A direct three-phase to single-phase AC/AC converter for contactless electric vehicle charger

Abstract

This paper proposes an attractive direct line-frequency three-phase to a higher frequency single-phase AC/AC converter for a contactless electric vehicle charger. It removes a DC-link capacitor of a conventional AC/AC converter but has a smaller number of bi-directional switches than a matrix converter. It operates using injection and free-oscillation modes based on a zero-current switching mechanism. Circuit descriptions including a topology, commutations and a modulation strategy are discussed using some illustrations and diagrams. An on-off control is used to simplify control of resonant current. Simulation results to study some effects due to different coupling factor and load are then presented to show converter's performance and capabilities in contactless power transfer.

Initial Current Injection Method of a Direct Three-Phase to Single-Phase AC/AC Converter for Inductive Charger

“…It shows that the transition between injection and free-wheeling is performed at the zero-crossing of primary resonant current i p (t) [1].…”

“…One possible modulation strategy of the converter is described in Fig. 3, which is explained thoroughly in [1]. It utilizes injection and freewheeling oscillation during maximum absolute value of the three-phase input or,…”

“…A concept of an inductive-based contactless power transfer (ICPT) for an electric vehicle charger has been introduced in [1], [2] and [3]. It incorporates a direct three-phase to single-phase AC/AC converter connected to a resonant circuit.…”

“…It also accepts current reference signal, which is i * p (t) from the secondary pick-up circuit. The primary and secondary sides are magnetically coupled and the pick-up circuit contains a rectifier, a DC/DC converter, and a battery equipped with a voltage sensor [1].…”

A zero-crossing approximation of a distorted sinusoidal signal using analog circuit

“…The method involves toggling a power switch when current is not flowing through it. For an AC/AC converter with a resonant circuit given in [1] and [2], ZCS is performed during zero-current crossing (ZCC). Therefore ZCC information from the measured resonant current is needed.…”