CN-121978529-A - Method and equipment for predicting external characteristics of flow battery

CN121978529ACN 121978529 ACN121978529 ACN 121978529ACN-121978529-A

Abstract

The application discloses a method and equipment for predicting external characteristics of a flow battery, the method comprises the steps of constructing an equivalent circuit model and a thermal model of the all-vanadium flow battery, calculating equivalent circuit parameters of the equivalent circuit model according to initial electrolyte temperature and initial vanadium ion concentrations in various valence states, calculating battery output voltage and electric power at the current moment according to the equivalent circuit parameters and charge-discharge current, inputting the environment temperature, the electric power at the current moment and pump power of a circulating pump into the thermal model, solving the temperature of a galvanic pile electrolyte at the next moment, inputting the temperature of the galvanic pile electrolyte at the next moment into a dynamic differential equation of the vanadium ion concentration to obtain the vanadium ion concentration at the next moment, feeding back the electrolyte temperature and the vanadium ion concentration at the next moment into the equivalent circuit model, and carrying out loop iteration until the battery charge-discharge process reaches a steady state, so as to obtain the output voltage and the galvanic pile electrolyte temperature of the flow battery at each moment in the charge-discharge process. The method reduces the computing resources and improves the prediction accuracy.

Inventors

LI AIKUI
SUN GUANGYU
SUN JUNJIE
WANG LIANG
GE YANGYANG
JIA QI
MA XINTONG
HUA XIA
LI ZHENGWEN
HAN ZIJIAO
NA GUANGYU
XIE BING
HUANG GUOCHENG
LI JIAJUE
ZHANG XIAOTONG
HU SHUBO

Assignees

大连理工大学
国网辽宁省电力有限公司电力科学研究院
国网辽宁省电力有限公司

Dates

Publication Date: 20260505
Application Date: 20251208

Claims (10)

1. A method for predicting external characteristics of a flow battery, the method comprising: The method comprises the steps of constructing an equivalent circuit model and a thermal model of the all-vanadium redox flow battery, wherein the equivalent circuit model comprises a circuit network consisting of an open-circuit voltage, an ohmic internal resistance, an activation polarization overpotential element, a concentration polarization overpotential element and a self-discharge branch, and the thermal model comprises a heat transfer differential equation for describing the temperature change of electrolyte in a galvanic pile, a pipeline and a liquid storage tank; calculating equivalent circuit parameters of an equivalent circuit model according to the initial electrolyte temperature and the initial vanadium ion concentration in each valence state, wherein the equivalent circuit parameters comprise self-discharge current, open-circuit voltage, activation polarization overpotential and concentration polarization overpotential; calculating the output voltage and the electric power of the battery at the current moment according to the equivalent circuit parameters and the charge-discharge current; Inputting the environmental temperature, electric power and pump power of a circulating pump at the current moment into the thermal model, and solving the temperature of the electrolyte of the electric pile at the next moment; Inputting the temperature of the electrolyte of the electric pile at the next moment into a dynamic differential equation of the vanadium ion concentration to obtain the vanadium ion concentration at the next moment; And feeding back the electrolyte temperature and the vanadium ion concentration at the next moment to the equivalent circuit model, and carrying out loop iteration until the battery charging and discharging process reaches a steady state, so as to obtain the output voltage of the flow battery at each moment in the charging and discharging process and the electrolyte temperature of the electric pile.
2. The method according to claim 1, wherein when the equivalent circuit parameter is an open circuit voltage, calculating the equivalent circuit parameter of the equivalent circuit model specifically comprises: Wherein U oc is open-circuit voltage, U o is standard electromotive force of a pile when in an equilibrium state, R is an ideal gas constant, F is Faraday constant, N is the number of monomers in the pile, X 2 、X 3 、X 4 X 5 is the concentration of vanadium ions in each valence state, T s is the temperature of electrolyte of the pile, k is the influence coefficient of self-discharge reaction on the open-circuit voltage, the influence coefficient and the self-discharge current represent negative correlation in the charging and discharging process.
3. The method according to claim 1, wherein when the equivalent circuit parameter is an activated polarization overpotential, calculating the equivalent circuit parameter of the equivalent circuit model specifically comprises: Wherein η a is the activation polarization overpotential, R is the ideal gas constant, F is the faraday constant, N is the number of monomers in the stack, a e is the surface area of the electrode, Is the reaction rate constant of the positive electrode, T s is the stack electrolyte temperature, which is the negative electrode reaction rate constant.
4. The method according to claim 1, wherein when the equivalent circuit parameter is concentration polarization overpotential, calculating the equivalent circuit parameter of the equivalent circuit model specifically comprises: Wherein η c is concentration polarization overpotential, l is diffusion layer thickness, R is ideal gas constant, F is faraday constant, N is monomer number in the galvanic pile, a e is surface area of electrode, I c is charge-discharge current, D f2 、D f3 、D f4 、D f5 is diffusion coefficient of vanadium ion concentration of each valence state between electrode surface area and solution, and T s is galvanic pile electrolyte temperature.
5. The method according to claim 1, wherein when the equivalent circuit parameter is a self-discharge current, calculating the equivalent circuit parameter of the equivalent circuit model specifically comprises: Wherein N is the number of monomers in the galvanic pile, F is Faraday constant, X 2 、X 3 、X 4 、X 5 is the concentration of vanadium ions in each valence state, and V is the volume of positive electrode electrolyte or negative electrode electrolyte.
6. The method according to claims 1-5, wherein calculating the battery output voltage and the electric power at the present moment according to the equivalent circuit parameters and the charge-discharge current comprises: The output voltage expression of the flow battery in the charge and discharge process is as follows: U b ＝U oc +η a +η c +I c R s Wherein U b is output voltage, U oc is open circuit voltage, eta a is active polarization overpotential, eta c is concentration polarization overpotential, I c is charge-discharge current, and R s is ohmic internal resistance; The flow battery has the following electric power expression:
7. The method of claim 1, wherein the expression of the thermal model is as follows: wherein, the state vector t= [ T S ,T p ,T t ] T ,u＝[P e ,T air ,P p ] T ; The matrix for B 1 is as follows: the matrix for B 2 is as follows: the matrix of G is as follows: Wherein C p is specific heat of the cell stack electrolyte, ρ is cell stack electrolyte density, V s is electrolyte volume in the cell stack, V t is electrolyte volume in the liquid storage tank, V s is electrolyte volume in the cell stack, T p is pipe electrolyte temperature, T s is cell stack electrolyte temperature, T t is liquid storage tank electrolyte temperature, T air is ambient temperature, S S is surface area of electrolyte-containing portion in the cell stack, S t is surface area of the liquid storage tank, S P is surface area of the pipe, H S is electrolyte heat transfer coefficient in the cell stack, H P is electrolyte heat transfer coefficient in the pipe, H t is electrolyte heat transfer coefficient in the liquid storage tank, P e is electric power, P p is pump power, and q is cell stack electrolyte flow.
8. The method of claim 1, wherein the expression of the dynamic differential equation for the vanadium ion concentration is as follows: Wherein d is the thickness of the ionic membrane, V is the volume of the positive electrode electrolyte or the negative electrode electrolyte, k 2 、k 3 、k 4 、k 5 is the diffusion coefficient of vanadium ions in each valence state influenced by the temperature of the electrolyte of the electric pile, S is the area of the ionic membrane, alpha i and beta i are the coefficient matrix and vector related to the reaction, and I c is the charge and discharge current. X i is the vanadium ion concentration of each valence.
9. The method according to claim 1, wherein the method further comprises: Comparing the temperature predicted value with a preset safety threshold value; And when the temperature predicted value exceeds a preset safety threshold, generating a control instruction to adjust the running state of the cooling system or the rotating speed of the electrolyte circulating pump.
10. A flow battery external characteristic prediction apparatus, characterized by comprising: at least one processor, and A memory communicatively coupled to the at least one processor, wherein, The memory stores instructions executable by the at least one processor to enable the at least one processor to perform a method of predicting flow cell external characteristics according to any one of claims 1-9.

Description

Method and equipment for predicting external characteristics of flow battery Technical Field The application relates to the technical field of energy storage, in particular to a method and equipment for predicting external characteristics of a flow battery. Background All-vanadium redox flow battery (vanadium redox flow battery, VFB) is regarded as an ideal choice for supporting renewable energy grid connection, improving power grid stability and pushing energy storage technology development as an advanced electrochemical energy storage battery due to the characteristics of high energy conversion efficiency, long cycle life, good safety, environmental friendliness and the like. The external characteristics of the VFB are mainly electrical characteristics and thermal characteristics during the operation of the battery, including battery voltage, power, temperature, and other indicators. In the actual operation of the all-vanadium redox flow battery, the temperature dynamic change is caused by the thermal effect in the charge and discharge process, so that the external characteristic performance of the battery is directly influenced. The research on external characteristics such as the voltage and the temperature of the all-vanadium redox flow battery has important engineering value for optimizing battery management, prolonging the service life of the battery and ensuring safe operation. At present, modeling researches on the external characteristics of the VFB are mainly divided into two types, namely an equivalent circuit model and a thermal model. The current equivalent circuit model is mostly based on constant temperature assumption, and the influence of temperature dynamic fluctuation in the charge and discharge process on model parameters in the circuit is not fully considered. The current thermal model provides guidance for the establishment of a thermal management strategy in the VFB charging and discharging process, but the thermal model mostly takes temperature as an independent variable, and does not establish a coupling relation with electrical characteristics such as voltage and the like, so that the prediction precision of external characteristic parameters is insufficient. Disclosure of Invention In order to solve the above problems, the present application provides a method for predicting external characteristics of a flow battery, comprising: The method comprises the steps of constructing an equivalent circuit model and a thermal model of the all-vanadium redox flow battery, wherein the equivalent circuit model at least comprises a circuit network consisting of open-circuit voltage, ohmic internal resistance, an activation polarization overpotential element, a concentration polarization overpotential element and a self-discharge branch, and self-discharge current is calculated based on the concentration difference of positive and negative vanadium ions; calculating equivalent circuit parameters of an equivalent circuit model according to the initial electrolyte temperature and the initial vanadium ion concentration in each valence state, wherein the equivalent circuit parameters comprise self-discharge current, open-circuit voltage, activation polarization overpotential and concentration polarization overpotential; calculating the output voltage and the electric power of the battery at the current moment according to the equivalent circuit parameters and the charge-discharge current; Inputting the environmental temperature, electric power and pump power of a circulating pump at the current moment into the thermal model, and solving the temperature of the electrolyte of the electric pile at the next moment; Inputting the temperature of the electrolyte of the electric pile at the next moment into a dynamic differential equation of the vanadium ion concentration to obtain the vanadium ion concentration at the next moment; And feeding back the electrolyte temperature and the vanadium ion concentration at the next moment to the equivalent circuit model, and carrying out loop iteration until the battery charging and discharging process reaches a steady state, so as to obtain the output voltage of the flow battery at each moment in the charging and discharging process and the electrolyte temperature of the electric pile. In one example, when the equivalent circuit parameter is an open circuit voltage, calculating the equivalent circuit parameter of the equivalent circuit model specifically includes: Wherein U oc is open-circuit voltage, U o is standard electromotive force of a pile when in an equilibrium state, R is an ideal gas constant, F is Faraday constant, N is the number of monomers in the pile, X 2、X3、X4X5 is the concentration of vanadium ions in each valence state, T s is the temperature of electrolyte of the pile, k is the influence coefficient of self-discharge reaction on the open-circuit voltage, the influence coefficient and the self-discharge current represent negative correlation in t