Determining matching capacitance for a variable distance WPT system considering ZVS

Wireless Power Transfer (WPT) systems are widely used today across various applications. Due to their interoperability, there are many instances where the receiver can vary, and consequently, the air gap may differ depending on the application. In such distance-variable WPT systems, the self-inductance of the transmitting and receiving coils can change, which means that zero-voltage switching (ZVS) is not always guaranteed. In this paper, we propose a method to determine the matching capacitor that is sufficient to ensure ZVS in a distance-variable system. According to our theoretical approach, the matching capacitance should be determined for the farthest air gap. The proposed idea was verified through experiments, and the results demonstrate that the ZVS is guaranteed within the specified range of variable distances.