Auxiliary Power Supply for Medium-/High-Voltage and High-Power Solid-State Transformers

This article proposes a new auxiliary power supply (APS), which is used to feed the controllers, drivers, and sensors of the submodules for medium-/high-voltage and high-power solid-state transformer. In medium-/high-voltage and high-power applications, the APS is usually connected to the dc bus of the submodule to obtain electric energy. The voltage of the submodule's dc bus is often as high as several thousand volts so that the APS must have the ability to handle such high input voltage. An input-series capacitor structure, which makes the voltage stress of the power semiconductor devices reduced, is adopted in the proposed APS. Therefore, the high input voltage can be handled by the low-voltage power semiconductor devices. Furthermore, the input voltage sharing can be achieved without any special control strategy, which makes the control system simplified and the stability improved. Meanwhile, zero-current switching is guaranteed for all the switches, so that the power density and efficiency can be improved. Finally, the simulation model and prototype are built, by which the feasibility and effectiveness of the proposed APS are verified.