| The output of photovoltaic power generation,wind power generation and other new energy generation methods is intermittent and volatile,which will affect the sTab operation of the power grid.With the advantages of large scale and long life,all-vanadium liquid-flow battery(VRB)has become one of the ideal choices for distributed energy generation and microgrid energy storage devices,which can restrain the impact of distributed generation output fluctuation on the power grid.The state of charge(SOC)of VRB is one of the important bases for energy management system to formulate energy management strategy,furthermore energy management system(EMS)is the key to ensure the safe and reliable operation of VRB.Therefore,it is necessary to study the SOC estimation method and EMS of VRB.(1)Firstly,this paper investigates the research status of VRB and energy management system of microgrid,and summarizes the common SOC estimation methods of VRB,which lays a foundation for the later research on the improved SOC algorithm.(2)In order to describe the operation characteristics of VRB more accurately,a 2-RCs equivalent circuit model of VRB is established.The parameters of the model are identified online by least squares recursive algorithm with forgetting factor(FFRLS),and the effectiveness of the 2-RCs model was verified by simulation.(3)The working principle and recurrence process of classical Kalman filter,extended Kalman filter and unscented Kalman filter are compared and analyzed.Aiming at the influence of battery capacity attenuation and accumulative error of current integration method on SOC estimation,a EBKF-UKF joint algorithm is proposed to estimate the SOC of VRB.Simulink simulation verifies the reliability of the algorithm.(4)The overall framework of Megawatt-class VRB system is proposed,the hardware circuit and software program of VRB battery management system are designed as well.At last,the energy management strategy and black-start scheme of VRB system are studied. |
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