Analysis and Design of Load-Independent, Efficient, Transformerless Multilevel Online Inductive Power Transfer System

A new transformerless multilevel inductive power transfer (IPT) system was proposed in 2022. It consisted of a multilevel converter, multiple excitation coils, and impedance-matching networks instead of high-frequency transformers. The prior work was limited in introducing the new IPT system and the design methodology for a transformerless IPT system has not been investigated yet. In this study, a new design methodology for transformerless multilevel IPT systems is proposed. The properties and design considerations for the system are identified in the initial stage. It is shown that the harmonic current, parameter-sensitive input impedance, load-dependent output voltage, and efficiency are the main issues of the system. The new design method determines the circuit parameters regarding those main issues and their tradeoffs. The viability of this design methodology was evaluated using simulation results of a medium-voltage input (22.9 kV
_rms
), 1-MW, 42-level online IPT system. In addition, an experimental test bed of 800-W, 4-level IPT system was constructed for the evaluation. The simulation and experimental results showed a good agreement with the theoretical results as well.