1,721,497 research outputs found
Modeling of Independent Energy Communities Sharing the Same Distribution Network
Full text linkRecent regulatory frameworks in several countries are introducing energy communities, which are collectives of prosumers and users that exchange active power while maintaining independence. Users are free to join or not, and to choose their electricity retailer. This paper considers the presence of multiple communities in the same distribution network (as allowed by regulation) and presents a model that independently optimize the operation of each community and manages network constraints. The price of the energy transactions between community members are determined as shadow prices of balancing constraints. Day-ahead scheduling results are presented for different community configurations and data sets from a real 15 kV distribution network. The paper analyzes the electricity procurement costs of both community members and non-members. The results show the effectiveness in reducing both energy procurement costs and noncompliance costs for each community. The sensitivity analysis on the number of ECs shows that as the number of ECs increases, cost reductions and penalties decrease, approaching the case without internal transactions within ECs
Kaposi-like manifestations in a newly diagnosed AIDS transgendered patient with silicone embolism syndrome and disseminated tuberculosis
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Indices of congested areas and contributions of customers to congestions in radial distribution networks
Full text linkCongestions are becoming a significant issue with an increasing number of occurrences in distribution networks due to the growing penetration of distributed generation and the expected development of electric mobility. Fair congestion management (CM) policies and prices require proper indices of congested areas and contributions of customer to congestions. This paper presents spatial and temporal indices for rapidly recognizing the seriousness of congestions from the perspectives of both magnitude violation and duration to prioritize the affected areas where CM procedures should be primarily activated. Besides, indices are presented which describe the contributions of customers to the congestions. Simulation tests on IEEE 123-bus and Australian 23-bus low-voltage distribution test feeders illustrate the calculation and capabilities of the proposed indices in balanced and unbalanced systems
Generic Dynamic Load Models in Long-Term Voltage Collapse Tme-Simulation
No full textThe aim of the paper is to examine up to which extent the so-called generic non-linear dynamic (GNLD) load models can replace more detailed models for representing loads, composed mostly by induction motors, both in short and in long-term voltage-collapse numerical simulations. After a review of the main characteristics of one GNLD model, namely the so called adaptive load model, a model refinement is proposed based on a more close reproduction of Q-V characteristics of induction motors. A power system often used in the literature is chosen as base case. In it, the two GNLD models have been introduced, in lieu of the residential and commercial load of such a system. For comparative purposes, contingency conditions leading the system to either short and long term voltage collapse are simulated
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Lightning interaction with medium-voltage overhead power distribution systems
No full textDistribution lines located in areas with high ground flash densities are prone to lightning-caused power interruptions. Lightning overvoltages can be produced on medium-voltage (MV) systems when lightning hits either the line conductors (direct strokes) or a point in the vicinity of the distribution network (indirect strokes). The evaluation of the lightning electromagnetic environment is essential to mitigate its effects and improve the power system quality. This chapter presents initially, using the concepts given in Chapter 5 of Volume 1, a procedure for the estimation of the mean annual number of direct lightning strikes to a given overhead distribution line. Then, the basic features of the lightning overvoltages are discussed. Although some typical characteristics can be identified, the analysis of the overvoltages depends on various parameters relevant to the adopted model of the lightning return stroke, soil and power network. The influences of the most important ones are discussed in this chapter, with examples of measured and calculated voltage waveshapes. Then, the main protective measures that can be applied to improve the lightning performance of MV distribution lines, namely the increase of the line insulation withstand capability, the use of periodically grounded shield wires and the installation of surge arresters along the line, are addressed. The analysis of the effectiveness of each measure as a function of the type of phenomenon (direct or indirect strikes) and of various parameters, such as the soil resistivity, ground resistance and grounding spacing, is performed. After that, the procedure presented in Chapter 1 of this volume for estimating the mean annual number of line flashovers that an overhead MV line can experience, is applied to the case of lines with different protective measures and the relevant performances are compared. The case of urban lines, whose performance is affected by the presence of buildings in their vicinity, is also dealt with, as well as the case of hybrid configurations, in which MV and high voltage (HV) lines share the same structures
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