A bidirectional moving field inductive power transfer system for electric vehicles

A system concept for bidirectional non-contact inductive power transfer between a supply line embedded in the road and electric vehicles is described. The system allows high-speed long-range cruise with a minimum on-board stored energy. The inductive power transfer (IPT) is performed over a transformer system formed by a linear array of primary coils embedded in the roadway and a secondary coil in every electric vehicle. Primary and secondary coils are loosely coupled. The resulting high stray inductances are capacitively compensated. To minimize power loss only the primary coils under the vehicles are activated. The IPT system is operated as a switched resonant converter controlled by the primary and secondary coil currents. By this way power transfer in both directions can be accomplished. When switching from one primary coil to the subsequent primary coil on the track in order to follow the moving vehicle the electric and magnetic energies stored in the coils and capacitors are passed on to the subsequent coils and capacitors in order to avoid loss of the stored energy.