A 2m Quasi-Wireless Capacitive Power Transfer (CPT) System Using Earth Ground as the Current-Returning Path

This paper proposes a quasi-wireless capacitive power transfer system to achieve long-distance power transfer. Compared to the conventional four-plate CPT system, the proposed quasi-wireless system only requires two metal plates, and the other two plates are replaced by the earth ground, which provides a current-returning path. In long-distance power transfer applications, the coupling capacitances between plates are affected by the appearance of the earth ground, which are analyzed by the method of mirror images. Based on the circuit model of the coupler, a double-sided LC compensation circuit is used to realize a long-distance and loosely-coupled CPT system. Its output properties, including output power and efficiency, are presented in detail. Two 0.91m×0.91m aluminum plates are used to implement the proposed two-plate system. Experimental results show that the prototype can realize 216.5W power transfer with 52.2% dc-dc efficiency at an air-gap distance of 2.0m. When the distance is 1.5m, the efficiency can reach 67%, and when the distance increases to 2.5m, the system can still maintain an efficiency of 20%.