A Novel Dual Feedback Collaborative Flux-Weakening Control for Multiphase Non-Sinusoidal Permanent Magnet Synchronous Motor

A flux weakening (FW) control of a highly non-sinusoidal seven-phase permanent magnet synchronous machine (PMSM) is addressed. In conventional FW control of multiphase PMSM with odd number of phases, the fundamental and the 3rd harmonic d-axis currents are used simultaneously with a fixed distribution ratio. Moreover, the phase difference between the fundamental and the 3rd harmonic volage are not taken into account, which is very important for the voltage peak value related to FW control performances. This paper proposes a novel dual feedback collaborative FW control for multiphase non-sinusoidal PMSM. Firstly, a parameter independent 2D lookup table (LUT) is built for the phase voltage peak value calculation, in which the amplitude ratio and the phase difference of voltage harmonic components are used as indexes. Secondly, the impact of the d-axis currents on the phase difference of the voltage harmonic components are studied. The instability mechanism of the conventional dual d-axis currents injection FW strategy with fixed ratio is revealed. Thirdly, based on the previous analysis, a novel dual feedback collaborative FW control strategy is proposed, which allows considering simultaneously the phase difference of the voltage components and the distribution ratio of d-axis currents. The needed rms value of current can be reduced, compared to the conventional FW control strategy. The effectiveness of the proposed theoretical analysis is verified through both the simulation and the experimental results of the 7-phase non-sinusoidal PMSM.