Wireless power transfer system based on LCC/LCL-S variable structure with constant output power

Abstract

In magnetic coupling wireless power transfer system, the relative position of power transfer coils may change during the operating condition. In order to solve the mutual inductance variation caused by the movement of coils, increase the anti-offset capability of the system to achieve constant power output, a variable structure is proposed in this article. Build the mathematic models of LCC-S and LCL-S structures and analyze the expressions of output power and efficiency in two structures. Design the switching condition, the relationship between coupling coefficient at switching point and parameter setting of capacitor array is obtained with the same input voltage and constant output power. The coupling coefficient range is estimated by output open circuit voltage with a small-voltage input, and the controlling strategy is put forward. Analyze the efficiency of variable structure and build the loss model. It is proved that the switching and input harmonic loss can be reduced by using LCC/LCL-S structure, while the transfer efficiency can be improved through the structure switching between two structures. The simulation results show that the variable structure can effectively reduce the variation range of input voltage and decrease the total harmonic distortion (THD) of input voltage by 46.6%, and keep THD of input current small in a wide range of coupling coefficient.

Keywords

• Variable structure
• LCC-S
• LCL-S
• Constant output power
• Anti-offset
• Loss model