Steady-state invariant frequency and amplitude droop control using adaptive output impedance for parallel-connected UPS inverters

In this paper, a novel wireless load-sharing controller for parallel connected UPS inverters is proposed. As opposed to the conventional droop method, the proposed method achieves stable steady-state frequency and amplitude. The paper explorers the output impedance of the UPS inverters, and adaptive virtual output impedance is proposed in order to reduce its line impedance impact. Experimental results are presented from two 6 kVA UPS inverters controlled by TMS320LF2407A DSP boards, showing the feasibility of the proposed approach