Parallel operation of digital controlled modified sine wave inverters

This paper proposes a method to parallel N digital controlled low cost modified sine wave inverters with current sharing capabilities. Existing current sharing methods used to parallel pure sine wave inverters and DC-DC converters cannot be applied directly to modified sine wave inverters because of possible circulating currents. The proposed method utilizes switch signal synchronization with dead time control to eliminate circulating current, implements digital compensator with on/off control to improve the dynamic response of the first stage DC-DC converter, and adopts a “piecewise” master-slave current sharing strategies to achieve equal current distribution. A prototype is designed, built, and tested.