Due to the increasing penetration of fluctuating distributed generation electrical grids require reinforcement, in order to secure a grid operation in accordance with given technical specifications. This grid reinforcement often leads to over-dimensioning of the distribution grids. Therefore, traditional and recent advances in distribution grid planning are analysed and possible alternative applications with large scale battery storage systems are reviewed. The review starts with an examination of possible revenue streams along the value chain of the German electricity market. The resulting operation strategies of the two most promising business cases are discussed in detail, and a project overview in which these strategies are applied is presented. Finally, the impact of the operation strategies are assessed with regard to distribution grid planning.
The German Energy Transition puts enormous pressure on the existing grid operation and planning. At the same time, battery technology is developing rapidly and has the potential to reduce stress on the grid and increase the profitability of renewable energies if implemented in a market that provides sufficient revenues. The motivation behind this paper was to take most recent developments in the price of battery storage systems (BSS) and analyze if the primary control reserve market (CRM) could yield a profitable investment. Moreover, three different battery technologies, namely Lead-Acid (LAB), Lithium-Ion (LIB) and Vanadium Redox Flow (VRB), were investigated. Both the prequalification guidelines for the markets, and the technology’s abilities were examined. Afterwards, the complete life cycle costs were calculated and compared to the potential revenues generated through the CRM by calculating the net present value (NPV) over the BSS’s lifetime. The conclusion yields a clear picture of a recommendable technology and whether it is mature to be implemented.
Decarbonisation in the generation of electricity is necessary to reduce fossil fuel consumption, the pollution emitted and to meet the Energy Technology Perspectives 2 ¿C Scenario (2DS) targets. Small islands are not exempt from this target, so this study’s emphasis is placed on a 50-50 target: to reduce the fossil fuel consumption through electricity generation from Renewable Energy Sources (RES) to cover 50% of all electric demand by 2050 on small islands. Using Cozumel Island, Mexico, as a case study, this analysis will be based on three factors: economical, technical, and land-use possibilities of integrating Renewable Energy Technologies (RETs) into the existing electrical grid. This analysis is made through long-term statistical models. A deterministic methodology is used to perform time-series simulations. The selection of the best system was made on the basis of a Dimensional Statistical Variable (DSV) through primary and secondary category rankings. The presented methodology determines the best systems for capturing the initial capital cost and competitiveness of this new proposal compared with the current system of electricity generation on the Island, and can be applied to small islands as well. According to the results, all systems proposed are able to completely satisfy the renewable electricity needed by 2050 in all scenarios. From the 12 system proposals that were compared, two systems, System 2 and System 7, were chosen as eligible systems to be installed. The Levelized Cost of Energy (LCOE) result for System 2 was 0.2518 US$/kWh and for System 7 was 0.2265 US$/kWh by 2018 in the Base Scenario. Meanwhile, the Internal Rate of Return (IRR) value fluctuated from 17.2% for System 2 to 31% for System 7.
The recent increase of intermittent power generation plants connected to the electric power grids may stress the operation of power systems. So, grid codes started considering these power plants should con- tribute to the grid support functions. Recently, a power ramp rate limitation is being included in several grid codes, which is a challenge for photovoltaic installations due to the lack of inertia. This paper pre- sents a method to deal with the main grid code requirements considering a PV plant with an energy stor- age device, where a strict two-second time window ramp rate restriction is applied. A direct ramp rate control strategy is used, which includes a dynamic SOC control and battery support functionality for active power setpoint compliance. The control strategy is validated by simulations.
An inspiration for INVADE are the world-wide agreements on minimisation of human caused effects to climate change and energy efficiency targets set at the European Union with ambitious goals for reduction of greenhouse gas emission and for increase of renewable energy share.
To enable a higher share of renewable energy sources to the smart grid and gain a traction in the market place a few critical barriers must be overcome. There is a deficiency of 1) flexibility and battery management systems 2) exploration of ICT solutions based on active end user participation 3) efficient integration of energy storage and transport sector (EVs), 4) novel business models supporting an increasing number of different actors in the grid.
INVADE addresses these challenges by proposing to deliver a Cloud based flexibility management system integrated with EVs and batteries empowering energy storage at mobile, distributed and centralised levels to increase renewables share in the smart distribution grid. The project integrates different components: flexibility management system, energy storage technologies, electric vehicles and novel business models. It underpins these components with advanced ICT cloud based technologies to deliver the INVADE platform. The project will integrate the platform with existing infrastructure and systems at pilot sites in Bulgaria, Germany, Spain, Norway and the Netherlands and validate it through mobile, distributed and centralised use cases in the distribution grid in large scale demonstrations. Novel business models and extensive exploitation activities will be able to tread the fine line between maximizing profits for a full chain of stakeholders and optimizing social welfare while contributing to the standardization and regulation policies for the European energy market. A meaningful integration of the transport sector is represented by Norway and the Netherlands pilots – with the highest penetration of EVs worldwide.
This paper aims to detail and illustrate the operation of the LEMS during the grid-connected and grid-disconnected mode of the Smart Rural Grid (SRG) project. The SRG project is focused on DSO’s capabilities to increase the interoperability, resilience, efficiency and robustness of the existing rural distribu- tion network by the utilization of new Smart Grid technologies. This project is founded by the European Union and it is constituted by an eight partners consortium mixing their know- how in a hybrid smart solution; therefore, power electronics, control theory, telecommunications, distribution system operator energy managing, supervisory systems and end-users coexist in a pilot network. This pilot network includes four rural secondary substations up to 200 kVA interconnected by means of medium voltage rural overhead lines in Vallfogona, Catalonia, Spain. Index Terms —Intelligent power distribution router, power quality, rural distribution network, smart rural grid.
The penetration of dc networks for different applications in power systems is increasing. This paper presents a novel methodology for security-constrained optimal power flow (SCOPF) operation of a power system, such as a smart grid or a supergrid, with an embedded dc network. The methodology demonstrates that dc networks can be operated to provide support to ac systems, increasing its security of supply and resilience in case of outages, while reducing operational costs. Moreover, the outage management support can be achieved via a preventive SCOPF – i.e. the combined network stays N-1 secure after outages without need for further control action – or via a corrective SCOPF, by using the fast controls of the ac-dc converters to react to the contingencies. The methodology relies on the construction of a binary outage matrix and optimizes only the control variables of the ac and dc networks. It was successfully tested in system with 12 buses and in the IEEE30 network with 35 buses. Operational savings of up to 1% and 0.52% were obtained for the first and second networks, respectively, while network violations for the N-1 contingency scenarios were completely eliminated in the first and reduced by 70% in the former.
The electric generation systems on islands are based generally on fossil fuel. This fact and its supply make the electricity cost higher than in systems used in the continent. In this article, we present a review of the renewable energy generation systems on islands. To do it we analysed 77 islands from 45 different countries. This work will allow us to know how the implementation of renewable energy sources could help these islands in developing a renewable and sustainable energy sector, including a reduction of electricity generation cost. This paper shows the results from a study case of the application of renewable energy technology in Cozumel Island, Mexico. This Island is located in front of the Riviera Maya area. The analysis was made through long- term statistical models. A deterministic methodology was used to perform time-series simulations. The simulations shows that for the year 2050 a feasible integration of a system based on wind/PV can be achieved on the Island, reducing the electricity price from 0.37 US$/kW h to 0.24 US$/kW h (2050 scenario). With this scenario, the government will achieve its targets in renewable energy and in the reduction of the emissions of CO2. This will allow reaching a sustainable electricity sector.
BUEHNER, V.; Franz, P.; Hanson, J.; Gallart, R.; Martínez, S.; Sumper, A.; Girbau-Llistuella, F. International Council on Large Electric Systems p. 1-9 Data de presentació: 2016-08-21 Presentació treball a congrés
Significant reductions of greenhouse gas emission by use of renewable energy sources belong to the common targets of the European Union. Smart grids address intelligent use and integration of conventional and renewable generation in combination with controllable loads and storages. Two special aspects have also to be considered for smart grids in future: rural conditions and electric vehicles. Both, the increasing share of renewable energy sources and a rising demand for charging power by electrical vehicles lead to new challenges of network stability (congestion, voltage deviation), especially in rural distribution grids. This paper describes two lighthouse projects in Europe (“Well2Wheel” and “Smart Rural Grid”) dealing with these topics. The link between these projects is the implementation of the same virtual power plant technology and the approach of cellular grid cells. Starting with an approach for the average energy balance in 15 minutes intervals in several grid cells in the first project, the second project even allows the islanded operation of such cells as a microgrid. The integration of renewable energy sources into distribution grids primary takes place in rural areas. The lighthouse project “Smart Rural Grid”, which is founded by the European Union, demonstrates possibilities to use the existing distribution system operator infrastructure more effectively by applying an optimised and scheduled operation of the assets and using intelligent distribution power routers, called IDPR. IDPR are active power electronic devices operating at low voltage in distribution grids aiming to reduce losses due to unbalanced loads and enabling active voltage and reactive power control. This allows a higher penetration of renewable energy sources in existing grids without investing in new lines and transformers. Integrated in a virtual power plant and combined with batteries, the IDPR also allows a temporary islanded mode of grid cells.
Both projects show the potential of avoiding or postponing investments in new primary infrastructure like cables, transformers and lines by using a forward-looking operation which controls generators, loads and batteries (mobile and stationary) by using new grid assets like power routers.
While primary driven by physical restrictions as voltage-band violations and energy balance, these cells also define and allow local smart markets. In consequence the distribution system operators could avoid direct control access by giving an incentive to the asset owners by local price signals according to the grid situation and forecasted congestions.
Camacho, O.; Schachler, B.; Bühler, J.; Resch, M.; Sumper, A.; von Ossietzky, C. International Conference on the European Energy Market p. 1-5 DOI: 10.1109/EEM.2016.7521338 Data de presentació: 2016-06 Presentació treball a congrés
The rapidly increasing number of implemented photovoltaic (PV) systems in the German distribution grid
in recent years has led to power quality issues due to the intermittent generation and reverse power flows in periods
of low demand. In order to decrease this impact, different solutions are being investigated. The aim of this study is to
analyze the maximum possible grid relief by using residential PV storage systems and different reactive power control
strategies from the viewpoint of a distribution system owner. To compare the different voltage control method scenarios
the hosting capacity is used as a performance indicator.
Olivella, P.; Viñals, G.; Sumper, A.; R. Villafafila-Robles; Bremdal, B.; Ilieva, I.; Ottesen, S. IEEE International Energy Conference and Exhibition p. 1-6 Data de presentació: 2016-04-07 Presentació treball a congrés
Marzband, M.; Yousefnejad, E.; Sumper, A.; Dominguez, J. International journal of electrical power and energy systems Vol. 75, p. 265-274 DOI: 10.1016/j.ijepes.2015.09.010 Data de publicació: 2016-02-01 Article en revista
In this paper, an algorithm for energy management system (EMS) based on multi-layer ant colony optimization (EMS-MACO) is presented to find energy scheduling in Microgrid (MG). The aim of study is to figure out the optimum operation of micro-sources for decreasing the electricity production cost by hourly day-ahead and real time scheduling. The proposed algorithm is based on ant colony optimization (ACO) method and is able to analyze the technical and economic time dependent constraints. This algorithm attempts to meet the required load demand with minimum energy cost in a local energy market (LEM) structure. Performance of MACO is compared with modified conventional EMS (MCEMS) and particle swarm optimization (PSO) based EMS. Analysis of obtained results demonstrates that the system performance is improved also the energy cost is reduced about 20% and 5% by applying MACO in comparison with MCEMS and PSO, respectively. Furthermore, the plug and play capability in real time applications is investigated by using different scenarios and the system adequate performance is validated experimentally too. (C) 2015 Elsevier Ltd. All rights reserved.
This paper analyses, from a steady state point of view, the potential benefit of a Wind Power Plant (WPP) control strategy whose main objective is to maximise its total energy yield over its lifetime by taking into consideration that the wake effect within the WPP varies depending on the operation of each wind turbine. Unlike the conventional approach in which each wind turbine operation is optimised individually to maximise its own energy capture, the proposed control strategy aims to optimise the whole system by operating some wind turbines at sub-optimum points, so that the wake effect within the WPP is reduced and therefore the total power generation is maximised. The methodology used to assess the performance of both control approaches is presented and applied to two particular study cases. It contains a comprehensive wake model considering single, partial and multiple wake effects among turbines. The study also takes into account the Blade Element Momentum (BEM) theory to accurately compute both power and thrust coefficient of each wind turbine. The results suggest a good potential of the proposed concept, since an increase in the annual energy captured by the WPP from 1.86% up to 6.24% may be achieved (depending on the wind rose at the WPP location) by operating some specific wind turbines slightly away from their optimum point and reducing thus the wake effect. (C) 2015 Elsevier Ltd. All rights reserved.
de Prada, M.; Igualada , L.; Corchero, C.; Gomis-Bellmunt, O.; Sumper, A. IEEE transactions on power systems Vol. 30, num. 4, p. 1868-1876 DOI: 10.1109/TPWRS.2014.2354457 Data de publicació: 2015-07-01 Article en revista
The aim of this paper is to present a hybrid AC-DC offshore wind power plant (OWPP) topology and to optimize its design in order to minimize the OWPP's total cost. This hybrid concept is based on clustering wind turbines and connecting each group to an AC/DC power converter installed on a collector platform which is located between the AC wind turbine array and the HVDC offshore platform. Thereby, individual power converters of each wind turbine are not required, since such AC/DC converters can provide variable speed generator control for each cluster. The optimal design for an OWPP based on the hybrid AC-DC topology is formulated as a MINLP problem. The capital costs of each component within the OWPP as well as the costs associated to the inherent losses of this topology are minimized. The optimal number of AC/DC converters and offshore collector platforms needed, as well as their locations, are determined. The cable route connecting the wind turbines between each other is also optimized. The results suggests a good potential for the hybrid AC-DC OWPP topology achieving a total cost saving of 3.76% for the case study compared to the conventional OWPP topology.
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.
Díaz, F.; Hau, M.; Sumper, A.; Gomis-Bellmunt, O. International journal of electrical power and energy systems Vol. 68, p. 313-326 DOI: 10.1016/j.ijepes.2014.12.062 Data de publicació: 2015-06-01 Article en revista
This work assesses the participation of wind power plants in primary frequency control support. To participate in frequency control-related tasks, the wind power plants have to maintain a certain level of power reserves. In this article, the wind power plant is equipped with a flywheel-based storage system to fulfil the power reserve requirements set by the network operator. The article focuses on two main aspects: the definition of the control strategy to derate the wind turbines to provide a part of the required power reserves; and the coordinated regulation of the power reserves of the wind turbines and the flywheels while participating in primary frequency control. This coordinated regulation enables the wind power plant to maintain the net level of power reserves set by the network operator while alleviating the need of deloading the wind turbines. The performance of the proposed control schemes are shown by simulation. (C) 2015 Elsevier Ltd. All rights reserved.
Electric Vehicles (EVs) have seen significant growth in sales recently and it is not clear how power systems will support the charging of a great number of vehicles. This paper proposes a methodology which allows the aggregated EV charging demand to be determined. The methodology applied to obtain the model is based on an agent-based approach to calculate the EV charging demand in a certain area. This model simulates each EV driver to consider its EV model characteristics, mobility needs, and charging processes required to reach its destination. This methodology also permits to consider social and economic variables. Furthermore, the model is stochastic, in order to consider the random pattern of some variables. The model is applied to Barcelona’s (Spain) mobility pattern and uses the 37-node IEEE test feeder adapted to common distribution grid characteristics from Barcelona. The corresponding grid impact is analyzed in terms of voltage drop and four charging strategies are compared. The case study indicates that the variability in scenarios without control is relevant, but not in scenarios with control. Moreover, the voltages do not reach the minimum voltage allowed, but the MV/LV substations could exceed their capacities. Finally, it is determined that all EVs can charge during the valley without any
negative effect on the distribution grid. In conclusion, it is determined that the methodology presented allows the EV charging demand to be calculated, considering different variables, to obtain better accuracy in the results.
Bullich, E.; Sumper, A.; R. Villafafila-Robles; Joan Rull-Duran; J. Rull; J. Rull-Duran IEEE transactions on power delivery Vol. 30, num. 2, p. 674-683 DOI: 10.1109/TPWRD.2014.2312077 Data de publicació: 2015-04-01 Article en revista
Lightning is considered one of the main causes of faults in overhead distribution networks. Direct strokes usually lead to flashovers due to the insulation levels that are used. Induced overvoltages caused by indirect lightning are usually lower and can be efficiently reduced by metal-oxide surge arresters. Hence, its associated flashover rate can be reduced. In this paper, a heuristic method is proposed to optimize the number of surge arresters as well as their locations. The method presented is based on genetic algorithms and an economic approach is taken into account by means of evaluating the cost of insulation flashover.
This article investigates the combined low voltage (LV) and medium voltage (MV) residential grid impact for slow and fast electric vehicle (EV) charging, for an increasing local penetration rate and for different residential slow charging strategies. A realistic case study for a Flemish urban distribution grid is used, for which three residential slow charging strategies are modeled: uncoordinated charging, residential off-peak charging, and EV-based peak shaving. For each slow charging strategy, the EV hosting capacity is determined, with and without the possibility of fast charging, while keeping the grid within its operating limits. The results show that the distribution grid impact is much less sensitive to the presence of fast charging compared to the slow charging strategy. EV-based peak shaving results in the lowest grid impact, allowing for the highest EV hosting capacity. Residential off-peak charging has the highest grid impact, due the load synchronization effect that occurs, resulting in the lowest EV hosting capacity. Therefore, the EV users should be incentivized to charge their EVs in a more grid-friendly manner when the local EV penetration rate becomes significant, as this increases the EV hosting capacity much more than the presence of fast charging decreases it.
Low-voltage Microgrids can be valuable sources of ancillary services for the Distribution System Operators (DSOs). The aim of this paper was to study if and how multimicrogrids can contribute to Voltage Control (VC) in mediumvoltage distribution grids by means of reactive power generation and/or absorption. The hierarchical control strategy was proposed with the main focus on the tertiary control which was defined as optimal power flow problem. The interior-point algorithm was applied to optimise experimental benchmark grid with the presence of Distributed Energy Resources (DERs). Moreover, two primary objectives were formulated: active power losses and amount of reactive power used to reach the voltage profile. As a result the active power losses were minimised to the high extent achieving the savings around 22% during entire day.
La red eléctrica tradicional, gracias al aumento de la generación
distribuida, la irrupción de la electrónica de potencia y las avanzadas
tecnologías de la información y comunicación, está evolucionando hacia
las futuras redes inteligentes, formadas por numerosas microrredes
independientes, autogestionadas y capaces de proporcionar una mayor
calidad de potencia a un menor coste económico e impacto ambiental.
La red eléctrica tradicional, gracias al aumento de la generación distribuida, la irrupción de la electrónica de potencia y las avanzadas tecnologías de la información y comunicación, está evolucionando hacia
las futuras redes inteligentes, formadas por numerosas microrredes independientes, autogestionadas y capaces de proporcionar una mayor calidad de potencia a un menor coste económico e impacto ambiental.
La estructura del sistema eléctrico debe cambiar, de forma que la
energía pueda ser guardada cuando haya disponibilidad y consumida
cuando haya demanda. La capacidad de obtener un sistema que pueda
ser gobernado bajo estas reglas está cada vez más cerca gracias a la
evolución de las baterías. La posibilidad de almacenar energía eléctrica
en cantidades aceptables está también incidiendo en el cambio de
otros hábitos de consumo, como la implantación del vehículo eléctrico,
posibilitando un uso más limpio y eficiente de la energía.
Large synchronous generators with high temperature superconductors are in constant development due to their advantages such as weight and volume reduction and the increased efficiency compared with conventional technologies. The offshore wind turbine market is growing by the day, increasing the capacity and energy production of the wind farms installed and increasing the electrical power for the electrical generators installed, consequently raising the total volume and weight for the electrical generators installed. The HTS synchronous generators (HTSSG) are an alternative to consider due to their low dimensions and low weight per megawatt. This article presents a detailed review of the geometric configurations of the large HTSSG for offshore wind energy followed by an explanation of the main non-conventional technological parts. Additionally, the experience from the most important projects - both ongoing and completed - by companies and research institutes related to the design and construction of HTSSG for offshore wind energy is reviewed. (C) 2014 Elsevier Ltd. All rights reserved.
Both performance optimization and scheduling of the distributed generation (DG) are relevant implementing an energy management system (EMS) within Microgrid (MG). Furthermore, optimization methods need to be applied to achieve maximum efficiency, improve economic dispatch as well as acquiring the best performance. This paper proposes an optimization method based on gravitational search algorithm to solve such problem in a MG including different types of DG units with particular attention to the technical constraints. This algorithm includes the implementation of some variation in load consumption model considering accessibility to the energy storage (ES) and demand response (DR). The proposed method is validated experimentally. Obtained results show the improved performance of the proposed algorithm in the isolated MG, in comparison with conventional EMS. Moreover, this algorithm which is feasible from computational viewpoint, has many advantages as peak consumption reduction, electricity generation cost minimization among other. (C) 2014 Elsevier Ltd. All rights reserved.
Armero, P.; Galceran-Arellano, S.; Bergas, J.; Sumper, A.; Gomis-Bellmunt, O.; Sudria, A. International Congress on Education, Innovation and Learning Technologies p. 1-3 Data de presentació: 2014-07-24 Presentació treball a congrés
The module CDMtek-DS is a standalone module with which the student can learn how to program a microcontroller or a digital signal processor and interact with the peripherals included in the module. It also includes a CAN transceiver to get into the industrial communications world. This module is intended to be used with the CDMtek-PM to build a complete platform for motion control.
The aim of this paper is to analyse, from the technical and economic point of view, the suitability of a proposed Offshore Wind Power Plant (OWPP) scheme based on removing the individual power converters of each wind turbine and connecting a turbine cluster (or an entire WPP) to a single large power converter (SLPC), by means of a centralised control. This proposed concept is specially worthwhile for HVDC interfaced offshore or remote WPPs where a common power converter (LCC or VSC) is required at the connection point of the wind farms. According to this approach, two WPP topologies are studied depending on whether the SLPC operates at variable or constant frequency (SLPC-VF or SLPC-CF). A detailed methodology to assess any WPP layout under any wind condition is presented and applied to a case study. In order to obtain accurate results, a wake model considering single, partial and multiple wakes within a WPP is considered. The implemented algorithm takes into account the steady-state and maintenance (preventive and corrective) energy losses, as well as investment and operation and maintenance (O&M) costs, to provide a precise technical and economic assessment of each WPP topology analysed. Due to the uncertainty of certain parameters, a sensitivity analysis varying the cost and efficiency of the individual power converters of each wind turbine, as well as the main economic indicators, has been performed. The results obtained suggests a good potential for the SLPC-VF scheme achieving a total cost saving of up to 6% compared to the conventional WPP topology, based on individual power converters connected to each turbine. Likewise, the effectiveness of implementing an optimum electrical frequency calculation algorithm for variable frequency operation within the WPP is demonstrated as a greater economic benefit can be realised for SLPC-VF instead of SLPC-CF scheme. (C) 2014 Elsevier Ltd. All rights reserved.
La energía eólica marina es un sector emergente que se encuentra en plena expansión. Cada vez existen más parques eólicos marinos, tanto en Europa como en el resto del mundo, principalmente debido a 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. Además, el hecho de que los parques eólicos marinos no padezcan tantas limitaciones de espacio permite poder instalar turbinas de mayor potencia y tamaño. 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 cierto 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 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 red interna de un parque eólico y no se analiza, el sistema de transmisión ni su integración a la red. El primer concepto de parque eólico evaluado puede ser aplicado tanto en parques situados en tierra como en el mar, que tengan una red interna de CA en media tensión (MTCA) y un sistema de transmisión tanto ATCC o ATCA. Respecto al resto de configuraciones presentadas, éstas 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 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. Los tres siguientes diseños de parque se fundamentan en la posibilidad que ofrece la tecnología ATCC de poder operar la red interna del parque a una frecuencia variable. Así pues, se propone estudiar la posibilidad de considerar parques eólicos donde se eliminan o se reducen los convertidores de cada turbina gracias a disponer del convertidor central situado en la subestación marina, el cual ejerce un control centralizado a todo el parque. Finalmente, el último concepto presentado en esta tesis analiza la posibilidad de considerar un parque eólico marino completamente en CC (transmisión y red interna del parque), a fin de poder reducir las pérdidas tanto en la red interna como en el cable de exportación.En términos generales se concluye 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.
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.
Active power reserves are needed for the proper operation of an electrical system. These reserves are continuously regulated in order to match the generation and consumption in the system and thus, to maintain a constant electrical frequency. They are usually provided by synchronized conventional generating units such as hydraulic or thermal power plants. With the progressive displacement of these generating plants by non-synchronized renewable-based power plants (e.g. wind and solar) the net level of synchronous power reserves in the system becomes reduced. Therefore, wind power plants are required, according to some European Grid Codes, to also provide power reserves like conventional generating units do. This paper focuses not only on the review of the requirements set by Grid Codes, but also on control methods of wind turbines for their participation in primary frequency control and synthetic inertia.
La incorporación de altos niveles a generación distribuida no despachable a pequeña escala está causando la transición de los tradicionales sistemas eléctricos de potencia 'verticales' a los sistemas de potencia 'operados horizontalmente', en donde dichas redes de distribución pueden contener tanto generación como consumos de carácter estocástico (p. ej. La recarga de vehículos eléctricos). Este hecho incrementa el número de variables estocásticas y las dependencias entre estas de forma considerable. Los análisis determinísticos no son suficientes para lidiar con estos nuevos factores y se necesita enfocar el problema de otro modo. Los análisis probabilísticos proporcionan una mejor manera de abordar la situación.Esta tesis describe el impacto de la recarga de vehículos eléctricos (para los cuales se ha usado un modelo detallado para las curvas de carga y descarga de sus baterías) en la red eléctrica. El método probabilístico Monte Carlo se ha aplicado a una red de equiparable a una red distribución española donde también se han considerado patrones de movilidad de vehículos (en este caso de la ciudad de Barcelona). Para llevar a cabo los análisis, en primer lugar se ha adaptado una red de estudio de IEEE con los parámetros de la red de distribución española. A continuación se ha modelado el comportamiento de las baterías de los vehículos eléctricos a partir de las características de baterías de modelos reales de vehículos eléctricos que ya están en el mercado. Finalmente, se han considerado diferentes estrategias de control en el momento de realizar la recarga de vehículos eléctricos.A partir de los datos obtenidos se han generado modelos estadísticos tanto para los consumos domésticos de la red como para la recarga de los vehículos eléctricos. Con dichos modelos se ha llevado a cabo un análisis Monte Carlo para estudiar los niveles de carga tanto de líneas como de transformadores. Los resultados obtenidos demuestran la importancia del correcto modelado de las baterías ya que se aumenta la precisión de los análisis. Adicionalmente, los patrones de movilidad de la zona a estudiar han demostrado ser clave en este tipo de estudio.
The incorporation of high levels of small-scale non-dispatchable distributed generation is leading to the transition from the traditional 'vertical' power system structure to a 'horizontally-operated' power system, where the distribution networks contain both stochastic generation and load (such as electric vehicles recharging). This fact increases the number of stochastic inputs and dependence structures between them need to be considered. The deterministic analysis is not enough to cope with these issues and a new approach is needed. Probabilistic analysis provides a better approach.
This PhD thesis describes the grid impact analysis of charging electric vehicles (EV) using charging curves with detailed battery modelling. A probabilistic method using Monte Carlo was applied to a typical Spanish distribution grid, also using mobility patterns of Barcelona. To carry out this analysis, firstly, an IEEE test system was adapted to a typical distribution grid configuration; secondly, the EV and its battery types were modeled taking into account the current vehicle market and the battery characteristics; and, finally, the recharge control strategies were taken in account.
Once these main features were established, a statistical probabilistic model for the household electrical demand and for the EV charging parameters was determined. With these probabilistic models, the Monte Carlo analysis was performed within the established scenario in order to study the lines' and the transformers' loading levels. The results show that an accurate model for the battery gives a more precise estimation about the impact on the grid. Additionally, mobility patterns have been proved to be some of the most important key aspects for these type of studies.
This paper deals with the design and the experimental validation in scale-lab test benches of an energy management algorithm based on feedback control techniques for a flywheel energy storage device. The aim of the flywheel is to smooth the net power injected to the grid by a wind turbine or by a wind power plant. In particular, the objective is to compensate the power disturbances produced by the cycling torque disturbances of the wind turbines due to the airflow deviation through its tower section. This paper describes the control design, its tuning, as well as the description of the experimental setup, and the methods for the experimental validation of the proposed concepts. Results show that the fast wind power fluctuations can be mostly compensated through the flywheel support.
The Smart_Rural_Grid project is aimed at developing an innovative smart grid approach targeted to the particular conditions of rural electricity distribution networks. The project will devote particular attention to highlight the differentiated specificities of rural electricity distribution and will target the need of gaining substantial improvements in terms of efficiency, quality and network resilience, favouring the introduction of new innovative business models in support of rural DSO's operations and of their future economic and industrial sustainability.\nBy exploring the convergence between electricity and telecom networks, the project is focused on the needs and visions for the future of DSOs' with rural networks, and intends to face a systemic development of rural smart grids aimed at allowing DSOs to operate more efficiently, integrate local renewable electricity sources, interconnect prosumers and increase and guarantee the quality of electricity supply by allowing forming resilient and manageable electricity islands. The project will pave the way for new industrial opportunities for the production and deployment of new industrial products (systems and devices) as well as services for electricity distribution and network management and control, framed by a novel improved electricity distribution network management architecture.\nThe project key impacts are directly related with the delivery of significant cost and investment savings in rural electricity distribution (by overall reducing the percentage of electricity lost during electricity distribution and the gap between electricity generated and electricity consumed) also allowing for an increase potential to inherently accommodate the integration and distribution of renewable electricity sources and Combined Heat and Power (CHP), particularly of those connected to the distribution grid and of locally co-generated electricity (including prosumers) generated in vast rural territories.