Hybrid compensation method for traction power quality compensators in electrified railway power supply system

In order to improve the Power Quality (PQ) of traction power supply system and reduce the power rating and operation cost of compensator, a Static VAR Compensator (SVC) integrated Railway Power Conditioner (RPC) is presented in this paper. RPC is a widely used device in the AC electrified railway systems to enhance the PQ indices of the main network. The next generation of this equipment is Active Power Quality Compensator (APQC). The major concern of these compensators is their high kVA rating. In this paper, a hybrid technique is proposed to solve aforementioned problems. A combination of SVC as an auxiliary device is employed together with the main compensators, i.e., RPC and APQC that leads on to the reduction of power rating of the main compensators. The use of proposed scheme will cause to reduce significantly the initial investment cost of compensation system. The main compensators are only utilized to balance active powers of two adjacent feeder sections and suppress harmonic currents. The SVCs are used to compensate reactive power and suppress the third and fifth harmonic currents. In this paper firstly, the PQ compensation procedure in AC electrified railway is analyzed step by step. Then, the control strategies for SVC and the main compensators are presented. Finally, a simulation is fulfilled using Matlab/Simulink software to verify the effectiveness and validity of the proposed scheme and compensation strategy and also demonstrate that this technique could compensate all PQ problems