Novel unity power factor circuits using zero-vector control for single-phase input system

Abstract

This paper proposes two novel circuits which realize a unity input power factor single-phase to three-phase power converter with a motor load. The power supply is connected to the neutral point of the motor, and the three-phase inverter is controlled to act also as a virtual AC/DC converter leg. This virtual leg is controlled by zero-vectors of the three-phase inverter. The main features of these circuits are: (i) no inductive components are required; and (ii) a reduction in number of switching devices compared with conventional topologies. A full-bridge power converter can be built using the same number of switching devices as the conventional half-bridge, and with no need for a capacitive leg with accessible neutral point. In this paper, the full-bridge type of the proposed circuit is experimentally tested using a 750 W induction motor as load.