Targeted-Subharmonic-Eliminating Pulse Density Modulation for Wireless Power Transfer Systems

This letter proposes a targeted-subharmonic-eliminating pulse density modulation (PDM) method for series-series (SS) compensated wireless power transfer (WPT) systems. The subharmonic frequency components which excite abnormal current oscillations in PDM-controlled WPT systems are eliminated through a specially designed noise transfer function (NTF). The proposed method is simple to implement in both primary and secondary sides of WPT systems and exhibits a certain tolerance to deviations caused by inaccurate coupling coefficient identification. Experimental results demonstrated the effectiveness and robustness of the proposed method in suppressing abnormal current oscillations and reducing the fluctuations in current amplitudes. The current fluctuations are reduced from over 60% to less than 22% over the entire test range.