An improved droop controller for parallel operation of single-phase inverters using R-C output impedance

This paper proposes a new droop-based approach for proportional load sharing among parallel-connected inverters in an islanded microgrid. For achieving accuracy in load sharing among the parallel connected inverters, R-C type virtual impedance is emulated as the output impedance of inverters. A new method of average power computation is proposed which significantly reduces the delay encountered in conventional approaches. In contrast with the conventional droop-control methods, the proposed approach results in effectively reduced line impedance, consequently improving the full-load voltage regulation. Simulation results are provided with two single phase inverters, of different rating, connected in parallel. It is shown that proportional sharing of active and reactive powers is obtained with excellent dynamic performance.