Active power conditioner based on a voltage source converter for harmonics and negative sequence components compensation in electrified railway systems

Abstract

The electrification of railway systems has always presented major challenges to the public electrical power systems. Electric locomotives are usually supplied by a single phase AC catenary, causing unbalance and the appearance of negative sequence components (NSCs) in the three phase electrical power grids. In addition, the traction power system of the electric locomotive is usually comprised by uncontrolled rectifiers to convert AC voltage to DC voltage, which produces high levels of current harmonics. Consequently, the operation of electric locomotives causes serious power quality problems to the public electrical power systems. This paper evaluates the use of Shunt Active Power Conditioners (SAPCs) to compensate power quality problems in single phase 25 kV, 50 Hz railway traction substations, when using the conventional V/V or the Scott traction power transformer between the catenary and the public electrical power systems.