Method and device for evaluating power overload capacity of all-vanadium redox flow battery

Abstract

The invention provides a method and device for evaluating the power overload capacity of an all-vanadium redox flow battery, and the method comprises the steps: carrying out a power step experiment on the battery at a plurality of charge state points in a full charge state range through a grid-connected power conversion system, synchronously acquiring a voltage response curve and a current response curve corresponding to each charge state point in the discharging process of the battery; inputting the voltage response curve and the current response curve corresponding to each charge state point into a Randles equivalent circuit model, and identifying to obtain each electrochemical parameter; performing polynomial fitting on each electrochemical parameter, and establishing a continuous function relation expression between each electrochemical parameter and the state of charge; and determining the maximum overload power which can be supported by the all-vanadium redox flow battery in the full charge state range based on each continuous function relation expression and a steady-state voltage equation of the battery equivalent circuit. According to the invention, accurate, continuous and predictable evaluation of the power overload capacity of the all-vanadium redox flow battery is realized.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage system technology, and in particular to a method and apparatus for evaluating the power overload capacity of a vanadium redox flow battery. Background Technology

[0002] As the penetration rate of renewable energy continues to increase, the demand for rapid power response and overload capacity of energy storage systems in power grids is growing. Vanadium redox flow batteries (VRBs) are widely used in frequency regulation, peak shaving, and grid-based active support applications due to their advantages such as power-capacity decoupling, long lifespan, and high safety. However, the electrochemical characteristics of VRBs mean that their internal resistance, open-circuit voltage, and other electrochemical parameters vary significantly under different states of charge (SOC), resulting in a strong SOC dependence on the overload power that VRBs can withstand.

[0003] Currently, most flow battery systems still use fixed power limits or empirical safety margins in their power scheduling and protection strategy design. This approach may lead to the following problems under low or high SOC conditions: (1) Conservative operation: Limiting the system's dynamic response capability and reducing energy storage utilization; (2) Risk operation: underestimating the risk of rising internal resistance or voltage drop can lead to irreversible damage such as battery over-discharge, hydrogen evolution, and membrane damage, thereby threatening system safety.

[0004] Therefore, an effective technical solution is urgently needed to solve the above-mentioned technical problems. Summary of the Invention

[0005] This invention provides a method and apparatus for evaluating the power overload capacity of vanadium redox flow batteries. This invention enables accurate, continuous and predictable evaluation of the power overload capacity of vanadium redox flow batteries, which helps to improve the safety and dynamic response performance of flow battery systems under complex operating conditions.

[0006] In a first aspect, the present invention provides a method for evaluating the power overload capacity of a vanadium redox flow battery, the method comprising the following steps: Through a grid-connected power conversion system, a power step experiment is performed on the vanadium redox flow battery at multiple pre-selected state of charge points within the full state of charge range, and the voltage response curve and current response curve corresponding to each state of charge point are collected simultaneously during the discharge process of the vanadium redox flow battery. The voltage response curves and current response curves corresponding to each of the stated charge state points are input into the Randles equivalent circuit model to identify the electrochemical parameters of the Randles equivalent circuit model at different charge state points. Polynomial fitting was performed on each of the electrochemical parameters to establish a continuous functional relationship between each electrochemical parameter and the state of charge. Based on the continuous functional relationship between each electrochemical parameter and the state of charge, and the steady-state voltage equation of the battery equivalent circuit, the maximum overload power that the vanadium redox flow battery can support within the full state of charge range is determined.

[0007] According to the present invention, a method for evaluating the power overload capacity of a vanadium redox flow battery includes performing a power step test on the vanadium redox flow battery at multiple pre-selected state of charge points within the full state of charge range using a grid-connected power conversion system. The method comprises: For any of the stated states of charge, the grid-connected output power is increased to a preset rated value at a preset rate by the grid-connected power conversion system, so that the discharge power of the vanadium redox flow battery increases in a stepwise manner.

[0008] According to the present invention, a method for evaluating the power overload capacity of a vanadium redox flow battery includes inputting the voltage response curves and current response curves corresponding to each state of charge (SOC) into a Randle equivalent circuit model to identify the electrochemical parameters of the Randle equivalent circuit model at different SOCs, including: Based on the voltage response curve and the current response curve corresponding to each of the charging state points, the voltage and current data corresponding to each of the charging state points are obtained. An optimization problem is constructed with the model parameters of the Randles equivalent circuit model as optimization variables and the root mean square error between the model-predicted voltage sequence and the measured voltage sequence as the objective function; the Randles equivalent circuit model is a first-order equivalent circuit model that includes a series ohmic resistor and an RC loop composed of a charge transfer resistor and a double-layer capacitor connected in parallel. Based on the voltage and current data corresponding to each of the stated charge state points, an optimization algorithm is used to iteratively solve the optimization problem. By minimizing the root mean square error, the optimal estimated values ​​of the model parameters are determined. The optimal estimated values ​​of the model parameters represent the identified electrochemical parameters.

[0009] According to the present invention, a method for evaluating the power overload capacity of a vanadium redox flow battery includes constructing an optimization problem with the model parameters of the Randles equivalent circuit model as optimization variables and the root mean square error between the model-predicted voltage sequence and the measured voltage sequence as the objective function. Determine the model parameter vector to be optimized, wherein the model parameter vector to be optimized includes at least ohmic resistance, charge transfer resistance and double-layer capacitance; An objective function is established; the objective function is configured to calculate the root mean square error between the model-predicted voltage sequence and the measured voltage sequence given the model parameter vector; the model-predicted voltage sequence is obtained by solving the differential equation corresponding to the Randles equivalent circuit model based on the model parameter vector and the measured current sequence.

[0010] According to the present invention, a method for evaluating the power overload capacity of a vanadium redox flow battery includes a step of iteratively solving an optimization problem based on voltage and current data corresponding to each state of charge point, and determining the optimal estimated values ​​of the model parameters by minimizing the root mean square error. The method comprises: Generate an initial set of candidate solutions for the optimization algorithm; In each iteration, for each candidate solution in the current candidate solution set, the following steps are performed: using the model parameter values ​​and measured current data represented by the candidate solution, a circuit model simulation is performed to obtain the model predicted voltage corresponding to the candidate solution; the error between the model predicted voltage and the measured voltage corresponding to the candidate solution is calculated as the fitness value of the candidate solution; the current candidate solution set is updated according to the fitness values ​​of each candidate solution to generate candidate solutions for the next iteration; the measured current data and the measured voltage are determined based on the voltage and current data corresponding to each state of charge point; If the iteration termination condition is met, the model parameter value corresponding to the candidate solution with the highest fitness value is determined as the optimal estimate of the model parameters.

[0011] According to the present invention, a method for evaluating the power overload capacity of a vanadium redox flow battery includes, in which polynomial fitting is performed on each of the electrochemical parameters to establish a continuous functional relationship between each electrochemical parameter and the state of charge, comprising: For any of the electrochemical parameters, a fitting is performed starting from a first-order polynomial, and the coefficient of determination of the current polynomial is calculated. Under the condition that the preset conditions are met, the degree of the polynomial is increased and the fitting is performed again; the preset conditions are that the determination coefficient of the current polynomial is less than the preset precision threshold and the degree of the current polynomial has not reached the preset maximum degree. If the preset conditions are not met, the fitting is stopped and the polynomial with the largest coefficient of determination is selected as the continuous functional relationship expression between the electrochemical parameters and the state of charge.

[0012] According to the present invention, a method for evaluating the power overload capacity of a vanadium redox flow battery is provided, wherein the preset accuracy threshold is 0.9 and the preset maximum number of tests is three.

[0013] According to the present invention, a method for evaluating the power overload capacity of a vanadium redox flow battery includes determining the maximum overload power that the vanadium redox flow battery can support within the full state of charge range, based on the continuous functional relationship between each electrochemical parameter and the state of charge, and the steady-state voltage equation of the battery equivalent circuit. Based on the continuous functional relationship between each electrochemical parameter and the state of charge, combined with the steady-state voltage equation and the preset minimum safe voltage limit of the battery, the maximum overload power that the vanadium redox flow battery can support within the full state of charge range is calculated and output.

[0014] According to the present invention, a method for evaluating the power overload capacity of a vanadium redox flow battery is provided, wherein the minimum safe voltage limit of the battery is determined based on the electrochemical characteristics and long-term operating life requirements of the vanadium redox flow battery cells.

[0015] According to the present invention, a method for evaluating the power overload capacity of a vanadium redox flow battery is provided, wherein the maximum overload power that the vanadium redox flow battery can support within the full state of charge range is represented by a maximum overload power capacity curve; the method further includes: Based on the maximum overload power capability curve and the current state of charge of the vanadium redox flow battery monitored in real time, a first current limit is determined; the first current limit is used to ensure that the battery port voltage is not lower than the minimum safe voltage limit. Obtain a second current limit based on the converter's own device safety and grid connection specifications; In the operation control of the converter, the smaller value between the first current limit and the second current limit is used as the final output current limit value to achieve dual protection for the overload safety of the vanadium redox flow battery and the operation safety of the converter.

[0016] According to the present invention, a method for evaluating the power overload capacity of a vanadium redox flow battery is provided, the method further comprising: Based on the maximum overload power that the vanadium redox flow battery can support within the full state of charge range, power scheduling suggestions or overload protection thresholds for the vanadium redox flow battery under different real-time states of charge are generated.

[0017] Secondly, the present invention also provides a power overload capacity assessment device for a vanadium redox flow battery, the device comprising the following modules: The data acquisition module is used to perform a power step experiment on the vanadium redox flow battery at multiple pre-selected state of charge points within the full state of charge range through the grid-connected power conversion system, and simultaneously acquire the voltage response curve and the current response curve corresponding to each state of charge point during the discharge process of the vanadium redox flow battery. The parameter identification module is used to input the voltage response curves and current response curves corresponding to each of the stated states of charge into the Randles equivalent circuit model, and identify the electrochemical parameters of the Randles equivalent circuit model at different states of charge. The polynomial fitting module is used to perform polynomial fitting on each of the electrochemical parameters and establish a continuous functional relationship expression between each electrochemical parameter and the state of charge. The maximum overload power calculation module is used to determine the maximum overload power that the vanadium redox flow battery can support within the full state of charge range, based on the continuous functional relationship expression between each electrochemical parameter and the state of charge, and the steady-state voltage equation of the battery equivalent circuit.

[0018] Thirdly, the present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the power overload capacity assessment method of any of the above-described vanadium redox flow batteries.

[0019] Fourthly, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the power overload capacity assessment method for all-vanadium redox flow batteries as described above.

[0020] Fifthly, the present invention also provides a computer program product, including a computer program that, when executed by a processor, implements the power overload capacity assessment method for any of the above-described vanadium redox flow batteries.

[0021] This invention provides a method and apparatus for evaluating the power overload capacity of a vanadium redox flow battery. First, a power step experiment is performed on the vanadium redox flow battery at multiple pre-selected state of charge (SOC) points within the full SOC range using a grid-connected power conversion system. Simultaneously, voltage and current response curves corresponding to each SOC point are acquired during the discharge process. Then, the voltage and current response curves are input into a Randle equivalent circuit model to identify the electrochemical parameters of the Randle equivalent circuit model at different SOC points. Further, polynomial fitting is performed on each electrochemical parameter to establish a continuous functional relationship expression between each electrochemical parameter and the SOC. Finally, based on the continuous functional relationship expression between each electrochemical parameter and the SOC and the steady-state voltage equation of the battery equivalent circuit, the maximum overload power that the vanadium redox flow battery can support within the full SOC range is determined.

[0022] This invention performs a power step experiment on a vanadium redox flow battery at a typical state of charge (SOC) point, measuring the voltage-current curves. Equivalent parameters (electrochemical parameters) are identified using the Randle model, and a continuous mapping relationship between these parameters and SOC is constructed through polynomial fitting. Furthermore, the power overload capacity of the vanadium redox flow battery across the entire SOC range is evaluated based on the circuit's steady-state equation. This invention does not rely on empirical thresholds, has clear physical meaning, and enables accurate, continuous, and predictable evaluation of the power overload capacity of vanadium redox flow batteries, contributing to improved safety and dynamic response performance of flow battery systems under complex operating conditions. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a flowchart illustrating the power overload capacity assessment method for vanadium redox flow batteries provided by the present invention.

[0025] Figure 2 This is a schematic diagram of the Randle equivalent circuit model of the all-vanadium redox flow battery provided by the present invention.

[0026] Figure 3 This is a schematic diagram of the power overload capacity assessment device for vanadium redox flow batteries provided by the present invention.

[0027] Figure 4 This is a schematic diagram of the structure of the electronic device provided by the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0029] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first" and "second" are generally of the same class, not limited in number; for example, a first node can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0030] To address the aforementioned problems in the prior art, this invention proposes a method for evaluating the power overload capacity of vanadium redox flow batteries based on multi-SOC point experimental identification and parameter-SOC continuous modeling. Specifically, it provides a quantitative evaluation method for the power overload capacity of vanadium redox flow battery (VRFB) systems, applicable to the accurate modeling and safety threshold tuning of the dynamic limit power boundary of the battery under different states of charge (SOC). This method can provide a scientific basis for power scheduling, overload protection strategy formulation, and system-level dynamic response capability design of energy storage systems.

[0031] The following is combined with Figures 1 to 4 The present invention describes a method and apparatus for evaluating the power overload capacity of a vanadium redox flow battery.

[0032] Figure 1 This is a flowchart illustrating the power overload capacity assessment method for vanadium redox flow batteries provided by this invention, as shown below. Figure 1 As shown, the method includes the following: Step 101: Through the grid-connected power conversion system, perform a power step experiment on the vanadium redox flow battery at multiple pre-selected state of charge points within the full state of charge range, and simultaneously collect the voltage response curve and current response curve corresponding to each state of charge point during the discharge process of the vanadium redox flow battery.

[0033] Specifically, the subject of this invention is an electronic device, and the method provided in the embodiments of this invention aims to accurately quantify the power overload limit that a vanadium redox flow battery can withstand under different states of charge (SOC).

[0034] First, power step experiments were performed on the vanadium redox flow battery at multiple pre-selected state of charge points (e.g., typical SOC points, including 20%, 40%, 60%, and 80%) within the full state of charge range. In these power step experiments, the power increase rate was controlled by a grid-connected power conversion system (PCS) to simulate a sudden power surge in a real system.

[0035] In practical applications, the grid-connected output power is quickly increased to the preset rated value through the battery's grid-connected power conversion system (PCS), and the voltage and current response curves during the battery discharge process are collected simultaneously, with the data sampling rate set to be greater than or equal to 100Sa / s (samples / second).

[0036] Step 102: Input the voltage response curves and current response curves corresponding to each charge state point into the Randles equivalent circuit model to identify the electrochemical parameters of the Randles equivalent circuit model at different charge state points.

[0037] Specifically, after obtaining the voltage response curves and current response curves corresponding to each state of charge (SOC), the collected voltage and current data (voltage and current curves for different SOCs) are input into the Randles equivalent circuit model to identify the electrochemical parameters at all SOC points. These electrochemical parameters include: open-circuit voltage U. oc Ohmic resistance R0, charge transfer resistance R ct and double-layer capacitance C dl Key electrochemical parameters, including the open-circuit voltage U. oc The identification values ​​are the average voltage data before the disturbance, the ohmic resistance R0, and the charge transfer resistance R. ct and double-layer capacitance C dl The initial values ​​are (0.1 ohms, 0.1 ohms, 0.1 farads), and the initial value of the capacitor voltage is U. cdl0 =0.

[0038] Among them, the Randles equivalent circuit model provides the physical topology and vividly describes the physical and electrochemical processes inside the vanadium redox flow battery using specific connection methods of circuits (resistors and capacitors). Figure 2 This is a schematic diagram of the Randle equivalent circuit model of the all-vanadium redox flow battery provided by the present invention, as shown below. Figure 2 As shown, the model consists of a DC voltage source, an ohmic resistor, and an RC parallel network connected in series. Its output is connected to the grid side to simulate the external characteristics of a battery during grid-connected discharge. oc The open-circuit voltage of the battery is represented by an ohmic resistor R0 connected in series, and the RC parallel network includes the charge transfer resistor R. ct and double-layer capacitance C d1 .

[0039] In practical applications, the first-order RC differential equations corresponding to the Randles equivalent circuit model can be solved based on the initial values ​​of electrochemical parameters and voltage-current curves. These first-order RC differential equations are precise mathematical rules describing the dynamic behavior of the parallel RC branches in this model. The first-order RC differential equations translate the circuit topology into mathematical language that can be used for numerical calculation and analysis. Specifically, through the ohmic resistance R0 and the charge transfer resistance R... ct and double-layer capacitance C dl The parameter iteration minimizes the residual of the first-order differential equation of RC, and finally identifies the electrochemical parameters at different charge states.

[0040] Step 103: Perform polynomial fitting on each electrochemical parameter to establish a continuous functional relationship expression between each electrochemical parameter and the state of charge.

[0041] Specifically, after obtaining the various electrochemical parameters, the ohmic resistance R0 and charge transfer resistance R are then combined with these parameters. ct and double-layer capacitance C dl For the identification values ​​under different SOC states, polynomial fitting from first-order to third-order polynomials is performed to obtain a continuous functional relationship expression between each electrochemical parameter and the state of charge.

[0042] The final output, such as R0 (SOC), R ct (SOC), C dl The expression for the continuous functional relationship between (SOC) equivalent circuit parameters (electrochemical parameters) and SOC.

[0043] Step 104: Based on the continuous functional relationship between each electrochemical parameter and the state of charge, and the steady-state voltage equation of the battery equivalent circuit, determine the maximum overload power that the vanadium redox flow battery can support within the full state of charge range.

[0044] Specifically, this involves combining the circuit's steady-state equations with the preset minimum safe battery voltage constraint U. min Calculate the maximum overload power P that the battery can support across the entire SOC range. max (SOC) enables continuous quantitative assessment of overload capacity.

[0045] The specific calculation method is as follows: combining U oc R0, R ct The relationship with SOC, and U min With fixed parameters, the battery's ultimate overload current I can be calculated using formula (1). max Based on the relationship with SOC, the battery's ultimate overload power P can be calculated using formula (2). max .

[0046] (1) (2) in, Indicates the battery's maximum overload current. This indicates the preset minimum safe battery voltage limit. Indicates open-circuit voltage. Indicates ohmic resistance. Represents charge transfer resistance. This indicates the battery's maximum overload power.

[0047] For example, a specific set of system parameters is given: a vanadium redox flow battery system with a rated power of 10kW, consisting of 30 battery cells connected in series, and a minimum safe voltage constraint Umin of 30V. The specific implementation steps include the following: (1) Set the grid-connected PCS power command value to 10kW (kilowatt) at battery SOC=20%, 40%, 60% and 80% respectively, set the oscilloscope sampling rate to 1kSa / s (thousand samples per second), record the battery voltage and current for 50s before and after the disturbance, and save a total of 8 data curves.

[0048] (2) Based on the experimental curves of different SOCs, and combined with the battery Randle equivalent circuit model, parameter identification was performed, U oc The identification value is the average voltage data before the disturbance, specifying R0 and R. ct C dl The initial values ​​are (0.1Ω, 0.1Ω, 0.1F), and the initial value of the capacitor voltage is U. cdl0 =0, and the equivalent circuit parameters R0 and R are obtained by minimizing the residuals of the first-order RC differential equation. ct C dl The identification value.

[0049] (3) Combining the equivalent circuit parameters R0, R ct C dl The identification values ​​under different SOC states are subjected to polynomial fitting from first-order to third-order polynomials to obtain R0(SOC) and R... ct (SOC), C dl (SOC) Equivalent circuit parameters and functional expressions of SOC.

[0050] (4) Calculate the battery limit overload current under different SOC states according to the above formulas (1) and (2). and ultimate overload power .

[0051] The method provided in this embodiment first performs a power step experiment on a vanadium redox flow battery at multiple pre-selected state of charge (SOC) points within the full SOC range using a grid-connected power conversion system, and simultaneously acquires the voltage response curves and current response curves corresponding to each SOC point during the discharge process of the vanadium redox flow battery. Then, the voltage and current response curves corresponding to each SOC point are input into a Randle equivalent circuit model to identify the electrochemical parameters of the Randle equivalent circuit model at different SOC points. Further, polynomial fitting is performed on each electrochemical parameter to establish a continuous functional relationship expression between each electrochemical parameter and the SOC. Finally, based on the continuous functional relationship expression between each electrochemical parameter and the SOC and the steady-state voltage equation of the battery equivalent circuit, the maximum overload power that the vanadium redox flow battery can support within the full SOC range is determined.

[0052] This invention performs a power step experiment on a vanadium redox flow battery at a typical state of charge (SOC) point, measuring the voltage-current curves. Equivalent parameters (electrochemical parameters) are identified using the Randle model, and a continuous mapping relationship between these parameters and SOC is constructed through polynomial fitting. Furthermore, the power overload capacity of the vanadium redox flow battery across the entire SOC range is evaluated based on the circuit's steady-state equation. This invention does not rely on empirical thresholds, has clear physical meaning, and enables accurate, continuous, and predictable evaluation of the power overload capacity of vanadium redox flow batteries, contributing to improved safety and dynamic response performance of flow battery systems under complex operating conditions.

[0053] It should be noted that each implementation method of this application can be freely combined, rearranged, or executed individually, and does not need to rely on or depend on a fixed execution order.

[0054] According to the present invention, a method for evaluating the power overload capacity of a vanadium redox flow battery is provided, which involves performing a power step test on the vanadium redox flow battery at multiple pre-selected state of charge points within the full state of charge range using a grid-connected power conversion system, including: For any point of charge, the grid-connected output power is increased to a preset rated value at a preset rate through a grid-connected power conversion system, so that the discharge power of the vanadium redox flow battery increases in a stepwise manner.

[0055] Specifically, in some embodiments, step 101, which performs a power step experiment on the all-vanadium redox flow battery, is achieved through the following steps: The grid-connected power conversion system (PCS) is the core power electronic device connecting the energy storage battery and the AC power grid. In this invention, the PCS is the only operable actuator for the power step experiment.

[0056] In practical applications, the battery's power is indirectly increased at a certain rate by sending precise power control commands to the power control system (PCS). The PCS changes its output power by rapidly adjusting its internal power electronic switching devices (such as IGBTs), thereby forcing the directly connected battery to make a corresponding power response. Specifically, the core controller of the PCS, usually based on a digital signal processor (DSP) or a field-programmable gate array (FPGA), immediately activates its current control loop upon receiving the command. It calculates a new, larger current command value and rapidly drives the IGBTs and other switching transistors through pulse width modulation (PWM), ensuring that the output current (and power) on the AC side of the PCS strictly tracks the command.

[0057] According to the law of conservation of energy, the power output from the AC side of the PCS must be input from its DC side. Therefore, when the power on the AC side of the PCS increases suddenly, it must simultaneously and equally draw the corresponding power from its DC side, i.e., from the vanadium redox flow battery. This causes the discharge current flowing through the battery to increase sharply in a very short time, resulting in a "step" and almost instantaneous increase in the battery's discharge power. This is precisely the "power step disturbance" required for the experiment.

[0058] Furthermore, while the PCS is operating, a high-precision data acquisition device (such as an oscilloscope or a high-speed acquisition card) can be used to simultaneously record the voltage across the battery and the current flowing through the battery at a rate of no less than 100 samples per second, thereby generating voltage and current curves under different states of charge.

[0059] The method provided in this embodiment creates a power demand step on the grid side by precisely controlling the rapid opening and closing of the PCS (Power Control System), a "power valve," thereby eliciting an observable and measurable electrochemical dynamic response on the battery side. This method ingeniously transforms a complex electrochemical test into a standard and controllable power electronic control action.

[0060] According to the power overload capacity assessment method of a vanadium redox flow battery provided by the present invention, the voltage response curves and current response curves corresponding to each state of charge are input into the Randle equivalent circuit model to identify the electrochemical parameters of the Randle equivalent circuit model at different states of charge, including: Based on the voltage response curve and the current response curve corresponding to each charge state point, the voltage and current data corresponding to each charge state point are obtained. An optimization problem is constructed with the model parameters of the Randles equivalent circuit model as optimization variables and the root mean square error between the model-predicted voltage sequence and the measured voltage sequence as the objective function. The Randles equivalent circuit model is a first-order equivalent circuit model that includes a series ohmic resistor and an RC loop consisting of a charge transfer resistor and a double-layer capacitor connected in parallel. An optimization algorithm is used to iteratively solve the optimization problem. By minimizing the root mean square error, the optimal estimates of the model parameters are determined. The optimal estimates of the model parameters represent the identified electrochemical parameters.

[0061] Specifically, in some embodiments, step 102 identifies the electrochemical parameters of the Randles equivalent circuit model at different charge states, which is achieved through the following steps: First, the process of identifying electrochemical parameters is constructed as a nonlinear optimization problem with model parameters as optimization variables and the deviation between model output and measured data as the objective function.

[0062] The Randles equivalent circuit model is a first-order equivalent circuit model that includes a series ohmic resistor and an RC loop consisting of a charge transfer resistor and a double-layer capacitor connected in parallel. The Randles model is typically represented as follows: The voltage equation is expressed as follows: U(t) = U oc -I(t)*R0-U c (t) (3) RC loop differential equation: dU c / dt=I(t) / C dl -U c (t) / (R ct *C dl (4) Where U(t) and I(t) represent the battery terminal voltage and current measured at time t (the inputs to the model), and the parameters to be identified include the open-circuit voltage. Ohmic resistance R0, charge transfer resistance R ct Double-layer capacitance C dl U c (t) is the voltage across the RC loop capacitor, which is an internal state variable.

[0063] In practical applications, formalizing the parameter identification problem as an optimization problem includes the following: determining the optimization variables (decision variables) and the objective function. The optimization variables (decision variables) are, for example, the parameter vector θ = [R0, R...]. ct C dl U oc ]. (U oTypically, the value can also be obtained directly by averaging the steady-state voltage before the disturbance, thus reducing the number of optimization variables. The objective function F(θ) is used to measure the error between the model output and the measured data. For example, the root mean square error. The goal of the optimization problem is to find a set of parameters θ* that minimizes the objective function F(θ).

[0064] Furthermore, based on the voltage and current data corresponding to each charge state point, an optimization algorithm is used to iteratively solve the optimization problem. By minimizing the root mean square error, the optimal estimated values ​​of the model parameters are determined, that is, the identified electrochemical parameters.

[0065] The method provided in this embodiment transforms parameter identification of the Randle equivalent circuit model into an optimization problem. An optimization algorithm is then used to iteratively minimize the error between the model output and the measured data, thereby determining the model parameters and ensuring the objectivity and accuracy of the identification.

[0066] According to the present invention, a method for evaluating the power overload capacity of a vanadium redox flow battery is provided, which constructs an optimization problem with the model parameters of the Randle equivalent circuit model as optimization variables and the root mean square error between the model-predicted voltage sequence and the measured voltage sequence as the objective function, including: Determine the model parameter vector to be optimized. The model parameter vector to be optimized shall include at least ohmic resistance, charge transfer resistance and double layer capacitance. Establish an objective function; the objective function is configured to calculate the root mean square error between the model-predicted voltage sequence and the measured voltage sequence given the model parameter vector; the model-predicted voltage sequence is obtained by solving the differential equation corresponding to the Randles equivalent circuit model based on the model parameter vector and the measured current sequence.

[0067] Specifically, first determine the optimization variables (decision variables), that is, determine the parameter vector θ=[R0, R] that needs to be found. ct C dl U oc ]. (U o This can usually be obtained directly by averaging the steady-state voltage before the disturbance, thus reducing the number of optimization variables. Therefore, the optimization variables are expressed as θ=[R0, R... ct C dl ].

[0068] Next, determine the objective function, such as the root mean square error. The objective function is expressed as follows: F(θ) = sqrt(mean((U) measured (t)-U model (t,θ)) 2 )) (5) Where F(θ) represents the objective function with θ as the optimization variable, U measured (t) represents the collected measured voltage sequence, U model (t,θ) represents the model-predicted voltage sequence calculated by solving the above differential equation using the current parameter θ and the measured current I(t).

[0069] The method provided in this embodiment transforms the parameter identification of the Randle equivalent circuit model into an optimization problem, which facilitates the solution and improves the objectivity and accuracy of the identification.

[0070] According to the present invention, a method for evaluating the power overload capacity of a vanadium redox flow battery is provided. Based on the voltage and current data corresponding to each state of charge, an optimization algorithm is used to iteratively solve the optimization problem. By minimizing the root mean square error, the optimal estimated values ​​of the model parameters are determined, including: Generate an initial set of candidate solutions for the optimization algorithm; In each iteration, for each candidate solution in the current candidate solution set, the following steps are performed: using the model parameter values ​​and measured current data represented by the candidate solution, a circuit model simulation is performed to obtain the model predicted voltage corresponding to the candidate solution; the error between the model predicted voltage and the measured voltage corresponding to the candidate solution is calculated as the fitness value of the candidate solution; the current candidate solution set is updated according to the fitness value of each candidate solution to generate the candidate solution for the next iteration; the measured current data and the measured voltage are determined based on the voltage and current data corresponding to each state of charge point; If the iteration termination condition is met, the model parameter value corresponding to the candidate solution with the highest fitness value is determined as the optimal estimate of the model parameters.

[0071] Specifically, in some embodiments, the process of iteratively solving the optimization problem using an optimization algorithm includes the following steps: (1) Initialization step: Generate an initial candidate solution set for the optimization algorithm. Each candidate solution in the set represents a model parameter vector θ, which includes at least the ohmic resistance R0 and the charge transfer resistance R... ct and double-layer capacitance C dl The initial candidate solution set includes the initial values ​​of the model parameter vector θ.

[0072] (2) Iterative evaluation and update steps: In each iteration, the following steps are performed for each candidate solution in the current candidate solution set: Forward computation sub-step: Using the model parameter values ​​represented by the candidate solutions and the measured current data, a circuit model simulation is performed to obtain the model predicted voltage corresponding to the candidate solutions. Specifically, in this forward computation sub-step, the first-order differential equation of the Randles equivalent circuit model is solved using numerical integration to obtain the model predicted voltage corresponding to the candidate solutions.

[0073] Fitness evaluation sub-step: Calculate the error between the model-predicted voltage and the measured voltage corresponding to the candidate solution, and use it as the fitness value of the candidate solution.

[0074] Update steps: Update the current set of candidate solutions based on the fitness values ​​of each candidate solution, and generate candidate solutions for the next iteration.

[0075] (3) Termination and Output Steps: If the iteration termination condition is met, the model parameter value corresponding to the candidate solution with the highest fitness value is determined as the optimal estimate of the model parameters and output as the identification result. The iteration termination condition is if it is greater than or equal to the preset number of iterations, or if the minimum root mean square error is met.

[0076] The optimization algorithm is a swarm intelligence optimization algorithm, specifically a particle swarm optimization algorithm or a genetic algorithm. When the swarm intelligence optimization algorithm is a particle swarm optimization algorithm, the candidate solution set is a swarm of particles, each candidate solution represents the position of a particle, and the fitness value is the fitness of that particle; the update step updates the particle's velocity and position based on the particle's historical best position and the swarm's global best position. When the swarm intelligence optimization algorithm is a genetic algorithm, the candidate solution set is a population, each candidate solution represents an individual, and the fitness value is the fitness of that individual; the update step includes selection, crossover, and mutation operations based on fitness to generate a new generation of the population.

[0077] The following section uses the Particle Swarm Optimization (PSO) algorithm as an example to explain in detail how to use the PSO algorithm to solve optimization problems: Step 1: Initialization Set PSO parameters: number of particles (e.g., 50), maximum number of iterations, inertia weight, etc.

[0078] For each parameter to be identified (R0, R ct C dl Set a reasonable physical range.

[0079] Generate initial particle swarm: Within a preset parameter range, randomly generate N particles. The position X of each particle... i Represents a set of parameter guess values ​​[R] 0i ,Rct i C dli At the same time, a velocity V is randomly initialized for it. i .

[0080] Each particle records its individual historical best position P. besti And the corresponding optimal fitness value (i.e., the minimum objective function value). The global optimal position G of the entire particle swarm is recorded globally.best .

[0081] Step 2: Iteration loop (for each iteration) For each particle i in the particle swarm: 1. Model Solving (Forward Computation): Input: The particle's current position X i (i.e., a set of parameters) and measured current data I(t).

[0082] Process: Using X i The parameters are used to numerically solve the differential equations of the Randle model (e.g., using the Euler method or the Runge-Kutta method) to calculate the model-predicted voltage U for the entire time series from the start to the end of the experiment. model i(t).

[0083] Output: Predicted voltage sequence U model i(t).

[0084] 2. Calculate fitness (evaluation): Predicted voltage U model i(t) and measured voltage U measured (t) is compared.

[0085] Calculate the fitness value of the particle, i.e., the objective function value F(X). i =RMSE(U model i,U measured ).

[0086] 3. Update individual and global optimum: Compare the current fitness F(X) i ) and the particle's historical best fitness F(P) besti If F(X) i ) <F(P besti If P is updated, then P is updated. besti =X i .

[0087] 4. Update particle state (move): Calculate the particle's new velocity V using the PSO velocity-position update formula. inew And the new location X inew Ensure X inew It does not exceed the physical boundaries preset by the parameters.

[0088] Step 3: Termination and Output Repeat step two until the maximum number of iterations is reached, or the change in the global optimal fitness value is less than a certain threshold.

[0089] After the iteration, the global optimal position G is found. bestThat is, the optimal parameter set [R0*, R] obtained by identification. ct *,C dl *].

[0090] The global optimal fitness value F(G) at this time best The value represents the best accuracy of the model fit.

[0091] The method provided in this embodiment automatically and systematically searches the parameter space through an optimized algorithm to find the set of electrochemical parameters that best matches the dynamic model output with complex transient measured data, thereby avoiding manual trial and error and ensuring the objectivity and accuracy of the identification.

[0092] According to the power overload capacity assessment method for a vanadium redox flow battery provided by the present invention, polynomial fitting is performed on each electrochemical parameter to establish a continuous functional relationship expression between each electrochemical parameter and the state of charge, including: For any electrochemical parameter, a fitting is performed starting from a first-order polynomial, and the coefficient of determination of the current polynomial is calculated. If the preset conditions are met, the degree of the polynomial is increased and the fitting is performed again; the preset conditions are that the determination coefficient of the current polynomial is less than the preset precision threshold and the degree of the current polynomial has not reached the preset maximum degree. If the preset conditions are not met, the fitting is stopped and the polynomial with the largest coefficient of determination is selected as the continuous functional relationship expression between electrochemical parameters and charge state.

[0093] Specifically, in some embodiments, step 103 is implemented in the following manner, including: Taking the fitting of a certain equivalent parameter (electrochemical parameter R0) as an example: The fitting process begins with a first-order polynomial, first calculating the coefficients of determination of the current polynomial. Coefficient of determination The coefficient of determination is a core metric for measuring the goodness of fit of a regression model (such as a polynomial), that is, it is used to judge how well the polynomial function fits the model. The core formula is as follows: (6) in, As the coefficient of determination, The sum of squared residuals measures the difference between the model prediction of an electrochemical parameter (e.g., the predicted R0 at 40% SOC) and the actual value of the electrochemical parameter (e.g., the R0 calculated using a fitted polynomial formula at 40% SOC). The total sum of squares measures the dispersion of the true data (such as the R0 value calculated using a fitted polynomial formula at 40% SOC) around the mean of all true values.

[0094] Then, based on the coefficients of determination of the current polynomial... Determine the fit and make the next decision: like : Indicates a perfect fit. The model explains all the variations in the data.

[0095] like The model fits the data exactly as it would have predicted using the mean. The model provides no explanation beyond the mean.

[0096] like < < : The closer the value is to 1, the higher the proportion of data variation explained by the model, and the better the fit.

[0097] like < This only occurs when the model fits extremely poorly, worse than predicting directly using the average (indicating the model is completely wrong).

[0098] The coefficients of determination of the current polynomial Less than the preset precision threshold (e.g.) And the current polynomial degree has not reached the preset maximum degree (e.g., polynomial degree). In case 3), increase the polynomial degree and refit, for example, continue to increase the polynomial degree to 1.

[0099] Conversely, if the above conditions are not met, the fitting process is stopped, and the coefficient of determination R in the above process is taken. 2 The largest polynomial is used as the fitting result for this parameter to establish a continuous functional relationship between the electrochemical parameter and SOC.

[0100] The method provided in this embodiment performs polynomial fitting on the relationship between each electrochemical parameter obtained from different SOC identifications and SOC, establishing a continuous functional relationship expression between them and SOC. Then, by combining the circuit steady-state voltage equation and the preset minimum safe voltage constraint of the battery, the maximum overload power P that the battery can support across the entire SOC range can be solved. max (SOC) enables accurate, continuous, and predictable assessment of battery power overload capacity.

[0101] According to the present invention, a method for evaluating the power overload capacity of a vanadium redox flow battery is provided, with a preset accuracy threshold of 0.9 and a preset maximum number of tests of three.

[0102] In some embodiments, the preset accuracy threshold is 0.9, and the preset maximum number of iterations is three. The preset accuracy threshold and the preset maximum number of iterations can be determined according to actual needs. A higher preset accuracy threshold and a higher preset maximum number of iterations indicate a higher requirement for the model fitting effect.

[0103] The method provided in this embodiment constructs an automated convergence mechanism with clear technical judgment criteria for the entire "electrochemical parameter-SOC relationship modeling" step, ensuring a lower limit of fitting accuracy, preventing excessive model complexity (overfitting), and achieving automation and objectivity in the modeling process. This strategy can automatically generate a continuous "electrochemical parameter-SOC" model that achieves the best balance between fitting accuracy, model simplicity, and physical rationality. This model is used for subsequent accurate calculation of the maximum overload power P across the entire SOC range. max The reliable mathematical foundation of (SOC) fundamentally improves the accuracy, security, and engineering practicality of the entire evaluation method.

[0104] According to the present invention, a method for evaluating the power overload capacity of a vanadium redox flow battery, based on the continuous functional relationship between various electrochemical parameters and the state of charge and the steady-state voltage equation of the battery equivalent circuit, determines the maximum overload power that the vanadium redox flow battery can support across the entire state of charge range, including: Based on the continuous functional relationship between various electrochemical parameters and state of charge, combined with the steady-state voltage equation and the preset minimum safe voltage limit of the battery, the maximum overload power that the vanadium redox flow battery can support within the full state of charge range is calculated and output.

[0105] Specifically, in some embodiments, a preset minimum safe battery voltage limit U min The minimum safe voltage constraint is determined based on the electrochemical characteristics and long-term operational life requirements of the vanadium redox flow battery cells. For example, a vanadium redox flow battery system with a rated power of 10 kW consists of 30 cells connected in series. The minimum safe voltage limit U of the battery is... min It is 30V.

[0106] In practical applications, the maximum overload power that a full vanadium redox flow battery can support within the full state of charge range is calculated and output through the following steps: combining the circuit steady-state voltage equation Compared with the preset minimum safe battery voltage constraint (preset minimum safe battery voltage limit) U min Solve for the maximum overload power P that the battery can support across the entire SOC range. max (SOC) enables continuous quantitative assessment of overload capacity. The specific calculation method is as follows: combining U... oc R0, R ct The relationship with SOC, and U minWith fixed parameters, the battery's ultimate overload current I can be calculated using formula (1). max Based on the relationship with SOC, the battery's ultimate overload power P can be calculated using formula (2). max .

[0107] (1) (2) in, Indicates the battery's maximum overload current. This indicates the preset minimum safe battery voltage limit. Indicates open-circuit voltage. Indicates ohmic resistance. Represents charge transfer resistance. This indicates the battery's maximum overload power.

[0108] The method provided in this embodiment combines the circuit steady-state voltage equation with a preset minimum safe voltage constraint for the battery to solve for the maximum overload power P that the battery can support across the entire SOC range. max (SOC) enables continuous quantitative assessment of overload capacity.

[0109] According to the present invention, a method for evaluating the power overload capacity of a vanadium redox flow battery is provided, wherein the maximum overload power that the vanadium redox flow battery can support within the full state of charge range is represented by a maximum overload power capacity curve; the method further includes: The first current limit is determined based on the maximum overload power capability curve and the current state of charge of the vanadium redox flow battery under real-time monitoring; the first current limit is used to ensure that the battery port voltage is not lower than the minimum safe voltage limit. Obtain a second current limit based on the converter's own device safety and grid connection specifications; In the operation control of the converter, the smaller value between the first current limit and the second current limit is used as the final output current limit value to achieve dual protection for the overload safety of the vanadium redox flow battery and the operation safety of the converter.

[0110] Specifically, the method further includes a dual protection step: First, the first current limit is determined based on the maximum overload power (maximum overload power capability curve) that the vanadium redox flow battery can support within the full state of charge range and the current state of charge of the vanadium redox flow battery monitored in real time.

[0111] This step is a dynamic process involving querying, calculation, and security applications, with the core being the conversion of power boundaries into current boundaries. The first current limit ensures that the battery port voltage does not fall below the minimum safe voltage limit, based on the power formula P=U×I, where P represents power, U represents voltage, and I represents current. Therefore, the current limit is obtained by dividing the power limit by a voltage parameter. The key to implementation lies in the selection of the voltage parameter, which is typically the real-time port voltage, the battery's rated voltage, or the open-circuit voltage corresponding to the current state of charge (SOC).

[0112] In practical applications, the maximum overload power capability curve Pmax(SOC) of the vanadium redox flow battery is first obtained, and the current state of charge (SOC) of the battery is monitored in real time. act Then based on Pmax(SOC) and SOC act This allows us to determine the current maximum allowable overload power value Pmax. act Furthermore, based on the current maximum permissible overload power value Pmax_—_ act Using a voltage parameter, the first current limit I is calculated. limit1 .

[0113] Then, obtain the second current limit I based on the converter's own device safety and grid connection specifications. limit2 The safety of a converter itself is determined by its hardware characteristics, such as the maximum allowable current-carrying capacity of its core power devices and the design limits of its heat dissipation system. Grid connection specifications are stipulated by the grid regulations, standards, or agreements at the grid connection point, typically specifying the maximum allowable injection current to ensure the safety and stability of the grid.

[0114] Ultimately, in the operation control of the converter, the first current limit I is adopted. limit1 With the second current limit I limit2 The smaller value in the range is used as the final output current limit to achieve dual protection for both overload safety of the vanadium redox flow battery and converter operation safety. That is, the dynamic limit (I0) characterizing the internal electrochemical safety boundary of the battery is used as the final output current limit. limit1 ), and static / regulatory limits (I) to ensure the safety of power electronic devices and power grids. limit2 It performs a real-time comparison and takes the more stringent one as the final execution instruction.

[0115] The method provided in this embodiment creatively combines a second current limit based on the safety of the converter's own components and grid connection specifications with a dynamic limit calculated by the battery model, forming a new "dual current limiting" control decision-making method. This simultaneously safeguards the safety of both the battery itself and the power conversion system, improving the overall reliability of the entire energy storage system. This method can provide a scientific basis for the design, protection strategy formulation, and power scheduling of all-vanadium redox flow battery systems, helping to improve system safety and dynamic response capabilities.

[0116] According to the present invention, a method for evaluating the power overload capacity of a vanadium redox flow battery is provided, the method further comprising: Based on the maximum overload power that the vanadium redox flow battery can support within the full state of charge range, power scheduling suggestions or overload protection thresholds for the vanadium redox flow battery under different real-time states of charge are generated.

[0117] Specifically, in some embodiments, the method further includes: After generating the maximum overload power Pmax(SOC) that the vanadium redox flow battery can support within the full state of charge range, power scheduling suggestions or overload protection thresholds for the vanadium redox flow battery under different real-time states of charge can be generated based on the maximum overload power that the vanadium redox flow battery can support within the full state of charge range.

[0118] Power dispatch recommendations refer to reference values ​​provided by the energy management system (EMS) or upper-level dispatch center of the energy storage system regarding the safe power output range of the battery in the current and short-term future. They serve as a guiding and forward-looking signal to optimize the system's charge and discharge plans, ensuring that the battery responds to grid demands within safe boundaries. Specific content and forms include real-time available power, power regulation margin, and future power capacity predictions.

[0119] In practical applications, scenarios include: when the power grid needs an energy storage system to provide frequency regulation backup, the EMS can query the current P max (SOC) is used to determine whether there is sufficient reserve capacity available for deployment. For example, when formulating day-ahead or real-time generation plans, P... max (SOC) serves as a constraint to avoid scheduling power output plans that exceed the battery's safe capacity.

[0120] Overload protection threshold refers to a hard safety limit set in the protection circuit of the battery management system (BMS) or power conversion system (PCS) to trigger emergency actions (such as power limiting or tripping). It is a mandatory, real-time protection measure that activates immediately when power or current exceeds the threshold to prevent battery damage. Specific content and forms include: Power protection threshold: directly in P max(SOC) is used as a threshold. When the real-time discharge power exceeds this value, the power reduction or shutdown protection is triggered.

[0121] Current protection threshold: As mentioned before, set P max (SOC) is converted into a current limit value, which is used as the current loop limit value or protection setting value.

[0122] Voltage protection threshold: via P max The minimum allowable voltage can be derived from the (SOC) and model, and can also be used as a voltage protection reference.

[0123] In practical applications, scenarios include: in the current control loop of a PCS, using the current limit as a dynamic limiting value to ensure that the output current does not cause battery overload. Another example is in a BMS, where power overload alarms and trip thresholds are set; when the measured power exceeds P... max (SOC) After a certain time or amplitude, an alarm will be issued or the circuit will be cut off.

[0124] The method provided in this embodiment embodies a dual application from "evaluation model" to "operation optimization" and "security protection", thus improving its practicality.

[0125] The following describes the power overload capacity assessment device for vanadium redox flow batteries provided by the present invention. The power overload capacity assessment device for vanadium redox flow batteries described below can be referred to in correspondence with the power overload capacity assessment method for vanadium redox flow batteries described above.

[0126] Figure 3 This is a schematic diagram of the power overload capacity assessment device for vanadium redox flow batteries provided by the present invention, as shown in the figure. Figure 3 As shown, the power overload capacity assessment device 300 for the all-vanadium redox flow battery includes the following modules: The data acquisition module 310 is used to perform a power step experiment on the vanadium redox flow battery at multiple pre-selected state of charge points within the full state of charge range through a grid-connected power conversion system, and simultaneously acquire the voltage response curve and the current response curve corresponding to each state of charge point during the discharge process of the vanadium redox flow battery. The parameter identification module 320 is used to input the voltage response curve and the current response curve corresponding to each of the charging state points into the Randles equivalent circuit model, and identify the electrochemical parameters of the Randles equivalent circuit model at different charging state points. The polynomial fitting module 330 is used to perform polynomial fitting on each of the electrochemical parameters and establish a continuous functional relationship expression between each of the electrochemical parameters and the state of charge. The maximum overload power calculation module 340 is used to determine the maximum overload power that the vanadium redox flow battery can support within the full state of charge range based on the continuous functional relationship expression between each electrochemical parameter and the state of charge and the steady-state voltage equation of the battery equivalent circuit.

[0127] This invention performs a power step experiment on a vanadium redox flow battery at a typical state of charge (SOC) point, measuring the voltage-current curves. Equivalent parameters (electrochemical parameters) are identified using the Randle model, and a continuous mapping relationship between these parameters and SOC is constructed through polynomial fitting. Furthermore, the power overload capacity of the vanadium redox flow battery across the entire SOC range is evaluated based on the circuit's steady-state equation. This invention does not rely on empirical thresholds, has clear physical meaning, and enables accurate, continuous, and predictable evaluation of the power overload capacity of vanadium redox flow batteries, contributing to improved safety and dynamic response performance of flow battery systems under complex operating conditions.

[0128] According to the present invention, a power overload capacity assessment device 300 for a vanadium redox flow battery is provided, wherein the data acquisition module 310 is specifically used for: For any of the stated states of charge, the grid-connected output power is increased to a preset rated value at a preset rate by the grid-connected power conversion system, so that the discharge power of the vanadium redox flow battery increases in a stepwise manner.

[0129] According to the present invention, a power overload capacity assessment device 300 for a vanadium redox flow battery is provided, wherein the parameter identification module 320 is specifically used for: Based on the voltage response curve and the current response curve corresponding to each of the charging state points, the voltage and current data corresponding to each of the charging state points are obtained. An optimization problem is constructed with the model parameters of the Randles equivalent circuit model as optimization variables and the root mean square error between the model-predicted voltage sequence and the measured voltage sequence as the objective function; the Randles equivalent circuit model is a first-order equivalent circuit model that includes a series ohmic resistor and an RC loop composed of a charge transfer resistor and a double-layer capacitor connected in parallel. Based on the voltage and current data corresponding to each of the stated charge state points, an optimization algorithm is used to iteratively solve the optimization problem. By minimizing the root mean square error, the optimal estimated values ​​of the model parameters are determined. The optimal estimated values ​​of the model parameters represent the identified electrochemical parameters.

[0130] According to the present invention, a power overload capacity assessment device 300 for a vanadium redox flow battery is provided, wherein the parameter identification module 320 is further used for: Determine the model parameter vector to be optimized, wherein the model parameter vector to be optimized includes at least ohmic resistance, charge transfer resistance and double-layer capacitance; An objective function is established; the objective function is configured to calculate the root mean square error between the model-predicted voltage sequence and the measured voltage sequence given the model parameter vector; the model-predicted voltage sequence is obtained by solving the differential equation corresponding to the Randles equivalent circuit model based on the model parameter vector and the measured current sequence.

[0131] According to the present invention, a power overload capacity assessment device 300 for a vanadium redox flow battery is provided, wherein the parameter identification module 320 is further used for: Generate an initial set of candidate solutions for the optimization algorithm; In each iteration, for each candidate solution in the current candidate solution set, the following steps are performed: using the model parameter values ​​and measured current data represented by the candidate solution, a circuit model simulation is performed to obtain the model predicted voltage corresponding to the candidate solution; the error between the model predicted voltage and the measured voltage corresponding to the candidate solution is calculated as the fitness value of the candidate solution; the current candidate solution set is updated according to the fitness values ​​of each candidate solution to generate candidate solutions for the next iteration; the measured current data and the measured voltage are determined based on the voltage and current data corresponding to each state of charge point; If the iteration termination condition is met, the model parameter value corresponding to the candidate solution with the highest fitness value is determined as the optimal estimate of the model parameters.

[0132] According to the present invention, a power overload capacity assessment device 300 for a vanadium redox flow battery is provided, wherein the polynomial fitting module 330 is specifically used for: For any of the electrochemical parameters, a fitting is performed starting from a first-order polynomial, and the coefficient of determination of the current polynomial is calculated. Under the condition that the preset conditions are met, the degree of the polynomial is increased and the fitting is performed again; the preset conditions are that the determination coefficient of the current polynomial is less than the preset precision threshold and the degree of the current polynomial has not reached the preset maximum degree. If the preset conditions are not met, the fitting is stopped and the polynomial with the largest coefficient of determination is selected as the continuous functional relationship expression between the electrochemical parameters and the state of charge.

[0133] According to the present invention, a power overload capacity assessment device 300 for a vanadium redox flow battery has a preset accuracy threshold of 0.9 and a preset maximum number of tests of three.

[0134] According to the present invention, a power overload capacity assessment device 300 for a vanadium redox flow battery is provided, wherein the maximum overload power calculation module 340 is specifically used for: Based on the continuous functional relationship between each electrochemical parameter and the state of charge, combined with the steady-state voltage equation and the preset minimum safe voltage limit of the battery, the maximum overload power that the vanadium redox flow battery can support within the full state of charge range is calculated and output.

[0135] According to the present invention, a power overload capacity assessment device 300 for a vanadium redox flow battery is provided, wherein the minimum safe voltage limit of the battery is determined based on the electrochemical characteristics and long-term operating life requirements of the vanadium redox flow battery cell.

[0136] According to the present invention, a power overload capacity evaluation device 300 for a vanadium redox flow battery is provided, wherein the maximum overload power that the vanadium redox flow battery can support within the full state of charge range is represented by a maximum overload power capacity curve; the device further includes a dual protection module; The dual protection module is used for: Based on the maximum overload power capability curve and the current state of charge of the vanadium redox flow battery monitored in real time, a first current limit is determined; the first current limit is used to ensure that the battery port voltage is not lower than the minimum safe voltage limit. Obtain a second current limit based on the converter's own device safety and grid connection specifications; In the operation control of the converter, the smaller value between the first current limit and the second current limit is used as the final output current limit value to achieve dual protection for the overload safety of the vanadium redox flow battery and the operation safety of the converter.

[0137] According to the present invention, a power overload capacity assessment device 300 for a vanadium redox flow battery is provided, the device further comprising a power scheduling module; The power scheduling module is used for: Based on the maximum overload power that the vanadium redox flow battery can support within the full state of charge range, power scheduling suggestions or overload protection thresholds for the vanadium redox flow battery under different real-time states of charge are generated.

[0138] Figure 4 This is a schematic diagram of the structure of the electronic device provided by the present invention, such as... Figure 4 As shown, the electronic device may include: a processor 410, a communication interface 420, a memory 430, and a communication bus 440, wherein the processor 410, the communication interface 420, and the memory 430 communicate with each other via the communication bus 440. The processor 410 can call logic instructions in the memory 430 to execute a power overload capacity assessment method for a vanadium redox flow battery, the method including: Through a grid-connected power conversion system, a power step experiment is performed on the vanadium redox flow battery at multiple pre-selected state of charge points within the full state of charge range, and the voltage response curve and current response curve corresponding to each state of charge point are collected simultaneously during the discharge process of the vanadium redox flow battery. The voltage response curves and current response curves corresponding to each of the stated charge state points are input into the Randles equivalent circuit model to identify the electrochemical parameters of the Randles equivalent circuit model at different charge state points. Polynomial fitting was performed on each of the electrochemical parameters to establish a continuous functional relationship between each electrochemical parameter and the state of charge. Based on the continuous functional relationship between each electrochemical parameter and the state of charge, and the steady-state voltage equation of the battery equivalent circuit, the maximum overload power that the vanadium redox flow battery can support within the full state of charge range is determined.

[0139] Furthermore, the logical instructions in the aforementioned memory 430 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0140] On the other hand, the present invention also provides a computer program product, the computer program product comprising a computer program that can be stored on a non-transitory computer-readable storage medium, wherein when the computer program is executed by a processor, the computer is capable of executing the power overload capacity assessment method for vanadium redox flow batteries provided by the above methods, the method comprising: Through a grid-connected power conversion system, a power step experiment is performed on the vanadium redox flow battery at multiple pre-selected state of charge points within the full state of charge range, and the voltage response curve and current response curve corresponding to each state of charge point are collected simultaneously during the discharge process of the vanadium redox flow battery. The voltage response curves and current response curves corresponding to each of the stated charge state points are input into the Randles equivalent circuit model to identify the electrochemical parameters of the Randles equivalent circuit model at different charge state points. Polynomial fitting was performed on each of the electrochemical parameters to establish a continuous functional relationship between each electrochemical parameter and the state of charge. Based on the continuous functional relationship between each electrochemical parameter and the state of charge, and the steady-state voltage equation of the battery equivalent circuit, the maximum overload power that the vanadium redox flow battery can support within the full state of charge range is determined.

[0141] In another aspect, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements a method for evaluating the power overload capacity of a vanadium redox flow battery provided by the methods described above, the method comprising: Through a grid-connected power conversion system, a power step experiment is performed on the vanadium redox flow battery at multiple pre-selected state of charge points within the full state of charge range, and the voltage response curve and current response curve corresponding to each state of charge point are collected simultaneously during the discharge process of the vanadium redox flow battery. The voltage response curves and current response curves corresponding to each of the stated charge state points are input into the Randles equivalent circuit model to identify the electrochemical parameters of the Randles equivalent circuit model at different charge state points. Polynomial fitting was performed on each of the electrochemical parameters to establish a continuous functional relationship between each electrochemical parameter and the state of charge. Based on the continuous functional relationship between each electrochemical parameter and the state of charge, and the steady-state voltage equation of the battery equivalent circuit, the maximum overload power that the vanadium redox flow battery can support within the full state of charge range is determined.

[0142] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0143] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0144] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for evaluating the power overload capacity of an all-vanadium redox flow battery, characterized in that, include: Through a grid-connected power conversion system, a power step experiment is performed on the vanadium redox flow battery at multiple pre-selected state of charge points within the full state of charge range, and the voltage response curve and current response curve corresponding to each state of charge point are collected simultaneously during the discharge process of the vanadium redox flow battery. The voltage response curves and current response curves corresponding to each of the stated charge state points are input into the Randles equivalent circuit model to identify the electrochemical parameters of the Randles equivalent circuit model at different charge state points. Polynomial fitting was performed on each of the electrochemical parameters to establish a continuous functional relationship between each electrochemical parameter and the state of charge. Based on the continuous functional relationship between each electrochemical parameter and the state of charge, and the steady-state voltage equation of the battery equivalent circuit, the maximum overload power that the vanadium redox flow battery can support within the full state of charge range is determined.

2. The method for evaluating the power overload capacity of a vanadium redox flow battery according to claim 1, characterized in that, The process of performing a power step experiment on a vanadium redox flow battery at multiple pre-selected state of charge points within the full state of charge range via a grid-connected power conversion system includes: For any of the stated states of charge, the grid-connected output power is increased to a preset rated value at a preset rate by the grid-connected power conversion system, so that the discharge power of the vanadium redox flow battery increases in a stepwise manner.

3. The method for evaluating the power overload capacity of a vanadium redox flow battery according to claim 1, characterized in that, The step of inputting the voltage response curves and current response curves corresponding to each of the stated states of charge into the Randles equivalent circuit model to identify the electrochemical parameters of the Randles equivalent circuit model at different states of charge includes: Based on the voltage response curve and the current response curve corresponding to each of the charging state points, the voltage and current data corresponding to each of the charging state points are obtained. An optimization problem is constructed with the model parameters of the Randles equivalent circuit model as optimization variables and the root mean square error between the model-predicted voltage sequence and the measured voltage sequence as the objective function; the Randles equivalent circuit model is a first-order equivalent circuit model that includes a series ohmic resistor and an RC loop composed of a charge transfer resistor and a double-layer capacitor connected in parallel. Based on the voltage and current data corresponding to each of the stated charge state points, an optimization algorithm is used to iteratively solve the optimization problem. By minimizing the root mean square error, the optimal estimated values ​​of the model parameters are determined. The optimal estimated values ​​of the model parameters represent the identified electrochemical parameters.

4. The method for evaluating the power overload capacity of a vanadium redox flow battery according to claim 3, characterized in that, The optimization problem, which constructs the model parameters of the Randles equivalent circuit model as optimization variables and the root mean square error between the model-predicted voltage sequence and the measured voltage sequence as the objective function, includes: Determine the model parameter vector to be optimized, wherein the model parameter vector to be optimized includes at least ohmic resistance, charge transfer resistance and double-layer capacitance; An objective function is established; the objective function is configured to calculate the root mean square error between the model-predicted voltage sequence and the measured voltage sequence given the model parameter vector; the model-predicted voltage sequence is obtained by solving the differential equation corresponding to the Randles equivalent circuit model based on the model parameter vector and the measured current sequence.

5. The method for evaluating the power overload capacity of a vanadium redox flow battery according to claim 3, characterized in that, The optimization problem is iteratively solved using an optimization algorithm based on the voltage and current data corresponding to each of the aforementioned state-of-charge points. The optimal estimated values ​​of the model parameters are determined by minimizing the root mean square error, including: Generate an initial set of candidate solutions for the optimization algorithm; In each iteration, for each candidate solution in the current candidate solution set, the following steps are performed: using the model parameter values ​​and measured current data represented by the candidate solution, a circuit model simulation is performed to obtain the model predicted voltage corresponding to the candidate solution; the error between the model predicted voltage and the measured voltage corresponding to the candidate solution is calculated as the fitness value of the candidate solution; the current candidate solution set is updated according to the fitness values ​​of each candidate solution to generate candidate solutions for the next iteration; the measured current data and the measured voltage are determined based on the voltage and current data corresponding to each state of charge point; If the iteration termination condition is met, the model parameter value corresponding to the candidate solution with the highest fitness value is determined as the optimal estimate of the model parameters.

6. The method for evaluating the power overload capacity of a vanadium redox flow battery according to any one of claims 1-5, characterized in that, The step of performing polynomial fitting on each of the electrochemical parameters to establish a continuous functional relationship between each electrochemical parameter and the state of charge includes: For any of the electrochemical parameters, a fitting is performed starting from a first-order polynomial, and the coefficient of determination of the current polynomial is calculated. Under the condition that the preset conditions are met, the degree of the polynomial is increased and the fitting is performed again; the preset conditions are that the determination coefficient of the current polynomial is less than the preset precision threshold and the degree of the current polynomial has not reached the preset maximum degree. If the preset conditions are not met, the fitting is stopped and the polynomial with the largest coefficient of determination is selected as the continuous functional relationship expression between the electrochemical parameters and the state of charge.

7. The method for evaluating the power overload capacity of a vanadium redox flow battery according to claim 6, characterized in that, The preset accuracy threshold is 0.9, and the preset maximum number of attempts is three.

8. The method for evaluating the power overload capacity of a vanadium redox flow battery according to any one of claims 1-5, characterized in that, The determination of the maximum overload power that the vanadium redox flow battery can support across the full state of charge range, based on the continuous functional relationship between each electrochemical parameter and the state of charge, and the steady-state voltage equation of the battery equivalent circuit, includes: Based on the continuous functional relationship between each electrochemical parameter and the state of charge, combined with the steady-state voltage equation and the preset minimum safe voltage limit of the battery, the maximum overload power that the vanadium redox flow battery can support within the full state of charge range is calculated and output.

9. The method for evaluating the power overload capacity of a vanadium redox flow battery according to claim 8, characterized in that, The minimum safe voltage limit for the battery is determined based on the electrochemical characteristics and long-term operating life requirements of the vanadium redox flow battery cells.

10. A power overload capacity assessment device for a vanadium redox flow battery, characterized in that, include: The data acquisition module is used to perform a power step experiment on the vanadium redox flow battery at multiple pre-selected state of charge points within the full state of charge range through the grid-connected power conversion system, and simultaneously acquire the voltage response curve and the current response curve corresponding to each state of charge point during the discharge process of the vanadium redox flow battery. The parameter identification module is used to input the voltage response curves and current response curves corresponding to each of the stated states of charge into the Randles equivalent circuit model, and identify the electrochemical parameters of the Randles equivalent circuit model at different states of charge. The polynomial fitting module is used to perform polynomial fitting on each of the electrochemical parameters and establish a continuous functional relationship expression between each electrochemical parameter and the state of charge. The maximum overload power calculation module is used to determine the maximum overload power that the vanadium redox flow battery can support within the full state of charge range, based on the continuous functional relationship expression between each electrochemical parameter and the state of charge, and the steady-state voltage equation of the battery equivalent circuit.

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