Development of a Medium-Voltage Transformerless Multilevel Inductive Power Transfer System

A transformerless multilevel inductive power transfer (IPT) system converts medium-voltage (MV, 6.6 ~ 25 kV) by employing a multilevel converter and excitation coils. To deliver outputs of N number of inverters with MV-level isolation, N:1 coupled excitation coils and a transmitter coil are investigated. The transmitter coil augments magnetic fields generated by the multiple excitation coils. Then, receiver coils can collect power from the transmitter coil via inductive couplings. Applications of the proposed IPT system are MV online IPT systems for trains and large-scale wireless charging stations for electric vehicles. This paper addresses key technical challenges in realizing the MV transformerless multilevel IPT system, such as the multilevel converter, its controllers, and the resonant tank design. In addition, the MV isolation strategy of the excitation coil and the impact of the reinforced concrete on the IPT system are discussed. For evaluation, a 6-level IPT system was fabricated in the PLECS simulation tool. The multi-load charging capacity of the proposed IPT system was evaluated as well.