The total energy demand in the world is expected to increase in the future years due to thehigh development rate of developing countries. Access to energy enables development, butthe current global energy mix has to be modified if a sustainable growth is desired. Renewableenergy sources (RES) benefit from both a political and economic support from manygovernments and international entities. The growing installation of RES takes place both inlarge scale, as wind farms with sizes 10 – 1000 MW, and in small scale in homes or smallenterprises with sizes 100 W – 100 kW. Small scale wind power connected to the grid is rarenowadays except in the case of remote mini-grids. By contrast, small scale solar photovoltaic(PV) power is being more and more commonly installed, especially in the form of investorownedroof-installed units. Taking increasing small scale solar and wind power into accountin network planning is a challenge faced by the distribution system operator (DSO).The aim of this thesis is to present a guideline that assists DSOs when planning lowvoltage (LV) distribution networks (DN) with a large amount of small scale distributedgeneration (DG) on a short-term perspective. A review on integration issues of DG isperformed and over-voltage constraints are identified as the most relevant issue. Simple ruleshave already been designed for individual DG units, as the one presented in the AMKhandbookpublished by Svensk Energi; but these are not valid any more when consideringmore than one DG unit. The new proposed guideline employs the AMK-handbook as astarting point and develops it further by including the interaction between DG units. Theguideline is then applicable to scenarios with more than one DG unit. The maximum capacityof a new DG unit applying for a connection to a grid is calculated based on the location andcapacity of the already installed DG units, and without any reinforcement. The proposedguideline can be applied under no load and minimum load condition.Since this thesis is a collaboration project between KTH-Royal Institute of Technologyand Vattenfall R&D, two specific Swedish LV distribution networks owned by VattenfallEldistribution AB are studied. Scenarios with different penetration levels of DG, with valuesbetween 12% and 71%, and capacity of individual DG units below 43.5 kW are analyzed.Evaluation of the results shows that the proposed guideline leads to acceptable results. Thedevelopment of future simple guidelines is suggested to be based on the following twoaspects: absolute and relative location of the DG units; and a correct identification of the weakbus. Relative location reveals the interaction with other DG units within the DN. Moreover, itis stated that the use of the penetration level as a planning measure, based on the total DGcapacity, has a limited application.

There has been a large body of statements claiming that the large scale deployment of Distributed Energy Resources (DERs) will eventually reshape the future distribution grid operation in numerous ways. However, there is a lack of evidence specifying to what extent the power system operation will be alternated. In this project, quantitative results in terms of how the future distribution grid will be changed by the deployment of distributed generation, active demand and electric vehicles, are presented. The quantitative analysis is based on the conditions for both a radial and a meshed distribution network. The input parameters are on the basis of the current and envisioned DER deployment scenarios proposed for Sweden. The simulation results indicate that the deployment of DERs can significantly reduce the power losses and voltage drops by compensating power from the local energy resources, and limiting the power transmitted from the external grid. However, it is notable that the opposite results (e.g., severe voltage uctuations, larger power losses) can be obtained due to the intermittent characteristics of DERs and the irrational management of different types of DERs in the DNs. Subsequently, this will lead to challenges for the Distribution System Operator (DSO).

The rise of disruptive technologies and the rapid growth of innovative initiatives have led to a trend of decentralization, deregulation, and distribution of regulated/centralized services. As a result, there is an increasing number of requests for the connection of distributed generators to distribution networks and the need for power utilities to quickly assess the impacts of distributed generators (DGs) to keep up with these requests. Grid integration of DGs brings about protection issues. Current protection systems were not designed for bi-directional power flow, thus the protective devices in the network lose their ability to perform their main functions. To mitigate the impact of distributed generation (DG), some standards and policies constrain the number of DG that can be connected to the distribution network. The problem with these limits is that they are based only on overload and overvoltage, and do not adequately define the DG size/threshold before the occurrence of a protection issue (NRS 097-2-3). The other problem with distributed generation is the vast difference in the technology, location, size, connection sequence, and protection scheme requirements which results in future DG network planning inadequacies – The Network DG Planning Dilemma. To determine the amount of DG to connect to the network, a detailed analysis is required which often involves the use of a simulation tool such as DIgSILENT to model the entire network and perform load flow studies. Modelling networks on DIgSILENT is relatively easy for simple networks but becomes time-consuming for complex, large, and real networks. This brings about a limitation to this method, planning inadequacies, and longer connection approval periods. Thus, there is a need for a fast but accurate system-wide tool that can assess the amount of DG that can be connected to a network. This research aims to present a technique used for calculating protection-based DG penetration limits on MV networks and develop a model to determine medium voltage opportunity network maps. These maps indicate the maximum amount of DG that can be connected to a network without the need for major protection scheme changes in South Africa. The approach to determining protection-based penetration limits is based on supervised machine learning methods. The aim is to rely on protection features present in the distribution network data i.e. fault level, Inverse Definite Minimum Time (IDMT) curve, pick-up current settings, Time Multiplier Settings (TMS), calculated relay operating times and relay positions to see how the network responds at certain DG penetration levels (‘actual' relay operating times). The dataset represents carefully anonymized distribution networks with accepted protection philosophy applied. A supervised machine learning algorithm is applied after nontrivial data pre-processing through recommendation systems and shuffling. The planning dilemma is cast into three parts: the first part is an automated pattern classification (logistic regression for classification of protection miscoordination), the second part involves regression (predicting operating time after different levels of DG penetration), and the last part involves developing a recommendation system (where, when and how much photovoltaic (PV) DG will be connected). Gradient descent, which is an optimisation algorithm that iterates and finds optimal values of the parameters that correspond to the local or global minimum values of the cost function using calculus was used to measure the accuracy of each model's hypothesis function. The cost function (one half mean squared error) for the models that predict ‘actual' relay operating times before DG penetration, at 35%, 65%, and 75% DG penetration converged to values below 120, 20, 15, and 15 seconds2 , respectively, within the first 100 iterations. A high variance problem was observed (cross-validation error was high and training error was low) for the models that used all the network protection features as inputs. The cross-validation and training errors approached the desired performance of 0.3±0.1 for the models that had second-order polynomials added. A training accuracy of 91.30%, 73.91%, 82.61%, and a validation accuracy of 100%, 55.56%, 66.67% was achieved when classifying loss of coordination, loss of grading and desensitization, respectively. A high bias problem was observed (cross-validation error was high and training error was high) for the loss of grading classification (relay positions eliminated) model. When the models (horizontal network features) were applied to four MV distribution networks, loss of coordination was not predicted, the loss of grading model had one false positive and the de-sensitization model had one false negative. However, when the results were compared to the vertical analysis (comparing the operating times of upstream and downstream relays/reclosers), 28 points indicated a loss of coordination (2 at 35%, 1 at 65% and 25 at 75% DG penetration). Protection coordination reinforcements (against loss of grading and desensitization) were found to be a requirement for DG connections where the MV transformer circuit breaker TMS is between 0.5 and 1.1, and where the network fault level is between 650 and 800A. Distribution networks in affluent neighbourhoods similar to those around the Western CapeSomerset West area and Gauteng- Centurion area need to be reinforced to accommodate maximum DG penetration up to the limit of 75% of the After Diversity Maximum Demand (ADMD). For future work, the collection of more data points (results from detailed analytical studies on the impact of DG on MV feeders) to use as training data to solve the observed high variance problem is recommended. Also, modifying the model by adding upstream and downstream network features as inputs in the classification model to solve the high bias problem is recommended.

Pour maintenir la tension dans des bornes admissibles, des régulations locales de puissance réactive (Q) en fonction de la tension (U) sont envisagées sur les réseaux de distribution. Ces travaux étudient l’impact de ces régulations sur la stabilité des réseaux de distribution accueillant de la production. Une étude empirique confirme le risque d’instabilité de la tension et souligne le lien avec les paramètres de la régulation. Pour aider les gestionnaires à les choisir, trois méthodes d’étude de la stabilité sont proposées. Tout d’abord, une méthode formelle fondée sur les notions d’abstraction discrète et de bisimulation est développée. Elle offre une grande précision au prix d’un effort de calcul important. Pour contournercette difficulté, un critère analytique portant sur le temps de réponse des régulations Q(U) est formulé. Ensuite, un critère valable dans tous les cas est proposé pour les codes de réseaux. Enfin, l’extension desméthodes à des cas plus complexes est discutée. / To maintain the voltage within specified limits, local control laws of distributed generators (DGs) reactive power (Q) with respect to their voltage (U) have been considered. This work studies the impact of Q(U) control laws on distribution feeders’voltage stability. An empirical study confirms the risk of voltage instability and highlights its dependence on control law parameters. To help distribution grid operators to choose these parameters, three methods assessing stability are formulated.First, a formal method based on discrete abstraction and bisimulation calculation is developed. The proposed approach yields precise results but with a high computational load. Then, to overcome this issue, an analytical criterion adapting Q(U) control laws response time with respect to grid parameters is formulated. Finally, a general criterion, valid in any cases, is established in order to be included in the grid codes. To conclude this work, extension to more complex cases is discussed.

Decarbonisation of different energy sectors of society is becoming a pressing issue globally withnumerous legislations and objectives being set to decarbonise electrical grids worldwide. Somehave already been met; however, islanded grids still heavily rely on fossil fuels to meet their electrical demand due to the weakness of their grid and limited available space forcing them to use space-efficient technologies such as diesel generators. This is the case of Fuerteventura in the Canary Islands (Spain) which produces 80-90% of its electricity from fossil fuels. This study will analyse the feasibility of decarbonising the electrical grid of Fuerteventura using a decentralised grid system with wind, solar, and battery storage to achieve 100% renewable generation. To select the best hybrid energy system for the case study, a 9-step methodology has been presented and followed in which both descriptive (qualitative) and quantitative data have been used to provide the background knowledge of the study and the inputs for the analysis which is done using the microgrids optimisation model HOMER. The analysis aims to understand the grid and renewable resources on the island to later develop the different scenarios to be reviewed. The three different scenarios, wind-battery, solar-battery, and wind-solar-battery were modelled and simulated using the latest HOMER software. Results showed reduced LCOE and capital costs in the wind-solar-battery scenario compared to the wind-battery and solar-battery scenarios due to increased use of wind and lower capacity of installed batteries needed. Space availability was shown to be a problem for the scenarios using wind as the turbines would occupy 5% of the islands surface. Environmental and visual impacts would also be noticeable under the wind-battery and wind-solar-battery scenarios as the entire island is a Biosphere Nature Reserve and is a well-known touristic destination for natural virgin beaches. Additionally, the results showed that all 3 scenarios had excess electricity values above 50% of the total electrical production and still experienced some capacity shortages. To solve this, diversification of the generation and storage facilities, implementation of DSM (Demand side management) and V2G (Vehicle-to-grid), and interconnection of the islands is proposed with the latter being the most realistic solution. The study concludes the wind-solar-battery is the most technological and economically feasible solution although several issues need to be addressed for a similar project to be implemented on a real island.

[pt] A Geração Distribuída (GD) tem modificado profundamente a estrutura clássica dos sistemas elétricos. No Brasil, o modelo tarifário adotado pela regulação atual, denominado Sistema de Compensação de Energia, estabelece que a energia injetada pela GD na rede da distribuidora desconta integralmente a energia consumida, com todas suas componentes tarifárias. Em voga, a discussão para novas regras a respeito das formas de remuneração e valoração da GD envolve por um lado as distribuidoras, que alegam que o atual mecanismo de compensação não remunera adequadamente o uso do sistema de distribuição e, por outro lado, consumidores que optam pela GD, pontuam seus benefícios à sociedade e defendem o atual modelo. Neste sentido, é proposta nesta tese de doutorado uma nova metodologia de quantificação e alocação de benefícios e custos da GD em sistemas de distribuição, que gere um sinal tarifário capaz de traduzir os efeitos da sua localização e presença na rede. A concepção básica abrange a identificação, contabilidade e partilha do que são denominadas na metodologia proposta como funções, que representam características tarifáveis e consideradas adequadas na averiguação da remuneração da GD. Neste trabalho, as funções que serão avaliadas representam o impacto da GD no uso, nas perdas, no pico de carga e na confiabilidade da rede de distribuição. A alocação entre os geradores é realizada utilizando-se o Valor Shapley da Teoria de Jogos Cooperativos. Para aplicação da metodologia proposta, dois sistemas testes e um sistema real de distribuição são utilizados e os resultados obtidos são amplamente discutidos. / [en] Distributed Generation (DG) has deeply changed the classical structure of electrical power systems. In Brazil, the tariff model adopted by the current regulation, called the Energy Compensation System, establishes that the energy injected by DG into the distribution grid fully discounts the energy consumed, with all its tariff components. In vogue, the discussion for new rules regarding the forms of remuneration and valuation of DG involves, on the one hand, distributors, who claim that the current compensation mechanism does not adequately remunerate the use of the distribution system, and, on the other hand, consumers who choose for DG, point out its benefits to society and defend the current model. In this sense, this doctoral thesis proposes a new method for quantifying and allocating DG benefits and costs in distribution systems, which generates a tariff signal capable of translating the effects of its location and presence in the network. The basic concept covers the identification, accounting and sharing of what are called in the proposed method as functions, which represent chargeable characteristics and considered adequate in the study of DG remuneration. In this work, the functions that will be evaluated represent the DG impact on the usage, losses, peak load and reliability of the distribution network. The allocation between generators is performed using the Shapley Value of Cooperative Game Theory. In order to apply the proposed method, two test systems and a real distribution system are used and the obtained results are widely discussed.

No description available.

As human society develops, there is an increasing demand for electricity. However, the reserves of fossil fuels on earth are limited and may run out in the foreseeable future. Therefore, the possibility of replacing traditional fossil fuels with renewable energy sources is widely being investigated to resolve the world-faced energy shortage and environmental problems. The first method is to utilize more renewable energy such as wind and solar power and increase the percentage of distributed generation. Another method is to popularize electric vehicles due to their environmental-friendly and energy-saving characteristics. However, the integration of distributed generation and electric vehicles may greatly influence the operation and planning of power systems in several ways. This might result in deterioration of power system reliability. Since the society development highly depends on a safe and reliable power grid, it is essential to ensure high reliability of power systems when integrated with renewable energy resources. This master thesis aims to investigate the reliability performance of power distribution systems after integrating distributed generation and electric vehicles. First, the probabilistic model of distributed generation and electric vehicles for various scenarios are simulated. After that, a set of reliability analyses based on a standard reliability test system are carried out, in which a sequential Monte-Carlo simulation method is adopted to estimate average reliability indices. The overall conclusion is that the integration of distributed generation enhances power system reliability performance through supplying power to nearby customers in island mode. For electric vehicles, the proper regulation of charging behavior can help reduce the deterioration of power system reliability to the most extent, and the Vehicle-to-Grid mode can also improve system reliability. Furthermore, the electric bus dynamic charging mode has no additional harm to power system reliability performance than non-dynamic charging and has a promising prospect. / När det mänskliga samhället utvecklas finns det en ökande efterfrågan på el. Reserverna av fossila bränslen på jorden är dock begränsade och kan ta slut inom en överskådlig framtid. Därför undersöks möjligheten att ersätta traditionella fossila bränslen med förnybara energikällor för att lösa den världsomspända energibristen och miljöproblemen. Den första metoden är att använda mer förnybar energi såsom vind- och solenergi och öka andelen distribuerad produktion. En annan metod är att popularisera elfordon på grund av deras miljövänliga och energibesparande egenskaper. Integrationen av distribuerad produktion och elfordon kan dock påverka sätt och planering av kraftsystem i hög grad på flera sätt. Detta kan leda till försämring av elsystemets tillförlitlighet. Eftersom samhällsutvecklingen i hög grad beror på ett säkert och tillförlitligt kraftnät är det viktigt att säkerställa hög tillförlitlighet hos kraftsystem när de är integrerade med förnybara energikällor. Syftet med detta examensarbete är att undersöka tillförlitligheten hos kraftdistributionssystemet efter integrering av distribuerad generation och elfordon. För det första konstrueras den probabilistiska modellen för distribuerad generation och elfordon inklusive olika scenarier. Därefter genomförs en uppsättning tillförlitlighetsanalys baserad på RBTS buss 6-system, där sekventiell Monte-Carlo-simuleringsmetod antas för att uppskatta genomsnittliga återansvarsindex. Den övergripande slutsatsen är att integreringen av distribuerad produktion förbättrar systemets tillförlitlighet genom att leverera kraft till närliggande kunder på öns plats. För elektriska fordon kan korrekt reglering av laddningsbeteendet bidra till att minska försämringen av elsystemets tillförlitlighet i största möjliga utsträckning, och läget Fordon till nät kan även förbättra systemets tillförlitlighet. Dessutom har det elektriska bussens dynamiska laddningsläge ingen ytterligare skada på kraftsystemets tillförlitlighet och har ett lovande perspektiv.

Within the past decade, talk has arisen of shifting the utility grid from centralized, radial sources to a distributed network of sources, also known as distributed generation (DG); in the wake of deregulation, the California energy crisis, and northeastern blackouts. Existing control techniques for DG systems are designed to operate a system either in the connected or disconnected (islanding) mode to the utility; thus not allowing for both modes to be implemented and transitioned between. Existing detection and re-closure algorithms can also be improved upon. Dependent upon the method implemented, detection algorithms can either cause distortions in the output or completely miss a disturbance. The present re-closure process to reconnect to the utility is to completely shutdown and wait five minutes. The proposed methods of this study improve upon existing methods, via simulation and hardware experimentation, for DG systems that can intentionally islanding themselves. The proposed, "switched-mode", control allows for continuous operation of the system during disturbances by transitioning the mode of control to reflect the change in the system mode (grid-connected or islanding). This allows for zero downtimes without detrimental transients. The proposed detection method can sense disturbances that other methods cannot; and within 25 ms (approximately 1.5 line-cycles at 60 Hz). This method is an improvement over other methods because it eliminates the need to purposely distort the outputs to sense a disturbance. The proposed re-closure method is an improvement over the existing method due to the fact that it does not require the system to de-energize before re-synchronizing and reconnecting to the utility. This allows for DGs to continuously supply power to the system without having to shut down. Results show that the system is generally ready to reconnect after 2 to 5 line cycles. / Master of Science

The content of this Master´s Thesis is creating of dynamic models of distributed energy sources in PSCAD and their validation in chosen operation regimes. In the introduction of this thesis is summarized theoretical knowledge about methods for power systems analysis and there is a comparison of static and dynamic methods for power systems analysis. Static methods are used to calculate electric variables in grid nodes. In compare with them, dynamic methods are used to study instantaneous electrical and mechanical variables not only in grid nodes, but also at components of power system. Secondly, we individually designed distributed energy sources in according to requirements, we made a topology of distribution grid and we integrated these energy sources to the distribution grid. Finally, we chose some operation regimes, and studied a behavior of energy sources during these operation regimes.