Comparison of a synchronous reference frame virtual impedance-based autonomous current sharing control with conventional droop control for parallel-connected inverters

In order to provide faster response and better accuracy in contrast to the conventional droop control which has been widely used in the last decade as the decentralized control of parallel converters, a simple and effective autonomous current-sharing controller for parallel three-phase inverters is used. Active or reactive power calculations are unnecessary for this approach. Instead, a synchronous-reference-frame (SRF) virtual impedance loop and an SRF-based phase-locked loop are used. By means of the system transfer functions, stationary analysis is provided in order to identify the inherent mechanism of the direct and quadrature output currents in relation to the voltage amplitude and frequency. Comparison experiments from two parallel inverters are presented to compare the control performance of the conventional droop control to the proposed control, meanwhile to verify the effectiveness of the proposed control strategy in different scenarios.