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.

Existing System

Modulation, Maximum Power Point Tracking.

Proposed System

In this paper, the bidirectional grid-tied flyback converter using single power conversion and its control system are presented. The proposed converter comprises a bidirectional flyback converter and an unfolding bridge. It performs bidirectional power conversion between the grid and the energy storage device only a single step. The bidirectional flyback operating in the CCM region enables the converter to improve the power capability and the power conversion efficiency relative to the converters operating only in DCM region. The control system of the converter is developed considering the dynamic features of the proposed converter, that it consists of a feed-forward controller, a linear feedback controller with a low pass filter, and a repetitive controller. The developed control system can overcome the constraints on the feedback control caused by the inherent dynamic characteristic of the proposed converter and ensure desired reference tracking and disturbance rejection performances with desired stability. Moreover, the proposed converter has simpler control system compared to the conventional double conversion method which requires two individual control system. In conclusion, the proposed converter can achieve high efficiency with the single power conversion technique and its circuit configuration, while the developed control system gives the feasibility of the single power conversion to the proposed converter and provides high quality grid current.

Architecture

Proposed bidirectional grid-tied converter using single power conversion technique