Wireless current sharing scheme considering phase synchronization requirement for paralleled online UPS inverters

In this paper, a wireless current sharing Scheme for paralleled online uninterruptible power system (UPS) inverters is proposed, based on which effective power sharing under phase locking condition and fast dynamic response of sharing load are obtained. The output impedance of UPS inverter is designed to be resistive, and the droop method based on resistive output impedance is employed. Moreover, an adaptive virtual resistor is added to regulate the magnitude of the output impedance according to the requirement of reactive power sharing, which makes the power sharing less sensitive to frequency change. Besides, the root-mean-square (RMS) loop is adopted to improve the output voltage quality. And the secondary P-V droop method is put forward to decrease the amplitude deviation and improve the dynamic performance of current sharing. Simulation and experimental results are presented to demonstrate the validity of the proposed scheme.