Constant DC-capacitor voltage-control-based harmonics compensation strategy of smart charger for electric vehicles in single-phase three-wire distribution feeders

Abstract

This paper discusses harmonic current compensation of the constant DC-capacitor voltage-control (CDCVC)-based strategy of smart chargers for electric vehicles (EVs) in single-phase three-wire distribution feeders (SPTWDFs) under nonlinear load conditions. The basic principle of the CDCVC-based harmonics compensation strategy under nonlinear load conditions is discussed in detail. The instantaneous power flowing into the three-leg pulse-width modulated (PWM) rectifier, which performs as a smart charger, shows that the CDCVC-based strategy achieves balanced and sinusoidal source currents with a unity power factor. The CDCVC-based harmonics compensation strategy does not require any calculation blocks of fundamental reactive, unbalanced active, and harmonic currents. Thus, the authors propose a simplified algorithm to compensate for reactive, unbalanced active, and harmonic currents. A digital computer simulation is implemented to confirm the validity and high practicability of the CDCVC-based harmonics compensation strategy using PSIM software. Simulation results demonstrate that balanced and sinusoidal source currents with a unity power factor in SPTWDFs are obtained on the secondary side of the pole-mounted distribution transformer (PMDT) during both the battery-charging and discharging operations in EVs, compensating for the reactive, unbalanced active, and harmonic currents.