三相PWMインバータの直流電流検出による交流電流演算の一手法

Abstract

In order to reduce costs of inverters for home electrical appliances using the PMSM, the AC current sensor-less control is required as well as the position sensor-less control. This paper proposes a PWM technique suitable for calculating AC currents from sampled DC current data in the one-shunt system, which is one of the AC current sensor-less methods. The proposed PWM technique using a triangle carrier wave leads to the dc current sampling at near the top and bottom of the carrier wave, and AC current calculation within one cycle of the carrier under normal conditions. To reduce errors in the AC current calculation caused by the PWM current ripple, the current ripple waveforms are calculated from the instantaneous inverter output voltages and used for the compensation. The principles of the PWM technique and the AC current calculation are explained, as well as experimental results.