Assessment of the worthwhileness of efficient driving in railway systems with high-receptivity power supplies

Eco-driving is one of the most important strategies for significantly reducing the energy consumption of railways with low investments. It consists of designing a way of driving a train to fulfil a target running time, consuming the minimum amount of energy. Most eco-driving energy savings come from the substitution of some braking periods with coasting periods. Nowadays, modern trains can use regenerative braking to recover the kinetic energy during deceleration phases. Therefore, if the receptivity of the railway system to regenerate energy is high, a question arises: is it worth designing eco-driving speed profiles? This paper assesses the energy benefits that eco-driving can provide in different scenarios to answer this question. Eco-driving is obtained by means of a multi-objective particle swarm optimization algorithm, combined with a detailed train simulator, to obtain realistic results. Eco-driving speed profiles are compared with a standard driving that performs the same running time. Real data from Spanish high-speed lines have been used to analyze the results in two case studies. Stretches fed by 1 × 25 kV and 2 × 25 kV AC power supply systems have been considered, as they present high receptivity to regenerate energy. Furthermore, the variations of the two most important factors that affect the regenerative energy usage have been studied: train motors efficiency ratio and catenary resistance. Results indicate that the greater the catenary resistance, the more advantageous eco-driving is. Similarly, the lower the motor efficiency, the greater the energy savings provided by efficient driving. Despite the differences observed in energy savings, the main conclusion is that eco-driving always provides significant energy savings, even in the case of the most receptive power supply network. Therefore, this paper has demonstrated that efforts in improving regenerated energy usage must not neglect the role of eco-driving in railway efficiency

Optimal control of hybrid systems and renewable energies

International policies for sustainable development have led to an increase in distributed power production based on renewable resources [...

Power Quality in Electrified Transportation Systems

"Power Quality in Electrified Transportation Systems" has covered interesting horizontal topics over diversified transportation technologies, ranging from railways to electric vehicles and ships. Although the attention is chiefly focused on typical railway issues such as harmonics, resonances and reactive power flow compensation, the integration of electric vehicles plays a significant role. The book is completed by some additional significant contributions, focusing on the interpretation of Power Quality phenomena propagation in railways using the fundamentals of electromagnetic theory and on electric ships in the light of the latest standardization efforts

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

The use of static frequency converter feeder stations and a new control strategy enabling mesh feeding for 50 Hz AC railways

Railways around the globe are rapidly growing as the passenger numbers surge due to the increasing requirements for connectivity and cleaner methods for transport. To accommodate the current and future demand, new and existing lines are being built and updated. Electrification has been identified as key to achieve sustainable railways, yet solutions have remained unchanged for decades. Although efficient, conventional electrification systems are inflexible and limit the application of multi-source power solutions. Static Frequency Converters (SFCs) are an alternative to conventional transformer-based electrification systems which provide a more highly interconnected electrification solution, due to their controllability, which potentially allows increased operational flexibility and robustness. Early static converter deployments for 16.7 Hz supplies the potential for dual-end feeding, however, due to the novelty of the SFC technology and its application to railways, a full mesh-feeding solution has not yet been explored. In this thesis, the author considers the deployment of SFC technologies within the 50 Hz, 25 kV, railway and the application of smart control strategies in deploying the mesh feeding concept. Comparative studies using mathematical models and computational simulations representing the electrification infrastructure and the moving trains have been carried out, in considerable detail, using code written in MATLAB Script. The mathematical modelling of the traction system is based on a lumped parameter modelling approach. These studies show that the application of SFCs requires lower rated feeder stations and provides increased operational flexibility and fault tolerance, while not suffering from the power quality issues associated with conventional transformer-based systems. In optimised deployments, SFC feeder station ratings and transmission losses can be reduced even further. Additionally, it has been shown that the use of a smart control system for mesh feeding increases flexibility in the locations available for efficient deployment of the feeder stations. An economic evaluation has demonstrated that SFCs are financially beneficial over a 50-year lifespan, with the novel control system introduced in this thesis proving beneficial, both economically and technically. As the technology is evolving, it is anticipated that economic and operational benefits will increase, and the flexibility associated with SFC solutions is expected to support advances in wider railway electrification, including the deployment of railway smart grids. A roadmap anticipating the wider technology development is therefore also presented

Opportunities and challenges of power electronics systems in future railway electrification

With the continuous expansion of the railway power systems, the integration of high speed locomotives and the need to increase the overhead catenary line power capacity, the main shortcomings of the conventional railway feeding system are becoming more evident. In order to overcome these drawbacks and to contribute to the technological evolution with innovative and electrically more efficient systems, several solutions have been proposed and implemented. In this context, this paper briefly presents a study of different railway power systems, highlighting emerging concepts, such as regenerative braking, energy storage systems, the inclusion of renewable energy sources, bidirectional power flow and wireless power transfer. Some of these concepts can be implemented in short to medium term, or in the long term. Following these concepts, an overview of the power electronics challenges for the implementation of these emerging concepts is presented and discussed.This work has been supported by FCT –Fundação para a Ciência e Tecnologia within the R&D Units Project Scope: UIDB/00319/2020. This work has been supported by the FCT Project QUALITY4POWER PTDC/EEI-EEE/28813/2017. Mr. Luis A. M. Barros is supported by the doctoral scholarship PD/BD/143006/2018 granted by the Portuguese FCT foundation. Mr. Mohamed Tanta was supported by FCT PhD grant with a reference PD/BD/127815/2016