Three-Stage Scalable Multimodule Parallel Wireless Power Transfer System With High-Distance-Diameter Ratio in Low-Voltage Applications

In low-voltage, high-current, and high-distance-diameter (d-D)-ratio applications, the magnetically coupled resonant wireless power transfer (MCR WPT) has been confronted with some new challenges, including low coupling coefficient between transmission coils, high-voltage/current stresses on resonant components, large conduction loss of the coil branch, and power switches, which further deteriorate the system efficiency and reliability. In view of above issues, a novel three-stage scalable multimodule parallel MCR WPT architecture is proposed in this article, which includes the input stage, the coil stage, and the output stage, and the specific circuit topology of each power stage is determined subsequently. The transfer characteristics are analyzed by the model of a multimodule parallel system with two sub-modules using the fundamental harmonic approximation (FHA) method. Meanwhile, three different output-stage circuits and the corresponding control schemes are compared to optimize the system performance. Furthermore, a system parameter design guideline is presented from the aspects of high coupling coefficient, low-voltage/current stress on resonant components, and wide-range soft-switching realization. Finally, a 1 kW prototype with the d-D ratio of 1 (3030 cm) is built and the experiments on three different output-stage topologies are carried out and compared, and the optimal system efficiency is 85.2%.