Research on Phase-Locked Control Strategy for Three-Phase Combined Inverters

Abstract

A novel control strategy for three-phase combined inverters is proposed based on phase-locked loop (PLL) technology. Phase synchronous signal is easily disturbed in the process of signal transmission for conventional combined inverters with control-wire connection, which is solved by demodulation of a certain output voltage. The proposed concept is simple, and easy to implement. And good symmetrical three-phase output voltage could be achieved under unbalanced loads, even with inverters of different topologies and controllers combined together. It demonstrates almost the same high performance as that in stand-alone operation mode. Experimental results of 3.6-kVA three-phase combined inverter prototypes are presented to verify the validity and feasibility of this scheme.