Input Impedance Analysis of an LCLC type Capacitive Power Transfer Converter

In wireless power transfer systems, capacitive power transfer has emerged as an alternative to traditional inductive methods. It offers several advantages like the absence of losses in surrounding metallic elements due to Eddy currents. These systems have several filter topologies presented in the literature, one of them being the LCLC-compensator with a capacitive link filter, which is analysed in this paper. This topology consists of a double network of low-pass LC-type filter that helps, among other characteristics, to downsize some of the elements of the circuit. Additionally, it can boost the voltage in the plates of the capacitive link. The input impedance of the filter is derived for the case when the load does not affect the bifurcation frequencies of the filter and for the case when the input impedance is untied from the load. The analytical solution is compared with simulations and with experimental tests. The design parameters are analysed to determine the bifurcation frequencies.