Bullich, E.; Díaz-González, F.; Aragüés, M.; Girbau-Llistuella, F.; Olivella, P.; Sumper, A. Applied energy Vol. 212, p. 340-361 DOI: 10.1016/j.apenergy.2017.12.048 Data de publicació: 2018-02-15 Article en revista
Microgrids are considered one of the most promising solutions to integrate renewable distributed generation into the electric power system. During the last decade, the microgrid concept has been studied and developed and nowadays it is becoming a reality. Hence, in the coming years a transformation of the current electric power system to a multi-microgrid power system can be expected. In this direction, the study of multi-microgrids is currently being explored. Accordingly, this paper examines the possible multi-microgrid architectures to form a grid of microgrids. For this purpose, the microgrid as a single entity and its possible interactions with external grids is first defined. Then, the possible multi-microgrid architectures are defined in terms of layout, line technology and interface technology. Finally, a comparison between the different architectures is performed in terms of cost, scalability, protection, reliability, stability, communications and business models. This analysis is expected to be of great utility for grid planners and policy makers, who can select the most adequate architecture in function of their necessities.
Olivella, P.; Bullich, E.; Aragüés, M.; Sumper, A.; Ottesen, S.; Vidal, J.; R. Villafafila-Robles Applied energy Vol. 210, p. 881-895 DOI: 10.1016/j.apenergy.2017.08.136 Data de publicació: 2018-01-15 Article en revista
The increasing penetration of distributed energy resources in the distribution grid is producing an ever-heightening interest in the use of the flexibility on offer by said distributed resources as an enhancement for the distribution grid operator. This paper proposes an optimization problem which enables satisfaction of distribution system operator requests on flexibility. This is a decision-making problem for a new aggregator type called Smart Energy Service Provider (SESP) to schedule flexible energy resources. This aggregator operates a local electricity market with high penetration of distributed energy resources. The optimization operation problem of SESP is formulated as an MILP problem and its performance has been tested by means of the simulation of test cases in a local market. The novel problem has also been validated in a microgrid laboratory with emulated loads and generation units. The performed tests produced positive results and proved the effectiveness of the proposed solution.
Esta tesis doctoral estudia las corrientes de energización de transformadores de parques eólicos marinos con aerogeneradores con convertidores en fuente de tensión (VSC) de plena potencia conectados a través de una conexión de Alta Tensión en Corriente Continua (HVDC). Las corrientes de energización pueden disminuir la fiabilidad de la transmisión eléctrica debido a disparos intempestivos de las protecciones durante la puesta en marcha o recuperación de una falta.Para la mitigación de las corrientes de energización durante la puesta en marcha del parque esta tesis propone una nueva estrategia basada en incrementar la tensión aplicada por el convertidor del parque eólico en forma de rampa (VRS). Este método persigue energizar el parque eólico con el menor coste y máxima fiabilidad. La tesis analiza diferentes escenarios y diferentes rampas.Otro momento en que las corrientes de energización pueden dar lugar a un disparo intempestivo de las protecciones es durante la recuperación de una falta en la red de alterna del parque eólico marino. Esta tesis extiende la estrategia VRS, utilizada durante la puesta en marcha del convertidor del parque, para los escenarios de recuperación de una falta.
The present PhD thesis deals with transformer inrush current in offshore grids including offshore wind farms and High Voltage Direct Current (HVDC) transmission systems. The inrush phenomenon during transformers energization or recovery after the fault clearance is one of important concerns in offshore systems which can threaten the security and reliability of the HVDC grid operation as well as the wind farms function. Hence, the behaviour of wind turbines,Voltage Source Converters (VSC) and transformer under the normal operation and the inrush transient mode is analyzed.
For inrush current reduction in the procedure of the offshore wind farms start-up and integration into the onshore AC grid, a technique based on Voltage Ramping Strategy (VRS) is proposed and its performance is compared with the operation of system without consideration of this approach. The new methodology which is simple, cost-effective ensures minimization of transformer inrush current in the offshore systems and the enhancement of power quality and the reliability of grid under the transformer energizing condition. The mentioned method can develop much lower inrush currents according to the slower voltage ramp slopes.
Concerning the recovery inrush current, the operation of the offshore grid especially transformers is analyzed under the fault and the system restoration modes.The recovery inrush transient of transformers can cause tripping the HVDC and wind farms converters as well as disturbing the HVDC power transmission. A voltage control design based on VRS is proposed in HVDC converter to recover ali the transformers in offshore grid with lower inrush currents.The control system proposed can assure the correct performance of the converters in HVDC system and in wind farm and also the robust stability of the offshore grid.
Esta tesis doctoral estudia las corrientes de energización de transformadores de parques eólicos marinos con aerogeneradores con convertidores en fuente de tensión (VSC) de plena potencia conectados a través de una conexión de Alta Tensión en Corriente Continua (HVDC). Las corrientes de energización pueden disminuir la fiabilidad de la transmisión eléctrica debido a disparos intempestivos de las protecciones durante la puesta en marcha o recuperación de una falta. Para la mitigación de las corrientes de energización durante la puesta en marcha del parque esta tesis propone una nueva estrategia basada en incrementar la tensión aplicada por el convertidor del parque eólico en forma de rampa (VRS). Este método persigue energizar el parque eólico con el menor coste y máxima fiabilidad. La tesis analiza diferentes escenarios y diferentes rampas. Otro momento en que las corrientes de energización pueden dar lugar a un disparo intempestivo de las protecciones es durante la recuperación de una falta en la red de alterna del parque eólico marino. Esta tesis extiende la estrategia VRS, utilizada durante la puesta en marcha del convertidor del parque, para los escenarios de recuperación de una falta.
Ensuring resilient operation and control of smart grids is fundamental for empowering their deployment, but challenging at the same time. Accordingly, this study proposes a novel methodology for evaluating resilience of Information and Communication Technology (ICT) systems for smart distribution grids. Analysing how the system behaves under changing operating conditions a power system perspective allows to understand how resilient the smart distribution grid is, but the resilience of the ICT system in charge of its operation affects the overall performance of the system and does, therefore, condition its resilience. With the aim of systematising the evaluation of ICT systems’ resilience, this study proposes to combine a standardized modelling of Smart Grids, the Smart Grid Architecture Model (SGAM), with a data structured diagram, the Entity Relationship Model (ERM). The architecture of smart distribution grids is analysed through SGAM. Then, their technical characteristics and functionalities are defined and represented in a ERM diagram. Finally, the attributes or properties of the system components are used to formulate resilience indicators against different types of disturbances. This methodology is then applied to analyse the resilience of a ICT platform being developed in EMPOWER H2020 project.
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
This book discusses HVDC grids based on multi-terminal voltage-source converters (VSC), which is suitable for the connection of offshore wind farms and a possible solution for a continent wide overlay grid. HVDC Grids: For Offshore and Supergrid of the Future begins by introducing and analyzing the motivations and energy policy drives for developing offshore grids and the European Supergrid. HVDC transmission technology and offshore equipment are described in the second part of the book. The third part of the book discusses how HVDC grids can be developed and integrated in the existing power system. The fourth part of the book focuses on HVDC grid integration, in studies, for different time domains of electric power systems. The book concludes by discussing developments of advanced control methods and control devices for enabling DC grids.
Presents the technology of the future offshore and HVDC grid
Explains how offshore and HVDC grids can be integrated in the existing power system
Provides the required models to analyse the different time domains of power system studies: from steady-state to electromagnetic transients
This book is intended for power system engineers and academics with an interest in HVDC or power systems, and policy makers. The book also provides a solid background for researchers working with VSC-HVDC technologies, power electronic devices, offshore wind farm integration, and DC grid protection.
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.
Rodriguez, J.; Eduardo Prieto-Araujo; Girbau, F.; Sumper, A.; R. Villafafila-Robles; Vidal, J. Sustainable Energy, Grids and Networks Vol. 4, num. -, p. 1-15 DOI: 10.1016/j.segan.2015.07.001 Data de publicació: 2015-12 Article en revista
Current power networks are facing numerous challenges in transmission and distribution in order to accommodate distributed generation from renewables. As a result, the current grid needs to evolve towards a system with more control and resiliency. The Intelligent Power Router device, located at strategic nodes, permits to add novel functionalities. This device allows to fully control the power flow by the means of Voltage Source Converters. In this article, the operation modes of the Intelligent Power Router are proposed and discussed. Moreover, this paper presents the design of a single phase Intelligent Power Router, simulations that prove its capability to control the power flow; and finally, an experimental validation of the device operation is also offered.
Girbau, F.; Sumper, A.; Díaz-González, F.; Sudria, A.; Castro, F.; Gallart, R. Congreso Iberoamericano sobre Microrredes con Generación Distribuida de Renovables p. 64-72 Data de presentació: 2015-12-01 Presentació treball a congrés
El trabajo presentado se enmarca en e l proyecto europeo del programa FP - 7 Smart Rural Grid que tiene como objetivo desarrollar la red rural inteligente y explorar las mejores maneras de hacer la transición de las actuales redes de distribución en zonas rurales a las nuevas redes inteligentes utilizando las nuevas tecnologías y conceptos de negocio a sociados. El proyecto reconsidera la arquitectura de la red de distribución rural actual, acomodando telecomunicaciones, tecnologías de control, almacenamiento y otros sistemas y dispositivos para renovar las estructuras existentes y - probar el nuevo conce pto desarrollado , basado en incrementar entre otros, la resiliencia de la red dando lugar a una nueva estructura de red p seudomallada.
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.