Virtual complex impedance-based droop control for a parallel three phase inverters-based islanded microgrids

This paper aims to improve the control performance of VSI-based distributed generation (DG) units in an islanded microgrid (IMG) under line impedance mismatches, focusing on power sharing, power decoupling, power oscillation reduction, and circulating current eliminations, all while utilizing a decentralized method. The traditional droop control method (TDCM), with well-established inner voltage and current controllers, can work effectively under ideal IMG. However, the existence of mismatches in line impedances tends to worsen its performance. In this context, a virtual complex impedance-based droop control method is proposed in this paper for three VSI-based DG units in an IMG. To examine and validate the performance of the proposed virtual complex impedance (VCI)based droop control method (DCM) used for controlling the three VSI-based DG units of the IMG, simulations using MATLAB/Simulink are performed. The results demonstrate that the proposed method can significantly enhance the control performance of the IMG. The system shares the active and reactive powers equally, with few oscillations. It also gets rid of the three DG units’ reactive power errors and mitigates the circulating currents.