Study on Frequency Tracking and Active Rectifier Constant Voltage Output of Full Digital Phase-Locked Loop for Wireless Power Transmission System

Frequency tracking is one of the effective solutions to improve the transmission efficiency and output power of Magnetically Coupled Resonant Wireless Power Transmission (MCR-WPT) systems. Investigating the detuning control strategies is crucial for enhancing the transmission performance of WPT systems. Therefore, an equivalent circuit model of the MCR-WPT system is established for the SS topology, and the mathematical expressions for the output power and transmission efficiency of the MCR-WPT system were derived. The voltage and current equations of the WPT transmitter and receiver are established, and the system impedance angle expressions are solved. The effects of frequency offset, impedance change, coil axial offset, radial offset and angular offset on the system impedance angle are explored through numerical solutions. Based on this, a frequency tracking control strategy of differential phase identification digital phase-locked loop was proposed. In view of the constant voltage output for MCR-WPT system, a constant voltage output control strategy based on half-controlled active rectifier was proposed. Finally, an experimental platform was built to verify the correctness of the proposed control strategy.