Reference Network Models Research Articles

Formulation of reference network models for the Hungarian medium voltage distribution level

In the next two decades, a rapidly increasing photovoltaic penetration connected to the distribution electricity network is expected both nationally and internationally, which influences grid operation. Simultaneously, an essential development of network infrastructure is also expected. In order to determine development directions and opportunities, power system simulation is essential, which is based on the generation of representative feeders. In this paper, by clustering (using k-means clustering) medium voltage distribution feeders, valid Hungarian representative networks are formulated and described. The number of descriptive variables was reduced by, principal component analysis. The feeders are described with the first three principal components (95% coverage of the information). The optimal number of clusters was determined using four different validity criteria, and set to 6. The contributions of the paper are that the examined feeders are characterized by both electrical (physical) and mathematical parameters, in a new combination, from which the number of switches is a novel element in the literature. The applied principal component analysis works with more components (3) and greater coverage (95%) than the methods available in the examined literature. Based on topographic verification of the representative networks, the clusters are well characterized by the parameters of the feeders.

Cost–benefit analysis of battery storage in medium‐voltage distribution networks

The increasing deployment of non-dispatchable generation in electric systems where generation and demand must be balanced at all times has led to a renewed interest in technologies for energy storage. This study presents a cost–benefit analysis of energy storage for peak demand reduction in medium-voltage distribution networks. In particular, the installation of batteries in secondary substations is studied for three realistic large-scale networks representing urban, semi-urban and rural distribution areas. On the one hand, savings in energy costs derived from storing energy at low-priced hours and selling it at peak hours are considered. On the other hand, savings in network reinforcement due to the peak shaving are evaluated. Network reinforcement requirements are assessed using reference network models, large-scale network-planning tools often used by distribution regulators to establish the allowed distribution costs. Additionally, sensitivity to different demand growth ratios and battery capacities is analysed. The final objective is to determine the target cost for batteries to be profitable from the point of view of distribution. Results show that significant savings can be obtained, especially in urban and semi-urban areas.

Reference Network Development Concept for the Malaysian Power Distribution System

Distribution system planning involves a set of complex analysis as the amount of data and associated parameters needed for the analysis are huge. Simplified reference network models (or a generic representative network) would help to reduce the amount of data to be handled, and thereby simplify the complexities of analysis. Depending on the parameters used, reference network models could be applied to assess the technical and economic performance of a network, such as, investment consequences against impact of customer end tariff pricing. The inherent idea is to develop a generic reference models that would help to visualize the impact of different planning parameters, such as adequacy, reliability, and quality against cost. These models have the potential capability for flexible usage on fast developing networks. This paper discusses an indigenous conceptual development of a reference network based on the Malaysian distribution system

Large-Scale MV/LV Transformer Substation Planning Considering Network Costs and Flexible Area Decomposition

In the context of incentive regulation applied to electricity distribution companies, reference network models (RNMs) can be a valuable tool to estimate their efficient costs. These models have to plan large-scale electricity distribution areas with different voltage levels. This paper describes the planning algorithms proposed to optimize the location, size, and supply area of the medium-voltage/low-voltage transformer substations in an RNM that has to plan a network from scratch (Greenfield planning). The presented methodology aims to divide the entire planning area into small zones with a nonpredetermined area so that each one can be optimized separately. Then, a heuristic process based on k-means algorithm seeks to find the set of clusters that minimize the cost function, considering the cost of the transformer substations, as well as the LV and MV network costs. The presented case studies show the benefits of applying the proposed methodology.

Distribution network costs under different penetration levels of distributed generation

AbstractNowadays, the amount of distributed generation (DG) connected to distribution networks is increasing significantly. In a European context, one of the main drivers for this growth is the support of electricity generation from renewable energy sources (RES) and combined heat and power (CHP) plants. Hence, these DG units mostly consist of non‐controllable generation. Distribution is a regulated activity which is, at least, legally and functionally unbundled from the generation activity. These issues, together with the fact that distribution networks were not originally designed to accommodate generation, pose significant challenges on distribution network planning and operation. One of the major concerns of distribution system operators (DSOs) is the impact that large penetration levels of DG may have on distribution network costs. This paper presents a quantification of the impact of DG on distribution network costs in three real distribution areas. Different scenarios of demand and generation have been analysed for each region. Two possible situations are taken into account in each scenario: maximum net demand and maximum net generation. The computation of the distribution network costs was carried out by means of two large‐scale distribution planning models called reference network models (RNMs). Copyright © 2010 John Wiley & Sons, Ltd.

Ecological network analyses and their use for establishing reference domain in functional assessment of an estuary

We developed a framework to use ecological network analysis for functional assessment of large aquatic ecosystems in the context of ecosystem-based management. We established a reference domain for the Neuse River Estuary, North Carolina, USA, from changes over time. Four reference network models of the trophic structure of the estuary during early and late summers of 1997 and 1998 were constructed and analyzed. The estuary has experienced various symptoms of eutrophication during the past 20 years, including summer-time hypoxia and fish kills. The networks were used to quantify indices of nominal trophic dynamics and their variation. The ratio of biomass of nekton to that of macrobenthos, derived from network construction, was used to index severity of eutrophication and to promote accessibility of ecological network analysis to environmental management. The ratio increased from early to late summer, and network metrics demonstrated a variety of responses in association with that change. Some variables from network analysis, especially related to consumers, reflected some but not all of this change. Others reflected the most severe increase in the ratio in late summer 1997 when hypoxia was most extensive. We evaluated uncertainty and the modulating effects of hierarchy by comparing variation of input biomasses with integrative response variables. Relative variation in input variables was generally greater than that of the integrative response variables as predicted by hierarchy theory. Ecological network analysis has previously served as support for ecosystem-based management of large aquatic systems with some success. However, its use can be enhanced by making it more accessible to environmental managers and policy makers. Ways to do this include promoting simple metrics from network construction and explicitly associating network analysis to concepts familiar to the management community, such as functional assessment and reference.