Direct torque IPM motor control method to obtain unity power factor using a single-phase diode rectifier

This paper proposes a new inverter drive system for an interior permanent magnet (IPM) synchronous motor and an inverter control strategy to obtain unity power factor operation of the single-phase diode rectifier. The motor drive system for home appliances requires improving the input power factor without using a reactor, an electrolytic capacitor and a switching device. This paper can achieve to improve input power factor without using a reactor, a current control-switching converter and an electrolytic capacitor. The proposed system consists of only single-phase diode rectifier, small film capacitor (10 μF/kW) across the DC-bus, three-phase inverter and IPM motor. Source side energy provides directly to the motor without smoothing the DC-bus voltage. There are many ripple voltages across the DC-bus. A principle of unity-power-factor operation is that the inverter makes the waveform of input current sinusoidal. The unity power factor operation is achieved by dither effect. For IPM motor, inverter control scheme in this paper is based on direct torque control (DTC). The proposed system is constructed by the input current controller based on DTC. The additional current controller improves its input current waveform. This paper describes that the proposed method achieves the power factor 98.8% by experimental tests, and realizes the small size, low cost and long life inverter system.