Submitted by Morgana Silva (morgana_linhares@yahoo.com.br) on 2016-09-27T17:05:15Z No. of bitstreams: 1 arquivototal.pdf: 2911484 bytes, checksum: a40eec3093de5890811339c6b3e86fa7 (MD5) / Made available in DSpace on 2016-09-27T17:05:15Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2911484 bytes, checksum: a40eec3093de5890811339c6b3e86fa7 (MD5) Previous issue date: 2016-02-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This work presents a method of sizing photovoltaic panels using modified Particle swarm (MPSO) in order to reduce power losses and improve the voltage profile. For implementation was used the PowerFactory® software, specifically programing language DIgSILENT (DPL). The proposed method was applied at the first time in the IEEE 13-bus system. After validating, it was applied to a real system, Federal University of Paraíba (UFPB). The results show that the proposed method have the ability to provide the best dimensions of photovoltaic panels distributed at the University, improving of the voltage profile and reducing energy losses / Este trabalho apresenta um método de dimensionamento de painéis fotovoltaicos usando enxame de partículas modificado (MPSO), a fim de reduzir as perdas de energia e melhorar o perfil de tensão. Para a implementação é utilizado o software PowerFactory®, especificamente a linguagem de programação em DIgSILENT (DPL). O método proposto foi aplicado inicialmente no sistema IEEE 13-barras. Após a validação, foi aplicada a um sistema real, Universidade Federal da Paraíba (UFPB). Os resultados mostram que o método proposto tem a capacidade de proporcionar as melhores dimensões de módulos fotovoltaicos distribuídos na micro rede da Universidade, melhorando o perfil de tensão e reduzindo as perdas de energia.

The purpose of this study is to analyse how a battery energy storage system (BESS) can support the frequency and voltage stability for an islanded microgrid containing a hydropower plant. Two different microgrids, both situated in Sweden, are evaluated. Modelling and dynamic simulations are conducted in the PowerFactory tool. The result shows that both the frequency and the voltage control can be improved with the BESS. However, with the allowed limit of ± 1 Hz, not all simulated scenarios including a BESS meets the requirement. A large difference between the BESS and generator capacity might be a possible cause for this. By dividing the larger loads so that smaller loads are attained, the frequency deviation might be reduced. Furthermore, by adjusting the systems PID-parameters according to the island mode operation, faster regulation can be attained. The system operates according to the Master slave control strategy, with the hydropower being the master unit with voltage control and the BESS being a slave unit with PQ control. The ability to operate an islanded microgrid can ensure the supply of electricity to inhabitants and vital functions in society. By utilizing a BESS for increasing electric stability, emission of CO2 is indirectly mitigated. As cost for BESS are expected to decrease rapidly, they will be accessible for utilization all over the world.

Due to increasing penetration of decentralized variable renewable energy generators and the increasing demand of electrical power due to the electrification of the heat and transport sectors, low voltage grids are facing critical problems. Deviation of the permitted voltage range and local overloads of the grid equipment, are the two main issues that are compromising a smooth distribution grid operation. An intelligent integration of distributed generators, heat-pumps and electric vehicles into a Smart Grid, allows the flexibility that they intrinsically provide, to be used by distribution system operators to avoid critical grid conditions. Smart grid suppliers currently available on the market, have been categorized into Local, Decentralized and Centralized Smart Grid Concepts. Their main difference is represented by the level of control, communication and coordination that they make use of. The aim of the thesis was to evaluate the effectiveness of solution of the Smart Grid Concepts implementation in specific low voltage grids, especially in term of voltages and loadings mitigation capabilities, to be used as a decision making tool for future smart grid implementations. A control architecture that emulates the way the analyzed Smart Grid Concepts operate, has been implemented in Python and tested on three different low voltage distribution networks in DigSILENT PowerFactory. The control architecture is an algorithm that communicates to DigSILENT PowerFactory how the Smart Grid needs to operate in response to detected critical grid conditions. The flexibility that the Smart Grid Concepts make use of, are battery storage, active power curtailment and reactive power compensation from photovoltaic inverters and demand side management by means of electric vehicles and heat pumps. In particular, in order to make most use of the available flexibility, an intelligent electric vehicles charging strategy has been implemented as well as an intelligent heat pump operation. Both static worst-case simulations and time-dependent simulations, over a winter and a summer day, for different penetration scenarios, have been carried out. The summary of the simulation results showed that while the Decentralized Smart Grid Concept, if the flexibility is available, is always able to keep voltages and loadings between their critical values, the Local Smart Grid Concept is not able to do the same for the loadings. / På grund av ökad penetration av decentraliserade variabla förnybara energikällor och den ökande efterfrågan på elkraft på grund av elektrifiering av värme- och transportsektorn, står lågspänningsnätet inför kritiska problem. Avvikelse av det tillåtna spänningsområdet och lokala överbelastningar av nätutrustningen är de två huvudproblemen som äventyrar en smidig nätdrift. En intelligent integration av distribuerade generatorer, värmepumpar och elektriska fordon i ett smart nät, tillåter flexibiliteten som de egentligen tillhandahåller, för att undvika kritiska rutnätförhållanden. Smartnätleverantörer som för närvarande är tillgängliga på marknaden har system som kategoriserats som lokalt, decentraliserat och centralt Smart Grid Concepts. Deras huvudsakliga skillnad representeras av den nivå av kontroll, kommunikation och samordning som de utnyttjar. Syftet med avhandlingen var att utvärdera effektiviteten av lösningen av implementeringen av Smart Grid Concepts i specifika lågspänningsnät, särskilt när det gäller spänningar och belastningsreducerande förmågor, som ska användas som beslutsverktyg för framtida smarta nätverksimplementeringar. En reglerarkitektur som emulerar hur ett analyserat Smart Grid Concepts fungerar, har implementerats i Python och testats på tre olika lågspänningsdistributionsnä i DigSILENT PowerFactory. Kontrollarkitekturen är en algoritm som kommunicerar med DigSILENT PowerFactory hur Smart Grid bör fungera som svar på detekterade kritiska gridförhållanden. Den flexibilitet som Smart Grid Concepts använder sig av är batterilagring, aktiv strömavbrott och reaktiv effektkompensation från fotovoltaiska omvandlare och efterfrågesidan hantering med elbilar och värmepumpar. I synnerhet för att på bästa sätt utnyttja den tillgängliga flexibiliteten har en intelligent laddningsstrategi för elfordon implementerats liksom en intelligent värmepumpsoperation. Både statiska wärsta fall simuleringar och tidsberoende simuleringar, över en vinter och en sommardag, för olika penetrationsscenarier har utförts. Sammanfattningen av simuleringsresultaten visade att medan det decentraliserade Smart Grid Conceptet, om flexibiliteten är tillgänglig, alltid kan hålla spänningar och belastningar mellan sina kritiska värden, kan det lokala Smart Grid Concepts inte göra samma för belastningarna.

This research argues that a diesel-based isolated electrical system can be optimized byintegrating a high share of solar photovoltaic (PV) generation and that the frequencystability of such system can be improved by including the PV participation in frequencyregulation. A case study is developed in order to explore an island’s expansion of theinstalled generating capacity and its optimization. This study uses the tool HOMER tosolve the optimization problem and PowerFactory to verify the frequency stability of theproposed system. The PV integration allows for a reduction of diesel fuel consumption,emissions and generation costs. Additionally, in high PV penetration scenarios, the reducedinertia in such systems can lead to high frequency deviations that may trip the systemprotection. The study demonstrates that the instantaneous frequency deviation after a loadand generation imbalance can be reduced by designing the PVs to operate with an allocatedreserve and a decentralized time-based secondary frequency control. The frequency stabilitywas achieved after different disturbance scenarios under high PV penetration and reducedavailable inertia, indicating that high PV integration is economically and technically feasiblein small island grids. / I detta examensarbete studeras hur ett dieselbaserat och isolerat elsystem kan optimeras genom att integrera en hög andel solceller (PV) i elproduktionen och att frekvensstabilitet kan förbättras när PV användas i regleringen. En fallstudie har utvecklats under denna forskning för att analysera en ökning av den installerade generationskapacitet vid en ö samt hur detta kan optimeras. I denna studie användas verktyget HOMER för modeloptimering och PowerFactory för att testa den optimerade systemfrekvens stabilitet. Med PV generation kan diesel konsumption, utsläpp och kostnader minskas för hela systemet. En hög andel PV i generationen reducerar elsystemet totala svängmassa vilket kan ledda till avvikelser i systemfrekvensen som kan ursaka att skyddsystem aktiveras. Studien demonstrerar att den momentana systemavvikelsen efter en obalans kan reduceras genom att designa PV i systemet med en allokerad reserv och en decentraliserad och tidsbaserad sekundär frekvensreglering. Frekvensstabiliteten nåddes i olika obalans scenarier med hög andel solcellgeneration och misnkat svängsmassa. Detta tyder på att en hög andel PV integration är både ekonomisk- och tekniskt möjligt i mindre elsystem.

The present work deals with the implementation of the test system Nordic32 proposed by Cigre task force 38-02-08. This test system which consists of 32 buses is a representation of the Swedish transmission and is suitable for the simulation of transient stability and long term dynamics. This work provides a detailed description about the steps followed to create both the static part of the system for load flow calculations and the controllers that the generators are equipped with. Furthermore, the thesis closes with a basic study concerning the modal analysis and the voltage stability of the system revealing some weaknesses that need further examination.

The plans to reduce the energy-related greenhouse gas emissions stimulate the deployment of electronically interfaced renewable resources. The increased penetration of such intermittent sources together with phasing conventional power plants out and the installation of High Voltage Direct Current (HVDC) links for long-distance more efficient transmission, reduces the stored inertia in any electrical grid. This leads to a more vulnerable power system and increases the significance of studying the corresponding stability aspects. Decreasing the inertial response of a power system deteriorates the quality of both frequency and rotor-angle stability which are the dynamics of interest in this study. The thesis explores the role of the location of low inertia on varying the power system’s dynamics. This is to be conducted in isolation of all other factors that could affect the study outcomes, such as dealing with the same system’s inertia value upon lowering the inertia in different locations. To accomplish this objective, it is essential to analyze the inertia distribution of the examined power system following the alterations of inertia reduction location. Accordingly, an inherently previous work methodology, that estimates the relative distance of the system’s components to Center Of Inertia (COI), is utilized throughout this study. Both frequency response and small-signal stability are analyzed in light of the inertia distribution results. The thesis examines two different power systems, a small two-area model and a bigger more realistic power system. The former model, known as Kundur model, helps in building a conceptual process to apply the methodology and to benchmark the dynamics of interest. While the latter is a reduced model of the Swedish transmission grid, known as Nordic 32 model. Different scenarios of low inertia are considered to capture the current trend of integrating more Renewable Energy Sources (RES) and phasing out more conventional plants. DIgSILENT Powerfactory is the weapon of choice in this study. It is utilized to assess both the frequency stability by performing electromechanical transients’ simulations, and small-signal stability following modal analysis simulations.  Results show that the alterations of low inertia location are associated with variations in Instantaneous Frequency Deviation (IFD), Rate Of Change Of Frequency (ROCOF) and the damping ratio of the most critical inter-area oscillation mode. These variations have different levels of significance. Variations of the latter two metrics have the most considerable effects from the stability’s perspective. They can be utilized to prioritize the phasing out process of the conventional power plants, and to choose one of the scenarios of a specific low inertia location over the others. This helps in fulfilling proper long-term planning and short-term operation from the system operator’s perspective.

Grid connection of wave energy is one of the crucial remaining areas of development towards the commercialization of this renewable energy technology. One of the major challenges with the grid connection of the wave energy technology is power variability. The rapidly changing voltage and power production from very high peaks to lows, increases the complexity for the wave farm developers to reach an agreement with the grid owners to satisfy the grid compliance. Correspondingly, electrical network designs of the offshore wind sector also differ on some key features which includes the power variability, cable lengths, power ratings, connection layouts, sea depths and transmission distances. These differences present new challenges to engineers in adapting technology and knowhow from the wind industry wherever applicable; whereas in parts of the network where power ratings are <2 MW, new designs need to be derived. Hence, power system dynamic modelling of variable emerging wave energy puts a great field of research. CorPower Ocean AB is in the process of developing a 300-kW point absorber type Wave Energy Converter (WEC) that is a commercial fullscale prototype. In this regard, the thesis will discuss the topics of optimization of offshore wave energy electrical networks for farms primarily focused on a 10 MW rating. The modelling for RMS simulation, network efficiency, voltage profile and power quality analysis has been simulated on DIgSILENT PowerFactory. Grid connection compliance for voltage levels, voltage flicker and power factor has been evaluated against local site regulations and parameters for optimal efficiency and better power quality with respect to grid connection is discussed. The impact of grid impedance angle and the wave front incidence angle on the rating of wave farm being connected is also evaluated. The study leads to an optimized electrical layout of a wave farm which can tackle problems such as voltage flicker and varying power. The study also leads to the understanding of better layout for the point absorber with least transmission losses. This study can also be generalized for bigger wave farms in the future which will reduce the complexity and time for wave farms engineers while planning.

The increasing amount of renewable energy sources is applying more and more pressure on today’s power system. Additionally, plannable sources of energy, which are mostly non-renewable, are being decommissioned at a high rate to combat climate change. The decommissioning of non-renewable producers and the increasing number of intermittent sources of energy are causing an increasingly volatile power system. In addition to the lack of plannable production, the inertia from synchronously rotating machines is decreasing due to the lack of contribution from renewable sources. The inertia of a power system assists in slowing down large frequency changes. When a notably large difference between production and consumption occurs in a power system with low inertia, components which can quickly counteract these effects by supplying the system with active power, are needed. The low inertia can also cause problems to the synchronicity of the synchronously rotating machines in the system, namely the rotor angle stability. A lack of rotorangle stability can cause the synchronicity of the synchronously rotating machines to be questioned. Fast frequency response units supply the power system with active power for a short period of time to reduce the rate of change of frequency and frequency deviation, which in turn allows the self-regulating units more time to adjust their production. Furthermore, these units can improve rotor angle stability. Such units can consist of batteries which are both serially and parallel connected with their associated control unit. This thesis aims to, with the help of the power system analysis program PowerFactory, and its associated dynamic simulation tools, formulate a methodology which can be used in power system models to locate the best placement for fast frequency response units. The results show that the formulated methodology can be used to find the best position of fast frequency response units for frequency deviation-, rate of change of frequency- and rotor angle stability support.

The study carried out in this master thesis is part of a larger project led by Energynautics GmbH focusing on renewable energy development in the Caribbean. One of the Caribbean states, consisting of multiple islands, has set a target of 30 % of renewable energy in the power sector by 2030. The first objective of the thesis is to develop optimal generation capacity expansion plans for two different islands of this country, utilizing solar PV generation, which is the only available renewable energy resource. To achieve this objective, three main tasks are identified. The first is the development of an optimal generation capacity expansion plan for the next three years using the optimization tool HOMER Energy. At the beginning only diesel generation is present on the islands. For each study case year, the installed capacity of PV and BESS is optimized and enabling technologies such as curtailment (controllability of PV) and grid-forming inverters are deployed. The second task focuses on the development of a new dispatch strategy, improving on the black box dispatch algorithms built into HOMER. The dispatch strategy minimises the cost of electricity generation and is based on a rolling 48 hours forecasts of the load and PV. It is implemented in MATLAB and linked to HOMER via the built-in MATLAB interface. As HOMER is focused on generation expansion and dispatch and inherently neglects the grid, a grid study is required to assess the stability of the network. This study is the last task of the thesis and is limited to determined steady-state voltage and the asset loading on one of the studied islands through load flow simulations in DIgSILENT PowerFactory. It is shown that there are no major issues even at high PV shares, however, grid performance can be improved if the PV unit is equipped with reactive power capability to control the voltage. A study on the impact of the Q(U)- control and the PQ-capability of the PV and BESS inverters is performed. / Studien som genomförts i detta examensarbete är en del av ett större projekt vilket leds av Energynautics GmbH med fokus på utveckling av förnybar energi i Karibien. En av de Karibiska staterna, bestående av flera öar, har ett mål på 30 % förnybar energi i elkraftssektorn innan 2030. Första syftet med examensarbetet är att utveckla optimala utbyggnadsplaner för produktionskapaciteten för två olika öar i detta land, med användning av solcellsproduktion, vilket är den enda tillgängliga förnybara energikällan. Den första uppgiften är utvecklingen av en optimal utbyggnadsplan för produktionskapaciteten för de kommande tre åren med optimeringsverktyget HOMER Energy. Från början fanns det bara dieselgeneratorer på öarna. För varje studerat år optimeras den installerade kapaciteten av PV och BESS samt aktivering av möjliggörande teknologier som begränsning av PV-produktion och grid-forming växelriktare. Den andra uppgiften fokuserar på utvecklingen av en ny driftsstrategi, förbättring av den basala driftsalgoritm som är inbyggd i HOMER. Driftsstrategin minimerar kostnaden av elproduktionen och är baserad på en 48 timmars prognos av laster och PV. Den är implementerad i MATLAB och kopplad till HOMER via det inbyggda MATLABgränssnittet. Eftersom HOMER fokuserar på produktionsutbyggnad och drift och i praktiken försummar elnätet, krävs en studie av elnätet för att utvärdera stabiliteten av elnätet. Studien av denna sista uppgift i examensarbetet är begränsad till att bestämma spänningen vid jämnviktsläge och den utvärderade lasten på en av de studerade öarna genom belastningsfördelningsberäkning i DIgSILENT PowerFactory. Det visade sig att det inte fanns några stora problem även med stora andelar PV, men elnätets prestanda kan förbättras om PV-omriktarna är utrustade med reaktiv effektstyrning som kontrollerar spänningen. En studie avinverkan från Q(U)-styrning och PQ-kapacitet av PV- och BESS-växelriktare har utförts.