DC Link Capacitor Sizing for 240°-Clamped Space Vector PWM for EV Traction Inverters

DC link capacitor is one of the critical components in EV powertrain affecting the size, weight, and reliability. In a cascaded architecture (DC-DC stage followed by DC-AC stage), the size of DC link capacitor is dictated by the ripple current it has to support from both the stages. This work explores the benefits of relatively new PWM method called 240°-Clamped space vector PWM (240CPWM) in terms of reduced current stress on the DC link capacitor which corresponds to reduction in the DC link capacitor size. Detailed analysis of ripple current contribution from DC-DC and DC-AC stages is carried out leading to design methods for the DC link capacitor. It is shown that the current stress on the DC link capacitor for 240CPWM is 25% lower as compared to CSVPWM under same operating conditions. The analysis is validated by the experimental results from a 5 kW, 500 V (line to line voltage) hardware prototype.