Analysis and experiment on harmonic current distortion in wireless power transfer system using a diode rectifier

Wireless power transfer (WPT) via magnetic resonance coupling provides highly efficient mid-range transmission. Its transmitting power can be controlled using a diode rectifier and a DC-DC converter on the secondary side. Previous research replaces the load and the rectifier circuit with an equivalent load resistance or a fundamental harmonic sine wave voltage source to analyze the charging power of WPT. In such a case however, the effect caused by the rectifier circuit becomes unclear because the harmonic components are neglected. As a result, the theoretical charging power and its true value have an error due to the harmonic current distortion. In this paper, a novel WPT circuit model is proposed for the analysis of the harmonic current distortion on the secondary side. The proposed model uses the secondary voltage as the input variable of transfer functions and makes clear the effect caused by the rectifier circuit. Experiments demonstrate that the harmonic current distortion is increased with the increase in the secondary voltage. These results accord with the analysis using the proposed model and verify the effectiveness of the proposed model.