A Frequency Design Method for Wireless Power Transfer Systems With PostStage DC–DC Converters

In wireless power transfer (WPT) systems, post-stage DC-DC converters—such as Buck converters—are commonly employed after the rectifier to achieve precise power regulation. This architecture effectively divides the system into two stages: the WPT transmission link at the front-end and the DC-DC converter at the back-end, interconnected via the DC bus on the receiver side. However, if the switching frequencies of the two stages are improperly designed or lack coordination, the system may suffer from undesired low-frequency oscillations in voltage or current waveforms. This letter proposes a frequency design methodology to mitigate inter-stage dynamic interactions in wireless power transfer systems. The underlying mechanisms of low-frequency oscillations are analyzed through steady-state circuit analysis and small-signal modeling. Based on these insights, a frequency planning strategy is developed to ensure system stability. Experimental results validate the proposed method, confirming its accuracy and effectiveness in practical applications.