A Carrier Based Minimum Voltage Distortion Overmodulation Strategy for Nine Phase Induction Motor Drives

Multiphase induction motor drives, particularly those with nine phases, offer significant advantages in fault tolerance, power density, and per phase current reduction. Extending the speed range beyond the rated DC link voltage requires overmodulation (OVM) techniques that inject harmonic voltages into non torque producing 𝑥–𝑦 subspaces. This paper presents a comprehensive evaluation of a carrier based Minimum Voltage Distortion (MVD) strategy for a symmetrical nine phase induction motor drive. The MVD method analytically minimizes the total harmonic voltage distortion (𝑇𝐻𝐷 𝑉) by injecting an optimal zero sequence voltage while preserving implementation simplicity. A detailed simulation study in MATLAB/Simulink compares MVD with clipped sinusoidal PWM, generalized SVPWM (NTV), and the Minimum Current Distortion (MCD) method. At a modulation index 𝑀=۱.۱۵, MVD reduces 𝑇𝐻𝐷 𝑉  from ۴۲.۳ % to ۱۸.۷ % and 𝑇𝐻𝐷 𝐼  from ۳۱.۵ % to ۱۳.۵ %. The dominant harmonic shifts from the ۳rd (۳۸ %) to the ۷th order (۱۳ %), lowering harmonic stator copper loss (HSCL) by approximately ۳۰ % and improving the efficiency from ۹۰.۹ % to ۹۲.۰ %. The inverter dead time effect is explicitly modeled, and the dynamic response to a speed step is characterized. A comprehensive sensitivity analysis reveals that MVD is completely immune to leakage inductance estimation errors, whereas MCD performance degrades beyond a ±۲۵ % error. A Monte Carlo analysis quantifies the statistical advantage of MVD under realistic manufacturing tolerances. A radar chart and a break even analysis provide clear design guidelines. All harmonic analyses are performed in accordance with IEEE Std ۵۱۹ ۲۰۲۲.

کلیدواژه ها:

nine phase induction motor ، overmodulation ، minimum voltage distortion ، dead time ، sensitivity analysis ، Monte Carlo ، IEEE ۵۱۹