A Dynamic Tuning Method for ZPA Frequency Operation of MEU-WPT System by DC Input Voltages Regulation

The multiexcitation units wireless power transfer (MEU-WPT) technology provides a flexible modular-based solution for high power applications with large coupling tolerances. However, complicated cross-coupling and multi-variable parameters may cause the drifting of the resonant operating frequency due to equivalent impedance changes. This article proposed a dynamic tuning method for zero phase angle (ZPA) frequency operation of a MEU-WPT system at a constant frequency. The equivalent impedance of a WPT system with multiple excitation units is analyzed and found to be determined by the coupling coefficient, load resistance, and dc input voltages. Theoretical modeling analyses are conducted to show the ability to maintain a constant ZPA frequency against load and coupling variations by dc input voltage control. Moreover, a practical MEU-WPT system is built with two excitation units, and the experimental results demonstrate that ZPA frequency operation at 90 kHz is achieved with improved power efficiency.