CN-121978536-A - Power overload capacity assessment method and device for all-vanadium redox flow battery

CN121978536ACN 121978536 ACN121978536 ACN 121978536ACN-121978536-A

Abstract

The invention provides a power overload capacity assessment method and device of an all-vanadium redox flow battery, wherein the method comprises the steps of executing 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, and synchronously collecting a voltage response curve and a current response curve corresponding to each charge state point in a battery discharging process; the method comprises the steps of inputting a voltage response curve and a current response curve corresponding to each charge state point into a Randes equivalent circuit model, identifying to obtain each electrochemical parameter, respectively performing polynomial fitting on each electrochemical parameter, establishing a continuous functional relation expression between each electrochemical parameter and the charge state, and determining the maximum overload power which can be supported by the vanadium redox flow battery in the full charge state range based on each continuous functional relation expression and a steady-state voltage equation of the battery equivalent circuit. The invention realizes accurate, continuous and predictable evaluation of the power overload capacity of the all-vanadium redox flow battery.

Inventors

CHEN LEI
WANG SHIYU
Jian Aolin
WU JINGBO
ZHAO DU
XU SHILONG
XU FEI
MIN YONG
HAO LING

Assignees

清华大学
大连融科储能集团股份有限公司

Dates

Publication Date: 20260505
Application Date: 20260226

Claims (10)

1. The power overload capacity assessment method of the all-vanadium redox flow battery is characterized by comprising the following steps of: Executing a power step experiment on the all-vanadium redox flow battery at a plurality of preselected state-of-charge points in a full state-of-charge range through a grid-connected power conversion system, and synchronously collecting a voltage response curve corresponding to each state-of-charge point and a current response curve corresponding to each state-of-charge point in a discharging process of the all-vanadium redox flow battery; Inputting a voltage response curve corresponding to each charge state point and a current response curve corresponding to each charge state point into a randes equivalent circuit model, and identifying to obtain each electrochemical parameter of the randes equivalent circuit model at different charge state points; Respectively performing polynomial fitting on each electrochemical parameter, and establishing a continuous functional relation expression between each electrochemical parameter and the state of charge; And determining the maximum overload power supportable by the all-vanadium redox flow battery in the full state-of-charge range based on the continuous functional relation expression between each electrochemical parameter and the state-of-charge and a steady-state voltage equation of a battery equivalent circuit.
2. The method for evaluating the power overload capability of an all-vanadium redox flow battery according to claim 1, wherein the performing, by the grid-connected power conversion system, the power step experiment on the all-vanadium redox flow battery at a plurality of preselected state-of-charge points over the range of the full state-of-charge comprises: And aiming at any charge state point, the grid-connected output power is increased to a preset rated value at a preset speed through the grid-connected power conversion system, so that the discharge power of the all-vanadium redox flow battery is increased in a step-type manner.
3. The method for evaluating the power overload capacity of an all-vanadium redox flow battery according to claim 1, wherein the step of inputting the voltage response curve corresponding to each state of charge point and the current response curve corresponding to each state of charge point into a randes equivalent circuit model, and identifying each electrochemical parameter of the randes equivalent circuit model at different states of charge points comprises the steps of: acquiring voltage and current data corresponding to each state of charge point based on the voltage response curve corresponding to each state of charge point and the current response curve corresponding to each state of charge point; Establishing an optimization problem by taking model parameters of the Randes equivalent circuit model as an optimization variable and taking root mean square error between a model predicted voltage sequence and an actually measured voltage sequence as an objective function, wherein the Randes equivalent circuit model is a first-order equivalent circuit model comprising a series ohmic resistor and an RC loop formed by connecting a charge transfer resistor and an electric double layer capacitor in parallel; And carrying out iterative solution on the optimization problem by adopting an optimization algorithm based on the voltage and current data corresponding to each charge state point, and determining an optimal estimated value of a model parameter by minimizing the root mean square error, wherein the optimal estimated value of the model parameter represents each identified electrochemical parameter.
4. The method for evaluating the power overload capacity of an all-vanadium redox flow battery according to claim 3, wherein the constructing an optimization problem with model parameters of the randes equivalent circuit model as an optimization variable and with root mean square error between a model predicted voltage sequence and an actually measured voltage sequence as an objective function comprises: determining a model parameter vector to be optimized, wherein the model parameter vector to be optimized at least comprises an ohmic resistor, a charge transfer resistor and an electric double layer capacitor; the method comprises the steps of establishing an objective function, wherein the objective function is configured to calculate root mean square error between a model predicted voltage sequence and an actually measured voltage sequence under the condition that a model parameter vector is given, and the model predicted voltage sequence is obtained by solving a differential equation corresponding to a Randes equivalent circuit model based on the model parameter vector and the actually measured current sequence.
5. The method for evaluating the power overload capacity of an all-vanadium redox flow battery according to claim 3, wherein the step of iteratively solving the optimization problem by using an optimization algorithm based on the voltage and current data corresponding to each state of charge point, and determining the optimal estimated value of the model parameter by minimizing the root mean square error comprises: Generating an initial candidate solution set of the optimization algorithm; In each iteration, executing the following steps of carrying out circuit model simulation by using a model parameter value and actual measurement current data represented by the candidate solution to obtain a model prediction voltage corresponding to the candidate solution, calculating an error of the model prediction voltage corresponding to the candidate solution and the actual measurement voltage as an adaptability value of the candidate solution, updating the current candidate solution set according to the adaptability value of each candidate solution to generate a candidate solution of the next iteration, wherein the actual measurement current data and the actual measurement voltage are determined based on the voltage and the current data corresponding to each charge state point; and under the condition that the iteration termination condition is met, determining a model parameter value corresponding to the candidate solution with the highest fitness value as an optimal estimated value of the model parameter.
6. The method for evaluating the power overload capacity of an all-vanadium redox flow battery according to any one of claims 1 to 5, wherein the fitting of polynomials to each of the electrochemical parameters respectively establishes a continuous functional relation expression between each of the electrochemical parameters and a state of charge, and comprises: Fitting from a first order polynomial for any electrochemical parameter, and calculating the decision coefficient of the current polynomial; Under the condition that a preset condition is met, polynomial degree is increased and fitting is carried out again, wherein the preset condition is that the decision coefficient of the current polynomial is smaller than a preset precision threshold value and the degree of the current polynomial does not reach a preset highest degree; And under the condition that the preset condition is not met, stopping fitting and selecting a polynomial with the maximum decision coefficient as a continuous functional relation expression between the electrochemical parameter and the state of charge.
7. The method for evaluating the power overload capacity of an all-vanadium redox flow battery according to claim 6, wherein the preset precision threshold is 0.9 and the preset maximum number of times is three.
8. The method for evaluating the power overload capacity of an all-vanadium redox flow battery according to any one of claims 1 to 5, wherein the determining the maximum overload power supportable by the all-vanadium redox flow battery in the all-state-of-charge range based on the continuous functional relation expression between each electrochemical parameter and the state-of-charge and the steady-state voltage equation of the battery equivalent circuit includes: And calculating and outputting the maximum overload power supportable by the all-vanadium redox flow battery in the full state-of-charge range by combining the steady-state voltage equation and a preset minimum safe voltage limit of the battery based on continuous functional relation expression between each electrochemical parameter and the state-of-charge.
9. The method of claim 8, wherein the battery minimum safe voltage limit is determined based on electrochemical characteristics and long-term operating life requirements of the all-vanadium redox flow battery cell.
10. A power overload capability assessment device of an all-vanadium redox flow battery, comprising: the data acquisition module is used for executing a power step experiment on the all-vanadium redox flow battery at a plurality of preselected state-of-charge points in a full state-of-charge range through the grid-connected power conversion system, and synchronously acquiring a voltage response curve corresponding to each state-of-charge point and a current response curve corresponding to each state-of-charge point in the discharging process of the all-vanadium redox flow battery; The parameter identification module is used for inputting the voltage response curve corresponding to each charge state point and the current response curve corresponding to each charge state point into a randes equivalent circuit model, and identifying and obtaining each electrochemical parameter of the randes equivalent circuit model at different charge state points; the polynomial fitting module is used for respectively performing polynomial fitting on each electrochemical parameter and establishing a continuous functional relation expression between each electrochemical parameter and the state of charge; And the maximum overload power calculation module is used for determining the maximum overload power which can be supported by the all-vanadium redox flow battery in the full charge state range based on the continuous functional relation expression between the electrochemical parameters and the charge state and a steady-state voltage equation of a battery equivalent circuit.

Description

Power overload capacity assessment method and device for all-vanadium redox flow battery Technical Field The invention relates to the technical field of electrochemical energy storage systems, in particular to a power overload capacity assessment method and device of an all-vanadium redox flow battery. Background As renewable energy permeability continues to rise, the demand of the grid for rapid power response and overload capabilities of the energy storage system is increasing. The all-vanadium redox flow battery is widely applied to scenes such as frequency modulation, peak shaving, network-structured active support and the like due to the advantages of decoupling of power and capacity, long service life, high safety and the like. However, the electrochemical characteristics of the all-vanadium redox flow battery determine that the electrochemical parameters such as internal resistance, open circuit voltage and the like of the battery have significant differences under different states of Charge (SOC), so that the overload power bearable by the all-vanadium redox flow battery has strong SOC dependence. Currently, most flow battery systems still employ fixed power limits or empirical safety margins in power scheduling and protection strategy design, and this approach may lead to either low or high SOC conditions: (1) The conservation operation is that the dynamic response capability of the system is limited, and the energy storage utilization rate is reduced; (2) Risk operation, namely underestimating the risk of internal resistance rise or voltage drop, and causing irreversible damage such as over-discharge, hydrogen evolution, membrane damage and the like of the battery, thereby threatening the safety of the system. Thus, an effective solution is needed to solve the above technical problems. Disclosure of Invention The invention provides a method and a device for evaluating the power overload capacity of an all-vanadium redox flow battery, which realize accurate, continuous and predictable evaluation of the power overload capacity of the all-vanadium redox flow battery and are beneficial to improving the safety and dynamic response performance of a redox flow battery system under complex working conditions. In a first aspect, the present invention provides a method for evaluating power overload capability of an all-vanadium redox flow battery, the method comprising the steps of: Executing a power step experiment on the all-vanadium redox flow battery at a plurality of preselected state-of-charge points in a full state-of-charge range through a grid-connected power conversion system, and synchronously collecting a voltage response curve corresponding to each state-of-charge point and a current response curve corresponding to each state-of-charge point in a discharging process of the all-vanadium redox flow battery; Inputting a voltage response curve corresponding to each charge state point and a current response curve corresponding to each charge state point into a randes equivalent circuit model, and identifying to obtain each electrochemical parameter of the randes equivalent circuit model at different charge state points; Respectively performing polynomial fitting on each electrochemical parameter, and establishing a continuous functional relation expression between each electrochemical parameter and the state of charge; And determining the maximum overload power supportable by the all-vanadium redox flow battery in the full state-of-charge range based on the continuous functional relation expression between each electrochemical parameter and the state-of-charge and a steady-state voltage equation of a battery equivalent circuit. According to the power overload capacity assessment method of the all-vanadium redox flow battery provided by the invention, the power step experiment is carried out on the all-vanadium redox flow battery at a plurality of preselected state of charge points in a full state of charge range through a grid-connected power conversion system, and the power step experiment comprises the following steps: And aiming at any charge state point, the grid-connected output power is increased to a preset rated value at a preset speed through the grid-connected power conversion system, so that the discharge power of the all-vanadium redox flow battery is increased in a step-type manner. According to the power overload capacity assessment method of the vanadium redox flow battery provided by the invention, the voltage response curve corresponding to each charge state point and the current response curve corresponding to each charge state point are input into a randes equivalent circuit model, and each electrochemical parameter of the randes equivalent circuit model at different charge state points is obtained through identification, and the method comprises the following steps: acquiring voltage and current data corresponding to each state of charge point based on the voltage response curve