Metro Railway Systems Research Articles

Quantifying and enhancing the energy resilience of zero-emission train station systems against power outages via electrified train-building integrations

Addressing power outages due to renewable energy penetration and conventional utility grid issues is vital to ensure the reliability and resilience of any energy system. Therefore, this project begins by modelling a renewable energy-supported swappable battery-powered railway system with stochastically driven power outages. Then, it comprehensively quantified energy resilience using novel technological, economic and environmental indicators for different annual power outage percentages and renewable energy capacities. Two implementations are systematically analysed: one that uses a unique control strategy for dynamically handling the power outage periods in addition to the existing control strategy, and another that finds the right renewable energy mix within and between the stations. The first one improves the autonomous net-zero energy system by enhancing the energy-based resilience factor, annual carbon emissions from the system, and net present value for the estimated lifetime of 20 years from 0.83 to 0.99, 264.7 to 12.7 ton and –7.3 × 106 to 51.4 × 106 HKD, respectively. The second investigation reveals that technological and environmental indicators favour solar energy of 70 %, and the economic indicator prefers more wind energy. Using 100 % wind energy on both stations of the metro railway system is economically consistently effective as it provides a net present value of up to 59.8 × 106 HKD owing to the 30 % lower capital cost of wind energy compared to solar energy.

Extending SysML to Integrate Cost Analysis Into Model-Based Systems Engineering

Model-based systems design (MBSD), a current trend adopted by INCOSE, employs the systems modeling language (SysML), a standard introduced by OMG and INCOSE. Though there are numerous works on integrating performance exploitation in SysML, cost is not sufficiently explored as a driving design parameter. By integrating cost analysis in a popular modeling language like SysML, the proposed approach may be applied to any system designed using standardized languages and tools. In this work, we integrate cost analysis within SysML models at a generic level to explore design alternatives under specific cost and performance restrictions and perform tradeoff analysis. The proposed SysML extensions provide: 1) cost-related entities to encode cost aspects, such as capital and operating expenses, and 2) functions that enable the automatic computation of costs; these extensions are contained in a custom SysML cost profile. The feasibility and benefits of the approach are explored in two distinct real-world case studies with different purpose and characteristics. 1) Configuring a remote elderly monitoring system, taking into consideration patients' budgetary and operational concerns regarding the equipment installed in their homes. In this case, patients had the opportunity to evaluate and prioritize their concerns prior to using the system. 2) Exploring the improvement of the passengers' comfort as a level of service indicator in the Athens Metro railway system, taking into account operational cost constraints. In this case, the operator obtained forecasts of performance and cost of the metro system operation in order to choose between different operational policies.

The positive and negative impact of novel utility demand response programme and stochastic utility-driven events on renewable penetration and flexibility activation of train and station systems

Integrating an incentive-driven demand response program (DRP) into a metro railway system can enhance the techno-economic benefits of grid operators and metro railway operators by modulating the grid interactions. To facilitate demand response (DR), all energy flexibility resources within the metro network, such as heating, cooling, electrical, and vehicle systems, should be individually regulated by optimal control strategies. Therefore, an automated energy management system was developed and implemented to prioritise and logically control various energy flexibility resources to maximise the annual performance based on the requirements of the DR signal from the utility grid. Automated DR management helps to achieve an annual DR incentive of 0.57 × 106 HKD, enabling a 2.9 times lower annual operational cost of 0.28 × 106 HKD compared to the reference, even after accounting for the annual electricity tariff of 0.84 × 106 HKD. The techno-economic impacts of becoming a DR participant were stochastically studied using Hong Kong’s DRP by examining all crucial factors in the DR business model. In addition, this study defines a methodology for determining the optimal demand reduction target without biasing any stakeholders. Then, the DR business model was comparatively evaluated between a prosumer-based energy system and the same system without renewable energy support. The former system loses the DR incentive in proportion to the load matching compared to the latter system. Moreover, the DRP was extended from static to dynamic DR support, and the results show that considering dynamic DR can further increase the economic benefit of all stakeholders.

A Hybrid Deep Learning Approach for Real-Time Estimation of Passenger Traffic Flow in Urban Railway Systems

This research introduces a hybrid deep learning approach to perform real-time forecasting of passenger traffic flow for the metro railway system (MRS). By integrating long short-term memory (LSTM) and the graph convolutional network (GCN), a hybrid deep learning neural network named the graph convolutional memory network (GCMN) was constructed and trained for accurate real-time prediction of passenger traffic flow for the MRS. Data collected of the traffic flow in Delhi’s metro rail network system in the period from October 2012 to May 2017 were utilized to demonstrate the effectiveness of the developed model. The results indicate that (1) the developed method provides accurate predictions of the traffic flow with an average coefficient of determination (R2) of 0.920, RMSE of 368.364, and MAE of 549.527, and (2) the GCMN model outperforms state-of-the-art methods, including LSTM and the light gradient boosting machine (LightGBM). This study contributes to the state of practice in proposing a novel framework that provides reliable estimations of passenger traffic flow. The developed model can also be used as a benchmark for planning and upgrading works of the MRS by metro owners and architects.

Leveraging energy flexibilities for enhancing the cost-effectiveness and grid-responsiveness of net-zero-energy metro railway and station systems

The number of metro railway systems is rapidly increasing, and several projects are being implemented to install renewables and convert overhanging power line-based trains into battery-powered trains. This study comprehensively reveals the energy flexibility potential of a net-zero metro railway system. Various energy flexibility strategies, quantification, and crucial trade-offs are explored to reach high levels of techno-enviro-economic and grid-responsive performance. Energy flexibility strategies, such as forced shutdown, forced charging, peak shaving, valley filling, energy shifting, and synergic control, are implemented to accurately reduce the maximum demand power, increase the self-consumption of self-generated renewables, and limit the import of power from the grid. This study systematically proposes a set of energy flexibility solutions for improving the interchangeable battery-powered net-zero metro railway system without modifying the capital cost. It suggests a cost-effective energy flexibility solution for the case in which the restriction in the capital cost is removed. Swappable battery-powered railway systems without (reference-1) and with (reference-2) renewable energy are simulated as reference cases for energy flexibility analysis. The annual operational cost and net present value (NPV) of reference-2 are −0.9 × 106 and 72.4 × 106 HKD, respectively. These values indicate that the net-zero metro railway system is techno-economically feasible. Without changing the capital cost, the energy flexibility measures help to reduce the annual operational cost 10.3 % lesser and NPV 1.89 × 106 HKD greater compared to those of reference-2. When implementing a few more energy flexibility strategies by incorporating a cost-effective energy flexibility source, the annual operational cost, NPV, and annual maximum grid imported power of the net-zero metro railway system were 26.1 % lesser, 3.9 × 106 HKD greater, and 58.3 % less than those of reference-2. Moreover, the strategies proposed in this study are suitable for sector-coupled systems whether the vehicle demand is lower than or equal to or higher than the building demand.

Real Time Control System for Metro Railways Using PLC & SCADA

This paper proposes to adopt SCADA and PLC technology for the improvement of the performance of real time signaling & train control systems in metro railways. The main concern of this paper is to minimize the failure in automated metro railways system operator and integrate the information coming from Operational Control Centre (OCC), traction SCADA system, traction power control, and power supply system. This work presents a simulated prototype of an automated metro train system operator that uses PLC and SCADA for the real time monitoring and control of the metro railway systems. Here, SCADA is used for the visualization of an automated process operation and then the whole operation is regulated with the help of PLC. The PLC used in this process is OMRON (NX1P2-9024DT1) and OMRON’s Sysmac studio programming software is used for developing the ladder logic of PLC. The metro railways system has deployed infrastructure based on SCADA from the power supply system, and each station’s traction power control is connected to the OCC remotely which commands all of the stations and has the highest command priority. An alarm is triggered in the event of an emergency or system congestion. This proposed system overcomes the drawbacks of the current centralized automatic train control (CATC) system. This system provides prominent benefits like augmenting services which may enhance a network’s full load capacity and network flexibility, which help in easy modification in the existing program at any time.

Modeling evaluation for fire resistance design of rail car floor assembly

This paper is prepared to report the engineering practice by a Chinese railcar manufacture in a railcar design process for a Metro system in U.S. The fire resistance of rail car floor systems is considered as one of the important fire protection features on the railcars operated in U.S., which provides fire separation between the equipment installed under the floor and the passengers insider railcar. In this study, a pragmatic approach was developed to numerically evaluate the fire resistance of rail car floor assemblies and provide insights for necessary design modifications. Finite element analysis (FEA) was applied to assess the fire resistance performance of a rail car floor assembly designed for a metro railway system in the U.S. An optimization algorithm was applied to obtain the thermal properties of intumescent coating. FEA analysis results were applied to assist the design modifications so that the floor assembly successfully satisfies the current requirement and passes the ASTM E119 fire resistance test. The FEA modeling details and heat transfer analysis results are presented. It is also shown that the model predictions agree conservatively well with the full-scale fire resistance test data.

Study of Integral Structure behaviour for Rail Structure Interaction in the Proposed Metro Viaduct

Long welded rails (LWR) are preferred in metro rail systems because they provide a smooth ride. They are extremely sturdy, require less maintenance and safe to travel at higher speeds. Rail structure interaction (RSI), especially additional longitudinal stresses in rail, is the major concern in the LWR. UIC standards provide the limitations of additional rail in longitudinal stresses. This paper studies the characteristics of additional forces in long welded rail used in one of the Metro Railway systems in India. The LWR is placed on five spans with integral intermediate piers of balanced cantilever superstructure (BCM). A nonlinear finite element analysis is performed using the analytical tool MIDAS CIVIL 2021 to study the interaction mechanism. For this study, rail and deck (unballasted) are linked with a multilinear elastic spring, as recommended in UIC 774-3R. The study was conducted in accordance with the International Union of Railways and Indian standards. This paper shows a comparison of the rail stresses along the rail due to combined thermal and live loading for both balanced cantilever span and conventional simply supported spans. The results show that rail stresses have significant variation due to bearing articulation, adjacent spans and integral BCM system.

Railway Automation: A framework for authority transfers in a remote environment

Research on mainline railway automation has advanced significantly in recent years regarding the technical and safety challenges linked to the deployment of open-world automated trains. However, similarly to other transport domains, early industrial concerts are mainly focused on fully automated systems that can operate without the help of human operators. As multiple studies tend to prove that such endeavor might be too optimistic in an open-world situation, due to multiple safety concerns, industrials are slowly aiming for more human-centered systems, focusing on cooperation. Different solutions are considered, from on-board shared control to remote driving scenarios. This paper presents the framework used in our research project on human-machine cooperation for authority transfer between an autonomous train and a remote driver, to define appropriate automation levels. The definitions for railway automation usually stem from metro railway systems. While the main ideas can be broadly applied to other railway domains, the definitions must be adapted to the specificities of the studied activity and the place of remote-control operations must be determined. In addition to this framework, this paper will also present the objectives of the project and the choices made regarding use cases with a focus on human factors aspects.

Simulation-based techno-economic feasibility study on sector coupled net-zero/positive energy metro railway system in Hong Kong

Sector coupling between the building and transportation sector can reduce decarbonization costs by boosting the energy system's overall performance, adequacy, flexibility, reliability and economy while leveraging renewable energy. This project recommends that the net-positive energy metro railway system is a large-scale versatile system capable of integrating all proven technologies to resolve many energy-related issues. Low consumption, high-efficiency metro station building and battery-powered metro trains with B2V, G2V, V2B and swappable battery techniques are designed, modelled, parametrically simulated and analyzed with various control strategies to achieve a net-positive energy balance based on various techno-enviro-economic indicators. Six different metro railway systems have been comprehensively developed and comparatively studied to investigate the renewable energy integration and interaction among metro stations, metro trains and the utility grid while achieving optimum load matching and grid interaction. The economic and energy flexibility studies are carried out to quantitatively highlight the potential. When the net-positive energy principle is implemented in a traditional railway system (ref_case-2), the renewable energy output of 1907 MWh meet demand, resulting in annual net positivity of 15.36% with an OEF of 0.8 and OEM of 0.71, and reducing annual carbon emissions into −8.5 kg/m2.a. The economic indicator shows that ref_case-2 and ref_case-3 are feasible only on Hong Kong FiT and not viable on the net-metering-based tariff. Eliminating the investment in electric catenary for the overhanging power line by following a battery-based metro train with B2V, G2V, V2B, and swappable battery technique significantly improves the overall performance and makes the system techno-enviro-economically feasibility on both the tariffs.

Assessment of Noise Pollution of Kolkata Metro Railway System and Its Impact on Urban Receptors A Case Study

An assessment of noise quality was conducted at underground and overground metro stations, within the metro rakes (AC and Non-AC) and at an institutional building near elevated metro corridor to assess the exposure of Kolkata Metro Railway System. The present study was conducted in different hours (peak and non-peak hour) for different types of rake (AC and Non-AC) movement. Different noise descriptors including A-weighted equivalent noise (Leq), statistical noise (L10,L50,L90), noise climate (NC), traffic noise index (TNI), two hour noise dose (%ND) and corresponding time-weighted average (TWA) were calculated under the purview of the present study. Pearson’s correlation was performed between all noise descriptors to investigate the relation between them. Scatter plot analysis was conducted between L10 and %ND. In case of all study duration, all noise descriptors mostly exceeded FTA prescribed noise standard, along with 2-hr TWA which exceeded the OSHA guidelines of 100 dB for both AC and Non-AC rakes. On the other hand, at underground and overground metro stations, within metro rakes (except at day peak hour within AC coach) and at school building, mean value of traffic noise index (TNI) exceeded 74 dB (A), the threshold of over criterion. The study results indicate that Non-AC rakes are more annoying than AC-rakes. In all the study units, Leq was influenced by L10, which originates from pressure honking. There is very strong relationship observed between L10 and % ND. This study proposes that noise barrier should be installed at underground and overground metro stations, along the stretches of overground metro track, within metro rakes for developing the acoustic quality of Kolkata Metro Railway System and the areas of its immediate vicinity.

Digital Twin Aided Sustainability and Vulnerability Audit for Subway Stations

Digital twin (DT) or so-called ‘building information model (BIM)’ has brought great revolution to the current building industry. Its applications to life cycle management of buildings and infrastructures can further increase the social and economic benefits. As a complete information model, a digital twin integrates the information of a project from different stages of the life cycle into a model, in order to facilitate better asset management and communicate through data visualizations with participants. This paper unprecedently introduces a digital-twin aided life cycle assessment to evaluate a subway station. Dadongmen subway station in Hefei was used as a case study. This new study benchmarks the cost estimation and carbon emission at each life cycle stage of the project. The cost in the construction stage of the project is the highest, accounting for 78% of the total cost. However, the amount of carbon emissions in the operation and maintenance is higher than the amount during the production of building materials, accounting for 67%. Among them, concrete only accounts for 43.66% of the carbon emissions of building materials, even though concrete was mainly used for constructing the metro station. Steel bar and aluminum alloy have carbon emissions of 29.73% and 17.64%, respectively. In addition, emerging risks of the subway stations can be identified. The digital twin has been used to illustrate vulnerability and potential solutions to emerging risks, and to assess the suitability through life cycle cost and carbon footprint. This initiative is relatively new to the industry. The new insight into life cycle assessment or LCA (especially carbon footprint over the life cycle) integrated with digital twin applications will enable sustainable development that will enhance resilience of metro railway systems globally.

Optimal Control of Reversible Substations and Wayside Storage Devices for Voltage Stabilization and Energy Savings in Metro Railway Networks

Growing concerns about environmental issues dictate the necessity for improving the energy efficiency and total performance of metro railway systems. Proper management of the regenerative energy is a key element in this direction, and several strategies, such as timetable optimization, use of reversible substations, and installation of storage devices, have been proposed. This paper focuses on the optimal control of reversible substations and wayside storage devices for energy savings and voltage stabilization. The methods proposed for maximizing the recovered energy are presented together with their theoretical analysis. A novel optimization strategy, based on the linearization of the dc power flow equations, is analytically explained, while a successive approximation method is used. The proposed control strategy is evaluated through simulations on a modified version of the Thessaloniki metro railway network (Greece). Simulation results show that the system performance is significantly improved when reversible substations or energy storage are in operation.

Big data driven urban railway planning: Shenzhen metro case study

Planning a successful metro railway system is challenging due to the fast development of urban cities and time-consuming construction. Recently big data reflecting city dynamics has become widely available, which enables us to solve this challenging problem from a data mining perspective. In this paper, we propose a framework to evaluate the traffic efficiency of metro railway systems from various factors such as the railway traffic flow, the structure of the traffic system and the spatial distribution of work-and-home. Based on the commute data (e.g., railway boarding) of Shenzhen rail transit reported by 28,000 passengers and electronic boarding card data provided by Shenzhen Railway Company, we assess the bottlenecks and congested areas of the system, understand passenger travel patterns, and observe organizational operations and deficiencies. The experimental results help us better understand how big data can help make Shenzhen metro railway more efficient and effective in terms of planning and management in the future.

A Sparse Optimization Approach for Energy-Efficient Timetabling in Metro Railway Systems

In this paper, we propose a sparse optimization approach to maximize the utilization of regenerative energy produced by braking trains for energy-efficient timetabling in metro railway systems. By introducing the cardinality function and the square of the Euclidean norm function as the objective function, the resulting sparse optimization model can characterize the utilization of the regenerative energy appropriately. A two-stage alternating direction method of multipliers is designed to efficiently solve the convex relaxation counterpart of the original NP-hard problem and then to produce an energy-efficient timetable of trains. The resulting approach is applied to Beijing Metro Yizhuang Line with different instances of service for case study. Comparison with the existing two-step linear program approach is also conducted which illustrates the effectiveness of our proposed sparse optimization model in terms of the energy saving rate and the efficiency of our numerical optimization algorithm in terms of computational time.

DC정류기를 갖는 도시철도의 최대수요전력 산출 근사모델

이 논문에서는 도시철도의 최대수요전력 산출을 위한 근사모델을 제시한다. 전류 벡터 반복법을 활용하여 변전소의 최대수요전력을 계산할 경우에 기존의 방법으로는 수 많은 반복 조류계산이 필요하기 때문에 계산시간 제약으로 인해 실시간 적용이 어렵다는 문제가 있다. 본 논문에서는 모든 조건이 동일한 상태에서 전원 임피던스의 변화에 따른 변전소 최대수요 전력을 빠르게 산출하는 근사모델을 제시한다. 제시된 근사 모델에 의한 산출결과가 기존 모델과 거의 유사한 정확성을 보임을 시뮬레이션을 통해 예시한다. This paper presents an approximate model for computing the peak demand power in a metro railway system. The peak demand of substations can be calculated using the current vector iteration method. But the existing method requires many repeated calculations to determine the peak demand power, which makes it difficult to apply to the real-time peak power control problem. In this paper, we assume that none of the conditions vary except source impedance and make an approximate model for rapid calculation based on changes in the impedance of the power substation. The proposed model result is approximately the same as the existing model, which is demonstrated through simulation.

Dynamic coast control of train movement with genetic algorithm

The railway service is now the major transportation means in most of the countries around the world. With the increasing population and expanding commercial and industrial activities, a high quality of railway service is the most desirable. Train service usually varies with the population activities throughout a day and train coordination and service regulation are then expected to meet the daily passengers' demand. Dwell time control at stations and fixed coasting point in an inter-station run are the current practices to regulate train service in most metro railway systems. However, a flexible and efficient train control and operation is not always possible. To minimize energy consumption of train operation and make certain compromises on the train schedule, coast control is an economical approach to balance run-time and energy consumption in railway operation if time is not an important issue, particularly at off-peak hours. The capability to identify the starting point for coasting according to the current traffic conditions provides the necessary flexibility for train operation. This paper presents an application of genetic algorithms (GA) to search for the appropriate coasting point(s) and investigates the possible improvement on fitness of genes. Single and multiple coasting point control with simple GA are developed to attain the solutions and their corresponding train movement is examined. Further, a hierarchical genetic algorithm (HGA) is introduced here to identify the number of coasting points required according to the traffic conditions, and Minimum-Allele-Reserve-Keeper (MARK) is adopted as a genetic operator to achieve fitter solutions.