1,720,983 research outputs found
Metrology Infrastructure for Energy and Power Quality in DC Railway Systems
Full text linkL'abstract è presente nell'allegato / the abstract is in the attachmen
Method for detecting an electric arc occurring between a railway overhead contact line and a railway traction unit and corresponding detection arrangement
No full textSetup for the Calibration of Current Measuring Systems Under DC Signals Affected by Ripple
No full textUncertainty Evaluation of a Supercapacitor Equivalent Circuit Parameters
No full textThe accurate simulation of the behavior of a supercapacitor (SC) and its control in an electronic system, cannot be achieved by a simple one-branch circuit. A correct simulation requires the use of more complex equivalent circuits, with at least two or three branches. These equivalent circuits guarantee a good reproduction of the device’s behavior. The effectiveness of an equivalent circuit is linked to the limits of the circuit parameter identification, which is commonly achieved by means of the voltage and current measurement of charge and self-discharge cycles. The uncertainty in the identification of these circuit parameters, is dependent on the accuracy of the measurement instrumentation and on the repeatability of the SC. A cycle for determining the parameters can extend over a few hours for larger SCs, also considering the time needed by the software algorithm for the parameter identification. Therefore, having a large set of cycles including the parameters determination is a time-consuming procedure. In this study, an efficient method for the repeatability and uncertainty assessment of the equivalent circuit parameters is proposed; this approach relies on a limited set of experimental data and on a single parameter identification process. The analysis presented in this paper highlights how the limited repeatability of the device is an important source of uncertainty for the identification of the equivalent circuit parameters, but it is not the main one for all parameters
Impact of DC Transient Disturbances on Harmonic Performance of Voltage Transformers for AC Railway Applications
Full text link: This paper analyzes the impact of typical DC transient events occurring in railway grids on the frequency performance of instrument transformers (ITs) installed onboard trains and in AC substations for power quality (PQ) applications. PQ monitoring in railway systems is an issue of great interest because it plays a key role in the improvement of energy efficiency. The measurement chain for the PQ measurements, at 15 kV at 16.7 Hz and 25 kV at 50/60 Hz, commonly includes ITs to scale the voltage to levels fitting the input of the measurement units. Nevertheless, the behavior of ITs in the presence of PQ phenomena represents an open issue from a normative point of view, even for those installed in conventional AC power supply systems. In this context, the paper presents a possible definition of DC transient disturbances test waveforms, a measurement procedure, and a setup to assess the impact of these disturbances on the harmonic performances of ITs for railway systems. Preliminary experimental tests carried out on two commercial ITs under wide ranges of variation for the amplitude and the time duration of DC disturbances show that, in some cases, the error introduced in harmonic measurements can exceed 100%
Optimal Operation of a Smart Electrified Traction System: A Review
No full textSmart Electrified Traction Systems (SETS) ma: play a pivotal role towards the decarbonization of the transpor sector and the integration of renewable energy sources. For thi reason, the paper proposes an up-to-date state of the art revier of the main configurations, operational schemes and flexibl assets forming these networks. Also, the intrinsic flexibility 0 these tractions systems calls for the optimal management of th assets in order to minimize the operational costs. This pape also reviews the main formulations of customized optimal powe flow problems, which incorporate the intrinsic features of thes networks. The critical analysis focuses on the reformulation techniques or algorithms adopted to overcome non-linear an non-convex constraints, typical of optimal power flow problems
Digital Twin Implementation for Urban Tram Systems: A Data-Driven Model for Estimating Traction Current
No full textThe urgent need to decarbonize our cities places the transport sector, responsible for a significant share of greenhouse gas emissions, at the center of global sustainability efforts. Achieving this goal requires not only the electrification of public transport systems but also ensuring their efficiency and effectiveness to encourage widespread adoption over private vehicles. A promising strategy to modernize such systems is the implementation of a Digital Twin (DT), a virtual counterpart of the infrastructure that integrates real-time field data from strategically deployed sensors. This work focuses on trambased urban transport systems, where one of the most critical parameters for DT applications is the traction current absorbed by each vehicle. However, the deployment of dedicated onboard current sensors is often constrained by economic and timerelated limitations. To address this, we propose a transitional solution: a data-driven model capable of estimating tram current consumption using only GPS-based vehicle position data. Specifically, this paper presents a hybrid neural network architecture combining Long Short-Term Memory (LSTM) and Gated Recurrent Unit (GRU) models. The network processes speed and acceleration profiles derived from open-access GPS data, eliminating the need for onboard instrumentation. The model was trained and validated with data from a targeted field measurement campaign, achieving a Mean Absolute Error (MAE) of 61.3 A and a Root Mean Square Error (RMSE) of 95.6 A. Given that the maximum absorbed current exceeds 900 A, these error values indicate that the model's predictive performance is within an acceptable range. This methodology provides a robust, low-cost solution for enabling early-stage DT development in Urban Traction Electrification Systems (UTES), supporting simulation and planning in the ongoing digital transformation of public transport
Energy Efficiency Improvement with Reversible Substations for Electrified Transportation Systems
Full text linkInternational audienceMore and more often overall energy efficiency of an electrified transportation system appears as a target of new constructions, sometimes with incomplete definitions of performance indexes to assess that target has been reached. A worked out example is based on the introduction of reversible substations. Reversible substations are a method to improve energy efficiency, whose application in an existing system can be progressive and does not require large traffic intensity to be effective. Their effectiveness depends on some system parameters (nominal catenary voltage in particular). A simulation model fed with experimental data from a line section of Metro de Madrid is used to demonstrate the operation and optimization of reversible substations. Background: The ambitious reduction of CO 2 greenhouse gas emission within 2050 declared by the European Commission also involves transportation systems. In this context an optimum recovery of the electric braking energy produced by railway vehicles is more and more relevant. Several strategies to completely recover the braking energy are being developed and applied. A methodology that allows the accurate determination of the amount of recovered energy in real operating conditions becomes then a valuable tool
Power Quality Assessment in Railway Traction Supply Systems
Full text linkThe assessment of the power quality (PQ) could be a valuable tool to foster the efficiency of the railway systems. PQ is a well-addressed topic in conventional ac 50/60 Hz power systems, and many procedures, algorithms and measurement systems were presented in the international standards and widely discussed in the scientific literature. A less explored research field is the assessment of the PQ in the railway traction supply systems, in particular with reference to the dc and 16.7 Hz systems. The article explores this theme, proposing an extension of the definitions and of the standard measurement procedures for some of the main PQ indexes, well defined and widely used for conventional power systems, in order to be used also in all railway traction supply systems. The limits or difficulties of applicability are discussed with reference to measurements performed both on-board and in substation. The proposed procedures are applied to an experimental case of a real dc railway system with a large measurement campaign
Filter Transients onboard DC Rolling Stock and Exploitation for the Estimate of the Line Impedance
No full textPower supply transients in dc railways related to filter charging may trigger network and filter oscillatory responses, as well as cause very fast voltage spikes. These phenomena are relevant not only for Power Quality and EMC, but also for their impact on the measured pantograph quantities e.g. for power and energy consumption estimate. The broadband excitation of the system gives the possibility of attempting the identification of the network impedance. The experimental results are discussed and compared to the output of a circuit and a distributed parameter simulator. Matching between simulated and experimental data is very good. © 2020 IEEE
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