Three-stage Optimal Control Approach of DC Microgrid Considering EVs Interval Prediction and BESS Rolling Power Limits

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