Analysis of Nonisolation Characteristics and Effect of Electric Field Couplers in Dynamic CPT Systems

The nonisolated characteristic of capacitive couplers in capacitive power transfer (CPT) systems can lead to significant voltage discrepancies between the two sides. This paper analyzes the reverse current phenomena caused by the nonisolated characteristic in dynamic capacitive power transfer (DCPT) systems. A capacitive coupler model that considers the voltage between two transmitters (operating and standby) of the DCPT system is developed. In the DCPT system designed within this paper, the RMS voltage to ground for the two ports on the standby transmitters is calculated to be 1577.62V and 1557.68V, respectively. When the standby inverter is activated, the reverse-biased diode of the MOSFETs within the inverter is momentarily turned off at the initial moment, which is akin to a circuit break. According to the calculation results presented in this paper, the potential becomes larger than
$E_{\text{dc}}$
or drops below OV to turn the diode on, thereby switching on the diode of the standby inverter and generating reverse current. The model proposed in this paper elucidates the mechanism behind the reverse current generation in the standby inverter, and its accuracy is validated through simulation research.