A three-phase unity power factor front-end rectifier for AC motor drive

This study presents the bidirectional controlled switch-based high-frequency (HF) current injection circuit with simple gate control scheme. Improved power factor and total harmonic distortion (THD) of ac input line current of front-end rectifier for ac motor drive is achieved using this scheme. The gating pulses for feedback bidirectional controlled switches are generated at every zero-crossing instances of the respective phase voltages for the duration of pi/6 rad. The analysis of the converter along with loss calculations is presented. In order to validate the concept, a prototype model of a converter for 5 kW power using voltage source converter feeding three-phase induction motor is designed in the laboratory. The sinusoidal pulse width modulation switching signals are generated by using DSP (TMS320F2812). The computer simulation results and experimental results are also presented. It is observed that HF current injection for the duration of one-third of phase voltage period results in a remarkable improvement in input current THD and power factor of the front-end rectifier.