A Hybrid Modulation Strategy Based on Tandem-Half-Bridge WPT Converter for Efficiency Optimization Within Wide Operation Range

The efficiency of the wireless power transfer (WPT) system is highly dependent on the load resistance. To meet the demand of wide load variation, traditional methods employ dual-side control with multivariable to improve the efficiency for light loads. However, these methods often necessitate high-frequency signal synchronization and involve complex control. Therefore, a crucial challenge in WPT systems is to maintain high efficiency over a wide load range while using a simple control method. To address this research gap, a tandem-half-bridge (THB) WPT converter is proposed to improve the system efficiency and reduce the switching drain-source voltage. Based on the THB WPT converter, a hybrid modulation strategy is proposed, and only pulse frequency modulation or phase shift modulation is used in each operation mode. Additionally, a unified pulsewidth modulation generated method for three modes is given, which can be better applied in the digital controller. To validate the effectiveness of the proposed THB WPT converter under the hybrid modulation strategy, we construct a 1.8-kW experimental prototype. The experimental results demonstrate a peak efficiency of 95.26%. Furthermore, the efficiency under light load is up to 10.36% higher than the traditional full-bridge and half-bridge (FB&HB) converter under the mode switching strategy.