A Method to Minimize Current Ripple of DC Link Capacitor for 48V Inverter Integrated Starter/Generator

This paper presents a method to reduce the current ripple of the dc link capacitor for the 48V inverter integrated starter and generator. A 48V belt-driven starter-generator with the integrated inverter has a limited space for the inverter. And about 20% of the inverter material cost is from the dc link capacitor. For size and cost reduction of the capacitor, it is important to reduce the ripple current in the dc link. Firstly, this paper applied a six-phase inverter in which two paralleled three phase inverters are phase-shifted by 30 degrees. There are coupling effects between the dual three-phase windings. So the voltage equations of the dual three-phase electric machines are rearranged considering the coupling effect and simulated. Secondly, the interleaving methods for the PWM carriers are studied in terms of the current ripple according to the interleaving angle. Thirdly, a method to reduce the phase current ripples caused by the coupling effect is proposed. The FFT analysis is performed to show the effect of the interleaving.