Power Electronic Autotransformer Based 3×25 kV Network for Power Quality Enhancement In Railway Supply Systems

State of the art single-phase AC traction systems are based on a split-phase 2×25kV supply network with multiple regularly spaced auto-transformers. The main drawbacks of this arrangement are the unbalanced currents in the three-phase grid and reactive power flow due to transformers and auto-transformers. This paper proposes to solve these issues with a completely new 3×25 kV railway power supply supported by a power electronic autotransformer (PEAT). The PEAT circuit comprises of single-phase back-to-back voltage source converters, connected across different phase pairs of the three-phase network. These voltage-source converters balance the three-phase grid current for all traction load conditions, ensuring grid compliant power quality performance. Over and above that, the PEAT system enables reactive power control and ensure unity power factor at the point of connection. Besides detailing the control algorithm for the PEAT system, this paper also discusses various design aspects and optimal positioning of the PEAT unit along the railway line. The efficacy of the PEAT topology is illustrated through extensive simulations carried out in Matlab/Simulink environment. These are further validated via real time hardware-in-the-loop (HIL) results obtained from a Typhoon HIL 404 device together with a C2000 microcontroller based interface card

Metro Trains Equipped Onboard withSupercapacitors: a Control Technique forEnergy Saving

The paper deals with the use of onboard supercapacitors for metro trains. The practical utilization of supercapacitors requires suitable power converters for the regulation of power flows between the catenary and the electrical drives of the power-train. These converters operate in dc current and have to be bi-directional in order to allow the charge and discharge of supercapacitors. The mathematical model of the whole electrical drive has been developed and the main features of the control strategy have been presented. The control is capable of limiting the peak currents of the contact line and recovering partially the kinetic energy of the train during the braking periods. Simulations prove that the suggested control strategy is very effective for both purposes. Experimental tests made on a scaled prototype, representing the translating masses of a train, fully confirm the results of the simulations