This Bachelor thesis has been written at the Blekinge Institute of Technology. This thesis concentrates on the wind power and their components, also the large wind farm is studied. The electrical power is generated by using the power in wind to drive a wind turbine to produce mechanical power. This mechanical power can be converted into electrical power by using electrical induction generators. There are two types of the wind turbines, the horizontal axis and vertical axis wind turbine, where the horizontal axis wind turbine is mostly used and was studied in this thesis. The rotor can be placed in two directions: an upwind rotor where the blade of turbine faces to the wind, so it operates more smoothly and transmit more power. The other type is a downwind rotor which orients itself with respect for the wind direction. Moreover, the tower shadow makes the blade to flex, consequently resulting in fatigue, noise, and reduces output of the power. The modern wind turbine has been built with an odd number of blades which is important for the stability of the turbine. The rotor with an odd number of blades can be considered to be similar to a disc when calculating the dynamic properties of the machine. The main idea of this thesis is to study the wind power in general and large wind parks specifically. The Horns Rev wind park was taken as an example of a wind park in Denmark and the Gotland wind park as an example of a wind park in Sweden too. Into account, the distance between wind turbine in the wind direction cannot be too small. If the wind turbines are located to close to each other, the wind will be more and more turbulent after it passes through each single wind turbine. This would lead to that wind turbines downstream in the wind park, and it might even have to shut down due to that mechanical loading gets to high during strong conditions. This is due to the fact that when wind passes through the rotor of the wind turbine it gets very turbulent and the wind speed is decreased. The minimum length of the rotor should be approximately 5-7 rotor diameters to avoid that issue. Gotland Energy AB (GEAB) considered, that high voltage direct current light would be the only realistic way to solve the technical problems for the high amount of wind power in-feed. One result is that The stability of voltage during transient events, has become much better by using the high voltage direct current light so that the output current stability from the asynchronous generators have been improved, which reduces the stresses on the AC grid and on the mechanical construction of the windmills. / In general the wind turbines with three blades accommodated a thicker root are used. It is obvious that, the less number of blades on the wind turbine, the cost of material and manufacturing will be lower. It is worthy to mentioned that, the modern wind turbine has been built with an odd number of blades. When the length of the blade increases the deflection of blade tip due to axial wind force also increase as well. So without consider the increase in length of blade may lead to dangerous situation of collision of tower and blade. Moreover, by increasing the number of blades cost of the system would increased as well. The limit of transfer for the AC transmission system depends on the distance from shore and is therefore physically limited by this. AC large wind parks that are placed at a long distance from the shore, which means AC long transmission line, and more drop voltage A solution to AC long transmission line, it could be to decrease the offshore frequency and use a low frequency AC networks. There is a suggestion by for instance (Schütte, Gustavsson and Ström 2011). The usages of a low frequency system are in electrified railway systems, where the frequency ranges from 16.67 Hz to 25 Hz. However, the network of a low frequency would allow a simpler design of the offshore WTs and The aerodynamic rotor of a large WT operates at maximum revolutions at 15-20 rpm. The lower frequency would then allow a smaller gear ratio for turbines with a gearbox, or decrease the poles number for WTs with direct driven generators. This would lead to lighter and cheaper turbines. One of the disadvantages by using a low frequency system is the size of transformer would be increased, and hence, the costs of transformer will increased too. The operator of the grid, Gotland Energy AB (GEAB) considered, that HVDC light would be the only realistic way to solve the technical problems for the high amount of wind power in-feed. The experiences have supported expected improvements in the characteristics for example: - Stability in the system arose. - Reactive demands, power flows, as well as voltage level in the harmonic and system were reduced. - Flicker problems were eliminated with the installation of HVDC light and transient phenomena disappeared. Moreover, Overall experiences of Gotland Energy AB (GEAB) are that the control of power flow from the converters makes the AC grid easier to observe than a conventional AC network and the power variations do not stress the AC grid as much as in normal network. Voltage quality has been better with the increased wind power production. A topic to study in the future is the consequences of blackouts in power supply with many wind power farm. / 004676396018

Tesis por compendio / [ES] La Unión Europea plantea una serie de retos en el GREEN DEAL para conseguir un escenario donde sus miembros sean climáticamente neutros en 2050. Para ello se plantean unas acciones entre las que destaca la descarbonización del sector de la energía. Por otra parte, se ha puesto como objetivo conseguir una capacidad de energía eólica de 1200 GW en 2050, desde los 190 GW que se tenía en 2019. El cierre de centrales eléctricas basadas en grandes generadores síncronos junto con el aumento en la construcción de centrales eléctricas con fuentes basadas en electrónica de potencia como parques eólicos o plantas fotovoltaicas, hace necesario la incorporación de controladores grid forming en energías renovables basadas en electrónica de potencia. La integración de estrategias de control grid forming en turbinas eólicas debe considerar las funciones de reparto de potencia activa y reactiva (control droop en generadores síncronos), así como un sistema de protección ante faltas que permita una recuperación rápida cuando se despeja la falta. Por otra parte, en la transición de los actuales parques eólicos grid following que funcionan como fuentes de corriente a parques eólicos grid forming que funcionan como fuentes de tensión se debe considerar que ambas tecnologías van a coexistir conjuntamente por mucho tiempo. Por tanto, se hace necesario el estudio de estabilidad de parques eólicos con ambas tecnologías, así como el estudio de cuanta generación grid forming es necesaria para mantener el parque eólico estable en cualquier situación. Además, el uso de parques eólicos grid foming permite diferentes aplicaciones como la energización de redes eléctricas después de un apagón desde estos parques eólicos, o el uso de diodos rectificadores en enlaces HVDC para la conexión de parques eólicos marinos. Para facilitar el estudio y diseño de aerogeneradores grid forming, en la presente tesis se propone una técnica de agregación de aerogeneradores tipo-4. Esta técnica permite reducir la complejidad del parque eólico para su estudio y análisis. Esta tesis incluye las siguientes contribuciones: Para el funcionamiento de aerogeneradores grid forming en paralelo con aerogeneradores grid following se propone un método de diseño analizando la estabilidad del sistema completo. Además, se propone una estrategia de control ante faltas para asegurar una recuperación rápida y segura. Se propone el uso de técnicas de control H∞ para la sintonización de controladores grid forming. El uso de estas técnicas para el diseño de controladores puede mejorar la robustez de los controladores, así como el rendimiento de estos. Considerando la aplicación de la energización de redes HVAC desde parques eólicos, se ha propuesto como llevar a cabo dicha maniobra a partir de parque con aerogeneradores grid forming y grid following. Los resultados obtenidos validan el funcionamiento de la operación. Además, muestran que la cantidad de generación grid forming está relacionada con la dimensión de cargas que tienen que aguantar dichas turbinas más que con la estabilidad del sistema con un porcentaje bajo de generación grid forming. Finalmente, se han propuesto estrategias de protección para la integración de parque eólicos en redes malladas HVDC utilizando rectificadores de diodos. Los parques eólicos grid forming pueden ayudar a gestionar faltas disminuyendo los requisitos en las protecciones necesarias en el enlace HVDC. Esto permite una reducción del coste de la instalación, además de aumentar la robustez del sistema. / [CA] La Unió Europea planteja uns reptes al GREEN DEAL per a aconseguir un escenario on els seus membres siguen climàticament neutrals al 2050. Per a aconseguir aquest objectiu es plantegen unes accions entre les quals destaca la de descarbonitzar el sector energètic. D'altra banda, s'ha posat com a objectiu aconseguir una capacitat d'energia eòlica de 1200 GW al 2050, des dels 190 GW que es tenia al 2019. El tancament de centrals elèctriques basades en grans generadors síncrons juntament amb l'augment en la construcció de centrals elèctriques basades en electrónica de potència com a parcs eòlics o plantes fotovoltaiques, fa necessari la incorporació de controladors grid forming en energies renovables que es basan en electrònica de potència. La integració d'estratègies de control grid forming per a turbines eòliques ha de considerar les funcions de repartiment de potència activa i reactiva, així com un sistema de protecció davant faltes que permeta una recuperació ràpida quan s'aïlla la falta. D'altra banda, en la transició dels actuals parcs eòlics grid following que funcionen com a fonts de corrent a parcs eòlics grid forming que funcionen com a fonts de tensió, s'ha de considerar que totes dues tecnologies coexistiran conjuntament per molt de temps. Per tant, es fa necessari l'estudi d'estabilitat d'un parc eòlic amb totes dues tecnologies, així com l'estudi del percentatge de generació grid forming necessari per a mantindre el parc eòlic estable en qualsevol situació. A més, l'ús de parcs eòlics grid foming permet diferents aplicacions com l'energització de xarxes elèctriques després d'una apagada des d'aquests parcs eòlics, o l'ús de díodes rectificadors en enllaços HVDC per a la connexió de parcs eòlics marins. Per a facilitar l'estudi i disseny d'aerogeneradors grid forming, en la present tesi es proposa una tècnica d'agregació d'aerogeneradors tipus-4. Aquesta técnica permet reduir la complexitat del parc eòlic per al seu estudi i anàlisi. La present tesi inclou les següents contribucions: Per al funcionament d'aerogeneradors grid forming en paral¿lel amb aerogeneradors grid following es proposa un mètode de disseny analitzant l'estabilitat del sistema complet. A més, es proposa una estratègia de control davant faltes per a assegurar una recuperació ràpida i segura. Es proposa l'ús de tècniques de control H∞ per a la sintonització de controladors grid forming. L'ús d'aquestes tècniques per al disseny de controladors pot millorar la robustesa dels controladors, a mé del rendiment d'aquestos. Considerant l'aplicació de l'energització de xarxes HVAC des de parcs eòlics, s'ha proposat com dur a terme aquesta maniobra a partir d'un parc eòlic amb aerogeneradors grid forming i grid following. Els resultats obtinguts validen el funcionament de l'operació. A més, mostren que la quantitat de generació grid forming està més relacionada amb la dimensió de les càrregues que ha d'aguantar el parc eòlic, que amb l'estabilitat del sistema que permet un menr percentatge de generació grid forming. Finalment, s'han proposat estratègies de protecció per a la integració de parcs eòlics marins en xarxes multi-punt HVDC utilitzant rectificadors de díodes. Els parcs eòlics grid forming poden ajudar a gestionar faltes disminuint els requisits de les proteccions necessàries en l'enllaç HVDC. Això permet una reducció del cost de la instal¿lació, a més d'augmentar la robustesa del sistema. / [EN] The European Union GREEN DEAL aims to make its 27 members climate-neutral by 2050. The decarbonization of the energy sector stands out as one of the proposed actions. To achieve that goal, the target for wind power generation is set at 1,200 GW in 2050, from the 190 GW that was had in 2019. The closure of power plants based on large synchronous generators and the increase of power electronics based generation such as Wind Power Plants (WPPs) or photovoltaic plants, leads to the use of grid forming controllers for power electronics based renewable energy. Grid forming control strategies for wind turbines generators (WTGs) must consider active and reactive power sharing control (droop control in synchronous generators) as well as a protection system that allows a quick recovery after fault clearance. Moreover, a transition from the conventional grid following WPPs to new grid forming WPPs is required. The transition must consider the parallel operation of both technologies for a long time. Thus, it is necessary to study the stability of Wind Power Plants with both technologies, as well as the study of how much grid forming generation is required to keep a mixed grid forming and grid following WPP stable in any situation. In addition, the use of grid forming WPPs allows different applications such as the energization of HVAC and HVDC grids after a blackout from these WPPs, or the use of diode rectifiers in HVDC links for the off-shore WPPs connection. An aggregation technique for type-4 WTGs has been proposed in this thesis in order to facilitate the study and design of grid forming WPPs. The aggregation technique allows to reduce the WPP complexity for its study and analysis. The main contributions of this theses are: A design methodology has been proposed for the parallel operation of grid forming and grid following WTGs. Including the stability analysis of the complete system. Additionally, a fault control strategy is proposed to ensure a fast and safe recovery. The use of H∞ control techniques is also proposed for grid forming controller tuning. Using H∞ control techniques for controller design may improve the robustness of the controllers as well as the performance of the controllers. A procedure to carry out black start operation of HVAC grid from mixed grid forming and grid following WPPs has been proposed. The obtained results validate that the procedure works as expected. Moreover, the results show that the amount of grid-forming generation usually is determined by the load size steps as stability limits are usually less stringent. Finally, protection strategies have been proposed for the integration of off-shore WWPs in multi-terminal HVDC grids using diode rectifiers. Grid forming WPPs are able to help managing faults. Their use allow lower requirements of the HVDC protection equipment, leading to overall cost reduction and an increment of the system robustness. / Martínez Turégano, J. (2022). Grid Forming Wind Power Plants: Black start operation for HVAC grids and Diode Rectifier-based Wind Power Plant integration [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/181529 / TESIS / Compendio