Study On Control Strategy Of Battery Energy Storage System In Micro Grid

As an important part of the micro grid,energy storage system can not only guarantee the normal operation of micro grid and power quality of load,but also can improve the power output characteristics of photovoltaic and wind power and other un-schedulable micro power.Change the un-schedulable energy into available scheduling energy.When micro grid is in the grid operation mode,the energy storage system can suppress power fluctuations by controlling its own output power;when micro grid is in off-grid operation mode,the energy storage system should provide voltage and frequency support for the micro grid system.The control strategy of energy storage system for the smooth switching of the micro grid operation mode is still insufficient,and the problem of oscillation caused by the switching operation mode can not be solved well.This article will launch a detailed study to address the problem.First,the micro grid system is established which contains wind power,solar power and energy storage.Select the appropriate battery and configure the battery capacity.According to the charge and discharge characteristics of lithium iron phosphate and research needs,select the appropriate storage converter topology.At the same time,the grid and off grid control strategy of the energy storage converter are simulated and analyzed by using the built energy storage system model.The effectiveness of the constant voltage charge discharge control,PQ control and V/f control strategy is verified.Secondly,for the presence of a larger oscillation problem in operation mode switching process of micro grid can not be completely solved,this paper presents a kind of improved V/f control.The pre synchronization control based on the voltage vector d axis orientation is directly superimposed on the V/f control,forming the V/f control having pre-synchronization function.The control strategy will stabilize voltage and frequency of micro grid,while tracks the voltage amplitude,phase and frequency of the normal operation of distribution network.Simulation results show that the control strategy can make the micro grid incorporate into the distribution network quickly,significantly reduces the frequency fluctuations and voltage fluctuations of micro grid in the operation mode switching process.Finally,take the optical storage micro grid as the research background,the paper introduces three cases depending on the direction and size of transmission power between micro grid and distribution network.And overall control strategy of battery energy storage system had been simulated and analyzed to verify the effectiveness of the proposed control strategy.