1,721,011 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
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
Resonant coil matrix shielding for dynamic WPT systems
No full textIn this article, a magnetic shield for automotive Wireless Power Transfer (WPT) systems is proposed. Its innovative feature consists in the positioning of the shield, that is part of the Ground Assembly (GA) of the WPT system. Passive coils, assembled in an array-like structure to build the shields properly located near the transmitting coils are investigated. Currently, there are a variety of shielding methods, each of them with its peculiar feature. The proposed method is simple and does not increase the transmitting and the receiving coil sizes, a constraint that is often critical from a practical and an economical point of view. The main characteristic of the proposed shielding method is the location of the shielding coils on the same level as the GA. The results here presented are validated by Finite Element (FE) based simulations and are referred to an experimental prototype of wireless charging systems for electric vehicles operating at 85 kHz with a transmitted nominal power of 3.3 kW. The results show that the proposed shield reduces the leakage magnetic flux density in the system up to 37% with a marginal impact on the transmission efficiency, complying the SAE J2954 international standard
An Electro-Thermal Model for LFP Cells: Calibration Procedure and Validation
Full text linkLithium batteries for energy storage systems are a prominent solution for both stationary and mobile applications. Electro-thermal modelling of the cell is a useful tool for monitoring voltage and temperature in order to predict battery behaviour especially in cases of critical operative con-ditions. This paper provides a modelling approach focusing on the calibration of parameters of an electro-thermal model for large prismatic LFP lithium cells. The designed model is tuned by means of experimental tests that identify a set of parameters that are function of a cell’s state-of-charge and temperature. The model outputs are voltage, cell surface, and internal temperature profiles, which are validated against experimental data referring to realistic working conditions, even providing an intense level of thermal stress. The model accuracy is marked by a voltage mean average error lower than 1% and a mean cell surface temperature deviation lower than 1 K
Experimental analysis of LFP lithium cells aging
No full textAging of batteries is one the most significant aspects to be considered, when engaged in stationary or mobile applications. With reference to a project currently in progress, based on an accurate analysis of fast charging operations, some experimental tests have been carried out on an LFP lithium cell, to analyze its aging over time, when subjected to different solicitations of power requested. Additionally, several aging indicators have been defined, measured and analyzed, to be compared each other and to verify their correlation with the cell aging levels. Preliminary results show that part of these indicators can correctly be used as good cell aging predictors, giving a unique aging trend
Technical and economic analysis of EV high-power recharging pools equipped with storage
No full textA comprehensive network of high-power recharging points will be fundamental to enable long-distance travel for electric vehicles. However, the distribution grid may not be always capable to provide such high levels of power in every area. From this prospect, recharging pools equipped with battery storage system provide the opportunity to limit the maximum power request to the grid, avoiding the need for an upgrade to the grid connection. This solution can be implemented by means of various configuration depending on the storage system size and the relative energy management, leading to different costs. This paper carries out a technical and economic analysis of a high-power recharging pool connected to the low voltage distribution network and equipped with a stationary storage system. A simulation model developed in Modelica language is used to compare three different storage configurations. Results indicate that a peak shaving BESS is the most feasible solution. It is also observed that a reduced size would improve the profitability of the investment, supporting the EV recharge with a reasonable additional waiting time
Voltage-current based algorithm for the on-line estimation of equivalent internal resistance of Lithium-Cobalt-Oxide cells at different aging levels
No full textThis paper deals with the problem of the identification of lithium cell parameters to be correlated with the cell level of aging. Three identical Lithium-Cobalt-Oxide (LCO) commercial cells at three different State-of-Life (SOL) values are experimentally tested, and two parameter estimations are applied, focusing on the cell internal resistance, which appears significantly sensitive to different cell aging levels. After displaying how the single cells under study can be calibrated through an off-line procedure by means of equivalent electrical circuit approach, the development of a voltage-current based algorithm to be applied on-line and capable of estimating an 'equivalent internal resistance' to be correlated with cell SOL is proposed. The robustness and the online applicability of the algorithm is tested on different realistic scenarios, as well as different State-of-Charge levels. Results confirm the capability of the proposed algorithm to be potentially applied for the online State-of-Life estimation for lithium cells
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