Unified Load-Independent ZPA Analysis and Design in CC and CV Modes of Higher Order Resonant Circuits for WPT Systems

This article proposes a general unified methodology for arbitrary higher order resonant circuits. With the proposed methodology, the equivalent circuits and the general resonant methods of the higher order resonant circuit are presented to realize the load-independent constant current (CC) and constant voltage (CV) outputs at two different load-independent zero phase angle (ZPA) frequencies. In addition, the corresponding regularized mathematical models of the constant output current and voltage and the purely resistive input impedances in CC and CV output modes are derived. All compensation topologies in both inductive and capacitive power transfer (CPT) systems have the essence of higher order resonant circuits. It means that the proposed methodology can be applied to investigate the load-independent output and input characteristics of any inductive power transfer (IPT) and CPT topologies. A 3.3-kW LCC -series-compensated IPT system for electric vehicles (EVs) was designed and manufactured to verify the theoretical analysis. The system operating frequencies in both the CC output with ZPA and the CV output with ZPA are in compliance with the SAE J2954 standard.