Harmonic losses of multi-phase PWM inverter-fed drives

Multi-phase variable speed drives, supplied from two-level voltage source inverters (VSIs), are currently considered for a number of industrial applications. While various multi-phase PWM schemes had been developed, no detailed analysis of the impact of these schemes on harmonic losses (current ripple) has been reported. This paper presents a general analytical analysis and comparison of harmonic losses of two basic continuous PWM (CPWM) schemes aimed at sinusoidal output voltage generation with multi-phase VSIs. The analysis utilizes the concept of multiple polygon connections, which exist for multi-phase systems, and covers all multi-phase topologies with an odd phase number and single neutral connection. General harmonics distortion factors (HDFs) of sinusoidal PWM (SPWM) and harmonic injection PWM (HIPWM) are determined and compared for various phase numbers. Theoretical findings are verified experimentally using a five-phase induction motor drive.