Wireless power transfer system for gate power supplies of modular multilevel converters

There has been a trend of applying IGBTs to high voltage direct current (HVDC) transmissions and static compensators (STATCOMs). Thus, modular multilevel converter (MMC) is attracting attention because it can satisfy high withstand voltage and large capacity. In MMC, gate power which is required for gate drive circuit tends to be supplied from the main circuit. This method, however, has a problem that the main circuit is unable to supply power to gate drive circuits during a power outage. This paper proposes that the system for the gate power supplies of MMC using wireless power transfer (WPT). 30 kV class MMC whose arm is composed of eight cells is assumed in this study. The proposed system consists of eight primary coils in series, eight secondary coils each cells and capacitors that compensate leakage inductance. About the proposed system, the design of the circuit and computer simulations were carried out. The comparison of compensation capacitors configuration and finite element method (FEM) analysis were conducted in the design. The simulations imitate a load failure and startup in the proposed system. As the results, it is shown that the proposed system has high efficiency which exceeds 80%. The compensation method that is a series connected in the primary side and a parallel connected in secondary side (Series-Parallel configuration) is suitable for proposed system.