EMI Suppression Method for LCC-S MC-WPT Systems by Parameter Optimization

The excitation current harmonics of the magnetic coupling wireless power transfer (MC-WPT) systems and switching noise will cause electromagnetic interference (EMI) through the coupling coils. This article proposes an interference source suppression method from the perspective of parameter design. The total harmonic distortion (THD) of the current in the primary and secondary coupling coils is derived to evaluate harmonic interference. To decrease the difficulty brought by multidimensional and multiobjective parameter design, the relationship between the Litz wire diameter and the electrical parameters of the coupling coil, such as self-inductance, mutual inductance, and internal resistance, is derived. On the premise of meeting the transmission requirements, a method for reducing switching noise by adjusting the turn- off current is proposed, and an objective function for balancing EMI and efficiency is established. Correspondingly, a system parameter optimization process is formed. Finally, a 1 kW, 85 kHz, 310 V LCC-S MC-WPT experimental platform is built up, and the effectiveness of the proposed method is verified through performance comparison of five groups of design parameters. Experimental results show that compared with the unoptimized parameter, the system with the optimized parameter achieves a current THD of the primary and secondary side coils decreasing to 0.56% and 3.09%, respectively. High-order harmonic magnetic field and switching noise near the coupling coils have been reduced by 15 dB and 20 dB.