1,721,012 research outputs found
Heavy-duty hybrid transportation systems: Design, modeling, and energy management
No full textThis chapter is centered on the design, modeling and energy management of heavy-duty transportation systems. After showing general definitions and conventions, the problem of energy management is addressed with reference to heuristic approaches and global optimization control techniques. After presenting the problem in the most general formulation, a detailed case study is shown, related to the design of a working machine typically used in construction site. The main steps are modeling of the conventional hydraulic working machine, identification of an electrified hybrid architecture, selection of a heuristic energy management strategy to be implemented online, verification and comparison with respect to offline optimal control solution, in order to have a benchmark with the selected strategy
Integration of small-scale power systems
No full textElectrochemical storage systems are increasingly being considered today. This chapter focuses attention on the different lithium typologies available today, from the cell characteristics to the composition of the battery packs. As main characteristics, charging techniques and life issues have been addressed, also by defining indicators currently used. Lithium solutions have been presented also by distinguishing between energy-oriented and power-oriented typologies. Also, other kinds of power-oriented technologies have been presented, in particular, supercapacitors and flywheels. A significant part is dedicated to numerical modeling, in order to identify equivalent electrical networks for the electrochemical cell/battery. Finally, battery selection criteria are provided to the reader, in order to properly size the storage system for the considered application
Use of Modelica language to simulate electrified railway lines and trains
No full textSimulation of multi-engineering systems typically requires many issues to be solved, which are to be addressed by developing appropriate modeling and simulation programming techniques. In the last years, the authors have participated in several studies in which they analyzed in detail electrified railway systems and simulated them using Modelica language. After a few years of study, despite the huge complexity of these systems, it has appeared evident that Modelica language is very well suited and able to effectively solve the typical issues they present. While specific railway system simulations have already been discussed in specific papers, whose focus was on application and actual results, in this paper, the authors show how to use Modelica language to solve specific modeling issues through suitable programming techniques. Moreover, the issues to be solved and the conceived techniques may be interpreted in a general way and to be applied also in different engineering domains. Finally, this paper briefly recalls the principal results obtained in previous specific papers, in which these techniques were fully implemented
State-of-charge estimation based on model-adaptive Kalman filters
No full textThis article presents a set of algorithms for the estimation of state of charge, specifically deployed for lithium-ion batteries. These algorithms are based on appropriate battery models. These models can be developed having different levels of accuracy, also including the possibility to correctly represent the hysteresis voltage behaviour of the selected lithium cells. In addition, different identification methods of the battery model parameters may also be considered, considering tabulated parameters, calibrated in previous tests, or online parametrization tools. State of charge is then evaluated using non-linear Kalman filter techniques. Effectiveness of identification methods, also with the performance offered by Kalman filter itself, has been accurately evaluated through experimental tests. To verify the robustness of the proposed algorithms, some disturbances were introduced and evaluation was also conducted at different state of charge initial conditions and sampling times
Development of an Energy Management System for AC/DC hybrid networks: From abstract functional requirements to the flexible tool
No full textAlternating Current (AC) networks are the predominant technologies used to transmit and distribute electricity worldwide. However, the penetration of renewable sources and the decreasing costs in power electronics are making Direct Current (DC) systems a promising approach to increase energy efficiency, reliability, and resilience, while exploiting synergies with AC systems. Therefore, appropriate Energy Management Systems (EMS) are mandatory for achieving energy efficiency and economic profitability, which shall account for both AC and DC components and networks. Moreover, in practical applications, multiple different control methodologies have been proposed to manage power systems, with different simulation tools, development platforms and software tools, which rarely have the same interface. This study aims at proposing the generalized framework and the tool for the development of a flexible EMS, which could be easily interfaced with standard commercial tools, e.g. NEPLAN or PowerFactory. The theoretical and functional requirements of the methodology can lay the foundations for further research studies and the proposed results confirm the robustness of the methodology
Use of AMT transformers and distributed storage systems to enhance electrical feeding systems for tramways
Full text linkTramway systems are more and more diffused today, to reduce pollution and greenhouse emissions. However, their electrical feeding substations can have significant margin for improvement. Therefore, it is questionable which kind of changes can be introduced, by changing their main features. First of all, transformer technology can be enhanced, by moving from the standard transformer to the amorphous metal one; thus, guaranteeing a significant reduction in losses. Then, by installing one dedicated storage systems for each substation. This solution can help to increase the energy efficiency; thus, recovering the tram braking energy and reducing the delivered energy from the grid, and also the reliability of the system; thus, guarantee different levels of services, in the case of failure of a feeding substation. This paper investigates in a systematic approach the two proposed solutions. In particular an amorphous metal transformer has been properly designed, and performance compared to the standard one. Then, evaluation of distributed storage installation was performed, and the aspects of reliability for these systems evaluated. Results have shown the general feasibility of the proposed solutions, showing a significant energy saving with respect to the conventional ones
Optimal sizing of microgrids: On the design equivalences of different objective functions
No full textDecentralized energy systems have risen attention of policy makers and academia for their potentiality to improve the electricity service, reduce costs and foster the rural electrification in developing countries. Several design methodologies have been proposed to optimize the size of different components, which is crucial especially in off-grid configurations. Given the interests of private companies, profitability aspects are becoming the major focus; nevertheless, there is no general agreement on the best indicator to use to assess if and how much the microgrid is cost effective. Moreover, different economic indicators can correspond to several sizing solutions, which makes the selection of the objective function a very critical aspect. In this study, we propose a comparison between main indicators used to optimize off-grid microgrids, including theoretical and numerical comparisons. Equivalences and inequalities among typical economic criteria are considered, including formulations accounting for the cost of the energy-not-served. Numerical case studies supporting the analysis are provided
Rolling-horizon scheduling strategies for off-grid systems: On the optimal redispatching frequency and the effects of forecasting errors
No full textAchieving universal electricity access is a serious challenge that developing countries are facing with. Decentralized systems are widely recognized as part of the solution, especially for remote areas where traditional approaches would be too expensive. In particular, mini-grids, which are local systems conceived to produce and distribute electricity, can provide good quality electricity enabling the development of basic industrial and commercial activities. Unfortunately, the significant business risks in that areas are hampering private companies in developing initiative in many areas of the world; hedging risks and reducing costs by achieving the optimal design and operation of mini-grids is then crucial. Advanced rolling-horizon operating strategies can lead to interesting savings in operating costs, which can improve the profitability of the project. In fact, predictive strategies advance the system's requirements and, by re-dispatching the system infra-daily, can better cope with load and RES uncertainties. In the present study, we investigate the effect of both the redispatching frequency and the forecasting errors into the operating costs, in order to help practitioners and researchers in identifying the best parameters to use in design and operation of mini-grids. A numerical case study is proposed for a mini-grid in Soroti, Uganda
Electro-mechanical modelling and simulation of 2×25 kV railway systems
No full textThe 2 × 25 kV railway systems are multi-engineering systems which involve many simulation issues. They require appropriate modelling and simulation tools to solve these issues and accurately reflect characteristic changes during system operation. This paper analyses the AC railway systems characteristics and several hypotheses that are proposed to simplify these simulation issues. After that, the systems simulation models are built by utilisation of two different cyber-physical modelling and simulation tools: Modelica and Matlab-Simscape. The respective characteristics of these two tools are compared in this paper as well. The results show that the two different tools have the nearly equivalent accuracy, and Modelica is more flexible and easier to use
- …
