1,721,373 research outputs found
Mixed Integer Linear Programming Models for Network Reconfiguration and Resource Optimization in Power Distribution Networks
No full textThis chapter deals with two typical optimization problems relevant to the operation of power distribution systems. The first aims at finding the minimum power loss configuration of the network. The second is the so-called Voltage/Var Optimization problem (VVO), i.e. the definition of the most efficient operating condition of voltage control apparatus and reactive power resources. The chapter describes the various parts of the proposed mixed integer linear programming (MILP) model of problems, such as the objective function, and the implementation of the radiality constraint. Both the objective function and the maximum line current constraints require the evaluation of the square value of the real and imaginary parts of each line current phasor. Piecewise linear functions (PLFs) are adopted for the MILP representation of these square values. Also the bus voltage constraints require a PLF representation of the square value of the real and imaginary parts of each bus voltage phasor
New Integral Formulas for the Elements of the Transient Ground Resistance Matrix of Multiconductor Lines
No full textThis paper proposes new formulas for the calculation of the transient ground resistance matrix elements based on the analytical solution of the inverse Laplace transform of the Sunde's logarithmic equation. The new formulas solve the computational issues in the representation of the transition between early time and late time response of the line that arises when adopting the expressions already available in the literature. The formulas are adopted for the calculation of the per-unit length voltage drop due to the transient ground resistance in a multiconductor overhead line and the results match those provided by the numerical inverse Fourier transform of Sunde's logarithmic equation
Comparison of HIV-DNA decay in naive patients starting dolutegravir plus lamivudine or dolutegravir-based triple therapy
No full textN/A Not Availabl
Day-Ahead Scheduling of a Local Energy Community: An Alternating Direction Method of Multipliers Approach
Full text linkThe paper focuses on the day-ahead operational planning of a grid-connected local energy community (LEC) consisting of an internal low-voltage network and several prosumers including generation units, battery storage systems, and local loads. In order to preserve, as much as possible, the confidentiality of the features of prosumers’ equipment and the production and load forecasts, the problem is addressed by designing a specific distributed procedure based on the alternating direction method of multipliers (ADMM). The distributed procedure calculates the scheduling of the available energy resources to limit the balancing action of the external grid and allocates the internal network losses to the various power transactions. Results obtained for various case studies are compared with those obtained by a centralized optimization approach. The results confirm that, in the considered LEC framework, each of the prosumers achieves a reduction in costs or increases revenues in case it participates to the LEC with respect to the case in which it can only transact with an external energy provider
Power system dynamics during large power imbalance phenomena: role of the thermoelectric units
No full textResponse of distribution networks to direct and indirect lightning: Influence of surge arresters location, flashover occurrence and environmental shielding
No full textThe paper deals with the response of distribution networks to direct and indirect lightning. The response of the network is analyzed with the aim of inferring the mean time between failures of the connected transformers. This is accomplished taking into account the voltage at the utility frequency, the flashovers occurrence in the line insulators, the location of surge arresters, and the shielding provided by nearby buildings. Two different transformer failure criteria are assumed: a critical value and a disruptive effect model. The results make reference to multi-conductor overhead systems with two different topologies: simple straight line and a real feeder with laterals. It is shown that such a detailed lightning performance analysis is useful in order to select the most appropriate strategy for the installation of surge arresters, which may allow the achievement of the desired mean time between failures at affordable costs
Inverse Laplace Transform of the Ground Impedance Matrix of Overhead Lines
No full textThis letter deals with the calculation in time domain of the transient ground resistance matrix of an overhead transmission line (TL). Each element of the matrix is evaluated by solving analytically the inverse Laplace transform of the general integral expressions of the ground impedance in frequency domain proposed by Sunde. The presented expressions are suitable for the direct implementation in an electromagnetic transient program (e.g., EMTP-like ones) based on a time domain solution of the TL's equations
A co-simulation platform for the analysis of the impact of electromobility scenarios on the urban distribution network
No full textIn order to facilitate the integration of electromo-bility, a plan for the installation of adequate public charging infrastructures is needed. Such infrastructures could impact the operating conditions of electric power distribution networks with particular reference to those serving urban areas. A co-simulation platform integrating an urban traffic simulator with an electric power system simulator can be a useful tool for the analysis of such an impact. The co-simulator used in this paper represents a portion of the medium voltage distribution network of a middle-size Italian city center, where a significant number of charging stations for electric vehicles is already in operation. The paper presents results obtained by including in the simulator the effects of a multi agent strategy that avoids the overloading of power components in the occasion of large charging requests in the periods of peak load
Blood telomere length gain in people living with HIV switching to dolutegravir plus lamivudine versus continuing triple regimen: a longitudinal, prospective, matched, controlled study
Full text linkBackground Blood telomere length (BTL) is a validated biomarker of aging. ART reduces immunosenescence and has benefits in terms of BTL in people living with HIV (PLWH). However, it has also been observed that ART containing NRTIs, such as tenofovir or abacavir, which are potent inhibitors of human telomerase activity in vitro, might negatively affect BTL. Here we investigated the effects on BTL 1 year after switching to a dual therapy (DT) with dolutegravir + lamivudine versus maintaining a standard triple therapy (TT) with a two-NRTI backbone and an anchor drug. Methods This was a longitudinal, prospective, matched, controlled study that included virologically suppressed adults on stable three-drug ART who either switched at baseline (BL) to DT or maintained TT. The DT and TT groups were 1:1 matched for age, sex, years since HIV diagnosis, years on ART and anchor drug. BTL was assessed by a monochrome multiplex qPCR at BL and after 48 weeks (W48). Results We enrolled 120 PLWH, i.e. 60 participants in each group. At BL, the BTL means were comparable between the two groups (P = 0.973). At W48, viro-immunological status was stable and an overall increase in the mean BTL was observed, i.e., +0.161 (95%CI, 0.054-0.268) (P = 0.004). However, the within-group analysis showed a significant mean BTL gain in the DT group (P = 0.003) but not in the TT group (P = 0.656). Conclusions In this setting of virologically suppressed PLWH, simplifying to dolutegravir + lamivudine was associated with a higher gain in BTL than maintaining triple therapy after the 1 year follow-up. These findings suggest that as a simplification strategy dolutegravir + lamivudine might have a positive effect on BTL
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