A novel position sensorless power transfer control of lumped coil-based in-motion wireless power transfer systems

Traditional in-motion (dynamic) wireless power transfer (WPT) is based on elongated power transmitting tracks. It suffers from low efficiency, having complex and not fully utilized magnetic structures, among other drawbacks. In the case of lumped transmitter coils commeasurable in size with the receiver coil, which has been recently proposed for the in-motion WPT, the power transfer is intermittent with variable power transfer efficiency. Although it is characterized by a very high efficiency when the pads are aligned (>90%), high efficiency of the overall energy transfer will be maintained only if the transmitter coil is energized in a proper, synchronized manner with respect to the position of the receiver coil. Considering the actual state of communication and sensing technology, identification of the actual position of the receiver pad in realtime would be a very challenging task and no reliable solution has been proposed so far in the WPT arena. This paper provides a thorough analysis of the power transfer characteristics of an in-motion system with lumped coils, meaning the analytic description of time-varying power transfer and efficiency profiles. Possible compensation topologies are studied and the most suitable structure is selected. A control algorithm is proposed to control the amount of energy transferred to the receiver, without the utilization of any position detection system. The energizing profiles are designed to maximize energy efficiency, while at the same time transferring the required amount of energy to the receiver. The control algorithm is analyzed by using analytical modeling of the WPT system and then verified by MATLAB-Simulink simulation tool. A scaled-down hardware prototype is developed and employed to test the operation of the control algorithm for different transferred energies.