CN206559058U - A kind of grid-connected Large Copacity energy-accumulating power station of synchronized motor - Google Patents

Abstract

The utility model provides a large-capacity energy storage power station connected to the grid through a synchronous motor, which learns from the synchronous motor in the power system, which has a large capacity and is naturally friendly to the grid; the energy storage power station is composed of ≥ 1 power station unit , the power station unit is composed of an energy storage system, PCS, a first motor, a coupling, and a second motor. The first motor and the second motor can operate as a motor or a generator and form an electrical The second motor is a synchronous motor and is connected to the medium-voltage and high-voltage grid; the PCS can quickly adjust the operating state of the first motor, and the second motor can adjust its own excitation system to send or absorb active power and reactive power to the AC grid. Realize two-way flow of energy and four-quadrant operation, participate in power system frequency regulation, peak regulation, and voltage regulation, and serve as a black start power supply for the power system, suitable for the construction of 100-megawatt-level battery energy storage power stations.

Description

A large-capacity energy storage power station connected to the grid through a synchronous motor

technical field

The utility model relates to the field of an energy storage power station using a battery pack and a supercapacitor as an energy storage device, in particular to a large-capacity energy storage similar to a pumped storage power station using a battery pack and a supercapacitor as an energy storage device The power station is connected to the grid with synchronous motors to assist the grid in peak regulation, frequency regulation, voltage regulation, and black start.

Background technique

my country has built a number of 10-million-kilowatt-level new energy power generation bases. With the rapid development of the Energy Internet, large-scale energy storage technology has become a key supporting technology for the utilization of new energy generation with randomness, gaps, and volatility. For the access of large-scale new energy power generation, on the one hand, reduce its randomness and improve its adjustability through the combination of energy storage technology and new energy power generation; adaptability.

Pumped storage is currently the most mature and cost-effective energy storage method in the power system, but it is limited by geographical location. The configuration of battery energy storage is flexible and is not restricted by geographical location. With the continuous improvement of battery cycle life and cost performance, energy storage power stations using batteries as energy storage devices have received attention and demonstration applications.

In power grids in areas where new energy power generation is enriched, the capacity requirements for battery energy storage are usually more than tens of MW, or even more than 100 MW. The national wind power storage and transmission demonstration project is currently the world's largest renewable energy project integrating wind power, photovoltaic power generation, energy storage and power transmission projects. The development scale is 500 megawatts of wind power, 100 megawatts of solar photovoltaic power generation, 110 megawatts Watts for chemical energy storage.

At present, battery energy storage is mainly connected to the grid by power electronic converters. With the large-scale development and utilization of new energy, a large number of power electronic converters are connected to the grid, the trend of power electronics in the power system is becoming more and more obvious, the operating characteristics of the power grid have undergone major changes, and the security and stability of the power system have become increasingly prominent. In some areas where new energy is concentrated and connected to the grid, sub-/super-synchronous oscillations often occur, which is different from the low-frequency oscillation mode dominated by synchronous machines, and it is difficult to analyze and suppress it.

Drawing on the natural and friendly grid-connected characteristics of synchronous motors, the virtual synchronous machine technology of power electronic converters has been highly valued. The virtual synchronous machine technology introduces the rotor motion and electromechanical transient equations of the synchronous machine into the control link of the power electronic converter, and configures the energy storage unit or uses the inertia of the wind turbine to simulate the primary frequency modulation and excitation control mechanism of the synchronous generator to realize automatic adjustment. Active power and reactive power, adaptively participate in system frequency and voltage regulation, and damp system frequency oscillation, so as to achieve the purpose of improving the safe and stable operation level of the regional power grid. Numerous scientific research institutions and enterprises have carried out a lot of research and demonstration applications on it, and have made certain progress.

However, the application of virtual synchronous machines also encounters inherent limitations. The adaptability of large-scale access to the power grid is still unclear, and it also faces the problems of associated coupling and mutual excitation under complex power electronic environment conditions; when a short-circuit fault occurs in the power grid, the traditional synchronous motor can It supports a large short-circuit current, while the virtual synchronous machine cannot support a large short-circuit current due to the limitation of the overcurrent characteristics of power electronic devices; limited by the overload capacity, the voltage control ability is not as good as that of the conventional synchronous motor set.

Contents of the invention

In view of the defects of the existing technology, and the trend of large-scale and high-proportion new energy grid connection in the energy transformation that has been vigorously developed in the world, the utility model provides a large-capacity energy storage power station scheme connected to the grid through synchronous motors And implementation examples, referring to the large capacity and natural grid-connected characteristics of synchronous motors in the power system, replacing the defects caused by a large number of grid-connected traditional power converters, similar to the function of pumped storage power plants but more flexible It can provide services such as peak regulation, frequency regulation, voltage regulation, black start, etc. for the power grid that accepts large-scale new energy power generation, improve the power grid's ability to accept energy storage power stations and new energy power generation, and improve the power system. safety.

The energy storage power station is composed of ≥ 1 power station unit. The power station unit is composed of an energy storage system, a PCS, a first motor, a coupling, and a second motor. The energy storage system is connected to the PCS, and the PCS is connected to the first motor. A motor and a second motor are connected through a coupling to form a motor unit, and the second motor is a synchronous motor and is connected to a medium-voltage and high-voltage grid for operation.

After the second motor is connected to the grid, it can send or absorb reactive power by adjusting its own excitation system to control the reactive power between it and the grid; at the same time, the speeds of the second motor and the first motor are basically unchanged by the constraints of the grid, and the PCS controls the first motor The running state of the first motor makes the first motor work in the motor state or the generator state; when the first motor works in the motor state, the PCS absorbs DC power from the energy storage system to drive the first motor, and the first motor drives the second motor through the coupling Grid-connected power generation, transmission of active power to the grid; when the first motor is working as a generator, the second motor operates as a motor, absorbing active power from the grid, driving the first motor to generate electricity, and the PCS converts the AC power generated by the first motor into The direct current charges the energy storage system.

The power station unit responds to the AGC (automatic generation control) and AVC (automatic voltage control) commands of the grid in real time or independently adjusts the operating state of the first motor and the self-excitation system of the second motor according to the voltage and frequency of the grid-connected point, and sends active power to the AC grid Or absorb active power and reactive power, realize two-way flow of energy and four-quadrant operation, participate in frequency modulation, peak regulation, and voltage regulation of the power system, and serve as a black start power supply for the power system.

Both the first motor and the second motor are three-phase AC motors, which can be operated as motors or generators; the first motor is one of permanent magnet synchronous motors, synchronous motors, and asynchronous motors, and the second motor is synchronous motor.

Due to the two-way transmission of energy by the motor set, the first motor and the second motor have the same rated power and rated speed, and their rated speed is the synchronous speed of the 50Hz or 60Hz alternating current generated by the second motor.

Because the first motor and the second motor transmit power through the coupling, they have the function of electrical isolation, so the rated voltages of the first motor and the second motor are independent of each other; the second motor can be connected to the grid through medium voltage and high voltage, which can improve the system efficiency. Conversion efficiency, reducing loss and cost of equipment such as step-up transformers, the rated voltage of the second motor includes 3.15kV, 6.3kV, 10.5kV, 13.8kV, 15.75kV, 18kV and 20kV.

The energy storage system of the energy storage power station is composed of ≥2 energy storage units, one energy storage unit includes an energy storage device and a bidirectional DC/DC converter, and the energy storage device includes battery packs of different chemical systems (such as lithium battery pack, lead-acid battery pack, lead-carbon battery pack, flow battery pack) and high power density supercapacitor module, the positive and negative poles of the energy storage device are respectively connected to the input positive and negative poles of the bidirectional DC/DC converter, bidirectional The positive pole and the negative pole of the output of the DC/DC converter are the positive pole and the negative pole of the energy storage unit.

There are two types of bidirectional DC/DC converters: isolated and non-isolated, and the insulation level of the isolated bidirectional DC/DC converter is the same as that of the connected first motor, so that the energy storage device is insulated from the first motor .

PCS has two topologies: modular multilevel converter (MMC) and cascaded H-bridge converter (CHC). PCSs with different topologies correspond to different energy storage unit access methods.

The PCS based on MMC topology has three phases and 6 bridge arms. The upper and lower bridge arms form a phase. The lead wires at the connection points of the upper and lower bridge arms are connected to the first motor phase. ) and a current-limiting reactance.

The PCS based on the MMC topology has a medium-voltage and high-voltage DC bus. Since the output voltage of a single energy storage unit is low, it cannot be directly connected to the DC bus. Therefore, several energy storage units are connected in series and in parallel to form a large-capacity energy storage system. Connect to this DC bus; the output port of the bidirectional DC/DC converter is used as the interface between the energy storage device and the PCS, and is controlled as a voltage source with analog internal resistance, and its output voltage is related to its output current and analog internal resistance, specifically the output voltage = When the output current of the energy storage unit is zero, the output voltage minus the analog internal resistance multiplied by the discharge current or the voltage obtained by adding the analog internal resistance multiplied by the charging current.

Based on the cascaded H-bridge topology PCS, it has three phases, the three phases are connected in a star shape, each phase is connected to one phase of the first motor, and each phase is composed of N H-bridge converters in series, and each H-bridge The converter is connected to an energy storage unit.

The grid connection mode of the power station unit of the energy storage power station is related to the topology structure, economy and reliability of the PCS. There are two input grid connection modes.

The first one is started from the side of the energy storage system: the energy storage system provides energy for the PCS, and drives the first motor to operate with variable frequency and speed regulation through the PCS, thereby adjusting the frequency and phase of the output voltage of the second motor; and adjusting the self-excitation of the second motor The system controls the output voltage of the second motor, and connects to the grid after the output voltage of the second motor meets the synchronization condition with the grid voltage.

The second type starts from the grid side: the second motor is equipped with an auxiliary starting device, which assists the second motor to start and enter the grid as a motor, and drives the first motor to run to the synchronous speed. It is suitable for the occasion where the PCS based on the MMC topology is inconvenient to start the first motor with frequency conversion .

Compared with the prior art, the utility model has the following beneficial effects.

The energy storage power station is connected to the grid through synchronous generators, which has inertia to the grid and can stabilize the frequency of the grid; replaces the grid connection of the power electronic converter, improves the power quality, and solves the adaptability of the large-scale grid connection of the power electronic converter to the grid. Theoretical analysis of effective and effective subsynchronous oscillations in power systems and solutions to subsynchronous/supersynchronous oscillations caused by large-scale power electronic converters connected to the grid; when a short-circuit fault occurs in the power grid, a large short-circuit current is provided, which is conducive to the restoration of the power grid ; In areas where new energy is concentrated and connected to the grid, the grid is often a weak grid, and its short-circuit current is small. The short-circuit current of the weak grid can be increased by synchronous motor grid connection, which is conducive to the stability of the power system and UHV DC transmission.

Description of drawings

Other characteristics, objects and advantages of the present invention will become more apparent by reading the detailed description of the non-limiting implementation examples with reference to the following drawings.

Fig. 1 is a structural diagram of a power station unit of a large-capacity energy storage power station connected to the grid through synchronous motors proposed by the utility model.

Fig. 2 is a schematic diagram of a PCS based on an MMC (modular multilevel) topology disclosed by the implementation example of the present invention.

Fig. 3 is a schematic diagram of an energy storage system disclosed in an implementation example of the present invention connected to a PCS based on an MMC (modular multi-level) topology.

Fig. 4 is a schematic diagram of a PCS with an energy storage system connected to a cascaded H-bridge (CHC) topology disclosed in the implementation example of the present invention.

detailed description

The utility model will be described in detail below in conjunction with specific implementation examples. The following implementation examples will help those skilled in the art to further understand the utility model, but do not limit the utility model in any form. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present utility model. These all belong to the protection domain of the present utility model.

Referring to Fig. 1, the utility model discloses a power station unit of a large-capacity energy storage power station connected to the grid through a synchronous motor. The power station unit consists of an energy storage system, a power conversion system (PCS), a first motor, a coupling, and a second motor. The energy storage system is connected to the PCS, and the PCS is connected to the first motor. The first motor and the second motor are connected through a joint The shaft is connected to form a motor group, and the second motor is a synchronous motor and is integrated into the medium-voltage and high-voltage power grid for operation.

After the second motor is connected to the grid, the reactive power between the second motor and the grid is controlled by adjusting its own excitation system, and reactive power is generated or absorbed; at the same time, the speed of the second motor and the first motor are basically unchanged by the constraints of the grid, and the PCS controls the first motor. In the running state, the first motor works in the motor state or the generator state; when the first motor works in the motor state, the PCS absorbs DC power from the energy storage system to drive the first motor, and the first motor drives the second motor through the coupling and The grid generates power and transmits active power to the grid; when the first motor is working as a generator, the second motor operates as a motor, absorbing active power from the grid to drive the first motor to generate electricity, and the PCS converts the AC power generated by the first motor into DC Charge the energy storage system.

The power station unit responds to the AGC (automatic generation control) and AVC (automatic voltage control) commands of the grid in real time or independently adjusts the operating state of the first motor and the self-excitation system of the second motor according to the voltage and frequency of the grid-connected point, and sends or absorbs power to the AC grid. Active power and reactive power realize two-way flow of energy and four-quadrant operation, participate in frequency regulation, peak regulation, and voltage regulation of the power system, and serve as a black start power supply for the power system.

Both the first motor and the second motor are three-phase AC motors, which can be operated as motors or generators; the first motor is one of permanent magnet synchronous motors, synchronous motors, and asynchronous motors, and the second motor is synchronous motor.

Due to the two-way transmission of energy by the motor set, the first motor and the second motor have the same rated power and rated speed, and their rated speed is the synchronous speed of the 50Hz or 60Hz alternating current generated by the second motor.

The first motor and the second motor transmit power through the coupling, which has the function of electrical isolation. Therefore, the rated voltages of the first motor and the second motor are independent of each other; in order to improve the conversion efficiency, the second motor is connected to the grid through medium voltage and high voltage. A step-up transformer can be saved. Preferably, the rated voltage of the second motor includes 3.15kV, 6.3kV, 10.5kV, 13.8kV, 15.75kV, 18kV and 20kV.

Referring to Fig. 2, the schematic diagram of the PCS based on the MMC (modular multi-level) topology disclosed by the utility model implementation example, the PCS has three phases and 6 bridge arms, and the upper and lower bridge arms form a phase, and the connection point of the upper and lower bridge arms is Lead wires are connected to one phase of the first motor, and each bridge arm is composed of N sub-modules (SM) and a current-limiting reactance.

Referring to FIG. 3 , it is a schematic diagram of the energy storage system disclosed in the implementation example of the present invention connected to the PCS based on the MMC (modular multi-level) topology.

The energy storage system consists of ≥2 energy storage units, one energy storage unit includes an energy storage device and a bidirectional DC/DC converter, and the energy storage device includes battery packs of different chemical systems (such as lithium battery packs, lead acid battery pack, lead-carbon battery pack, flow battery pack), and high power density supercapacitor module, the positive pole and negative pole of the energy storage device are respectively connected to the input positive pole and negative pole of the bidirectional DC/DC converter, and the bidirectional DC/DC The positive pole and the negative pole of the output of the converter are the positive pole and the negative pole of the energy storage unit.

There are two types of bidirectional DC/DC converters: isolated and non-isolated, and the insulation level of the isolated bidirectional DC/DC converter is the same as that of the connected first motor, so that the energy storage device is insulated from the first motor .

Since the PCS based on the MMC topology has a medium-voltage and high-voltage DC bus, the output voltage of a single energy storage unit is low and cannot be directly connected to the DC bus. Therefore, several energy storage units are connected in series and parallel to form a large-capacity energy storage system. Connect to this DC bus; the output port of the bidirectional DC/DC converter is used as the interface between the energy storage device and the PCS, and is controlled as a voltage source with analog internal resistance, and its output voltage is related to its output current and analog internal resistance, specifically the output voltage = When the output current of the energy storage unit is zero, the output voltage minus the analog internal resistance multiplied by the discharge current or the voltage obtained by adding the analog internal resistance multiplied by the charging current. The external characteristics of the battery are simulated in the above way to facilitate the series and parallel connection of the energy storage units, similar to how the batteries are connected in series and parallel to form a battery pack with a higher voltage level and higher capacity.

The power station unit has two input and grid connection methods: the first one starts from the side of the energy storage system, the energy storage system provides energy for the PCS, and the PCS drives the first motor to operate with variable frequency and speed regulation to adjust the frequency and output voltage of the second motor. Phase, and adjust the self-excitation system of the second motor to control the output voltage of the second motor, and connect to the grid after the output voltage of the second motor and the grid voltage meet the synchronization conditions;

The second type starts from the grid side, the second motor is equipped with an auxiliary starting device, and the auxiliary second motor is used as a motor to start and put into the grid, driving the first motor to run to the synchronous speed. It is suitable for the occasion where the PCS based on the MMC topology is inconvenient to start the first motor with frequency conversion .

Referring to FIG. 4 , it is a PCS schematic diagram of an energy storage system connected to a cascaded H-bridge (CHC) topology disclosed in the implementation example of the present invention.

The energy storage system is composed of ≥ 2 modular energy storage units, one energy storage unit includes an energy storage device and a bidirectional DC/DC converter, and the energy storage device includes battery packs of different chemical systems (such as lithium battery pack, lead-acid battery pack, lead-carbon battery pack, flow battery pack), and high power density supercapacitor module, the positive and negative poles of the energy storage device are respectively connected to the input positive and negative poles of the bidirectional DC/DC converter, The positive pole and the negative pole of the output of the bidirectional DC/DC converter are the positive pole and the negative pole of the energy storage unit.

There are two types of bidirectional DC/DC converters: isolated and non-isolated, and the insulation level of the isolated bidirectional DC/DC converter is the same as that of the connected first motor, so that the energy storage device is insulated from the first motor .

Based on the cascaded H-bridge topology PCS, it has three phases, the three phases are connected in a star shape, each phase is connected to one phase of the first motor, and each phase is composed of N H-bridge converters in series, and each H-bridge The converter is connected to an energy storage unit.

The power station unit has two input and grid connection methods: the first one starts from the side of the energy storage system, the energy storage system provides energy for the PCS, and the PCS drives the first motor to operate with variable frequency and speed regulation to adjust the frequency and output voltage of the second motor. Phase, and adjust the second motor's own excitation system to control the output voltage of the second motor, and connect to the grid after the output voltage of the second motor and the grid voltage meet the synchronization conditions; the second type starts from the grid side, and the second motor is equipped with an auxiliary starting device , assisting the second motor as a motor to start and put into the power grid, driving the first motor to run to a synchronous speed.

Claims (4)

1. a kind of grid-connected Large Copacity energy-accumulating power station of synchronized motor, it is characterised in that including：

The energy-accumulating power station is made up of >=1 power station unit, and power station unit is by energy-storage system, PCS（Energy conversion system）, first Motor, shaft coupling, the second motor composition, energy-storage system access PCS, PCS access the first motor, and the first motor and the second motor are logical Cross shaft coupling to couple to form group of motors, the second motor is synchronous motor and is incorporated to middle pressure, high-voltage fence operation；

It is idle between the control of itself excitation system and power network by adjusting after second motor is grid-connected, send or absorb idle work( Rate；The rotating speed of the second motor is by power constraint simultaneously, and PCS controls the running status of the first motor, the first motor is worked in electricity Motivational state or Generator Status；When first motor works in electric motor state, PCS absorbs direct current energy driving from energy-storage system First motor, the first motor drives the second motor to generate electricity by way of merging two or more grid systems by shaft coupling, and active power is conveyed to power network；First motor work When making in Generator Status, the second motor absorbs active power as motor running from power network, drives the first electric power generation, The AC energy that first motor is sent is converted into direct current energy and charged to energy-storage system by PCS；

Power station unit responsive electricity grid AGC in real time（Automatic Generation Control）、AVC（Automatism voltage control）Instruct or according to grid entry point Voltage, frequency from the running status of the motor of main regulation first and itself excitation system of the second motor, sent to AC network or Active power, reactive power are absorbed, two-way flow and the four quadrant running of energy is realized, power system frequency modulation, peak regulation, tune is participated in Pressure, and it is used as the black starting-up power supply of power system.

2. a kind of grid-connected Large Copacity energy-accumulating power station of synchronized motor according to claim 1, it is characterized in that：

First motor, the second motor are all three phase alternating current motors, can not only be transported as motor running but also as generator OK；First motor is one kind in permagnetic synchronous motor, synchronous motor, asynchronous machine, and the second motor is synchronous motor；

First motor and the second motor have identical rated power and rated speed, and its rated speed is that the second motor is sent The synchronous rotational speed of 50Hz or 60Hz alternating currents；

First motor and the second motor transmit power by shaft coupling, with electrical isolation effect；First motor and the second motor Rated voltage it is separate；Second motor is grid-connected by middle pressure, high pressure, and the rated voltage of the second motor includes 3.15kV, 6.3kV, 10.5kV, 13.8kV, 15.75kV, 18kV and 20kV.

3. a kind of grid-connected Large Copacity energy-accumulating power station of synchronized motor according to claim 1, it is characterized in that：

Energy-storage system is made up of >=2 energy-storage units, and 1 energy-storage units includes 1 energy storage device and 1 two-way DC/DC conversion Device, energy storage device includes battery pack, super capacitor, and positive pole, the negative pole of energy storage device connect the defeated of two-way DC/DC converters respectively Enter positive pole, negative pole, the output cathode of two-way DC/DC converters, positive pole, the negative pole that negative pole is energy-storage units；

Two-way DC/DC converters have isolated and non-isolated 2 kinds, wherein insulation of isolation type bidirectional DC/DC converters etc. The class of insulation of first motor of the level with being accessed is identical so that energy storage device and the first motor insulate；

The PCS has MMC（Modular multilevel）And cascaded H-bridges（CHC）2 kinds of topological structures, PCS pairs of different topology structure Answer different energy-storage units access ways：

Based on the PCS of MMC topologys, with 6 bridge arms of three-phase, two bridge arms are constituted up and down draws at a phase, upper and lower bridge arm tie point Go out the phase that wire accesses the first motor, each bridge arm is by N number of submodule（SM）With current-limiting reactor composition；

PCS based on MMC topologys has middle pressure, high voltage dc bus, and several energy-storage units are constituted by way of series and parallel This dc bus is accessed after Large Copacity energy-storage system；The output port of two-way DC/DC converters connects as energy storage device and PCS's Mouthful, control as with the voltage source for simulating internal resistance, its output voltage is relevant with its output current, simulation internal resistance, specially exports Output voltage subtracts simulation internal resistance and is multiplied by the voltage or add that discharge current draws when voltage=energy-storage units output current is zero The voltage that charging current is drawn is multiplied by simulation internal resistance；

Based on cascaded H-bridges topology PCS, with three-phase, three-phase is connected into star, and each phase accesses a phase of the first motor, Mei Yixiang It is in series by N number of H bridges current transformer, each H bridges current transformer accesses 1 energy-storage units.

4. a kind of grid-connected Large Copacity energy-accumulating power station of synchronized motor according to claim 1, it is characterised in that：

Power station unit have 2 kinds input synchronizing modes；

The first starts from energy-storage system side：Energy-storage system provides direct current energy for PCS, and PCS drives the first motor variable-frequency speed-regulating The frequency and phase of runing adjustment the second motor output voltage；And adjust itself excitation system the second motor of control of the second motor Output voltage, put into after the second motor output voltage and line voltage meet same period condition grid-connected；

Second from grid side start：Second motor configures auxiliary actuating apparatus, and the second motor of auxiliary is thrown as motor start-up Enter power network.