A bidirectional wireless power transfer system for roadway powered electric vehicles

A wireless power transfer system for roadway powered electric vehicles (EVs) is presented. The system concept is using inductive coupling of primary coils arranged in a linear array in the roadway to secondary coils in each EV. The system is geared to minimize loss of the stored energy in the primary coils and compensation capacitors by passing the energy on to the subsequent coil and capacitor of the linear array. The inductive power transfer (IPT) system is operated as a switched resonant inverter controlled by the primary and secondary coil currents. By this way power transfer in both directions can be accomplished. We describe an extension of the moving field inductive power transfer (MFIPT) system by introducing a synchronous switched DC-DC converter. A rectangular AC power supply voltage is provided by a switched inverter from the underroad DC power supply. An automatic switching adapts to load changes and switches in optimum phase. Also the analysis of a basic IPT cell is discussed and efficiency considerations are given.