Control of Parallel Inverters for High Power Quality and Sharing Accuracy in Single-Phase AC Microgrids

This paper studies the control problem of using conventional droop method to achieve a highly power sharing accuracy/quality in a stand-alone microgrid that operates parallel inverters. A new power sharing control scheme combined with a common integral action is then proposed in this paper to face this problem. It contains three features: (1) inclusion of load voltage and frequency regulation into the conventional scheme, (2) new concern for power loading in the droop control calculation using virtual load voltage, and (3) extension of droop coefficient concept to be implemented in different kinds of line impedance type. A case study with two parallel-connected inverter and resistive line impedance is presented and analysed by using simulation in MATLAB environment. The simulation results present the superiority of the proposed control scheme over the conventional one in proportional power sharing case. The sharing accuracy using the proposed control was almost 100 % and the quality of voltage/frequency deviation and harmonics have fulfilled the IEEE recommendation. The proposed control strategy may work in various impedance type and microgrid operation mode.