Influence of PWM techniques on the DC-Link capacitor power losses of multiphase VSIs

Multiphase drives are becoming a viable alternative to three-phase drives in electric traction applications, thanks to a number of benefits that offset the additional cost, e.g. smoother torque performance, higher current capability, enhanced fault tolerance, higher efficiency, and lower DC-Link current ripples. This work focuses on the impact that continuous and discontinuous PWM techniques have on such a costly and bulky component as the DC-Link capacitor, in a multiphase arrangement. Because the equivalent series resistance (ESR) of the DC-Link capacitor varies with frequency, the typical current RMS-based power loss approximation is often inaccurate. Thus, the current spectrum-based power loss estimation has been carried out for the five-phase two-level voltage source inverter (VSI). In this scenario, and switching at about 100 kHz, a MKP capacitor has shown to suffer lower power losses when discontinuous PWM techniques are used.