Single-Stage Isolated DC/AC Converter With Continuous Dynamic Model and Controller Design

Abstract

This article proposes an analysis and controller design of a bidirectional bridgeless single-stage DC/AC converter with high frequency-link and low part count. Dual phase-shift control is proposed to control and modulate the AC power and to minimize the Root Mean Square (RMS) of the transformer current. Furthermore, the phase shift angle is chosen to assure wide range of ZVS turn-on of all the switching devices. The proposed controller has a reduced THD at the output AC current without zero-crossing spikes. A continuous-time average model, that well predicts both transient and steady-state relations between the high-frequency AC link and the DC side, is needed to simplify the controller design. Since complex discrete-time models were used in previous literatures, simple and powerful continuous-time tools were not used to design the closed-loop system. In this paper, a novel continuous-time Generalized Average Model (GAM) is proposed. The derived model precisely predicts the high-frequency state variables of the converter, including a simple formula for the transformer current RMS value. The formula is used to minimize the transformer current to reduce the losses. Moreover, the transient analysis and the closed-loop control design are presented. A prototype circuit is tested to verify the performance of the proposed control scheme with the proposed isolated single-stage DC/AC converter.