Control method of a flow battery system and flow battery system

Abstract

The application relates to the field of energy storage systems, and provides a control method of a liquid flow battery system and the liquid flow battery system. The liquid flow battery system comprises a battery stack, a first electrolyte tank, a second electrolyte tank, a first liquid path pipeline and a second liquid path pipeline. The first electrolyte tank is provided with a first opening, and the second electrolyte tank is provided with a second opening. The setting positions of the first opening and the second opening are both lower than the liquid level of the electrolyte tank. The first liquid path pipeline is used for connecting the first opening and the second opening, and a valve is arranged on the first liquid path pipeline. The second liquid path pipeline is used for connecting the first electrolyte tank and the battery stack, and connecting the second electrolyte tank and the battery stack. A liquid pump is arranged on the second liquid path pipeline. The method comprises the following steps: acquiring the electric quantity information of the liquid flow battery system and the liquid pump state of the liquid pump. The liquid pump state comprises a resting state and a working state. In the case that the electric quantity information is less than a preset electric quantity and the liquid pump state is in the resting state, the valve is controlled to be opened.

Description

Technical Field

[0001] This application relates to the field of energy storage systems, and more particularly to a control method for a flow battery system and a flow battery system. Background Technology

[0002] In a flow battery, the positive and negative electrolytes are separated by an ion exchange membrane within the battery stack. Ions in the electrolytes pass through the ion exchange membrane under the influence of an electric field and react at the electrodes. However, these ions typically exist as hydrated ions, surrounded by a layer of water molecules. Due to differences in the ability of ions of different valence states to bind water molecules, there is a net flux in the migration direction of water molecules. Taking a vanadium redox flow battery as an example, water molecules generally tend to migrate from the negative electrode side to the positive electrode side, causing the volume of the electrolyte at the positive electrode to continuously increase while the volume at the negative electrode continuously decreases. This electrolyte volume imbalance poses a risk of overflow to the side with increased volume and a risk of pump dredging and cavitation to the side with decreased volume. Avoiding these situations has become a pressing problem to solve. Summary of the Invention

[0003] The main objective of this application is to provide a control method and a flow battery system, which aims to achieve positive and negative electrolyte rebalancing at a lower cost while ensuring the safety of the flow battery.

[0004] In a first aspect, this application provides a control method for a flow battery system, the flow battery system comprising: a battery stack, a first electrolyte tank, a second electrolyte tank, a first liquid path pipe, and a second liquid path pipe; wherein, the first electrolyte tank has a first opening, the first opening being positioned below the liquid surface of the first electrolyte tank; the second electrolyte tank has a second opening, the second opening being positioned below the liquid surface of the second electrolyte tank, the first electrolyte in the first electrolyte tank and the second electrolyte in the second electrolyte tank respectively containing different ions of the same element; the first liquid path pipe is used to connect the first opening and the second opening, and a valve is provided on the first liquid path pipe; the second liquid path pipe is used to connect the first electrolyte tank to the battery stack, and the second electrolyte tank to the battery stack, and a liquid pump is provided on the second liquid path pipe; the method includes: When the valve is in the closed state, the power information of the flow battery system and the pump status of the pump are acquired, including the resting state and the working state. When the power level is less than the preset power level and the pump is in the resting state, the valve is controlled to open.

[0005] Secondly, this application provides a flow battery system, the flow battery system comprising: Battery stack; A first electrolyte tank, the first electrolyte tank having a first opening, the first opening being positioned below the liquid level in the first electrolyte tank; The second electrolyte tank has a second opening, which is positioned below the liquid level in the second electrolyte tank. The first electrolyte in the first electrolyte tank and the second electrolyte in the second electrolyte tank each contain different ions of the same element. A first liquid passage pipeline is used to connect the first opening and the second opening, and a valve is provided on the first liquid passage pipeline; The second liquid passage is used to connect the first electrolyte tank and the battery stack, and the second electrolyte tank and the battery stack. A liquid pump is installed on the second liquid passage. The flow battery system further includes a processor, a memory, and a computer program stored in the memory and executable by the processor, wherein when the computer program is executed by the processor, it implements the steps of the control method as described in any one of the embodiments of this application.

[0006] This application provides a control method for a flow battery system and a flow battery system. By setting a first liquid passage pipe connected below the liquid surface of a first electrolyte tank and a second electrolyte tank, and by controlling the opening or closing of the valve on the first liquid passage pipe, the connection of the first liquid passage pipe can be controlled, thereby achieving safe and controllable rebalancing of the electrolyte volume in the flow battery at extremely low cost. Attached Figure Description

[0007] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0008] Figure 1 A schematic diagram of a flow battery system provided for an embodiment of this application; Figure 2 A schematic flowchart illustrating a control method for a flow battery system provided in an embodiment of this application; Figure 3 This is a schematic diagram of the liquid level difference provided in the embodiments of this application; Figure 4 A schematic flowchart illustrating a control method for a flow battery system according to another embodiment of this application; Figure 5 A curve showing the relationship between the cross-sectional area of ​​a storage tank and the inner diameter of a pipe is provided in one embodiment of this application; Figure 6 This is a schematic block diagram of a flow battery system provided in an embodiment of this application. Detailed Implementation

[0009] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0010] The flowchart shown in the attached diagram is for illustrative purposes only and does not necessarily include all content and operations / steps, nor does it necessarily have to be performed in the order described. For example, some operations / steps can be broken down, combined, or partially merged, so the actual execution order may change depending on the actual situation.

[0011] This application provides a control method for a flow battery system and a flow battery system.

[0012] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0013] Please refer to Figure 1 , Figure 1 This is a schematic diagram of a flow battery system provided for an embodiment of this application.

[0014] like Figure 1 As shown, the flow battery system provided in this application embodiment includes: a battery stack (not shown), a first electrolyte tank 10, a second electrolyte tank 20, a first liquid passage pipe 30, and a second liquid passage pipe (not shown).

[0015] The first electrolyte tank 10 has a first opening 101, which is positioned below the liquid surface of the first electrolyte tank 10; the second electrolyte tank 20 has a second opening 201, which is positioned below the liquid surface of the second electrolyte tank 20; the first electrolyte in the first electrolyte tank 10 and the second electrolyte in the second electrolyte tank 20 each contain different ions of the same element.

[0016] Specifically, taking a vanadium redox flow battery as an example, the first electrolyte tank 10 and the second electrolyte tank 20 are acidic solutions of vanadium ions with different valence states. Assuming the first electrolyte tank 10 is the positive electrode electrolyte tank, the electrolyte in the first electrolyte tank 10 is vanadium oxide ion (VO²⁻). + ), dioxane ions (VO2) +The first electrolyte is a sulfuric acid solution; the second electrolyte tank 20 is a negative electrode electrolyte tank, therefore the electrolyte in the second electrolyte tank 20 is divalent vanadium ions (V²). + ), trivalent vanadium ions (V³ + The solution is a sulfuric acid solution; during the operation of the vanadium redox flow battery, water molecules migrate towards the positive electrode, meaning the volume of the electrolyte in the first electrolyte tank 10 gradually increases. However, this is not the only limitation; the polarity of the first electrolyte tank 10 and the second electrolyte tank 20, as well as the ion types in the flow battery system, are not specified here.

[0017] In some embodiments, the first liquid passage 30 is used to connect the first opening 101 and the second opening 201, and a valve 301 is provided on the first liquid passage 30.

[0018] Specifically, since both the first opening 101 and the second opening 201 are positioned below the liquid surface, connecting the first opening 101 and the second opening 201 via the first liquid passage pipe allows the electrolyte levels in the first electrolyte tank 10 and the second electrolyte tank 20 to tend to balance under the influence of gravity. This reduces the volume of electrolyte in the tank with the higher liquid level and increases the volume of electrolyte in the tank with the lower liquid level, achieving a rebalancing operation of the electrolyte volume. However, to prevent the positive and negative electrolytes from continuously reacting in the first liquid passage pipe, which could lead to a decrease in battery capacity, this embodiment of the application includes a valve 301 on the first liquid passage pipe 30. Only when the valve 301 is open can the positive and negative electrolytes come into contact in the first liquid passage pipe 30, making the rebalancing process through the first liquid passage pipe 30 controllable.

[0019] In some embodiments, the second liquid passage is used to connect the first electrolyte tank 10 to the battery stack, and the second electrolyte tank 20 to the battery stack, and a liquid pump is provided on the second liquid passage.

[0020] Specifically, the electrolyte in the first electrolyte tank 10 and the electrolyte in the second electrolyte tank 20 need to react in the battery stack. Therefore, both are connected to the battery stack through second liquid passage pipes, and the electrolyte is continuously pumped to the battery stack by a liquid pump. The specific structure of the battery stack and the second liquid passage pipes can be found in the flow battery provided in related technologies, and will not be described in detail here.

[0021] Please refer to Figure 2 , Figure 2 This is a flowchart illustrating a control method for a flow battery system provided in an embodiment of this application.

[0022] like Figure 2 As shown, the control method for the flow battery system provided in this application includes steps S101 to S102.

[0023] Steps S101 to S102 can be executed by the battery management system (BMS) in the flow battery system.

[0024] Step S101: When the valve is in the closed state, obtain the power information of the flow battery system and the pump status of the pump, the pump status including resting state and working state.

[0025] For example, the charge information can be the State of Charge (SOC) of the flow battery system. When the SOC is low, the valence states of the positive and negative electrolytes are relatively close, and their potentials are also similar. Connecting the positive and negative electrolytes through the first liquid path results in a gentler reaction, reducing energy loss from mixing. Taking a vanadium redox flow battery as an example, at high SOCs, the positive electrolyte is mainly strongly oxidizing pentavalent vanadium, while the negative electrolyte is mainly strongly reducing divalent vanadium. Mixing them releases a large amount of heat, posing a certain danger, and may also generate insoluble substances, leading to permanent loss of active vanadium. At low SOCs, the positive electrolyte is mainly tetravalent vanadium, and the negative electrolyte is mainly trivalent vanadium. Mixing them carries almost no risk of heat release, making operation safer, and almost no loss of active vanadium. Therefore, obtaining the charge information of the flow battery system ensures that the valve on the first liquid path is opened only when the charge information is low to perform a rebalancing operation, reducing the safety risks and charge loss associated with the rebalancing operation.

[0026] For example, to avoid affecting the pumping operation and rebalancing, it is also necessary to ensure that the liquid pump is in a quiescent state during volume rebalancing. Therefore, the BMS is also communicatively connected to the liquid pump on the second liquid line, enabling it to obtain the liquid pump status, which can be either quiescent or operational. Operational status indicates that the liquid pump is pumping electrolyte, while quiescent status indicates that the liquid pump is stopped.

[0027] Step S102: When the power information is less than the preset power and the liquid pump is in the resting state, control the valve to open.

[0028] Understandably, during step S101, the valve is in a closed state, and is only opened when the conditions in step S102 are met. This ensures that the valve in the flow battery system provided in this application is normally closed, preventing continuous reaction of the positive and negative electrode electrolytes that could cause charge loss and the generation of bypass current. The closed state indicates that liquid cannot pass through the valve, while the open state indicates that liquid can flow through the valve.

[0029] The preset battery level can be set according to actual needs. For example, the preset battery level can be set to 10% by default, which provides a high level of safety when performing a rebalancing operation. Of course, this is not the only option; users can also choose any value within the range of 0% to 50% as the preset battery level.

[0030] As mentioned earlier, opening the valve when the battery level is less than the preset level can prevent the battery capacity loss caused by violent reactions of the positive and negative electrolytes when the battery level is high, as well as the bypass DC caused by direct connection between the positive and negative electrolytes.

[0031] Specifically, with the valve open, the transfer of electrolyte through the first liquid path is entirely driven by gravity, with the driving force originating from the hydrostatic pressure difference between the first and second electrolyte tanks. When the electrolyte level in one tank is higher than in the other, the resulting hydrostatic pressure difference forces the electrolyte to passively flow from the higher tank to the lower tank through the first liquid path until the levels on both sides are equal. The formula for the driving pressure at any given time t is:

[0032] Where ρ represents the electrolyte density, which is approximately 1,400 kg / m³ in a vanadium redox flow battery, g = 9.81 m / s² is the gravitational acceleration, and Δh(t) is the difference in liquid level between the two electrolyte tanks at any time t.

[0033] Please refer to Figure 3 , Figure 3 This is a schematic diagram of the liquid level difference provided in the embodiments of this application.

[0034] like Figure 3 As shown, it is understandable that there is a liquid level difference Δh(t) between the liquid levels of the first electrolyte tank 10 and the second electrolyte tank 20. When the valve is open, as the volume rebalancing process proceeds, Δh(t) gradually decreases, and the driving force also decreases accordingly. Therefore, the control method provided in this embodiment allows for rebalancing between the first and second electrolyte tanks simply by opening the valve, without requiring any additional operations, making the rebalancing operation simple and controllable.

[0035] Please see Figure 4 , Figure 4 This is a flowchart illustrating a control method for a flow battery system according to another embodiment of this application.

[0036] like Figure 4 As shown, in some embodiments, the method further includes: step S103, controlling the valve to close after controlling the valve to open for a first preset time.

[0037] For example, after the valve is opened in step S102, in order to prevent the positive and negative electrolytes from reacting for a long time when the first liquid pipeline is connected, causing a short circuit in the electrolyte and thus triggering continuous chemical self-discharge, the valve opening time should be limited to a certain duration. After the valve opening time reaches the first preset time, the valve is controlled to close, so that the valve remains normally closed under normal conditions.

[0038] The first preset duration can be set according to actual needs. Based on factors such as the flow rate of the positive and negative electrode electrolytes under gravity, the first preset duration can be set to 15 minutes. Of course, it is not limited to this. The first preset duration can also be arbitrarily selected within the range of 0 to 120 minutes.

[0039] In addition to controlling the valve to close based on the duration of valve opening, the valve can also be controlled to close based on other conditions, such as controlling the valve to close when the liquid pump is detected to be in working condition, or controlling the valve to close when the flow battery system is detected to be starting to charge or discharge.

[0040] In some embodiments, the method further includes: After controlling the valve to open for a first preset time, the valve is controlled to close, and the operation interval time is accumulated after the valve is closed; When the operation interval reaches a preset time threshold, the valve is controlled to open, and after the valve has been open for a second preset time, the valve is controlled to close, wherein the second preset time is less than the first preset time.

[0041] Understandably, if the conditions in step S102 of the flow battery system are not met for an extended period, to prevent severe volume imbalance between the first and second electrolyte tanks during long-term operation, a rebalancing operation is directly performed, i.e., the valve is opened, provided the interval since the last rebalancing operation has reached the second preset time. Furthermore, in this case, since the charge level may be high, the valve opening time should be shorter than the first preset valve opening time during normal rebalancing in step S102, to prevent the positive and negative electrolytes from reacting and releasing large amounts of heat for an extended period in the first liquid path when the state of charge (SOC) is high. This reduces the level difference between the positive and negative electrolyte tanks to some extent and prevents prolonged reaction and excessive heat release by the positive and negative electrolytes.

[0042] The preset duration threshold can be 84 hours, but it is not limited to this. The value of the preset duration threshold can also be determined according to the migration rate of water molecules, and the selectable range is 1 to 500 hours. The second preset duration can be 1 / 3 of the first preset duration. If the first preset duration is 15 minutes, the second preset duration can be 5 minutes.

[0043] In some embodiments, a liquid level sensor is provided in the first electrolyte tank, the liquid level sensor being used to send a first status signal or a second status signal when it is immersed in the electrolyte in the first electrolyte tank, and to send the other of the first status signal or the second status signal when it is not immersed in the electrolyte in the first electrolyte tank; the method further includes: When the detection signal of the liquid level sensor changes from the first state signal to the second state signal, the valve is controlled to open; After the valve has been open for a first preset time, the valve is controlled to close.

[0044] For example, a level sensor can be installed in the positive electrolyte tank and / or the negative electrolyte tank to detect the increase or decrease in the electrolyte volume.

[0045] Assuming the level sensor outputs a high-level signal when immersed in liquid and a low-level signal when not immersed, taking a vanadium redox flow battery as an example, if the level sensor installed in the positive electrolyte tank changes from low to high, it indicates that the volume of the positive electrolyte has increased to the position of the level sensor, which may indicate a volume imbalance; or, if the level sensor installed in the negative electrolyte tank changes from high to low, it indicates that the volume of the negative electrolyte has decreased to the position of the level sensor, which may also indicate a volume imbalance.

[0046] Understandably, the first electrolyte tank can be a positive electrolyte tank or a negative electrolyte tank, or both the first and second electrolyte tanks can be equipped with level sensors.

[0047] Therefore, when the signal from the liquid level sensor changes, it indicates that the electrolyte volume in at least one electrolyte tank has increased or decreased by a certain amount, meaning there is a certain degree of volume imbalance. At this point, a volume rebalancing operation is performed, which means the control valve is opened. Furthermore, since the accumulated volume imbalance has reached a certain value, the control valve is kept open for a relatively long first preset time to ensure that the imbalanced volume can be restored.

[0048] In some embodiments, the method further includes: After the valve is opened, if a charging or discharging command is received, the valve is closed. After the valve has been closed for a preset waiting time, or after receiving confirmation of the valve closure, the pump is controlled to change from the resting state to the working state and perform a charging or discharging operation.

[0049] In a dual-flow flow battery system, both the positive and negative electrolytes are stored in external electrolyte tanks, while the electrochemical reaction occurs only inside the stack. Only a small amount of electrolyte is retained within the stack chamber for the reaction, and during charging and discharging, the electrolyte level in the stack chamber is very limited, typically only enough for a few seconds to tens of seconds of reaction. Therefore, upon receiving a charging or discharging command, the liquid pump needs to be activated to pump the positive and negative electrolytes from the electrolyte tanks to the stack. To avoid a large amount of heat release due to a chemical short circuit in the electrolyte, the system must be shut down during rebalancing. Once a charging or discharging command is detected, the rebalancing operation is stopped, i.e., the control valve is closed. Only after the valve is confirmed to be closed can the liquid pump be restarted to perform the charging or discharging operation, thus improving the safety of the flow battery system.

[0050] The system allows setting a preset waiting time to confirm valve closure, with the preset waiting time being longer than the valve's operating time. For example, if the valve closure requires 1 second, the preset waiting time is set to 5 seconds. If no abnormal signal is received 5 seconds after the valve is closed, the system determines that the valve has completed the closure operation and controls the pump to switch to operating mode.

[0051] Alternatively, the valve can communicate with the controller in the BMS, sending a closure confirmation message to the controller after closing. Upon receiving the closure confirmation message, the controller can confirm that the valve has been closed, thereby controlling the pump to switch to the operating state.

[0052] In some embodiments, the method further includes: Upon receiving a fault indication message from the valve, the valve status before receiving the fault indication message is obtained, including a closed state and an open state. If the valve is in the closed state, a first alarm prompt is issued; If the valve status is not the closed state, a second alarm is issued, wherein the second alarm has a higher priority than the first alarm.

[0053] Understandably, in order to improve the safety of the flow battery system and avoid the large amount of heat generated by chemical short circuits, the valve in the flow battery system provided in this application embodiment is normally closed and is only opened for a certain period of time when certain conditions are met, such as when the conditions in step S102 are met, the valve is opened for a first preset time.

[0054] Therefore, in the event of a valve malfunction (such as jamming), if the valve was in the closed state before the malfunction, it will remain in the faulty state. While it's impossible to open the valve for volume rebalancing, at least the positive and negative electrolytes cannot come into contact through the first liquid path, ensuring the safety of the flow battery system. In this situation, a low-priority first alarm is output, such as a reminder to the user to have it inspected within 7 days. The user can wait until a rebalancing operation is needed before addressing the valve malfunction.

[0055] However, if the valve was in an open or unknown state before the malfunction, it indicates that it may remain open during the malfunction process, allowing the positive and negative electrolytes to remain in contact through the first liquid path, posing a risk of chemical short circuit. In this case, a second alarm with higher priority will be output, strongly reminding the user to address the valve malfunction as soon as possible to avoid the safety risks caused by the large amount of heat released from the reaction of the positive and negative electrolytes.

[0056] In some embodiments, the electrolyte in at least one of the first electrolyte tank and the second electrolyte tank is sulfuric acid electrolyte, and the material of the first liquid pipeline is at least one of polyvinyl chloride, polypropylene, polyvinylidene fluoride, and polytetrafluoroethylene.

[0057] For example, the first liquid circuit pipes and valves must be chemically resistant to concentrated vanadium electrolyte in sulfuric acid, and therefore the first liquid circuit pipes and valves can be made of materials including but not limited to PVC, PP, PVDF and PTFE.

[0058] In some embodiments, the flow battery system is a vanadium redox flow battery system, the first liquid passage is a straight circular tube with a uniform cross-section, and the inner diameter of the first liquid passage is 8~12mm.

[0059] To avoid violent reactions between the positive and negative electrolytes, the first liquid path pipeline needs to have a small inner diameter. However, since the valve on the first liquid path pipeline is normally closed and only opens for a first preset time period, the first liquid path pipeline can have a larger inner diameter within an acceptable range to ensure that the liquid levels in the first and second electrolyte tanks can reach equilibrium in a shorter time.

[0060] Specifically, in a vanadium redox flow battery system, the Reynolds number of the positive and negative electrode electrolytes is ≤2300, and the first liquid path pipe is a straight circular pipe with a constant cross-section. In this case, the liquid flow in the first liquid path pipe is laminar flow, and the flow rate is described by the Hagen-Poiseuille Equation:

[0061] Where d represents the inner diameter of the first liquid path pipe, η is the dynamic viscosity of the electrolyte, and L is the length of the first liquid path pipe.

[0062] Since the liquid level difference Δh(t) decreases continuously during the equilibrium process, the system exhibits a first-order exponential decay characteristic:

[0063] Its time constant is:

[0064] Where A represents the cross-sectional area of ​​a single storage tank (assuming the two tanks have equal areas).

[0065] In this scenario, assuming the first preset time is 15 minutes = 900 seconds, in order to achieve at least 90% liquid level balance within the first preset time of 15 minutes, that is... Substituting into the exponential formula, we get Taking the natural logarithm of both sides yields Therefore, the time constant in this case can be obtained as follows:

[0066] The minimum inner diameter of the first liquid flow pipe is:

[0067] Therefore, the inner diameter of the first liquid passage is proportional to the fourth root of its length. Furthermore, the required inner diameter of the first liquid passage is proportional to the initial height difference between the liquid levels in the two electrolyte tanks. No. Although a larger level difference will generate a greater driving pressure, it will also require a larger volume of liquid to be transferred, and these two effects will cancel each other out.

[0068] Representative parameters for vanadium electrolyte: viscosity η = 5 mPa·s, density ρ = 1,400 kg / m³ Assuming the pipe length L = 1m, the required pipe inner diameter d varies with the cross-sectional area A of the storage tank as follows:

[0069] As can be seen, the 8–12 mm inner diameter covers a tank cross-sectional area of ​​0.25–1.0 m², which is typical for commercial vanadium redox flow battery systems. The Reynolds number remains between 350 and 1,750 under all operating conditions—fully laminar flow.

[0070] Specifically, please refer to Figure 5 , Figure 5 The curve showing the relationship between the cross-sectional area of ​​the storage tank and the inner diameter of the pipe is provided for one embodiment of this application.

[0071] like Figure 5 As shown, for different pipe lengths (0.5m, 1.0m, 2.0m), the inner diameter of the pipe increases slowly with the increase of the cross-sectional area of ​​the storage tank. When the pipe length is 1m and the cross-sectional area of ​​the storage tank is 0.25~1.0m², the inner diameter of the pipe is preferably 8~12mm.

[0072] The pipe length L and the pipe inner diameter d have the property d∝ The effect is relatively mild: doubling the pipe length only increases the required inner diameter by a small amount. ≈19%. For a storage tank with A=0.25m², the scaling relationship is as follows:

[0073] Therefore, when the diameter of the first liquid path pipeline is 8~12mm, the pipeline length ranges from 0.5 to 2.0m.

[0074] In some embodiments, the volume of the first liquid passage is less than 10% of the maximum volume difference between the first electrolyte tank and the second electrolyte tank.

[0075] For example, each time the valve is opened, the volume of electrolyte contained inside the first liquid path pipe constitutes a small amount of anolyte-cathode mixture. Therefore, to limit unnecessary cross-contamination, the pipe volume should not exceed 10% of the expected volume loss per cycle. Assuming a pipe with an inner diameter d = 10 mm and a length L = 1 m, its volume is approximately 78 mL, which is far less than 10% of the typical difference in electrolyte volume between the positive and negative electrodes (1~5.5 L).

[0076] In some embodiments, the distance between the first opening and the bottom of the first electrolyte tank is less than a preset distance, and the distance between the second opening and the bottom of the second electrolyte tank is less than a preset distance.

[0077] Specifically, the first and second openings are located at or near the lowest accessible point of each electrolyte tank and below the lowest expected electrolyte level during normal operation. This arrangement maximizes the electrolyte height above the first and second openings, thereby providing the maximum available hydrostatic pressure differential under a given volume imbalance condition, thus allowing the use of the smallest possible pipe diameter.

[0078] For example, the above method can be implemented as a computer program that can run on the flow battery system provided in the embodiments of this application.

[0079] Please see Figure 6 , Figure 6 This is a schematic block diagram of a flow battery system provided in an embodiment of this application.

[0080] like Figure 6 As shown, the flow battery system includes a processor, a memory, and a network interface connected via a system bus, wherein the memory may include a storage medium and internal memory.

[0081] The storage medium may store the operating system and computer programs. The computer programs include program instructions, which, when executed, cause the processor to perform any control method.

[0082] The processor provides computing and control capabilities to support the operation of the entire flow battery system.

[0083] Internal memory provides an environment for the execution of computer programs stored in the storage medium. When the computer program is executed by the processor, it enables the processor to perform any control method.

[0084] This network interface is used for network communication, such as sending assigned tasks. Those skilled in the art will understand that... Figure 6 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the flow battery system to which the present application is applied. A specific flow battery system may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0085] It should be understood that the processor can be a Central Processing Unit (CPU), but it can also be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. Among these, a general-purpose processor can be a microprocessor or any conventional processor.

[0086] In one embodiment, the processor is configured to run a computer program stored in memory to perform the following steps: When the valve is in the closed state, the power information of the flow battery system and the pump status of the pump are acquired, including the resting state and the working state. When the power level is less than the preset power level and the pump is in the resting state, the valve is controlled to open.

[0087] It should be noted that those skilled in the art will understand that, for the sake of convenience and brevity, the specific working process of the flow battery system described above can be referred to the corresponding process in the control method embodiment of the aforementioned flow battery system, and will not be repeated here.

[0088] It should be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the application. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0089] It should also be understood that the term "and / or" as used in this specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations. It should be noted that, herein, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or system. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or system that includes that element.

[0090] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments. The above descriptions are merely specific implementations of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A control method for a flow battery system, characterized in that, The flow battery system includes: a battery stack, a first electrolyte tank, a second electrolyte tank, a first liquid path pipe, and a second liquid path pipe; wherein, the first electrolyte tank has a first opening, the first opening being positioned below the liquid surface of the first electrolyte tank; the second electrolyte tank has a second opening, the second opening being positioned below the liquid surface of the second electrolyte tank, the first electrolyte in the first electrolyte tank and the second electrolyte in the second electrolyte tank each containing different ions of the same element; the first liquid path pipe connects the first opening and the second opening, and a valve is provided on the first liquid path pipe; the second liquid path pipe connects the first electrolyte tank to the battery stack, and the second electrolyte tank to the battery stack, and a liquid pump is provided on the second liquid path pipe; the method includes: When the valve is in the closed state, the power information of the flow battery system and the pump status of the pump are acquired, including the resting state and the working state. When the power level is less than the preset power level and the pump is in the resting state, the valve is controlled to open.

2. The control method according to claim 1, characterized in that, The method further includes: After the valve is opened for a first preset time, the valve is closed.

3. The control method according to claim 2, characterized in that, The method further includes: After controlling the valve to open for a first preset time, the valve is controlled to close, and the operation interval time is accumulated after the valve is closed; When the operation interval reaches a preset time threshold, the valve is controlled to open, and after the valve has been open for a second preset time, the valve is controlled to close, wherein the second preset time is less than the first preset time.

4. The control method according to claim 1, characterized in that, The first electrolyte tank is equipped with a liquid level sensor, which is used to send a first status signal or a second status signal when the liquid level sensor is submerged in the electrolyte in the first electrolyte tank, and to send the other of the first status signal or the second status signal when the liquid level sensor is not submerged in the electrolyte in the first electrolyte tank; the method further includes: When the detection signal of the liquid level sensor changes from the first state signal to the second state signal, the valve is controlled to open; After the valve has been open for a first preset time, the valve is controlled to close.

5. The control method according to claim 1, characterized in that, The method further includes: After the valve is opened, if a charging or discharging command is received, the valve is closed. After the valve has been closed for a preset waiting time, or after receiving confirmation of the valve closure, the pump is controlled to change from the resting state to the working state and perform a charging or discharging operation.

6. The control method according to any one of claims 1 to 5, characterized in that, The method further includes: Upon receiving a fault indication message from the valve, the valve status before receiving the fault indication message is obtained, including a closed state and an open state. If the valve is in the closed state, a first alarm prompt is issued; If the valve status is not the closed state, a second alarm is issued, wherein the second alarm has a higher priority than the first alarm.

7. The control method according to any one of claims 1 to 5, characterized in that, The flow battery system is a vanadium redox flow battery system, the first liquid passage is a straight circular tube with a constant cross-section, and the inner diameter of the first liquid passage is 8~12mm.

8. The control method according to claim 7, characterized in that, The inner diameter of the first liquid passage is proportional to the fourth root of the length of the first liquid passage.

9. The control method according to claim 7, characterized in that, The first cross-sectional area of ​​the first electrolyte tank is equal to the second cross-sectional area of ​​the second electrolyte tank, and the first cross-sectional area and the second cross-sectional area are 0.25–1.0 m².

10. A flow battery system, characterized in that, The flow battery system includes: Battery stack; A first electrolyte tank, the first electrolyte tank having a first opening, the first opening being positioned below the liquid level in the first electrolyte tank; The second electrolyte tank has a second opening, which is positioned below the liquid level in the second electrolyte tank. The first electrolyte in the first electrolyte tank and the second electrolyte in the second electrolyte tank each contain different ions of the same element. A first liquid passage pipeline is used to connect the first opening and the second opening, and a valve is provided on the first liquid passage pipeline; The second liquid passage is used to connect the first electrolyte tank and the battery stack, and the second electrolyte tank and the battery stack. A liquid pump is installed on the second liquid passage. The flow battery system further includes a processor, a memory, and a computer program stored in the memory and executable by the processor, wherein the computer program, when executed by the processor, implements the steps of the control method as described in any one of claims 1 to 9.

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