A Soft-Switched Modulation for a Single-Phase Quasi-Z-Source-Integrated Charger in Electric Vehicle Application

A modulation for a single-phase quasi-Z-source-integrated electric vehicle charger (qZSC) system is proposed, which can achieve multiple zero-voltage-switching and zero-current-switching (ZCS) transitions without any auxiliary circuit. Though the modulation has a couple of hard-switching turn-off transitions, they occur at low current values. The switch of a quasi-Z-source network also can be turned on with ZCS. The inductor currents of the quasi-Z-source network operate in boundary conduction mode or discontinuous conduction mode to achieve all freewheeling diodes turned off naturally. Besides, there is no additional voltage stress and current stress on all switches in comparison with hard switching. Therefore, it is observed that the efficiency of the qZSC system using the novel modulation increases significantly. The details of operation principles for this soft-switching qZSC are analyzed. A simulation model is built and a 1.3-kW prototype is established to verify the proposed theory.