Multiple Output Inductive Charger for Electric Vehicles

Abstract

Multiple output chargers have widely been adopted in various electronic devices due to their benefit concerning cost, power density, and space for installation. On the contrary, inductive power transfer (IPT) has been applied increasingly in electric vehicles (EVs) since it is safer and more convenient as compared to conductive chargers. However, research works on multiple output chargers using an IPT system for EV charging applications are rarely presented. This paper proposes a new concept of a multiple output IPT charger, which can charge several output batteries independently and simultaneously by adopting only one full bridge inverter at the primary side combining with multiple transmitters. A total of two possible IPT-coil structures are analyzed, and the minimum distance between each channel's coils is determined to neglect the cross-coupling between them. A total of two options are proposed to attain a zero phase angle (ZPA) condition for the primary inverter of the proposed system. First option is to operate the compensation tanks of every output channel at exact ZPA frequencies. The other option is to let one channel work in the inductive region of its input impedance and other channel work in the capacitive region. By adopting an appropriate design, the reactive powers of these tanks can be nearly canceled by each other and the phase of inverter current can be nearly in-phase with the input voltage as a result. A total of two proposed options are compared to give recommendation whether option 1 or 2 should be selected according to various applications’ requirements. To simplify control complexity, IPT output current sources topologies are selected, compared, and analyzed to construct the proposed multiple output system in both above-mentioned options. Double-sided LCC and series–parallel topologies are adopted to demonstrate the proposed idea for options 1 and 2, respectively. In order to verify feasibility and validity of the proposed method, experimental results of two output channels with the total output power of 1.5 kW are provided. Experimental results indicate that the ZPA is achieved for the primary inverter with both of the above-mentioned options even under different load conditions. Some comparisons between the conventional and the proposed IPT charging structure in terms of cost, reliability, and complexity are included in the discussion section.