Evaluation of current ripple amplitude in five-phase PWM voltage source inverters

Abstract

Multiphase systems are nowadays considered for various industrial applications. Numerous PWM schemes for multiphase voltage source inverters with sinusoidal outputs have been developed, but no detailed analysis of the impact of these modulation schemes on the output peak-to-peak current ripple amplitude has been reported. Determination of current ripple in five-phase PWM voltage source inverters is important for both design and control purposes. This paper gives the complete analysis of the peak-to-peak current ripple distribution over a fundamental period. In particular, peak-to-peak current ripple amplitude is analytically determined as a function of the modulation index, and a simplified expression to get its maximum value is carried out. Reference is made to centered symmetrical PWM, being the most simple and effective solution to maximize the dc bus utilization, leading to a nearly-optimal modulation to minimize the rms of current ripple. However, the analysis can be easily extended to either discontinuous or asymmetrical modulation, both carrier-based and space vector PWM. The analytical developments for all the different sub-cases are verified by numerical simulations.