STATCOM Evaluation in Electrified Railway Using V/V and Scott Power Transformers

Abstract

Rail transport has always been one of the greatest economic boosters of several world nations, allowing the freight and passenger transport. In addition, it is the most secure and economic land transportation mode. From the energetic perspective, the electric locomotives emerge as one of the most efficient land transportation mode, as well as allow a more sustainable development. However, when an electric locomotive is connected to the three-phase power grid, power quality (PQ) deterioration arise, leading to the distortion and unbalance of the three-phase power grid currents and voltages which imply higher operational costs, raising economic and functional issues. In order to overcome the PQ deterioration phenomena, several solutions based power electronics technology have been studied and developed. These solutions vary in terms of control, functionality, implementation costs and complexity. One of the existing solutions is a static synchronous compensator (STATCOM), which compensates the three-phase currents imbalance and harmonics. In this paper, a comprehensive review of the electrified railway systems is carried out, identifying the electric PQ phenomena which may appear due to the non-linear dynamic traction loads. Following this topic, a computational simulation of the STATCOM is presented, making analysis of its behavior regarding the PQ improvement in electrified railway systems. Two case studies are presented: (i) a traction power system fed with V/V power transformer; (ii) a traction power system fed with Scott power transformer.

Evaluation of Static Synchronous Compensator and Rail Power Conditioner in Electrified Railway Systems Using V/V and Scott Power Transformers

“…Some phenomena associated with this system are identified in [7], [8]. In [11] are presented examples of harmonic components in a three-phase 220 kV electrical power grid, as well as presented a performance evaluation of a Static Synchronous Compensator (STATCOM) in these operation conditions.…”

Topologies and Operation Modes of Rail Power Conditioners in AC Traction Grids: Review and Comprehensive Comparison

“…Despite the complex structure of the Scott power transformers when compared to the V/V power transformers, Scott power transformers have several advantages regarding the power quality improvement capability [59]. For instance, when the traction feeders are equally loaded, no active power shifting and no reactive power for NSC compensation are applied by the RPC.…”

“…This imbalance does not appear when using the V/V power transformer, as shown in Figure 21a (B), since it has common windings end points on the primary and the secondary sides. Scott power transformer shows a better power quality improvement capability than the V/V power transformer, even when both traction feeders are unequally loaded (traction feeder x is loaded with 4.8 MW and traction feeder y is loaded with 2.4 MW), as shown in Figure 20b [59]. In this case, the NSC of currents at the fundamental frequency of 50 Hz when using the Scott power transformer was lower than the NSC when using the V/V power transformer.…”

A Review on Power Electronics Technologies for Electric Mobility

“…That is, except by the negligible STATCOM internal power losses, STATCOM will not consume or provide active power to the three-phase ac power grid, and its main objective is solely to exchange reactive power with the three-phase ac power grid in order to improve power quality. Consequently, the STATCOM exchanges the instantaneous reactive power among the phases of the three-phase ac power grid, thus acting as a source of reactive power [262]. Another possibility is to consider a power converter connected to the single-phase traction power system (TPS), where the rail power conditioner (RPC) is used for the purpose of power quality improvement in the ac electrified railways.…”