A Unified Control Strategy for Electronically Interfaced Distributed Energy Resources

This paper proposes a unified control strategy that enables islanded and grid-connected operations of three-phase electronically interfaced distributed energy resources (DERs), with no need for knowing the prevailing mode of operation or switching between two corresponding control architectures. The proposed strategy benefits from both active feedback compensation and the droop method. It allows the employment of the same power circuit and control architecture for the islanded operation as those established and optimized for grid-connected power-electronic converter systems. The proposed strategy can be directly adopted for dispatchable systems (e.g., battery energy storage systems) or, alternatively, it can be embedded in a nested control loop for non-dispatchable systems. This paper presents the mathematical model on which the proposed strategy is based. Further, the effectiveness of the proposed strategy is demonstrated through time-domain simulation of a two-unit test microgrid in the PSCAD/EMTDC software environment.