A Coordinated Control Method for DC Microgrid with PV and Energy Storage Based on Multi-Voltage-Loop Competition

Energy storage system (ESS) is usually used to smooth fluctuations of photovoltaic (PV) generation in DC microgrids. However, fluctuations in PV and loads may lead to power imbalance under extreme conditions. It is necessary to achieve system stability and assist energy management through coordinated control strategy. In this paper, a coordinated control method based on multi-voltage-loop competition is proposed for DC microgrid with PV and energy storage. According to the power balance relationship among PV, ESS and the grid-connected inverter in the microgrid, four working modes are defined to keep the system stable and prioritize grid-connected power commands from upper energy management system (EMS). Through the competition among voltage control loops of modules in the DC microgrid, the system can switch among the four modes adaptively and smoothly according to various working conditions. The processing utilizes the bus voltage as information medium without separate communication devices. The effectiveness of the method is verified by simulation.