Analysis and Comparison of Modular Railway Power Conditioner for High-Speed Railway Traction System

With the rapid development of modern electrified railway, negative-sequence current minimization is one of the most important considerations in the high-speed railway traction system. In the past, many multiple or multilevel topologies with high compensation capacity have been introduced for railway power conditioner (RPC). This paper presents a simplified quantitative comparison of five previous modular RPC topologies for negative sequence compensation in V/V and SCOTT traction systems, aiming for an optimal selection of the compensators. Performance criteria such as transformer requirement, voltage stress and current stress of a power switch, numbers of the power switches and capacitor are derived by analytical methods. Moreover, the numerical comparison of operating controllers is completed for modular RPCs. In addition, power losses of five modular RPCs are obtained by theoretical analysis, IPOSIM calculation as well as PSIM simulation. These calculations are validated via simulations results in PSIM. The main conclusion is that presented modular RPCs can be divided into general purpose RPC and special purpose RPC in terms of the behavior and efficiency. It is helpful to choose the appropriate topology for specific applications.

I. Introduction

Nowadays, the high-speed electrified railway for mass transportation with reliability and safety is in demand in many countries. Advanced power-electronic technologies [1] –[7], such as pulse-width-modulated (PWM) control and full controlled devices, have partly mitigated the power quality in the traditional traction systems, like harmonic, reactive power, etc. However, negative-sequence current (NSC) caused by the inherited single-phase power traction is increased due to the enhancive load power and the increasing trains [8] [9]. Existence of system unbalance can threaten system stability and may damage vital devices or even cause system failure, resulting in massive economic losses. Hence, proper compensation for traction power supply has become a great concern [10] –[16].