Modeling and control of bidirectional isolated battery charging and discharging converter based high-frequency link transformer

Abstract

This paper presents a new PWM technique for controlling a bidirectional isolated grid-tie AC-AC-DC converter. The proposed PWM technique has the ability to control the dc voltage and current in addition to achieving unity power factor at the grid side. In the first stage, a matrix converter is used to convert the grid three-phase voltage to a high-frequency square-wave single-phase voltage. In the second stage, an H-bridge converter is used to convert the high-frequency square-wave voltage to dc voltage. Therefore, a high-frequency transformer is used to link the matrix and the H-bridge converters. A conventional PI controller has been used to control the dc voltage and current for battery charging and discharging control. The grid current is always in-phase with the grid voltage for unity power factor. The effectiveness of the proposed technique has been verified experimentally using laboratory prototype.