A Novel Control Method for Single-Phase 25kV Solid-State Transformer for High-speed Railway Vehicle

This paper proposes a novel control method for the 4.2 MW single-phase Solid-State Transformer (SST). The purpose of the SST is to regulate the 25kV AC voltage to 3kV DC voltage for the inverter of the traction motor in a high-speed railway vehicle. The SST consists of many converters so that these converters have the form of Input-Series-Output-Series (ISOS) to configure a subsystem called a module. The several modules are connected as Input-Series-Output-Parallel (ISOP), and it configures the SST system. To control the ISOS and ISOP systems, a novel control method is proposed in this paper. Based on the energy control concept, all the capacitors in SST can be easily controlled. In addition, the energy balancing control method for the ISOS system is proposed. The proposed method is confirmed in a simulation and experimental results in a lab-scale prototype.