Space Vector PWM Techniques for Sinusoidal Output Voltage Generation with a Five-Phase Voltage Source Inverter

Abstract

Five-phase variable-speed drives currently are considered for numerous applications, including electric and hybrid-electric vehicles, traction, and ship propulsion. If the machine is designed with a concentrated stator winding, the third stator current harmonic injection can be used to enhance the torque production and the machine needs to be supplied with the fundamental and the third harmonic of the voltage. On the other hand, if the machine is with a sinusoidally distributed winding, the supply should consist of the fundamental harmonic only. Since five-phase drives are invariably supplied from five-phase voltage source inverters (VSIs), adequate methods for VSI pulse width modulation (PWM) are required. This article analyzes different space vector PWM (SVPWM) schemes for a five-phase VSI, which can be used for five-phase motor drives with sinusoidal distribution of windings. A detailed model of a five-phase VSI is presented first in terms of space vectors and the existing technique of utilizing only large space vectors is elaborated. It is shown that this SVPWM method leads to generation of high amounts of low-order output voltage harmonics. Next, a novel SVPWM method is introduced, which enables operation with pure sinusoidal output voltages up to a certain reference voltage value, which is smaller than the maximum achievable with the given DC link voltage. To enable full utilization of the DC bus voltage, two different SVPWM schemes are further developed that can be used to extend the operation so that full utilization of the DC bus is achieved. This unavoidably leads to the generation of some low-order harmonics. These harmonics are however of significantly lower values than when only large vectors are used. A detailed performance evaluation of the existing and newly developed schemes is performed, based on the low-order harmonic content in the output voltages. Simulation results are included throughout the article to illustrate and verify the theoretical considerations.