The Start-up Dynamic Analysis and One Cycle Control-PD Control Combined Strategy for Primary-Side Controlled Wireless Power Transfer System

This paper proposes a novel dynamic analysis and a switching converter control strategy for primary-side voltage controlled wireless power transfer (WPT) system. First, the modeling of the high-order double-sided LCC resonant converter is carried out. By dividing the resonant circuit into three equivalent parts and analyzing their transfer functions, respectively, the approximated boundary of the start-up transient time of the WPT stage is solved analytically. Furthermore, in order to ensure the swiftness of the transient response of the WPT system, a novel control strategy combining one cycle control and proportional differential control (OCC-PD) is proposed. By using switching flow-graph technique, the transfer functions of the buck converter applying the OCC, proportional integral differential, and OCC-PD control are obtained. The superiorities of the OCC-PD are proved through the analytic expressions of dynamic characteristic parameters. The input impedance of the WPT stage cascaded to the buck converter is also derived to evaluate the performance of the whole WPT system. Finally, simulations and experiments are carried out through a 6.6-kW two-stage primary-controlled WPT prototype. The results are in accordance with the theoretical analysis and validate the superiorities of the proposed OCC-PD strategy in the aspects of the transient response and the robustness.