Frequency Adaptive Discrete Repetitive Controller Design for Electric Vehicle Charger

Abstract

This article introduces the design of a bidirectional two-stage, on-board electric vehicle (EV) charger controller. As with the growing trend of EVs, their widespread use may compromise grid quality, leading to the demand for a stable, simple, and better control system. However, some controllers provide sluggish responses and fail to compensate for harmonics. Therefore, to mitigate the grid current harmonics, a repetitive controller (RC) has been analyzed. Within a specified integer period, for any periodic signal, the RC may accomplish tracking of zero steady-state error. However, if grid frequency varies under the permissible range the performance of conventional RC degrades. Therefore, a Lagrange interpolating polynomial-based fractional-order RC has been implemented with a fixed sampling rate to enhance its performance during frequency fluctuations. PLL estimates the frequency, which is fed back to update the controller's resonant frequency. Then, using Lagrange interpolating the polynomial the fractional delay is approximated. The proposed controller has been designed within a MATLAB environment. Its performance has also been probed in a real-time experimental setup with OPAL-RT (4510).