Search results for "temi"
showing 10 items of 3194 documents
Wind Turbine Mechanical Characteristics and Grid Parameters Influence on the Transient Voltage Stability of a Fixed Speed Wind Turbine
2008
This paper describes the effect of wind turbine mechanical characteristic of construction and grid parameters on the transient voltage stability of a fixed speed wind turbine (FSWT) connected to a simple grid. The model of FSWT has been developed in Matlab/Simulink. Using this model, a three-phase fault is applied close to the wind turbine (WT) and cleared by disconnecting the faulted line. The effects of mechanical construction of WT and of grid parameters on the voltage stability of this simple case are evaluated and discussed. The considered parameters are the inertia coefficient of the WT, the short-circuit power at the connection bus, the hub-generator resonant frequency, the wind spee…
Effects of Electrical Parameters of Induction Generator on the Transient Voltage Stability of a Fixed Speed Wind Turbine
2008
This paper describes the effect of electrical parameters of the induction generator on the transient voltage stability of a fixed speed wind turbine connected to a simple grid; the dynamic behavior of a wind turbine connected to the grid is examined. The model of the fixed speed wind turbine has been developed in the simulation tool Matlab/Simulink. Itpsilas composed by the induction generator, the shaft system, the aerodynamic model of the wind turbine rotor and the pitch control system. Using this model, a three-phases fault is applied close to the wind turbine and cleared by disconnecting the faulted line. The effect of different electrical parameters of the induction generator on the vo…
Current and Voltage Behaviour During a Fault in a HV/MV System: Methods and Measurements
2015
When a single line to ground fault happens on the MV side of a HV/MV system, only a small portion of the fault current is injected into the ground by the ground-grid of the faulty substation. In fact the fault current is distributed between grounding electrodes and MV cables sheaths. In systems with isolated neutral or with resonant earthing this may be sufficient to provide safety from electric shock. Experimental measurements were performed on a real MV distribution network: a real single line to ground fault was made and fault currents were measured in the faulty substation and in four neighbouring substations. In this paper the problem of fault current distribution is introduced, the te…
Influence of LV neutral grounding on global earthing systems
2015
International Standards define a Global Earthing System as an earthing net created interconnecting local Earthing Systems (generally through the shield of MV cables and/or bare buried conductors). In Italy, the regulatory authority for electricity and gas requires distributors to guarantee the electrical continuity of LV neutral conductor. This requirement has led to the standard practice of realizing “reinforcement groundings” along the LV neutral conductor path and at users’ delivery cabinet. Moreover, in urban high-load scenarios (prime candidates to be part of a Global Earthing System), it is common that LV distribution scheme creates, through neutral conductors, an effective connection…
Urban Energy Hubs and Microgrids: Smart Energy Planning for Cities
2017
In this chapter, we try to connect the urban design features with energy consumption and consequent pollution parameters. After a review of a selected set of approaches to Urban Energy Systems study with a special focus on electrical power systems, urban energy systems are proposed as networks of multi-source hybrid energy hubs, where different energy flows are collected at the same bus and can be stored, delivered or transformed as needed. Resources at the hub and infrastructures interact with each other; therefore, both definition and boundaries of such energy systems at urban level are difficult to be clearly outlined. Similarly, the possibility to generate new operational models based o…
A multi-agent system reinforcement learning based optimal power flow for islanded microgrids
2016
In this paper, a distributed intelligence algorithm is used to manage the optimal power flow problem in islanded microgrids. The methodology provides a suboptimal solution although the error is limited to a few percent as compared to a centralized approach. The solution algorithm is multi-agent based. According to the method, couples of agents communicate with each other only if the buses where they are located are electrically connected. The overall prizing system required for learning uses a feedback from an approximated model of the network. Based on the latter, a distributed reiforcement learning algorithm is implemented to minimize the joule losses while meeting operational constraints…
An expert system hybrid architecture to support experiment management
2014
Specific expert systems are used for supporting, speeding-up and adding precision to in silico experimentation in many domains. In particular, many experimentalists exhibit a growing interest in workflow management systems for making a pipeline of experiments. Unfortunately, these type of systems does not integrate a systematic approach or a support component for the workflow composition/reuse. For this reason, in this paper we propose a knowledge-based hybrid architecture for designing expert systems that are able to support experiment management. This architecture defines a reference cognitive space and a proper ontology that describe the state of a problem by means of three different per…
Time-dependent effects of polystyrene nanoparticles in brine shrimp Artemia franciscana at physiological, biochemical and molecular levels
2019
Micro- (<5 mm) and nanoplastics (<1 μm) are emerging threats for marine ecosystems worldwide. Brine shrimp Artemia is recognized as a suitable model among planktonic species for studying the impact of polystyrene nanoparticles (PS NPs) through short and long-term bioassays. Our study aims to evaluate the time-dependent effects of cationic amino-modified PS-NH (50 nm) in A. franciscana after short- (48 h) and long-term exposure (14 days). For this purpose, nauplii were exposed to a concentration range of PS-NH (0.1, 1, 3 and 10 μg/mL) in natural sea water (NSW), and physiological, biochemical and molecular responses were investigated. Short-term exposure to PS-NH caused a decrease in nauplii…
Effect of Integrating Photovoltaic Systems on Electrical Network Losses Considering Load Variation
2018
Planning of Distributed Generation (DG) units in the power distribution networks is an important issue, one of the most important considerations that is directly affected by installing DG units is the power losses. Improper allocation of DG units to the grid can lead to a noticeable increase in the power losses. Moreover, the load variation is considered as critical matter when studying the optimal scenario that minimizes the power losses in the network. The aim of this paper is to investigate the effect of integrating photovoltaic (PV) units on the distribution network losses considering load variation. The optimal parameters of the DG units were calculated for the various load demands in …
Deep drawing versus incremental forming processes: A comparative cradle to gate analysis
2012
The evaluation and reduction of the environmental impact of manufacturing processes have become a crucial issue in the last few years, addressing the interest of industrial and academic research towards greener solutions and technologies. Reducing input materials and energy requirements has become an imperative action in the industrial practice. As a matter of fact, strong is the concern on lightweight solutions and technologies for sheet stamping operations especially in the automotive sector. However, the knowledge on how impactful such processes are is still poor. In this paper, a comparison between a traditional deep drawing and an single point incremental forming process is investigate…