A Developed PLL Control Technique for Distorted and Unbalanced Grid Voltages with a Three-Level NPC Converter-Based Off-Board Battery Charger

Abstract

As electric vehicle technologies advance, the number of off-board battery charger stations grows. Because they can provide a high-power level that is suitable for fast charging. The main factor of high-power transferring is power converters that should serve the grid power quality, including the reactive power, the power factor, and the harmonic distortion. In this paper, the development of the control algorithm for the three-phase three-level neutral point clamped converter-based off-board battery charger to support the utility grid when the three-phase grid voltage distortion or unbalance occurs is presented. By applying the standard phase-locked loop controller into the conventional control algorithm, it is possible to obtain more sinusoidal and balanced grid currents along with distorted or unbalanced grid voltages to conserve the grid power quality. The system operations, along with the comparison of the conventional control algorithm and the proposed algorithm, are provided in the simulation results.