Design Consideration and Comparison of Wireless Power Transfer via Harmonic Current for PHEV and EV Wireless Charging

Wireless power transfer (WPT) using only harmonic current for plug-in hybrid electric vehicle and electric vehicle is a fairly new concept. The frequency limitation of most high-voltage high-current IGBTs is around 20 kHz which also limits the system frequency of the transformer. The series resonant converter (SRC) is widely used in WPT application for its simplicity and high efficiency. Due to the bandpass filter characteristic of the resonant network, the SRC allows one frequency component to pass while the other frequency components are greatly attenuated. By deliberately selecting one harmonic current as the power carrier, the system frequency can be raised up to several times with the same switching frequency. Thus, a higher system frequency contributes to a more compact system. However, a high-order harmonic system results in high conduction loss on the switches, and it leads to a tradeoff between the system size and efficiency. This paper provides a theoretical and practical design for a system using harmonic current. Furthermore, a comprehensive comparison between different harmonic systems is carried out. A 1-kW SRC prototype with a 20-cm air gap is built to verify the proposed method.