Dwell-Time-Domain Asymmetric Space Vector Modulation With Multirate Feedforward Current Control for PMSM at Low Carrier-to-Target Frequency Ratio

Abstract

A novel dwell-time-domain asymmetric space vector modulation (A-SVM) with multirate feedforward current control (MFCC) is proposed for permanent magnet synchronous motor (PMSM) drives to improve steady-state harmonic current tracking accuracy under low carrier-to-target frequency ratios (CTFRs). Harmonic current injection is an effective method for active vibration suppression in PMSMs; however, its injection accuracy degrades in high power density machines because higher harmonic frequencies reduce CTFR. To address this issue, the proposed method comprises two main stages. In the MFCC stage, the harmonic current reference is updated at intervals of half the carrier period to capture intracarrier harmonic variations, thereby generating two feedforward control inputs per carrier period. In the A-SVM stage, two reference dwell-time vectors with different magnitudes and phase angles are synthesized separately for the first and second halves of each carrier period. This increases the degrees of freedom in voltage reference vector synthesis and enables explicit control of the current within the carrier period. Furthermore, to improve voltage reference vector synthesis precision, two or more active vectors can be applied in a single carrier period. Experimental results demonstrate that the proposed method improves harmonic injection accuracy by more than 30% compared with conventional methods under low CTFRs, without increasing the current and rotor position sampling frequencies, carrier frequency.