Operation and planning of distribution networks with integration of renewable distributed generators considering uncertainties: a review

YesDistributed generators (DGs) are a reliable solution to supply economic and reliable electricity to customers. It is the last stage in delivery of electric power which can be defined as an electric power source connected directly to the distribution network or on the customer site. It is necessary to allocate DGs optimally (size, placement and the type) to obtain commercial, technical, environmental and regulatory advantages of power systems. In this context, a comprehensive literature review of uncertainty modeling methods used for modeling uncertain parameters related to renewable DGs as well as methodologies used for the planning and operation of DGs integration into distribution network.This work was supported in part by the SITARA project funded by the British Council and the Department for Business, Innovation and Skills, UK and in part by the University of Bradford, UK under the CCIP grant 66052/000000

Optimal operation of hybrid AC/DC microgrids under uncertainty of renewable energy resources : A comprehensive review

The hybrid AC/DC microgrids have become considerably popular as they are reliable, accessible and robust. They are utilized for solving environmental, economic, operational and power-related political issues. Having this increased necessity taken into consideration, this paper performs a comprehensive review of the fundamentals of hybrid AC/DC microgrids and describes their components. Mathematical models and valid comparisons among different renewable energy sources’ generations are discussed. Subsequently, various operational zones, control and optimization methods, power flow calculations in the presence of uncertainties related to renewable energy resources are reviewed.fi=vertaisarvioitu|en=peerReviewed

Smart grid

Tese de mestrado integrado em Engenharia da Energia e do Ambiente, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2016The SG concept arises from the fact that there is an increase in global energy consumption. One of the factors delaying an energetic paradigm change worldwide is the electric grids. Even though there is no specific definition for the SG concept there are several characteristics that describe it. Those features represent several advantages relating to reliability and efficiency. The most important one is the two way flow of energy and information between utilities and consumers. The infrastructures in standard grids and the SG can classified the same way but the second one has several components contributing for monitoring and management improvement. The SG’s management system allows peak reduction, using several techniques underlining many advantages like controlling costs and emissions. Furthermore, it presents a new concept called demand response that allows consumers to play an important role in the electric systems. This factor brings benefits for utilities, consumers and the whole grid but it increases problems in security and that is why the SG relies in a good protection system. There are many schemes and components to create it. The MG can be considered has an electric grid in small scale which can connect to the whole grid. To implement a MG it is necessary economic and technical studies. For that, software like HOMER can be used. However, the economic study can be complex because there are factors that are difficult to evaluate beyond energy selling. On top of that, there are legislation and incentive programs that should be considered. Two case studies prove that MG can be profitable. In the first study, recurring to HOMER, and a scenario with energy selling only, it was obtained a 106% reduction on production cost and 32% in emissions. The installer would have an $8 000 000 profit in the MG’s lifetime. In the second case, it was considered economic services related to peak load reduction, reliability, emission reduction and power quality. The DNO had a profit of$41,386, the MG owner had $29,319 profit and the consumers had a$196,125 profit. We can conclude that the MG with SG concepts can be profitable in many cases

Distribution System Planning and Reliability Assessment under High DG Penetration

With power system restructuring, continuous growth of demand, and deregulation, small, scattered generators referred to as Distributed Generation (DG) are predicted to play a key role in the power distribution system. Moreover, among the different types of DG units, it is widely accepted that renewable DG units are the key to a sustainable energy supply infrastructure, since they are both inexhaustible and non-polluting. However the intermittent nature and the uncertainties associated with the renewable resources create special technical and economical challenges that have to be comprehensively investigated in order to facilitate the deployment of these DG units in the distribution system. The objective of the work proposed in this thesis is to tackle some of the challenges associated with the increased penetration of renewable DG units into existing distribution systems. This includes the study of the impact of different renewable DG units on the supply adequacy of the distribution system, and the development of planning technique that optimally allocate renewable DG units into the distribution system. Furthermore, a methodology is proposed to check the feasibility of implementing energy storage system (ESS) into the distribution system to mitigate the problems associated with the high penetration of renewable DG units. These problems include the maximum reverse power flow limit, the equipment rating limit, and the voltage limit on each bus. The first step toward the accomplishment of this work is to model the random behaviour of the renewable resources (i.e. wind speed and solar irradiance). Here, different approaches are proposed to model the random behaviour of both wind speed and solar irradiance, either chronologically or probabilistically. Among those approaches are a novel technique of annual wind speed estimation based on a constrained Grey predictor, and a new implementation of the probability density function (pdf) of the clearness index so as to model solar irradiance using Monte Carlo Simulation (MCS). Supply adequacy of distribution systems is assessed based on well-being criteria during different modes of operation (i.e. grid-connected mode and islanding mode), using analytical and (MCS) techniques. During the grid-connected mode, from the load perspective, the substation transformers act as generating units. Therefore, supply adequacy of distribution systems is assessed by considering that the generating units of the distribution system are the substation transformers and the DG units. During the islanding mode of operation, the island is acting as a small autonomous power system (SAPS) and the most important issue during this mode of operation is to determine the probability of the island to be successful (the DG power output within the island matches the load) or a failure (there is a deficit in power generation). The focus of the model developed to optimally allocate the renewable DG units in existing distribution systems is to minimize annual energy losses and at the same time, avoid any violation of the system constraints under any operating condition. The methodology is based on generating a probabilistic generation-load model that combines all possible operating conditions of the renewable DG units with their probabilities, hence accommodating this model in a deterministic planning problem. The objective function of the planning formulation is to minimize annual energy losses; whereas the constraints include the voltage limits, the feeders’ capacity, the maximum penetration limit, and the discrete size of the available DG units. The objective of the methodology proposed for allocating an ESS into distribution systems with high penetration (greater than 20% of the feeder capacity) of renewable energy is to maximize the benefits for both the DG owner and the utility. This is done by sizing the ESS to accommodate the entire surplus of renewable energy, and then allocating it within the system in order to minimize the annual cost of the electricity

Distribution System Operators Observatory 2018

The distribution system is a key part of the electricity chain. It links bulk production with end consumers. Recently, radical changes have taken place in every segment of the power industry. These are calling for a changing role of the Distribution System Operators (DSOs) in Europe. This report provides a clear picture of the features of distribution grids in Europe, on the way they are operated and how far DSOs are from the paved provisions proposed in the recent Electricity Directive of the European Commission.JRC.C.3-Energy Security, Distribution and Market

City-Friendly Smart Network Technologies and Infrastructures: The Spanish Experience

Efficient, resilient, and sustainable electricity delivery is a key cornerstone in increasingly large and complex urban environments, where citizens expect to keep or rise their living standards. In this context, cost-effective and ubiquitous digital technologies are driving the transformation of existing electrical infrastructures into truly smart systems capable of better providing the services a low-carbon society is demanding. The goal of this paper is twofold: 1) to review the dramatically evolving landscape of power systems, from the old framework based on centralized generation and control, aimed at serving inelastic customers through alternating current (ac) transmission networks and one-way distribution feeders, to a new paradigm centered mainly around two main axes: renewable generation, both centralized and distributed, and active customers (prosumers), interacting with each other through hybrid ac/dc smart grids; 2) to illustrate, through featured success stories, how several smart grid concepts and technologies have been put into practice in Spain over the last few years to optimize the performance of urban electrical assets

Active congestion quantification and reliability improvement considering aging failure in modern distribution networks

The enormous concerns of climate change and traditional resource crises lead to the increased use of distributed generations (DGs) and electric vehicles (EVs) in distribution networks. This leads to significant challenges in maintaining safe and reliable network operations due to the complexity and uncertainties in active distribution networks, e.g., congestion and reliability problems. Effective congestion management (CM) policies require appropriate indices to quantify the seriousness and customer contributions to congested areas. Developing an accurate model to identify the residual life of aged equipment is also essential in long-term CM procedures. The assessment of network reliability and equipment end-of-life failure also plays a critical role in network planning and regulation. The main contributions of this thesis include a) outlining the specific characteristics of congestion events and introducing the typical metrics to assess the effectiveness of CM approaches; b) proposing spatial, temporal and aggregate indices for rapidly recognizing the seriousness of congestion in terms of thermal and voltage violations, and proposing indices for quantifying the customer contributions to congested areas; c) proposing an improved method to estimate the end-of-life failure probabilities of transformers and cables lines taking real-time relative aging speed and loss-of-life into consideration; d) quantifying the impact of different levels of EV penetration on the network reliability considering end-of-life failure on equipment and post-fault network reconfiguration; and e) proposing an EV smart charging optimization model to improve network reliability and reduce the cost of customers and power utilities. Simulation results illustrate the feasibility of the proposed indices in rapidly recognizing the congestion level, geographic location, and customer contributions in balanced and unbalanced systems. Voltage congestion can be significantly relieved by network reconfiguration and the utilization of the proposed indices by utility operators in CM procedures is also explained. The numerical studies also verify that the improved Arrhenius-Weibull can better indicate the aging process and demonstrate the superior accuracy of the proposed method in identifying residual lives and end-of-life failure probabilities of transformers and conductors. The integration of EV has a great impact on equipment aging failure probability and loss-of-life, thus resulting in lower network reliability and higher cost for managing aging failure. Finally, the proposed piecewise linear optimization model of the EV smart charging framework can significantly improve network reliability by 90% and reduce the total cost by 83.8% for customers and power utilities

Design and Engineering for Smart Secondary Substation Automation Panel

This M.Sc. thesis presents a systematic approach to enhance automation at the electrical distribution level by introducing multiple retrofit approaches in existing secondary substations. This study has explored insights into providing intelligence to the secondary substation efficiently in terms of dimensions, cost and communication needs. The designing of a retrofit product has been accomplished taking into consideration the current network status, the present need and the future compatibility for Smart Grid. Although, the new device has been designed based on the Finnish network need, it is fully compatible with electrical networks worldwide. Initially a comprehensive review of the theory and literature related to present network configuration, distribution automation, Smart Grids and all relevant areas was conducted. This was followed by a review of the reports of transmission and distribution networks operators in Finland and product brochures from various manufacturers in order to create a framework. This was complemented and further verified by the primary collection of data in the form of interviews and discussions with representatives from these companies. Based on all this information, the operation within the network was emulated and the final product was designed. The product provides practical capabilities from the basic monitoring to the full automated control with decision making capabilities locally or remotely through the network control centre via SCADA. Being customizable and retrofit installation, its adaptability and scalability is based on the specific network need. Besides, as the product has been developed in the form a detailed research through collaboration with university researchers, product manufacturers as well as network operators, it is practically designed and is planned to be implemented soon. Although, there are other similar but less effective and less flexible products available, they lose advantage when it comes to compatibility. The research represents one of the first attempts to design a customizable product for the medium voltage level network automation and the retrofit approach with its modular and scalable feature provides originality to it

An Economic and Institutional Analysis of Maize Research in Kenya

Maize, the most important food crop in Kenya, contributes 44 percent of the per-capita, calorie intake. Increases in maize production over the past three decades have been attributed to the availability and adoption of modern maize techniques, especially fertilizer and hybrid seed. This paper estimates the rate of return to maize research to be 53 to 61 percent, and reveals that his impact was aided by complementary agricultural extension and seed multiplication and distribution programs. The paper describes the institutional framework that may have led to one of Kenya’s agricultural research success stories. It also poses challenges to the future of maize production in Kenya.food security, food policy, maize, Crop Production/Industries, Research and Development/Tech Change/Emerging Technologies, Downloads July 2008 - July 2009: 19, O18,