Nonisolation Model and Load Virtual-Grounding Design Method for Capacitive Power Transfer System With Asymmetric Four-Plate Coupling Interface

In most capacitive power transfer (CPT) systems, significant voltage difference between the primary and secondary coupling plates leads to a high load-to-ground (L2G) voltage, posing a risk of electric shock when individuals contact with the power receiver. However, existing models of capacitive couplers cannot describe the interplate voltage between different sides, making it difficult to analyze the L2G voltage. Moreover, existing methods for reducing the L2G voltage are only applicable to CPT systems with a symmetric coupler. This article proposes a nonisolated model of four-plate capacitive couplers to describe the interplate voltage and the L2G voltage. Based on this model, a compensation network with asymmetrically separated inductors (ASIs) is proposed. The high interplate voltage between the two sides can be canceled by ASIs, thus realizing the load virtual grounding for CPT systems. Finally, a prototype of the CPT system with an ASI-based compensation network is constructed. Experimental results demonstrate that the secondary side of the system is virtually grounded without affecting the system power transmission. In the optimal scenario, the L2G voltage is reduced by 66.7% from 120.6 to 40.2 V compared to existing designs. The L2G voltage reduction is also verified for CPT systems with different loads and voltage gains.