Analysis and compensation of current sampling error in AC drive with discontinuous PWM

This paper addresses the issue of current sampling in high performance AC motor drive systems fed by a discontinuous PWM inverter. The effect of the sampling error due to the measurement delay produced by the low pass filter and A/D converter is described in case of discontinuous PWM. To compensate the error, a method to estimate the delay time of the whole measurement system based on the measured current is proposed and its effectiveness is verified by experimental results. The proposed algorithm can automatically estimate the system delay introduced by low pass filter and A/D converter at the commissioning stage. Through delaying the current sampling by the estimated value, experimental results reveal more than 50% reduction of current ripples