Investigation of PT-Symmetric Frequency and Compensation for IPT Coupling-Independent CC/CV and Efficiency in Wide Load Range

It is well known that inductive power transfer (IPT) systems are hard to rival cables due to the significant leakage magnetic flux of loosely coupled transformers. To deliver power efficiently over a wide distance, the coupling-independent constant current/voltage (CC/CV) output and efficiency are desired at any power level. By means of parity-time (PT)-symmetric principle and proper compensation, it is known that series-series (SS)-based IPT system operating at the PT-symmetric frequencies can realize the coupling-independent CC/CV and efficiency, but within a narrow range of load. If the load range becomes larger, the PT-symmetric frequencies and the corresponding coupling-independent characteristics cannot exist, which limits the application. To expand the load range in many applications, this article systematically investigates the PT-symmetric frequencies in the parallel-parallel (PP)-based IPT converter, and then derives the output characteristics and available load area for PT-symmetric frequencies. Furthermore, a fair comparison is carried out among PT-symmetric frequencies in SS and PP compensation, and the other resonance frequencies with coupling-independent output, where it reveals that PT-symmetric frequencies in PP compensation can realize the abovementioned objectives in a wide load range as well as input zero-phase angle to reduce the volt-ampere ratings of components. Finally, a PP-based IPT converter working at PT-symmetric frequencies is implemented to verify the abovementioned performances.