Three-Dimensional Free-Positioning Wireless Power Transfer via Multiple-Current Amplitude Modulation

Free-positioning is one of the challenges for different wireless power transfer applications, from consumer electronics to industrial electronics. Misalignment leads to weak magnetic coupling and reduces the output capacity. However, much research focuses on the misalignment of the two-dimensional plane; once the transmission distance changes, the anti-misalignment capability will be weakened, and the coupler structure needs to be redesigned. This paper introduces a novel multi-current modulation method implemented on a three-layer concentric transmitter, which ensures uniform magnetic fields at varying transmission distances by modulating the current to achieve three-dimensional free-positioning. A surrogate-assisted multi-fidelity genetic algorithm is proposed to obtain the suitable coupler structure and the current amplitude for various transmission distances. A fitness function with a scoring mechanism is adopted to evaluate the uniformity of the magnetic field, which is convenient for the optimization process. Experiments are implemented to verify the anti-misalignment performance at various transmission distances. The results show that the proposed scheme exhibits 25%, 25%, and 15.6% anti-misalignment capabilities in the x, y, and z directions, respectively, and can limit the voltage fluctuation within 5.51%.