Frequency-Splitting-Free Wireless Power Transfer via Hybrid Frequency Control and Asymmetric Voltage Cancellation

In this article, a hybrid frequency control and asymmetric voltage cancellation (HFC-AVC) strategy is presented to address frequency-splitting challenges in wireless power transfer (WPT) systems. Although WPT systems with varying operating frequencies offer advantages in hardware simplicity, existing frequency control approaches suffer from the frequency-splitting phenomenon. The proposed HFC-AVC strategy is developed to tackle this issue. First, the frequency-splitting phenomenon is analytically investigated under detuned conditions, and a criterion is established to determine the critical load resistance that triggers splitting. Based on this, the constant current-constant voltage (CC-CV) battery charging process is divided into two regions: the frequency-splitting region and the frequency-splitting-free region. In the frequency-splitting region, constant frequency control is adopted, where output regulation is achieved through AVC modulation, while zero-voltage switching (ZVS) is maintained via an optimized detuning strategy. Conversely, in the frequency-splitting-free region, variable frequency control is applied, with output regulation achieved by tuning the frequency. The proposed approach enables wide-range output regulation across the entire CC-CV process while maintaining full-range ZVS, without requiring any additional hardware circuits. More importantly, it overcomes frequency splitting challenges. Experimental results confirm that the proposed strategy effectively achieves CC-CV charging with full-range ZVS, and attains a peak dc-to-dc efficiency of 96.34%.