Selected harmonic elimination‐derived multi‐frequency pulse width modulation control strategy for multi‐load MCR WPT system with single transmitting coil

Abstract

Magnetically coupled resonant wireless power transfer (MCR WPT) has become the research focus in recent years because of its safety, simplicity and high efficiency. In multi-load applications, the ‘one-to-one’ charging scenario is difficult to meet the requirement of load diversity, and the development of the ‘one-to-many’ charging has become increasingly important. In this study, a multi-load MCR WPT system with single transmitting coil and multiple receiving coils was investigated. To discriminate the loads for targeted power distribution, each receiving coil cascaded by the load is designed to operate at an individual frequency. For this purpose, a single-phase full-bridge inverter and a multi-frequency pulse width modulation (MFPWM) control strategy were used to generate a multi-frequency mixed excitation voltage that servers as the input of the single transmitting coil. In view of the different voltage features, two control modes defined as the unipolar and the bipolar modes were presented, and the characteristics of these two modes were analysed. To further reduce the harmonic content in the voltage waveform, a phase-shifted MFPWM control strategy was proposed, and the design guideline of the phase-shifted angle was given. Finally, a dual-load MCR WPT system was taken as an example for the experimental verification, which confirms the correctness and effectiveness of the proposed control strategies.