Grid Current Control Based Smooth Transfer Control Method in Distributed Generation

Abstract

This paper proposes a smooth transfer control strategy for distributed generation (DG) units between grid-connected (GC) mode and stand-alone (SA) mode. In the GC mode, the DG unit is controlled as a current source. When islanding happens, the DG unit can transfer from current source to voltage source automatically. In the SA mode, the DG unit is based on current droop control. The advantages of this proposed strategy are as follows. Firstly, compared with indirect current control, the reliability of microgrid system can be improved in the SA mode. Secondly, compared with the droop control method, the proposed control strategy can improve the grid current quality and output constant power when the grid voltage has oscillation in the GC mode, and can provide faster dynamic performance. The simulation results are provided to verify the effectiveness of the proposed method.