Modeling Of Vanadium Redox Flow Battery Applied In DC Microgrid

With the widespread demonstration of All-Vanadium Redox Flow Battery(VRB)in large-scale energy storage technology,it is necessary to design an operation control scheme to make it run stably in the energy storage system.Therefore,it is one of the necessary conditions to build a VRB model to meet the system simulation requirements.In the current widely used VRB numerical analysis model,if the static equivalent circuit model is adopted separately,it is difficult to adjust the parameters dynamically when the VRB charging and discharging,which leads to the accumulation of errors.If the dynamic analysis model is adopted separately,it is difficult to expand the interface of the external circuit.Moreover,when VRB is used in system modeling,for example,applied to DC microgrid as an energy storage element,because of the mismatch of simulation scale among the components,it is difficult to carry out dynamic full process simulation analysis in large-scale time.To address the above problems,this paper proposed a dynamic equivalent circuit simulation model of VRB in SIMULINK.The model was built based on the VRB equivalent circuit model and the dynamic model analysis.The equivalent circuit model includes the electromotive force,overpotential and ohmic polarization of the reactor.The dynamic model analysis of the effects of ion diffusion,electrolyte flow loss,and temperature change.By substituting experimental parameters into the simulation model,the experimental and simulation curves of constant current/power charge-discharge are compared.Quantitative analysis shows that the error of the model is less than 1%.Meanwhile,the charge efficiency and energy efficiency of VRB are analyzed based on simulation data.A performance analysis method of VRB based on the simulation model is proposed.Then,based on the above dynamic equivalent circuit model,using the Energy Macro-Representation(EMR)method,the DC microgrid model is extended,which uses VRB as energy storage component and photovoltaic power as distributed energy.According to the energy interaction between the components,the dynamic simulation analysis model of the whole DC microgrid system is built.The Maximum Control System(MCS)is obtained by inverting the EMR model.On this basis,combined with the input and output characteristics of each part of the components and the actual working range,the coordinated operation control scheme of the system is designed when the working condition changes continuously.In SIMULINK,the EMR model and its operation scheme are simulated in large scale time to verify the reliability of the operation scheme.Finally,the bi-directional DC-DC circuit is designed,the device selection and PCB design are completed,the experimental platform is built,and the buck and boost functions of the circuit are tested.Through the test and analysis of hardware circuit parameters,the boost function of EMR model is verified.