SOC balance recovery control system for large-scale all-vanadium redox flow energy storage power station

Abstract

The utility model relates to the technical field of vanadium redox flow batteries, in particular to a large all-vanadium redox flow energy storage power station SOC balance recovery control system which comprises at least two redox flow battery modules, an energy storage converter and a battery management system. The flow battery module comprises an electric pile group, a positive electrode electrolyte storage tank, a negative electrode electrolyte storage tank, a variable frequency pump and SOC sensors connected in parallel to two ends of the electric pile group. During working, the SOC of each battery module is evaluated in real time through a battery management system (BMS) control system; when the BMS system monitors that the SOC difference value between the electric pile groups is too large, the SOC difference value is generally 5%. The BMS system adjusts the flow of the electrolyte flowing through the galvanic pile groups by controlling the frequency of the variable frequency pumps of the galvanic pile groups, so that the internal resistance of the galvanic pile groups is adjusted, and the charging and discharging power on each galvanic pile group is adjusted.

Description

Technical Field

[0001] The present application relates to the field of vanadium liquid flow batteries, and in particular to a SOC balance recovery control system for a large-scale all-vanadium liquid flow energy storage power station. Background Art

[0002] Liquid flow batteries are a type of electrochemical energy storage system. The electrolyte, the energy storage active material for the positive and negative electrodes, is stored in external tanks. This electrolyte is pumped into the battery stack via an electrolyte circulation pump and pipelines, where it is charged and discharged at the electrodes. Flow batteries feature independent output power and energy storage capacity, deep discharge capability, no safety hazards, and a long lifespan. Currently, various liquid flow battery systems have been developed, with all-vanadium liquid flow battery technology being the primary technology used in engineering and industrial energy storage power stations exceeding megawatts.

[0003] A flow battery system consists of multiple stacks connected in series and parallel. During operation, the electrolyte continuously circulates between the stacks and the electrolyte storage tank. However, performance varies between stacks. After prolonged charging and discharging, this can lead to deviations in the charge and discharge states of the flow battery modules, affecting the charge and discharge balance between the modules. This increases the SOC differences between the modules and reduces the overall charge and discharge capacity of the all-vanadium flow battery system.

[0004] The traditional SOC balancing method uses a circulating mixing method. When the system is shut down, the positive electrolyte of different stack groups is circulated and mixed through the pipeline. The negative electrolyte is also circulated and mixed through the pipeline. This method has complex pipelines and requires shutdown for SOC balancing. Another method is to use a discharge method. That is, when the system is shut down, the SOC of the stack group with a high SOC is reduced by external discharge, and the stack group with a lower SOC is charged, thereby balancing the SOC between the unconnected stack groups. However, this method is cumbersome and has low accuracy. Utility Model Content

[0005] In response to the shortcomings of the existing technology, the utility model provides a large-scale all-vanadium liquid flow energy storage power station SOC balance recovery control system, which can simply and effectively adjust the charging and discharging conditions of each module, reduce the SOC differences of the battery modules, and solve the above technical problems.

[0006] The SOC balance recovery control system of a large-scale all-vanadium liquid flow energy storage power station provided in this application adopts the following technical solutions:

[0007] A large-scale all-vanadium liquid flow energy storage power station SOC balance recovery control system includes at least two liquid flow battery modules, an energy storage converter and a battery management system; the liquid flow battery module includes a stack group, a positive electrolyte storage tank, and a negative electrolyte storage tank; a closed loop is formed between the stack group and the positive electrolyte storage tank, and a closed loop is formed between the stack group and the negative electrolyte storage tank; the liquid flow battery module also includes two variable frequency pumps, one of which is arranged between the positive electrolyte storage tank and the stack group, and the other is arranged between the stack group and the negative electrolyte storage tank; the liquid flow battery module also includes an SOC sensor connected in parallel at both ends of the stack group; the battery management system line is connected to the variable frequency pump and the SOC sensor; multiple stack groups and the energy storage converter form a series closed loop.

[0008] Optionally, it also includes a flow rate regulating component arranged between the positive electrode electrolyte storage tank and the variable frequency pump; the flow rate regulating component includes a pipeline b connected to the positive electrode electrolyte storage tank, and a pipeline c connected in series to the pipeline b, the diameter of the pipeline b is larger than the diameter of the pipeline c, and the pipeline c is connected to the variable frequency pump at one end away from the pipeline b.

[0009] Optionally, the flow rate regulating assembly further includes a pipeline a connected to the positive electrode electrolyte storage tank, a three-way valve connected to pipeline a, pipelines b and pipeline c are connected to the three-way valve, pipelines a and pipeline b are connected in parallel, and the diameter of pipeline a is equal to the diameter of pipeline c.

[0010] Optionally, the diameter of pipe b is twice the diameter of pipe c.

[0011] Optionally, the negative electrode electrolyte storage tank and the stack group are provided with a flow rate regulating component.

[0012] Optionally, the three-way valve is connected to a battery management system.

[0013] Optionally, the fuel cell stack group includes a plurality of fuel cell stacks connected in series.

[0014] In summary, this application includes at least one of the following beneficial technical effects:

[0015] The battery management system (BMS) controls the system, evaluating the SOC of each battery module in real time. When the BMS detects a significant SOC difference between stacks, typically 5%, it adjusts the stack's internal resistance and the charge and discharge power applied to each stack by controlling the frequency of the stack's variable frequency pumps to regulate the flow of electrolyte through the stack.

[0016] The utility model can balance the SOC between the unpowered stacks without stopping the machine, without adding any additional electrolyte pipelines or additional charging and discharging equipment.

[0017] When adjusting the SOC, the electrolyte has two flow paths: one is pipe a-pipe c, and the other is pipe b-pipe c. As the pipe diameter decreases, the water flow rate decreases, and the change is very significant. According to the law of conservation of flow, the flow rate in a pipe remains constant over the same time period. Therefore, as the pipe diameter decreases, the water velocity increases, resulting in increased frictional resistance. This increased resistance requires higher pressure to maintain the same water flow rate. Therefore, as the pipe diameter decreases, higher pressure is required to maintain the same water flow rate. If the pressure remains unchanged, the water flow rate decreases. In summary, by selecting two different paths and controlling the power of the variable frequency pump, the electrolyte flow rate entering the stack can be comprehensively adjusted, achieving a wider range of regulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the overall structure of Example 1 of the present application.

[0019] Figure 2 This is a partial structural diagram of Example 2 of the present application.

[0020] Explanation of the accompanying drawings: 1. Water pipe; 2. Electric wire; 3. Bluetooth signal. DETAILED DESCRIPTION

[0021] The following is combined with Figure 1-2 This application is described in further detail.

[0022] Example 1

[0023] The embodiment of the present application discloses a large-scale all-vanadium liquid flow energy storage power station SOC balance recovery control system. Figure 1 A large-scale all-vanadium liquid flow energy storage power station SOC balance recovery control system includes two liquid flow battery modules, a storage converter PCS, and a battery management system BMS.

[0024] Reference Figure 1 The liquid flow battery module includes a stack group, a positive electrode electrolyte storage tank, and a negative electrode electrolyte storage tank; a closed loop is formed between the stack group and the positive electrode electrolyte storage tank, and a closed loop is formed between the stack group and the negative electrode electrolyte storage tank; the above two loops are symmetrically arranged, and the stack group includes a plurality of stacks connected in series; the liquid flow battery module also includes two variable frequency pumps, one of which is arranged between the positive electrode electrolyte storage tank and the stack group, and the other variable frequency pump is arranged between the stack group and the negative electrode electrolyte storage tank; the liquid flow battery module also includes an SOC sensor connected in parallel at both ends of the stack group, and part of the electrolyte in the positive electrode electrolyte storage tank and the negative electrode electrolyte storage tank enters the SOC sensor, and part enters the stack group; the various components of the liquid flow battery module are interconnected through a water pipe 1.

[0025] refer to Figure 1The battery management system BMS is connected to the variable frequency pump and the SOC sensor through wire 2; multiple battery stacks and energy storage converter PCS form a series closed loop, and the battery stacks and energy storage converter PCS are connected through Bluetooth signal 3; the battery management system BMS and energy storage converter PCS are connected through Bluetooth signal 3.

[0026] During operation, the battery management system (BMS) monitors the SOC values ​​of each flow battery module. When the difference between the SOC value of the battery group with the highest SOC (Group A) and the SOC value of the battery group with the lowest SOC (Group B) exceeds a preset value (5%), the control system starts to operate. For example, if the SOC of Group A is 10% and the SOC of Group B is 5%, when the system is fully charged, the SOC of Group A is 100% and the SOC of Group B is 95%.

[0027] After the system is started:

[0028] During charging: While maintaining the same charging power, the frequency of the variable frequency pump in Group A is increased to reduce the internal resistance of the stack, resulting in lower charging power and a reduced charge capacity. The frequency of the variable frequency pump in Group B is reduced to increase the internal resistance of the stack, increasing charging power and a larger charge capacity. When the system is fully charged (maximum SOC = 100%), the SOC of Group A is 100%, and the SOC of Group B is 96%.

[0029] During discharge: While maintaining the same discharge power, the frequency of the variable frequency pump for Group A is reduced, increasing the internal resistance of the stack. This increases the discharge power of Group A and the discharge volume. The frequency of the variable frequency pump for Group B is increased, reducing the internal resistance of the stack, which reduces the discharge power of Group B and the discharge volume. When the system is shut down (minimum SOC = 5%), the SOC of Group A is 8%, and the SOC of Group B is 5%.

[0030] After a period of operation and adjustment, the SOC difference will become smaller and smaller. When the SOC difference falls below the preset value (1%), the frequency of each variable frequency pump group returns to the initial value. This system regulation ends and the system SOC difference is monitored in real time.

[0031] Through this method, the SOC differences between the battery stack groups can be reduced and balanced during operation, solving the problem that the SOC differences between different groups of flow battery modules increase with operating time, resulting in a decline in the performance of the all-vanadium liquid flow battery system, thereby ensuring the system efficiency and economy of the energy storage power station operation.

[0032] Example 2

[0033] refer to Figure 2Example 2 differs from Example 1 in that it further includes two flow rate regulating assemblies, located between the positive electrolyte storage tank and the variable frequency pump, and between the negative electrolyte storage tank and the variable frequency pump, respectively. The variable frequency pump flow rate regulating assembly includes a pipeline b connected to the positive electrolyte storage tank and a pipeline c connected in series with pipeline b. The diameter of variable frequency pump pipeline b is twice the diameter of pipeline c, and the end of variable frequency pump pipeline c away from pipeline b is connected to the variable frequency pump. The variable frequency pump flow rate regulating assembly also includes a pipeline a connected to the positive electrolyte storage tank and a three-way valve connected to pipeline a. Variable frequency pump pipelines b and c are connected to the variable frequency pump three-way valve. Variable frequency pump pipelines a and b are connected in parallel, and the diameter of variable frequency pump pipeline a is equal to the diameter of pipeline c. The variable frequency pump three-way valve is connected to the battery management system (BMS).

[0034] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A large-scale all-vanadium liquid flow energy storage power station SOC balance recovery control system, characterized by: It includes at least two liquid flow battery modules, as well as an energy storage inverter and a battery management system; the liquid flow battery module includes a stack group, a positive electrode electrolyte storage tank, and a negative electrode electrolyte storage tank; a closed loop is formed between the stack group and the positive electrode electrolyte storage tank, and a closed loop is formed between the stack group and the negative electrode electrolyte storage tank; the liquid flow battery module also includes two variable frequency pumps, one variable frequency pump is arranged between the positive electrode electrolyte storage tank and the stack group, and the other variable frequency pump is arranged between the stack group and the negative electrode electrolyte storage tank; the liquid flow battery module also includes an SOC sensor connected in parallel at both ends of the stack group; the battery management system is connected to the variable frequency pump and the SOC sensor; the multiple stack groups and the energy storage inverter form a series closed loop.

2. A large-scale all-vanadium liquid flow energy storage power station SOC balance recovery control system according to claim 1, characterized in that: The device also includes a flow rate regulating component arranged between the positive electrode electrolyte storage tank and the variable frequency pump; the flow rate regulating component includes a pipeline b connected to the positive electrode electrolyte storage tank and a pipeline c connected in series to the pipeline b, the diameter of the pipeline b is larger than the diameter of the pipeline c, and the pipeline c is connected to the variable frequency pump at one end away from the pipeline b.

3. The SOC balance recovery control system of a large-scale all-vanadium liquid flow energy storage power station according to claim 2 is characterized by: The flow rate regulating assembly also includes a pipeline a connected to the positive electrode electrolyte storage tank, a three-way valve connected to the pipeline a, the pipeline b and the pipeline c are connected to the three-way valve, the pipeline a and the pipeline b are connected in parallel, and the diameter of the pipeline a is equal to the diameter of the pipeline c.

4. A large-scale all-vanadium liquid flow energy storage power station SOC balance recovery control system according to claim 3, characterized in that: The diameter of the pipeline b is twice the diameter of the pipeline c.

5. The SOC balance recovery control system of a large-scale all-vanadium liquid flow energy storage power station according to claim 1 is characterized by: The negative electrode electrolyte storage tank and the stack group are provided with a flow rate regulating component.

6. The SOC balance recovery control system of a large-scale all-vanadium liquid flow energy storage power station according to claim 3 is characterized by: The three-way valve is connected to a battery management system.

7. The SOC balance recovery control system for a large-scale all-vanadium liquid flow energy storage power station according to claim 1 is characterized by: The fuel cell stack group includes a plurality of fuel cell stacks connected in series.

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