Research On Control Strategy Of Battery Energy Storage System In Photovoltaic Microgrid

With the increasingly severe global environmental problems,the exploration and utilization of new energy sources is the current development trend.The microgrid integrated with various distributed power sources(DER)is an efficient and flexible new energy utilization method.It is mainly composed of distributed power generation units(DG)and energy storage systems(ESS),while photovoltaics with energy storage systems Microgrid is an effective means to utilize solar energy,so the research on photovoltaic microgrid control strategy is of great significance.This paper discusses the photovoltaic power generation unit and the microgrid system of battery energy storage,studies the mathematical model and characteristics of photovoltaic cells,and establishes a simulation model of the photovoltaic power generation unit.Aiming at the problem of tracking the maximum power point of photovoltaic cells,an adaptive variable-step perturbation observation method is proposed based on the traditional perturbation observation method(P&O),and the feasibility of this method is verified by simulation comparison.The control method of microgrid in grid-connected mode is discussed.First,the control strategy of photovoltaic power generation unit and battery energy storage system in the grid-connected state is studied.The method adopted is mainly P-Q control.The photovoltaic power generation unit is implemented based on MPPT and the battery energy storage system is implemented based on its SOC.The current inner-loop closed-loop feedback control strategy in grid-connected mode is studied to realize the constant power control of photovoltaic power generation units and energy storage systems.Finally,based on the Matlab/Simulink platform,under the conditions of variable irradiation intensity and different initial states of the energy storage system,the simulation analysis of the control operation process of the photovoltaic power generation unit and energy storage system under grid-connected conditions is carried out,and the experimental results are The validity of the model and the correctness of the control strategy are verified.The control method of microgrid in island mode is discussed too.First,the control strategy of the battery energy storage system in the islanding state is studied.The method adopted is mainly V/f control,and the logic control scheme of the battery SOC is proposed,which is used as the main control unit to support the voltage and frequency of the microgrid.Furthermore,the closed-loop feedback control strategy of voltage outer loop and current inner loop of the battery energy storage system in island mode is studied.Finally,based on the Matlab/Simulink platform,the micro-grid was simulated and analyzed under the conditions of transition from grid connection to islanding,power generation unit disassembly,load shedding,and island reconnection to the main grid.The experimental results verified the micro-grid.In island mode,this control strategy can run stably,and it can switch smoothly in the two modes.