Energy Management Systems for Smart Electric Railway Networks: A Methodological Review

Energy shortage is one of the major concerns in today’s world. As a consumer of electrical energy, the electric railway system (ERS), due to trains, stations, and commercial users, intakes an enormous amount of electricity. Increasing greenhouse gases (GHG) and CO2 emissions, in addition, have drawn the regard of world leaders as among the most dangerous threats at present; based on research in this field, the transportation sector contributes significantly to this pollution. Railway Energy Management Systems (REMS) are a modern green solution that not only tackle these problems but also, by implementing REMS, electricity can be sold to the grid market. Researchers have been trying to reduce the daily operational costs of smart railway stations, mitigating power quality issues, considering the traction uncertainties and stochastic behavior of Renewable Energy Resources (RERs) and Energy Storage Systems (ESSs), which has a significant impact on total operational cost. In this context, the first main objective of this article is to take a comprehensive review of the literature on REMS and examine closely all the works that have been carried out in this area, and also the REMS architecture and configurations are clarified as well. The secondary objective of this article is to analyze both traditional and modern methods utilized in REMS and conduct a thorough comparison of them. In order to provide a comprehensive analysis in this field, over 120 publications have been compiled, listed, and categorized. The study highlights the potential of leveraging RERs for cost reduction and sustainability. Evaluating factors including speed, simplicity, efficiency, accuracy, and ability to handle stochastic behavior and constraints, the strengths and limitations of each optimization method are elucidated

Hybrid Energy Storage System Taking Advantage of Electric Vehicle Batteries for Recovering Regenerative Braking Energy in Railway Station

Nowadays, nations are moving toward the electrification of the transportation section, and the widespread development of EV charging stations and their infrastructures supplied by the grid would strain the power grid and lead to overload issues in the network. To address this challenge, this paper presents a method for utilizing the braking energy of trains in railway stations to charge EVs located in strategic areas like park-and-ride regions close to railway stations improving energy efficiency and preventing grid overload. To validate the feasibility of the proposed system, a metro substation in Milan city is considered as a case study located in outskirts of the city and contains large number of parking space for vehicles. Three different scenarios are evaluated including DC fast charging station, AC low charging station and collaborative hybrid energy storage based AC charging station as EV charging station type. The results are studied for different EV population number, charging rate and the contractual power grid. Meanwhile, the possibility of proposed system in participating as V2G technology and taking advantage of the EV’s batteries to provide ancillary support to accelerating trains is investigated regarding peak shaving objective. The results indicated that the suggested interconnected system operates effectively when a significant quantity of EVs are parked at the station. However, the results revealed that the performance of the proposed system is notably influenced by other factors and a limited number of EVs during the early morning and late evening periods. Overall, this study confirms the feasibility of energy transfer between two types of transportation means in intermodal areas

Applications of Genetic Algorithm and Its Variants in Rail Vehicle Systems: A Bibliometric Analysis and Comprehensive Review

Railway systems are time-varying and complex systems with nonlinear behaviors that require effective optimization techniques to achieve optimal performance. Evolutionary algorithms methods have emerged as a popular optimization technique in recent years due to their ability to handle complex, multi-objective issues of such systems. In this context, genetic algorithm (GA) as one of the powerful optimization techniques has been extensively used in the railway sector, and applied to various problems such as scheduling, routing, forecasting, design, maintenance, and allocation. This paper presents a review of the applications of GAs and their variants in the railway domain together with bibliometric analysis. The paper covers highly cited and recent studies that have employed GAs in the railway sector and discuss the challenges and opportunities of using GAs in railway optimization problems. Meanwhile, the most popular hybrid GAs as the combination of GA and other evolutionary algorithms methods such as particle swarm optimization (PSO), ant colony optimization (ACO), neural network (NN), fuzzy-logic control, etc with their dedicated application in the railway domain are discussed too. More than 250 publications are listed and classified to provide a comprehensive analysis and road map for experts and researchers in the field helping them to identify research gaps and opportunities

A comprehensive control strategy of railway power quality compensator for AC traction power supply systems

The development of electrical railway systems leads to critical power quality problems in the power grid. This paper discusses a kind of half-bridge-based railway power quality compensator system (HBRPQC) that can compensate negative sequence currents, harmonics, and reactive power simultaneously. In order to keep the HBRPQC performance efficient for the different kinds of transformers used in traction power supply substations, a new multifunctional control strategy that performs better than previous methods is proposed. Due to the fast dynamicity of traction loads, a recessive self-Tuning PI controller based on fuzzy logic is adopted in the current control system. The output control variables are integrated with carrier-based pulse width modulation techniques to generate the pulse signals of HBRPQC switches. The performance of the proposed control strategy is verified for V/V, Yd11, and Scott transformers by simulation and the results prove the effectiveness of the strategy

Compatibility of Present 3 kV DC and 2×25 kV AC High-Speed Railway Power Supply Systems towards Future MVDC System

In recent years, due to the limitations and disadvantages of conventional DC and AC railway power supply systems (RPSS) the idea of reinforcing and replacing these systems with a more advanced and developed MVDC based system has become more prominent. The high power capability of these alternative systems together with convenient integration of distributed energy resources are the outstanding features which highlight their potential. In this paper, the adaptability of current Italian high-speed RPSS including 3 kV DC and 2×25 kV AC with new MVDC RPSS in terms of the configuration of traction power substations (TPSS), OCS structures, voltage drops, and rolling stocks has been addressed and interface power electronic-based converters are suggested

The Evolution of Railway Power Supply Systems Toward Smart Microgrids: The concept of the energy hub and integration of distributed energy resources

In recent years, the achievement of sustainable energy systems has become one of the foremost challenges of experts around the world. In this context, the reduction of energy consumption while providing optimum power flow to the end users is a substantial challenge in various fields of generation, transmission, and distribution. Environmental concerns like global greenhouse gas emissions and other problems related to fossil fuels, together with deficiency of resources, are other significant aspects

Power Quality Phenomena in Electric Railway Power Supply Systems: An Exhaustive Framework and Classification

Electric railway power systems (ERPS) as one of the most critical and high-power end-user loads of utility grids are characterized by outlandish power quality (PQ) problems all over the world. The extension and evolution of different supply topologies for these systems has resulted in significant and various forms of distortions in network voltage and current in all ERPS, the connected power system, and adjacent consumers. During the last years, numerous studies have been offered to investigate various aspects of PQs in a specific supplying topology. Variation in the supply structure of the ERPS and different types of locomotives has propelled the observation of different PQ phenomena. This versatility and development have led to confront considerable types of two-way interactive interfaces as well as reliability and PQ problems in ERPS. In addition, the lack of standards explicitly dedicated to ERPS has added to the ambiguity and complexity of this issue. In this paper, an extensive review of PQ distortions and phenomena in different configurations of ERPS is proposed and a systematic classification is presented. More than 140 scientific papers and publications are studied and categorized which can provide a fast review and a perfect perspective on the status of PQ indexes for researchers and experts

Reversible Traction Substations in DC Railway Systems: A Comparative Study of Approaches

In line with the overall goals of EU climate commitment and railway operators, reducing CO2 emission and eco-friendly transport systems together with increased energy efficiency have received more attention during the last years. In this context, a significant contribution of studies is dedicated to the capabilities and potentials of utilizing regenerative braking energy (RBE). Among different methods of recuperating RBE, adopting reversible/bidirectional substations to feed back the RBE into the upstream grid is a promising solution. In this paper, different methods and configurations regarding the implementation of reversible substations (RSS) with bidirectional power flow capability are discussed and compared. Meanwhile, the challenges of transforming the existing traditional traction substations (TSS) into reversible substations together with their impacts on the energy efficiency of the electric railway system (ERS) are outline