Wireless charging technology greatly improves the flexibility and convenience of electric vehicles (EVs) charging. The alignment of coils directly affects the performance of the wireless charging system. For the above problems, we proposed a mesh-based accurate positioning strategy for EV wireless charging coils. The strategy takes the center of primary coil as the origin and divides the meshed reference points in the plane of secondary coil. It is based on voltage induced by detection coils installed on the secondary coil. The centimeter-level positioning of the secondary coil is realized in the X and Y directions of the horizontal plane. The effectiveness of the proposed strategy is verified by simulations and experiments. Without considering the rotation, the maximum error is within 3cm in 5cm mesh width. The positioning strategy helps to align coils and improves transmission performance. It is also helpful for automatic parking, unmanned vehicle, and other industrial applications.

In order to improve system reliability and reduce device thermal fatigue failure in multi-load wireless power transfer(WPT) systems for electric vehicles, the implementation of junction temperature fluctuations suppression strategy for SiC MOSFETs is necessary. However, current methods are relatively lacking, and active thermal management has not been used in WPT systems. In this paper the relationship between circuit parameters and junction temperature of SiC MOSFET is analyzed. In particular, a junction temperature fluctuation tracking suppression strategy for SiC MOSFETs is proposed, which consists of a coarse and a fine adjustment stage. As for the former, a shunt capacitor bank switching method is implemented. In order to compensate for the coarse adjustment defects in the small adjustment range and poor effect, in fine adjustment stage, a changing driving voltage method is proposed. Lastly, a 5kW multi-load WPT system is built for verification. Experimental results show that the proposed strategy has obvious effect on the suppression of junction temperature fluctuation and keeps temperature near the target temperature. Benefiting from this, the maximum 13.9°C junction temperature fluctuation is completely eliminated when the power fluctuations within 36.1% of the rated power, and the heat load of each SiC MOSFET can be independently adjusted.

Recently, bidirectional wireless power transmission (BD-WPT) technology has been increasingly used in electric vehicles (EVs) charging and discharging applications to realize interactive energy feedback between EVs and the power grid. Although the efficiency of BD-WPT system has been impressively improved, it still heavily relies on complex control methods. This article proposes a simple but effective control method to achieve maximum efficiency with zero reactive power. Specifically, a resonance judgment and phase synchronization network is employed to ensure the resonance performance and synchronization of the bilateral control signals, which realizes the stead autostarting of the secondary side and guarantees the disentanglement between power control processes as well. With the help of voltage ratio design and symmetric phase-shift between bilateral inverters, the optimization efficiency is well achieved. The results of the experiment and simulation match well, showing the effectiveness of the proposed method in this article.

Junction temperature fluctuations are the most important factor in accelerating the aging and failure of SiC MOSFETs. An effective way to improve the reliability of SiC MOSFETs is to suppress or even smooth out the junction temperature fluctuation. This brief proposes an active thermal management technique to adjust the turn-off loss in SiC MOSFETs based on adjusting the buffer capacitance, thus smoothing out the junction temperature fluctuation. To realize online continuous capacitor adjustment, this brief further proposes an equivalent adjustment of the buffer capacitor based on the use of a delay switch. Using the SiC MOSFET in a 6 kW high-frequency inverter as an example, experimental results show that the proposed active thermal management technology can be used to completely smooth out the junction temperature fluctuation generated by a rated load fluctuation of 37.5%.

In the secondary side of the wireless power transfer (WPT) system, the active rectifier helps increase efficiency and adjust output characteristics. However, there is a certain probability that oscillation problems will occur, especially in an LCC-LCC system. A closed loop that causes oscillations in the circuit is figured out. And with the established discrete system mode, the dynamic oscillation conditions are presented in a wide operating range. The theory and simulation show that the proposed improved control method based on the resonant filter breaks the original oscillation closed loop and effectively suppresses oscillations. Finally, the proposed method is applied in an experimental prototype, and the stable operating range of the improved prototype is significantly expanded.