Oscillation Frequency Manipulation in Autonomous WPT Systems With Series–Series Compensation

The autonomous wireless power transfer (WPT) system with series–series compensation has the advantage of the output power being approximately independent of variations in the coupling coefficient and load within the bifurcation region. However, the system encounters the issue of nonuniqueness in steady-state oscillation frequency, influenced by factors, such as varying system parameters, unpredictable external disturbances, and initial conditions. To overcome this issue, this letter proposes a relay-switching technique for manipulating the oscillation frequencies of autonomous WPT systems. This technique utilizes an adjustable relay threshold to dynamically modify the phase relationship between the input voltage and current, guiding the system to operate at the desired oscillation frequency. Complementary to the relay-switching technique, a gain-shaping strategy is presented to enhance the current gain at the target frequency, thereby increasing the possibility of convergence to that frequency. Finally, an experimental setup is built to verify the effectiveness of the proposed method. A video demonstrating the switching of different steady-state oscillation frequencies is attached to this letter.