Hybrid Control Based on Pulse Density Modulation and Asymmetrical Voltage Cancellation for WPT Systems

For wireless power transfer (WPT) systems, traditional pulse density modulation (PDM) can easily induce oscillation during continuous power adjustment, leading to serious current ripple. In this article, the oscillation phenomenon is investigated based on the system’s impedance characteristics. Subsequently, a hybrid modulation strategy based on the PDM, and asymmetrical voltage cancellation (AVC) is proposed. This strategy not only effectively mitigates oscillation issues during continuous power regulation, but also improves the performance of traditional AVC in the frequency control and triple phase shift (TPS) control application. For the frequency control, the switching frequency scope to achieve ZVS is narrower than that of the traditional AVC, which is conductive to meet the SAE J2954 standard. For the TPS control, the hybrid modulation enables the WPT system with higher system efficiency than the traditional AVC. Experimental results have been presented to verify the theoretical analysis.