Second Harmonic Voltage Suppression for <i>LLC</i> Converter in Dual-Stage Single-Phase Rectifier Based on Voltage-Oriented State Plane Feedforward Control
Jie Chen, Junzhong Xu, Haiguo Tang, Yuxuan Bi, Yunfeng Peng, Yong Wang
Abstract
Second harmonic output voltage ripple in a single-phase grid-connected rectifier can degrade the system's performance. In this letter, a voltage-oriented state plane feedforward control is proposed to suppress the second harmonic output voltage ripple for the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> converter, which serves as the backstage of the dual-stage single-phase rectifier. Herein, the desired switching frequency of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> converter is predicted online through geometrically simplified state plane analysis, and thus the voltage control loop gain at the second harmonic frequency can be increased. The proposed control strategy features a fast dynamic response and is immune to grid frequency deviation. Both simulation and experimental results fully confirm the theoretical analysis.