Constant Output Wireless Power Transfer System via Variable Inductance and Synchronous Control Under High Misalignment

The input and output characteristics, such as input zero phase angle (ZPA) and constant output, of the wireless power transfer (WPT) system are easily affected by coil misalignment and variable load. To solve this issue, the coupled mode model of the compensation network part is established to reveal the operation mechanism first, and then, the inverter part is taken as an adjustable negative resistor by following the inherent frequency characteristics of whole circuits. Meanwhile, the negative resistor can be regulated by adjusting the secondary loop impedance to control the system output. Based on the coupling mode theory, a WPT system using a variable inductance (VI) structure is proposed in this article. Without wireless communication and any parameter identification, a primary synchronous control guarantees the ZPA realization under parameters detuning. In addition, secondary VI and the corresponding control strategy enable the whole system to obtain an ideal output. Finally, a 72-V experimental prototype is built to verify the feasibility of the proposed system. Experimental results show that stable output and high transmission efficiency can be maintained within wide load variation and coil misalignment ranges.