Flow battery energy storage system for improving consistency between modules and equalization method

Abstract

The invention discloses a flow battery energy storage system capable of improving consistency between modules and a balancing method, and belongs to the technical field of flow energy storage. The flow battery energy storage system for improving the consistency between the modules comprises at least two energy storage modules, each energy storage module comprises an energy storage electric pile, the energy storage electric pile is connected with a positive storage tank and a negative storage tank, the positive storage tank is connected with the negative storage tank, and a power supply / load is connected with the electric piles in the energy storage modules; the flow battery energy storage system further comprises a flow battery management system and a controller used for controlling the flow battery energy storage system. The flow battery energy storage system capable of improving the consistency between the modules and the equalization method are suitable for the field of flow energy storage, SOC equalization and voltage equalization between the modules of the flow energy storage system can be realized, and the consistency of the flow energy storage system can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid flow energy storage, and in particular to a liquid flow battery energy storage system and a balancing method for improving consistency between modules. Background Art

[0002] With the development of science and technology, population growth and the progress of civilization, human demand for energy is gradually increasing. In order to meet the energy demand, the development and application of new energy such as wind energy and solar energy are crucial. However, due to factors such as wind speed, light intensity, and time uncertainty, the output power of wind power and photovoltaics is unstable. Direct grid connection may impact the power grid, affecting the quality and safety of electricity use. The application of energy storage technology can effectively solve the above problems, and at the same time, it also plays a role in peak shaving, optimizing power dispatch, and flexibly configuring power, fully improving the utilization rate of power. Liquid flow batteries have shown strong competitiveness in the field of energy storage with their advantages of high safety, long service life, rich resources, no pollution, convenient expansion, and low cost. It is the main route in the field of long-term energy storage. At present, all-vanadium, iron-chromium, zinc-bromine and other liquid flow batteries have been commercialized, proving the practicality and reliability of liquid flow batteries in long-term energy storage. Liquid flow battery energy storage is gradually expanding in scale and capacity in industrial engineering applications.

[0003] In engineering applications, in order to improve the capacity, voltage level and system efficiency, the liquid flow battery energy storage system usually includes multiple energy storage modules. Each energy storage module contains a power unit and a capacity unit. The power unit and the capacity unit are connected by a pipeline to achieve liquid communication, and the electrolyte circulates between the capacity unit and the power unit through the pipeline. The power unit of each module can be connected to the power supply or load in series, parallel or series-parallel mixed circuits. The most commonly used circuit connection scheme is the series-parallel mixed circuit connection scheme. The power unit of the liquid flow battery is generally assembled into a single cell by fasteners from various components, and then a filter press is used to assemble several single cells in series into a stack. Due to the limitations of the manufacturing process, material and structure, there are differences between the single cells. After being assembled into a stack, the differences between the stacks are still large, resulting in large differences in the voltage of each stack during the charging and discharging process. In order to ensure the safety and life of the energy storage system, it is generally set that when one battery stack reaches the cut-off condition during the charging and discharging process, the other battery stacks in series with it or even all the battery stacks in the system will stop charging and discharging at the same time even if they have not reached the cut-off condition. When charging and discharging are stopped, the battery stack voltage difference is large and the system SOC difference is large, which will lead to further increase in the SOC difference of each module in the system and the voltage difference of each battery stack, reducing the system efficiency. At the same time, the differences between the modules of the liquid flow energy storage system, such as differences in liquid filling volume, temperature, flow rate, pressure, liquid level migration, hydrogen evolution, leakage and other problems will also lead to large differences in the SOC of each module.

[0004] Existing flow battery balancing methods mainly use the following technical routes to solve the inconsistency problem of flow battery energy storage systems: using energy-consuming elements to consume the energy of higher energy units at the battery stack level; transferring the energy of higher energy units to lower energy units at the battery stack level; individually charging and discharging energy units with large energy differences at the battery stack level; adjusting the process system characteristics of energy units with large energy differences at the process system level; and adjusting the electrolyte ion concentration of each energy unit at the reactant ion concentration level.

[0005] The consistency of the liquid flow energy storage system is jointly affected by the differences in the electrolyte states of each module and the differences in the process system. Although the existing mixed liquid balancing method can make the electrolyte states of each module relatively consistent after each mixed liquid balancing, the electrolyte state after mixing cannot offset the differences in the process systems of each module, and the speed of consistency decline cannot be reduced after each balancing. In addition, the mixed liquid balancing method requires mixing operations on all electrolytes, so the balancing time is long, the energy consumption during the balancing process is large, and the capacity loss is large. Summary of the invention

[0006] The object of the present invention is to provide a method for solving the technical problem of SOC differences and voltage differences between modules of a liquid flow battery energy storage system in the prior art.

[0007] To achieve the above-mentioned object, an embodiment of the present invention provides a liquid flow battery energy storage system for improving consistency between modules, including a power supply / load, the power supply / load is connected to at least two energy storage modules, each energy storage module includes an energy storage stack, and the two ends of the energy storage stack are connected to a positive electrode storage tank and a negative electrode storage tank, and the positive electrode storage tank is connected to the negative electrode storage tank;

[0008] The liquid flow battery energy storage system also includes a liquid flow battery management system and a controller for controlling the liquid flow battery energy storage system.

[0009] In one of the preferred solutions of the present invention, each energy storage module is provided with a consistency evaluation index detection device, and the consistency evaluation index detection device is used to detect the consistency evaluation index of the energy storage module.

[0010] In one of the preferred solutions of the present invention, the consistency evaluation index includes at least one of the total voltage of the battery stack in the module, the maximum voltage of the battery stack in the module, the module SOC and the module OCV.

[0011] In one of the preferred solutions of the present invention, the positive electrode storage tank is connected to a positive electrode pump, and the negative electrode storage tank is connected to a negative electrode pump.

[0012] In one of the preferred solutions of the present invention, a liquid communication pipeline and a gas communication pipeline are provided between the positive electrode storage tank and the negative electrode storage tank.

[0013] In one of the preferred solutions of the present invention, a first valve is provided on the liquid communication pipeline, and a second valve is provided on the gas communication pipeline.

[0014] In one of the preferred solutions of the present invention, the initial composition and state of the electrolyte in the positive electrode storage tank and the negative electrode storage tank are consistent.

[0015] In one of the preferred solutions of the present invention, both the positive electrode storage tank and the negative electrode storage tank are provided with a liquid level detection device.

[0016] In one of the preferred solutions of the present invention, a conversion module is connected to the power supply / load.

[0017] In one of the preferred solutions of the present invention, the conversion module includes a bidirectional energy storage inverter, the bidirectional energy storage inverter is connected to a bidirectional DC converter, and the bidirectional DC converter is connected to the energy storage stack.

[0018] The present invention also discloses a balancing method for improving consistency between modules, which is based on the above-mentioned liquid flow battery energy storage system for improving consistency between modules, and includes the following steps:

[0019] The controller obtains the consistency evaluation index of each energy storage module, and controls the electrolyte transport between the positive electrode storage tank and the negative electrode storage tank in the energy storage module according to the obtained consistency evaluation index, thereby changing the SOC of the energy storage module or the total voltage of each battery stack in the module, thereby improving the consistency between the various energy storage modules.

[0020] In one of the preferred solutions of the present invention, the balancing method comprises the following steps:

[0021] The consistency evaluation index detection device detects the consistency evaluation index of each energy storage module;

[0022] The controller obtains the consistency evaluation index of each energy storage module;

[0023] The controller adjusts the consistency between the energy storage modules according to the obtained consistency evaluation index.

[0024] In one of the preferred solutions of the present invention, the controller needs to determine whether a balancing operation is required before adjusting the consistency between the energy storage modules.

[0025] One of the preferred solutions of the present invention is that the controller adjusts the consistency between each energy storage module according to the obtained consistency evaluation index, including: the controller realizes the electrolyte transportation between the positive electrode storage tank and the negative electrode storage tank in the energy storage system by controlling the first valve on the liquid communication pipeline, the flow rate of the positive electrode pump and the flow rate of the negative electrode pump in the energy storage system.

[0026] One of the preferred schemes of the present invention is that the controller adjusts the consistency between each energy storage module according to the obtained consistency evaluation index, including: when the energy storage module is in a hot standby state where charging or no charging or discharging is performed before charging, the controller changes the SOC of the energy storage module or the total voltage of each battery stack in the module by transferring the electrolyte in the negative electrode storage tank in the energy storage module to the positive electrode storage tank, thereby improving the consistency between each energy storage module.

[0027] One of the preferred schemes of the present invention is that the controller adjusts the consistency between each energy storage module according to the obtained consistency evaluation index, including: when the energy storage module is in a hot standby state where charging and discharging are not performed before discharging, the controller changes the SOC of the energy storage module or the total voltage of each battery stack in the module by transferring the electrolyte in the positive electrode storage tank in the energy storage module to the negative electrode storage tank, thereby improving the consistency between each energy storage module.

[0028] In summary, the beneficial effects of the present invention are:

[0029] 1. The liquid flow battery energy storage system and balancing method for improving consistency between modules of the present invention determine the energy storage modules with poor consistency by detecting the total voltage and SOC of each energy storage module, and perform balancing operations on the energy storage modules with poor consistency: by controlling the first valve on the liquid connecting pipeline between the positive electrode storage tank and the negative electrode storage tank in the energy storage module and the positive electrode pump and the negative electrode pump, the electrolyte transportation between the positive electrode storage tank and the negative electrode storage tank in the energy storage module is realized, thereby changing the electrolyte ion concentration in the positive electrode storage tank and the negative electrode storage tank, which can effectively balance the voltage and SOC between the modules in the liquid flow battery energy storage system, and achieve the purpose of improving the consistency of the modules in the liquid flow battery energy storage system. The system has the technical characteristics of real-time, rapid, low cost, simple structure, easy implementation, and convenient operation.

[0030] 2. The liquid flow battery energy storage system and balancing method for improving consistency between modules of the present invention are applicable to the field of liquid flow energy storage, and can achieve SOC balance and voltage balance between modules of the liquid flow energy storage system, and can effectively improve the consistency of the liquid flow energy storage system.

[0031] 3. The flow battery energy storage system and balancing method for improving consistency between modules of the present invention changes the concentration of reactant ions in the positive and negative storage tanks by transferring electrolyte between the positive and negative storage tanks in the energy storage modules, thereby balancing the voltage and SOC between the energy storage modules.

[0032] 4. The balancing method for improving the consistency between modules of the present invention directly takes the reactant ion concentration of the electrolyte in the positive electrode storage tank and the negative electrode storage tank as the balancing target, and the power consumption and capacity loss of the balancing process are low; compared with the existing mutual mixing balancing method, the present invention only balances the modules that are judged to have poor consistency each time, with less operation volume and corresponding less energy and capacity loss; although the existing mutual mixing balancing method can make the electrolyte state in each storage tank completely consistent, the electrolyte state does not match the differences in the process systems of each module, and the differences in the process systems will again lead to reduced consistency between the modules. Compared with complete mixing that only improves the electrolyte consistency, the balancing method of the present invention pays more attention to the overall consistency of the system, rather than blindly making the electrolyte state completely the same. After balancing, the electrolyte state will match the differences in the process systems of each module, ultimately improving the consistency of the entire liquid flow energy storage system.

[0033] 5. The consistency between energy storage modules after each balancing operation of the present invention is better than the consistency between energy storage modules after the previous balancing operation, which can reduce the operation time and operation power consumption of the next balancing operation. For liquid flow energy storage systems, especially large-scale long-term energy storage systems, from a macroscopic perspective of long-term operation, the present invention has particularly obvious effects of improving the consistency between modules of the liquid flow energy storage system, reducing the power consumption of balancing operation, and reducing capacity loss.

[0034] 6. The liquid flow battery energy storage system and balancing method for improving inter-module consistency of the present invention have simple principles and structures, are low-cost and easy to implement, and utilize the liquid level difference generated by liquid level migration during charging and discharging to effectively reduce power consumption during the balancing process. There are few existing liquid flow energy storage systems that perform balancing methods at the level of reactant ion concentration. The present invention provides a new idea and solution for balancing liquid flow energy storage systems, and has broad application and research and development prospects in the field of liquid flow energy storage, especially in the field of large-scale, large-capacity liquid flow energy storage that operates for a long time.

[0035] 7. Compared with the existing mixed liquid balancing method, the balancing method of the present invention can not only balance the current state of inconsistent energy storage modules, but also change the capacity of inconsistent energy storage modules, compensate for the differences in process systems, and reduce the energy consumption of the next balancing. It has the advantages of obvious long-term operation advantages, shorter balancing time, less energy consumption during the balancing process, and less capacity loss.

[0036] Other features and advantages of the present invention will be described in the following description, and part of them will become obvious from the description, or will be understood by implementing the present invention. The purpose and other advantages of the present invention can be described by the effects described in the description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A schematic diagram of a flow battery energy storage system for improving inter-module consistency according to the present invention;

[0038] Figure 2 A flow chart of a balancing method for improving consistency among modules according to the present invention;

[0039] Figure 3 This is a schematic diagram of the structure of the liquid flow battery energy storage system in Example 1 of the present invention;

[0040] Figure 4 Schematic diagram of the flow of the balancing method in Embodiment 1 of the present invention;

[0041] Figure 5 Schematic diagram of the flow of the equalization method in Embodiment 2 of the present invention taking the case before discharge as an example.

[0042] Among them, 1-power supply / load, 2-bidirectional energy storage inverter, 3-bidirectional DC converter, 4-energy storage stack, 5-liquid connecting pipeline, 6-first valve, 7-second valve, 8-gas connecting pipeline, 9-positive electrode storage tank, 10-positive electrode pump, 11-negative electrode pump, 12-negative electrode storage tank, 13-first positive electrode pump, 14-second positive electrode pump, 15-first negative electrode pump, 16-second negative electrode pump. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] The present invention provides a flow battery energy storage system that improves the consistency between modules, such as Figure 1 As shown, it includes a power supply / load 1, which is connected to at least two energy storage modules. Each energy storage module includes an energy storage stack 4, and the energy storage stack 4 is composed of multiple stacks connected in series, parallel, or in a series-parallel mixed manner through wires.

[0045] The two ends of the energy storage stack 4 are respectively connected to the positive electrode storage tank 9 and the negative electrode storage tank 12. The positive electrode storage tank 9 is connected to the negative electrode storage tank 12 through a pipeline. The initial composition and state of the electrolyte stored in the positive electrode storage tank 9 and the negative electrode storage tank 12 are exactly the same. The positive electrode storage tank 9 is connected to the positive electrode pump 10, and the negative electrode storage tank 12 is connected to the negative electrode pump 11. The electrolyte in the positive electrode storage tank 9 and the negative electrode storage tank 12 enters each energy storage stack 4 through the pipeline through the positive electrode pump 10 and the negative electrode pump 11. Each energy storage stack 4 is connected in liquid circuit in series or in parallel through the pipeline, and each energy storage stack 4 has a valve at the liquid inlet and outlet.

[0046] The liquid flow battery energy storage system also includes a liquid flow battery management system for monitoring the battery status of the liquid flow battery energy storage system and a controller for controlling the liquid flow battery energy storage system.

[0047] Each energy storage module is provided with a consistency evaluation index detection device, which is used to detect the consistency evaluation index of the energy storage module. The consistency evaluation index includes at least one of the total voltage of the battery stack in the module, the maximum voltage of the battery stack in the module, the module SOC (state of charge, also known as remaining capacity) and the module OCV (open circuit voltage). The consistency evaluation index detection device transmits the consistency evaluation index of each energy storage module measured in real time to the above-mentioned controller in real time through the communication module. The controller obtains the transmitted consistency evaluation index, processes the obtained consistency evaluation index, and then adjusts the consistency between each energy storage module according to the processed data.

[0048] A liquid communication pipeline 5 and a gas communication pipeline 8 are also provided between the positive electrode storage tank 9 and the negative electrode storage tank 12. The liquid communication pipeline 5 is provided with a first valve 6, and the first valve 6 is used to control the opening and closing of the liquid communication pipeline 5. The gas communication pipeline 8 is provided with a second valve 7, and the gas communication pipeline 8 is used to realize gas communication between the positive electrode storage tank 9 and the negative electrode storage tank 12.

[0049] Liquid level detection devices are provided on both the positive electrode storage tank 9 and the negative electrode storage tank 12. The liquid level detection devices are used to detect the electrolyte liquid levels of the positive electrode storage tank 9 and the negative electrode storage tank 12 in real time, and the liquid level detection devices transmit the liquid level data obtained by real-time detection to the above-mentioned controller through the communication module. The controller obtains the transmitted liquid level data and calculates the liquid level difference between the positive electrode storage tank 9 and the negative electrode storage tank 12 of each energy storage module.

[0050] The power supply / load 1 is also connected to a conversion module, which includes a bidirectional energy storage inverter 2, and the bidirectional energy storage inverter 2 is connected to a bidirectional DC converter 3. The power supply / load 1 is cascaded with the bidirectional DC converter 3 through the bidirectional energy storage inverter 2, and the bidirectional DC converter 3 is connected to the energy storage stack 4.

[0051] Working process: The consistency evaluation index detection device detects the consistency evaluation index of each energy storage module, the controller obtains the consistency evaluation detection index of each energy storage module, and judges whether the consistency evaluation index of a certain energy storage module is greatly different from that of other energy storage modules based on the obtained consistency evaluation index. When the consistency evaluation index of a certain energy storage module is greatly different from that of other energy storage modules, the controller controls the first valve 6 on the liquid connecting pipe 5 in the energy storage system, the flow rate of the positive electrode pump 10 and the flow rate of the negative electrode pump 11 to realize the electrolyte transportation between the positive electrode storage tank 9 and the negative electrode storage tank 12 in the energy storage system, thereby improving the consistency between the various energy storage modules.

[0052] The present invention also discloses a balancing method for improving the consistency between modules, which is based on the above-mentioned flow battery energy storage system for improving the consistency between modules, and includes the following steps: a controller obtains the consistency evaluation index of each energy storage module, and controls the electrolyte delivery between the positive electrode storage tank 9 and the negative electrode storage tank 12 in the energy storage module according to the obtained consistency evaluation index, thereby improving the consistency between each energy storage module; specifically, as Figure 2 As shown, the equalization method includes the following steps:

[0053] Step (1): a consistency evaluation index detection device detects the consistency evaluation index of each energy storage module; specifically, each energy storage module is provided with a consistency evaluation index detection device, the consistency evaluation index detection device detects the consistency evaluation index of each energy storage module in real time, and transmits the real-time detected consistency evaluation index to the controller through the communication module; wherein the consistency evaluation index includes at least one of the total voltage of the battery stack in the module, the maximum voltage of the battery stack in the module, the module SOC and the module OCV;

[0054] Step (2): the controller obtains the consistency evaluation index of each energy storage module; specifically, the controller obtains the consistency evaluation index of each energy storage module, and calculates the obtained consistency evaluation index to obtain the average value of the consistency evaluation index of each energy storage module;

[0055] Step (3): The controller adjusts the consistency between each energy storage module according to the obtained consistency evaluation index; specifically, the controller determines whether the consistency evaluation index of a certain energy storage module is significantly different from that of other energy storage modules according to the obtained consistency evaluation index. When the consistency evaluation index of a certain energy storage module is significantly different from that of other energy storage modules, it is determined that a balancing operation is required. The balancing operation is: by controlling the first valve 6, the positive electrode pump 10 and the negative electrode pump 11, including opening the first valve 6 on the liquid connecting pipe 5, increasing the flow of the positive electrode pump 10 and the negative electrode pump 11, etc., the electrolyte in the positive electrode storage tank 9 of the energy storage module is transported to the negative electrode storage tank 12 through the pipeline, or the electrolyte in the negative electrode storage tank 12 in the energy storage module is transported to the positive electrode Storage tank 9, this is operation one; after continuous operation for a set time T, if it is detected that the consistency evaluation index of the energy storage module is slightly different from that of other energy storage modules or the liquid level difference between the positive storage tank 9 and the negative storage tank 12 of the energy storage module is greater than the set value, then through the control of the first valve 6, the positive pump 10 and the negative pump 11, including closing the first valve 6 on the liquid communication pipeline 5, reducing the pump flow of the positive pump 10 and the negative pump 11, etc., the electrolyte transport between the positive storage tank 9 and the negative storage tank 12 in the energy storage module is stopped, and the balancing operation ends; if it is detected that the consistency evaluation index of the energy storage module is still significantly different from that of other energy storage modules and the liquid level difference between the positive storage tank 9 and the negative storage tank 12 of the energy storage module is less than the set value, then the operation one is repeated;

[0056] When the energy storage module is in a hot standby state where charging or charging is not performed before charging, for an energy storage module whose highest stack voltage or total stack voltage or module SOC is significantly higher than that of other modules, the electrolyte in the negative electrode storage tank 12 of the energy storage module is transported to the positive electrode storage tank 9 through a pipeline, thereby reducing the concentration of the positive electrode product in the positive electrode storage tank 9. According to the Nernst equation, the SOC and stack voltage of the energy storage module can be effectively reduced, thereby delaying the energy storage module from reaching the charging cut-off condition, so that the states of each energy storage module when charging is stopped are close; at the same time, during the charging process, hydrogen ions migrate to the negative electrode, the positive electrode liquid level decreases, the negative electrode liquid level increases, and the hydraulic pressure of the negative electrode storage tank 12 on the positive electrode storage tank 9 increases, so the pump consumption of the electrolyte transported from the negative electrode storage tank 12 to the positive electrode storage tank 9 in this process is relatively low;

[0057] When the energy storage module is in a hot standby state where the lowest stack voltage or the total stack voltage or the module SOC is significantly lower than that of other modules, the electrolyte in the positive electrode storage tank 9 of the energy storage module is transported to the negative electrode storage tank 12 through a pipeline, thereby reducing the concentration of the negative electrode product in the negative electrode storage tank 12. According to the Nernst equation, the SOC and the stack voltage of the energy storage module can be effectively improved, thereby delaying the energy storage module from reaching the discharge cut-off condition, so that the states of each energy storage module when stopping discharge are close; at the same time, during the discharge process, hydrogen ions migrate to the positive electrode, the positive electrode liquid level increases, the negative electrode liquid level decreases, and the hydraulic pressure of the positive electrode storage tank 9 to the negative electrode storage tank 12 increases, so the pump consumption of the electrolyte transported from the positive electrode storage tank 9 to the negative electrode storage tank 12 in this process is relatively low.

[0058] The initial composition and state of the electrolyte in each positive electrode storage tank 9 and negative electrode storage tank 12 are completely the same, and the electrolyte between the positive electrode storage tank 9 and the negative electrode storage tank 12 will not produce other products.

[0059] The basis for selecting the consistency evaluation index is: in order to prevent a battery stack from overcharging / discharging during the charging / discharging process, it is usually set that as long as one battery stack reaches the charging / discharging cut-off voltage, the battery stacks on the circuit branch where the battery stack is located or all the battery stacks on the entire system will stop charging / discharging, that is, the battery stack with the highest / lowest voltage determines the cut-off of charging / discharging, so during the charging / discharging process, the battery stack voltage or the total voltage of all battery stacks in the module is selected as the consistency evaluation index; during the charging / discharging process, if the highest / lowest battery stack voltage in a module or the total voltage of all battery stacks in a module is significantly higher / lower than other modules, it is judged that the module needs to be balanced; when in the hot standby state without charging / discharging, the module SOC can more intuitively reflect the consistency of each module, so when in the hot standby state without charging / discharging, the module SOC is selected as the consistency evaluation index; before charging / discharging, if the SOC of a module is significantly higher / lower than other modules, it is judged that the module needs to be balanced.

[0060] Example 1

[0061] A flow battery energy storage system with improved consistency between modules, such as Figure 3 As shown, when each energy storage module of the flow battery is in a charging / discharging state, when it is detected that the real-time total voltage Vi of module i is greater than / less than the set voltage value V1 / V2, the difference Vi-Va / Va-Vi between the real-time total voltage Vi of the module and the real-time total voltage average value Va of each module is calculated. If Vi-Va / Va-Vi is greater than the voltage difference set value Vd, it is determined that the inconsistency of module i is large and a balancing operation is required. The balancing operation is: open the gas communication pipeline 8 and the first valve 6 on the liquid communication pipeline 5 between the positive electrode storage tank 9 and the negative electrode storage tank 12 of module i, start the first negative electrode pump 15 / the second positive electrode pump 14, and transport electrolyte from the negative electrode storage tank 12 to the positive electrode storage tank 9 / from the positive electrode storage tank 9 to the negative electrode storage tank 12. After continuous operation for a set time T, if the voltage difference Vi-Va / Va-Vi is greater than Vd and the liquid level difference L between the positive electrode storage tank 9 and the negative electrode storage tank 12 is L=L 正 -L 负 / L=L 负 -L 正 If the voltage difference Vi-Va / Va-Vi is less than or equal to the set value L1, the electrolyte will continue to be transported from the negative electrode storage tank 12 to the positive electrode storage tank 9. After the set time T, the judgment will be repeated again until the voltage difference Vi-Va / Va-Vi is less than or equal to Vd or the liquid level difference L between the positive electrode storage tank 9 and the negative electrode storage tank 12 is L = L 正 -L 负 / L=L 负 -L 正 If the voltage is greater than the set value L1, the first cathode pump 15 / the second cathode pump 14 is stopped, the first valve 6 on the liquid communication pipeline 5 is closed, and the real-time total voltage of the module is continuously detected. When the inconsistency of the module i is large, the balancing operation of this embodiment is performed again. The whole balancing method is as follows: Figure 4 shown.

[0062] Example 2

[0063] When each energy storage module of the flow battery is in a hot standby state before charging / discharging, the real-time SOC of each energy storage module is detected, and the SOC of module i is recorded as Si. If the difference Si-Sa / Sa-Si between Si and the average value Sa of the SOC of each module is greater than the set value Sd, it is determined that the inconsistency of module i is large and a balancing operation is required. The balancing operation is: open the gas communication pipeline 8 and the first valve 6 on the liquid communication pipeline 5 between the positive electrode storage tank 9 and the negative electrode storage tank 12 of module i, increase the flow rate of the negative electrode pump 11 / positive electrode pump 10, and transport electrolyte from the negative electrode storage tank 12 / positive electrode storage tank 9 to the positive electrode storage tank 9 / negative electrode storage tank 12 through the energy storage stack 4. After the set time T, if Si-Sa / Sa-Si is greater than Sd and the liquid level difference L between the positive electrode storage tank 9 and the negative electrode storage tank 12 is L=L 正 -L 负 / L=L 负 -L 正 If the electrolyte is less than or equal to the set value L1, the electrolyte will continue to be transported from the negative electrode storage tank 12 / positive electrode storage tank 9 to the positive electrode storage tank 9 / negative electrode storage tank 12 through the energy storage stack 4. After the set time T, the cycle is repeated until Si-Sa / Sa-Si is less than or equal to Sd or the liquid level difference L between the positive electrode storage tank 9 and the negative electrode storage tank 12 is L=L 正 -L 负 / L=L 负 -L 正 If the flow rate of the negative electrode pump 11 / positive electrode pump 10 is greater than the set value L1, the flow rate of the negative electrode pump 11 / positive electrode pump 10 is restored to the original flow rate, the first valve 6 on the liquid connecting pipe 5 is closed, and the real-time SOC of the detection module is continuously cycled until the inconsistency of the module i is large, and the balancing operation of this embodiment is performed again; taking the pre-discharge as an example, the whole balancing process is as follows Figure 5 shown.

[0064] In summary, the liquid flow battery energy storage system and balancing method for improving consistency between modules of the present invention realize the electrolyte transportation between the positive electrode storage tank 9 and the negative electrode storage tank 12 in the energy storage module, thereby changing the electrolyte ion concentration in the positive electrode storage tank 9 or the negative electrode storage tank 12, and then changing the total voltage or SOC of each battery stack of the module, which can effectively balance the battery stack voltage and SOC between each module in the liquid flow battery energy storage system, and achieve the purpose of improving the consistency of each module in the liquid flow battery energy storage system.

[0065] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary engineering and technical personnel in the field should all fall within the protection scope of the claims of the present invention.

Claims

1. A flow battery energy storage system for improving inter-module consistency, characterized in that: It includes a power supply / load, the power supply / load is connected to at least two energy storage modules, each of the energy storage modules includes an energy storage stack, and the two ends of the energy storage stack are connected to a positive electrode storage tank and a negative electrode storage tank, and the positive electrode storage tank is connected to the negative electrode storage tank; The liquid flow battery energy storage system also includes a liquid flow battery management system and a controller for controlling the liquid flow battery energy storage system.

2. A flow battery energy storage system for improving inter-module consistency as claimed in claim 1, characterized in that: Each of the energy storage modules is provided with a consistency evaluation index detection device, and the consistency evaluation index detection device is used to detect the consistency evaluation index of the energy storage module.

3. A flow battery energy storage system for improving inter-module consistency as claimed in claim 2, characterized in that: The consistency evaluation index includes at least one of the total voltage of the battery stack in the module, the maximum voltage of the battery stack in the module, the module SOC and the module OCV.

4. A flow battery energy storage system for improving inter-module consistency as claimed in claim 1, characterized in that: The positive electrode storage tank is connected to a positive electrode pump, and the negative electrode storage tank is connected to a negative electrode pump.

5. A flow battery energy storage system for improving inter-module consistency as claimed in claim 1, characterized in that: A liquid communication pipeline and a gas communication pipeline are arranged between the positive electrode storage tank and the negative electrode storage tank.

6. A flow battery energy storage system for improving inter-module consistency as claimed in claim 5, characterized in that: The liquid communication pipeline is provided with a first valve, and the gas communication pipeline is provided with a second valve.

7. A flow battery energy storage system for improving inter-module consistency as claimed in claim 1, characterized in that: The initial composition and state of the electrolyte in the positive electrode storage tank and the negative electrode storage tank are consistent.

8. A flow battery energy storage system for improving inter-module consistency as claimed in claim 1, characterized in that: The positive electrode storage tank and the negative electrode storage tank are both provided with liquid level detection devices.

9. A flow battery energy storage system for improving inter-module consistency as claimed in claim 1, characterized in that: The power source / load is connected with a conversion module.

10. A flow battery energy storage system for improving inter-module consistency according to claim 8, characterized in that: The conversion module includes a bidirectional energy storage converter, the bidirectional energy storage converter is connected to a bidirectional DC converter, and the bidirectional DC converter is connected to an energy storage stack.

11. A balancing method for improving inter-module consistency, implemented based on a flow battery energy storage system for improving inter-module consistency according to any one of claims 1 to 10, characterized in that: The following steps are involved: The controller obtains the consistency evaluation index of each energy storage module, and controls the electrolyte transportation between the positive electrode storage tank and the negative electrode storage tank in the energy storage module according to the obtained consistency evaluation index, thereby improving the consistency between the various energy storage modules.

12. A method for improving inter-module consistency according to claim 11, characterized in that: The balancing method comprises the following steps: The consistency evaluation index detection device detects the consistency evaluation index of each energy storage module; The controller obtains the consistency evaluation index of each energy storage module; The controller adjusts the consistency between the energy storage modules according to the obtained consistency evaluation index.

13. A method for improving inter-module consistency according to claim 12, characterized in that: The controller needs to determine whether a balancing operation is required before adjusting the consistency between the energy storage modules.

14. A method for improving inter-module consistency according to claim 12, characterized in that: The controller adjusts the consistency between the energy storage modules according to the obtained consistency evaluation index, including: the controller realizes the electrolyte transportation between the positive electrode storage tank and the negative electrode storage tank in the energy storage system by controlling the first valve on the liquid communication pipeline, the flow rate of the positive electrode pump and the flow rate of the negative electrode pump in the energy storage system.

15. The method for improving the consistency between modules as claimed in claim 12, characterized in that: The controller adjusts the consistency between the energy storage modules according to the obtained consistency evaluation index, including: when the energy storage module is in a hot standby state where charging or no charging or discharging is performed before charging, the controller improves the consistency between the energy storage modules by transferring the electrolyte in the negative electrode storage tank of the energy storage module to the positive electrode storage tank.

16. A method for improving inter-module consistency according to claim 12, characterized in that: The controller adjusts the consistency between the various energy storage modules according to the obtained consistency evaluation index, including: when the energy storage module is in a hot standby state where charging and discharging are not performed before discharging, the controller improves the consistency between the various energy storage modules by transferring the electrolyte in the positive electrode storage tank in the energy storage module to the negative electrode storage tank.

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