Detuning mechanism and frequency tracking algorithm for wireless power transmission system

Wireless power transmission (WPT) uses a loosely coupled transformer to transmit electric energy. The resulting system's transmission efficiency and distance are affected by factors such as, inductance parameter and resonance frequency offset. To reduce the influence of detuning on transmission efficiency, a frequency tracking method based on the hill-climbing algorithm was proposed in this study. The WPT model was established to depict the detuning mechanism and the transmission efficiency affected by natural frequency changes in the primary and secondary coils. Experimental data were used to prove the correctness of the theoretical analysis. Results demonstrate that the coupling coefficient of the two coils is proportional to the increase of the distance between the transmitting and receiving coils. Hence, coupling coefficient influences transmission efficiency. Another important factor is distance S, as its increase leads to mutual loss, which breaks the previous state of the best resonance compensation, which in turn reduces the transmission efficiency of WPT. When distance S increases from 10 mm to 30 mm and the system has no frequency tracking, the transmission efficiency decreases from 45% to 7.5%. However, when distance S increases from 10 mm to 30 mm and the system has frequency tracking, the transmission efficiency decreases from 70% to 19.1%. When distance S is equidistant, the transmission efficiency is much higher with than without frequency tracking. The proposed method can effectively raise the transmission efficiency of the WPT system and control the cost of hardware, which optimizes practical engineering design. © 2017 Eastern Macedonia and Thrace Institute of Technology.