Modelling and improvement of oscillation problem in a double-sided LCC compensation network for electric vehicle wireless power transfer

Abstract The double-sided LCC compensation network shows high performances in electric vehicle wireless power transfer (EV WPT) applications owing to its constant output current, low voltage stress and other good characteristics. In order to achieve full power and high-efficiency energy transmission within the specified range of coupling and battery voltage, a controlled rectification scheme became a trend in EVs manufacturers and standards. However, a current oscillation problem emerges in a double-sided LCC system when employing a circulating current control method for the controlled rectifier. This paper proposes a mechanism to understand the oscillation phenomenon caused by the inter-harmonics and a positive feedback scheme. The amplification effect of circuit admittance is believed to be the key cause of the inter-harmonics. Therefore, an oscillation improvement is proposed in this paper by adding an inductor and a capacitor to the secondary LCC network, minimizing the admittance amplification effect. A comprehensive simulation and experimental validations under different rectifier duty cycles, coupling positions and load resistances, confirmed the effectiveness of the proposed method. Interestingly, the optimized system expanded the safe operating region and reduced the oscillating operating points from 18 to 8 out of the 27 possible conditions.