Comparison of Peak-to-Peak Current Ripple Amplitude in Multi­phase PWM Voltage Source Inverters

Multiphase systems are nowadays considered for various industrial applications. Numerous PWM schemes for multiphase voltage source inverters with sinusoidal outputs have been developed, but just recently the impact of these modulation schemes on the output peak-to-peak current ripple amplitude has been considered. Determination of current ripple in multiphase PWM voltage source inverters is important for both design and control purposes. This paper gives the comparison of the peak-to-peak current ripple distribution over a fundamental period for multiphase VSIs, starting from three-phase and extended to the multiphase inverters, with emphasis on five and seven phases. Simplified expressions to get maximum value of the ripple are carried out and compared among inverters with different phase number. Although reference is made to the 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 the current ripple, the analysis can be readily extended to either discontinuous or asymmetrical modulations, both carrier-based and space vector PWM. The results obtained by the proposed analytical approach are backed with the numerical simulations of the peak-to-peak ripple for inverters with different phase numbers and in case of different modulation indexes to prove the effectiveness of mathematical developments.