Proposal of Series-Parallel Continuously Regulated Chopper Suitable for Auxiliary Power Supply of Railway Vehicle

SUMMARY The conventional auxiliary power supply (APS) of a railway vehicle is directly connected to the catenary through the LC filter. Hence, the switching devices of the APS must have a high breakdown voltage to account for catenary voltage fluctuation. On the other hand, low-voltage switching devices have better characteristics that are desirable for low-loss and high-frequency operation. Therefore, a step-down converter is incorporated between the LC filter and inverter to adapt to catenary voltage fluctuations when using low-voltage switching devices. This paper proposes the series-parallel continuously regulated chopper as a novel step-down converter. First, the fundamental operation characteristics and output voltage control method of the proposed chopper are introduced. The simulation and experimental results for the fundamental characteristics are then described; the simulation and experimental values were almost the same as the theoretical values. The proposed chopper controls the output voltage at the expected value without dramatic fluctuation regardless of the input voltage fluctuation. In addition, a resonance damping control for a constant power load is proposed. The operational characteristics were considered under different potential distributions or load conditions.