1,721,285 research outputs found
Dynamic Stability of Isolated System in presence of PQ Disturbances
No full textThe aim of this paper is to assess the theoretical basis for the dynamic stability analysis in case power-quality disturbances, such as unbalances, harmonics, and interharmonics occur. This kind of pollution that is present in the currents and voltages of the system may cause stability problems especially in isolated electric plants where small generators, supply motor drives, static converters, or nonlinear loads are involved. Some examples based on simulation activity show the influence of these disturbances on the dynamic stability of the generator
Study of Propagation Phenomena in Three-Phase Form Wound Machines Operating at Medium and High Frequency
No full textA three-phase model of asynchronous machines operating at medium or high frequencies is presented. It can be used to study the propagation of surge waves along the stator windings of induction form wound machines. The model is derived from an analogy with a three-phase transmission line. The use of time-space Clarke vectors allows the introduction of mutual coupling between phases. The analytical expressions for voltage waves are derived by means of the Laplace approach to the solution of hyperbolic partial differential equations. Some applicative examples confirm the model validity and can underline some aspects of the project of three-phase winding
Multiconductor transmission line models for PQ and EMC analysis of railway electrification systems
No full textThis paper present and discuss two methods that allows defining MTL models that allows to represent the railway power electrification systems with a reduced number of conductors. Groups of conductors shorted together are replaced with an equivalent conductor and group of conductors grounded are included into the reference conductor. Reducing criteria are developed in the frequency domain and their extension to the time domain is discussed. A section of the Italian 2x25 kV 50 Hz AC high speed railway power system is considered as a benchmark and reduction methods are applied to the MTL cells that represent this kind of electrification system, also including the high voltage grid that supply the Electrical Substation. The equivalent impedance at pantograph terminals and the disturbances on the track circuits caused by trains harmonic current injection are evaluated by using reduced models and taking into account several train positions along the railway line. The numerical results are reported, compared and discussed, considering both precision and computational times
Direct Haar-space control for DC Motors
No full textAfter considering the analysis of a three-phase inverter driving induction motors for railway applications, the authors take into consideration the system formed by a DC motor fed by a chopper. The mathematical analysis has been conducted through Haar functions, a tool based on the general framework of wavelets. The spec advantage consists in being able to solve differential equations by approaching the problem in the Haar domain, instead of adopting a time domain solution. A limited number of Haar coefficients are necessary to perform this task. Especially transient conditions during the starting process can usefully be examined in such a way, putting into evidence specific characteristics of the chopper motor system. An example describing the application of such technique is presented and critically describe
Some notes on wavelet analysis of time-variant electrical networks
No full textAfter presenting a new approach for the analysis and the resolution of linear time-variant circuits, based on wavelet functions, the authors introduce some specific considerations related to matrix properties associated with such methodology. The simple recursive algorithm for the construction of the integral and convolution matrices and the topological matrix are evaluated in depth in order to bring out the most interesting features. Proposals for numerical optimizations are also given. An example including a three-phase inverter studied using such a technique is presente
Comparative Life Cycle Assessment on Different End-of-Life Management of Lithium-Ion Electric Vehicle Batteries: A Literature Review and an Application Scenario
No full textBattery packs for electric mobility application, typically lithium-ion batteries, need to be particularly performant to guarantee minimum standards to the Electric Vehicle (EV). Therefore, they are used for such application for a reduced span of their lifetime. Once their mobility application is over, various End-of-Life (EoL) strategies are possible. These strategies includes direct disposal, recycling, remanufacturing, refurbishment and repurposing, from the least to the most preferred. Each EoL strategy involves different environmental, technical, economical and safety aspects, that regulatory bodies are defining by legislating on batteries undertaking a life cycle approach, considering the battery from its manufacturing to its second-life or disposal. This paper focuses on the environmental aspects, thus the latest European regulatory framework is analysed and a critical literature review on comparative life cycle assessments on different EoL strategies for lithium-ion EV battery packs is proposed. Additionally, this paper proposes a possible application scenario, where second-life batteries are deployed as stationary storage in an EV charging station
Calculation of Rail Internal Impedance by using Finite Elements Methods and Complex Magnetic Permeability
No full textHaar state equations for power electronics sysetm modelling
No full textThe authors extend to this work some considerations on the Haar analysis of switching circuits introduced in previous papers. Specific properties related to matrices associated with the analysis and the resolution of linear time-variant circuits, have been used to perform such study and define transient behavior for the line current of a power electronic device. The simple recursive algorithm for the construction of the integral and convolution matrices and the topological matrix has been applied to evaluated more in depth the most interesting features of the system. The example describing the application of such technique to a three-phase inverter provides also significant starting points for future researc
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