Elimination of circulating current in parallel operation of single phase inverter using droop controller

Abstract

This paper presents the control strategy for parallel operation of an inverter to eliminate DC & AC circulating current. This paper also analyses the cross-current between parallel connected inverter due to the difference in output voltage magnitudes of inverters, the phase difference of inverter output voltages and difference in DC offsets present in inverter output voltages. The circulating current flows between inverters due to DC-offset voltage and fluctuation of AC output voltages. This strategy uses the fundamental voltage and phase droop scheme to allow the inverters to share their load currents and uses a DC-offset droop scheme in order to eliminate DC circulating current. AC component of current is divided into two parts i.e. an active component of the current Ip and a reactive component of the current Iq. These two components of AC currents are used to eliminate AC circulating current. The validity of the proposed control strategy is investigated through MATLAB simulation and the results obtained satisfactorily.

Keywords

• Distributed generation
• Parallel operation
• MATLAB Simulink
• Uninterruptible power supply