Energy-Storage-Based Smart Electrical Infrastructure and Regenerative Braking Energy Management in AC-Fed Railways with Neutral Zones

Abstract

This paper presents a modified power supply system based on the current alternating current (AC)-fed railways with neutral zones that can further improve the eco-friendliness and smart level of railways. The modified system complements the existing infrastructure with additional energy-storage-based smart electrical infrastructure. This infrastructure comprises power electronic devices with energy storage system connected in parallel to both sides of each neutral zone in the traction substations, power electronic devices connected in parallel to both sides of each neutral zone in section posts, and an energy management system. The description and functions of such a modified system are outlined in this paper. The system allows for the centralized-and distributed-control of different functions via an energy management system. In addition, a control algorithm is proposed, based on the modified system for regenerative braking energy utilization. This would ensure that all the regenerative braking energy in the whole railway electrical system is used more efficiently. Finally, a modified power supply system with eight power supply sections is considered to be a case study; furthermore, the advantages of the proposed system and the effectiveness of the proposed control algorithm are verified.The installation of equipment that provide clean energy from renewable sources (e.g., solar panels and wind generators) to feed the traction loads in rail may have a significant impact in the energy costs and CO 2 emissions of a railway system, increasing the environment friendliness of the railway [4][5][6]. The introduction of renewable energy is to partially reduce the depletion of non-renewable energy resources and thus reduce CO 2 emissions. These outcomes have been favored by scholars and many countries, such as North American, European, China, and Japan [6,7]. But in practice, the traction energy consumption of railways has not been reduced.By contrast, the efficient driving and regenerative braking schemes differ the renewable energy scheme. They can essentially reduce the traction energy consumption of railways.Efficient driving is an effective way to reduce the traction energy consumption of rolling stock. Typically, the running state of vehicles comprises three phases: braking, speed-holding (cruising) and acceleration. At present, many literatures have studied the efficient driving and realize the traction energy savings through the optimum combination of these phases [8][9][10][11][12][13]. To implement such trajectories and maximize savings, some auxiliary systems, such as driver advisory systems (DAS) [10,11] and automatic train operation (ATO) [12,13], must be provided to drivers. The trials of such systems have shown savings of 5-18%. However, with efficient driving, the savings of energy consumption may sacrifice service quality, such as the train speed, stopping time, etc. [1].Regenerative braking energy (RBE) recovery is a simple and efficient way to reduce energy consumption, which cannot influence the operati...

Centralized-Decentralized Control for Regenerative Braking Energy Utilization and Power Quality Improvement in Modified AC-Fed Railways

“…Moreover, a large power loss occurs because of the long-distance delivery of RBE. Then, an energy-storage-based smart electrical infrastructure is proposed to solve these problems by installing PTDs and EPTDs in all NZs [36]. This scheme can not only deliver RBE between different power supply sections, but also store surplus RBE.…”

“…At present, the railway smart grid concept is proposed and offers a new perspective for the eco-friendliness of railway systems [37,38]. The scheme in [36] will create more opportunities and controllability for smart railway systems, and have great significance for the construction of smart railway grids.…”

“…However, in the modified railway system in [36], the realization of these functions needs to be controlled in the energy management system (EMS), using bidirectional communication equipment and advanced computational features. If faults occur in the EMS or communication equipment, all functions, including the utilization of RBE, will be unavailable, which would greatly affect the utilization of RBE and the reliability of the modified railway system, even endangering the safe operation of the whole railway system [39].…”

“…With the development of a smart railway system, the centralized-decentralized control will become an inevitable trend for railway energy management systems. The authors in [42] proposed a centralized-decentralized automation architecture for a railway energy management system, but this cannot be directly applied to the modified railway system in [36]. An internal-external method to control three RPCs was proposed in [43], however it was primarily aimed at improving the power quality of the railway and reducing the capacity of RPCs.…”

“…In addition, the internal-external method strongly depends on the state of the central controller and communication equipment. Given that only a centralized control strategy is proposed in [36], it is necessary to introduce a centralized-decentralized control strategy into a modified railway system to improve the reliability and redundancy of the system. The work done in this paper is also the continuation of the research in [36].…”