Modeling and Analysis of Magnetic Resonance Coupled Wireless Power Transfer Systems

Abstract

Magnetic resonance coupling (MRC) is a practical high efficient method for midrange wireless power transfer (WPT). In a MRC-WPT system, when the gap between transmitter (Tx) and receiver (Rx) is shorter than the critical coupling distance, the strong coupling will result in two natural resonance frequencies (frequency splitting). When increasing the gap between Tx and Rx, the coupling becomes weaker, and the split resonance frequencies become closer to each other and eventually merge into a single natural resonance frequency. As long as frequency splitting exists, a near to constant maximum power transmission efficiency can be maintained. In this paper, commonly used four-loop and two-loop WPT system configurations are analyzed and compared based on the simplified circuit model. An example symmetrical system simulation shows that with the same Tx, Rx, source and load, the four-loop system has longer transmission distance with relatively lower efficiency compare to the two-loop system. A 3-D physical model of 5-turn, 400mm outer diameter spiral shape four-loop WPT system is designed and simulated by using ANSYS® HFSS®. Operation distance of 550mm with nearly constant maximum transmission efficiency of 92.3% is achieved.