Three-stage optimal control approach of DC microgrid considering EVs interval prediction and BESS rolling power limits

In order to prolong the battery energy storage system (BESS) service life in microgrids, this paper proposes a three-stage optimal control approach to reduce the charging/discharging frequency of BESS caused by large-scale renewable energy storages (RESs) integrated into microgrids. The principle of the proposed approach is to realize the coordination scheduling of electric vehicles (EVs) and BESS with considering EVs interval prediction and BESS rolling power limits. In the first stage, based on the prediction of photovoltaics and wind turbine outputs, the day-ahead electric price and basic loads are scheduled to minimize microgrid operation costs. Then in the second stage, the interval prediction model of EV cluster load demands is developed to deal with the mobility and uncertainty of EVs, and then the hourly rolling optimal power limits of BESS are calculated to minimize the BESS aging loss. Finally, in the third stage, the BESS control mode is adjusted by tracking the real-time microgrid current and recalculating BESS power limits when the current exceeds the withstand current of the inverter, which compensates for the second-stage scheduling decisions. Simulation results demonstrate the superior performance of the proposed three-stage optimal control approach in prolonging the service life of BESS and reducing microgrid total operation cost.