Study on frequency tracking for wireless power transfer system using magnetic resonant coupling

In the Magnetic Coupling Resonant Wireless Power Transfer(MCR-WPT) system, the efficiency will be reduced greatly by detuning. So after analyzing the phase relationship between the voltage and current of the primary and the secondary side, a new method is proposed using the Phase-Locked Loop(PLL) for the SS compensation topology of MCR-WPT system. Compared with the existing frequency tracking methods which based on the primary side voltage and current, the new method can always track the natural resonant frequency under any mutual inductance and load conditions and will not be affected by the frequency splitting phenomenon when the system operates in the over-coupled region.