A Hybrid Modulation Strategy for <i>LCC</i>–<i>LCC</i> Compensated Bidirectional Wireless Power Transfer System to Achieve High Efficiency in the Whole Operating Range
Jun Huang, Xuguo He, Pengchong Huo, Rui Xu
Abstract
A hybrid modulation strategy is proposed for the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> – <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> compensated bidirectional wireless power transfer system ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> -BWPT), which aims to boost the efficiencies in the whole operating range. The basic operating modes of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> -BWPT with the hybrid modulation strategy are analyzed, and the unified discrete-time model is then established based on the full-mode operation, which can accurately describe the state variables under all operating modes. Based on the model, the criteria for optimal operation are put forward in consideration of three working processes of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> -BWPT, i.e., the constant current (CC) charging process, the constant voltage charging process, and the CC discharging process. The optimal control variables in three working processes are derived, respectively, which realize full zero-voltage switching operation and minimize the reactive current. On this basis, an optimal modulation strategy featuring high efficiency performance is proposed for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> -BWPT. Besides, a control method independent of the real-time wireless communication is developed for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> -BWPT with the optimal modulation strategy. Finally, a 1.2 kW prototype is applied, and experimental results verify the effectiveness of the proposed optimal modulation strategy, where the efficiencies are improved in the whole operating range.