Resonant coil matrix shielding for dynamic WPT systems

In this article, a magnetic shield for automotive Wireless Power Transfer (WPT) systems is proposed. Its innovative feature consists in the positioning of the shield, that is part of the Ground Assembly (GA) of the WPT system. Passive coils, assembled in an array-like structure to build the shieldsproperly located near the transmitting coils are investigated. Currently, there are a variety of shielding methods, each of them with its peculiar feature. The proposed method is simple and does not increase the transmitting and the receiving coil sizes, a constraint that is often critical from a practical and an economical point of view. The main characteristic of the proposed shielding method is the location of the shielding coils on the same level as the GA. The results here presented are validated by Finite Element (FE) based simulations and are referred to an experimental prototype of wireless charging systems for electric vehicles operating at 85 kHz with a transmitted nominal power of 3.3 kW. The results show that the proposed shield reduces the leakage magnetic flux density in the system up to 37% with a marginal impact on the transmission efficiency, complying the SAE J2954 international standard.