Uniform-gain frequency tracking of wireless EV charging for improving alignment flexibility

Wireless power transfer is a promising alternative option for electric vehicle charging due to its non-contact operation. However, the magnetic coupling variation caused by misaligned coils limits its practical application. The output voltage can significantly drop due to the coupling change, lowering the power transfer capability. A uniform-gain frequency tracking control is proposed to keep the output voltage stable within a large misalignment. The uniform-gain control is achieved through voltage gain and impedance analysis across the frequency domain. Experimental results demonstrate that the voltage variation of uniform gain control is within 3.3% across the misalignment range of 200mm, while it is 57.2% for the same misalignment range under fixed frequency control.