This dissertation about the Stirling engine deals with the history and formation of the heat engine. At the beginning of this work, fundamental parts and their functions are described, elucidating the principle of operation explained by the thermodynamic cycle and subsequently comparing the ideal and the real Stirling cycle and last but not least provides various modifications whilst describing their differences. The mathematical model of the Stirling engine is processed by Schmidth’s theoretical analysis and thereafter is created in PScad v46. The process of creating a model is shown in one of the chapters of this dissertation. The results were taken into account in the design of 3D models in Inventor Professional by Autodesk. The work concludes with the evaluation of the computational model and its functionality as well as the documentation of the 3D model.

Recently, with growing application of wind power, the system based on the doubly fedinduction generator (DFIG) has become the one of the most popular concepts. Theproblem of connecting to the grid is also gradually revealed. As an effective solution toconnect offshore wind farm, VSC-HVDC line is the most suitable choice for stabilityreasons. However, there are possibilities that the converter of a VSC-HVDC link canadversely interact with the wind turbine and generate poorly damped sub-synchronousoscillations. Therefore, this master thesis will derive the linear model of a single DFIG aswell as the linear model of several DFIGs connecting to a VSC-HVDC link. For thelinearization method, the Jacobian transfer matrix modeling method will be explainedand adopted. The frequency response and time-domain response comparison betweenthe linear model and the identical system in PSCAD will be presented for validation. / Nyligen, med ökande tillämpning av vindkraft, det system som bygger på den dubbeltmatad induktion generator (DFIG) har blivit en av de mest populära begrepp. Problemetmed att ansluta till nätet är också gradvis avslöjas. Som en effektiv lösning för att anslutavindkraftpark är VSC -HVDC linje det lämpligaste valet av stabilitetsskäl. Det finns dockmöjligheter att omvandlaren en VSC-HVDC länk negativt kan interagera medvindturbinen och genererar dåligt dämpade under synkron svängningar. Därför kommerdetta examensarbete härleda den linjära modellen av en enda DFIG liksom den linjäramodellen av flera DFIGs ansluter till en VSC-HVDC -länk. För arise metoden kommerJacobian transfer matrix modelleringsmetodförklaras och antas. Jämförelse mellan denlinjära modellen och identiskt system i PSCAD frekvensgången och tidsdomänensvarkommer att presenteras för godkännande.

This work proposes recommendations for new guidelines for fault current injection on a distribution grid. These guidelines will help improve the transition towards renewable electrical energy generation. The grid-integration of inverter-based distributed generations (IBDGs) into the distribution grid changes the topology of a conventional grid with one-way power flow to a grid with multi-way power flow. This thesis investigates the impact of fault current injection on a distribution grid, if the limitations in the fault current injection of IBDGs affect the reliable function of the protection system and if there is a preferable type of current control to be prioritised. This investigation was carried out through a literature review and transient state simulations on a model grid in PSCAD. The grid is based on a real radial distribution grid on the Swedish island of Gotland, where a Type III wind turbine generator (WTG) is connected. The limitation on fault current injection by the wind turbine, the location and type of fault in the grid, can affect the reliable function of the protection system. The control system inside a type III WTG affects its fault current injection that impacts fault detection by the protection system. This thesis emphasizes the need for a guideline and requirement on the WTG control system for fault current injection. Prioritising reactive current control (q-axis) seems to be preferable and should become the standard for fault current injection in type III wind turbine generators in this distribution grid, according to this study. Furthermore, the need for more investigation for different types of IBDGs with different control strategies is highlighted in this work. / Detta arbete föreslår rekommendationer för nya riktlinjer för felströmsinjektering i ett distributionsnät. Dessa rekommendationer kommer bidra till att förbättra omställningen till förnyelsebar elgenerering. Integreringen av omriktarbaserade distributionsgeneratorer (IBDG) i distributionsnätet förändrar topologin i ett konventionellt nät med ett enkelriktat effektflöde till ett flervägsriktat effektflöde. Detta examensarbete undersöker påverkan av felströmsinjektering i ett distributionsnät, om begränsningarna i felströmsinjekteringen hos IBDG:er påverkar reläskydds pålitliga funktionalitet och om det finns en typ av kontrollström som föredras och bör prioriteras. Denna undersökning genomfördes genom en litteraturstudie och transienta simuleringar i ett exempelnät i PSCAD. Nätet är baserat på ett verkligt radialdistributionsnät från Gotland, där ett Typ III vindkraftverk (WTG) är anslutet. Begränsningen i felströmsinjektering hos vindkraftverket, platsen för och typen av fel i nätet kan påverka den pålitliga funktionaliteten hos reläskydd. Kontrollsystemet inuti ett Typ III WTG påverkar dess felströmsinjektering som påverkar feldetekteringen i reläskyddet. Detta examensarbete betonar vikten av riktlinjer och krav på WTG kontollsystem för felströmsinjektering. Prioritering av reaktiv kontrollström (q-axis) verkar vara fördelaktigt och bör bli standard för felströminjektering i Typ III WTG i detta distributionsnät, enligt detta arbete. Dessutom påtalas behovet av att ytterligare undersöka olika typer av IBDG:er med olika kontrollstrategier i detta arbete.

Rapidly growing Inverter- Based Resources (IBR) have different fault properties compared to Synchronous Generators (SG). Therefore, it is necessary to study the fault behavior of systems that contain different types of IBR and compare it to the conventional system responses in order to understand what steps should be taken to adapt conventional protection settings for new types of sources. For a two bus model, it is found out that sequence profiles in a system with one IBR are different from those observed in conventional system. Thermal and electrical limitations of the power electronics reduce the fault current from the IBR significantly, driving negative sequence current to small values compared to conventional sources. This is true for all studied types of IBR. Moreover, if IBR is connected to the grid through one line only, during Three Phase Fault (3hp) it is possible to lose synchronism with grid due to erroneous estimation of the grid angle through the Phase-Locked Loop (PLL). Verification of the obtained results is made through comparison to the Fault Recordings taken from the protection relays placed at substations. It is shown that for some faults simulation results can predict the behavior of symmetrical components in the network whereas for others they do not. To explain the latter behavior modifications to the sequence networks are proposed. / Snabbt växande inverterbaserade resurser (IBR) har olika felinmatningsegenskaper jämfört med synkrongeneratorer (SG). Därför är det nödvändigt att studera felbeteende hos system som innehåller olika typer av IBR och jämför det med konventionella källor för att kunna förstå vilka steg som ska göras för att anpassa konventionella skyddsinställningar för nya typer av källor. Under litteraturöversikten introduktion till det fast jordade systemet och dess speciella fall med isolerad transformatorjordning är klar. Kort introduktion till den studerade IBR och typer av simulerade fel görs också. För en tvåbussmodell har det visat sig att sekvensprofiler i ett system med en IBR skiljer sig från de som observerats i konventionella system. Termisk och elektrisk begränsningar i kraftelektroniska komponenter minskar felströmmen från IBR avsevärt och driver negativ sekvensström till små värden jämfört med konventionella källor. Detta gäller för alla studerade typer av IBR. Dessutom, om IBR är ansluten till nätet endast genom en linje, är det möjligt under trefasfel (3hp) att tappa synkronisering med nätet på grund av felaktig uppskattning av fasvinkeln genom styrsystemets faslåst slinga (PLL). Verifiering av de erhållna resultaten görs genom jämförelse med Fel Inspelningar från reläet placerade på transformatorstationer. Det visas att för vissa fel simuleringsresultat kan förutsäga symmetriska komponenters beteende i nätverket medan andra inte gör det. För att förklara de senare beteendena föreslås modifieringar i sekvensnätverket.

Sistemas de transmissão de energia elétrica em corrente contínua e alta tensão baseados em tecnologia de conversores a fonte de tensão (VSC-HVDC), ao contrário de linhas de transmissão em corrente alternada, operam como elementos de controle de variáveis elétricas, podendo ser úteis na estabilidade do sistema de potência. Mas apesar desta vantagem, sistemas VSC-HVDC possuem limitações no desempenho estável, o que enseja o desenvolvimento de uma metodologia para mapeamento de suas zonas de operação estável e possíveis regiões de instabilidade. Inicialmente estudou-se os detalhes da tecnologia VSC-HVDC tais como o funcionamento da eletrônica de potência e estratégias de controle utilizadas. Em seguida, investigou-se os modelos de geradores síncronos para interconexão com o lado CA das estações conversoras do VSC-HVDC. E, finalmente, aplicou-se a tecnologia VSC-HVDC sobre um modelo de sistema de potência com uma estação conversora localizada em um porto offshore e uma outra no continente, próxima à rede de alta tensão em corrente alternada. Simulações e análise deste sistema foram executadas considerando várias condições operacionais. O gráfico de potência gerada e consumida, obtido pela aplicação da metodologia, apresenta grande potencial de uso prático como por exemplo sua implementação na interface homem-máquina da estação de operação do porto offshore, provendo informação em tempo real de alto nível ao operador do sistema elétrico do porto offshore e consequentemente aumentando sua consciência situacional quanto a proximidade dos limites de instabilidade. / High voltage direct current power transmission systems based on voltage source converters (VSC-HVDC), as opposed to alternating current ones, operates as elements of control of electrical variables, being useful for stability of power system. Besides this advantage, VSC-HVDC systems have limitations in stable performance, which instigates the development of a methodology for mapping its operational zones of stability and possible regions of instability. The author initially studied the details of the VSC-HVDC technology such as the power electronic principles and the control strategies used on this research. Subsequently, the author investigated synchronous generator models for interconnection on the AC side of the VSC-HVDC converter stations. Finally, the author applied the VSC-HVDC technology on a model of power system with two converter stations, one located on an offshore port and the other on the shore, next to an alternating current high voltage power grid. Simulations and analysis of this system were carried out considering various operational conditions. The graphic of generated and consumed power on offshore port, obtained by the application of the methodology for mapping operational zones, presents a great potential of being implemented in the man-machine interface of an operation workstation, thus providing high level online information for the operator of the offshore port electrical system and consequently improving its situational awareness of the proximity to instability limits.

Sistemas de transmissão de energia elétrica em corrente contínua e alta tensão baseados em tecnologia de conversores a fonte de tensão (VSC-HVDC), ao contrário de linhas de transmissão em corrente alternada, operam como elementos de controle de variáveis elétricas, podendo ser úteis na estabilidade do sistema de potência. Mas apesar desta vantagem, sistemas VSC-HVDC possuem limitações no desempenho estável, o que enseja o desenvolvimento de uma metodologia para mapeamento de suas zonas de operação estável e possíveis regiões de instabilidade. Inicialmente estudou-se os detalhes da tecnologia VSC-HVDC tais como o funcionamento da eletrônica de potência e estratégias de controle utilizadas. Em seguida, investigou-se os modelos de geradores síncronos para interconexão com o lado CA das estações conversoras do VSC-HVDC. E, finalmente, aplicou-se a tecnologia VSC-HVDC sobre um modelo de sistema de potência com uma estação conversora localizada em um porto offshore e uma outra no continente, próxima à rede de alta tensão em corrente alternada. Simulações e análise deste sistema foram executadas considerando várias condições operacionais. O gráfico de potência gerada e consumida, obtido pela aplicação da metodologia, apresenta grande potencial de uso prático como por exemplo sua implementação na interface homem-máquina da estação de operação do porto offshore, provendo informação em tempo real de alto nível ao operador do sistema elétrico do porto offshore e consequentemente aumentando sua consciência situacional quanto a proximidade dos limites de instabilidade. / High voltage direct current power transmission systems based on voltage source converters (VSC-HVDC), as opposed to alternating current ones, operates as elements of control of electrical variables, being useful for stability of power system. Besides this advantage, VSC-HVDC systems have limitations in stable performance, which instigates the development of a methodology for mapping its operational zones of stability and possible regions of instability. The author initially studied the details of the VSC-HVDC technology such as the power electronic principles and the control strategies used on this research. Subsequently, the author investigated synchronous generator models for interconnection on the AC side of the VSC-HVDC converter stations. Finally, the author applied the VSC-HVDC technology on a model of power system with two converter stations, one located on an offshore port and the other on the shore, next to an alternating current high voltage power grid. Simulations and analysis of this system were carried out considering various operational conditions. The graphic of generated and consumed power on offshore port, obtained by the application of the methodology for mapping operational zones, presents a great potential of being implemented in the man-machine interface of an operation workstation, thus providing high level online information for the operator of the offshore port electrical system and consequently improving its situational awareness of the proximity to instability limits.

Η παρούσα διπλωματική εργασία έχει ως αντικείμενο τη διερεύνηση της λειτουργίας και το σχεδιασμό συστήματος ελέγχου του δυναμικού αποκαταστάτη τάσης (DVR - Dynamic Voltage Restorer, όπως αναφέρεται στη διεθνή βιβλιογραφία) που χρησιμοποιείται στα δίκτυα διανομής. Η συγκεκριμένη συσκευή ανήκει στην κατηγορία των FACTS (Flexible ac Transmission Systems), παρέχει εν σειρά αντιστάθμιση, και ο σκοπός λειτουργίας της είναι η βελτίωση της ποιότητας της παρεχόμενης ισχύος και η αύξηση της αξιοπιστίας του συστήματος. Εξειδικεύεται στις βυθίσεις τάσεως. Πιο συγκεκριμένα, ο δυναμικός αποκαταστάτης τάσης έχει στόχο, όπως μαρτυρά και το όνομά του, να διατηρεί την τάση ενός φορτίου κατά το δυνατόν σταθερή στην τιμή που αυτή είχε πριν συμβεί η όποια βύθιση. Έτσι, θα καταβληθεί προσπάθεια προκειμένου να προσομοιωθεί η λειτουργία μιας τέτοιας συσκευής σε ένα απλό δίκτυο με τη βοήθεια του λογισμικού PSCAD. Θα κατασκευαστεί ο DVR καθώς και το σύστημα ελέγχου του κι αφού συνδεθεί σε ένα φορτίο, θα δημιουργήσουμε διάφορα είδη σφαλμάτων και θα μελετήσουμε την απόκρισή του και την ικανότητά του να αποκαθιστά την τάση. / This diploma thesis refers to Dynamic Voltage Restorer (DVR), a series compensator used in transmission systems. It is a device that belongs to FACTS and its main function is the mitigation of volatge sags and swells.

The main point of this thesis is the extension of the complex solar radiation simulator, the creation of new functionalities, and the cooperation of this complex simulator with the PV power plant. This work builds on the work done in the area of solar radiation modeling. The thesis deals with the continuation, or improvement of some shortcomings, removing shortcomings, such as fixing the beginnings and ends of the simulation, correcting the calculation of sunrise and sunset, but also adding different types of clouds, combinations of different preset cloud situations, or data input, and more. These deficiencies are found in the bachelor's thesis "Complex Simulator of the solar irradiance", and PSCAD is the main tool in this work. Another important point of this work is the realization of the simulation where an improved solar radiation simulator works in cooperation with a model of a photovoltaic panel or a PV power plant, respectively. It has different operating states created in PSCAD. These include, for example, cloud crossings, both over the entire power plant and only partial. In addition, there are experiments that prove the fact that the direction of the incoming cloud plays a role in the power of the PV power plant.

This thesis focused on creating a model of a small hydropower plant model (SHPP) and a part of the electricity network in the simulation software "PSCAD" (basing on real sources). The model will be specified on the basis of the data obtained from the measurements to correspond with the real equipment.

This diploma thesis discusses two major topics. The first one is the control size of the voltage in LV networks in regard to the increase in distributed generation concered to renewable energy sources. The study contains a review focused on the current state of low voltagegrid followed by a proposal for the solution of the oncoming state. The solution is identified as a deploying OLTC distribution transformer. In the case of more complex topology is deployed a series voltage transformer. Both methods are part of the Smart Grid. The thesis also analyzes the issue of the data measurement and data transmission. The second part of the thesis consists of the description of selected control strategies and their simulations. The design of individual system elements in the PSCAD is described. From these elements, a test network was constructed and tested the individual simulation scenarios.