Reducing Harmonics Distortion in Five-Phase VSI Using Space-Vector-Based Optimal Hybrid PWM

Compared with three-phase motors, multiphase motors offer several advantages such as higher efficiency, lower torque pulsation, and higher fault tolerance. To exploit these advantages, a multiphase modulator with low current harmonics is essential. However, the switching sequence of conventional space-vector pulse width modulation (SVPWM) is not optimal because of high stator flux ripple, which is proportional to line current harmonics. In this study, all possible switching sequences for a given switching number and carrier frequency were explored. On the basis of stator harmonic current analysis, the optimal switching sequence was selected for different modulation indices and reference angles. Then the optimal spacial distribution of each sequence to minimize root-mean-square harmonic current was derived, yielding optimal hybrid pulse width modulation (OHPWM). Similar to SVPWM, the proposed OHPWM produces an equivalent phase voltage to a reference in average means. By employing different switching sequences, the proposed method can reduce the total current harmonics distortion. Both simulations and experiments confirmed the correctness of the theoretical derivation of the proposed modulator.