the alternating current power grid.
Optionally, the battery energy storage system is a three-phase circuit energy storage system, and the battery energy storage system further comprises a direct current power grid connection end;
the bridge type current conversion module is realized by a half-bridge current converter or a full-bridge current converter;
each phase circuit comprises an upper bridge arm and a lower bridge arm, the number of subsystems of the upper bridge arm and the lower bridge arm in cascade connection is the same, wherein:
in the upper bridge arm, two alternating current access ends of the alternating current side of each subsystem are respectively connected with two alternating current access ends of the alternating current side of the adjacent subsystem in series; at least one inductor is connected in series between a plurality of subsystems in an upper bridge arm and/or between the second end of the first subsystem and the access point of the alternating current power grid; the first end of the last subsystem is connected with the positive end of the direct current power grid;
in the lower bridge arm, two alternating current access ends of the alternating current side of each subsystem are respectively connected with two alternating current access ends of the alternating current side of the adjacent subsystem in series; at least one inductor is connected in series between a plurality of subsystems in a lower bridge arm and/or between the first end of the first subsystem and the access point of the alternating current power grid; the second end of the last subsystem is connected with the negative end of the direct current power grid.
[ beneficial effects ]
According to the embodiment of the invention, the battery energy storage system comprises a control system and phase circuits, wherein each phase circuit comprises a subsystem which is sequentially cascaded, and the subsystem comprises: the battery pack is obtained by connecting N energy storage batteries in series and is used for storing electric energy output by a power grid; the bridge type converter module is used for converting alternating current electric energy into direct current electric energy to be stored in the battery pack, or converting electric energy output by the battery pack into alternating current and combining the alternating current electric energy with a power grid; the coupling module is used for coupling and matching the bridge type converter module and the battery pack, the battery balancing module is used for monitoring the working state of each energy storage battery and responding to the balancing control signal to balance and control the electric energy of each battery in the battery pack, and therefore the cascade structure of the battery energy storage system is realized. In the embodiment of the invention, each phase unit circuit of the energy storage system is decomposed into a plurality of subsystems, and the number of batteries connected in series in each subsystem is controlled within a range which is easy to realize active balance control of the batteries. The controller of the subsystem controls the equalization module of the subsystem to realize the active equalization of the electric quantity of each battery in the subsystem battery pack according to the electric quantity of each battery in the subsystem battery pack; the energy storage control system corrects the charge and discharge current of each subsystem according to the electric quantity of the battery pack of each subsystem, so that the electric quantity among the battery packs of each subsystem is balanced; the energy storage system obtains the balance effect which is not seen by the existing energy storage system through the efficient two-stage electric quantity balance method, fully exerts the capacity of each battery in the energy storage system, and improves the utilization rate of the batteries of the energy storage system.
In addition, when the voltage of the anode and the cathode of the ith energy storage battery relative to the average voltage of the batteries in the battery pack exceeds a preset threshold value, the controller outputs an equalization control signal to a first switch unit of the ith equalization unit; and the ith equalization unit exchanges the electric energy of the ith energy storage battery with the electric energy of the battery pack where the ith energy storage battery is positioned through the input end. The balance unit realizes the redistribution of redundant energy among different batteries in the battery pack. This allows energy to be recovered and less wasted, the energy not being dissipated as heat but being re-used to charge the remaining cells in the battery. The capacity of each battery in the battery pack is fully utilized, and the utilization rate of the battery pack is improved.
In addition, the energy storage control system controls the output level of each subsystem, and the output levels of the subsystems are overlapped to obtain the voltage required by the power grid. The stepped multi-level analog sine wave voltage output reduces the switching times and switching loss of the power device, reduces the harmonic voltage and harmonic current output by the energy storage system, and improves the efficiency and the electric energy quality of the energy storage system.
Meanwhile, each subsystem is respectively provided with a controller for carrying out data interaction with the control system, so that the control of the bridge converter in the subsystem can be realized, and meanwhile, the monitoring and the balance control of the battery are finished; compared with the prior art that an independent multi-stage battery management system monitors and manages batteries and interacts with a high-capacity PCS converter to control the energy exchange mode of the battery system, the energy storage control system and controllers in all subsystems in the application not only complete the monitoring and control of the battery pack in the subsystem, but also complete the energy conversion control of the subsystem and an alternating current system, the battery management system and the PCS converter are integrated, the configuration of the energy storage system is simplified, and the occupied space of the independent PCS energy conversion system in the prior art is saved; the real-time data interaction between the subsystem and the energy storage control system improves the detection speed and the processing speed of the battery abnormality from the minute level of the traditional battery management system to the level of 100 mu S, avoids the linkage propagation of the battery abnormality and enlarges the accident. The energy storage system is divided into a plurality of subsystems, when the battery of the subsystem is abnormal or other types of faults, the energy storage system can independently bypass the fault subsystem from the energy storage system, the battery pack of the fault subsystem is protected, and the rest subsystems can still work continuously. The characteristics provide guarantee for the reliable and safe operation of the battery energy storage system.
Other advantages of the present invention will be set forth in the description of specific technical features and solutions, by which those skilled in the art should understand the advantages that the technical features and solutions bring.
Drawings
Embodiments of the present invention will be described below with reference to the accompanying drawings. In the figure:
fig. 1 is a schematic structural diagram of a three-phase circuit battery energy storage system disclosed in this embodiment;
fig. 2 is a schematic structural diagram of another three-phase circuit battery energy storage system disclosed in this embodiment;
fig. 3 is a schematic circuit diagram of an energy storage subsystem according to the present embodiment;
fig. 4 is a schematic circuit diagram of a battery equalization module 4 according to the embodiment;
fig. 5 is a schematic circuit diagram of a battery equalization module 4 according to the embodiment;
fig. 6 is a schematic diagram of an equalization control principle of the control system disclosed in the present embodiment;
FIG. 7 is a schematic diagram of a circuit configuration of another energy storage subsystem according to the present embodiment;
fig. 8 is a schematic circuit diagram of an embodiment of a third coupling module 3 disclosed in this embodiment;
fig. 9 is a schematic diagram of a current superposition process of M charge/discharge control units according to the present embodiment;
Fig. 10 is a schematic circuit diagram of an embodiment of a fourth coupling module 3 disclosed in this embodiment.
Detailed Description
The present invention is described below based on examples, but the present invention is not limited to only these examples. In the following detailed description of the present invention, certain specific details are set forth in order to avoid obscuring the present invention, and in order to avoid obscuring the present invention, well-known methods, procedures, flows, and components are not presented in detail.
Moreover, those of ordinary skill in the art will appreciate that the drawings are provided herein for illustrative purposes and that the drawings are not necessarily drawn to scale.
Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is, it is the meaning of "including but not limited to".
In the description of the present invention, it should be understood that the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. Furthermore, in the description of the present invention, unless otherwise indicated, the meaning of "a plurality" is two or more.
In the description of the invention, the MOS tube can be a MOS tube or a power device with a switching function such as an IGBT tube; for a MOS transistor, the control electrode is a gate electrode, and the second electrode is a source electrode when the first electrode is used as a drain electrode, wherein the first electrode and the second electrode can be replaced with each other; for an IGBT tube, the control electrode is a base electrode, and the second electrode is an emitter electrode when the first electrode is a collector electrode, for example, wherein the first and second electrodes can be replaced with each other.
In order to equalize performance states among batteries so as to improve performance of the whole battery pack, the embodiment discloses a battery energy storage system, which comprises a control system and a phase circuit, wherein the phase circuit can be a single-phase or three-phase circuit, and each phase circuit comprises a subsystem which is sequentially cascaded. Specifically, taking a battery energy storage system including a three-phase circuit as an example:
referring to fig. 1, a schematic structure diagram of a three-phase circuit battery energy storage system is disclosed in this embodiment, in the battery energy storage system, a bridge converter module is implemented based on a full bridge converter (see description about the bridge converter module 2 below), each phase circuit includes a bridge arm in which a plurality of subsystems are sequentially cascaded, specifically, the battery energy storage system includes a plurality of subsystems 100, an inductor 200 (with variable positions and numbers), a control system 300 and a monitor 400 in sequential cascaded, and when the battery energy storage system adopts the full bridge circuit to perform converter, each phase circuit is connected with an access point of A, B, C phases of an ac power grid after being cascaded by the plurality of subsystems 100. Specifically, two ac access terminals h1 and h2 on the ac side of each subsystem are respectively connected in series with two ac access terminals h1 and h2 on the ac side of an adjacent subsystem, two ends after cascading form a grid connection terminal, one end is connected with one phase access point of an ac grid, and the other end is connected with a neutral access point of the ac grid. At least one inductor 200 is connected in series between the plurality of subsystems and/or between the first end h1 of the first subsystem and an access point of the alternating current power grid, as shown in fig. 1, at least one inductor 200 is connected in series between the first end h1 of the first subsystem and the access point of the alternating current power grid, and h1 of the first subsystem close to the power grid side is used as an alternating current access end and is connected with a phase access point of the alternating current power grid through the at least one inductor 200; in other embodiments, at least one inductor 200 may be connected in series between the subsystems; the second end h2 of the last subsystem is used as an alternating current access end to be connected with a neutral access point of an alternating current power grid.
Referring to fig. 1, in the implementation process, the operating voltage and current of the three-phase circuit may also be monitored by the monitor 400 to determine the voltage and current output by the energy storage system.
Illustratively, the energy storage system discharges to the power grid and selectively controls the plurality of subsystems to output different selectable voltage values (+U) according to the value of the alternating voltage required to be output by each phase of circuit Subsystem capacitance voltage 、0、-U Subsystem capacitance voltage ) Wherein U is Subsystem capacitance voltage The voltage at two ends of the energy storage capacitor in the subsystem can be superposed by a plurality of subsystems to obtain a voltage value close to the output voltage of each phase of circuit, so that direct power exchange between the energy storage system and the alternating current power grid is realized. Assuming that the output voltage of each subsystem is 50V, and the voltage required to be output by a certain phase of the energy storage system is 500V at this time, the number of subsystems in the input state in the phase can be controlled to be 10, and the other subsystems are in the bypass state, so that the phase cascading circuit can output a corresponding voltage value.
In particular embodiments, various subsystems in the battery energy storage system may be uniformly coordinated controlled by the control system 300. Specifically, each subsystem configures a controller, the control system 300 and each subsystem may communicate through a communication interface, so that the control system 300 performs data interaction with the controllers in each subsystem 100, and the control system 300 controls each subsystem 100 to access the energy storage system to store energy, release energy, or bypass from the energy storage system according to the voltage and current monitoring result of the monitor 400.
It should be noted that, the plurality of subsystems in the longitudinal direction shown in fig. 1 form a bridge arm, when the battery energy storage system adopts the half-bridge circuit to perform current transformation, the energy storage system increases the direct current power grid connection end, the number of the bridge arm may be increased, and in the specific implementation process, the number of the bridge arm may be determined according to actual needs. As an example:
referring to fig. 2, a schematic structure diagram of another three-phase circuit battery energy storage system disclosed in this embodiment is shown in fig. 2, compared to fig. 1: the direct current power grid connection terminal is included; the bridge converter modules are realized by full bridge converters or by half bridge converters (see below for description of bridge converter module 2); the cascading manner of the subsystems in each phase circuit is different from that of fig. 1, specifically, each phase single-path comprises two cascading bridge arms, namely an upper bridge arm and a lower bridge arm, wherein each of the upper bridge arm and the lower bridge arm comprises at least one reactor 200 (the positions and the number of the reactors are variable) and the subsystems 100 with the same number.
In the upper bridge arm shown in fig. 2, the ac side of each subsystem 100 is sequentially connected from the ac power grid to the DC positive terminal dc+ of the DC power grid for cascading, as shown in fig. 2, two ac access terminals h1 and h2 of the ac side of each subsystem 100 are respectively connected in series with two ac access terminals h1 and h2 of the ac side of an adjacent subsystem, and two ends after cascading form two ends of the upper bridge arm. The second end h2 in the first subsystem 100 from the alternating current power grid to the positive end DC+ of the direct current power grid is used as an alternating current access end h2 to be connected with a phase access point of the alternating current power grid; at least one inductor 200 is connected in series between the plurality of subsystems and/or between the second end h2 of the first subsystem and the access point of the ac power grid, that is, at least one inductor 200 may be connected in series between the plurality of subsystems, or at least one inductor 200 may be connected in series between the first subsystem and the access point of the ac power grid; the first end h1 in the last subsystem is used as an alternating current access end to be connected with the positive end DC+ of the direct current power grid.
In the lower bridge arm shown in fig. 2, the ac side of each subsystem 100 is DC-sequentially connected from the ac power grid to the DC power grid negative end, as shown in fig. 2, two ac access ends h1 and h2 of the ac side of each subsystem 100 are respectively connected in series with two ac access ends h1 and h2 of the ac side of an adjacent subsystem, and two ends after cascading form two ends of the lower bridge arm. An ac access terminal h1 in the first subsystem 100 from the ac power grid to the DC-to-DC power grid negative terminal DC-is used as an ac access terminal h1 to connect to a phase access point of the ac power grid; at least one inductor 200 is connected in series between the subsystems in the lower bridge arm and/or between the first end h1 of the first subsystem and the access point of the alternating current power grid, that is, at least one inductor 200 may be connected in series between the subsystems, or at least one inductor 200 may be connected in series between the first subsystem and the access point of the alternating current power grid; the second terminal h2 in the last subsystem is connected as an ac access terminal to the bus voltage negative terminal DC-.
It should be noted that, a person skilled in the art may select the topology structure of fig. 1 or fig. 2 according to an actual application scenario, for example, for a new energy scenario such as a photovoltaic scenario, the topology structure of fig. 2 may be selected; the topology of fig. 1 may be selected for the scenario where the grid is only charged. Of course, the topology may also be determined according to the type of bridge converter module, for example, in the case of using a full bridge converter module, the topology of fig. 1 may be preferentially selected; for the case of half-bridge current transformation modules, the topology of fig. 2 may be preferred.
In this embodiment, please refer to fig. 3, which is a schematic diagram of a subsystem circuit structure of an energy storage system disclosed in this embodiment, the subsystem includes: the battery pack 1, the bridge type current converting module 2, the coupling module 3, the battery balancing module 4 and the controller 5, wherein:
the battery pack 1 is obtained by connecting N energy storage batteries in series and is used for storing electric energy output by a power grid, and N is an integer greater than or equal to 2. In a specific embodiment, the battery pack 1 is used for storing electrical energy of an electrical grid, or for releasing electrical energy to an electrical grid. As an application scenario, when the electric energy of the ac power grid remains in the electricity consumption valley period, the ac power grid can charge the battery pack 1 to provide electric energy for the battery pack 1 through the cooperation of each module in the energy storage system subsystem, so that part of the electric energy of the power grid is converted into electric energy in the battery pack 1; on the contrary, when the power supply is interrupted in the peak period of electricity consumption or the external power grid, the electric energy of the battery pack 1 can be released through the cooperation of each module in the energy storage system subsystem and converted into the alternating current power grid so as to compensate the electric energy of the power grid.
The bridge converter module 2 is used for converting alternating current energy into direct current energy for storage in the battery pack 1, or converting the electric energy output by the battery pack 1 into alternating current energy, and integrating the alternating current energy into a power grid. The bridge type converter module 2 is provided with an alternating current side and a coupling side, wherein the alternating current side is used for connecting the subsystems in series in a plurality of subsystems; the bridge type current conversion module 2 comprises an energy storage capacitor C1 which is connected to two ends of the coupling side; in a specific embodiment, the ac side is connected to a power grid for converting ac power to dc power for storage to the battery pack 1; or converts the electric energy output by the battery pack 1 into alternating current and incorporates the alternating current into a power grid. In a specific embodiment, the bridge current transformation module 2 may be a full bridge current transformer or a half bridge current transformer.
In order to implement equalization control of the battery pack in the same subsystem, please refer to fig. 3, where the battery equalization module 4 is connected to the battery pack, the battery equalization module 4 is configured to monitor an operation state of each energy storage battery, and is further configured to equalize electric quantities of each battery in the battery pack 1 in response to an equalization control signal. Specifically, the controller 5 is connected with the control ends of the bridge converter module 2, the coupling module 3 and the battery balancing module 4, and is capable of receiving the working state of each energy storage battery monitored by the battery balancing module 4 and controlling at least two of the bridge converter module 2, the coupling module 3 and the battery balancing module 4.
In order to realize the battery pack balancing control between different subsystems, please refer to fig. 1 (or fig. 2) and fig. 3, the control system 300 performs data interaction with the controllers 5 in each subsystem, and the controllers 5 in each subsystem control the bridge converter module 2 and the coupling module 3 in each subsystem according to the control command of the control system 300, so as to control the working states of the respective subsystems, so that the electric quantity between the battery packs of the different subsystems is relatively balanced.
In this embodiment, the control system 300 is responsible for charge and discharge control and equalization control among subsystems, and the controller 5 of each subsystem is responsible for equalization control in its own subsystem, where:
The control system 300 generates a charge and discharge current reference instruction of the subsystem battery pack 1 according to the average value of the voltage of the energy storage capacitor C1 in the bridge type converter module in the effective subsystem in the phase circuit;
the control system 300 adjusts charge and discharge current instructions of the battery packs of the subsystems according to the quantity of the electric quantity of the battery packs 1 of the subsystems, and controls the balance of the electric quantity of the battery packs 1 of the subsystems; the electric quantity of the subsystem battery pack is higher, and in a charging state, the charging current instruction is reduced, and in a discharging state, the discharging current instruction is increased; the electric quantity of the subsystem battery pack is lower and is in a charging state, a charging current instruction is increased, and in a discharging state, a discharging current instruction is reduced;
the control system 300 sends a charge and discharge current instruction of the battery pack 1 to the controllers 5 of all the subsystems, and the controllers 5 of all the subsystems control the charge or discharge current of the battery pack 1 through the control coupling module 3;
further, the controller 5 of the subsystem controls the equalization module 4 of the subsystem to realize equalization of the electric quantity of each battery in the subsystem battery pack 1 according to the electric quantity of each battery in the subsystem battery pack.
In an alternative embodiment, control system 300 determines the voltages required at a plurality of times within a power frequency period according to the voltage, active and reactive requirements of the ac power grid, and determines the target number of subsystems required to be put into at each time based on the voltages required at that time and the voltage values that can be output by each subsystem; the control system 300 selects a target number of subsystems to enter the input state according to whether the subsystems needing to be put into operation are in a charging or discharging state, and other subsystems enter a bypass state; when the subsystem is in a charging state, the control system 300 preferentially selects the subsystem with a lower energy storage capacitor voltage value in the bridge converter module 2 to enter a put-in state; when the subsystem is in a discharging state, the subsystem with a higher voltage value of the energy storage capacitor in the bridge type converter module 2 is preferentially selected to enter an input state.
In this embodiment, when the deviation between the positive and negative voltages of the ith energy storage battery and the average voltage of the batteries in the battery pack exceeds the equalization threshold, the controller 5 outputs an equalization control signal, and the battery equalization module 4 supplements or releases the electric energy of the ith energy storage battery in response to the equalization control signal, so that the electric energy of the ith energy storage battery is equalized with the electric energy of other batteries in the battery pack 1, wherein i is greater than or equal to 1 and less than or equal to N. In a specific embodiment, the battery balancing module 4 charges the electric energy discharged from the ith energy storage battery into the whole battery pack, or charges the electric current discharged from the whole battery pack into the ith energy storage battery.
For the battery equalization module 4, two manners may be used to equalize the battery power in the battery pack, which is specifically as follows:
in an embodiment, please refer to fig. 4, which is a schematic diagram of a circuit structure of a battery equalization module 4 disclosed in the present embodiment, wherein a battery pack 1 obtained by connecting n energy storage batteries BAT1, BAT2 … … BAT in series is illustrated; the battery equalization module 4 includes: the N releasing units 41 are in one-to-one correspondence with the N energy storage batteries, and each releasing unit 41 is connected to the positive and negative electrodes of the corresponding energy storage battery. In the figure, S1 and S2 … … Sn are equalization control signals of the 1 st and 2 nd … … n release units.
In the present embodiment, when the positive-negative electrode voltage of the ith energy storage battery exceeds a preset threshold, the controller 5 outputs an equalization control signal Si (1. Ltoreq.i. Ltoreq.n) to the ith release unit 41; the i-th discharging unit 41 turns on the positive and negative electrodes of the i-th energy storage battery to discharge the electric energy of the i-th energy storage battery.
In an embodiment, referring to fig. 4, the release unit 41 includes: power resistor R d And a switching tube Q k Wherein the power resistor R d The energy output by the battery can be released in a heating mode, and the power resistor R d And a switching tube Q k The connection mode of (2) is as follows:
in one connection, please refer to fig. 4, the power resistor R d One end of the power resistor R is connected with the positive electrode of the corresponding energy storage battery d Is connected to the other end of the switch tube Q k Is switched on and off in the first pole of (A) k Is connected to the negative electrode of the corresponding energy storage cell.
In another connection (not shown), the power resistor R d One end of the power resistor R is connected with the cathode of the corresponding energy storage battery d Is connected to the other end of the switch tube Q k Is switched on and off in the first pole of (A) k Is connected to the positive electrode of the corresponding energy storage cell.
In this embodiment, please refer to fig. 4, switch tube Q k The control electrode of (2) responds to the equalization control signal to turn on the switching tube Q k So as to correspond to the first pole and the second pole ofThe energy storage battery passes through the power resistor R d Releasing the electric energy.
In this embodiment, when one of the energy storage cells is overcharged, the corresponding switching tube Q k Conduction to dissipate excess energy into power resistor R d Thereby balancing each energy storage cell being monitored. The advantage of this embodiment is low cost and low complexity.
In another embodiment, please refer to fig. 5, which illustrates a schematic circuit structure of a battery equalization module 4 disclosed in this embodiment, wherein a battery pack 1 obtained by connecting n energy storage batteries BAT1, BAT2 … … BAT in series is illustrated; the battery equalization module 4 includes: n equalization units 42 corresponding to N energy storage batteries one by one; a first switching unit G; the two input ends of each equalization unit 42 are connected to the positive and negative poles of the corresponding energy storage battery, and the two output ends of the equalization unit 42 are connected to the positive pole m+ and the negative pole M of the battery pack 1 (connected to the negative pole M "through the first switch unit G). In the figure, S1 and S2 … … Sn are equalization control signals of the 1 st and 2 nd … … n equalization units.
In this embodiment, when the average voltage of the positive and negative voltages of the ith energy storage battery relative to the voltages of the batteries in the battery pack exceeds a preset threshold, the controller 5 outputs an equalization control signal Si (i is greater than or equal to 1 and less than or equal to N) to the first switch unit G of the ith equalization unit 42; the i-th equalization unit 42 exchanges the electric energy of the i-th energy storage battery with the electric energy of the battery pack 1 in which the i-th energy storage battery is located through the input terminal.
In an embodiment, referring to fig. 5, the equalizing unit 42 includes: mutual inductance coil L and second switch element K, wherein: one end of a primary coil of the mutual inductance coil L is connected to the positive electrode of the corresponding energy storage battery, and the other end of the primary coil is connected to the negative electrode of the corresponding energy storage battery through a second switch unit K; one end of a secondary coil of the mutual inductance coil L is connected to the positive electrode of the battery pack 1 where the corresponding energy storage battery is located, and the other end of the secondary coil is connected to the negative electrode of the battery pack 1 where the corresponding energy storage battery is located through the first switch unit G.
In this embodiment, the second switch unit K and the switch G are turned on in response to the equalization control signal, so that the electric energy of the corresponding energy storage battery exchanges energy with the battery pack 1 where the corresponding energy storage battery is located through the primary coil and the secondary coil of the mutual inductance coil L.
As an example, referring to fig. 5, when, for example, the positive and negative voltages of the 2 nd energy storage battery exceed the average voltage of the battery cell to reach the threshold, the controller 5 outputs an equalization control signal to the 2 nd equalization unit 42, at this time, the second switching unit K in the 2 nd equalization unit 42 is turned on in response to the equalization control signal; then, the positive electrode and the negative electrode of the 2 nd energy storage battery form a passage through the primary coil of the mutual inductance coil L, the secondary coil outputs the electric energy coupled from the primary coil through the mutual inductance principle and transmits the electric energy to the positive electrode and the negative electrode (namely, marks M+ and M-) of the battery pack 1 through the output end M+ and M-, and therefore the electric energy of the 2 nd energy storage battery is transmitted to the battery pack 1 where the 2 nd energy storage battery is located. When the positive and negative voltages of the 2 nd energy storage battery are lower than the average voltage of the battery pack battery to reach a threshold value, the controller 5 outputs an equalization control signal to the 2 nd equalization unit 42, and at this time, the first switch unit G in the 2 nd equalization unit 42 is turned on in response to the equalization control signal; therefore, the positive electrode M+ and the negative electrode M-of the battery pack form a passage through the secondary coil of the mutual inductance coil L, and the primary coil outputs electric energy coupled from the secondary coil by the mutual inductance principle and transmits the electric energy to the positive electrode and the negative electrode of the 2 nd battery, so that the battery pack 1 where the energy storage battery is arranged is realized to transmit the electric energy to the 2 nd energy storage battery.
In this embodiment, the redistribution of excess energy among the different cells within the battery pack is achieved by the equalization unit 42. This allows energy recovery and less waste to occur. In this embodiment, the energy is not dissipated in the form of heat, but is reused to charge the remaining cells in the battery. The embodiment fully utilizes the capacity of each battery in the battery pack and improves the utilization rate of the battery pack.
In an alternative embodiment, referring to fig. 3, 4 and 5, the subsystem further comprises: and the battery voltage and temperature detection module 6 is used for detecting the battery voltage and the battery temperature of the battery pack, and the battery voltage and temperature detection module 6 is connected with the battery pack and the controller 5. The controller 5 limits the charge and discharge current of the battery pack according to the voltage and temperature of the energy storage battery. When the temperature of the energy storage battery of the battery pack 1 of the subsystem exceeds a certain threshold value, or the voltage of any battery of the battery pack 1 of the subsystem exceeds an upper limit threshold value or is lower than a lower limit threshold value, or the charge and discharge current of the battery pack 1 of the subsystem exceeds a limit value, the subsystem controller 5 outputs or makes a decision through the control system 300 to output a bypass control signal so that the subsystem bridge conversion module 2 responds to the bypass control signal to short the alternating current side connected with the power grid to isolate the power grid from the battery pack 1; or the subsystem controller 5 outputs a breaking signal, and the first switching MOS tube Q1 and the second switching MOS tube Q2 respectively respond to the breaking signal to break the first pole and the second pole so as to stop the electric energy transmission of the battery pack 1; when a subsystem is abnormally bypassed, the control system 300 of the energy storage system controls the remaining subsystems to remain operational if the number of remaining subsystems still meets the operational requirements of the energy storage system.
In one embodiment, when the temperature of the energy storage battery exceeds a temperature threshold, the controller 5 outputs a bypass signal, and the bridge converter module 2 shorts the ac side connected to the grid in response to the bypass signal to isolate the grid from the battery 1. Specifically, for a full bridge converter (see description below), MOS transistor Q23 and MOS transistor Q24 may be turned on, such that first end h1 and second end h2 communicate via MOS transistor Q23 and MOS transistor Q24, bypassing the subsystem; for a half-bridge converter, MOS transistor Q26 may be turned on, such that first and second ends h1 and h2 communicate via MOS transistor Q26, thereby bypassing the subsystem.
It should be noted that, since each phase circuit is formed by cascading subsystems, and each subsystem is configured with a battery pack, after bypassing one subsystem for the same circuit, other subsystems can still participate in the operation (charge and discharge) of the phase circuit in cascade. That is, by-passing a subsystem, the subsystem can be protected and isolated, so that the subsystem does not influence the continuous operation of the phase rectifying circuit, and the reliable and safe operation of the battery energy storage system is ensured.
In another embodiment, referring to fig. 3, 4 and 5, the subsystem further comprises: and the battery voltage and temperature detection module 6 is used for detecting the battery voltage and the battery temperature of the battery pack, and the battery voltage and temperature detection module 6 is connected with the battery pack and the controller 5.
In this embodiment, when the temperature of the energy storage battery exceeds the temperature threshold, the controller 5 outputs a shutdown signal, and the first switching MOS Q1 disconnects the first pole and the second pole in response to the shutdown signal, so as to stop transmitting dc power to the battery pack 1; alternatively, the first switching MOS transistor Q1 and the second switching MOS transistor Q2 are both turned off from the respective first pole and second pole in response to the off signal, so as to stop the transmission of the dc power to the battery pack 1.
In this embodiment, the charging of the subsystem may be stopped by disconnecting the first switching MOS transistor Q1 or disconnecting the first switching MOS transistor Q1 and the second switching MOS transistor Q2, so that the subsystem is protected in the same way; and, this subsystem can be isolated again, make this subsystem not influence the work of phasing circuit.
Referring to fig. 6, which is a schematic diagram of a power balance control between sub-controls disclosed in this embodiment, the control system 300 generates a charge-discharge current reference command of the sub-system battery pack 1 according to the average value of the voltage of the energy storage capacitor C1 in the sub-system in the active phase circuit; the control system 300 generates a correction value of a charge-discharge current instruction of each subsystem battery pack according to the deviation of the electric quantity of each subsystem battery pack 1 relative to the average electric quantity of each subsystem battery pack; and adding correction values of the charge-discharge current reference command and the charge-discharge current command corresponding to each subsystem to form a final charge-discharge current command of each subsystem. The method comprises the following steps:
The subsystem charge-discharge current instruction is divided into two parts:
part 1: the control system 300 generates a charge-discharge current reference instruction of the subsystem battery pack 1 according to the average value of the energy storage capacitor voltage of the bridge type converter module in the effective subsystem in the phase circuit, which is shown as a closed-loop control system shown by a black solid arrow line in the figure, wherein Uc (N) is the rated value of the energy storage capacitor voltage of the subsystem;
for n subsystem storage capacitor C1 actualThe average voltage, where Uc (i) is the energy storage capacitor C1 voltage of the i-th subsystem. />
And generating subsystem charge and discharge current instructions for the voltage deviation of the energy storage capacitor C1 through low-pass filtering and the first PI controller.
Part 2: the control system 300 generates a correction value of the charge-discharge current command of each subsystem battery pack according to the deviation of the electric quantity of each subsystem battery pack 1 relative to the average electric quantity of each subsystem battery pack, see a closed-loop control system shown by a broken arrow line in the figure, wherein,
and (3) forming a correction value of an ith subsystem charge-discharge current instruction through a second PI controller facing the ith subsystem, wherein the average value of the battery pack electric quantity of the n subsystems is SOCavg-SOC (i) is the battery pack electric quantity of the ith subsystem, and SOCavg-SOC (i) is the deviation of the battery pack electric quantity of the ith subsystem.
The subsystem charge-discharge current command of part 1 and the correction value of each subsystem charge-discharge current command of part 2 are added to form the final charge-discharge current command of each subsystem.
The control system 300 sends the final charge-discharge current command to the controllers 5 of the respective subsystems, and the controllers 5 of the respective subsystems control the magnitude of the charge or discharge current to the battery pack 1 by controlling the coupling module 3.
In this embodiment, the above two parts form a dual closed-loop control system to restrict the electric quantity of each battery pack from protruding, so that each battery pack reaches a full/empty state as simultaneously as possible, and the whole system cannot continue to charge/discharge due to early full/empty of the individual battery packs, specifically:
the voltage of the energy storage capacitor C1 of the subsystem is a standard value in general;
the total energy of the power grid entering the energy storage system is controlled to be consistent with the total energy of charging and discharging of all subsystem battery packs: if the two are inconsistent, redundant energy is reflected on the change of the voltage of the energy storage capacitor C1, the average voltage of the energy storage capacitor C1 of each subsystem is consistent with the standard value of the voltage of the energy storage capacitor C1 through the first PI controller, namely, the energy stored by the energy storage capacitor C1 of each subsystem is balanced, and the energy of a power grid entering each subsystem of the energy storage system and the energy of each subsystem flowing into each battery pack are balanced and consistent in total quantity;
The balance of the electric quantity among all subsystem battery packs is consistent: because of the inconsistency of the characteristics of the energy storage battery packs, the electric quantity of each subsystem may be inconsistent, and a second PI controller exists for each subsystem, so that the electric quantity of the battery pack of the corresponding subsystem is consistent with the average electric quantity of the battery packs of the subsystems in a tracking control mode by the second PI controller, and the electric quantity among the battery packs of the different subsystems is balanced and consistent.
In addition, the balance control efficiency can be improved by forming the double closed-loop control system by the two parts. For example, in the prior art, when the number of batteries connected in series is very large (for example, 100 batteries), each battery needs to be controlled separately, and the circuit design and control are difficult. The two parts are adopted to form a double closed-loop control system, and the total quantity of electric quantity between the power grid and the energy storage system can be controlled relatively easily by combining the selective input and the selective exit of each subsystem during the output of the multi-level topological voltage, so that the electric quantity between the battery packs is balanced without additional circuit design and loss, and the efficiency of balanced control can be improved. In the specific implementation process, some modules in the subsystem may be implemented by using an existing circuit structure, and for convenience of understanding by those skilled in the art, the present embodiment performs an unfolding description on some modules in the subsystem:
In one embodiment, the bridge converter module 2 is implemented by a full-bridge converter, and referring to fig. 3, the bridge converter module 2 includes a full-bridge converter and an energy storage capacitor C1. The full-bridge converter mainly comprises a plurality of MOS (metal oxide semiconductor) tubes (for example, Q21-Q24). One side of the full-bridge converter is the alternating current side of the bridge converter module 2, such as a first end h1 and a second end h2 shown in fig. 3, for accessing an alternating current power grid; the other side of the full bridge converter is the coupling side of the bridge converter module 2, as shown in fig. 3 at a third end h3 and a fourth end h4 for accessing the coupling module 3. Specifically, the second pole of the MOS transistor Q21 is connected to the first pole of the MOS transistor Q23 to form a first end h1, and the second pole of the MOS transistor Q22 is connected to the first pole of the MOS transistor Q24 to form a second end h2; the first pole of the MOS transistor Q21 is connected with the first pole of the MOS transistor Q22 to form a third end h3, and the second pole of the MOS transistor Q23 is connected with the second pole of the MOS transistor Q24 to form a fourth end h4. The control electrodes of the MOS transistors Q21, Q22, Q23 and Q24 are used for responding to respective control signals to turn on/off respective first electrodes and second electrodes.
In an alternative embodiment, the other side of the full bridge converter is connected to two ends of the energy storage capacitor C1, and the other side is a coupling side of the bridge converter module 2, such as a third end h3 and a fourth end h4 shown in fig. 3, and the coupling side is connected to the coupling module 3.
In another embodiment, the bridge converter module 2 is implemented by a half-bridge converter, please refer to fig. 7, which is a schematic diagram of another subsystem circuit structure of the energy storage system disclosed in this embodiment; the bridge converter module 2 comprises a half-bridge converter and an energy storage capacitor C1. As shown in fig. 7, the half-bridge converter mainly comprises 2 MOS transistors (Q25, Q26), and the two MOS transistors Q25, Q26 form a bridge arm; one side of the half-bridge converter is the ac side of the bridge converter module 2, such as a first end h1 and a second end h2 shown in fig. 7, for accessing an ac power grid; the other side of the half-bridge converter is the coupling side of the bridge converter module 2, as shown in fig. 4 at a third end h3 and a fourth end h4 for accessing the coupling module 3. Specifically, the second pole of the MOS transistor Q25 is connected with the first pole of the MOS transistor Q26 to form a first end h1, and the second pole of the MOS transistor Q26 forms a second end h2; two ends of the energy storage capacitor C1 are respectively connected with the first pole of the MOS transistor Q25 and the second pole of the MOS transistor Q26, and a third end h3 and a fourth end h4 are formed. In this embodiment, the MOS transistor Q25 is turned on, the MOS transistor Q26 is turned off, so that the energy storage capacitor C1 can be charged and discharged, and the entire subsystem can be bypassed when the MOS transistor Q25 is turned off and the MOS transistor Q26 is turned on.
In the implementation process, the bridge conversion module 2 can be realized by selecting a half-bridge converter or a full-bridge converter according to actual application scenes. When the full-bridge converter is selected to realize the bridge converter module 2, the topology structure of fig. 1 is preferentially selected; when a half-bridge converter is chosen to implement the bridge converter module 2, the topology of fig. 2 is preferred.
In this embodiment, the energy storage capacitor C1 is disposed in the bridge converter module 2, so as to improve the ripple of the input current of the power grid. Specifically, a full-bridge converter is taken as an example for explanation,
when the input current of the alternating current power grid is sinusoidal, and the first end h1 and the second end h2 of the bridge type current converting module 2 are input to be positive half waves of the sinusoidal current, the MOS transistors Q21 and Q24 are controlled to be conducted, the two ends of the capacitor C1 are charged at the moment, and when the first end h1 and the second end h2 of the bridge type current converting module 2 are input to be negative half waves of the sinusoidal current, the MOS transistors Q22 and Q23 are controlled to be conducted, and the two ends of the capacitor are in a charging state at the moment. In the charging process, the charging current of the energy storage capacitor C1 is a pulsating charging current; the voltage across the storage capacitor C1 is relatively stable due to the storage capacitor C1. When the battery pack 1 is charged under the control of the coupling module 3, the dc side of the bridge converter module 2 can provide a relatively stable dc voltage output for the energy storage unit to charge the battery pack 1.
In this embodiment, the energy storage capacitor C1 is used as a transfer station for energy conversion between the ac power grid and the battery pack 1, and can convert the pulsating current with larger ripple wave input by the power grid into the dc voltage with smaller ripple wave, so as to maintain the dc voltage output by the bridge converter module 2 in a relatively stable state, so as to reduce the dc ripple wave when the battery pack 1 is charged, and reduce the damage to the battery pack 1.
It should be noted that, because active and reactive exchange may exist between the battery pack and the ac power grid at the same time, the energy storage capacitor also has a transient process of discharging, but the ac power grid charges the energy storage capacitor macroscopically, that is, the energy storage capacitor stores electric energy.
Referring to fig. 3, a coupling module 3 is connected between the coupling side of the bridge converter module 2 and the battery pack 1, and the coupling module 3 is used for performing coupling matching on the bridge converter module 2 and the battery pack 1, where the coupling matching may be voltage matching or current matching. In addition, the coupling module 3 can also carry out ripple filtering on the direct current output by the bridge type converter module 2, and transmit the direct current energy after filtering to the battery pack 1; alternatively, the coupling module 3 is configured to transmit the electric energy output by the battery pack 1 to the bridge converter module 2, and transmit the electric energy to the power grid through the bridge converter module 2. In this embodiment, the voltage between the bridge converter module 2 and the battery pack 1 may be adapted by the coupling module 3, specifically, may be either boost or buck. In a specific embodiment, the coupling module 3 may be formed by a single DC-DC unit, by a plurality of DC-DC units connected in parallel, or by a combination of DC-DC units and LC filter circuits. Referring to fig. 3, in the present embodiment, a first end d1 and a second end d2 of the coupling module 3 form a first dc side of the coupling module 3, and are connected to a third end h3 and a fourth end h4 of the coupling side of the bridge converter module 2, and a second end d2 and a third end d3 of the coupling module 3 form a second dc side of the coupling module 3, and are connected to the positive and negative poles of the battery pack 1. In this embodiment, through the coupling module 3, voltage and current matching can be performed, and filtering effect can be achieved, so that ripple waves of charge and discharge flows can be reduced.
In the implementation process, the step-up or step-down function of the coupling module 3 may be implemented by a DC-DC unit. Preferably, the coupling module 3 may be configured as a buck DC-DC by a charge-discharge control unit (in particular, see circuit description of the charge-discharge control unit described below), for which the voltage on the second direct current side is lower than the voltage on the first direct current side, and thus may be suitable for use in smaller battery pack sizes, so that higher control accuracy and more diversified operation capabilities may be provided when used in an energy storage system.
In a specific embodiment, referring to fig. 3 and 7, the coupling module 3 includes a charge and discharge control unit, and the charge and discharge control unit includes: in this embodiment, 2 switching MOS transistors Q1, Q2 are connected in series to form a bridge arm of a half-bridge converter, where: the second pole of the first switching MOS tube Q1 is connected with the first pole of the second switching MOS tube Q2, and the connection point is connected with the first end of the first inductor L1; the second pole of the second switching MOS transistor Q2 is connected to the negative pole of the bridge converter module 2 and the negative pole of the battery pack 1. In this embodiment, a first pole of the first switching MOS transistor Q1 is connected to one of the positive pole terminal of the coupling side of the bridge converter module 2 and the positive pole terminal of the battery pack 1, and a second pole of the first inductor L1 is connected to the other of the positive pole terminal of the coupling side of the bridge converter module 2 and the positive pole terminal of the battery pack 1, specifically as follows:
In one embodiment, referring to fig. 3, a first pole (e.g., drain) of the first switching MOS transistor Q1 is connected to the positive terminal (h 3 terminal) of the bridge converter module 2, and meanwhile, the first pole (e.g., drain) of the first switching MOS transistor Q1 is led out as the first terminal d1 of the coupling module 3; the second pole (e.g. source) of the second switching MOS transistor Q2 is connected to the negative terminal of the bridge converter module 2 and the negative terminal (h 4 terminal) of the battery pack 1, and at the same time, the second pole (e.g. source) of the second switching MOS transistor Q2 is led out as the second terminal d2 of the coupling module 3; the second pole (e.g., source) of the first switching MOS transistor Q1 and the first pole (e.g., drain) of the second switching MOS transistor Q2 are connected, and the connection point is connected to a first end of the first inductor L1, and a second end of the first inductor L1 is connected to a positive end of the battery pack 1 via a coupling circuit or directly (see description below).
In a specific implementation process, when the bridge current conversion module 2 charges the battery pack 1, the control electrode of the first switching MOS transistor Q1 and the control electrode of the second switching MOS transistor Q2 are alternately turned on with respective first and second electrodes according to a preset switching frequency in response to a charging control signal, so as to transmit the electric energy output by the bridge current conversion module 2 to the battery pack 1 through a later coupling circuit. Specifically, the charging control signal of the first switching MOS transistor Q1 and the charging control signal of the second switching MOS transistor Q2 are inverted PWM signals: in one switching period, the second switching MOS transistor Q2 is turned off and the first switching MOS transistor Q1 is turned on; and then, after the first switching MOS tube Q1 is turned off, the second switching MOS tube Q2 is turned on, and the pulsating direct current (the ripple wave is eliminated by the first inductor L1) output by the coupling side of the bridge type current converting module 2 charges the battery pack 1.
When the battery pack 1 discharges to the bridge converter module 2, the control electrode of the first switching MOS transistor Q1 and the control electrode of the second switching MOS transistor Q2 are alternately conducted with the respective first electrode and second electrode in response to a discharge control signal, so as to transmit the electric energy released by the battery pack 1 to the bridge converter module 2. Specifically, the first aspect isThe discharge control signal of the MOS transistor Q1 and the discharge control signal of the second MOS transistor Q2 are inverted PWM signals: in a switching period, the second switching MOS tube Q2 is controlled to be conducted, the first switching MOS tube Q1 is controlled to be closed, at the moment, the current output by the battery pack 1 flows through the first inductor L1, and energy is stored in the first inductor L1; then, the second switching MOS transistor Q2 is controlled to be turned off, and then the first switching MOS transistor Q1 is turned on, and at this time, the first inductor L1 charges the energy storage capacitor C1 through the first switching MOS transistor Q1. In the next switching cycle, the above process is continued, and finally, the voltage across the storage capacitor C1 is maintained at a substantially stable value. It will be appreciated that when the energy storage unit 30 is used to supply power to the ac power grid, the output voltages of the ac side first and second terminals h1 and h2 of the bridge converter module 2 may be +u by controlling the switching tubes in the bridge converter Subsystem capacitance voltage 、-U Subsystem capacitance voltage Or 0.
In another embodiment, as an alternative embodiment of fig. 3, please refer to fig. 7, which is a schematic circuit diagram of an alternative circuit structure of the coupling module 3 disclosed in this embodiment, specifically, the position of the charge/discharge control unit in the coupling module 3 is exchanged with the position of the inductor L1. As shown in fig. 7, a first pole (e.g., drain) of the first switching MOS transistor Q1 is led out as a third terminal d3 of the coupling module 3, and is connected to the positive terminal of the battery pack 1; a second pole (e.g. source) of the second switching MOS transistor Q2 is led out as a second end d2 of the coupling module 3, and is connected to the negative terminal of the bridge converter module 2 and the negative terminal of the battery pack 1; the second pole (e.g., source) of the first switching MOS transistor Q1 is connected to the first pole (e.g., drain) of the second switching MOS transistor Q2, the connection point is connected to the first end of the first inductor L1, and the other end of the first inductor L1 is led out (or led out via a coupling circuit) as the first end d1 of the coupling module 3, and is connected to the positive electrode end h3 of the coupling side in the bridge converter module 2.
In this embodiment, the first end d1 and the second end d2 of the coupling module 3 are connected to the third end h3 and the fourth end h4 of the bridge converter module 2; the second end d2 and the third end d3 of the coupling module 3 are connected with the anode and the cathode of the battery pack 1.
With this arrangement, a step-up DC-DC unit (for the charging process) can be realized, so that charging of the battery pack 1 can be realized even if the voltage across the energy storage capacitor C1 is lower than the voltage across the battery pack in the energy storage unit 30.
It should be noted that, in the two embodiments of fig. 3 and fig. 7, the bridge converter module 2 and the coupling module 3 may be combined at will.
In this embodiment, the coupling circuit may be a combination of inductance and capacitance, and specifically includes the following steps:
in another embodiment, the coupling circuit is additionally connected with an LC circuit based on the inductance L1, please refer to fig. 3 and fig. 7, which are schematic circuit structures of another embodiment of the coupling module 3 disclosed in this embodiment, wherein fig. 3 is a circuit structure suitable for a buck type, and fig. 7 is a circuit structure suitable for a boost type. In a specific embodiment, the coupling module 3 further comprises: the capacitor C2 and the second inductor L2, wherein the capacitor C2 is connected between the second end of the first inductor L1 and the second pole of the second switching MOS tube Q2; the second inductor L2 is connected in series between the second end of the first inductor L1 and the positive end of the battery pack 1. Specifically:
referring to fig. 3, a first pole (e.g., drain) of the first switching MOS transistor Q1 is led out as a first end d1 of the coupling module 3; one end of the capacitor C2 is connected to a connection point between the second pole (e.g., source) of the first switching MOS transistor Q1 and the first pole (e.g., drain) of the second switching MOS transistor Q2, and the other end of the capacitor C2 is connected to the second pole (e.g., source) of the second switching MOS transistor Q2, and the connection point is led out as a second end d2 of the coupling module 3; one end of the first inductor L1 is connected to a connection point between a second pole (e.g., a source) of the first switching MOS transistor Q1 and a first pole (e.g., a drain) of the second switching MOS transistor Q2, the other end of the first inductor L1 is connected to one end of the second inductor L2, and the other end of the second inductor L2 is led out to serve as a third end d3 of the coupling module 3. The first and second ends d1 and d2 of the coupling module 3 are connected to both ends (h 3 and h 4) of the bridge converter module 2, and the second and third ends d2 and d3 of the coupling module 3 are connected to the positive and negative poles of the battery pack 1.
At this time, the inductors L1, L2 and the capacitor C2 form a pi-type filter circuit to further eliminate the ripple in the dc current during the charge and discharge of the battery pack 1, ensure that the current ripple is as small as possible, protect the battery pack 1, and prolong the life of the battery.
Referring to fig. 7, one end of a first inductor L1 is connected to a connection point between a second pole (e.g., a source) of the first switching MOS transistor Q1 and a first pole (e.g., a drain) of the second switching MOS transistor Q2, the other end of the first inductor L1 is connected to one end of a second inductor L2, and the other end of the second inductor L2 is led out as a first end d1 of the coupling module 3; one end of the capacitor C2 is connected to a connection point between the second pole (e.g., source) of the first switching MOS transistor Q1 and the first pole (e.g., drain) of the second switching MOS transistor Q2, and the other end of the capacitor C2 is connected to the second pole (e.g., source) of the second switching MOS transistor Q2, and the connection point is led out as a second end d2 of the coupling module 3; a first pole (e.g., drain) of the first switching MOS transistor Q1 is led out as a third terminal d3 of the coupling module 3. The first and second ends d1 and d2 of the coupling module 3 are connected to both ends (h 3 and h 4) of the bridge converter module 2, and the second and third ends d2 and d3 of the coupling module 3 are connected to the positive and negative poles of the battery pack 1.
At this time, the inductors L1, L2 and the capacitor C2 form a pi-type filter circuit to further eliminate the ripple in the dc current during the charge and discharge of the battery pack 1, ensure that the current ripple is as small as possible, protect the battery pack 1, and prolong the life of the battery.
In order to further eliminate the ripple in the dc current during the charge and discharge, in an alternative embodiment, a plurality of charge and discharge control units may be connected in parallel in the coupling module 3, please refer to fig. 8, which is a schematic circuit structure diagram of a third embodiment of the coupling module 3 disclosed in this embodiment, where the coupling module 3 includes: m charge and discharge control units connected in parallel, wherein M is more than or equal to 2, and the working phase of each charge and discharge control unit is different by 360 degrees/M in sequence; the first poles of the first switching MOS transistors Q1 are connected in parallel; the second poles of the second switching MOS transistors Q2 are connected in parallel; the second ends of the first inductors L1 are connected in parallel. Specifically, taking the step-down coupling module 3 as an example, the first poles of the first switching MOS transistors Q1 are connected in parallel to the positive pole end (h 3 end) of the bridge converter module 2; the second pole of each second switching MOS transistor Q2 is connected in parallel to the negative pole end of the bridge converter module 2 and the negative pole end (h 4 end) of the battery pack 1; each charge-discharge control unit is connected to the positive terminal of the battery pack 1 via a respective coupling circuit (an example of an inductance L1 in the drawing).
The parallel connection of the boost-type coupling module 3 is similar, and will not be described here again.
In a specific implementation process, the current phases on each charge and discharge control unit are sequentially different by 360 °/M, for example, please refer to fig. 9, which is a schematic diagram of a current superposition process of M charge and discharge control units disclosed in this embodiment, taking 4 charge and discharge control units as an example, the i+1th charge and discharge control unit current phase is delayed by 90 ° (i=1, 2, 3) than the i-th charge and discharge control unit current phase, that is, the 2, 3, 4-th charge and discharge control units are respectively delayed by 90 °, 180 °, 270 ° than the 1-th charge and discharge control unit current phase. In a specific implementation process, the phase difference may be achieved by controlling the switching timing (for example, the on timing of the first switching MOS transistor Q1) of each charge-discharge control unit.
In this embodiment, please refer to fig. 9, the difference in phase of the plurality of charge/discharge control units makes the dc current combined by the plurality of charge/discharge control units smaller than the dc current in the single branch. Meanwhile, the ripple wave can be reduced without increasing the switching frequency continuously due to the existence of the plurality of charge and discharge control units, so that the switching frequency in each charge and discharge control unit can be smaller, the switching loss is reduced to a certain extent, the overall loss of the energy storage system is reduced, and the energy conversion efficiency is improved.
In an alternative embodiment, the coupling circuits of the respective charge and discharge control units are at least partially multiplexed. Referring to fig. 10, a schematic circuit structure of a fourth embodiment of a coupling module 3 disclosed in this embodiment is shown, specifically, a plurality of charge-discharge control units are connected in parallel and are respectively configured with a first inductor L1 of the coupling circuit, meanwhile, each charge-discharge control unit multiplexes a second inductor L2 and a capacitor C2 of the coupling circuit together, and the multiplexed second inductor L2 and capacitor C2 can respectively form a pi-type filter circuit with the first inductor L1 configured independently by each charge-discharge control unit, so as to ensure that the current ripple at d3 is as small as possible, further eliminate the ripple in the direct current during charge-discharge in the battery pack 1, protect the battery pack 1, and prolong the service life of the battery.
The coupling module 3 may be any circuit that achieves the above object, and is not limited to the above circuit implementation.
According to the embodiment of the invention, the battery energy storage system comprises a control system and phase circuits, wherein each phase circuit comprises a subsystem which is sequentially cascaded, and the subsystem comprises: the battery pack is obtained by connecting N energy storage batteries in series and is used for storing electric energy output by a power grid; the bridge type converter module is used for converting alternating current electric energy into direct current electric energy to be stored in the battery pack, or converting electric energy output by the battery pack into alternating current and combining the alternating current electric energy with a power grid; the coupling module is used for coupling and matching the bridge type converter module and the battery pack, the battery balancing module is used for monitoring the working state of each energy storage battery and responding to the balancing control signal to balance and control the electric energy of each battery in the battery pack, and therefore the cascade structure of the battery energy storage system is realized.
And the controller is used for receiving the working state of each energy storage battery monitored by the battery balancing module and controlling at least one of the bridge type converter module, the coupling module and the battery balancing module, namely, for N energy storage batteries connected in series, N can be controlled in a range (such as within 10) easy to realize battery balancing control by the scheme, so that the electric quantity in each energy storage battery can be effectively controlled, and the charging process of stopping the whole battery pack caused by triggering protection such as overvoltage and undervoltage by a single battery is avoided. The battery energy storage module of the phasing circuit can store more electric energy, the capacity of the battery energy storage module is fully exerted, and the capacity waste is avoided. That is, the adverse effect of the weakest cell in the battery on the performance of the battery is reduced.
In addition, it should be noted that, since a plurality of subsystems are divided, the safety of the energy storage system can be improved, specifically, each subsystem can independently control bypass or input, and when a battery pack fault is detected, the subsystem can be bypassed; in addition, the traditional energy storage system cannot effectively realize active equalization, namely the number of batteries connected in series is too large, and an equalization circuit is too complex to realize.
For the equalization module, when the voltage of the anode and the cathode of the ith energy storage battery relative to the average voltage of the batteries in the battery pack exceeds a preset threshold value, the controller outputs an equalization control signal to a first switch unit of the ith equalization unit; and the ith equalization unit exchanges the electric energy of the ith energy storage battery with the electric energy of the battery pack where the ith energy storage battery is positioned through the input end. The balance unit realizes the redistribution of redundant energy among different batteries in the battery pack. This allows energy to be recovered and less wasted, the energy not being dissipated as heat but being re-used to charge the remaining cells in the battery. The capacity of each battery in the battery pack is fully utilized, and the utilization rate of the battery pack is improved.
Those skilled in the art will appreciate that the above-described preferred embodiments can be freely combined and stacked without conflict.
It will be understood that the above-described embodiments are merely illustrative and not restrictive, and that all obvious or equivalent modifications and substitutions to the details given above may be made by those skilled in the art without departing from the underlying principles of the invention, are intended to be included within the scope of the appended claims.
Claims (15)
1. A battery energy storage system comprising a single-phase or three-phase circuit, comprising a control system (300) and a phase circuit, each phase circuit comprising a plurality of subsystems in series, the subsystems comprising:
the battery pack (1) is obtained by connecting N energy storage batteries in series and is used for storing electric energy output by a power grid, wherein N is an integer greater than or equal to 2;
the bridge type converter module (2) is used for converting alternating current electric energy into direct current electric energy to be stored in the battery pack (1) or converting electric energy output by the battery pack (1) into alternating current electric energy to be combined with a power grid; the bridge type current conversion module (2) is provided with an alternating current side and a coupling side, wherein the alternating current side is used for connecting subsystems in series in a plurality of subsystems; the bridge type current conversion module (2) comprises an energy storage capacitor (C1) which is connected to two ends of the coupling side;
the coupling module (3) is connected between the coupling side of the bridge type current conversion module (2) and the battery pack (1) and is used for coupling and matching the bridge type current conversion module (2) and the battery pack (1);
the battery equalization module (4) is connected to the battery pack (1), and the battery equalization module (4) is used for monitoring the working state of each energy storage battery and is also used for equalizing the electric quantity of each battery in the battery pack (1) in response to an equalization control signal;
The controller (5) is connected with the control ends of the bridge type converter module (2), the coupling module (3) and the battery balancing module (4) and can receive the working state of each energy storage battery monitored by the battery balancing module (4) and control at least two of the bridge type converter module (2), the coupling module (3) and the battery balancing module (4);
the control system (300) respectively performs data interaction with the controllers (5) in each subsystem, and the controllers (5) in each subsystem control the bridge converter modules (2), the coupling modules (3) and/or the battery equalization modules (4) in each subsystem according to the control command of the control system (300) so as to control the working states of each subsystem, wherein:
the control system (300) is responsible for charge and discharge control and balance control among all subsystems, and the controller (5) of each subsystem is responsible for balance control in the subsystem of the controller, wherein:
the control system (300) generates a charge-discharge current reference instruction of the subsystem battery pack (1) according to the average value of the voltage of the energy storage capacitor (C1) in the bridge type converter module in the subsystem which is effective in the phase circuit;
the control system (300) adjusts charge and discharge current instructions of the battery packs of the subsystems according to the quantity of the electric quantity of the battery packs (1) of the subsystems, and controls balance of the electric quantity of the battery packs (1) of the subsystems; the electric quantity of the subsystem battery pack is higher, and in a charging state, the charging current instruction is reduced, and in a discharging state, the discharging current instruction is increased; the electric quantity of the subsystem battery pack is lower and is in a charging state, a charging current instruction is increased, and in a discharging state, a discharging current instruction is reduced;
The control system (300) sends charge and discharge current instructions of the battery pack (1) to the controllers (5) of all the subsystems, and the controllers (5) of all the subsystems control the charge or discharge current of the battery pack (1) through the control coupling module (3);
and a controller (5) of the subsystem controls an equalization module (4) of the subsystem to realize equalization of the electric quantity of each battery in the subsystem battery pack (1) according to the electric quantity of each battery in the subsystem battery pack.
2. The battery energy storage system according to claim 1, wherein the battery equalization module (4) comprises: n equalization units (42) are in one-to-one correspondence with the N energy storage batteries; a first switching unit (G); the two input ends of each equalization unit (42) are connected with the positive electrode and the negative electrode of the corresponding energy storage battery, and the two output ends of each equalization unit (42) are connected with the positive electrode and the negative electrode of the battery pack (1);
when the voltage of the anode and the cathode of the ith energy storage battery exceeds a preset threshold value, the controller (5) outputs an equalization control signal to a first switch unit (G) of the ith equalization unit (42); the ith equalization unit (42) exchanges the electric energy of the ith energy storage battery with the electric energy of the battery pack (1) where the ith energy storage battery is located through an input end, wherein i is more than or equal to 1 and less than or equal to N.
3. The battery energy storage system according to claim 2, wherein the equalization unit (42) comprises: a mutual inductance coil (L) and a second switching unit (K);
one end of a primary coil of the mutual inductance coil (L) is connected to the positive electrode of the corresponding energy storage battery, and the other end of the primary coil is connected to the negative electrode of the corresponding energy storage battery through the second switch unit (K); one end of a secondary coil of the mutual inductance coil (L) is connected to the positive electrode of the battery pack (1) where the corresponding energy storage battery is located, and the other end of the secondary coil is connected to the negative electrode of the battery pack (1) where the corresponding energy storage battery is located through a first switch unit (G);
the second switch unit (K) and the first switch unit (G) are conducted in response to the balance control signal, so that the electric energy of the corresponding energy storage battery exchanges energy with the battery pack (1) where the corresponding energy storage battery is located through the primary coil and the secondary coil of the mutual inductance coil (L).
4. The battery energy storage system of claim 1, wherein the subsystem further comprises:
the battery voltage and temperature detection module (6) is used for detecting the battery voltage and the battery temperature of the battery pack, the battery voltage and temperature detection module (6) is connected with the battery pack and the controller (5), and the controller (5) limits the charge and discharge current of the battery pack according to the voltage and the temperature of the energy storage battery.
5. The battery energy storage system of any of claims 1-4, wherein,
the control system (300) determines the voltages required by a plurality of moments in a power frequency period according to the voltage, active and reactive requirements of an alternating current power grid, and determines the target number of subsystems required to be put into at each moment based on the voltages required by the moment and the voltage values which can be output by the subsystems;
the control system (300) selects a target number of subsystems to enter a put-in state according to whether the subsystems needing to put into operation are in a charge or discharge state, and other subsystems enter a bypass state; when the subsystem is in a charging state, the control system (300) preferentially selects a lower subsystem of the voltage value of the energy storage capacitor in the bridge type converter module (2) to enter an input state; when the subsystem is in a discharging state, the subsystem with a higher voltage value of the energy storage capacitor in the bridge type converter module (2) is preferentially selected to enter an input state.
6. The battery energy storage system of any of claims 1-4, wherein,
the control system (300) generates a charge-discharge current reference instruction of the subsystem battery pack (1) according to the average value of the voltage of the energy storage capacitor (C1) in the subsystem which is effective in the phase circuit;
The control system (300) generates correction values of charge and discharge current instructions of the subsystem battery packs according to deviation of the electric quantity of the subsystem battery packs (1) relative to the average electric quantity of the subsystem battery packs;
and adding correction values of the charge-discharge current reference command and the charge-discharge current command corresponding to each subsystem to form a final charge-discharge current command of each subsystem.
7. Battery energy storage system according to any of claims 1-4, characterized in that the coupling module (3) comprises: a charge-discharge control unit;
the charge and discharge control unit includes: the first switching MOS tube (Q1), the second switching MOS tube (Q2) and the first inductor (L1);
the second pole of the first switching MOS tube (Q1) is connected with the first pole of the second switching MOS tube (Q2), and the connection point is connected with the first end of the first inductor (L1);
the second pole of the second switching MOS tube (Q2) is connected to the negative pole end of the bridge type current transformation module (2) and the negative pole end of the battery pack (1);
a first electrode of the first switching MOS tube (Q1) is connected to one of a positive electrode end of a coupling side in the bridge type current converting module (2) and a positive electrode end of the battery pack (1), and a second end of the first inductor (L1) is connected to the other of the positive electrode end of the coupling side in the bridge type current converting module (2) and the positive electrode end of the battery pack (1);
When the bridge type current transformation module (2) charges the battery pack (1), the control electrode of the first switching MOS tube (Q1) and the control electrode of the second switching MOS tube (Q2) are used for responding to a charging control signal to alternately conduct the respective first electrode and second electrode so as to transmit the electric energy output by the bridge type current transformation module (2) to the battery pack (1);
when the battery pack (1) discharges to the bridge type current conversion module (2), the control electrode of the first switching MOS tube (Q1) and the control electrode of the second switching MOS tube (Q2) are alternately conducted with the respective first electrode and the second electrode in response to a discharge control signal, so that electric energy released by the battery pack (1) is transmitted to the bridge type current conversion module (2).
8. The battery energy storage system of claim 7, wherein,
when the temperature of the energy storage battery of the battery pack (1) of the subsystem exceeds a certain threshold value, or the voltage of any battery of the battery pack (1) of the subsystem exceeds an upper limit threshold value or is lower than a lower limit threshold value, or the charge and discharge current of the battery pack (1) of the subsystem exceeds a limit value, the subsystem controller (5) outputs or makes a decision through the control system (300) to output a bypass control signal so that the subsystem bridge converter module (2) responds to the bypass control signal to short the alternating current side connected with the power grid to isolate the power grid from the battery pack (1); or the subsystem controller (5) outputs a breaking signal, and the first switching MOS tube (Q1) and the second switching MOS tube (Q2) are respectively used for responding to the breaking signal to disconnect the respective first pole and second pole so as to stop the electric energy transmission of the battery pack (1); when a subsystem is abnormally bypassed, a control system (300) of the energy storage system controls the remaining subsystems to keep running if the number of the remaining subsystems still meets the running requirement of the energy storage system.
9. The battery energy storage system according to claim 7, wherein the coupling module (3) comprises: m charge and discharge control units connected in parallel, wherein M is more than or equal to 2, and the working phase of each charge and discharge control unit is different by 360 degrees/M in sequence;
the first poles of the first switching MOS transistors (Q1) are connected in parallel;
the second poles of the second switching MOS transistors (Q2) are connected in parallel;
the second ends of the first inductors (L1) are connected in parallel.
10. The battery energy storage system of claim 7, wherein,
a first pole of the first switching MOS tube (Q1) is connected to a positive pole end of a coupling side in the bridge type converter module (2);
the second end of the first inductor (L1) is connected to the positive end of the battery pack (1).
11. The battery energy storage system according to claim 10, wherein the coupling module (3) further comprises:
the capacitor (C2) is connected between the second end of the first inductor (L1) and the second pole of the second switching MOS tube (Q2);
and a second inductor (L2) connected in series between the second end of the first inductor (L1) and the positive electrode end of the battery pack (1).
12. The battery energy storage system of claim 7, wherein,
a first electrode of the first switching MOS tube (Q1) is connected to the positive electrode end of the battery pack (1);
The second end of the first inductor (L1) is connected to the positive end of the coupling side in the bridge type current transformation module (2).
13. The battery energy storage system according to claim 12, wherein the coupling module (3) further comprises:
the capacitor (C2) is connected between the second end of the first inductor (L1) and the second pole of the second switching MOS tube (Q2);
the second inductor (L2) is connected in series between the second end of the first inductor (L1) and the positive electrode end of the coupling side in the bridge type current transformation module (2).
14. The battery energy storage system of any of claims 1-4, wherein the battery energy storage system is a single-phase or three-phase circuit energy storage system;
the bridge type current conversion module (2) is realized by a full-bridge current converter;
each phase circuit comprises a bridge arm which is sequentially cascaded with a plurality of subsystems, wherein two alternating current access ends (h 1, h 2) of each subsystem on the alternating current side are respectively connected with two alternating current access ends (h 1, h 2) of the adjacent subsystem on the alternating current side in series; a first end (h 1) of the first subsystem is connected with a phase access point of an alternating current power grid, and at least one inductor (200) is connected in series between the subsystems and/or between the first end (h 1) of the first subsystem and the access point of the alternating current power grid; the second end (h 2) of the last subsystem is connected to a neutral access point of the ac network.
15. The battery energy storage system of any of claims 1-4, wherein the battery energy storage system is a three-phase circuit energy storage system, the battery energy storage system further comprising a dc grid connection;
the bridge type current conversion module (2) is realized by a half-bridge current converter or a full-bridge current converter;
each phase circuit comprises an upper bridge arm and a lower bridge arm, the number of subsystems of the cascade connection of the upper bridge arm and the lower bridge arm is the same, wherein:
in the upper bridge arm, two alternating current access ends (h 1, h 2) of the alternating current side of each subsystem are respectively connected in series with two alternating current access ends (h 1, h 2) of the alternating current side of the adjacent subsystem; connecting a first phase access point of an alternating current power grid from the alternating current power grid to a direct current power grid positive end (DC+), wherein at least one inductor (200) is connected in series between a plurality of subsystems in an upper bridge arm and/or between the second end (h 2) of the first subsystem and the access point of the alternating current power grid; the first end (h 1) of the last subsystem is connected with the positive end (DC+) -of the direct current power grid;
in the lower bridge arm, two alternating current access ends (h 1, h 2) of the alternating current side of each subsystem are respectively connected in series with two alternating current access ends (h 1, h 2) of the alternating current side of the adjacent subsystem; from the alternating current power grid to the negative end (DC-), the first end (h 1) of the first subsystem is connected with a phase access point of the alternating current power grid, and at least one inductor (200) is connected in series between a plurality of subsystems in the lower bridge arm and/or between the first end (h 1) of the first subsystem and the access point of the alternating current power grid; the second end (h 2) of the last subsystem is connected to the negative end (DC-) of the direct current network.
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| CN202210983389.0A CN115313457B (en) | 2022-08-16 | 2022-08-16 | Battery energy storage system |
| PCT/CN2022/119307 WO2024036685A1 (en) | 2022-08-16 | 2022-09-16 | Battery energy storage system |
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| CN118381096B (en) * | 2024-06-26 | 2024-09-20 | 西安奇点能源股份有限公司 | Modeling method and device for cascade multi-level energy storage system and storage medium |
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| CN104901381A (en) * | 2015-06-16 | 2015-09-09 | 北京亿利智慧能源科技有限公司 | Equalizing current control method for H-bridge cascaded energy-storing system |
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