System for converting the DC traction substations into active substations

Abstract

This paper is concerned with the possibilities of transformation the DC traction substations with uncontrolled rectifiers into active substation, being able to ensure both the braking energy recovery and active filtering function. There are a lot of approaches on the management of regenerative braking energy, most of them based on energy storage systems or the concept of reversible substation. Few references refer to the addition of complementary functions, such as harmonic filtering, and involve the adoption of specific structures without further argumentation. In this paper, the intention is to analyze and find argumentations on the possibilities of coupling a three-phase active power filter based on voltage source inverter topology in the power structure of a DC traction substation. The most used types of uncontrolled rectifiers, i.e. the three-phase bridge scheme and both 12-pulse parallel and series structures are taken into consideration. Based on correlation between the DCline and AC-line voltages, it is shown that the active power filter can be connected directly in the secondary of the existing traction transformer only in the case of 12-pulse series rectifier. A dedicated recovery transformer is required for the other two schemes of rectifiers and some considerations and results on the compensating power and correlation between the active filtering performance and the voltage in the recovery transformer primary are presented.

A Review of the Energy Efficiency Improvement in DC Railway Systems

“…Regarding how to connect the inverter to the existing system, in order to ensure good performance in both traction and regeneration regimes, a proper correlation between the inverter voltage at the DC-side and the AC voltage in the point of common coupling (PCC) must be ensured [94]. To illustrate the capability of scheme to allow the regeneration and compensation through the connection of the PWM inverter in the transformer secondary, the ratio k p of the rated DC voltage (U DCN ), and the magnitude of the line-to-line voltage in the transformer secondary is expressed as [94]:…”

“…In setting-up the structure of SISFREG ( Figure 5), which is intended to be added to an existing DC-traction substation with six-or twelve-pulse series/parallel diode rectifier in order to be transformed into a reversible substation with compensation capabilities, it was assumed that a VSI-based SAPF is the basic component, provided it is properly designed and connected. The intrinsic SAPF's capability of providing an increased voltage on its DC-side ensures the correct operation of the system in terms of the quality of the injected current [94,103]. The possibilities of connecting SISFREG to the power supply on the AC-side are illustrated, supported by a theoretical grounding [94].…”

Establishment and Analysis of Energy Consumption Model of Heavy-Haul Train on Large Long Slope

“…If the feedback power cannot be used by other loads in the same traction substation, or the braking power exceeds the power required by other loads, the excess energy flows to the public power grid [6][7][8]. However, feedback into power networks can cause harmonic pollution and reduce the power quality [9,10].…”

“…To avoid braking energy feedback to the public power grid, the current technical solutions are: energy storage [7,[10][11][12], inverter feedback [10][11][12], and inverter load [12]. Because coal-laden trains are heavy-haul trains, which are powerful and have a long running time, regenerative braking energy needs to be recovered by energy storage devices with high energy density and large volume.…”

Application of a High-Power Reversible Converter in a Hybrid Traction Power Supply System

“…It is a good energy-saving method to invert the regenerative braking energy to the AC grid, which has been already applied in several subway lines [16][17][18][19][20][21]. However, it requires additional installation…”