Direct microgrid harmonic current compensation and seamless operation mode transfer using coordinated triple-loop current-voltage-current controller

It is found that connecting local load to DG interfacing converter output filter could cause significant resonance in grid-connected operation mode, even when the well-understood double-loop current control with well design control parameters according to the design guidelines. To overcome this limitation, a closed-loop triple-loop control algorithm is proposed in order to realize an accurate grid current harmonic compensation. It is demonstrated that the proposed method offers the interfacing converter the capability to seamlessly transfer from grid-tied to islanding operation, even when the transfer happens at a time with maximum line current or grid voltage.