Novel MTPA Approach for IPMSM with Non-Sinusoidal Back-EMF

Interior permanent magnet synchronous machines (IPMSMs) are widely used due to features like high efficiency and high power density. For high performance drives, maximum torque per Ampère (MTPA) is employed to optimally balance the contribution of mutual and reluctance torque. However, conventionally the MTPA algorithm considers IPMSM with sinusoidal back-electromotive forces (back-EMFs). In practice, IPMSM often presents back-EMF waveforms that deviate from ideal sinusoid, exhibiting harmonic components. Thus, this paper presents a new algorithm for MTPA operation of IPMSM with non-sinusoidal back-EMF that includes the contribution of harmonic back-EMF components in average torque production. For the test machine the proposed optimal stator current provides approximately 2% higher average torque per Ampère ratio compared to the conventional MTPA. Due to the increase of torque undulations, this method is more suitable for applications non sensitive to torque ripple.