Eigenfrequency Identification Scheme for Strongly Coupled Series-Parallel Compensated Wireless Power Transfer System

Abstract

This brief proposes an eigenfrequency identification scheme (EIS) based on circuit theory in time domain for a series-parallel compensated wireless power transfer (SP-WPT) system with the pure capacitance filter. In the SP-WPT system, the high nonlinear features (HNFs), including the strong magnetic coupling and diode rectifier influence the system operation by causing the distortion and discontinuity of the voltages and currents. Thus, the effectiveness of fundamental harmonic approximation is influenced, especially when the impact of HNF becomes serious under the strong magnetic coupling and light load conditions. Consequently, the time domain analysis is developed for the diode rectifier-equipped strongly coupled SP-WPT system. Three operation modes of the diode rectifier are analyzed in detail, where the influence of constant dc-link voltage is investigated. Besides, the two eigenfrequencies of the SP-WPT system can be analytically calculated by using the coupling coefficient, k and resonant frequency in the proposed EIS, which reveals the relationship between k and the operation characteristic of the system. Eigenfrequency is the inherent characteristic of the system, which is different from odd and even frequency. Finally, the effectiveness and accuracy of the proposed EIS are verified by experiments on an SP-WPT platform.