ZCS $LCC$-Compensated Resonant Inverter for Inductive-Power-Transfer Application

Inductive power transfer (IPT) is commonly used to transmit power from an extended loop (track) to a number of galvanically isolated movable pick-ups. To maximize the power transfer and minimize converter requirements, various compensation circuits have been proposed for both the track (primary) and the pick-up (secondary). This paper investigates the suitability of the LCC series-parallel compensation for IPT primary design. A new compensation-circuit design procedure is proposed that considers high-order current harmonics and results in inverter zero-current switching. The proposed compensation is compared with the classical compensation designed for zero phase angle between the inverter voltage and current fundamental components. Expressions for the bifurcation boundary, voltampere rating of reactive-compensation elements, and the current at the moment of switching are derived and analyzed. Analytical results are verified both via PSpice simulations and experimentally using a 1-hp MOSFET-based prototype.

I. Introduction

Inductive power transfer (IPT) is an efficient technique for transferring power with no physical contact between the source (primary) and the load (secondary or pick-up) [1]. This technology has found applications in many fields such as continuously powered electric vehicles [2], contactless electric-vehicle battery charging [3]–[5], material-handling systems [6], consumer electronics [7], and medical implants [8]. In IPT systems, electrical power is transferred from a primary coil to one or more isolated secondary coils that may move relative to the primary. A typical IPT structure is shown in Fig. 1. The system consists of three main components: a switching power supply, powered track, and pick-up. The system typically operates at a high frequency (in the 1–100 kHz range) to improve power transfer. Fig. 1.

Structure of a typical IPT system.