Analysis of Neutral Line Current Ripple Effective Value for Three-Phase Four-Wire Grid-Connected Inverters

This article provides a derivation for the neutral line current ripple effective value. For the three-phase four-wire inverter topology which has the neutral line connected with the split capacitor configuration, the neutral line current ripple affects the voltage ripple of the split capacitor. Excessive neutral line current ripple increases loss on the neutral line and necessitates using neutral inductor to reduce the ripple. Computer simulations with MATLAB/Simulink are shown to verify the theoretical analysis result. A 1kVA three-phase four-wire grid-connected inverter is built to demonstrate the neutral line current. Both simulations and hardware experimental results agree well with the theoretical analysis.