ALLPCB
Background
Magnetic resonant coupling for wireless power transfer (WPT) is a key technology for enabling contactless charging. It is widely used in devices such as smartphones, medical equipment, and electric vehicles (EVs). However, high-power WPT systems for EVs require strong magnetic fields, and the resulting leakage fields can pose risks. Therefore, developing effective magnetic shielding methods is critical for the application of EV WPT systems.
System Overview
Balancing magnetic shielding effectiveness with transmission efficiency is a common challenge in EV wireless power transfer systems. To address this, a strongly coupled magnetic shielding structure has been proposed to reduce magnetic leakage while improving efficiency. This research analyzes the effect of shielding coil impedance on system leakage and efficiency, leading to a new optimization method for leakage reduction. Using this method, coil parameters were determined to meet design requirements. A prototype EV wireless charging system was developed, and its performance was validated through simulation and experiments, confirming the effectiveness of the proposed structure and method.
Key Features and Optimization Method
- A strongly coupled shielding coil structure is used to reduce the leakage magnetic field of the WPT system. When the shielding coil is added, its impedance is controlled to a capacitive state, which enhances the equivalent mutual inductance between the transmitter and receiver coils. Compared to traditional passive inductive shielding, this method improves transmission efficiency while simultaneously weakening the overall system leakage field.
- A comprehensive optimization method for WPT system magnetic leakage is introduced. The process involves optimizing the parameters of the transmitter, receiver, and shielding coils to reduce leakage and increase efficiency. A novel aspect of this method is the inclusion of an optimization step for the ideal shielding capacitance and optimal load, which expands the adjustable range of the optimization. This allows for the determination of optimal parameters that achieve both low magnetic leakage and high transmission efficiency for EV wireless charging.
Applications and Future Prospects
The proposed leakage optimization structure and method can maintain high transmission efficiency and safe magnetic field leakage levels even with a certain degree of coil misalignment. This design does not use ferrite cores, which reduces both the production and operating costs of the WPT system while improving energy efficiency. It is particularly relevant for static charging systems for electric vehicles. The structure has been successfully applied to static EV charging systems. Future research will focus on developing electromagnetic shielding methods for dynamic wireless charging of EVs to further promote the broader application of WPT technology in the automotive sector.
