Sensorless Vector Control Using Simplified DC-Link Current Sampling

Abstract

This paper proposes a sensorless vector control using a simplified the DC-link current sampling. The motor current phase and amplitude are estimated from two different phases of the three-phase AC current in the conventional method. The timer function of a microcomputer for A/D conversion is necessary to sample two different phases current from the DC-link. The range of available microcomputers is restricted, which increases the cost of the motor drive system. The current estimation method without the timer function is proposed for a low-cost microcomputer in this paper. One phase of the three phase AC current is repeatedly sampled at regular intervals. The motor current phase and amplitude are estimated from two same phase current sampled at different timing. Because the accuracy of the proposed current estimation method depends on the sampling timing, a fluctuating error occurs in the case of a low sampling rate and a low carrier frequency. The fluctuating error is removed by using the compensation coefficient that is calculated online based on the sampling timing. The obtained simulation and experimental results confirm the effectiveness of the proposed method.