A Double-Sided LCL-Compensated Network for the Strongly Coupled CPT System With Minimum Plate Voltage Stresses

In the conventional design of a double-sided LCL compensation network for the capacitive power transfer (CPT) system, two external capacitors are connected in parallel with the horizontal capacitive coupler, or a vertical capacitive coupler is required to reduce the resonant inductances. This approach results in a loosely coupled structure. The compensation inductor resonates with the whole coupler, inducing reactive power transferred from the primary to the secondary side, leading to higher voltage stresses on the plates, which inevitably increases the system complexity and susceptibility to air breakdown. This article proposes a double-sided LCL compensation network design method for the CPT system where no parallel-connected capacitors are required, thereby a strongly coupled structure can be obtained with a constant current (CC) output and input zero phase angle (ZPA) characteristics. By keeping the phase angle difference between the voltage vectors across the primary and secondary plates at 90 degrees, no reactive power is transmitted from the primary to the secondary side. Thus, the voltage stresses across the plates can be minimized. A 500 W prototype with a high coupling coefficient of 0.82 is established to verify the proposed system and an efficiency of 90% is achieved.