Feedback Linearization-Based Direct Torque Control for Asymmetrical Six-Phase PMSM Motor With Back EMF Harmonics Compensation

This article presents a feedback linearization (FL)-based direct torque control (DTC) for an asymmetrical six-phase permanent magnet synchronous motor (PMSM). The decoupled linear model of PMSM is yielded using the FL approach. In this way, the advantages of classical hysteresis comparator-based DTC, such as fast dynamic response, are preserved. The output of the FL, namely, the desired vector, is synthesized by four active vectors for the sake of harmonics mitigation in the secondary subspace. The existing work usually adopts the synthetic vectors with zero voltage in the secondary subspace to suppress the harmonic currents, while this practice ignores the back electromotive force (EMF) harmonics. Thus, the four-vector-based space vector pulsewidth modulation (SVPWM) with and without considering the back EMF harmonics is investigated. The effectiveness of the proposed method is validated through experimental results. Compared with the classical switching table (ST)-based DTC, the proposed FL-DTC method achieves less torque and flux ripple in the primary subspace and less harmonic currents in the secondary subspace.