Design and stability analysis for an autonomous DC microgrid with constant power load

Abstract

Fuel cell is a promising source in autonomous dc microgrid. Hybridization of fuel cell with battery is commonly implemented to overcome slow dynamic of fuel cell. Then battery compensates high frequency fluctuation and fuel cell provides consistent power at steady state. To achieve this objective, most control strategies require a centralized controller, which encounter reliability and scalability issues. This paper proposes a virtual capacitor droop controller to achieve autonomous dynamic power sharing at distributed level. An autonomous dc microgrid is designed to verify the proposed method. Considering the high penetration of constant power loads (CPLs) in dc microgrid and the destabilizing effect of CPLs, system stability is investigated with the implementation of the proposed controller. Both simulation and hardware experiment are conducted to validate the effectiveness of the proposed control method and analytical results.