Control method and device of all-vanadium redox flow battery energy storage system

Abstract

The invention relates to a control method and device for an all-vanadium redox flow battery energy storage system, and belongs to the technical field of energy storage, and the method comprises the steps: constructing an efficiency model used for representing the corresponding relation among the discharge energy of an all-vanadium redox flow battery, the energy consumption of a circulating pump and the battery efficiency; determining the optimal efficiency based on the temperature of the electrolyte of the all-vanadium redox flow battery, the flow of an electric pile inlet and an efficiency model, and setting the temperature and the flow as the optimal temperature and the optimal flow corresponding to the optimal efficiency; determining an electrical angle of active power output and a voltage amplitude of reactive power output by using a VSG control method and a power instruction, and controlling the bidirectional converter to output an output voltage meeting a power grid demand based on the electrical angle and the voltage amplitude; and the all-vanadium redox flow battery is connected into a power grid through the bidirectional converter. According to the control method of the all-vanadium redox flow battery energy storage system, the stability of a new energy power grid is improved, and powerful support is provided for access of new energy and stable operation of the power grid.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage, and particularly to a control method and device for a vanadium redox flow battery energy storage system. Background Art

[0002] Driven by the "dual carbon" goal, the large-scale grid connection of volatile renewable energy sources such as wind power and photovoltaic power poses a severe challenge to the grid frequency stability. Due to its power-capacity decoupled design and high safety, the vanadium redox flow battery (VRFB) has become an ideal choice for grid-scale energy storage and is very suitable for grid-scale energy storage.

[0003] Although VRFB has entered the engineering demonstration stage, the technical bottlenecks in high-power application scenarios still need to be broken through: the traditional PQ control strategy is difficult to simulate the characteristics of synchronous generator inertia response, resulting in insufficient dynamic characteristics of VRFB for grid frequency regulation; the circulating current problem caused by parameter differences under multi-machine parallel operation conditions will exacerbate system losses; the uneven flow field of the stack, the increase in flow rate and pump loss lead to a decrease in the overall system efficiency as the power increases. The above problems seriously restrict the large-scale promotion of MW-level grid-side energy storage of VRFB.

[0004] With the improvement of the penetration rate of renewable energy, traditional energy storage systems are difficult to meet the stability requirements when new energy is connected to the grid due to slow dynamic response and insufficient inertia support. Summary of the Invention

[0005] In view of this, it is necessary to provide a control method and device for a vanadium redox flow battery energy storage system to achieve the purpose of improving the efficiency of the energy storage system and the stability of the new energy grid.

[0006] To achieve the above purpose, in a first aspect, the present invention provides a control method for a vanadium redox flow battery energy storage system, including: Constructing an efficiency model for characterizing the corresponding relationship among the discharge energy of the vanadium redox flow battery, the energy consumption of the circulation pump, and the battery efficiency; Based on the temperature of the electrolyte of the vanadium redox flow battery, the flow rate at the stack inlet, and the efficiency model, determining the optimal efficiency, and setting the temperature and the flow rate as the optimal temperature and the optimal flow rate corresponding to the optimal efficiency; Using the VSG control method and the power command to determine the electrical angle of the active power output and the voltage amplitude of the reactive power output, and controlling the bidirectional converter to output an output voltage that meets the grid demand based on the electrical angle and the voltage amplitude; the vanadium redox flow battery is connected to the grid through the bidirectional converter.

[0007] In a possible implementation manner, before constructing the efficiency model for characterizing the corresponding relationship among the discharge energy of the vanadium redox flow battery, the energy consumption of the circulation pump, and the battery efficiency, it further includes: Determine the stack resistance, Coulomb efficiency, and power loss of the circulation pump based on the said flow rate; Determine the voltage efficiency based on the said stack resistance and open-circuit voltage; Determine the energy efficiency based on the said Coulomb efficiency and the said voltage efficiency; Determine the said discharge energy based on the said energy efficiency; Determine the energy consumption of the circulation pump based on the power loss of the circulation pump.

[0008] In a possible implementation manner, the determining the optimal efficiency based on the temperature of the electrolyte of the all-vanadium redox flow battery, the flow rate at the stack inlet, and the said efficiency model, and setting the said temperature and the said flow rate to the optimal temperature and the optimal flow rate corresponding to the optimal efficiency includes: When the said temperature is lower than the preset value, increase the frequency of the circulation pump to increase the said flow rate; When the said temperature is higher than or equal to the preset value, decrease the frequency of the circulation pump to decrease the said flow rate; Until the efficiency corresponding to the said efficiency model is the maximum, determine the said optimal efficiency, and the optimal temperature and the optimal flow rate corresponding to the optimal efficiency.

[0009] In a possible implementation manner, the said power command includes an active power command and a reactive power command; The determining the electrical angle of the active output and the voltage amplitude of the reactive output by using the VSG control method, and controlling the bidirectional converter to output an output voltage that meets the grid demand based on the said electrical angle and the said voltage amplitude includes: Determine the electrical angle of the active output based on the said active power command and the active frequency control; Determine the voltage amplitude of the reactive output based on the said reactive power command and the reactive voltage control; Determine the reference voltage based on the said electrical angle of the active output and the said voltage amplitude of the reactive output; Control the bidirectional converter to output the said output voltage based on the said reference voltage.

[0010] In a possible implementation manner, the controlling the bidirectional converter to output the said output voltage based on the said reference voltage includes: Generate a modulation signal based on the said reference voltage; Drive the IGBT switches of the bidirectional converter based on the said modulation signal to output the said output voltage.

[0011] In a possible implementation manner, after driving the IGBT switches of the bidirectional converter based on the said modulation signal to output the said output voltage, it further includes: Modify the output voltage based on the virtual impedance; The modified output voltage is as follows:

[0012] Wherein, U i represents the i th modified output voltage, U ref represents the reference voltage, Z line represents the line impedance, Z virtual represents the virtual impedance, I i represents the i th output current.

[0013] In a possible implementation manner, the expression of the efficiency model is as follows:

[0014] Wherein, EE system represents the battery efficiency, E discharge represents the discharge energy, E pump represents the energy consumption of the circulation pump, V oc represents the open circuit voltage, I represents the discharge current, t represents the discharge time.

[0015] In a second aspect, the present invention further provides a device for a vanadium redox flow battery energy storage system, including: A construction unit for constructing an efficiency model for characterizing the corresponding relationship between the discharge energy of the vanadium redox flow battery, the energy consumption of the circulation pump, and the battery efficiency; A determination unit for determining the optimal efficiency based on the temperature of the electrolyte of the vanadium redox flow battery, the flow rate at the inlet of the stack, and the efficiency model, and setting the temperature and the flow rate as the optimal temperature and the optimal flow rate corresponding to the optimal efficiency; A control unit for using the VSG control method and the power command to determine the electrical angle of the active power output and the voltage amplitude of the reactive power output, and controlling the bidirectional converter to output an output voltage that meets the grid demand based on the electrical angle and the voltage amplitude; the vanadium redox flow battery is incorporated into the grid through the bidirectional converter.

[0016] In a third aspect, the present invention further provides an electronic device, including a memory and a processor, wherein, The memory is used for storing programs; The processor, coupled to the memory, is configured to execute the program stored in the memory to implement the control method of the all-vanadium redox flow battery energy storage system in any of the above implementation manners.

[0017] In a fourth aspect, the present invention further provides a computer-readable storage medium for storing a computer-readable program or instruction, and when the program or instruction is executed by a processor, it can implement the steps in the control method of the all-vanadium redox flow battery energy storage system in any of the above implementation manners.

[0018] The beneficial effects of the present invention are as follows: The control method and device of the all-vanadium redox flow battery energy storage system provided by the present invention consider the energy consumption of the circulation pump to construct an efficiency model, and optimize the efficiency model according to the temperature of the electrolyte of the all-vanadium redox flow battery and the flow rate at the inlet of the stack to determine the optimal temperature and the optimal flow rate, and set the temperature and the flow rate to the optimal temperature and the optimal flow rate to improve the efficiency of the all-vanadium redox flow battery, and connect the all-vanadium redox flow battery to the power grid through a bidirectional converter, and adopt a VSG control method to control the bidirectional converter to simulate the operating characteristics of a synchronous generator, output an output voltage that meets the grid requirements, endow the VRFB with inertia support ability through the VSG control method, improve the stability of the new energy power grid, and achieve a double improvement of grid demand response and system efficiency, providing strong support for the access of new energy and the stable operation of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those skilled in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0020] Figure 1 It is a schematic flowchart of an embodiment of the control method of the all-vanadium redox flow battery energy storage system provided by the present invention; Figure 2 It is a schematic diagram of the relationship curves of VE, CE, EE and system efficiency with flow rate during the operation of a 500kW stack provided by the present invention; Figure 3 It is a schematic diagram of the relationship curves of the efficiency of a 500kW stack with flow rate at different temperatures provided by the present invention; Figure 4 It is a topology diagram of a 2.5MW all-vanadium redox flow battery module provided by the present invention; Figure 5 It is a block diagram of active power frequency control provided by the present invention; Figure 6 It is a block diagram of reactive power voltage control provided by the present invention; Figure 7The VSG multi - machine parallel control block diagram provided by the present invention; Figure 8 The schematic diagrams of voltage, current, active power and reactive power waveforms when two - path VSGs in parallel cut off the virtual impedance provided by the present invention; Figure 9 The schematic diagrams of voltage, current, active power and reactive power waveforms when two - path VSGs in parallel connect the virtual impedance provided by the present invention; Figure 10 The schematic diagram of the grid - connection response test curve of the VSG converter provided by the present invention; Figure 11 The schematic structural diagram of an embodiment of the device of the all - vanadium redox flow battery energy storage system provided by the present invention; Figure 12 The schematic structural diagram of an embodiment of the electronic device provided by the present invention. Detailed implementation manners

[0021] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present invention.

[0022] In the description of the embodiments of the present invention, unless otherwise specified, "a plurality of" means two or more. "And / or" describes the association relationship of associated objects, indicating that there can be three relationships, for example: A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone these three situations.

[0023] The descriptions such as "first", "second", etc. involved in the embodiments of the present invention are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Therefore, the technical features defined with "first" and "second" may explicitly or implicitly include at least one such feature.

[0024] Referring to "embodiment" in this article means that the specific features, structures or characteristics described in connection with the embodiment may be included in at least one embodiment of the present invention. The phrase appears in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0025] Before presenting the embodiments, the structure and working principle of the all - vanadium redox flow battery will be described first.

[0026] The structure of a vanadium redox flow battery mainly consists of modules such as a stack, pipelines, positive and negative liquid storage tanks, and positive and negative circulation pumps. The vanadium electrolyte circulates and is stored in the liquid storage tanks, pipelines, and stack. The stack is composed of end plates, graphite bipolar plates, electrodes, ion exchange membranes, and seals. There are four valence states of vanadium ions in the electrolyte, namely blue VO 2+ and orange V 2+ and green V 3+ .

[0027] The working principle is as follows: During charging, VO 2+ at the positive electrode loses electrons and is oxidized to . Electrons reach the negative electrode through the circuit. V 3+ at the negative electrode gains electrons and is reduced to V 2+ . During discharging, at the positive electrode gains electrons and is reduced to VO 2+ . V 2+ at the negative electrode loses electrons and is oxidized to V 3 + .

[0028] The reaction equations are as follows: (1) Charge and discharge at the negative electrode: (2) Total reaction: (3) According to the Nernst equation of the electrochemical reaction, ignoring the influence of hydrogen atom concentration, the electromotive force of the battery is: (4) In the above formula, V oc is the electromotive force of the stack, U cell is the electromotive force of a single cell, N is the number of single cells, R is the ideal gas constant, generally taken as 8.314, F is the Faraday constant, generally taken as 96485 C / mol, z is the number of equivalents per mole of redox substance, E 0 is the standard electrode potential of the positive and negative electrodes of the redox reaction battery, taken as 1.259.

[0029] The state of charge (SOC) of the battery is defined as the ratio of the current remaining charge of the battery to the rated capacity of the battery, and the expression is:

[0030] The SOC value ranges from 0 to 1. The larger the SOC, the more electric energy the battery stores.

[0031] For a vanadium redox flow battery, the SOC can be expressed by the concentration ratio of vanadium ions in different valence states in the electrolyte.

[0032] Positive electrolyte: (6) Negative electrolyte: (7) The Nernst equation can also be written as:

[0033] According to the open-circuit voltage and SOC curves of a single cell at different temperatures, the voltage range of a single cell is between 1.1 - 1.4V. The SOC is in the linear region within [0.15, 0.85], and the SOC is in the non-linear regions within [0, 0.15] and [0.85, 1]. The voltage range of an 88-cell single stack is between 96.8 - 123.2V, and the voltage range of a five-series stack module is between 484 - 616V.

[0034] The present invention provides a control method and device for a vanadium redox flow battery energy storage system, which will be described separately below.

[0035] Figure 1 It is a schematic flow chart of an embodiment of the control method for the vanadium redox flow battery energy storage system provided by the present invention. As Figure 1 shown, the control method for the vanadium redox flow battery energy storage system includes: S101. Construct an efficiency model for characterizing the corresponding relationship between the discharge energy of the vanadium redox flow battery, the energy consumption of the circulation pump, and the battery efficiency.

[0036] In a vanadium redox flow battery, the stack resistance decreases as the flow rate at the stack inlet increases. Therefore, the stack resistance can be determined according to the flow rate, and the discharge voltage of the vanadium redox flow battery can be obtained based on the stack resistance.

[0037] Thus, the voltage efficiency can be obtained according to the ratio of the discharge voltage to the open-circuit voltage.

[0038] The change in the flow rate will affect the uniformity of electrolyte mixing, and the coulombic efficiency decreases as the flow rate increases. Therefore, the coulombic efficiency can be determined according to the flow rate.

[0039] Thus, the energy efficiency can be obtained according to the product of the voltage efficiency and the coulombic efficiency, and the discharge energy can be obtained based on the energy efficiency.

[0040] When calculating the system efficiency, the energy consumption loss of the circulation pump needs to be subtracted. The power of the circulation pump and the flow rate are approximately in a quadratic relationship. Therefore, the power of the circulation pump can be determined according to the flow rate, and then the energy consumption loss of the circulation pump can be calculated based on the power of the circulation pump.

[0041] Thus, based on the discharge energy of the all-vanadium redox flow battery and the energy consumption of the circulation pump, an efficiency model is constructed to characterize the corresponding relationship among the discharge energy of the all-vanadium redox flow battery, the energy consumption of the circulation pump, and the battery efficiency. The efficiency model can be used to evaluate the overall efficiency of the all-vanadium redox flow battery under different conditions.

[0042] S102. Based on the temperature of the electrolyte of the all-vanadium redox flow battery, the flow rate at the inlet of the stack, and the efficiency model, determine the optimal efficiency, and set the temperature and the flow rate as the optimal temperature and the optimal flow rate corresponding to the optimal efficiency.

[0043] The flow rate at the inlet of the stack can be monitored in real time through a flow sensor, and the temperature data of the electrolyte can be collected through a temperature sensor.

[0044] By adjusting the temperature of the electrolyte and the flow rate at the inlet of the stack, observe the change of the system efficiency, and use an optimization algorithm to find the optimal temperature and the optimal flow rate that maximize the system efficiency.

[0045] Exemplarily, with the goal of maximizing the system efficiency, the optimization variables are temperature and flow rate. Optimize the efficiency model. When the efficiency is the highest, the optimal efficiency is obtained.

[0046] It can be understood that the optimal temperature and the optimal flow rate corresponding to the optimal efficiency are the optimal temperature and the optimal flow rate.

[0047] And set the temperature and the flow rate as the optimal temperature and the optimal flow rate to ensure the highest efficiency of the all-vanadium redox flow battery.

[0048] S103. Use the VSG control method and the power command to determine the electrical angle of the active power output and the voltage amplitude of the reactive power output, and control the bidirectional converter to output the output voltage that meets the grid demand based on the electrical angle and the voltage amplitude; the all-vanadium redox flow battery is connected to the grid through the bidirectional converter.

[0049] Connect the all-vanadium redox flow battery to the grid through the bidirectional converter. The bidirectional converter can realize the bidirectional energy flow between the battery and the grid, and can both discharge to the grid and charge from the grid. After being connected to the grid, the all-vanadium redox flow battery can be used as an energy storage device, discharging when the grid demand is high and charging when the grid demand is low, so as to balance the supply and demand relationship of the grid and improve the stability and reliability of the grid.

[0050] The virtual synchronous generator (VSG) control method is a control strategy that simulates the operating characteristics of a synchronous generator, enabling a bidirectional converter to simulate the inertia and damping characteristics of a synchronous generator, thereby enhancing the stability of the power grid and being applicable to power grids with a high proportion of renewable energy access.

[0051] The VSG control method can simulate the inertia of a synchronous generator, provide virtual inertia for the power grid, and help suppress frequency fluctuations. It can automatically adjust the output power to respond to frequency changes. In addition to active power support, it can also provide reactive power support.

[0052] By using the VSG control method and power command to control the bidirectional converter to simulate the operating characteristics of a synchronous generator, a target voltage waveform matching the power grid demand is generated, and an output voltage that meets the power grid demand is output.

[0053] The power command includes an active power command and a reactive power command. The active power command is used to regulate the active power output by the VSG to ensure power balance in the power grid. The reactive power command is used to regulate the reactive power output by the VSG to maintain the stability of the power grid voltage and improve the power quality.

[0054] For example, the electrical angle output by the active - frequency droop control and the voltage amplitude of the reactive - voltage droop control and reactive output can be used to control the bidirectional converter to output an output voltage that meets the power grid demand, realizing the power grid support function. The multi - machine parallel circulating current is suppressed through virtual impedance compensation, and the dynamic response and waveform quality are ensured through double - closed - loop control + SVPWM modulation.

[0055] In summary, the control method of the all - vanadium redox flow battery energy storage system provided by the embodiments of the present invention constructs an efficiency model considering the energy consumption of the circulation pump, optimizes the efficiency model according to the temperature of the electrolyte of the all - vanadium redox flow battery and the flow rate at the inlet of the stack to determine the optimal temperature and optimal flow rate, sets the temperature and flow rate as the optimal temperature and optimal flow rate to improve the efficiency of the all - vanadium redox flow battery, incorporates the all - vanadium redox flow battery into the power grid through a bidirectional converter, and uses the VSG control method to control the bidirectional converter to simulate the operating characteristics of a synchronous generator, output an output voltage that meets the power grid demand, endow the VRFB with inertia support ability through the VSG control method, enhance the stability of the new - energy power grid, and achieve a double improvement in power grid demand response and system efficiency, providing strong support for the access of renewable energy and the stable operation of the power grid.

[0056] In some embodiments of the present invention, before constructing the efficiency model for characterizing the corresponding relationship between the discharge energy of the all - vanadium redox flow battery, the energy consumption of the circulation pump, and the battery efficiency, it further includes: Determine the stack resistance, Coulomb efficiency, and power loss of the circulation pump based on the said flow rate; Determine the voltage efficiency based on the stack resistance and open circuit voltage; Determine the energy efficiency based on the Coulomb efficiency and the voltage efficiency; Determine the discharge energy based on the energy efficiency; Determine the energy consumption of the circulation pump based on the power loss of the circulation pump.

[0057] In some embodiments of the present invention, the expression of the efficiency model is as follows:

[0058] Wherein, EE system represents the battery efficiency, E discharge represents the discharge energy, E pump represents the energy consumption of the circulation pump, V oc represents the open circuit voltage, I represents the discharge current, t represents the discharge time.

[0059] The relationships between the stack energy efficiency, voltage efficiency, charge-discharge energy and flow rate of the all-vanadium redox flow battery can be demonstrated by formula derivation or charts to show the changing trends of these parameters.

[0060] Stack resistance R decreases with the increase of the flow rate Q as follows: (mΩ) (9) Wherein, a and b are stack resistance parameters, is the temperature coefficient, both of which are fitting constants.

[0061] Voltage efficiency VE is defined as the ratio of the actual discharge voltage to the open circuit voltage, as follows: (10) On the premise of ignoring the influence of temperature, the change of the flow rate will affect the electrolyte mixing uniformity, and the Coulomb efficiency CE decreases with the increase of the flow rate, as follows: (11) Wherein, c and d are Coulomb efficiency parameters, is the temperature coefficient, both of which are fitting parameters.

[0062] Energy efficiency EE is the product of the voltage efficiency VE and the coulombic efficiency CE as follows: (12) Pump power P pump has an approximate quadratic relationship with the flow rate Q as follows: (13) where k is the pump power loss constant

[0063] The energy consumption of the pump E pump is as follows: (kWh)(14) Discharge energy E discharge is as follows: (kWh)(15) Calculating the total system efficiency EE system , the pump loss needs to be deducted as follows: (16) It can be seen from the above formula that as the flow rate increases, the voltage efficiency gradually increases because after the flow rate increases, the electrolyte circulates sufficiently, the concentration polarization becomes smaller, and the internal resistance also becomes smaller. The coulombic efficiency is mainly related to the ion transfer of the proton exchange membrane and does not change significantly with the flow rate. Since the energy efficiency is the product of the voltage efficiency and the coulombic efficiency, in order to improve the overall efficiency of the system, the energy efficiency of the stack should be increased, the internal resistance should be reduced to increase the voltage efficiency, and the circulation speed of the electrolyte can be increased during system operation, and the output frequency of the circulation pump can be increased to increase the flow rate.

[0064] In some embodiments of the present invention, determining the optimal temperature and optimal flow rate corresponding to the optimal efficiency based on the temperature of the electrolyte of the all-vanadium redox flow battery, the flow rate at the stack inlet, and the rate model includes: When the temperature is lower than the preset value, increase the frequency of the circulation pump to increase the flow rate; When the temperature is higher than or equal to the preset value, reduce the frequency of the circulation pump to reduce the flow rate; Until the efficiency corresponding to the efficiency model is the maximum, determine the optimal efficiency, and the optimal temperature and optimal flow rate corresponding to the optimal efficiency.

[0065] To verify the data consistency between simulation and experiment, a large number of tests and experiments were carried out on a 500 kW stack module to record data, and the data was input into a computer to fit the parameters of the above voltage efficiency and Coulomb efficiency as shown in Table 1.

[0066] Table 1: Parameters of the mathematical model for stack efficiency test

[0067] Figure 2 It is a schematic diagram of the relationship curves between VE, CE, EE and system efficiency and flow rate during the operation of the 500 kW stack provided by the present invention. Figure 2 (a) is the relationship curve of energy efficiency and flow rate, Figure 2 (b) is the relationship curve of Coulomb efficiency and flow rate, Figure 2 (c) is the relationship curve of voltage efficiency and flow rate, Figure 2 (d) is the relationship curve of system efficiency and flow rate.

[0068] As Figure 2 shown, under the condition of an ambient temperature of 25 °C, during the initial stage of stack operation, increasing the circulation speed of the electrolyte to reduce the internal resistance can, to a certain extent, improve the voltage efficiency VE, while the change in Coulomb efficiency CE is not obvious. Therefore, the energy efficiency EE increases, but when the flow rate increases to a certain extent, the influence of the increasing pump loss becomes greater and greater, resulting in an inflection point in the system efficiency. Therefore, it is necessary to find the flow rate corresponding to the maximum system efficiency to optimize the system efficiency.

[0069] However, during the actual operation process, the temperature of the stack is variable. Figure 3 It is a schematic diagram of the relationship curves between the efficiency and flow rate of the 500 kW stack at different temperatures provided by the present invention.

[0070] Figure 3 (a) is the energy efficiency curve at different temperatures, Figure 3 (b) is the voltage efficiency curve at different temperatures, Figure 3 (c) is the Coulomb efficiency curve at different temperatures, Figure 3 (d) is the system efficiency diagram at different temperatures.

[0071] As Figure 3 shown, as the temperature increases, the ion diffusion rate accelerates, the resistance decreases, and the voltage efficiency increases, but the Coulomb efficiency decreases, and the overall energy efficiency EE is not high. It is necessary to reduce the flow rate to achieve the optimal efficiency. In a low-temperature environment, it is necessary to increase the flow rate to reduce the resistance and improve the voltage efficiency to achieve the optimal system efficiency.

[0072] The above test results demonstrate the importance of thermal management during operation. When designing the control algorithm, temperature, flow rate, and pump loss need to be considered. The electrolyte temperature is maintained stable through water cooling, and the flow rate is controlled in a closed loop by a circulation pump to achieve an algorithm for optimizing system efficiency.

[0073] The 500kW stack module was set to different flow rates, and multiple charge-discharge tests were conducted. The test results are shown in Tables 2 and 3.

[0074] Table 2: Test data for controlling the efficiency of a 500kW stack using an integrated control model at 25°C

[0075] Table 3: Test data for controlling the efficiency of a 500kW stack using a traditional control model at 25°C

[0076] The experimental results show that the temperature-flow closed-loop control improves the system efficiency by 3%. Under temperature fluctuations, the flow rate needs to be dynamically adjusted to maintain the optimal system efficiency.

[0077] That is, the present invention provides a temperature compensation strategy. In a low-temperature environment (temperature below the preset value), the flow rate is increased to reduce the stack resistance and compensate for the increase in viscosity caused by low temperature. In a high-temperature environment (temperature higher than or equal to the preset value), the flow rate is reduced to suppress ion crossover loss and balance the decrease in Coulomb efficiency.

[0078] The control method of the all-vanadium redox flow battery energy storage system provided by the embodiment of the present invention proposes a closed-loop flow control algorithm based on electrochemical coupling, which couples the temperature-flow-efficiency model and quantifies the multi-physical field coupling effect, and can significantly reduce pump loss and improve system efficiency.

[0079] In some embodiments of the present invention, the power command includes an active power command and a reactive power command; The method of using the VSG control method and the power command to determine the electrical angle of the active output and the voltage amplitude of the reactive output, and controlling the bidirectional converter to output an output voltage that meets the grid demand based on the electrical angle and the voltage amplitude includes: Determining the electrical angle of the active output based on the active power command and the active frequency control; Determining the voltage amplitude of the reactive output based on the reactive power command and the reactive voltage control; Determining a reference voltage based on the electrical angle of the active output and the voltage amplitude of the reactive output; Controlling the bidirectional converter to output the output voltage based on the reference voltage.

[0080] The all-vanadium redox flow battery converts the voltage into alternating current through the PCS and connects it to the distribution network. The PCS adopts corresponding control strategies to activate and charge / discharge the battery, thereby achieving the corresponding control objectives of the power grid.

[0081] The electrical control system of VRFB consists of a BMS power management system, a PCS bidirectional converter, and a DC / DC DC converter. Figure 4 For the 2.5MW all-vanadium redox flow battery module topology provided by the present invention, as Figure 4 shown, the high voltage side of the energy storage transformer is 35kV, and the low voltage side is 300V. It is connected to the stack through 5 paths of PCS+DCDC, and the stack is controlled by the BMS for battery management.

[0082] When the battery is powered on for the first time, the DC / DC DC converter module is required to activate it. After the battery is activated using PCS+DC / DC (charged to the lowest voltage of the battery), the DC / DC exits operation, and the main circuit bypass switch K1 closes, switching to the PCS to directly charge and discharge the battery, which can reduce losses and improve the charge and discharge efficiency.

[0083] Figure 4 For the 2.5MW battery module topology shown, it is connected to the power grid in parallel through the PCS. To achieve stable parallel output, reduce system circulating current, and solve the problem of uneven power distribution, the VSG parallel control strategy is used for precise control.

[0084] Aiming at the problems of circulating current and power coupling existing in the system of converter parallel connection, virtual impedance is introduced into the voltage and current loops to make the equivalent impedance of the system inductive, so as to reduce the circulating current and achieve power decoupling.

[0085] The VSG control method includes active-frequency control and reactive-voltage control.

[0086] Figure 5 For the active frequency control block diagram provided by the present invention, the inertia and damping links of the synchronous generator are introduced into the control strategy of active power control. The rotor mechanical equation of VSG is: (17) Among them, J is the moment of inertia, is the virtual electrical angular velocity, is the mechanical active power, is the electromagnetic active power, D is the damping coefficient, is the rated angular velocity.

[0087] When the active power of the system changes and the frequency also deviates, the droop control strategy is used to adjust the active power output, and the difference between the virtual electrical angular velocity and the rated angular velocity is adjusted. The frequency modulation controller is: (18) P ref is the active power command value, is the droop coefficient, which can be obtained from Equations (17) and (18): (19) The above formula is transformed into a control block diagram as Figure 5 shown.

[0088] Figure 6 is the reactive voltage control block diagram provided by the present invention. The reactive power control of the VSG is the droop control of reactive power and voltage, and the expression is: (20) The droop control strategy enables the PCS inverter to satisfy the characteristics of primary voltage regulation. In the above formula is the amplitude of the VSG output voltage, U n is the no-load voltage amplitude, K q is the droop coefficient of reactive voltage control, Q ref is the reactive power command value, Q e is the output reactive power value. The above formula is transformed into a control block diagram as Figure 6 shown.

[0089] In some embodiments of the present invention, controlling the bidirectional converter to output the output voltage based on the reference voltage includes: generating a modulation signal based on the reference voltage; driving the IGBT switch of the bidirectional converter based on the modulation signal to output the output voltage.

[0090] In the main circuit topology of the VSG, the electrical angle of the active output and the voltage amplitude of the reactive output can be calculated through the VSG control algorithm added in the PQ control link, and then the corresponding SVPWM signal (i.e., the modulation signal) is generated through the voltage-current double closed-loop module.

[0091] Driving the IGBT through the modulation signal enables the bidirectional converter to realize the function of an inverter, simulating the operating characteristics of a synchronous generator to output an output voltage that meets the grid requirements.

[0092] Combining the pre-synchronization control strategy, Figure 7 is the VSG multi-machine parallel control block diagram provided by the present invention. The overall control block diagram of the VSG is as Figure 7As shown, the three-phase reference voltage amplitude and phase angle generated by the active-power / frequency and reactive-power / voltage droop equations enable the inverter output to have the same "inertia" and "damping" characteristics as a generator, ensuring safe and stable operation after large-scale grid connection.

[0093] In some embodiments of the present invention, after driving the IGBT switches of the bidirectional converter based on the modulation signal to output the output voltage, it further includes: Correcting the output voltage based on virtual impedance; The corrected output voltage is as follows:

[0094] Wherein, U i represents the i th corrected output voltage, U ref represents the reference voltage, Z line represents the line impedance, Z virtual represents the virtual impedance, I i represents the i th output current.

[0095] Traditional droop control or VSG control in a multi-machine parallel system can lead to uneven power distribution and circulating current problems due to line impedance differences. An improved VSG + virtual impedance compensation control strategy is proposed below, which can make the output power of each energy storage unit more balanced.

[0096] Considering a multi-VSG parallel system, the output voltage and current of each VSG can be expressed as:

[0097] Wherein, U i is the output voltage of the i-th VSG, U ref is the reference voltage, Z line is the line impedance, I i is the output current of the i-th VSG.

[0098] When the virtual impedance Z virtual =R virtual +jX virtual is introduced, the output voltage of each VSG can be expressed as:

[0099] By adjusting R virtual and X virtual values, the influence caused by different line impedances of each VSG output can be compensated.

[0100] The improved VSG control block diagram is as Figure 7 shown. The adaptive virtual impedance compensation module can calculate the virtual impedance value in real time, and the output of the adaptive compensation function is superimposed on the voltage command value. This module has a power sharing function and can dynamically adjust the droop coefficient K p and K q to ensure that the VSG power is distributed according to the capacity ratio.

[0101] To verify the effect of the improved VSG multi-machine parallel connection in suppressing circulating current, the following simulation verification is carried out: The virtual impedance is designed as follows. Assuming the system reference impedance Z base = 0.1 + 0.2j Ω, then the line impedances of each VSG are as follows: VSG branch 1: Z line,1 = 0.05 + 0.15j Ω.

[0102] VSG branch 2: Z line,1 = 0.15 + 0.25j Ω.

[0103] The virtual impedance compensation values after adaptive calculation are as follows: VSG branch 1: Z virtual,1 = 0.05 + 0.05j Ω.

[0104] VSG branch 2: Z virtual,1 = -0.05 - 0.05j Ω.

[0105] Build a 2-VSG parallel system, and set the grid-connected circulating current suppression module in the simulation model. When the virtual impedance suppression link is removed, Figure 8 Figure Figure 8 The voltage, current, active power and reactive power waveforms of the two-way VSG parallel connection provided by the present invention when the virtual impedance is removed are shown in Fig. Figure 8 Among them, Figure 8 (a) is the schematic diagram of the grid-connected three-phase voltage waveform, Figure 8 (b) is the schematic diagram of the grid-connected three-phase current waveform,

[0106] AsFigure 8 As shown, after the VSG branch 1 is delayed and then the VSG branch 2 is put into operation, oscillations and divergence occur in the three-phase current, active power, and reactive power, among which the phenomenon of increasing current circulation occurs.

[0107] When the virtual impedance suppression link is put into operation, Figure 9 It is a schematic diagram of voltage, current, active, and reactive power waveforms when two VSGs of the present invention are put into parallel with virtual impedance. Among them, Figure 9 (a) is a schematic diagram of the grid-connected three-phase voltage waveform, Figure 9 (b) is a schematic diagram of the grid-connected three-phase current waveform, Figure 9 (c) is a schematic diagram of the active power waveform, Figure 9 (d) is a schematic diagram of the reactive power waveform.

[0108] As Figure 9 shown, after the VSG branch 1 is delayed and then the VSG branch 2 is put into operation, the three-phase voltage, current, active power, and reactive power all quickly converge to a stable state after the VSG branch is put into operation, and the active power is stable at the set value of 200 kW with a small circulation.

[0109] By building an experimental platform to verify the above scheme, the 500 kW VRFB stack module of the all-vanadium redox flow energy storage power station is composed of 15 stacks of 37.5 kW. A 500 kW physical test platform is built. The configuration of the experimental test platform is as follows: single-stack power 37.5 kW, 88 pieces, rated voltage 484 - 685 V, maximum current 1033 A, and each stack group is controlled by a set of BMS and PCS and connected to the energy storage system.

[0110] For the grid-connected switching response time test, the performance of the converter VSG grid-connected switching directly affects the rapidity and stability of the energy storage system's participation in frequency modulation and peak shaving. Each converter with VSG function can be regarded as a virtual generator. Different from the grid-following converter, the VSG converter does not need to perform grid synchronization through PLL phase locking in real time. The grid connection includes the following three steps: including pre-synchronization control, grid-connected switching control, and rapid stabilization after grid connection.

[0111] Figure 10 It is a schematic diagram of the VSG converter grid-connected response test curve provided by the present invention, Figure 10 (a) is the pre-synchronization phase alignment waveform diagram, Figure 10 (b) is the pre-synchronization frequency alignment, Figure 10 (c) is the pre-synchronization voltage alignment diagram, Figure 10 (d) is the current response diagram after grid connection, Figure 10 (e) is the active power response diagram, Figure 10 (f) is the reactive power response diagram.

[0112] Pre-synchronization control accurately locks the phase of the output voltage and the grid voltage through a PLL. As shown in Figure 10 (a), the phase deviation is less than 1%. The amplitude of the VSG output voltage is adjusted to align with the grid by regulating the reactive power control loop. As shown in Figure 10 (f), the voltage amplitude deviation is less than 1%. The virtual rotor angular velocity of the VSG is adjusted to match the grid. As shown in Figure 10 (b), the frequency deviation is less than 0.05 Hz. When the above three indicators are met, the amplitude, phase, and frequency of the converter output voltage are consistent with the grid voltage, and the controller outputs a grid connection switching command.

[0113] Stable operation after grid connection. After grid connection, the converter adjusts the output frequency and voltage to remain synchronized with the grid, and dynamically adjusts the output active power and reactive power according to the grid power requirements. Inertia support is provided by simulating the inertia of the VSG, and the voltage stability is maintained through voltage droop control, thus simulating the access characteristics of a synchronous generator. Generally, the pre-synchronization time and dynamic response time of VSG grid connection switching are adjusted to within 200 - 300 ms. The pre-synchronization response time of this system is 150 ms, and the stable time after full-power grid connection is 150 ms. Through parameter adjustment and optimization, it can be achieved within 120 ms.

[0114] Virtual impedance suppression link for multi-machine parallel harmonic testing. Comparison before and after the virtual impedance link is put into operation. Before putting it into operation, the THD of the double-machine parallel current harmonic content is 17.27%. After putting it into operation, the double-machine parallel current harmonic content is reduced to 2.87%. The proportion of each harmonic before and after putting it into operation is shown in Table 4.

[0115] Table 4: Results of multi-machine parallel harmonic testing

[0116] The experimental results show that when the virtual impedance suppression link is put into operation during multi-machine parallel operation, the output current harmonic content can be reduced to less than 3%, meeting the standard requirements.

[0117] The VSG-VRFB coupled control of the system shortens the inertia response time to 150 ms, meeting the grid frequency regulation requirements; the system efficiency is improved by 3% through flow-temperature closed-loop optimization, verifying the necessity of dynamic regulation; the virtual impedance compensates the multi-machine circulating current to less than 3%, supporting the stable operation of the megawatt-level system.

[0118] That is, the present invention proposes an optimal control algorithm for an efficient high-power VRFB energy storage system. At the technical level, the VSG control strategy of the virtual synchronous generator endows the VRFB with inertia support ability, improving the stability of the high-proportion new energy grid; at the economic level, the flow field optimization and adaptive circulating current suppression technology can increase the overall system efficiency to more than 75%, significantly reducing the cost per kilowatt-hour.

[0119] Through the VSG-VRFB dynamic coupling control architecture, integrating the VSG droop characteristic and the stack model, the grid inertia support response time is achieved to be < 150 ms; the system efficiency is optimized by 3% through closed-loop flow control, breaking through the limitations of traditional static control; through the multi-machine parallel adaptive algorithm, the virtual impedance compensation suppresses the circulating current to below 3%, supporting the stable operation of the megawatt-level system.

[0120] In order to better implement the control method of the all-vanadium redox flow battery energy storage system in the embodiments of the present invention, correspondingly, based on the control method of the all-vanadium redox flow battery energy storage system, as Figure 11 shown, the embodiments of the present invention further provide a device of an all-vanadium redox flow battery energy storage system. The device 1100 of the all-vanadium redox flow battery energy storage system includes: A construction unit 1101, configured to construct an efficiency model for characterizing the corresponding relationship among the discharge energy of the all-vanadium redox flow battery, the energy consumption of the circulation pump, and the battery efficiency; A determination unit 1102, configured to determine the optimal efficiency based on the temperature of the electrolyte of the all-vanadium redox flow battery, the flow rate at the stack inlet, and the efficiency model, and set the temperature and the flow rate as the optimal temperature and the optimal flow rate corresponding to the optimal efficiency; the all-vanadium redox flow battery is connected to the grid through a bidirectional converter; A control unit 1103, configured to use the VSG control method and the power command to determine the electrical angle of the active power output and the voltage amplitude of the reactive power output, and control the bidirectional converter to output an output voltage that meets the grid demand based on the electrical angle and the voltage amplitude; the all-vanadium redox flow battery is connected to the grid through a bidirectional converter.

[0121] The device 1100 of the all-vanadium redox flow battery energy storage system provided in the above embodiments can implement the technical solutions described in the embodiments of the control method of the all-vanadium redox flow battery energy storage system. The specific implementation principles of the above modules or units can be referred to the corresponding content in the embodiments of the control method of the all-vanadium redox flow battery energy storage system, and will not be elaborated here.

[0122] As Figure 12 shown, the present invention also correspondingly provides an electronic device 1200. The electronic device 1200 includes a processor 1201, a memory 1202, and a display 1203. Figure 12 Only some components of the electronic device 1200 are shown, but it should be understood that it is not required to implement all the shown components, and more or fewer components can be alternatively implemented.

[0123] In some embodiments, the processor 1201 may be a central processing unit (CPU), a microprocessor, or other data processing chips, which are used to run the program code stored in the memory 1202 or process data, such as the control method of the all-vanadium redox flow battery energy storage system in the present invention.

[0124] In some embodiments, the processor 1201 may be a single server or a server group. The server group may be centralized or distributed. In some embodiments, the processor 1201 may be local or remote. In some embodiments, the processor 1201 may be implemented on a cloud platform. In some embodiments, the cloud platform may include a private cloud, a public cloud, a hybrid cloud, a community cloud, a distributed cloud, an internal cloud, a multi-cloud, etc., or any combination of the above.

[0125] In some embodiments, the memory 1202 may be an internal storage unit of the electronic device 1200, such as the hard disk or memory of the electronic device 1200. In some other embodiments, the memory 1202 may also be an external storage device of the electronic device 1200, such as a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) card, a Flash Card, etc., equipped on the electronic device 1200.

[0126] Furthermore, the memory 1202 may also include both the internal storage unit and the external storage device of the electronic device 1200. The memory 1202 is used to store the application software installed in the electronic device 1200 and various types of data.

[0127] In some embodiments, the display 1203 may be an LED display, a liquid crystal display, a touch liquid crystal display, an Organic Light-Emitting Diode (OLED) toucher, etc. The display 1203 is used to display the information in the electronic device 1200 and to display a visual user interface. The components 1201-1203 of the electronic device 1200 communicate with each other through a system bus.

[0128] In one embodiment, when the processor 1201 executes the program of the all-vanadium redox flow battery energy storage system in the memory 1202, the following steps may be implemented: Construct an efficiency model for characterizing the corresponding relationship between the discharge energy of the all-vanadium redox flow battery, the energy consumption of the circulation pump, and the battery efficiency; Optimize the efficiency model based on the temperature of the electrolyte of the all-vanadium redox flow battery and the flow rate at the inlet of the stack, and determine the optimal temperature and optimal flow rate corresponding to the optimal efficiency; Set the temperature and the flow rate to the optimal temperature and the optimal flow rate; Use the VSG control method to determine the electrical angle of the active power output and the voltage amplitude of the reactive power output, and control the bidirectional converter to output an output voltage that meets the grid demand based on the electrical angle and the voltage amplitude.

[0129] It should be understood that when the processor 1201 executes the program of the all-vanadium redox flow battery energy storage system in the memory 1202, in addition to the above functions, other functions can also be realized. For details, please refer to the description of the corresponding method embodiments above.

[0130] Furthermore, the embodiments of the present invention do not specifically limit the type of the mentioned electronic device 1200. The electronic device 1200 can be a mobile phone, a tablet computer, a personal digital assistant (PDA), a wearable device, a laptop computer, and other portable electronic devices. Exemplary embodiments of the portable electronic device include, but are not limited to, portable electronic devices equipped with IOS, android, microsoft, or other operating systems. The above portable electronic devices can also be other portable electronic devices, such as a laptop computer with a touch-sensitive surface (such as a touch panel). It should also be understood that in some other embodiments of the present invention, the electronic device 1200 can also not be a portable electronic device, but a desktop computer with a touch-sensitive surface (such as a touch panel).

[0131] Correspondingly, the embodiments of the present invention also provide a computer-readable storage medium. The computer-readable storage medium is used to store computer-readable programs or instructions. When the programs or instructions are executed by a processor, the steps or functions in the control method of the all-vanadium redox flow battery energy storage system provided by the above method embodiments can be realized.

[0132] Those skilled in the art can understand that all or part of the processes of implementing the above method embodiments can be completed by instructing relevant hardware (such as a processor, a controller, etc.) through a computer program. The computer program can be stored in a computer-readable storage medium. Among them, the computer-readable storage medium is a magnetic disk, an optical disk, a read-only memory, or a random access memory, etc.

[0133] The control method and device of the all-vanadium redox flow battery energy storage system provided by the present invention have been introduced in detail above. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those skilled in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A control method for a vanadium redox flow battery energy storage system, characterized in that, Including: Constructing an efficiency model for characterizing the corresponding relationship among the discharge energy of a vanadium redox flow battery, the energy consumption of a circulation pump, and the battery efficiency; Based on the temperature of the electrolyte of the vanadium redox flow battery, the flow rate at the inlet of the stack, and the efficiency model, determining the optimal efficiency, and setting the temperature and the flow rate as the optimal temperature and the optimal flow rate corresponding to the optimal efficiency; Using the VSG control method and the power command to determine the electrical angle of the active power output and the voltage amplitude of the reactive power output, and controlling the bidirectional converter to output an output voltage that meets the grid demand based on the electrical angle and the voltage amplitude; The vanadium redox flow battery is connected to the grid through a bidirectional converter.

2. The control method of the all-vanadium redox flow battery energy storage system according to claim 1, wherein Before constructing the efficiency model for characterizing the corresponding relationship among the discharge energy of a vanadium redox flow battery, the energy consumption of a circulation pump, and the battery efficiency, it further includes: Based on the flow rate, determining the stack resistance, the Coulomb efficiency, and the power loss of the circulation pump; Based on the stack resistance and the open-circuit voltage, determining the voltage efficiency; Based on the Coulomb efficiency and the voltage efficiency, determining the energy efficiency; Based on the energy efficiency, determining the discharge energy; Based on the power loss of the circulation pump, determining the energy consumption of the circulation pump.

3. The control method of the all-vanadium redox flow battery energy storage system according to claim 1, wherein The determining the optimal efficiency based on the temperature of the electrolyte of the vanadium redox flow battery, the flow rate at the inlet of the stack, and the efficiency model includes: When the temperature is lower than the preset value, increasing the frequency of the circulation pump to increase the flow rate; When the temperature is higher than or equal to the preset value, decreasing the frequency of the circulation pump to decrease the flow rate; Until the efficiency corresponding to the efficiency model is the maximum, determining the optimal efficiency.

4. The control method of the all-vanadium redox flow battery energy storage system according to claim 1, characterized in that, The power command includes an active power command and a reactive power command; The using the VSG control method and the power command to determine the electrical angle of the active power output and the voltage amplitude of the reactive power output, and controlling the bidirectional converter to output an output voltage that meets the grid demand based on the electrical angle and the voltage amplitude includes: Based on the active power command and the active frequency control, determining the electrical angle of the active power output; Based on the reactive power command and the reactive voltage control, determining the voltage amplitude of the reactive power output; Based on the electrical angle of the active power output and the voltage amplitude of the reactive power output, determining the reference voltage; Based on the reference voltage, controlling the bidirectional converter to output the output voltage.

5. The control method of the all-vanadium redox flow battery energy storage system according to claim 4, characterized in that, The controlling the bidirectional converter to output the output voltage based on the reference voltage includes: Generating a modulation signal based on the reference voltage; Driving the IGBT switch of the bidirectional converter based on the modulation signal to output the output voltage.

6. The control method of the all-vanadium redox flow battery energy storage system according to claim 5, characterized in that, After driving the IGBT switch of the bidirectional converter based on the modulation signal to output the output voltage, it further includes: Correcting the output voltage based on the virtual impedance; The corrected output voltage is as follows: Among them, U i represents the i th corrected output voltage, U ref represents the reference voltage, Z line represents the line impedance, Z virtual represents the virtual impedance, I i represents the i th output current.

7. The control method of the all-vanadium redox flow battery energy storage system according to claim 1, characterized in that, The expression of the efficiency model is as follows: Among them, EE system represents the battery efficiency, E discharge represents the discharge energy, E pump represents the energy consumption of the circulation pump, V oc represents the open-circuit voltage, I represents the discharge current, t represents the discharge time.

8. An apparatus for a vanadium redox flow battery energy storage system, characterized in that, Including: A construction unit for constructing an efficiency model for characterizing the corresponding relationship among the discharge energy of a vanadium redox flow battery, the energy consumption of a circulation pump, and the battery efficiency; A determination unit, configured to determine an optimal efficiency based on the temperature of the electrolyte of the all-vanadium redox flow battery, the flow rate at the stack inlet, and the efficiency model, and set the temperature and the flow rate to the optimal temperature and the optimal flow rate corresponding to the optimal efficiency; A control unit, configured to determine the electrical angle of the active power output and the voltage amplitude of the reactive power output by using the VSG control method and a power command, and control a bidirectional converter to output an output voltage that meets the grid demand based on the electrical angle and the voltage amplitude; the all-vanadium redox flow battery is connected to the grid through the bidirectional converter.

9. An electronic device, characterized in that, It includes a memory and a processor, wherein, The memory is configured to store a program; The processor is coupled to the memory and is configured to execute the program stored in the memory to implement the steps in the control method of the all-vanadium redox flow battery energy storage system according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, For storing a computer-readable program or instruction, and when the program or instruction is executed by a processor, it can implement the steps in the control method of the all-vanadium redox flow battery energy storage system according to any one of claims 1 to 7 above.

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