Phase and Neutral Current Ripple Analysis in Three-Phase Four-Wire Split-Capacitor Grid Converter for EV Chargers

The current switching ripple in a three-phase four-wire split-capacitor converter is analyzed in this paper for all the four ac output wires in relation to both balanced and unbalanced working conditions. Specifically, analytical formulations of the peak-to-peak and root mean square (RMS) current ripples are originally evaluated as a function of the modulation index, separately for the three phases and the neutral wire. Initially, the single-carrier sinusoidal pulse width modulation (PWM) technique is outlined, as it generally concerns a straightforward and effective modulation. With the aim of mitigating the current ripple in the neutral wire, the interleaved multiple-carrier PWM strategy is adopted, also avoiding any repercussion on the phase one. Numerical simulations and experimental tests were carried out to verify all the analytical developments.

Automated summary

This paper analyzes the current switching ripple in a three-phase four-wire split-capacitor converter and proposes the single-carrier sinusoidal PWM modulation technique and interleaved multiple-carrier PWM strategy to mitigate the current ripple in the neutral wire. Numerical simulations and experimental tests were conducted to verify the analytical developments.