An intelligent control system and method for recovering the electrolyte capacity of a vanadium redox flow battery

Abstract

This application relates to an intelligent control system and method for electrolyte capacity recovery in a vanadium redox flow battery. The system mainly includes a level detection unit, a capacity analysis unit, a valence state analysis unit, a reducing agent addition actuator, a piping system, and a central processing unit. The central processing unit is communicatively connected to the level detection unit, capacity analysis unit, valence state analysis unit, reducing agent addition actuator, and piping system. It determines whether to initiate a level balancing operation based on level data and capacity retention rate. When the capacity recovery rate of the level balancing operation is lower than a preset recovery threshold, the valence state analysis unit is activated to detect the valence state. Based on the average valence state of vanadium ions, it determines whether to perform a valence state repair operation via the reducing agent addition actuator. After the valence state repair reaches the target, it controls the piping system to perform a mixing repair operation. This application enables timely detection and precise control of electrolyte capacity decay, maintaining a high level of battery system capacity retention.

Description

Technical Field

[0001] This application relates to the field of flow battery technology, and in particular to an intelligent control system and method for electrolyte capacity recovery in a vanadium redox flow battery. Background Technology

[0002] Vanadium redox flow batteries have become an important technological route in the field of large-scale energy storage due to their advantages such as long cycle life, high safety, and adjustable capacity. Their working principle is based on the valence state conversion between the positive electrode VO²⁺ / VO₂⁺ redox couple and the negative electrode V²⁺ / V³⁺ redox couple to achieve energy storage and release.

[0003] However, during long-term operation of vanadium redox flow batteries, due to differences in the permeability of the ion exchange membrane to different vanadium ions, transmembrane migration of vanadium ions occurs between the positive and negative electrolytes, leading to level deviations in the two electrolytes and causing vanadium ion valence imbalance. The combined effect of level deviation and valence imbalance results in a continuous decrease in the usable discharge capacity of the battery system. Currently, the industry mainly relies on manual periodic monitoring of the electrolyte state (such as periodic sampling and titration analysis) to determine whether to perform level balancing or mixing operations based on the test results. This manual monitoring method suffers from large response delays and high detection errors, making it impossible to monitor electrolyte level deviations and valence state changes in real time. Untimely intervention or improper operation can easily exacerbate capacity decay and even damage the internal structure of the battery.

[0004] Based on the above, how to solve the technical problem of continuous capacity decay caused by the lack of real-time monitoring and adaptive control of electrolyte status during the operation of vanadium redox flow batteries 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, this application provides an intelligent control system and method for electrolyte capacity recovery in vanadium redox flow batteries. By conducting online real-time monitoring of the liquid level, valence state, and discharge capacity of the positive and negative electrolytes, and based on the monitoring results, automatically executing capacity recovery operations according to a graded progressive strategy of liquid level balance—valence state analysis and repair—mixed electrolyte repair, the system achieves timely detection and precise control of electrolyte capacity decay, thereby maintaining the battery system capacity retention rate at a high level.

[0006] The embodiments of this application adopt the following technical solutions: In a first aspect, this application provides an intelligent control system for electrolyte capacity recovery in a vanadium redox flow battery, comprising: A liquid level detection unit is installed in the positive electrode storage tank and the negative electrode storage tank of the vanadium redox flow battery to collect the liquid level data of the electrolyte in the positive electrode storage tank and the negative electrode storage tank in real time. The capacity analysis unit is communicatively connected to the battery tester of the vanadium redox flow battery, and is used to acquire the real-time discharge curve of the vanadium redox flow battery and calculate the capacity retention rate. The valence state analysis unit is connected to the electrolyte circulation pipelines of the positive electrode storage tank and the negative electrode storage tank respectively, and is used to detect the average valence state of vanadium ions in the positive electrode electrolyte and the negative electrode electrolyte online. A reducing agent addition actuator is connected to the electrolyte circulation pipeline and is used to quantitatively inject a reducing agent solution into the electrolyte. The piping system includes a mixing pipeline connecting the positive electrode storage tank and the negative electrode storage tank, and an electric valve installed on the mixing pipeline, which is used to open the electric valve when a mixing command is received to achieve bidirectional mixing of the positive electrode electrolyte and the negative electrode electrolyte. The central processing unit is communicatively connected to the liquid level detection unit, the capacity analysis unit, the valence state analysis unit, the reducing agent addition actuator, and the pipeline system. It is used to determine whether to initiate a liquid level balancing operation based on the liquid level data and the capacity retention rate. When the capacity recovery rate of the liquid level balancing operation is lower than a preset recovery threshold, it activates the valence state analysis unit to perform valence state detection. Based on the average valence state of vanadium ions, it determines whether to perform a valence state repair operation through the reducing agent addition actuator. After the valence state repair reaches the target, it controls the pipeline system to perform a mixed liquid repair operation.

[0007] By adopting the above technical solution, an intelligent control system is integrated, which combines the liquid level detection unit, capacity analysis unit, valence state analysis unit, reducing agent addition actuator, pipeline system and central processing unit into one unit. This system enables online real-time monitoring of the electrolyte level, vanadium ion valence state and discharge capacity of the vanadium redox flow battery. The central processing unit automatically performs capacity recovery operations according to a graded progressive strategy of liquid level balance, valence state analysis and repair, and mixed liquid repair. This solves the technical problem of continuous capacity decay caused by the lack of real-time monitoring and adaptive control capabilities of electrolyte state in existing technologies, and maintains the capacity retention rate of the vanadium redox flow battery system at a high level.

[0008] In some embodiments, the central processing unit is further configured to: After the liquid level balancing operation is completed, the capacity recovery rate calculated by the capacity analysis unit is obtained; When the capacity recovery rate is lower than the preset recovery threshold, the liquid level balance is determined to be in failure, and the valence state analysis unit is automatically activated to detect the valence state of the positive and negative electrolytes. When the average valence state of the vanadium ions is within the preset valence state range, the pipeline system is directly controlled to perform mixed liquid repair operation; When the average valence state of vanadium ions is higher than the upper limit of the preset valence state qualified range, the reducing agent addition actuator is first controlled to perform a valence state repair operation. After the average valence state of vanadium ions drops to the preset valence state qualified range, the pipeline system is then controlled to perform a mixed liquid repair operation.

[0009] By adopting the above technical solution, a decision-making mechanism for automatically switching to the valence state analysis and repair stage after liquid level balance failure was established. The operation path of directly mixing the liquid or repairing the valence state first and then mixing the liquid is distinguished according to whether the average valence state of vanadium ions is within the qualified range. This avoids ion cross-contamination and further capacity decay caused by blindly mixing the liquid when the vanadium ion valence state is abnormal.

[0010] In some embodiments, the central processing unit is further configured to: After the mixed solution repair operation is completed, the vanadium redox flow battery is controlled to undergo charge-discharge testing and the capacity recovery rate is calculated by the capacity analysis unit. When the capacity recovery rate is greater than or equal to the preset capacity qualification threshold, the capacity recovery is determined to be successful; When the capacity recovery rate is less than the preset capacity qualification threshold, the valence state analysis unit is restarted to perform valence state detection, and the valence state repair operation and mixed liquid repair operation are re-executed based on the valence state detection result.

[0011] By adopting the above technical solution, an effectiveness verification step is added after the mixed liquid remediation operation is completed. If the verification fails, the process is automatically backtracked to the valence state analysis stage to re-execute the control procedure, forming a complete closed-loop feedback mechanism to ensure the final effectiveness of the capacity restoration operation.

[0012] In some implementations, the capacity analysis unit is also used to record capacity retention rate data for multiple consecutive cycles and establish a capacity decay database; The central processing unit is also used to perform linear regression analysis based on the capacity retention rate data in the capacity decay database, calculate the capacity decay rate, and dynamically adjust the liquid level deviation threshold and the capacity retention rate threshold according to the capacity decay rate. Specifically, when the capacity decay rate is greater than a preset accelerated decay threshold, the central processing unit lowers the liquid level deviation threshold and increases the capacity retention rate threshold; when the capacity decay rate is less than a preset decelerated decay threshold, the central processing unit increases the liquid level deviation threshold and lowers the capacity retention rate threshold.

[0013] By adopting the above technical solution, the intelligent control system can dynamically adjust the control trigger threshold based on the capacity decay rate, enabling it to adaptively determine the timing of control intervention according to the actual operating state of the battery. It can intervene in advance when the capacity decays rapidly to avoid the capacity decaying to an unrecoverable level, and reduce unnecessary control operations when the capacity decays slowly to reduce the consumption of reducing agent and the number of system shutdowns. This overcomes the defect that fixed thresholds cannot adapt to the dynamic changes in capacity decay at different operating stages.

[0014] In some implementations, the central processing unit is also used to predict the remaining number of cycles required for the capacity retention rate to reach the critical capacity retention rate based on the capacity decay rate; when the remaining number of cycles is less than a preset warning cycle number, the central processing unit issues a warning signal in advance and initiates control preparation.

[0015] By adopting the above technical solution and using the capacity decay rate for trend prediction, early warning and preparation can be initiated before the capacity retention rate reaches the control trigger threshold, realizing the transformation from passive response to active prevention and further shortening the control response time.

[0016] Secondly, this application provides a method for intelligent control of electrolyte capacity recovery in a vanadium redox flow battery, comprising: Liquid level balancing step: Real-time acquisition of electrolyte level data in the positive and negative electrode storage tanks of the vanadium redox flow battery, and acquisition of the real-time discharge curve of the vanadium redox flow battery to calculate the capacity retention rate; when the liquid level deviation between the positive and negative electrode storage tanks is greater than or equal to the liquid level deviation threshold, or when the capacity retention rate is lower than the capacity retention rate threshold, liquid level balancing operation is performed. Failure determination step: After the liquid level balancing operation is completed, the capacity recovery rate is calculated; when the capacity recovery rate is lower than the preset recovery threshold, the liquid level balancing is determined to be failed, and the valence state analysis step is entered. Valence state analysis steps: Online spectral detection is used to scan the positive and negative electrolytes to calculate the average valence state of vanadium ions; Valence state repair step: When the average valence state of vanadium ions is higher than the upper limit of the preset valence state qualified range, the amount of reducing agent to be added is calculated based on the deviation between the average valence state of vanadium ions and the target valence state and the electrolyte volume. The reducing agent solution is injected into the electrolyte until the average valence state of vanadium ions drops to the preset valence state qualified range. Mixed electrolyte repair steps: When the average valence state of vanadium ions is within the preset valence state range, the vanadium redox flow battery is discharged to reduce the state of charge to the preset charge range. Then, the mixing passage between the positive electrode storage tank and the negative electrode storage tank is opened to perform bidirectional mixing of the positive electrode electrolyte and the negative electrode electrolyte.

[0017] By adopting the above technical solution, an intelligent control method for restoring the electrolyte capacity of vanadium redox flow batteries is provided, which follows a hierarchical progressive strategy of liquid level balance, failure judgment, valence state analysis, valence state repair, and mixed liquid repair. This method realizes real-time monitoring of electrolyte state and automatic execution of adaptive capacity recovery operation, and solves the technical problem of continuous capacity decay caused by the lack of real-time monitoring and adaptive control capability of electrolyte state in the prior art.

[0018] In some embodiments, in the valence state repair step, a trial dose of reducing agent solution is first injected according to a preset ratio of the calculated reducing agent addition amount. After a preset time interval, the valence state of the electrolyte is retested. Based on the retest results, the amount of remaining reducing agent is adjusted and the injection is completed.

[0019] By adopting the above technical solution and using a step-by-step addition strategy that combines trial addition with retesting and correction, the problem of excessive or insufficient addition of reducing agent due to calculation deviations is avoided by adding it all at once, thus improving the accuracy and safety of valence state restoration.

[0020] In some embodiments, the mixed-liquid remediation step further includes: During the mixing process, the electrolyte temperature is monitored in real time. When the temperature is higher than the preset upper temperature limit, the mixing operation is paused and restarted after the temperature drops below the preset lower temperature limit. After the mixed liquid repair operation is completed, a charge-discharge test is performed and the capacity recovery rate is calculated. When the capacity recovery rate is less than the preset capacity qualification threshold, the valence state analysis step is returned to re-execute the valence state analysis, valence state repair and mixed liquid repair operations.

[0021] By adopting the above technical solutions, a temperature protection mechanism and a closed-loop performance verification are added to the mixed liquid remediation process. This not only ensures the safety of the mixed liquid process, but also ensures that the capacity recovery operation can be automatically backtracked and readjusted if the target is not met, thus forming a complete capacity recovery guarantee system.

[0022] In some implementations, an adaptive threshold adjustment step is also included: Record capacity retention rate data for multiple consecutive cycles and establish a capacity decay database; Linear regression analysis was performed on the capacity retention rate data in the capacity decay database to calculate the capacity decay rate; The level deviation threshold and the capacity retention rate threshold are dynamically adjusted according to the capacity decay rate; wherein, when the capacity decay rate is greater than the preset accelerated decay threshold, the level deviation threshold is decreased and the capacity retention rate threshold is increased; when the capacity decay rate is less than the preset decelerated decay threshold, the level deviation threshold is increased and the capacity retention rate threshold is decreased.

[0023] By adopting the above technical solution, the control trigger threshold is dynamically adjusted based on the capacity decay rate, enabling the intelligent control method to adaptively determine the timing of control intervention according to the actual operating state of the battery, thus overcoming the defect that a fixed threshold cannot adapt to the dynamic changes in capacity decay at different operating stages.

[0024] In some implementations, the adaptive threshold adjustment step further includes: predicting the remaining number of cycles required for the capacity retention rate to reach the critical capacity retention rate based on the capacity decay rate; and issuing an early warning signal and initiating control preparation when the remaining number of cycles is less than a preset warning cycle number.

[0025] By adopting the above technical solutions, trend prediction and early warning can be made using the capacity decay rate, realizing the transformation from passive response to proactive prevention, further shortening the control response time, and avoiding the situation where intervention is only made after the capacity decays to an unrecoverable level.

[0026] In summary, this application includes at least the following beneficial technical effects: 1. An intelligent control system integrating the liquid level detection unit, capacity analysis unit, valence state analysis unit, reducing agent addition actuator, and pipeline system with the central processing unit enables online real-time monitoring of the liquid level, vanadium ion valence state, and discharge capacity of the vanadium redox flow battery electrolyte. The central processing unit automatically performs capacity recovery operations according to a graded progressive strategy of liquid level balancing, valence state analysis and repair, and mixed liquid repair. This solves the problems of large response delay, high detection error, and untimely intervention that exist in existing technologies that rely on manual periodic detection, thus maintaining the capacity retention rate of the battery system at a high level. 2. By establishing a liquid level balance failure judgment mechanism and a branch decision logic based on the average valence state of vanadium ions, the system automatically switches to the valence state repair and mixed liquid repair stages when the liquid level balance operation cannot effectively restore the capacity. A step-by-step reducing agent addition strategy combining trial addition and retesting correction is adopted to minimize the error in reducing agent addition control, thus avoiding secondary pollution caused by excessive addition and ion cross-contamination caused by blind mixing. 3. Through an adaptive threshold adjustment mechanism based on the capacity decay rate and a trend prediction and early warning function, the control system can dynamically determine the timing of intervention based on the actual operating status of the battery. It can intervene in advance when the capacity decays rapidly to avoid irreversible losses, and reduce unnecessary intervention when the capacity decays slowly to reduce operation and maintenance costs, thus realizing the transformation from fixed-cycle maintenance to intelligent adaptive control. Attached Figure Description

[0027] 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.

[0028] Figure 1 This application provides a structural block diagram of an intelligent control system for electrolyte capacity recovery in a vanadium redox flow battery. Figure 2 A flowchart of the intelligent control method for electrolyte capacity recovery in a vanadium redox flow battery provided in this application embodiment; Figure 3 This is a schematic diagram of an adaptive threshold adjustment mechanism based on capacity decay trend prediction provided in an embodiment of this application. Detailed Implementation

[0029] 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

[0030] It should be noted that during long-term operation of vanadium redox flow batteries, due to the difference in permeability of the ion exchange membrane to different vanadium ions, vanadium ion migration occurs across the membrane between the positive and negative electrolytes, leading to liquid level deviation and vanadium ion valence state imbalance, which in turn causes continuous capacity decay. Existing manual periodic monitoring methods have large response delays and high detection errors, making it impossible to monitor the electrolyte status in real time and implement timely capacity recovery operations. In severe cases, capacity decay can decrease by more than 50%.

[0031] To solve the above problems, refer to Figure 1 This embodiment provides an intelligent control system for electrolyte capacity recovery in a vanadium redox flow battery, including a level detection unit, a capacity analysis unit, a valence state analysis unit, a reducing agent addition actuator, a piping system, and a central processing unit.

[0032] The liquid level detection unit employs a laser rangefinder with an accuracy of ±0.3mm. It is vertically mounted on the tops of the positive and negative electrode storage tanks of the vanadium redox flow battery, respectively, to collect real-time electrolyte level data in both tanks. The unit collects data every 30 seconds and uses a temperature compensation algorithm to eliminate measurement errors caused by thermal expansion and contraction of the electrolyte.

[0033] The capacity analysis unit communicates with the battery tester for vanadium redox flow batteries to acquire real-time discharge curves and calculate capacity retention based on these curves. The capacity retention rate is calculated by dividing the current discharge capacity by the initial discharge capacity and multiplying by 100%. The capacity recovery rate is calculated by dividing the increase in discharge capacity after the liquid level balancing operation by the decrease in discharge capacity before the operation and multiplying by 100%. Furthermore, the capacity analysis unit establishes a capacity decay database, recording the capacity retention rate and capacity decay trend for five consecutive cycles.

[0034] The valence state analysis unit employs an online ultraviolet-visible spectrometer with a wavelength range of 300-800 nm, equipped with a 2048-pixel array CCD (charge-coupled device) sensor, achieving a spectral resolution of 1.5 nm and a detection accuracy of ±0.03 valence states. The valence state analysis unit is connected to the electrolyte circulation pipelines of both the positive and negative electrode storage tanks, enabling online scanning of the positive and negative electrolytes and real-time calculation of the average valence state of vanadium ions. To improve detection reliability, three consecutive spectral data points are acquired for each valence state detection, and the average value is used as the basis for valence state calculation to eliminate random errors. During system initialization, a 3 mol / L sulfuric acid solution is used as a reference for spectrometer baseline calibration.

[0035] The reducing agent addition mechanism includes a reducing agent storage tank, a precision metering pump, and a static mixer. The reducing agent storage tank contains a 0.5 mol / L ascorbic acid solution and is equipped with nitrogen protection to prevent oxidation and deterioration of the reducing agent. The tank volume is configured to be 5% of the battery system capacity. The precision metering pump is located between the reducing agent storage tank and the electrolyte circulation line, with a flow rate range of 10-100 mL / min. It is driven by a stepper motor, achieving a microstepping accuracy of 1 / 128 and a flow rate accuracy of ±0.5%. The static mixer is located at the connection between the outlet of the precision metering pump and the electrolyte circulation line to promote uniform mixing of the reducing agent solution and the electrolyte.

[0036] The piping system uses corrosion-resistant tubing made of perfluoroalkoxy polymer (PFA), including a mixing line connecting the positive and negative electrode storage tanks, and an electrically operated three-way valve installed on the mixing line. This valve opens upon receiving a mixing command to achieve bidirectional mixing of the positive and negative electrolytes. The system also includes a temperature sensor on the mixing line for real-time monitoring of the electrolyte temperature during the mixing process.

[0037] The central processing unit (CPU) employs an embedded industrial controller equipped with an ARM Cortex-M7 core and integrates a valence state analysis algorithm library. The CPU communicates with the level detection unit, volume analysis unit, valence state analysis unit, reducing agent addition actuator, and piping system.

[0038] refer to Figure 2 The control process of the central processing unit is as follows: Liquid level balancing stage: The central processing unit receives liquid level data collected by the liquid level detection unit and capacity retention rate calculated by the capacity analysis unit in real time. When the liquid level deviation between the positive and negative electrode storage tanks is greater than or equal to 20% (i.e., the liquid level deviation threshold), or the capacity retention rate is lower than 70% (i.e., the capacity retention rate threshold), the central processing unit automatically initiates the liquid level balancing operation. The liquid level balancing operation opens the liquid equalization passage between the positive and negative electrode storage tanks through an electric three-way valve in the pipeline system, transferring the electrolyte from the high liquid level side to the low liquid level side until the liquid levels on both sides tend to be equal.

[0039] The initial liquid level balancing operation can achieve a volume recovery rate of about 18% (the measured range is 16%-21%), but the recovery ability continues to decline with the increase of the number of operations.

[0040] Failure determination phase: After the liquid level balancing operation is completed, the central processing unit calculates the capacity recovery rate through the capacity analysis unit. When the capacity recovery rate is lower than 5% (i.e., the preset recovery threshold), the central processing unit determines that the liquid level balancing has failed and automatically starts the valence state analysis unit to detect the valence state of the positive and negative electrolytes.

[0041] Valence state analysis stage: The valence state analysis unit uses an online ultraviolet-visible spectrometer to scan the electrolyte, continuously collects spectral data three times, takes the average value, and calculates the average valence state of vanadium ions.

[0042] When the average valence state of vanadium ions is between 3.5 and 3.6 (i.e., within the preset acceptable valence state range), the central processing unit directly controls the pipeline system to perform mixed liquid repair operation.

[0043] When the average valence state of vanadium ions is greater than or equal to 3.6 (i.e., higher than the upper limit of the preset acceptable valence state range), the central processing unit first controls the reducing agent addition actuator to perform the valence state repair operation.

[0044] Valence state restoration stage: The central processing unit calculates the amount of reducing agent to be added based on the deviation between the average vanadium ion valence state and the target valence state (3.50±0.02) and the electrolyte volume. To ensure the accuracy of the restoration, a trial dose of reducing agent solution, amounting to 20% of the calculated amount, is injected at a rate of 10 mL / min using a precision metering pump. The valence state of the electrolyte is retested after 15 minutes, and the remaining reducing agent amount is adjusted based on the retest results before the injection is completed. A spectral retest is performed 5 minutes after each injection of reducing agent until the average vanadium ion valence state drops to 3.50±0.02. After the reducing agent addition is complete, the pipeline is flushed to prevent crystallization blockage.

[0045] If the average valence state of vanadium ions exceeds the standard in the first test, a small dose (20% of the predicted amount) of reducing agent is added as a trial. The test is repeated after 15 minutes. The final amount is adjusted based on the results of the second test. This step-by-step strategy effectively avoids secondary pollution caused by excessive addition at one time.

[0046] Mixing and Repair Stage: After the average valence state of vanadium ions is within the preset acceptable range, the central processing unit first controls the vanadium redox flow battery to discharge, reducing the state of charge (SOC) to 30%-40%. Then, the mixing pathway between the positive and negative electrode storage tanks is opened to allow for bidirectional mixing of the positive and negative electrolytes. The initial mixing flow rate is set to 1 / 3 of the normal operating circulation flow rate.

[0047] During the mixing process, temperature sensors on the piping system monitor the electrolyte temperature in real time. To reduce temperature response time, the central processing unit immediately pauses the mixing operation when the temperature exceeds 38°C; the mixing operation is restarted once the temperature drops below 30°C.

[0048] Performance Verification Phase: After the mixed-solution repair operation is completed, the central processing unit controls the vanadium redox flow battery to perform charge-discharge tests and calculates the capacity recovery rate through the capacity analysis unit. When the capacity recovery rate is greater than or equal to 95% (i.e., the preset capacity qualification threshold), the capacity recovery is considered successful. When the capacity recovery rate is less than 95%, the central processing unit returns to the valence state analysis step, restarts the valence state analysis unit to perform valence state detection, and re-executes the valence state repair operation and mixed-solution repair operation based on the valence state detection results until the capacity recovery meets the standard.

[0049] Through the aforementioned intelligent control system and methods, online real-time monitoring of the electrolyte level, vanadium ion valence state, and discharge capacity of the vanadium redox flow battery is achieved. The central processing unit automatically executes capacity recovery operations according to a tiered, progressive strategy of level balancing, valence state analysis and repair, and mixed electrolyte repair. The detection cycle is shortened to 25 minutes, with a detection accuracy of ±0.8%. The error in reducing agent addition is controlled to less than 2.5%, avoiding secondary pollution caused by excessive addition. The battery system capacity retention rate is maintained above 70%, and the annual degradation rate is reduced to 0.5%. Approximately 80% of manual maintenance workload is reduced, saving about 150,000 yuan in maintenance costs per system per year. The electrolyte lifespan is extended by approximately 50%. Example 2

[0050] This embodiment 2 uses the intelligent control system and method for electrolyte capacity recovery in vanadium redox flow batteries described in embodiment 1, and applies it to a 40kW / 220kWh vanadium redox flow battery system. The system parameters are: total electrolyte volume 2000L, rated operating temperature 25℃, and discharge capacity of 40kWh under normal operating conditions.

[0051] During operation, the liquid level detection unit detected a liquid level deviation of over 20% between the positive and negative electrode storage tanks. Simultaneously, the capacity analysis unit calculated that the capacity retention rate was below 70% (current discharge capacity is 27.6 kWh, capacity retention rate is approximately 69%). The central processing unit then automatically initiated a liquid level balancing operation. This operation uses an electrically operated three-way valve in the piping system to open the liquid equalization path between the positive and negative electrode storage tanks, transferring electrolyte from the high-level side to the low-level side.

[0052] After the initial leveling operation, the discharge capacity increased from 27.6 kWh to 34.5 kWh, representing a capacity recovery rate of approximately 18%. The entire adjustment process took 5 minutes, during which the battery maintained normal power supply without shutdown. After 100 consecutive cycles following leveling, the discharge capacity remained between 33.4 and 34.5 kWh, and the system energy efficiency recovered from 72% to 81%. Subsequent continuous operation over 720 hours showed no energy efficiency degradation exceeding 1%. Example 3

[0053] This embodiment 3 uses the intelligent control system and method for electrolyte capacity recovery in vanadium redox flow batteries described in embodiment 1, applied to a 120kW / 500kWh vanadium redox flow battery energy storage power station. The system parameters are: total electrolyte volume 4000L, matching reducing agent storage tank volume 200L (storing 0.5mol / L ascorbic acid solution), valence state analysis unit using an online UV-Vis spectrometer with a spectral resolution of 1.5nm, and precision metering pump flow rate range 10-100mL / min.

[0054] After 300 hours of continuous operation, the capacity analysis unit detected that the capacity retention rate was only 62%. The central processing unit first initiated a liquid level balancing operation. After the operation was completed, the capacity recovery rate was only 3%, which was lower than the preset recovery threshold of 5%. The central processing unit determined that the liquid level balancing had failed and automatically activated the valence state analysis unit.

[0055] An online ultraviolet-visible spectrometer scanned the positive and negative electrolytes, acquiring three consecutive spectral data points and averaging them. The average valence state of vanadium ions in the electrolyte was found to be 3.62. Since the average valence state of vanadium ions was higher than the upper limit of the preset acceptable valence state range of 3.6, the central processing unit initiated a valence state repair operation.

[0056] The central processing unit, considering the electrolyte circulation rate (50 L / min) and the total electrolyte volume (4000 L), calculated that 7.8 L of reducing agent solution needed to be added. Following operating procedures, a trial dose of 1.56 L (20% of the calculated amount) was injected at a rate of 10 mL / min using a precision metering pump. After a 15-minute interval, the valence state analysis unit retested the average vanadium ion valence state in the electrolyte, finding it to be 3.58. Based on the retest result, the central processing unit adjusted the remaining amount to be added and then replenished with 6.24 L of reducing agent solution. After the reducing agent addition was completed, the pipeline flushing procedure was initiated to prevent crystallization blockage. The final retest showed an average vanadium ion valence state of 3.51, within the preset acceptable range (3.5-3.6).

[0057] After the valence state is restored to the target, the central processing unit controls the vanadium redox flow battery to discharge until the state of charge drops to 35%. Then, the electric three-way valve in the mixing pipeline is opened to initiate bidirectional mixing at 1 / 3 of the normal operating circulation flow rate. During the mixing process, the temperature sensor continuously monitors the electrolyte temperature, which never exceeds 38°C. After mixing is completed, a charge-discharge test is performed. The capacity recovery rate reaches 97%, which is greater than the preset capacity qualification threshold of 95%. The central processing unit determines that the capacity recovery is successful.

[0058] After adjustment, the average vanadium ion valence state in the electrolyte stabilized at 3.51, the system energy efficiency remained at 80%, and the capacity retention rate remained at around 97%. Compared with the traditional offline detection and adjustment method, this operation saved approximately 1,600 yuan in labor costs and avoided a power generation loss of approximately 180 kWh due to downtime. Example 4

[0059] This embodiment 4 uses the intelligent control system and method for electrolyte capacity recovery in vanadium redox flow batteries described in embodiment 1, applied to a 30kW / 100kWh distributed vanadium redox flow battery system. The system parameters are: total electrolyte volume 700L, and the valence state analysis unit uses a miniaturized ultraviolet-visible spectrophotometer (detection wavelength 350-800nm).

[0060] After 200 hours of system operation, the capacity analysis unit detected a capacity retention rate of 68%. The central processing unit sequentially performed liquid level balancing operations; if the liquid level balancing effect was unsatisfactory, valence state analysis was automatically initiated. The online UV-Vis spectrophotometer detected an average valence state of vanadium ions in the electrolyte of 3.61, which is higher than the upper limit of the preset acceptable valence state range of 3.6.

[0061] The central processing unit calculated that 1.4 L of reducing agent solution needed to be added. A precision metering pump initially injected 0.28 L (20% of the calculated amount) at a flow rate of 30 mL / min. After a 15-minute interval, the average vanadium ion valence state of the electrolyte was measured again and found to be 3.57. A second injection of 1.12 L was then performed at a flow rate of 45 mL / min. No leaks were observed during the entire flow path switching process, and no crystallization deposition occurred in the pipeline. The final measured average vanadium ion valence state was 3.50, within the preset acceptable range.

[0062] After the valence state is restored to the target, the central processing unit controls the battery to discharge to 35% state of charge according to the mixed electrolyte repair process, and initiates the bidirectional mixed electrolyte operation. After the mixed electrolyte is completed, a charge-discharge test is performed. If the capacity recovery rate reaches 96%, which is greater than the preset capacity qualification threshold of 95%, the capacity recovery is deemed successful.

[0063] After adjustment, the average valence state of vanadium ions in the electrolyte stabilized at 3.50, and the service life of the electrolyte was extended by 42% compared with before the system was adopted. A single adjustment process consumes only 0.3% of the system's energy, which is far lower than the 5%-8% energy consumption ratio of the electrolytic regeneration method. Example 5

[0064] It should be noted that the control triggering conditions in Examples 1 to 4 all use fixed liquid level deviation thresholds (20%) and capacity retention thresholds (70%). However, in actual operation, the capacity decay rate of the vanadium redox flow battery will dynamically change with operating time, ambient temperature, and charge / discharge regime. Using fixed thresholds has two problems: first, when the capacity decay rate is fast, a fixed threshold may lead to control intervention too late, when the capacity has decayed to a level that is difficult to recover; second, when the capacity decay rate is slow, a fixed threshold may lead to unnecessary frequent control operations, increasing reductant consumption and the number of system shutdowns.

[0065] refer to Figure 3 This embodiment adds an adaptive threshold adjustment mechanism based on capacity decay trend prediction, based on embodiments 1 to 4.

[0066] After the capacity analysis unit records capacity retention rate data for multiple consecutive cycles (10 consecutive cycles in this embodiment), the central processing unit performs linear regression analysis on this data to calculate the capacity decay rate. The capacity decay rate is defined as the decrease in capacity retention rate per unit cycle, expressed as % per cycle.

[0067] The central processing unit dynamically adjusts the liquid level deviation threshold and the capacity retention rate threshold based on the capacity decay rate. The specific adjustment method is as follows: Liquid level deviation threshold = reference liquid level deviation threshold × correction factor; The reference liquid level deviation threshold is 20%, and the correction factor is calculated as: reference attenuation rate / actual attenuation rate. The reference attenuation rate is the standard attenuation rate preset during system design based on battery specifications and operating conditions.

[0068] Capacity retention rate threshold = Baseline capacity retention rate threshold + Compensation value; The baseline capacity retention rate threshold is 70%, and the compensation value is K × (actual attenuation rate - baseline attenuation rate), where K is a preset compensation coefficient.

[0069] When the actual decay rate is greater than the reference decay rate, the correction coefficient is less than 1, and the liquid level deviation threshold is reduced (e.g., from 20% to 15%), meaning that a smaller liquid level deviation can trigger liquid level balancing operation; at the same time, the compensation value is positive, and the capacity retention rate threshold is increased (e.g., from 70% to 75%), meaning that regulation is intervened as soon as the capacity retention rate begins to decline.

[0070] When the actual decay rate is less than the baseline decay rate, the correction factor is greater than 1, and the liquid level deviation threshold is increased (e.g., from 20% to 25%), reducing unnecessary frequent liquid level balancing operations; at the same time, the compensation value is negative, and the capacity retention rate threshold is reduced (e.g., from 70% to 65%), allowing for greater natural fluctuation space in capacity when decay is slower.

[0071] Furthermore, the central processing unit also predicts the remaining number of cycles required for the capacity retention rate to reach the critical capacity retention rate (set to 70% in this embodiment) based on the capacity decay rate. The prediction formula is as follows: Remaining cycles = (Current capacity retention rate - Critical capacity retention rate) / Capacity decay rate; When the predicted remaining number of cycles is less than the preset warning cycle number (set to 20 cycles in this embodiment), the central processing unit issues a warning signal in advance and initiates control preparation (including checking the liquid level of the reducing agent storage tank, confirming the status of valves in the pipeline system, and performing baseline calibration of the spectrometer, etc.).

[0072] The following example illustrates a 120kW / 500kWh vanadium redox flow battery energy storage power station. During continuous operation, the capacity analysis unit recorded the capacity retention rates for 10 consecutive cycles as follows: 92%, 91.2%, 90.3%, 89.2%, 88.0%, 86.6%, 85.1%, 83.4%, 81.5%, and 79.5%. The central processing unit calculated the capacity decay rate to be 1.39% per cycle using linear regression analysis, while the system's preset baseline decay rate is 0.5% per cycle.

[0073] Since the actual decay rate (1.39% / cycle) is much greater than the baseline decay rate (0.5% / cycle), the central processing unit dynamically adjusts the threshold as follows: Correction factor = 0.5 / 1.39 ≈ 0.36; Liquid level deviation threshold = 20% × 0.36 ≈ 7.2%; Compensation value = K × (1.39 - 0.5), take K = 5, then compensation value = 4.45%; Capacity retention threshold = 70% + 4.45% = 74.45% The adjusted threshold enables the system to initiate regulation as soon as the liquid level deviation reaches 7.2% or the capacity retention rate drops to 74.45%, which is much earlier than the intervention timing when a fixed threshold is used.

[0074] Meanwhile, the current capacity retention rate is 79.5%, the critical capacity retention rate is 70%, the capacity decay rate is 1.39% / cycle, and the central processing unit predicts the remaining number of cycles to be: Remaining number of cycles = (79.5% - 70%) / 1.39% ≈ 6.8 times; Since 6.8 times is far less than the preset warning cycle number of 20 times, the central processing unit immediately issued a warning signal and initiated control preparations.

[0075] Through an adaptive threshold adjustment mechanism based on capacity decay rate, the system can intervene and regulate approximately 10 cycles earlier during the rapid capacity decay phase (compared to a fixed threshold scheme), avoiding intervention only when capacity decays below 62%, resulting in better capacity recovery after each regulation. Simultaneously, during the stable operation phase with slower capacity decay, the adjusted threshold reduces unnecessary regulation operations by approximately 40%, lowering reductant consumption and system downtime. The trend prediction and early warning function reduces regulation preparation time from over 30 minutes to less than 5 minutes, achieving a shift from passive response to proactive prevention.

[0076] The following technical details have been reflected in the above embodiments or can be combined with the above embodiments, and are further explained here: Regarding multiple sampling for spectral detection: In the valence state analysis step, the valence state analysis unit continuously collects spectral data three times for each detection and takes the average value as the basis for valence state calculation. This measure can eliminate random errors in the spectral detection process (such as instantaneous interference caused by electrolyte flow, bubbles, etc.), keeping the valence state detection accuracy within ±0.03.

[0077] Regarding nitrogen protection for the reducing agent addition actuator: The reducing agent storage tank is equipped with nitrogen protection function. By continuously introducing nitrogen into the top of the storage tank to isolate air, it prevents the ascorbic acid solution from being oxidized and decomposed during storage, ensuring that the effective concentration of the reducing agent remains stable within its service life.

[0078] Regarding pipeline flushing: After the reducing agent is added, the system automatically initiates the pipeline flushing procedure, using electrolyte to flush the pipeline section from the precision metering pump to the static mixer. This step prevents residual reducing agent solution from crystallizing in the pipeline and causing blockages, ensuring the long-term reliable operation of the pipeline system.

[0079] Regarding the mixing flow rate control: The initial mixing flow rate is set to 1 / 3 of the normal operating circulation flow rate to control the reaction rate during mixing of the positive and negative electrolytes and avoid a sharp rise in electrolyte temperature due to excessively rapid mixing. As mixing progresses, the concentration difference between the electrolytes on both sides gradually decreases, and the heat release from the reaction decreases. The mixing flow rate can be gradually increased based on temperature monitoring.

[0080] 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 smart control system for electrolyte capacity recovery in a vanadium redox flow battery, characterized in that, include: A liquid level detection unit is installed in the positive electrode storage tank and the negative electrode storage tank of the vanadium redox flow battery to collect the liquid level data of the electrolyte in the positive electrode storage tank and the negative electrode storage tank in real time. The capacity analysis unit is communicatively connected to the battery tester of the vanadium redox flow battery, and is used to acquire the real-time discharge curve of the vanadium redox flow battery and calculate the capacity retention rate. The valence state analysis unit is connected to the electrolyte circulation pipelines of the positive electrode storage tank and the negative electrode storage tank respectively, and is used to detect the average valence state of vanadium ions in the positive electrode electrolyte and the negative electrode electrolyte online. A reducing agent addition actuator is connected to the electrolyte circulation pipeline and is used to quantitatively inject a reducing agent solution into the electrolyte. The piping system includes a mixing pipeline connecting the positive electrode storage tank and the negative electrode storage tank, and an electric valve installed on the mixing pipeline, which is used to open the electric valve when a mixing command is received to achieve bidirectional mixing of the positive electrode electrolyte and the negative electrode electrolyte. The central processing unit is communicatively connected to the liquid level detection unit, the capacity analysis unit, the valence state analysis unit, the reducing agent addition actuator, and the pipeline system. It is used to determine whether to initiate a liquid level balancing operation based on the liquid level data and the capacity retention rate. When the capacity recovery rate of the liquid level balancing operation is lower than a preset recovery threshold, it initiates the valence state analysis unit to perform valence state detection. Based on the average valence state of vanadium ions, it determines whether to perform a valence state repair operation through the reducing agent addition actuator. After the valence state repair reaches the target, it controls the pipeline system to perform a mixed liquid repair operation. The capacity analysis unit is further configured to record capacity retention rate data for multiple consecutive cycles and establish a capacity decay database; the central processing unit is further configured to perform linear regression analysis based on the capacity retention rate data in the capacity decay database, calculate the capacity decay rate, and dynamically adjust the liquid level deviation threshold and the capacity retention rate threshold according to the capacity decay rate; wherein, when the capacity decay rate is greater than a preset accelerated decay threshold, the central processing unit lowers the liquid level deviation threshold and raises the capacity retention rate threshold; when the capacity decay rate is less than a preset decelerated decay threshold, the central processing unit raises the liquid level deviation threshold and lowers the capacity retention rate threshold; The central processing unit is also used to predict the remaining number of cycles required for the capacity retention rate to reach the critical capacity retention rate based on the capacity decay rate; when the remaining number of cycles is less than the preset warning cycle number, the central processing unit issues a warning signal in advance and starts control preparation.

2. The intelligent control system for electrolyte capacity recovery in a vanadium redox flow battery according to claim 1, characterized in that, The central processing unit is also used for: After the liquid level balancing operation is completed, the capacity recovery rate calculated by the capacity analysis unit is obtained; When the capacity recovery rate is lower than the preset recovery threshold, the liquid level balance is determined to be in failure, and the valence state analysis unit is automatically activated to detect the valence state of the positive and negative electrolytes. When the average valence state of the vanadium ions is within the preset valence state range, the pipeline system is directly controlled to perform mixed liquid repair operation; When the average valence state of vanadium ions is higher than the upper limit of the preset valence state qualified range, the reducing agent addition actuator is first controlled to perform a valence state repair operation. After the average valence state of vanadium ions drops to the preset valence state qualified range, the pipeline system is then controlled to perform a mixed liquid repair operation.

3. The intelligent control system for electrolyte capacity recovery in a vanadium redox flow battery according to claim 2, characterized in that, The central processing unit is also used for: After the mixed solution repair operation is completed, the vanadium redox flow battery is controlled to undergo charge and discharge tests, and the capacity recovery rate is calculated by the capacity analysis unit. When the capacity recovery rate is greater than or equal to the preset capacity qualification threshold, the capacity recovery is determined to be successful; When the capacity recovery rate is less than the preset capacity qualification threshold, the valence state analysis unit is restarted to perform valence state detection, and the valence state repair operation and mixed liquid repair operation are re-executed based on the valence state detection result.

4. A method for intelligent control of electrolyte capacity recovery in a vanadium redox flow battery, characterized in that, include: Liquid level balancing step: Real-time acquisition of electrolyte level data in the positive and negative electrode storage tanks of the vanadium redox flow battery, and acquisition of the real-time discharge curve of the vanadium redox flow battery to calculate the capacity retention rate; when the liquid level deviation between the positive and negative electrode storage tanks is greater than or equal to the liquid level deviation threshold, or when the capacity retention rate is lower than the capacity retention rate threshold, liquid level balancing operation is performed. Failure determination step: After the liquid level balancing operation is completed, the capacity recovery rate is calculated; when the capacity recovery rate is lower than the preset recovery threshold, the liquid level balancing is determined to be failed, and the valence state analysis step is entered. Valence state analysis steps: Online spectral detection is used to scan the positive and negative electrolytes to calculate the average valence state of vanadium ions; Valence state repair step: When the average valence state of vanadium ions is higher than the upper limit of the preset valence state qualified range, the amount of reducing agent to be added is calculated based on the deviation between the average valence state of vanadium ions and the target valence state and the electrolyte volume. The reducing agent solution is injected into the electrolyte until the average valence state of vanadium ions drops to the preset valence state qualified range. Mixed electrolyte repair steps: When the average valence state of vanadium ions is within the preset valence state qualified range, the vanadium redox flow battery is discharged to reduce the state of charge to the preset charge range. Then, the mixing passage between the positive electrode storage tank and the negative electrode storage tank is opened to perform bidirectional mixing of the positive electrode electrolyte and the negative electrode electrolyte. It also includes an adaptive threshold adjustment step: recording capacity retention rate data for multiple consecutive cycles and establishing a capacity decay database; Linear regression analysis is performed on the capacity retention rate data in the capacity decay database to calculate the capacity decay rate; the liquid level deviation threshold and the capacity retention rate threshold are dynamically adjusted according to the capacity decay rate; wherein, when the capacity decay rate is greater than a preset accelerated decay threshold, the liquid level deviation threshold is decreased and the capacity retention rate threshold is increased; when the capacity decay rate is less than a preset decelerated decay threshold, the liquid level deviation threshold is increased and the capacity retention rate threshold is decreased. The adaptive threshold adjustment step further includes: predicting the remaining number of cycles required for the capacity retention rate to reach the critical capacity retention rate based on the capacity decay rate; and issuing an early warning signal and initiating control preparation when the remaining number of cycles is less than the preset warning cycle number.

5. The intelligent control method for electrolyte capacity recovery in a vanadium redox flow battery according to claim 4, characterized in that, In the valence state restoration step, a trial dose of reducing agent solution is first injected according to the preset ratio of the calculated reducing agent addition amount. After a preset time interval, the valence state of the electrolyte is retested. Based on the retest results, the amount of remaining reducing agent is adjusted and the injection is completed.

6. The intelligent control method for electrolyte capacity recovery in a vanadium redox flow battery according to claim 4, characterized in that, The mixed-liquid remediation step also includes: During the mixing process, the electrolyte temperature is monitored in real time. When the temperature is higher than the preset upper temperature limit, the mixing operation is paused and restarted after the temperature drops below the preset lower temperature limit. After the mixed liquid repair operation is completed, a charge-discharge test is performed and the capacity recovery rate is calculated. When the capacity recovery rate is less than the preset capacity qualification threshold, the valence state analysis step is returned to re-execute the valence state analysis, valence state repair and mixed liquid repair operations.

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