A Voltage Injection-Based Current Harmonics Suppression Strategy for Six-Phase PMSM With Nonsinusoidal Back EMF

Abstract

This paper presents a voltage injection-based current harmonic minimization method for Wide Band Gap (WBG) device-based six-phase Permanent Magnet Synchronous Machine (PMSM) drives. The presence of low-order harmonics is common in the back EMF of PMSMs with low slot and high pole numbers. The back EMF harmonics generate low-order harmonic currents that increase torque ripples. Furthermore, zero-sequence current (ZSC) is also observed if all six phases are connected to a common neutral point. ZSC does not affect the torque ripple but reduces the system efficiency. A special technique is required to reduce ZSC for variable speed drives as direct AC component to Synchronous Reference Frame (SRF) DC transformation is not possible for ZSC. In this paper, a voltage injection-based current harmonics reduction method is proposed. The injected harmonic voltage coefficients are calculated from the harmonic estimations of back EMF and updated using closed-loop harmonic compensators to improve steady-state performance. For ZSC reduction, third harmonics power controller, and for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$6n\pm 1$</tex-math></inline-formula> (n=1,2,...) order harmonic current reduction, SRF current controllers are presented in this paper. The current harmonics minimization method is experimentally verified using a GaN-based Three Level (3L) Active Neutral Point Clamped (ANPC) inverter-driven six-phase PMSM.