Autonomous Coordination of Multiple PV/Battery Hybrid Units in Islanded Microgrids

In this paper, a control strategy is developed to achieve fully autonomous power management of multiple photovoltaic (PV)/battery hybrid units in islanded microgrids. Also, the developed strategy has the ability to autonomously coordinate with dispatchable droop controlled units. The power supplied by the hybrid units is autonomously determined based on the available PV power from all hybrid units, the total generation capacity of the available dispatchable units, the total load demand, and the state-of-charge (SOC) of all batteries in the microgrid. In addition to maintaining the power balance in the microgrid, the decentralized coordination scheme prioritizes charging the microgrid batteries with lower SOC. Also, the control strategy enables the hybrid units to import power from other units to support charging their batteries. These features are achieved by employing the proposed multi-segment adaptive power/frequency characteristics in the hybrid unit controllers. Since the strategy is based solely on the local voltage controllers, neither a central energy management system nor communications among different units are required. The developed strategy has been validated using detailed switching models in PSCAD/EMTDC.