Anti-Offset Parity-Time Symmetric Wireless Power Transfer System With Multiple Transmitting Coils

Parity-Time (PT) symmetric wireless power transfer (WPT) systems offer potential for mobile desktop charging applications due to their ability to maintain constant output power and transfer efficiency even when the receiver is misaligned. However, the anti-offset range of PT-WPT systems is still limited, and further optimization is required. To this end, this paper proposes a PT-WPT system comprising multiple transmitting coils. A reduced-order circuit model of the proposed system has been developed for analysis. Compared to the conventional PT-WPT system with single transmitting coil, the proposed structure significantly reduces the critical coupling coefficient, extends the constant power transfer range, and achieves higher output power and transfer efficiency. Additionally, the two extra degrees of freedom (the number of transmitting coils and the coupling coefficient between them) enable the system's output to be flexibly adjusted to meet the charging requirements of different products. Crucially, all transmitting coils are driven by a single inverter, eliminating the need for additional switches, thereby ensuring simplified system control and cost-effectiveness. Experimental results from a triple-transmitting-coil PT-WPT prototype demonstrate that under the same conditions as a single-transmitting-coil PT-WPT system, the proposed system increases output power by 58.33%, improves transfer efficiency by 1.6%, and extends transfer distance by 21.5%. These results confirm its ability to realize robust and efficient power transfer over a wide range.