CN115986897B - Battery string charge and discharge management device and battery energy storage system - Google Patents

Abstract

The invention discloses a battery string charge and discharge management device and a battery energy storage system. The battery string charge and discharge management device is applied to a battery energy storage system. The battery string charge and discharge management device includes several groups of battery energy storage sub-modules, each The battery energy storage sub-modules each include several battery energy storage units connected in series, several first electric control switches, and several second electric control switches. During use, the battery management module controls the closing and opening of the first electric control switch and the second electric control switch according to the battery voltage and battery current detected by the battery detection module, thereby selecting the corresponding battery energy storage sub-module and battery The energy storage system is connected, and the charging and discharging of the battery energy storage sub-module is regulated, which can make the charging and discharging process more balanced, avoid overcharging or over-discharging of the battery cell, and thus improve the overall performance of the entire battery energy storage sub-module. service life, and ensure the voltage stability of the battery energy storage sub-module.

Description

A battery string charge and discharge management device and battery energy storage system

technical field

The invention relates to the technical field of power electronics, in particular to a battery string charging and discharging management device and a battery energy storage system.

Background technique

In recent years, with the establishment of my country's dual carbon targets and the rapid development of new energy equipment, intermittent and fluctuating power generation methods (photovoltaic power generation, wind power generation, etc.) in the power system have become influential factors that cannot be ignored in the current system. , and its scale will become larger and larger in the near future. Such a development trend also makes the task of peak-shaving and valley-filling in the power system more difficult, and electric energy storage is one of the effective means to solve this problem.

Battery energy storage is currently the most widely used high-energy-density energy storage method, and the existing battery energy storage system needs to use multiple battery cells connected in series and parallel to form a battery pack because most of the rated voltage of the battery is 3.2V. Then multiple battery packs are connected in series to form a battery cluster that meets the DC bus voltage; generally, in order to increase the capacity of energy storage, multiple battery clusters need to be connected in parallel to form a complete battery energy storage system. Then, according to the output requirements of the subsequent circuit, configure the DC/DC converter to cooperate with the photovoltaic power generation system or configure the DC/AC converter to directly connect to the grid.

Recently, some researchers have proposed a relatively novel improved structure that uses a modular multi-level structure to achieve precise control of the battery pack, called a modular multi-level battery energy storage system, but its precise control of the battery is still limited. At the pack level, finer control over the battery is not possible.

Contents of the invention

In view of the above problems, embodiments of the present invention are proposed to provide a battery string charging and discharging management device and a battery energy storage system that overcome the above problems or at least partially solve the above problems.

The embodiment of the present invention discloses a battery string charge and discharge management device. The battery string charge and discharge management device is applied to a battery energy storage system. The battery string charge and discharge management device includes:

Several groups of battery energy storage sub-modules, each group of battery energy storage sub-modules includes several battery energy storage units and a plurality of first electronically controlled switches, each of the battery energy storage units includes battery strings and The second electronically controlled switch connected in series to the battery strings, several of the battery energy storage units are connected in parallel to the several first electronically controlled switches, and each battery string is provided with several batteries;

A battery detection module, configured to detect the battery voltage and battery current of each battery string;

A battery management module, the battery management module is electrically connected to the battery string, the first electric control switch, the second electric control switch and the battery detection module, and is used to detect control the closing and opening of the first electric control switch and the second electric control switch, thereby selecting the corresponding battery energy storage sub-module to communicate with the battery energy storage system, And control the charging and discharging of the battery energy storage sub-module.

Optionally, the battery string is connected to the bus bar of the battery energy storage system through the second electric control switch,

When all the second electronically controlled switches in the battery energy storage submodule are turned off, and all the first electronically controlled switches in the battery energy storage submodule are closed, the battery energy storage submodule All battery strings in the module are bypassed from the battery energy storage system.

Optionally, the battery string is connected to the busbar of the battery energy storage system through the second electric control switch, the second electric control switch is provided with a diode, and the diode has a current blocking function during the discharge process,

When the battery strings in the battery energy storage sub-module are discharging, the battery detection module performs voltage sampling on the battery strings, and the battery management module selects from the n battery strings according to the voltage sorting by numerical value, select m battery strings with higher voltage sorting, and control the second electric control switch of the m battery strings to be closed, and the m battery strings are discharged, wherein, m<n, and m and n is a positive integer, and the specific number of m is determined according to the discharge current of the bus; after determining the corresponding m battery strings, the first PWM duty cycle is adjusted according to the detected voltage value, and the voltage value is consistent with the first PWM duty cycle The duty cycle is positively correlated to equalize the discharge current among the m battery strings, wherein the first PWM duty cycle is related to the PWM parameter of the second electronically controlled switch.

Optionally, the battery string is connected to the bus bar of the battery energy storage system through the second electric control switch, and the second electric control switch is provided with a diode,

When the battery strings in the battery energy storage sub-module are charging, the diodes have no blocking function for the current during the charging process, and the battery strings are all in the charging state, and the battery detection module performs a check on the battery strings Voltage sampling, the battery management module adjusts the second PWM duty cycle according to the detected battery voltage, and the voltage value is negatively correlated with the second PWM duty cycle, so as to balance the charging current between the battery strings, wherein the The second PWM duty ratio is related to the PWM parameter of the second electronically controlled switch.

Optionally, the battery string charge and discharge management device is further provided with several resistance devices, and the resistance devices are connected in parallel with the second electric control switch.

Optionally, the battery string charge and discharge management device is further provided with several capacitive devices, and the capacitive devices are connected in parallel with the second electric control switch.

Optionally, the battery energy storage system is provided with the above-mentioned battery string charge and discharge management device, which is applied to the grid connection of the battery energy storage system through a DC/AC converter. The battery energy storage system also includes a bus bar, a DC / AC converter, three-phase isolation transformer, and the third electric control switch, several sets of sub-module clusters are respectively connected in series with the third electric control switch, and each set of sub-module clusters includes several electrically connected said Battery energy storage sub-module;

When the battery energy storage system receives a grid connection instruction, the battery management system selects multiple groups of sub-module clusters to connect to the battery energy storage system, and controls the third electronically controlled switch connected to the sub-module clusters to close;

Wherein, after determining the corresponding sub-module cluster, the battery management system selects q battery energy storage sub-modules suitable for connecting to the battery energy storage system from a group of p battery energy storage sub-modules in the sub-module cluster , where, q=floor(U _{DC bus} /U _{energy storage sub-module} ), q<p, and both p and q are positive integers, U _{DC bus} is the voltage between the positive and negative poles of the DC bus, U _{energy storage sub-module} is the preset voltage of the battery energy storage sub-module;

After determining q submodules connected in series in the system in a group of submodule clusters, the battery management system samples the DC bus voltage, and controls at least one redundant battery energy storage submodule of the group of submodule clusters according to the voltage sampling results The first electric control switch and the second electric control switch are closed or disconnected, so as to select the corresponding battery energy storage sub-module to communicate with the battery energy storage system, and store energy for the battery The charging and discharging of the sub-modules are regulated.

Optionally, the battery energy storage system is provided with the above-mentioned battery string charge and discharge management device, which is applied to the grid connection of the battery energy storage system. The battery energy storage system includes a DC positive bus, a DC negative bus, and The inductance between the DC positive bus and the DC negative bus, and six sub-module clusters, each group of sub-module clusters includes several electrically connected battery energy storage sub-modules;

Wherein, one end of the three sub-module clusters is connected to the DC positive bus, and the other end of the three sub-module clusters is connected in series with the first end of the inductor, and three phases A, B, and C are drawn out as The three upper bridge arms of the inverter; one end of the three sub-module clusters is connected to the DC negative bus, the other end of the three sub-module clusters is connected in series with the second end of the inductor, and leads to A , B, and C three-phase, as the three lower bridge arms of the inverter; the inductor is used for filtering and power conversion.

By adopting the above technical solution, the technical solution of the present invention has the following beneficial effects:

(1) By detecting the battery voltage and battery current of the battery string, the battery string charge and discharge management device can finely control the charging and discharging of the battery string monomers, making the charging and discharging process more balanced and avoiding the occurrence of battery single Overcharge or overdischarge of the body, thereby improving the overall service life of the entire battery energy storage sub-module, and ensuring the voltage stability of the battery energy storage sub-module;

(2) Multiple battery energy storage modules are connected in parallel through switches to facilitate the management of the battery management module. Select a suitable battery energy storage module and incorporate it into the system to avoid battery overheating caused by internal circulation in the battery energy storage.

Description of drawings

FIG. 1 is a structural diagram of a conventional battery energy storage system in the prior art;

Fig. 2 is a schematic structural diagram of a multi-level half-bridge energy storage sub-module provided by an embodiment of the present invention;

Fig. 3 is a schematic structural diagram of a battery energy storage system provided by an embodiment of the present invention;

Fig. 4 is a schematic diagram of the structure of a battery energy storage module provided by an embodiment of the present invention;

5 is a schematic diagram of a battery string charge and discharge management device provided by an embodiment of the present invention;

Fig. 6 is a schematic diagram of a battery energy storage system provided by an embodiment of the present invention;

Fig. 7 is a schematic diagram of another battery energy storage system provided by an embodiment of the present invention;

Fig. 8 is a schematic diagram of a battery energy storage sub-module provided by an embodiment of the present invention;

Fig. 9 is a schematic diagram of another battery energy storage sub-module provided by an embodiment of the present invention.

Detailed ways

In order to make the above objects, features and advantages of the present invention more comprehensible, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

The embodiments of the present invention are made based on the inventors of the present application's discovery and recognition of the following facts and problems. In related technologies, battery energy storage is currently the most practically used high-energy-density energy storage method, and the existing battery energy storage system requires the use of multiple battery cells connected in series and parallel because the rated voltage of the battery cells is mostly 3.2V. It is a battery pack, and then multiple battery packs are connected in series to form a battery cluster that meets the DC bus voltage; generally, in order to increase the capacity of energy storage, multiple battery clusters need to be connected in parallel to form a complete battery energy storage system. Then, according to the output requirements of the subsequent circuit, configure the DC/DC converter to cooperate with the photovoltaic power generation system or configure the DC/AC converter to directly connect to the grid.

Fig. 1 is a structural diagram of a conventional battery energy storage system in the prior art, which is applied in a scenario where a DC/AC converter is configured for grid connection. This battery energy storage system consists of a DC positive bus 101 , a DC negative bus 102 , a DC-AC converter 103 , a three-phase isolation transformer 104 , a battery cluster 105 , a battery pack 106 , and a third electric control switch 107 . The basic principle of its structure is that a plurality of battery packs 106 are connected in series to form a battery cluster 105, and the battery cluster 105 is connected in series with the third electric control switch 107, and then connected in parallel to form the entire battery energy storage system. The application in FIG. 1 is a scenario where the DC positive bus 101 and the DC negative bus 102 are connected to a DC/AC converter 103, and then a three-phase isolation transformer 104 is connected to the grid. If the DC positive bus 101 and the DC negative bus 102 are externally connected to a DC/DC converter 130, it is a scenario where a conventional battery energy storage system is combined with photovoltaic power generation.

The disadvantages of this battery energy storage system are mainly manifested in: 1. Only the third electric control switch 107 can be used to control whether the entire battery cluster is connected to the system, and it is impossible to control the charging and discharging of the internal battery packs and battery cells. It is very easy to cause unbalanced charge and discharge control of internal battery packs and battery cells due to differences in consistency, resulting in overcharge or overdischarge, and eventually lead to attenuation of the capacity and life of the entire battery cluster 105; 2. Multiple battery clusters 105 are connected in parallel to form In the entire battery energy storage system, when multiple battery clusters 105 are connected to the DC positive bus 101 and the DC negative bus 102 at the same time, the voltage difference between the battery clusters may cause a circulating current inside the battery energy storage system. If the current is too large, the A fire may occur due to overheating of the battery; 3. The voltage between the DC positive bus 101 and the DC negative bus 102 is uncontrollable, and a DC/AC converter or a DC/DC converter must be used to achieve subsequent goals, which increases costs and loss.

In order to solve the problems caused by the above-mentioned conventional battery energy storage system in Fig. 1, Fig. 2 is a schematic structural diagram of a multi-level half-bridge energy storage sub-module provided by an embodiment of the present invention, and a modular multi-level half-bridge can be used The energy storage sub-module structure is used to realize the fine control of the battery pack inside the battery cluster. The basic structure of the sub-module is composed of a battery pack 206 , an upper power electronic switch 208 and a lower power electronic switch 209 . The basic working principle is: regardless of the direction of the current, the upper power electronic switch 208 is turned on, and the lower power electronic switch 209 is turned off to connect the battery pack 206 into the energy storage system; while the upper power electronic switch 208 is turned off, the lower power electronic switch Turning on the switch 209 can bypass the battery pack 206 from the energy storage system, so as to realize fine control of the battery packs inside the battery cluster. The fine-grained control of the battery pack can avoid the capacity and life decay of the battery cluster and the battery overheating.

Fig. 3 is a schematic structural diagram of a battery energy storage system provided by an embodiment of the present invention. The battery energy storage system applies the modular multi-level half-bridge energy storage sub-module shown in Fig. 2 to a DC battery energy storage system. It consists of a DC positive bus 301 , a DC negative bus 302 , a DC-AC converter 303 , a three-phase isolation transformer 304 , a third electric control switch 307 , and a cluster of submodules 310 . Its structure is that a plurality of energy storage sub-modules in Fig. 2 are connected in series to form a sub-module cluster 310, and then connected in series with the third electric control switch 307, and then multiple in parallel according to actual needs to form the entire battery energy storage system. The application in Figure 3 is a scenario where the DC positive bus 301 and the DC negative bus 302 are connected to the DC/AC converter 303, and then connected to the grid with a three-phase isolation transformer 304. This AC scenario is the same as the conventional battery energy storage system shown in Figure 1 Same, all need to configure DC/AC converter. However, if it is changed to a DC application scenario, the DC/DC converter 130 in FIG. 1 can be saved because the sub-module cluster 310 has a DC voltage regulation capability, thereby reducing the grid-connected cost of the battery energy storage system.

In the actual application process, the inventors found that the sub-module in Figure 3 still has shortcomings. In a high-power battery energy storage system, due to the high instantaneous power of the system, the charging and discharging current flowing through the battery pack 206 is also very large. In order to reduce system loss and improve reliability, Figure 4 is a schematic diagram of a battery energy storage sub-module structure provided by an embodiment of the present invention, and the modular multi-level half-bridge sub-module in Figure 2 can be adjusted to The sub-module shown in Figure 4 is composed of a plurality of upper power electronic switches 408 in parallel and a plurality of lower power electronic switches 409 in parallel to form a switch group to realize the switching function, which reduces losses and also provides redundant power electronic switches, thereby facilitating The battery pack in the sub-module is controlled.

In the actual application process, the inventor found that when the power electronic switch is connected in series with the battery string, the parallel connection method can control the battery grouping in the energy storage sub-module battery pack under the premise of the same capacity without increasing the cost. Good precise control of the connection between battery strings and busbars. 5 is a schematic diagram of a battery string charge and discharge management device provided by an embodiment of the present invention. The battery string charge and discharge management device is applied to a battery energy storage system. The battery string charge and discharge management device includes several groups of battery energy storage sub-modules, Battery detection module and battery management module.

Each battery energy storage sub-module includes several battery energy storage units 511 and several first electric control switches 509 , and each battery energy storage unit 511 includes battery strings 510 and second electric control switches 508 . Among them, several groups of battery strings 510 are connected in parallel with the second electronically controlled switches 508 in series, and then connected in parallel with several first electronically controlled switches 509 to form the above-mentioned battery energy storage sub-module, and each battery string is provided with several batteries; This connection method can control the battery strings in the energy storage sub-modules in groups without increasing the cost of the same capacity, and can better control the connection between the battery strings and the busbar precisely. The battery packs used in the prior art are generally packaged by connecting a plurality of battery cells in series and parallel. In the embodiment of the present invention, a battery string with the same voltage as the battery pack 406 is used. The battery string can be understood as disassembling the battery pack 406 in parallel It is a combination of several batteries with smaller packages. Under the premise of equivalent voltage and equivalent space, the battery string with smaller capacity can achieve more fine control, so that users can easily control the output of the battery energy storage sub-module shown in Figure 5. voltage is regulated.

During use, the battery detection module is used to detect the battery voltage and battery current of each battery string. The battery management module is electrically connected to the battery string, the first electric control switch 509, the second electric control switch 508 and the battery detection module, and is used to control the first electric control switch according to the battery voltage and battery current detected by the battery detection module 509 and the closing and opening of the second electric control switch 508, so as to select the corresponding battery string to communicate with the battery energy storage system, and regulate the charging and discharging of the battery string.

During use, the battery string is connected to the outside of the battery energy storage sub-module through the second electric control switch 508, when all the second electric control switches 508 in the battery energy storage sub-module are disconnected, and the battery energy storage sub-module When all the first electric control switches 509 are closed, all battery strings in the battery energy storage sub-module are bypassed from the battery energy storage system.

During use, the battery string is connected to the outside of the battery energy storage sub-module through the second electric control switch 508, and the second electric control switch 508 is provided with a diode, which has a current blocking function during the discharge process. When the battery energy storage sub-module When the battery strings in are discharging, the battery detection module samples the voltage of the battery strings, and the battery management module sorts the n battery strings according to the voltage value according to the detected battery voltage, and selects m battery strings with higher voltage rankings , and control the closing of the second electric control switch of the m battery strings, and the m battery strings are discharged, wherein, m<n, and both m and n are positive integers, and the specific number of m is determined according to the discharge current of the bus; m=Id/Ic, where Id is the discharge current demand of the sub-module cluster, and Ic is the rated discharge current of the battery string, which is related to the discharge rate of the battery.

After determining the corresponding m battery strings, adjust the first PWM duty cycle according to the detected voltage value, and the voltage value is positively correlated with the first PWM duty cycle, so as to balance the discharge current among the m battery strings. Exemplarily, when the current direction is from bottom to top to discharge the sub-modules, the results of voltage sampling are sorted, and the m battery strings with higher voltages are prioritized to turn on their second electronically controlled switches 508, so that the corresponding m battery strings The battery string is discharged, and the number of m is determined by the discharge current of the entire sub-module. Then it is necessary to balance the discharge current of m battery strings that have been connected in series to the system. The specific operation steps are to set a higher or even 1 PWM duty cycle for battery strings with higher voltage, and for battery strings with lower voltage, Set a lower PWM duty cycle, and use this principle to balance the discharge current of each battery string put into the system.

During use, when the battery strings in the battery energy storage sub-module are charging, the diodes have no function of blocking the current during the charging process, and the battery strings are all in the charging state, and the battery detection module is The battery string performs voltage sampling, the battery management module adjusts the second PWM duty cycle according to the detected battery voltage, and the voltage value is negatively correlated with the second PWM duty cycle, so as to balance the charging between the battery strings current. Exemplarily, when the current direction is from top to bottom to charge the battery, due to the existence of anti-parallel diodes in all the second electronically controlled switches 508, there is no blocking capability, but the current regulation of the battery string can still be realized through PWM regulation. The principle is that the conduction voltage drop of the channel of the second electronically controlled switch 508 is very low, while the anti-parallel diode has a voltage drop of 0.7-1V, the charging current of the battery string charged through the channel is greater than the charging current of the battery string charged through the anti-parallel diode , the difference between the two can realize battery string current regulation. Therefore, according to the state of each battery string in the parallel controllable battery energy storage module 511 and the magnitude of the external charging and discharging current, the battery string suitable for being connected in series to the energy storage system can be optimally selected to achieve fine control of the battery string. It should be noted that both the first PWM duty cycle and the second PWM duty cycle are related to the design parameters of the second electric control switch 508, and both the first electric control switch 509 and the second electric control switch 508 can use MOS tubes, Those skilled in the art can set the parameters of the first PWM duty cycle and the second PWM duty cycle according to the parameters of the MOS transistors, so as to meet the requirements in actual use.

The technical solution of the present invention has the following beneficial effects: (1) By detecting the battery voltage and battery current of the battery string, the battery string charging and discharging management device can finely control the charging and discharging of the battery string monomers, so that the charging The discharge process is more balanced, avoiding the overcharge or overdischarge of the battery cell, thereby improving the overall service life of the entire battery energy storage sub-module, and ensuring the voltage stability of the battery energy storage sub-module; (2) multiple battery energy storage The modules are connected in parallel through the switch to facilitate the management of the battery management module. Select the appropriate battery energy storage module and incorporate it into the system to avoid the battery overheating problem caused by the internal circulation of the battery energy storage.

Fig. 6 is a schematic diagram of a battery energy storage system provided by an embodiment of the present invention. The energy storage system is provided with several groups of battery energy storage sub-modules as shown in Fig. 5 above. The battery energy storage system includes a DC positive bus 601 , a DC negative bus 602 , a DC-AC converter 603 , a three-phase isolation transformer 604 , a submodule cluster 612 formed by connecting n energy storage submodules shown in FIG. 5 in series, and a third electronically controlled switch 607 . Its structure is that the sub-module clusters 612 are connected in series with the third electric control switch 607, and then connected in parallel to form the entire battery energy storage system. Each group of sub-module clusters 612 includes several electrically connected battery energy storage sub-modules. The application in Figure 6 is a scenario where the DC positive bus 601 and the DC negative bus 602 are connected to the DC/AC converter 603, and then connected to the grid with a three-phase isolation transformer 604. This scenario is the same as the conventional battery energy storage system shown in Figure 1. A DC/AC converter is required. However, unlike the battery energy storage system shown in Figure 1, if the battery energy storage system shown in Figure 6 cooperates with the photovoltaic power generation system, the DC/DC converter 130 in Figure 1 can be saved, because the energy storage The sub-module cluster 612 formed by connecting the modules in series has a DC voltage adjustment capability, and can adjust the DC voltage between the DC positive bus 601 and the DC negative bus 602 . Since the energy storage system cooperates with the photovoltaic power generation system, the DC/DC converter can be saved, thereby reducing the cost of grid connection.

In practical applications, in order to ensure the reliability and flexibility of the battery energy storage system, each submodule cluster 612 is provided with a small number of redundant energy storage submodules. When the battery energy storage system receives the grid connection instruction, the battery management system selects multiple groups of sub-module clusters 612 to connect to the battery energy storage system, and controls the third electronically controlled switch 607 connected to the sub-module clusters 612 to close; After corresponding sub-module clusters, the battery management system selects q battery energy storage sub-modules suitable for connecting to the battery energy storage system from a group of p battery energy storage sub-modules in a group of sub-module clusters 612, wherein, q=floor(U _{DC bus} /U _{energy storage sub-module} ), q<p, and both p and q are positive integers, U _{DC bus} is the voltage between the positive and negative poles of the DC bus, and U _{energy storage sub-module} is the preset value of the battery energy storage sub-module Voltage; after determining the q submodules connected in series in the system in a group of submodule clusters, the battery management system samples the DC bus voltage, and controls at least one redundant battery energy storage submodule of the group of submodule clusters according to the voltage sampling results The first electronically controlled switch and the second electronically controlled switch are closed or disconnected, so that the corresponding battery energy storage sub-module is selected to communicate with the battery energy storage system, and the charging and discharging of the battery energy storage sub-module are regulated. It should be noted that when the battery energy storage system is running, the q most suitable energy storage sub-modules in the sub-module cluster 612 can be selected according to the preset algorithm, and those skilled in the art can set the preset algorithm according to their own needs. , this application does not specifically limit it.

Fig. 7 is a schematic diagram of another battery energy storage system provided by the embodiment of the present invention. The battery energy storage system uses the principle of MMC to directly connect to the grid. This application is consistent with the scenario shown in Figure 6, and the battery energy storage system is connected to the grid. However, the topology in Figure 7 can save high-power DC/AC converters at the cost of relatively complex control ideas. It consists of a DC positive bus 701, a DC negative bus 702, and a sub-module cluster 712 formed by connecting n energy storage sub-modules in series. The specific connection method is shown in Figure 7. The battery energy storage system includes a DC positive bus, a DC negative bus, an inductor arranged between the DC positive bus and the DC negative bus, and six sub-module clusters 712, each group of sub-module clusters 712 Each includes a number of electrically connected battery energy storage sub-modules; among them, one end of the three sub-module clusters 712 is connected to the DC positive bus 701, and the other end of the three sub-module clusters 712 is connected in series with the first end of the inductor _L0 , and leads out A, B, and C three-phase, as the three upper bridge arms of the inverter; one end of the three sub-module clusters 712 is connected to the DC negative bus 702, and the other end of the three sub-module clusters 712 is connected in series with the second end of the inductor _L0 , and lead out A, B, C three phases, as the three lower bridge arms of the inverter; the inductance L ₀ is used for filtering and power conversion.

The integrated topology of energy storage and inverter uses the nearest neighbor control commonly used in MMC to simulate AC voltage. Taking phase A as an example, by controlling whether the energy storage batteries in the 2n sub-modules are connected in series to the sub-module clusters of the upper and lower bridge arms of phase A to make A The phase port forms a stepped sinusoidal waveform, and the B and C phases also use the same control principle; while the sub-module still uses the optimal fine-grained control idea in Figure 5. By adopting the battery energy storage system, a high-power DC/AC converter can be saved, and while the cost can be reduced, the space occupied by the battery energy storage system can also be reduced.

In some embodiments, FIG. 8 is a schematic diagram of a battery energy storage sub-module provided by an embodiment of the present invention. Compared with the battery energy storage sub-module in Fig. 5, by connecting a resistor device in parallel beside the second electric control switch of the battery energy storage sub-module, such as the resistor in Fig. 8, a step-down circuit can be provided when the battery is discharged. The basic working principle is: if the second electronically controlled switches 808 in all the controllable battery energy storage modules 811 are turned off, all the lower first electronically controlled switches 809 are turned on, regardless of the direction of the current, all the battery strings in the module can be transferred from the storage Bypass in the energy system. If all the first electronically controlled switches 809 are turned off, the working principle is related to the direction of the current: the current direction discharges the battery from bottom to top, then all the second electronically controlled switches 808 have the ability to block, and the step-down circuit formed by the resistors connected in parallel passes through The discharge current of the battery string in the channel discharge is greater than the discharge current of the battery string through the resistor, and the current of each controllable battery energy storage module 811 can be adjusted by PWM; the current direction is from top to bottom to charge the battery, because all the second electronically controlled switches 808 The existence of anti-parallel diodes does not have blocking capability, but the battery string current regulation can still be realized through PWM regulation. The voltage drop is about 0.7-1V, and the charging current of the battery string charged through the channel is greater than the charging current of the battery string charged through the anti-parallel diode, and the difference between the two can realize the regulation of the battery string current. Therefore, according to the state of each battery string in the parallel controllable battery energy storage module 811 and the magnitude of the external charging and discharging current, the battery string suitable for being connected in series to the energy storage system can be optimally selected, and the refined control of the battery string can be realized. Fine control of charging and discharging can make the charging and discharging process more balanced, avoid overcharging or overdischarging of battery cells, thereby improving the overall service life of the entire battery energy storage sub-module, and ensuring that the battery energy storage sub-module The voltage is stable.

In some embodiments, FIG. 9 is a schematic diagram of another battery energy storage sub-module provided by an embodiment of the present invention. Compared with the battery energy storage sub-module in Fig. 5 and Fig. 8, by connecting a capacitor component in parallel next to the second electric control switch of the battery energy storage sub-module, a step-down circuit can be provided when the battery is discharged. The basic working principle is: if the second electronically controlled switches 908 in all the controllable battery energy storage modules 911 are turned off, all the first electronically controlled switches 909 are turned on, regardless of the direction of the current, all the battery strings in the module can be switched from the energy storage Bypass in the system. If all the first electronically controlled switches 909 are turned off, the working principle is related to the direction of the current: the current direction discharges the battery from bottom to top, then all the second electronically controlled switches 908 have the ability to block, and the step-down circuit formed by the capacitors connected in parallel passes through The battery string discharge current of channel discharge is greater than the battery string discharge current passing through the capacitor, and the current of each controllable battery energy storage module 911 can be adjusted by PWM; the current direction is from top to bottom to charge the battery, because all the second electronically controlled switches 908 The existence of the anti-parallel diode does not have the blocking ability, but the current regulation of the battery string can still be realized through PWM regulation. The voltage drop is about 0.7-1V, and the charging current of the battery string charged through the channel is greater than the charging current of the battery string charged through the anti-parallel diode, and the difference between the two can realize the regulation of the battery string current. Therefore, according to the state of each battery string in the parallel controllable battery energy storage module 911 and the magnitude of the external charging and discharging current, the battery string suitable for being connected in series to the energy storage system can be optimally selected, and the refined control of the battery string can be realized. Fine control of charging and discharging can make the charging and discharging process more balanced, avoid overcharging or overdischarging of the battery cell, thereby improving the overall service life of the entire battery energy storage sub-module, and ensuring that the battery energy storage sub-module The voltage is stable.

Each embodiment in this specification is described in a progressive manner, each embodiment focuses on the difference from other embodiments, and the same and similar parts of each embodiment can be referred to each other.

Those skilled in the art should understand that the embodiments of the present invention may be provided as methods, apparatuses, or computer program products. Accordingly, embodiments of the invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, embodiments of the invention may take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein.

Having described preferred embodiments of embodiments of the present invention, additional changes and modifications to these embodiments can be made by those skilled in the art once the basic inventive concept is appreciated. Therefore, the appended claims are intended to be interpreted to cover the preferred embodiment and all changes and modifications which fall within the scope of the embodiments of the present invention.

Finally, it should also be noted that in this text, relational terms such as first and second etc. are only used to distinguish one entity or operation from another, and do not necessarily require or imply that these entities or operations, any such actual relationship or order exists. Furthermore, the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article, or terminal equipment comprising a set of elements includes not only those elements, but also includes elements not expressly listed. other elements identified, or also include elements inherent in such a process, method, article, or terminal equipment. Without further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article or terminal device comprising said element.

The embodiments provided by the present invention have been described in detail above. The principles and implementation methods of the present invention have been explained by using specific examples in this paper. There will be changes in the scope of application. To sum up, the contents of this specification should not be construed as limiting the present invention.

Claims (3)

1. A battery string charge and discharge management device, wherein the battery string charge and discharge management device is applied to a battery energy storage system, the battery string charge and discharge management device comprising:

each battery energy storage sub-module comprises a plurality of battery energy storage units and a plurality of first electric control switches, each battery energy storage unit comprises a battery string and a second electric control switch connected with the battery string in series, the plurality of battery energy storage units are connected with the plurality of first electric control switches in parallel after being connected in parallel, and each battery string is provided with a plurality of batteries;

a battery detection module for detecting a battery voltage and a battery current of each group of the battery strings;

the battery management module is respectively and electrically connected with the battery string, the first electric control switch, the second electric control switch and the battery detection module and is used for controlling the first electric control switch and the second electric control switch to be closed and opened according to the battery voltage and the battery current detected by the battery detection module, so that the corresponding battery energy storage sub-module is selected to be communicated with the battery energy storage system and the charging and discharging of the battery energy storage sub-module are regulated and controlled;

the battery string is connected with a bus of the battery energy storage system through the second electric control switch,

when all the second electric control switches in the battery energy storage sub-module are disconnected and all the first electric control switches in the battery energy storage sub-module are closed, all the battery strings in the battery energy storage sub-module are bypassed from the battery energy storage system;

the battery string is electrically connected with a bus of the battery energy storage system through the second electric control switch, the second electric control switch is provided with a diode which has a current blocking function in the discharging process,

when the battery strings in the battery energy storage sub-module are discharged, the battery detection module samples the voltages of the battery strings, the battery management module sorts the detected battery voltages according to the voltage values in the n battery strings, selects m battery strings with higher voltage sorting, controls a second electric control switch of the m battery strings to be closed, and discharges the m battery strings, wherein m is less than n, m and n are positive integers, and the specific number of m is determined according to the discharge current of a bus; after determining the corresponding m battery strings, adjusting a first PWM duty cycle according to the detected voltage value, wherein the voltage value is positively correlated with the first PWM duty cycle so as to balance the discharge current among the m battery strings, and the first PWM duty cycle is correlated with PWM parameters of the second electric control switch;

the battery string is connected with a bus of the battery energy storage system through the second electric control switch, the second electric control switch is provided with a diode,

when a battery string in the battery energy storage sub-module is charged, the diode has no blocking function on current in the charging process, the battery string is in a charging state, the battery detection module performs voltage sampling on the battery string, the battery management module adjusts a second PWM duty cycle according to the detected battery voltage, and the voltage value is inversely related to the second PWM duty cycle so as to balance charging current among the battery strings, wherein the second PWM duty cycle is related to PWM parameters of the second electric control switch;

the battery string charge and discharge management device is also provided with a plurality of resistor devices or capacitor components, and the resistor devices or capacitor components are connected with the second electric control switch in parallel.

2. The battery energy storage system is characterized in that the battery energy storage system is provided with the battery string charge and discharge management device according to claim 1, the battery energy storage system is applied to grid connection of the battery energy storage system through a direct current/alternating current converter, the battery energy storage system further comprises a bus, a direct current/alternating current converter, a three-phase isolation transformer and a third electric control switch, a plurality of groups of sub-module clusters are respectively connected with the third electric control switch in series, and each group of sub-module clusters comprises a plurality of battery energy storage sub-modules which are electrically connected;

when the battery energy storage system receives a grid-connected instruction, the battery management system selects a plurality of groups of sub-module clusters to be connected with the battery energy storage system, and controls a third electric control switch connected with the sub-module clusters to be closed;

wherein the battery management system, after determining the corresponding sub-module cluster, is selected from a group ofQ battery energy storage sub-modules suitable for being connected with the battery energy storage system are selected from p battery energy storage sub-modules of the sub-module cluster, wherein q=floor (U _{DC bus} /U _{Energy storage sub-module} )，q<p, p and q are positive integers, U _{DC bus} U is the voltage between the positive electrode and the negative electrode of the direct current bus _{Energy storage sub-module} The method comprises the steps of presetting voltage for a battery energy storage sub-module;

after q sub-modules of a system are serially connected into a group of sub-module clusters, the battery management system samples the voltage of the direct current bus and controls the first electric control switch and the second electric control switch in at least one redundant battery energy storage sub-module of the group of sub-module clusters to be closed or opened according to the voltage sampling result, so that the corresponding battery energy storage sub-module is selected to be communicated with the battery energy storage system, and the charging and discharging of the battery energy storage sub-module are regulated and controlled.

3. The battery energy storage system is characterized in that the battery energy storage system is provided with the battery string charge and discharge management device according to claim 1, and is applied to grid connection of the battery energy storage system, the battery energy storage system comprises a direct current positive bus, a direct current negative bus, an inductor arranged between the direct current positive bus and the direct current negative bus and six sub-module clusters, and each group of sub-module clusters comprises a plurality of battery energy storage sub-modules which are electrically connected;

one end of each sub-module cluster is connected with the direct current positive bus, the other end of each sub-module cluster is connected with the first end of the inductor in series, and A, B, C three phases are led out and used as three upper bridge arms of the inverter; one end of each sub-module cluster is connected with the direct current negative bus, the other end of each sub-module cluster is connected with the second end of the inductor in series, and A, B, C three phases are led out and used as three lower bridge arms of the inverter; the inductor is used for filtering and performing power conversion.

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