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

In this article, we propose an analysis and controller design of a bidirectional bridgeless single-stage dc/ac converter with high-frequency link and low part count. The 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 zero voltage switching (ZVS) turn-
on
of all the switching devices. The proposed controller has a reduced total harmonic distortion (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 the previous pieces of literature, simple and powerful continuous-time tools were not used to design the closed-loop system. In this article, a novel continuous-time generalized average model 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.