Modelización dinámica y control de un aerogenerador de velocidad variable con una máquina de inducción doblemente alimentada en PSS/E

Hoy en d a, debido a la creciente penetraci on de la energ a e olica en la red el ectrica, los Operadores del Sistema de Transmisi on (TSO) se han visto obligados a revisar los requerimientos de conexi on a la red (Grid Codes), con el n de garantizar una correcta calidad de la energ a, tanto a nivel de abilidad como de estabilidad. As pues, para asegurar el correcto funcionamiento de los parques existentes y de los futuros, se requieren modelos din amicos ables y detallados, que permitan reproducir faltas con la su ciente exactitud como para veri car la idoneidad de estos. A tal n, en este proyecto se desarrolla un modelo din amico mediante el programa de simulaci on PSSTME. Dicho modelo comprende un aerogenerador de velocidad variable, de aspas orientables, y con generador de inducci on doblemente alimentado (DFIG). El dise~no del control se lleva a cabo a dos niveles: a alto nivel (control de velocidad o extracci on de m axima potencia del viento y control de pitch) y a bajo nivel (control del convertidor mediante la t ecnica del control vectorial). Adicionalmente, se a~nade al dise~no de control una regulaci on de frecuencia para el control de su estabilidad. Finalmente, se simulan unas situaciones de inter es con el modelo completo y se veri ca que se cumpla con los nuevos requisitos que imponen los TSO

Design, operation and control of novel electrical concepts for offshore wind power plants

Offshore wind is an emerging energy sector with a huge potential to be tapped in the near future. Offshore Wind Power Plants (OWPPs) are becoming increasingly relevant in Europe and worldwide mainly because the wind speeds are potentially higher and smoother than their onshore counterpart, which leads to higher wind power generation. Moreover, OWPPs have less space limitations constraints, so that it allows the possibility of using larger wind turbines. Nowadays, environmental and social aspects are forcing OWPPs to be constructed further from shore, (which usually leads to deeper waters) and the trend is expected to continue in the coming years. Several studies have demonstrated that if the distance between an OWPP and its grid connection point at the Point of Common Coupling (PCC) exceeds a certain critical distance (approximately 55-70 km), HVDC transmission becomes a more interesting solution than HVAC, since reduce cable energy losses and decrease reactive power requirements. This trend towards larger OWPPs located further away from shore is posing some technical, economic and political challenges that must be overcome to be fully competitive in the longer term compared to other energy sources. Today, there is an important concern about reducing the current Levelised Cost Of Energy (LCOE) of offshore wind projects by improving system reliability and availability, reducing O&M costs and/or increasing energy generation. This thesis aims to propose novel electrical WPP concepts more cost-effective than the existing ones and to comprehensive analyse their technical and economic feasibility. Specific challenges related to the design, optimisation, modelling, operation and control of these new concepts will be addressed in the study. All the concepts presented throughout this thesis, are focused on the collector grid of an OWPP, which encompasses all the necessary equipment to collect the power generated by the wind turbines and to export it to the offshore transmission HVDC platform. The first novel WPP concept assessed can be applied to either an onshore or offshore WPP with a MVAC collection grid connected to the grid through either an HVAC or HVDC transmission link, whilst the rest of the OWPP configurations analysed are motivated by the presence of HVDC technology and its ability to electrically decouple the OWPP from the onshore power system. Thus, the first wind power plant concept evaluated consists in properly derating some specific wind turbines in order to reduce the wake effect within the collection grid and, therefore, to maximise the energy yield by the whole wind power plant during its lifetime of the installation. The following three OWPP concepts analysed arise thanks to the opportunity provided by HVDC technology to operate the collection grid at variable frequency. Thus, the second proposed OWPP concept investigated is based on removing the individual power converter of each wind turbine and connecting a synchronous generator-based OWPP (or a wind turbine cluster) to a single large power converter which operates at variable frequency. Likewise, the third OWPP configuration assessed deals with the optimisation of this aforementioned concept and with the proposal of an hybrid MVAC/MVDC OWPP concept for the offshore collection grid. Regarding the fourth OWPP design, it consists of a DFIG-based OWPP with reduced power converters (approximately 5% of rated slip) connected to a single HVDC substation. This proposal is analysed both static and dynamically by means of simulations. Finally, the last novel OWPP concept presented in this thesis deals with the analysis of an entire offshore wind power plant in DC, with the aim of reducing the losses both in the inter-array and the export cable(s). In general terms, all the novel OWPP concepts analysed suggest a good potential to be applied to future offshore wind power plants by reducing in all the cases the LCOE in comparison with the existing OWPPs.La energía eólica marina es un sector emergente que se encuentra en plena expansión. Múltiples circunstancias tales como que cada vez sea más difícil encontrar lugares propicios en tierra (principalmente en Europa) para la instalación de parques eólicos, que a medida que el parque se aleja de la costa el impacto visual y auditivo es menor y que en el mar el viento sopla con más intensidad y de una manera más constante que en tierra, lo cual posibilita obtener una mayor generación de energía eólica, han provocado que cada vez existan más parques eólicos marinos. Hoy en día, factores medioambientales y sociales están obligando a construir los parques eólicos marinos cada vez más alejados de la costa y se espera que esta tendencia continúe en los próximos años. Varios estudios han demostrado que a partir de una cierta distancia crítica entre el parque eólico y su punto de conexión a tierra (aproximadamente 55-70 km), la transmisión mediante alta tensión en corriente continua (ATCC) resulta una opción más interesante que a través de una transmisión en alta tensión de corriente alterna (ATCA), ya que las pérdidas en los cables se ven reducidas, así como los requerimientos de potencia reactiva. Esta tendencia hacia construir parques eólicos marinos cada vez mayores y a ubicarlos más alejados de la costa, supone el tener que resolver ciertos retos técnicos, económicos y políticos a fin de poder ser más competitivos en el futuro en comparación con otras fuentes de generación de energía. Hoy en día existe una importante preocupación por tratar de reducir el elevado coste actual de la energía para los proyectos de eólica marina a base de mejorar la fiabilidad y disponibilidad del sistema, reducir costes de operación y mantenimiento y/o incrementar la generación de energía. Esta tesis tiene como objetivo proponer conceptos eléctricos novedosos, aplicados a parques eólicos marinos, que resulten más rentables que los existentes actualmente. Asimismo, esta tesis pretende analizar de una manera exhaustiva la factibilidad, tanto técnica como económica, de dichos conceptos. Asuntos tales como el diseño, la optimización, el modelaje, la operación y el control son presentes en la tesis. El alcance del trabajo se focaliza en la zona colectora de un parque eólico y, por lo tanto, no se analiza, el sistema de transmisión ni su integración a la red. Dicha zona comprende todo el equipamiento necesario para recolectar la potencia generada por los aerogeneradores y transmitirla a la plataforma marina de ATCC. El primer concepto innovador de parque eólico evaluado puede ser aplicado tanto en parques situados en tierra como en el mar, que tengan una red colectora interna de corriente alterna en media tensión (MTCA) y un sistema de transmisión tanto ATCC o ATCA. Respecto al resto de configuraciones presentadas, estas vienen motivadas por la presencia de la tecnología ATCC y su capacidad para desacoplar eléctricamente la red interna del parque eólico del sistema eléctrico de potencia situado en tierra. Así pues, la primera propuesta de parque eólico a analizar consiste en operar algunas máquinas concretas por debajo de su punto óptimo de operación a fin de poder reducir el efecto estela dentro del parque y poder así maximizar la potencia total extraída por el mismo. Las tres siguientes configuraciones de parque analizadas se fundamentan en la posibilidad que ofrece la tecnología ATCC de poder operar la red interna del parque eólico a una frecuencia variable. En base a este nuevo concepto, la segunda propuesta de parque investigada consiste en prescindir de los convertidores individuales de cada turbina y conectar todos los generadores síncronos del parque eólico (o un simple grupo de máquinas) directamente al convertidor central, el cual opera a frecuencia variable. El tercer diseño de parque eólico se basa en una topología híbrida dentro del parque combinado MTCA y MTCC. Esta configuración surge de optimizar la propuesta anterior de parque eólico. Asimismo, la cuarta propuesta a analizar estudia la posibilidad de tener un parque consistente en generadores de inducción doblemente alimentados conectados a un convertidor común de tensión controlada situado en la plataforma marina, en el cual los convertidores de cada máquina sean de un tamaño menor a lo habitual (aproximadamente a un deslizamiento nominal de un 5%). Este sistema es analizado en detalle tanto estática como dinámicamente. Finalmente, el último concepto que se presenta en esta tesis analiza la posibilidad de considerar un parque eólico marino completamente (transmisión y red interna del parque) constituido mediante tecnología en CC, con el fin de poder reducir las pérdidas tanto en la red interna del parque como en el cable de exportación. En términos generales se puede concluir que todos los conceptos propuestos a lo largo de esta tesis sugieren un gran potencial para poder ser aplicados en futuros parques eólicos marinos, ya que su coste de energía se ve reducido en comparación con los parques eólicos existentes hoy en día

Modelización dinámica y control de un aerogenerador de velocidad variable con una máquina de inducción doblemente alimentada en PSS/E

Hoy en d a, debido a la creciente penetraci on de la energ a e olica en la red el ectrica, los Operadores del Sistema de Transmisi on (TSO) se han visto obligados a revisar los requerimientos de conexi on a la red (Grid Codes), con el n de garantizar una correcta calidad de la energ a, tanto a nivel de abilidad como de estabilidad. As pues, para asegurar el correcto funcionamiento de los parques existentes y de los futuros, se requieren modelos din amicos ables y detallados, que permitan reproducir faltas con la su ciente exactitud como para veri car la idoneidad de estos. A tal n, en este proyecto se desarrolla un modelo din amico mediante el programa de simulaci on PSSTME. Dicho modelo comprende un aerogenerador de velocidad variable, de aspas orientables, y con generador de inducci on doblemente alimentado (DFIG). El dise~no del control se lleva a cabo a dos niveles: a alto nivel (control de velocidad o extracci on de m axima potencia del viento y control de pitch) y a bajo nivel (control del convertidor mediante la t ecnica del control vectorial). Adicionalmente, se a~nade al dise~no de control una regulaci on de frecuencia para el control de su estabilidad. Finalmente, se simulan unas situaciones de inter es con el modelo completo y se veri ca que se cumpla con los nuevos requisitos que imponen los TSO

Partitioning approach for large wind farms: active power control for optimizing power reserve

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Nowadays, large wind farms are expected to guarantee stability of the electrical grid contributing with ancillary services, such as frequency support. To this end, wind farm controllers must set the power generation of each turbine to compensate generation and demand imbalances. With the aim of optimizing primary frequency support, this paper proposes a partitioning approach to split large wind farms into several disjoint subsets of turbines according to the wake propagations through the wind farm. The partitioning problem is solved as a mixed-integer multi-objective optimization problem stated to maximize the strength of the coupling among the turbines due to the wake effect. Thus, no additional information sharing related to the wake propagations needs to be considered between the subsets. Different control tasks are assigned to the local controller of each subset, such that the total power generated meets the power demanded by the grid while the power reserve for enhancing primary frequency support is maximized. Finally, as an application of the proposed model, a decentralized wind farm control strategy is designed and compared with a centralized approach.Peer ReviewedPostprint (author's final draft

The influence of different wind and wave conditions on the energy yield and downtime of a Spar-buoy floating wind turbine

Floating offshore wind turbines (FOWT) have been extensively proven in model tests and are reaching currently a pre-commercial phase where large scale demonstrators are being built offshore. This transition increases the need for models able to assess the performance at suitable offshore locations. A simplified model is proposed that computes the dynamic response of FOWT to different met-ocean conditions and calculates the energy production considering the behavior of the structure as well as the downtime of the turbine due to exceeding operating limits. The model is validated against FAST and applied to three offshore sites. The motions response and hub acceleration are largest for West of Barra followed by Gulf of Maine and Costa Brava. The energy generation is also the highest at West of Barra, where a capacity factor of 75% is reached. A comparison between the energy generation of a bottom-fixed and FOWT indicates a difference of less than 1% for all sites. Finally, a sensitivity analysis of hub acceleration and platform pitch limits studies the impact on the capacity factor and downtime. The model can be useful for feasibility or pre-engineering studies and can be of interest for both investigators and developers of offshore wind projects.Peer ReviewedPostprint (author's final draft

Collection grid optimization of a floating offshore wind farm using particle swarm theory

Floating substructures for offshore wind turbines is a promising solution in order to harness the vast wind potential of deep water sites where bottom-fixed turbines are not feasible. The electrical system of large scale floating offshore wind farms will experience the application of new technologies and installation procedures that likely affect the cost-competitiveness. Thus, in this work, an optimization model based on the particle swarm theory is presented that allows optimizing the collection grid of a floating offshore wind farm. The developed model is applied to a study case consisting of a 500MW floating offshore wind farm located at the Golfe de Fos in the Mediterranean Sea. The resulting layout allows to reduce the total cost of the collection grid by more than 6% and to decrease the energy losses by 8% compared to the actual layout. Besides this, a further study analyzes the effect of a quantity discount with a reduced number of power cable cross sections.Postprint (published version

DFIG-based offshore wind power plant connected to a single VSC-HVDC operated at variable frequency: Energy yield assessment

The existence of HVDC (High Voltage Direct Current) transmission systems for remote offshore wind power plants allows devising novel wind plant concepts, which do not need to be synchronized with the main AC grid. This paper proposes an OWPP (offshore wind power plant) design based on variable speed wind turbines driven by DFIGs (doubly fed induction generators) with reduced power electronic converters connected to a single VSC-HVDC converter which operates at variable frequency and voltage within the collection grid. It is aimed to evaluate the influence of the power converter size and wind speed variability within the WPP on energy yield efficiency, as well as to develop a coordinated control between the VSC-HVDC converter and the individual back-to-back reduced power converters of each DFIG-based wind turbine in order to provide control capability for the wind power plant at a reduced cost. To maximise wind power generation by the OWPP, an optimum electrical frequency search algorithm for the VSC-HVDC converter is proposed. Both central wind power plant control level and local wind turbine control level are presented and the performance of the system is validated by means of simulations using MA'FLAB/Simulink (R). (C) 2015 Elsevier Ltd. All rights reserved.Postprint (author’s final draft

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Modelización dinámica y control de un aerogenerador de velocidad variable con una máquina de inducción doblemente alimentada en PSS/E

Hoy en d a, debido a la creciente penetraci on de la energ a e olica en la red el ectrica, los Operadores del Sistema de Transmisi on (TSO) se han visto obligados a revisar los requerimientos de conexi on a la red (Grid Codes), con el n de garantizar una correcta calidad de la energ a, tanto a nivel de abilidad como de estabilidad. As pues, para asegurar el correcto funcionamiento de los parques existentes y de los futuros, se requieren modelos din amicos ables y detallados, que permitan reproducir faltas con la su ciente exactitud como para veri car la idoneidad de estos. A tal n, en este proyecto se desarrolla un modelo din amico mediante el programa de simulaci on PSSTME. Dicho modelo comprende un aerogenerador de velocidad variable, de aspas orientables, y con generador de inducci on doblemente alimentado (DFIG). El dise~no del control se lleva a cabo a dos niveles: a alto nivel (control de velocidad o extracci on de m axima potencia del viento y control de pitch) y a bajo nivel (control del convertidor mediante la t ecnica del control vectorial). Adicionalmente, se a~nade al dise~no de control una regulaci on de frecuencia para el control de su estabilidad. Finalmente, se simulan unas situaciones de inter es con el modelo completo y se veri ca que se cumpla con los nuevos requisitos que imponen los TSO

A simplified model for the dynamic analysis and power generation of a floating offshore wind turbine

This paper presents a simplified model for the dynamic analysis of a floating off-shore wind turbine (FOWT), which can be suitable for early feasibility and pre-engineering studies, where the complete system has to modeled in order to predict its behavior and to assess the performance. The model solves the equation of motion in time domain and considers Morison equation for computing the hydrodynamic loads. The aerodynamic loads are included by considering the wind thrust at hub height and the loads from the mooring system have been computed as a non-linear model. A methodology is also presented for calculating the structural properties of the system. The model is tested for two load cases and compared to results obtained with the more complex model FAST. The comparison between the response of the models is satisfactory. The simplified model allows to capture the main motions of the FOWT with an acceptable accuracy. A further feature of the model is to calculate the power generation of the floating wind turbine. The results show that the losses in comparison with a bottom-fixed off-shore wind turbine are below 1% or 1.1% according to the load case, which confirms the good performance of the studied FOWT