Adaptive Impedance Converters in Co-phase Railway Traction Supply System

This chapter presents the application of adaptive impedance converters for co-phase railway supply. The electrical locomotives are treated as single-phase nonlinear loads, which can cause a low power factor, high content of harmonic currents, and negative-sequence currents. Power quality conditioners are widely used to solve power quality issues in the railway power system. In power quality conditioners, the coupled impedance can affect the operation voltage, compensation range, and performance. Therefore, this section discusses the effect of different coupled impedances in conditioners, including fixed inductive impedance, fixed capacitive impedance, and adaptive impedance. Moreover, an adaptive impedance-coupled hybrid power quality conditioner (AI-HPQC) is proposed in comparison with an inductive-coupled railway power quality compensator (RPC) and capacitive-coupled hybrid power quality conditioner (HPQC). Furthermore, a control method for the AI-HPQC is proposed for the coordination control of the adaptive impedance part and the active inverter part. The validities of the RPC, HPQC, and the proposed AI-HPQC are verified by both simulation and experimental results.