High-Efficiency Bidirectional Grid-Tied Converter Using Single Power Conversion With High-Quality Grid Current

Abstract

This paper presents a high-efficiency bidirectional grid-tied converter using single power conversion with high-quality grid current and a control system for it. The proposed converter is composed of a bidirectional flyback dc-dc converter and an unfolding bridge circuit. By adjusting the PWM signal of the flyback, the proposed converter performs bidirectional power conversion between the grid and energy storage device in only one step. The control system consists of a feed-forward controller, a linear feedback controller with a low-pass filter, and a repetitive controller. The development of the proposed control system considers the inherent dynamic characteristics of the converter, thus overcoming the constraints on designing feedback control gains originating in right-half-plane zero and LC filter dynamics. Therefore, the control system ensures desired reference tracking and disturbance rejection performances while satisfying stability requirements. In conclusion, the proposed converter can achieve high conversion efficiency through a single power conversion, and its control system makes the implementation of the single power conversion in the proposed converter feasible. The theoretical analysis for the proposed converter and its control system is described. Finally, experimental results using a 250 W prototype are represented to confirm the validity of the proposed converter and its control system.