This article addresses the problem of optimizing voltage profiles in distribution networks. The voltage optimization is split into two stages; the former is performed offline and the latter online. ...First, the network is partitioned into several weakly coupled voltage control zones (VCZs) with pilot nodes (PNs). Then, the partitioning is used to optimize the voltage profiles of the distribution systems on the frame of a two time-scale-based coordinated approach. At the first level, a centralized voltage optimization problem (VOP), minimizing the distance of bus voltages at the PNs from their reference values and subject to linearized power flow equations, is solved to fix the positions of the on-load tap changer and of step-voltage regulators, and the reactive powers provided by capacitor banks. At the second level, the VOP is implemented according to a decentralized approach, in which the solution is obtained by applying a distributed algorithm based on the alternating direction method of multipliers. It optimizes in each VCZ the voltage at the PN by acting on the active and reactive powers provided by the distributed energy resources present in the VCZ; the VCZ solutions are driven to the global optimum of the whole distribution system by a limited data exchange between the PNs. The proposed approach reduces the complexity and computational burden typical when solving the VOP on a large scale system. The proposed strategy is tested on the modified IEEE 123-bus system; various load and generation scenarios are analyzed proving the effectiveness of the proposed approach in achieving the objective of voltage regulation.
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•Higher B-type LMW-GS expression in modern genotypes contributes to gluten strength.•A marked decrease in ω-type gliadin expression is observed in modern genotypes.•Differences in ω-5 ...gliadin expression appear also related to the number of isoforms.•Old and modern genotypes show similar α- and γ-type gliadin expression.•A higher ω-gliadins and HMW-GS content was observed under water deficit.
The impact of breeding on grain yields of wheat varieties released during the 20th century has been extensively studied, whereas less information is available on the changes in gluten quality associated with effects on the amount and composition of glutenins and gliadins. In order to explore the effects of breeding during the 20th century on gluten quality of durum wheat for processing and health we have compared a set of old and modern Italian genotypes grown under Mediterranean conditions. The better technological performance observed for the modern varieties was found to be due not only to the introgression of superior alleles of high (HMW-GS) and low molecular weight (LMW-GS) glutenin subunits encoded at Glu-B1 and Glu-B3 loci, but also to differential expression of specific storage proteins. In particular, the higher gluten index observed in modern genotypes was correlated with an increased glutenin/gliadin ratio and the expression of B-type LMW-GS which was, on average, two times higher in the modern than in the old group of durum wheat genotypes. By contrast, no significant differences were found between old and modern durum wheat genotypes in relation to the expression of α-type and γ-type gliadins which are major fractions that trigger coeliac disease (CD) in susceptible individuals. Furthermore, a drastic decrease was observed in the expression of ω-type gliadins in the modern genotypes, mainly ω-5 gliadin (also known as Tri a 19) which is a major allergen in wheat dependent exercise induced anaphylaxis (WDEIA). Immunological and 2DE SDS-PAGE analyses indicated that these differences could be related either to a general down-regulation or to differences in numbers of isoforms. Lower rainfall during grain filling period was related to overall higher expression of HMW-GS and ω-gliadins. In conclusion, breeding activity carried out in Italy during the 20th century appears to have improved durum wheat gluten quality, both in relation to technological performance and allergenic potential.
A key issue in Low Voltage(LV) distribution systems is to identify strategies for the optimal management and control in the presence of Distributed Energy Resources (DERs). To reduce the number of ...variables to be monitored and controlled, virtual levels of aggregation, called Virtual Microgrids (VMs), are introduced and identified by using new models of the distribution system. To this aim, this paper, revisiting and improving the approach outlined in a conference paper, presents a sensitivity-based model of an LV distribution system, supplied by a Medium/Low Voltage (MV/LV) substation and composed by several feeders, which is suitable for the optimal management and control of the grid and for VM definition. The main features of the proposed method are: it evaluates the sensitivity coefficients in a closed form; it provides an overview of the sensitivity of the network to the variations of each DER connected to the grid; and it presents a limited computational burden. A comparison of the proposed method with both the exact load flow solutions and a perturb-and-observe method is discussed in a case study. Finally, the method is used to evaluate the impact of the DERs on the nodal voltages of the network.
Voltage control is becoming a key issue in active distribution systems, which are electric distribution networks characterized by a large penetration of DERs. Traditional voltage control devices, as ...well as the active and reactive powers injected by DERs, can be used as ancillary services to support voltage profiles along the distribution feeders. Due to the peculiar characteristics of active distribution systems, the decentralized control approach presents the most promising technical and economical features. In the paper, the decentralized voltage control structure is hierarchically decomposed into different control levels, characterized by different objectives and time frames. The primary and secondary control levels have been analyzed, always according to a decentralized approach. For each level, the various techniques for solving the voltage control problem that have been proposed in the literature are presented, and their main features compared. The main open issues related to the real time practical implementation of the decentralized architectures at both primary and secondary voltage control levels are investigated, keeping always in mind both technical and economical aspects, which always represent the components of a trade-off solution.
► The use of ultrasounds for biometric purposes has been evaluated. ► B-scan and C-scan images of human hand palms have been analysed and compared. ► The moving linear array technique has been ...exploited. ► Several anatomic elements have been measured as biometric parameters. ► A new biometric characteristic called “3D hand geometry” is defined and proposed.
In this work the moving ultrasound linear array technique has been used to perform 3D echographic images of different human hands, in order to evaluate this technique to biometric recognition purposes. An automated set up, based on a commercial echographic machine provided with a high frequency (12
MHz) linear array, has been built up. The probe is moved in the direction orthogonal to the array and at each step a B-scan is performed and stored to form a 3D matrix representing the under skin hand volume.
B-scan and C-scan images of the hand of different users were analysed and compared. The results have shown that, in the analysed region (about 10
mm under the palm skin), there are several anatomic elements (including hand bones, bending tendons, muscle tissue, blood vessels) that can be exploited for measurements of biometric parameters.
The characteristics of the proposed technique are compared with those of the 2D optical hand geometry, which is a well established biometric technique, and its possible advantages are underlined and discussed.
Within an investigation focused on effect of casting conditions on steel quality in an industrial beam blanks mould, different nozzle geometries were tested with Computational Fluid Dynamics ...modelling. The innovative nature of the work consisted in feeding with only one nozzle, whereas two nozzles in the flange-tip zone are commonly used. This configuration has the advantage of a simplified mono-slide gate casting layout, but single nozzle feeding can bring about risks of too high steel velocity in the mould, harmful for shell integrity and meniscus stability. Having in mind the mentioned constraints, different geometry solutions were checked and, to assess the solutions found, suitable indices were defined, related to flow conditions able to prevent slag entrapment at the meniscus, and hot-spotting at walls, harmful for the solid shell integrity. The modelling work gave general indications on undesired flow features and guidelines to improve reference conditions, involving number of holes and holes angle, size and shape. For the caster mould and the operating conditions under concern, a solution was found satisfying the indices, and expected to fulfil the quality requests. It consisted of a nozzle with a 50 mm diameter throat, a 50 mm× 60 mm elliptical lateral port inclined 25° downwards and a 20 mm-diameter bottom hole. A water model check with such a nozzle prototype validated the model supporting the solution identified to be used on plant.
A market characterized by economic uncertainty and increased competition has led industrial enterprises to find ways to improve operational efficiency and reduce energy costs. In this context, the ...Demand Response (DR) has drawn ever greater attention from industries, allowing the shift of the electricity usage from their normal consumption patterns in response to changes in the price of electricity over time. This study proposes an innovative control strategy for renewable-based Load Shifting (LS) system designed on, at the same time, energy, economic, and environmental performance to realize an effective DR for industrial enterprises. The proposed techno-economic model is based on power flow management, economic indicators, such as NPV, IRR, and DPP, and associated CO2 emissions, adopting both deterministic and stochastic approaches. A realistic government incentive program framed in a potential carbon-based market is also assessed and validated. The resulting solution is obtained through a sensitivity analysis of several parameters, including the operating conditions of 15%, 20%, 30%, 35%, and 45% LS. MATLAB-Simulink simulations provide the following sizes for both storage and photovoltaic systems of 38, 68, 87, 115, 153 kWh and 18, 18, 32, 43, 61 kWp, respectively. Results show the profitability of the proposed DR, with a payback period that ranges from 6 to 10 years and within 3 years when incentives are considered. NPV and IRR range from 34,261 to 101,428 € and from 7% to 15.9%, respectively. The amount of CO2 emissions is reduced up to 47.7% for the highest LS percentage. Finally, the investigated incentive program led to CO2 prices between 18.2 and 551.9 €/tonCO2. Finally, results from the stochastic analysis show a good consistence with deterministic results.
•A DR strategy for a real industrial application is presented.•A novel LS based on energy, economic, and environmental performance is presented.•The proposed DR improves economic and environmental efficiency of the enterprise.•The amount of CO2 emissions is reduced up to 47.7% for the highest LS percentage.•Power flows management proves the feasibility of LS up to 45%.
This paper deals with the problem of the voltage profile optimization in a distribution system including distributed energy resources. Adopting a centralized approach, the voltage optimization is a ...non-linear programming problem with large number of variables requiring a continuous remote monitoring and data transmission from/to loads and distributed energy resources. In this study, a recently-proposed Jacobian-based linear method is used to model the steady-state operation of the distribution network and to divide the network into voltage control zones so as to reformulate the centralized optimization as a quadratic programming of reduced dimension. New clustering methods for the voltage control zone definition are proposed to consider the dependence of the nodal voltages on both active and reactive powers. Zoning methodologies are firstly tested on a 24-nodes low voltage network and, then, applied to the voltage optimization problem with the aim of analyzing the impact of the R/X ratios on the zone evaluation and on the voltage optimization solution.
This paper presents the preliminary results of our research activity aimed at forecasting the number of voltage sags in distribution networks. The final goal of the research is to develop proper ...algorithms that the network operators could use to forecast how many voltage sags will occur at a given site. The availability of four years of measurements at Italian Medium Voltage (MV) networks allowed the statistical analyses of the sample voltage sags without performing model-based simulations of the electric systems in short-circuit conditions. The challenge we faced was to overcome the barrier of the extremely long measurement times that are considered mandatory to obtain a forecast with adequate confidence. The method we have presented uses the random variable time to next event to characterize the statistics of the voltage sags instead of the variable number of sags, which usually is expressed on an annual basis. The choice of this variable allows the use of a large data set, even if only a few years of measurements are available. The statistical characterization of the measured voltage sags by the variable time to next event requires preliminary data-conditioning steps, since the voltage sags that are measured can be divided in two main categories, i.e., rare voltage sags and clusters of voltage sags. Only the rare voltage sags meet the conditions of a Poisson process, and they can be used to forecast the performance that can be expected in the future. However, the clusters do not have the characteristics of memoryless events because they are sequential, time-dependent phenomena the occurrences of which are due to exogenic factors, such as rain, lightning strikes, wind, and other adverse weather conditions. In this paper, we show that filtering the clusters out from all the measured sags is crucial for making successful forecast. In addition, we show that a filter, equal for all of the nodes of the system, represents the origin of the most important critical aspects in the successive steps of the forecasting method. In the paper, we also provide a means of tracking the main problems that are encountered. The initial results encouraged the future development of new efficient techniques of filtering on a site-by-site basis to eliminate the clusters.
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