In this paper, we develop a simulation procedure to generate realistic, synthetic wind speed vari... more In this paper, we develop a simulation procedure to generate realistic, synthetic wind speed variates for wind parks. These wind variates are defined by their marginal Weibull distributions and their auto-and cross-correlations only. In order to deal with these two types of correlation simultaneously, a vector autoregressive (VAR) model is used. Power output variates are obtained by applying the nonlinear turbine power curves to the correlated wind speed samples. The complete procedure is illustrated through a numerical example with a few turbines. A comparison is established between real wind time series from a wind park and synthetic wind variates simulated with similar, estimated underlying parameters.
... Ferreira de Jesus IST – Instituto Superior Técnico (Technical University of Lisbon) Av. Rovis... more ... Ferreira de Jesus IST – Instituto Superior Técnico (Technical University of Lisbon) Av. Rovisco Pais, 1049–001 Lisboa, Portugal Tel: 351 1 841 72 87, Fax: 351 1 841 74 21, e-mail: [email protected] ABSTRACT When assessing the interaction between wind parks and the ...
The incorporation of clean energy sources in the power system is a topic of discussion almost eve... more The incorporation of clean energy sources in the power system is a topic of discussion almost everywhere. After the “Wind (farms) of change”, small, dispersed, urban photovoltaic (PV) generators are being installed in the roofs of the buildings, connected to the local Low Voltage (LV) grid. A boost in this type of renewable micro generation is expected in the near future. Due to the domestic loads, LV grids are inherently unbalanced, its analysis requiring the use of three-phase load flow (...)
Given the increasing penetration of wind energy in the power system, not only at a national, but ... more Given the increasing penetration of wind energy in the power system, not only at a national, but also global level, the need for the scientific and academic community to better understand this technology is rapidly growing. For that purpose, the effort of several international entities has greatly contributed, with the creation of generic models capable of accurately representing the multitude of wind turbine generators, WTGs, available in the present-day market. These models can be of type 1, 2, 3 or 4 (A, B, C or D in some literature), depending on the generator’s topology and grid interface. This article focuses on the type 3 generic model, WT3, which represents a WTG composed of a doubly-fed induction generator, DFIG, equipped with an AC/DC/AC power converter connecting the rotor to the grid and the stator directly connected to the grid. This being the most used technology nowadays. The work was developed in MATLAB based on an academic program for dynamic simulations of electric...
This paper aims to study the basic principles and the importance of the development of a model fo... more This paper aims to study the basic principles and the importance of the development of a model for characterizing photovoltaic arrays with shaded cells. It will also include the future methodology of work and schedule, the motivation and definition of the problem under study. Photovoltaic energy is one of the fastest growing renewable energies in recent years. However, its production is strongly affected by the shading (total and partial) of the modules responsible for its production. This shading causes a mismatch between the cells, reducing the global production of the panel. It’s necessary to know the effects of shading in the production of energy, for different configuration of photovoltaic modules, in order to understand which is less affected and why. For this, a model for characterizing photovoltaic arrays is created, whose equivalent circuit parameters change depending on the operation conditions (irradiance and temperature). Through an analysis based on each cell that const...
The need to provide Spinning Reserve (SR), together with the need to respect some operational con... more The need to provide Spinning Reserve (SR), together with the need to respect some operational constraints, points to high power state combinations of the thermal power plants, therefore reducing the penetration of renewables in the power mix and eventually leading to wind curtailment. Water Pumped Storage Systems (WPSS) are a way to overcome this issue, by storing the surplus energy not needed in the valley periods, to use it later in peak periods. This situation is dealt with in this paper, through the proposal of an energy balance technical model, taking into account the constraints and operational limits of the thermal power plant, together with an economic model based on NPV and IRR. This model is applied to assess the Terceira Island case-study. Despite the fact that this is a simplified model, not using any optimization techniques, it was possible to conclude that WPSS provide both thermal based electricity and wind curtailment reduction, therefore facilitating the integration of renewable energy in the power system and enhancing the environmental aspects of electricity production. Moreover, it was found that there are turbine/pump sizing combinations that can turn the project into an economically viable one. Also, it was demonstrated that further economic feasibility could be achieved if SR requirements could be lowered. This aspect should be considered by Terceira system operator.
In order to reduce the high dependence on imported fuels and to meet the ongoing growth of electr... more In order to reduce the high dependence on imported fuels and to meet the ongoing growth of electricity demand, Cape Verde government set the goal to increase renewable energy penetration in Santiago Island until 2020. To help maximize renewable energy penetration, an off-stream Pumped Storage Hydropower (PSH) plant will be installed in Santiago, in one of the following locations: Chã Gonçalves, Mato Sancho and Ribeira dos Picos. This paper summarizes the studies carried out to find the optimal location and connection point of the PSH plant in Santiago's electricity network. This goal was achieved by assessing the impact of the PSH plant, in each location, on power system stability. The simulation tool PSS/E of Siemens was used to study the steady-state and dynamic behavior of the future (2020) Santiago MV grid. Different scenarios of demand and renewable resources were created. Each hydro unit of the PSH plant was modeled as an adjustable speed reversible turbine employing a DFIM. The results show that Santiago's grid with the PSH plant in Chã Gonçalves is the one that has the best performance.
It is now clear that the installation of offshore wind parks is the next step towards an even mor... more It is now clear that the installation of offshore wind parks is the next step towards an even more widespread use of wind power. In what concerns the interconnection of remote offshore wind parks to the existing onshore grid, for distances over 50 km and/or installed capacities above 100 MW, High Voltage Direct Current (HVDC) technology seems to be more adequate than High Voltage Alternating Current (HVAC). This paper addresses only the interconnection of offshore systems with the onshore grid through the HVDC technology. Two HVDC technologies are compared: HVDC using Line Commutated Converters (HVDC-LCC) and HVDC using Voltage Source Converters (HVDC-VSC). As it is known that LCC technology is unable to offer reactive power support in fault conditions, the association with a STATCOM is considered. Specific studies are performed in both steady-state and transient conditions of the grid in order to evaluate the pros and cons of each HVDC technology. The impact of the HVDC technologies in the compliance of existing grid code requirements is also assessed.
The electric power systems, which are responsible for energy transportation in the form of electr... more The electric power systems, which are responsible for energy transportation in the form of electricity, are subject to a number of disturbances such as frequency variations or voltage fluctuations. These situations can influence the power quality, bringing a negative impact to the devices that we connect to the network. An effective energy storage, such as Battery Energy Storage Systems (BESS), is able to bring to the network many advantages, not only in power quality applications that increase network security but also in energy management applications that enables efficient response to fluctuations demand and increased use of renewable energy. Batteries, as auxiliary network element, exhibit unique characteristics of performance, efficiency and versatility, especially the lithium-ion’s. The modeling of this technology is a complex process because even the battery characteristics are easily influenced by external factors. However, the chosen model intends to represent not only the ...
The main objective of this paper is to study the implementation of a battery energy storage syste... more The main objective of this paper is to study the implementation of a battery energy storage system (BESS) in order to improve the dynamic behaviour of an offshore wind farm. Special attention is given to the frequency excursions limitation in the sequence of a fault on the onshore grid. This goal is accomplished by setting up a case study in which an offshore wind farm is connected to an onshore grid through a high voltage direct current line commutated converter (HVDC-LCC) link. The Power System Simulator for Engineering (PSS/E) simulation tool is used to implement the whole system, including the onshore and offshore grids and the load flow and dynamic models of the conventional generators, the wind turbine generators (WTGs), the HVDC-LCC link and the BESS. With the BESS out of service, some protective actions of the DC link lead to the uncontrolled frequency increase of the WTG, which are consequently tripped out. The BESS proves to be essential, as it allows the offshore wind farm to keep running by maintaining the frequency of the WTG at acceptable levels and therefore bringing the entire system to a steady state operating point.
Integration of a nuclear power plant in a transmission grid with a large penetration of wind generation
… and Technology for …, 2010
... References. [1] Akhmatov, V., Hans Knudsena, Arne Hejde Nielsenb, Jørgen Kaas Pedersenb and N... more ... References. [1] Akhmatov, V., Hans Knudsena, Arne Hejde Nielsenb, Jørgen Kaas Pedersenb and Niels Kjølstad Poulsen (2003). ... [3] Sucena Paiva, JP, Ferreira de Jesus, JM, Rui Castro, Pedro Correia, João Ricardo, Reis Rodrigues, A., João Moreira and Bruno Nunes (2005). ...
A wind park reduced-order model using singular perturbations theory
Energy Conversion, IEEE …, 1996
... If one denote these fast variations by zf=z-zs and again letting E=O, will obtain the so call... more ... If one denote these fast variations by zf=z-zs and again letting E=O, will obtain the so called fast sub-system as: rox ~ ~ at ~ ~ ~ for x and z are then given by: x(t> E x,(f) (64 (6b) ... id,, iqr are respectively tor resistance and currents, and Ah, Aqs, Adr, ...
In this paper, we develop a simulation procedure to generate realistic, synthetic wind speed vari... more In this paper, we develop a simulation procedure to generate realistic, synthetic wind speed variates for wind parks. These wind variates are defined by their marginal Weibull distributions and their auto-and cross-correlations only. In order to deal with these two types of correlation simultaneously, a vector autoregressive (VAR) model is used. Power output variates are obtained by applying the nonlinear turbine power curves to the correlated wind speed samples. The complete procedure is illustrated through a numerical example with a few turbines. A comparison is established between real wind time series from a wind park and synthetic wind variates simulated with similar, estimated underlying parameters.
... Ferreira de Jesus IST – Instituto Superior Técnico (Technical University of Lisbon) Av. Rovis... more ... Ferreira de Jesus IST – Instituto Superior Técnico (Technical University of Lisbon) Av. Rovisco Pais, 1049–001 Lisboa, Portugal Tel: 351 1 841 72 87, Fax: 351 1 841 74 21, e-mail: [email protected] ABSTRACT When assessing the interaction between wind parks and the ...
The incorporation of clean energy sources in the power system is a topic of discussion almost eve... more The incorporation of clean energy sources in the power system is a topic of discussion almost everywhere. After the “Wind (farms) of change”, small, dispersed, urban photovoltaic (PV) generators are being installed in the roofs of the buildings, connected to the local Low Voltage (LV) grid. A boost in this type of renewable micro generation is expected in the near future. Due to the domestic loads, LV grids are inherently unbalanced, its analysis requiring the use of three-phase load flow (...)
Given the increasing penetration of wind energy in the power system, not only at a national, but ... more Given the increasing penetration of wind energy in the power system, not only at a national, but also global level, the need for the scientific and academic community to better understand this technology is rapidly growing. For that purpose, the effort of several international entities has greatly contributed, with the creation of generic models capable of accurately representing the multitude of wind turbine generators, WTGs, available in the present-day market. These models can be of type 1, 2, 3 or 4 (A, B, C or D in some literature), depending on the generator’s topology and grid interface. This article focuses on the type 3 generic model, WT3, which represents a WTG composed of a doubly-fed induction generator, DFIG, equipped with an AC/DC/AC power converter connecting the rotor to the grid and the stator directly connected to the grid. This being the most used technology nowadays. The work was developed in MATLAB based on an academic program for dynamic simulations of electric...
This paper aims to study the basic principles and the importance of the development of a model fo... more This paper aims to study the basic principles and the importance of the development of a model for characterizing photovoltaic arrays with shaded cells. It will also include the future methodology of work and schedule, the motivation and definition of the problem under study. Photovoltaic energy is one of the fastest growing renewable energies in recent years. However, its production is strongly affected by the shading (total and partial) of the modules responsible for its production. This shading causes a mismatch between the cells, reducing the global production of the panel. It’s necessary to know the effects of shading in the production of energy, for different configuration of photovoltaic modules, in order to understand which is less affected and why. For this, a model for characterizing photovoltaic arrays is created, whose equivalent circuit parameters change depending on the operation conditions (irradiance and temperature). Through an analysis based on each cell that const...
The need to provide Spinning Reserve (SR), together with the need to respect some operational con... more The need to provide Spinning Reserve (SR), together with the need to respect some operational constraints, points to high power state combinations of the thermal power plants, therefore reducing the penetration of renewables in the power mix and eventually leading to wind curtailment. Water Pumped Storage Systems (WPSS) are a way to overcome this issue, by storing the surplus energy not needed in the valley periods, to use it later in peak periods. This situation is dealt with in this paper, through the proposal of an energy balance technical model, taking into account the constraints and operational limits of the thermal power plant, together with an economic model based on NPV and IRR. This model is applied to assess the Terceira Island case-study. Despite the fact that this is a simplified model, not using any optimization techniques, it was possible to conclude that WPSS provide both thermal based electricity and wind curtailment reduction, therefore facilitating the integration of renewable energy in the power system and enhancing the environmental aspects of electricity production. Moreover, it was found that there are turbine/pump sizing combinations that can turn the project into an economically viable one. Also, it was demonstrated that further economic feasibility could be achieved if SR requirements could be lowered. This aspect should be considered by Terceira system operator.
In order to reduce the high dependence on imported fuels and to meet the ongoing growth of electr... more In order to reduce the high dependence on imported fuels and to meet the ongoing growth of electricity demand, Cape Verde government set the goal to increase renewable energy penetration in Santiago Island until 2020. To help maximize renewable energy penetration, an off-stream Pumped Storage Hydropower (PSH) plant will be installed in Santiago, in one of the following locations: Chã Gonçalves, Mato Sancho and Ribeira dos Picos. This paper summarizes the studies carried out to find the optimal location and connection point of the PSH plant in Santiago's electricity network. This goal was achieved by assessing the impact of the PSH plant, in each location, on power system stability. The simulation tool PSS/E of Siemens was used to study the steady-state and dynamic behavior of the future (2020) Santiago MV grid. Different scenarios of demand and renewable resources were created. Each hydro unit of the PSH plant was modeled as an adjustable speed reversible turbine employing a DFIM. The results show that Santiago's grid with the PSH plant in Chã Gonçalves is the one that has the best performance.
It is now clear that the installation of offshore wind parks is the next step towards an even mor... more It is now clear that the installation of offshore wind parks is the next step towards an even more widespread use of wind power. In what concerns the interconnection of remote offshore wind parks to the existing onshore grid, for distances over 50 km and/or installed capacities above 100 MW, High Voltage Direct Current (HVDC) technology seems to be more adequate than High Voltage Alternating Current (HVAC). This paper addresses only the interconnection of offshore systems with the onshore grid through the HVDC technology. Two HVDC technologies are compared: HVDC using Line Commutated Converters (HVDC-LCC) and HVDC using Voltage Source Converters (HVDC-VSC). As it is known that LCC technology is unable to offer reactive power support in fault conditions, the association with a STATCOM is considered. Specific studies are performed in both steady-state and transient conditions of the grid in order to evaluate the pros and cons of each HVDC technology. The impact of the HVDC technologies in the compliance of existing grid code requirements is also assessed.
The electric power systems, which are responsible for energy transportation in the form of electr... more The electric power systems, which are responsible for energy transportation in the form of electricity, are subject to a number of disturbances such as frequency variations or voltage fluctuations. These situations can influence the power quality, bringing a negative impact to the devices that we connect to the network. An effective energy storage, such as Battery Energy Storage Systems (BESS), is able to bring to the network many advantages, not only in power quality applications that increase network security but also in energy management applications that enables efficient response to fluctuations demand and increased use of renewable energy. Batteries, as auxiliary network element, exhibit unique characteristics of performance, efficiency and versatility, especially the lithium-ion’s. The modeling of this technology is a complex process because even the battery characteristics are easily influenced by external factors. However, the chosen model intends to represent not only the ...
The main objective of this paper is to study the implementation of a battery energy storage syste... more The main objective of this paper is to study the implementation of a battery energy storage system (BESS) in order to improve the dynamic behaviour of an offshore wind farm. Special attention is given to the frequency excursions limitation in the sequence of a fault on the onshore grid. This goal is accomplished by setting up a case study in which an offshore wind farm is connected to an onshore grid through a high voltage direct current line commutated converter (HVDC-LCC) link. The Power System Simulator for Engineering (PSS/E) simulation tool is used to implement the whole system, including the onshore and offshore grids and the load flow and dynamic models of the conventional generators, the wind turbine generators (WTGs), the HVDC-LCC link and the BESS. With the BESS out of service, some protective actions of the DC link lead to the uncontrolled frequency increase of the WTG, which are consequently tripped out. The BESS proves to be essential, as it allows the offshore wind farm to keep running by maintaining the frequency of the WTG at acceptable levels and therefore bringing the entire system to a steady state operating point.
Integration of a nuclear power plant in a transmission grid with a large penetration of wind generation
… and Technology for …, 2010
... References. [1] Akhmatov, V., Hans Knudsena, Arne Hejde Nielsenb, Jørgen Kaas Pedersenb and N... more ... References. [1] Akhmatov, V., Hans Knudsena, Arne Hejde Nielsenb, Jørgen Kaas Pedersenb and Niels Kjølstad Poulsen (2003). ... [3] Sucena Paiva, JP, Ferreira de Jesus, JM, Rui Castro, Pedro Correia, João Ricardo, Reis Rodrigues, A., João Moreira and Bruno Nunes (2005). ...
A wind park reduced-order model using singular perturbations theory
Energy Conversion, IEEE …, 1996
... If one denote these fast variations by zf=z-zs and again letting E=O, will obtain the so call... more ... If one denote these fast variations by zf=z-zs and again letting E=O, will obtain the so called fast sub-system as: rox ~ ~ at ~ ~ ~ for x and z are then given by: x(t> E x,(f) (64 (6b) ... id,, iqr are respectively tor resistance and currents, and Ah, Aqs, Adr, ...
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