Hybrid Energy Storages for Islanded Microgrids with High Solar PV Penetration

Distribution feeders with high penetration of renewable power generation can be converted into microgrids to provide power with increased reliability and high power quality. Voltage stability during faults in islanded microgrids with a low X/R ratio would be challenging due to the limited short circuit current contribution of the inverter-based distributed energy resources. Virtual synchronous inertia is used to increase the inertia of inverter-based microgrids to provide the same performance as synchronous generators. This article proposes a designing and controlling system for a supercapacitor-battery hybrid energy storage system for a microgrid in islanded operation. A supervisory controller is used to decide the state of the supercapacitor according to the severity of the fault, and the state of charge level of the energy storage. The performance of the proposed energy storage system is verified using a microgrid derived based on a real distribution system. The results illustrate that during a fault, the proposed hybrid energy storage system can improve the voltage ride-through capability of the microgrid compared to using only the conventional battery storage systems.