2-D alignment analysis of capacitively coupled contactless power transfer systems

Capacitive Power Transfer (CPT) technology has been proposed and investigated recently as an alternative contactless power transfer solution which has the advantages of being able to transfer power across metal barriers and having low standing power losses. Alignment between the primary and secondary plates is one of the most important factors affecting the performance of a CPT system because any misalignment may cause a significant drop in the output power. This paper analyses the effect of the coupling variation caused by misalignments of the coupling plates and suggests improvement methods for achieving better tolerance. A simple circuit model is established and the system voltage transfer function is derived to investigate the 2-D alignments. It has been found that placing the tuning inductor on the primary side of the circuit can greatly improve the misalignment tolerance between the primary and secondary plates and even increase the system output voltage. The theoretical analysis has been verified by simulation and experimental results.