A flow battery system and a method for recovering residual electricity after discharging a flow battery

Abstract

The application relates to a liquid flow battery system and a method for recycling residual electricity after discharging of a liquid flow battery. The system part mainly comprises a positive electrolyte storage tank, a negative electrolyte storage tank, a power module stack, an electrical module, a residual electricity recycling module and a control system; wherein: the power module stack is connected with the positive electrolyte storage tank and the negative electrolyte storage tank respectively; the electrical module is connected with the power module stack, the residual electricity recycling module and a load respectively, and the electrical module is internally provided with a first contactor and a second contactor; the first contactor is used for controlling the switch between the electrical module and the load; the second contactor is used for controlling the switch between the electrical module and the residual electricity recycling module; and the residual electricity recycling module is connected with the positive electrolyte storage tank and the negative electrolyte storage tank respectively. The application can recycle residual electricity, thereby avoiding energy waste.

Description

Technical Field

[0001] This application relates to the field of flow battery technology, and in particular to a flow battery system and a method for recovering residual electricity after the flow battery has been discharged. Background Technology

[0002] The commercial application of flow battery systems is rapidly developing. During use, because the overall power module of a flow battery is composed of a stack, and the stack itself has a large volume (typically 50-200L), after the flow battery system has discharged, the electrolyte stored in the stack still retains some charge. If this charge is not released, it will self-discharge inside the stack, causing the internal temperature of the stack to rise, which will affect the service life of the stack materials and the performance of the stack itself. For example, in a 100-megawatt project, based on one stack of 100kW, at least 1000 stacks are needed; with a stack volume of 200L, the residual electrolyte volume inside the stack = 1000 * 200L = 200000L = 200m³. Therefore, a large amount of residual electrical energy remains, especially during high SOC (State of Charge) shutdown conditions, where the residual electrical energy is extremely large.

[0003] In response to the above situation, the industry currently employs some existing solutions to consume residual power, such as adding external resistors to consume residual power. However, although this method can release the power inside the fuel cell, it requires a large external load, which increases costs. At the same time, this method releases the internal residual power as heat, which also results in energy waste.

[0004] Therefore, overcoming the problems of increased cost and energy waste when the residual power is consumed in the existing flow battery system is a problem to be solved in this technical field. Summary of the Invention

[0005] To address the aforementioned deficiencies or improvement needs of existing technologies, and to solve the problems of increased costs and energy waste when existing flow battery systems consume residual charge, this application provides a flow battery system and a method for recovering residual charge after discharge. By switching via a contactor, the residual charge inside the battery stack is released, preventing damage to the stack from internal self-discharge. Simultaneously, a residual charge recovery module can be activated to recover the remaining charge inside the stack and recharge it into the electrolyte storage tank. This method eliminates the need for additional loads, saving costs, and also recovers and reuses residual charge, avoiding energy waste.

[0006] The embodiments of this application adopt the following technical solutions:

[0007] In a first aspect, this application provides a flow battery system, including a positive electrode electrolyte storage tank, a negative electrode electrolyte storage tank, a power module stack, an electrical module, a residual energy recovery module, and a control system; wherein:

[0008] The power module stack is connected to the positive electrolyte storage tank and the negative electrolyte storage tank respectively, and a power module circulation pump is provided between the power module stack and the positive electrolyte storage tank and the negative electrolyte storage tank;

[0009] The electrical module is connected to the power module stack, the residual power recovery module, and the load respectively. The electrical module is equipped with a first contactor and a second contactor. The first contactor is used to control the switch between the electrical module and the load, and the second contactor is used to control the switch between the electrical module and the residual power recovery module.

[0010] The residual electricity recovery module is connected to the positive electrolyte storage tank and the negative electrolyte storage tank respectively, and the residual electricity recovery module is equipped with a residual electricity recovery circulation pump connected to the positive electrolyte storage tank and the negative electrolyte storage tank;

[0011] The control system is used to monitor various states of the flow battery system and issue execution commands.

[0012] By adopting the above technical solution, after the flow battery system is shut down, the first contactor between the electrical module and the load can be disconnected, and the second contactor between the electrical module and the residual power recovery module can be closed, connecting the power module stack, the electrical module, and the residual power recovery module. This allows the residual charge in the power module stack to be released into the residual power recovery module, preventing damage to the stack from internal self-discharge. Furthermore, by turning on the residual power recovery circulation pump, the charge recovered by the residual power recovery module can be recharged into the positive and negative electrolyte storage tanks, achieving the purpose of recovering and utilizing residual charge and avoiding energy waste. Moreover, this method does not require additional load, thus saving costs.

[0013] In some embodiments, the electrical module includes a DC / DC module and a PCS module. The DC / DC module is connected to the power module stack, the residual power recovery module, and the PCS module, respectively. The PCS module is connected to the load.

[0014] The first contactor is disposed between the DC / DC module and the PCS module;

[0015] The second contactor is disposed between the DC / DC module and the residual power recovery module.

[0016] By adopting the above technical solution, when the system is discharging normally, the second contactor is open and the first contactor is closed. The electricity released by the power module stack reaches the load after passing through the DC / DC module and the PCS module, completing the discharge operation. After the system stops, the first contactor is opened and the second contactor is closed. The DC / DC module can discharge the power module stack and recover the released electricity into the residual power recovery module.

[0017] In some embodiments, the residual power recovery module includes a residual power recovery stack and a residual power recovery circulation pump, wherein the residual power recovery circulation pump includes a residual power recovery positive electrode circulation pump and a residual power recovery negative electrode circulation pump.

[0018] The residual power recovery stack is connected to the DC / DC module, and the second contactor is disposed between the residual power recovery stack and the DC / DC module;

[0019] The residual electricity recovery stack is connected to the positive electrolyte storage tank and the negative electrolyte storage tank, and the residual electricity recovery positive circulation pump is located between the residual electricity recovery stack and the positive electrolyte storage tank, and the residual electricity recovery negative circulation pump is located between the residual electricity recovery stack and the negative electrolyte storage tank.

[0020] By adopting the above technical solution, the residual power recovery module uses a residual power recovery stack to recover electricity. This residual power recovery stack can be the same as or different from the power module stack, and the overall power of the residual power recovery stack can be appropriately reduced. In addition, the residual power recovery circulation pump of the residual power recovery module includes a residual power recovery positive electrode circulation pump and a residual power recovery negative electrode circulation pump, which can be controlled to connect or disconnect with the positive electrode electrolyte storage tank and the negative electrode electrolyte storage tank, respectively. When connected, the electricity recovered by the residual power recovery stack is recharged into the positive electrode electrolyte storage tank and the negative electrode electrolyte storage tank.

[0021] In some embodiments, both the first contactor and the second contactor are DC contactors.

[0022] By adopting the above technical solution, a DC contactor is set up to match the DC / DC module, and it has the characteristics of long life and suitability for frequent start-stop.

[0023] In some embodiments, the power module circulation pump includes a power module positive electrode circulation pump and a power module negative electrode circulation pump;

[0024] The power module positive electrode circulation pump is located between the power module stack and the positive electrode electrolyte storage tank, and the power module negative electrode circulation pump is located between the power module stack and the negative electrode electrolyte storage tank.

[0025] By adopting the above technical solution, the power module stack is connected to the positive electrolyte storage tank and the negative electrolyte storage tank respectively through the power module positive circulation pump and the power module negative circulation pump. When the power module positive circulation pump and the power module negative circulation pump are closed, the positive electrolyte storage tank and the negative electrolyte storage tank cannot replenish the electrolyte of the power module stack; when the power module positive circulation pump and the power module negative circulation pump are open, the positive electrolyte storage tank and the negative electrolyte storage tank can replenish the electrolyte of the power module stack.

[0026] In some embodiments, the control system includes a detection unit, a first judgment unit, a second judgment unit, a first control unit, a second control unit, a third control unit, and a fourth control unit, wherein:

[0027] The detection unit is used to detect the working status of each component and current and voltage parameters.

[0028] The first judgment unit is used to determine whether the machine is in a shutdown state; the second judgment unit is used to determine whether the current and voltage have reached the protection threshold.

[0029] The first control unit is used to control the state of the first contactor and the second contactor; the second control unit is used to control the working state of the power module circulation pump; the third control unit is used to control the working state of the residual power recovery circulation pump; and the fourth control unit is used to control the start-up, load-bearing and shutdown of the DC / DC module.

[0030] By adopting the above technical solution, the control system monitors various states of the flow battery through the detection unit, determines various conditions through the first and second judgment units, and issues various execution commands through the first, second, third, and fourth control units to realize the automated operation of the entire system.

[0031] Secondly, this application provides a method for recovering residual electricity after discharge from a flow battery, applied to the flow battery system described in the first aspect, comprising:

[0032] Determine if the flow battery system has stopped. If it has stopped, disconnect the first contactor and close the second contactor. At the same time, turn off the power module circulation pump and turn on the residual power recovery circulation pump.

[0033] The control electrical module performs load discharge on the power module stack, recovers the electricity through the residual electricity recovery module, and charges the electrolyte in the positive electrode electrolyte storage tank and the negative electrode electrolyte storage tank;

[0034] Determine whether the voltage and power of the power module stack have reached the protection threshold. If they have, control the electrical module to stop applying load to the power module stack, thus stopping the power module stack from discharging.

[0035] Disconnect the second contactor and shut down the residual electricity recovery circulation pump.

[0036] By adopting the above technical solution, after the flow battery system is shut down, the first contactor between the electrical module and the load can be disconnected, and the second contactor between the electrical module and the residual power recovery module can be closed, connecting the power module stack, the electrical module, and the residual power recovery module. This allows the residual charge in the power module stack to be released into the residual power recovery module, preventing damage to the stack from internal self-discharge. Furthermore, by turning on the residual power recovery circulation pump, the charge recovered by the residual power recovery module can be recharged into the positive and negative electrolyte storage tanks, achieving the purpose of recovering and utilizing residual charge and avoiding energy waste. Moreover, this method does not require additional load, thus saving costs.

[0037] In some embodiments, when determining whether the voltage and power of the power module stack have reached the protection threshold, if they have not, the electrical module continues to control the power module stack to perform load discharge.

[0038] By adopting the above technical solution, the residual power of the power module stack can be continuously recycled and utilized until the voltage and power of the power module stack reach the protection threshold and then stop.

[0039] In summary, this application includes at least the following beneficial technical effects:

[0040] 1. After the flow battery system is shut down, the first contactor between the electrical module and the load can be disconnected, and the second contactor between the electrical module and the residual power recovery module can be closed, connecting the power module stack, the electrical module, and the residual power recovery module. This allows the residual charge in the power module stack to be released into the residual power recovery module, preventing damage to the stack from internal self-discharge. Furthermore, by turning on the residual power recovery circulation pump, the charge recovered by the residual power recovery module can be recharged into the positive and negative electrolyte storage tanks, achieving the purpose of recovering and utilizing residual charge and avoiding energy waste. Moreover, this method does not require an additional load, thus saving costs.

[0041] 2. When the system is discharging normally, the second contactor is open and the first contactor is closed. The electricity released by the power module stack passes through the DC / DC module and the PCS module and reaches the load to complete the discharge operation. After the system stops, the first contactor is opened and the second contactor is closed. The DC / DC module can discharge the power module stack and recover the released electricity into the residual power recovery module.

[0042] 3. The residual power recovery module uses a residual power recovery stack to recover electricity. This residual power recovery stack can be the same as or different from the power module stack, and the overall power of the residual power recovery stack can be appropriately reduced. In addition, the residual power recovery circulation pump of the residual power recovery module includes a residual power recovery positive electrode circulation pump and a residual power recovery negative electrode circulation pump, which can be controlled to connect or disconnect with the positive electrode electrolyte storage tank and the negative electrode electrolyte storage tank, respectively. When connected, the electricity recovered by the residual power recovery stack is recharged into the positive electrode electrolyte storage tank and the negative electrode electrolyte storage tank. Attached Figure Description

[0043] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 A structural block diagram of a flow battery system provided in this application embodiment;

[0045] Figure 2 A flowchart of the control system provided in the embodiments of this application;

[0046] Figure 3 A flowchart illustrating a method for recovering residual electricity after discharge from a flow battery, as provided in this application embodiment. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. Furthermore, the technical features involved in the various embodiments described below can be combined with each other as long as they do not conflict with each other. The application will now be described in detail with reference to the accompanying drawings and embodiments. Example 1

[0048] like Figure 1As shown, Embodiment 1 of this application provides a flow battery system, including a positive electrolyte storage tank (electrolyte+), a negative electrolyte storage tank (electrolyte-), a power module stack, an electrical module, a residual energy recovery module, and a control system; wherein: the power module stack is connected to the positive electrolyte storage tank and the negative electrolyte storage tank respectively through electrolyte connection pipelines, and a power module circulation pump is provided between the power module stack and the positive electrolyte storage tank and the negative electrolyte storage tank; the power module circulation pump includes a power module positive circulation pump (Pump1) and a power module negative circulation pump (Pump2); the power module positive circulation pump is located between the power module stack and the positive electrolyte storage tank, and the power module negative circulation pump is located between the power module stack and the negative electrolyte storage tank. The power module stack is connected to the positive electrolyte storage tank and the negative electrolyte storage tank via a power module positive circulation pump and a power module negative circulation pump, respectively. When the power module positive circulation pump and the power module negative circulation pump are turned off, the positive electrolyte storage tank and the negative electrolyte storage tank cannot replenish the electrolyte of the power module stack. When the power module positive circulation pump and the power module negative circulation pump are turned on, the positive electrolyte storage tank and the negative electrolyte storage tank can replenish the electrolyte of the power module stack. The electrical module is connected to the power module stack, the residual power recovery module, and the load. The electrical module contains a first contactor (K1) and a second contactor (K2). The first contactor controls the switching between the electrical module and the load, and the second contactor controls the switching between the electrical module and the residual power recovery module. The residual power recovery module is connected to both the positive and negative electrolyte storage tanks, and it contains a residual power recovery circulation pump connected to both the positive and negative electrolyte storage tanks. The control system monitors various states of the flow battery system and issues execution commands.

[0049] Through the above technical solution, after the flow battery system is shut down, the first contactor between the electrical module and the load can be disconnected, and the second contactor between the electrical module and the residual power recovery module can be closed, connecting the power module stack, the electrical module, and the residual power recovery module. This allows the residual charge in the power module stack to be released into the residual power recovery module, preventing damage to the stack from internal self-discharge. Furthermore, by turning on the residual power recovery circulation pump, the charge recovered by the residual power recovery module can be recharged into the positive and negative electrolyte storage tanks, achieving the purpose of recovering and utilizing residual charge and avoiding energy waste. Moreover, this method does not require additional load, thus saving costs.

[0050] In some embodiments, the electrical module includes a DC / DC (direct current / direct current) module and a PCS (Power Conversion System) module. The DC / DC module is connected to the power module stack, the residual power recovery module, and the PCS module, respectively. The PCS module is connected to the load. A first contactor is disposed between the DC / DC module and the PCS module; a second contactor is disposed between the DC / DC module and the residual power recovery module. The electrical module is used to realize the charging and discharging of the power module stack, contactor switching, power load application, and shutdown functions. Optionally, the power module stack can consist of one or more stacks, the PCS module can consist of one or more PCS modules, and the DC-DC module can consist of one or more DC-DC modules. Optionally, both the first and second contactors are DC contactors. Using DC contactors can adapt to and match the DC / DC module, and has the characteristics of long life and suitability for frequent start-stop. With the above technical solution, when the system is discharging normally, the second contactor is open and the first contactor is closed. The electricity released by the power module stack reaches the load after passing through the DC / DC module and the PCS module, completing the discharge operation. After the system stops, the first contactor is opened and the second contactor is closed. The DC / DC module can discharge the power module stack and recover the released electricity into the residual power recovery module.

[0051] In some embodiments, the residual power recovery module includes a residual power recovery stack and a residual power recovery circulation pump. The residual power recovery module is used to recover the residual power in the power module stack after discharge and charge the power into the existing electrolyte in the system. The residual power recovery circulation pump includes a residual power recovery positive electrode circulation pump and a residual power recovery negative electrode circulation pump. The residual power recovery stack is connected to the DC / DC module, and the second contactor is disposed between the residual power recovery stack and the DC / DC module. The residual power recovery stack is connected to the positive electrode electrolyte storage tank and the negative electrode electrolyte storage tank through electrolyte connection pipelines, and the residual power recovery positive electrode circulation pump is disposed between the residual power recovery stack and the positive electrode electrolyte storage tank, and the residual power recovery negative electrode circulation pump is disposed between the residual power recovery stack and the negative electrode electrolyte storage tank. Through the above technical solution, the residual power recovery module uses a residual power recovery stack to recover electricity. This residual power recovery stack can be the same as or different from the power module stack, and the overall power of the residual power recovery stack can be appropriately reduced. In addition, the residual power recovery circulation pump of the residual power recovery module includes a residual power recovery positive electrode circulation pump and a residual power recovery negative electrode circulation pump, which can be controlled to connect or disconnect with the positive electrode electrolyte storage tank and the negative electrode electrolyte storage tank, respectively. When connected, the electricity recovered by the residual power recovery stack is recharged into the positive electrode electrolyte storage tank and the negative electrode electrolyte storage tank.

[0052] In some embodiments, the control system includes a detection unit, a first judgment unit (judgment unit 1), a second judgment unit (judgment unit 2), a first control unit (control unit 1), a second control unit (control unit 2), a third control unit (control unit 3), and a fourth control unit (control unit 4), wherein: the detection unit is used to detect the operating status of each component and current and voltage parameters; the first judgment unit is used to determine whether the system is in a shutdown state; the second judgment unit is used to determine whether the current and voltage have reached a protection threshold (this protection threshold is determined according to requirements and is not limited here); the first control unit is used to control the state of the first contactor and the second contactor; the second control unit is used to control the operating state of the power module circulation pump; the third control unit is used to control the operating state of the residual power recovery circulation pump; and the fourth control unit is used to control the start-up, load-bearing, and shutdown of the DC / DC module. By adopting the above technical solution, the control system monitors various states of the flow battery through the detection unit, determines various conditions through the first and second judgment units, and issues various execution commands through the first, second, third, and fourth control units to achieve automated operation of the entire system.

[0053] Based on the above setup, during normal discharge of the flow battery system, the first contactor K1 is closed and the second contactor K2 is open. After discharge, the first contactor K1 of the main circuit is opened while the second contactor K2 of the residual power recovery module is closed. At this time, the electrolyte circulation pumps (Pump1, Pump2) of the power module are turned off, and the electrolyte circulation pumps (Pump3, Pump4) of the residual power recovery module are turned on. The control system sends a command to the DC / DC module to continue discharging the power module stack. The discharge mode changes from constant power to constant voltage. The initial discharge power is usually set to 20% of the rated power (adjusted according to the residual power recovery duration). After discharging to the set voltage of a single stack cell (usually 1.05V), the discharge mode switches to constant voltage. Discharge stops when the discharge current reaches the set value (usually 0.1A). At this time, the second contactor K2 of the residual power recovery module is opened, and the electrolyte circulation pumps (Pump3, Pump4) of the residual power recovery module are turned off, completing the residual power recovery and reuse of the flow battery system.

[0054] Based on the above description of the flow battery system, the following section will further describe the system by explaining the specific workflow of the control system. (Reference) Figure 2 As shown, the specific workflow of the control system includes the following steps.

[0055] Step 1 (Start): The flow battery system begins to discharge according to the control command requirements.

[0056] Step 2 (Determine if the system is shut down): The first determination unit determines whether the flow battery system is shut down. If so, proceed to step 3; otherwise, return to step 1.

[0057] Step 3 (Switch the current output switch to the residual power recovery module): Through the first control unit, control the first contactor K1 to open and the second contactor K2 to close.

[0058] Step 4 (Turn off the main electrolyte circulation pump and turn on the electrolyte circulation pump of the residual power recovery module): Turn off the electrolyte circulation pump of the power module stack through the second control unit; at the same time, turn on the electrolyte circulation pump of the residual power recovery module through the third control unit.

[0059] Step 5 (Perform residual power discharge): The fourth control unit controls the DC / DC module to discharge the power module stack; the electrical energy released in this stage is used to charge the system through the residual power recovery stack.

[0060] Step 6 (Detect whether the voltage and power of the power module stack have reached the threshold): The detection module detects whether the voltage and power of the power module stack have reached the protection threshold; if the protection threshold has been reached, proceed to step 7; otherwise, continue to step 5.

[0061] Step 7 (Stay Discharged from the Power Module Stack): The fourth control unit controls the DC / DC module to stop pulling the load, and the power module stack stops discharging.

[0062] Step 8 (Disconnecting the line contactor): Disconnect the second contactor K2 through the first control unit; at this time, both the first contactor K1 and the second contactor K2 are in the open state.

[0063] Step 9 (Residual Charge Module Circulation Pump Shutdown): Shut down the residual charge module circulation pump via the third control unit; at this time, all circulation pumps used for electrolyte circulation are in the off state.

[0064] Step 10 (End): The entire discharge process and residual power recovery process are now complete. Example 2

[0065] Based on the flow battery system provided in Example 1, Example 2 provides a method for recovering residual charge after discharge from a flow battery, applied to the flow battery system described in Example 1. The method includes:

[0066] Step 101: Determine if the flow battery system has stopped. If it has stopped, disconnect the first contactor and close the second contactor. At the same time, turn off the power module circulation pump and turn on the residual power recovery circulation pump.

[0067] Step 102: Control the electrical module to perform load discharge on the power module stack, recover the power through the residual power recovery module, and charge the electrolyte in the positive electrode electrolyte storage tank and the negative electrode electrolyte storage tank.

[0068] Step 103: Determine whether the voltage and power of the power module stack have reached the protection threshold. If they have, control the electrical module to stop applying load to the power module stack, thus stopping the discharge. If not, continue controlling the electrical module to discharge the power module stack while simultaneously recovering excess electricity through the residual charge recovery module and charging the electrolyte in the positive and negative electrolyte storage tanks. This step allows for continuous recovery and utilization of residual electricity in the power module stack until the voltage and power reach the protection threshold.

[0069] Step 104: Disconnect the second contactor and turn off the residual power recovery circulation pump.

[0070] The specific process of the above method can be found in Example 1, and will not be repeated here.

[0071] By adopting the above technical solution, after the flow battery system is shut down, the first contactor between the electrical module and the load can be disconnected, and the second contactor between the electrical module and the residual power recovery module can be closed, connecting the power module stack, the electrical module, and the residual power recovery module. This allows the residual charge in the power module stack to be released into the residual power recovery module, preventing damage to the stack from internal self-discharge. Furthermore, by turning on the residual power recovery circulation pump, the charge recovered by the residual power recovery module can be recharged into the positive and negative electrolyte storage tanks, achieving the purpose of recovering and utilizing residual charge and avoiding energy waste. Moreover, this method does not require additional load, thus saving costs.

[0072] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A flow battery system, characterized in that, It includes a positive electrolyte storage tank, a negative electrolyte storage tank, a power module stack, an electrical module, a residual energy recovery module, and a control system; among which: The power module stack is connected to the positive electrolyte storage tank and the negative electrolyte storage tank respectively, and a power module circulation pump is provided between the power module stack and the positive electrolyte storage tank and the negative electrolyte storage tank; the power module circulation pump includes a power module positive circulation pump and a power module negative circulation pump; the power module positive circulation pump is located between the power module stack and the positive electrolyte storage tank, and the power module negative circulation pump is located between the power module stack and the negative electrolyte storage tank; The electrical module is connected to the power module stack, the residual energy recovery module, and the load. The electrical module contains a first contactor and a second contactor. The first contactor controls the switching between the electrical module and the load, and the second contactor controls the switching between the electrical module and the residual energy recovery module. The electrical module includes a DC / DC module and a PCS module. The DC / DC module is connected to the power module stack, the residual energy recovery module, and the PCS module, respectively. The PCS module is connected to the load. The first contactor is located between the DC / DC module and the PCS module; the second contactor is located between the DC / DC module and the residual energy recovery module. The residual electricity recovery module is connected to the positive electrolyte storage tank and the negative electrolyte storage tank respectively, and the residual electricity recovery module is provided with a residual electricity recovery circulation pump connected to the positive electrolyte storage tank and the negative electrolyte storage tank; the residual electricity recovery circulation pump includes a residual electricity recovery positive electrode circulation pump and a residual electricity recovery negative electrode circulation pump; the residual electricity recovery stack is connected to the DC / DC module, and the second contactor is disposed between the residual electricity recovery stack and the DC / DC module; the residual electricity recovery stack is connected to the positive electrolyte storage tank and the negative electrolyte storage tank, and the residual electricity recovery positive electrode circulation pump is disposed between the residual electricity recovery stack and the positive electrolyte storage tank, and the residual electricity recovery negative electrode circulation pump is disposed between the residual electricity recovery stack and the negative electrolyte storage tank; The control system is used to monitor various states of the flow battery system and issue execution commands. The control system includes a detection unit, a first judgment unit, a second judgment unit, a first control unit, a second control unit, a third control unit, and a fourth control unit. Specifically: the detection unit detects the operating status of each component and current and voltage parameters; the first judgment unit determines whether the system is in a shutdown state; the second judgment unit determines whether the current and voltage have reached protection thresholds; the first control unit controls the state of the first and second contactors; the second control unit controls the operating state of the power module circulation pump; the third control unit controls the operating state of the residual power recovery circulation pump; and the fourth control unit controls the start-up, load-bearing, and shutdown of the DC / DC module. The discharge mode switches from constant power to constant voltage, with the initial discharge power set to 20% of the rated power. After discharging to the set voltage value of a single cell in the battery stack, the system switches to constant voltage mode, and discharge stops when the discharge current reaches the set value.

2. The flow battery system according to claim 1, characterized in that, Both the first contactor and the second contactor are DC contactors.

3. A method for recovering residual electricity after discharge from a flow battery, applied to the flow battery system according to any one of claims 1-2, characterized in that, include: Determine if the flow battery system has stopped. If it has stopped, disconnect the first contactor and close the second contactor. At the same time, turn off the power module circulation pump and turn on the residual power recovery circulation pump. The control electrical module performs load discharge on the power module stack, recovers the electricity through the residual electricity recovery module, and charges the electrolyte in the positive electrode electrolyte storage tank and the negative electrode electrolyte storage tank; Determine whether the voltage and power of the power module stack have reached the protection threshold. If they have, control the electrical module to stop applying load to the power module stack, thus stopping the power module stack from discharging. Disconnect the second contactor and shut down the residual electricity recovery circulation pump.

4. The method for recovering residual electricity after discharge of a flow battery according to claim 3, characterized in that, When determining whether the voltage and power of the power module stack have reached the protection threshold, if not, the electrical module continues to control the power module stack to perform load discharge.

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