Adaptive droop controller for energy management of islanded ac microgrids

Abstract

Distribution feeders with high penetration of renewable power generation can be converted into microgrids for providing more quality power with increased reliability. Virtual synchronous inertia is used to increase the inertia of inverter-based microgrids to provide the same performance as synchronous generators. Frequency stability and power sharing among the distributed energy resources of islanded microgrids would be challenging due to poor transient response with droop controllers and inaccurate selection of droop values. This article proposes an adaptive droop controller for a microgrid in islanded operation that has several distributed energy resources including solar PV, diesel generator, and energy storage. Droop values, and reference values in the droop characteristics curve are decided based on the severity of the frequency disturbance and the state of charge level of the energy storage. The performance of the proposed droop controller is verified using a radial-connected microgrid derived based on a real distribution system. The results illustrate that during a disturbance, the proposed adaptive droop controller can slightly boost the diesel generator's output power with a minimum loss of charge of the energy storage.