A Single-Stage Dynamically Compensated IPT Converter With Unity Power Factor and Constant Output Voltage Under Varying Coupling Condition

Leakage and magnetizing inductances of a loosely coupled transformer are constantly changing due to the relative positions of the primary and secondary transformer windings in inductive power transfer systems. In order to counteract the nonnegligible inductances and extract desirable characteristics from the system, various compensation networks have been proposed to obtain unity input power factor and constant output voltage for minimum reactive power and ease of control for battery charging or other power electronic applications. However, most of the existing control methods with fixed compensation networks, which are usually designed for a specific coupling coefficient, have failed to fulfill both requirements simultaneously due to the mismatch between the resonant frequencies of the networks after the deviation of the designed coupling condition. In this article, a dynamic series/series-parallel compensation network based on a switch-controlled capacitor is proposed to rematch the series- and parallel-resonant frequencies of the network such that the magnetizing inductance can be adaptively compensated for different sizes of air gap/misalignment. By doing so, the requirements of load-independent output voltage and unity input power factor can be simultaneously fulfilled, while zero-voltage switching on the primary bridge is still maintained under different coupling conditions by a single-stage converter. An experimental prototype with the air gap ranging from 10-16 cm is built to verify the idea.