State Of Charge Estimation And Application Of Vanadium Redox Flow Battery Based On Doublekalman Filter Algorithm

Due to its safety and reliability,VRB has attracted much attention in the field of energy storage.SOC is a parameter for evaluating battery performance and characterizing the residual capacity.Its accurate measurement is of great significance for battery energy management and control.In this dissertation,DKF algorithm is used to estimate battery SOC.Firstly,taking 5kW/30 kWh VRB as the object,the basic characteristics of battery current and voltage,watt-hour energy,SOC,monomer voltage consistency and internal resistance were tested and analyzed through charge and discharge experiments.Meanwhile,the OCV-SOC curve is obtained by potentiometric titration method,and is linearly fitted by third-order approximation and least square method.Then,based on the principle of VRB,the equivalent loss circuit model with branch current is established.The parameters of the model are identified by combining experimental data with RLS.The accuracy of the model is verified by comparing the output of the model with that of the experiment under the same input.Next,based on the battery model,the Time integral,EKF and DKF estimators are designed respectively.The DKF algorithm is based on the EKF algorithm and the ampere-time integration method,using KF weight the two estimation results to obtain the final estimation result.The accuracy and robustness of the DKF algorithm are verified by comparing the estimated results of the three estimators with the reference SOC through experiments of constant current and constant voltage charging,constant power discharge and initial error.Finally,a VRB charging and discharging control platform is designed and built to verify the algorithm online.The platform consists of VRB,BMS,energy meter,charger,frequency converter and PLC controller.The operating mode is given by the software platform,and the collected battery data is transmitted to the MATLAB GUI by the hardware platform to perform online estimation of the SOC.By analyzing the experimental results,the effectiveness and feasibility of the DKF algorithm are verified.