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Research paper thumbnail of Operation and Control of Wind Farms in Non-Interconnected Power Systems

Wind Farm - Impact in Power System and Alternatives to Improve the Integration, 2011

The protection system was also modeled in the simulation platform. The settings for both under/ov... more The protection system was also modeled in the simulation platform. The settings for both under/over voltage and under/over frequency protection system are crucial for the operation and dynamic response of the system during transient instances. As mentioned in the Introduction, non interconnected system, like the one used in this report as a study case, face the problem of significant variations in voltage and frequency. The relays, which act on either the production (protection of the conventional units or protection of the wind turbines), or the demand side (relays attached on the Medium Voltage feeders) decide the disconnection of equipment or loads, when the limits set by the system operator (or the production unit user) are violated. Regarding the loads, this leads to the so called load shedding, which often determines also the dynamic security margins for the system. It is often the case, in isolated systems, with low inertia, that during frequency variations, large proportion of the load is disconnected to avoid further frequency drop and possible frequency instability, i.e. due to sudden loss of a production unit. The voltage and frequency protection system was modeled specifying the lower (or upper) limit of the value and the time duration, during which the variable measured, is out of the accepted range. One kind of under/over frequency protection operating in modern power systems is the so called ROCOF protection (Rate of Change of Frequency). The relays controlled by this system, open when the frequency changes at a rate faster than the specified one for a specific time. Thus, a part of the substation loads is disconnected. However, in many non-interconnected systems, especially those designed many decades ago, the under/over frequency protection system controlling the relays at substation loads measures the actual frequency and not the rate of change. Thus, if the frequency drops lower than a specified limit for specific time duration, the relay is ordered to open. As a case study the small size island system of Rhodes is used. Rhodes power system for the reference year 2012 includes a 150 kV transmission system, two power plants, distributed in the north and in the south, as shown in , and five wind farms. A significant proportion of the generation comes from wind turbines and diesel units. In 2012, the total installed wind power capacity and the maximum annual power demand are assumed to be about 48 MW and 233 MW, respectively (see ). The present Rhodes power system model is based on dynamic models of conventional generating units, loads and wind turbines. In order to be able to perform power system simulation studies for 2012, the present system model has to be modified with additional generating units and wind farms, which are expected to be online by the year of study, 2012, ). The protection system, mainly under/over frequency and voltage protection relay is also included in the dynamic power system model. In the reference year study 2012, five wind farms with different technologies will be connected online in Rhodes power system. depicts the wind turbine technology and the size of each wind farm.

Research paper thumbnail of Conocimientos libres, energía distribuida y empoderamiento social para un cambio de matriz energética

D. Vila-Viñas y X.E. Barandiaran (Eds.) BUEN CONOCER/FLOK SOCIETY: Modelos sostenibles y políticas públicas para una economía social del conocimiento común y abierto en el Ecuador, Jul 2015

El presente documento parte de un análisis de las políticas energéticas en Ecuador y de las neces... more El presente documento parte de un análisis de las políticas energéticas en Ecuador y de las necesidades del país en el contexto de los límites biofísicos del planeta, como base para proponer orientaciones y directrices estratégicas de política pública en el ámbito energético, así como un conjunto de casos y proyectos ilustrativos de las medidas propuestas. En particular, se consideran las condiciones para una transformación de la matriz energética del país que acompañe a la transformación productiva general, lo que implica disminuir la dependencia de los combustibles fósiles, fortalecer el rol de las energías renovables y descentralizar la producción energética, potenciando una escala productiva en la que la ciudadanía pueda pasar de ser mera consumidora de energía a participar en la producción y la gestión del sistema energético, a través de su mayor conocimiento y empoderamiento en la materia, lo
que en definitiva afecta no solo a la oferta energética, sino también a la demanda. Asimismo, son propuestas fundamentales la mejora de un conocimiento diversificado y ajustado al territorio, así como la puesta en común de los diseños y saberes técnicos al respecto.

Research paper thumbnail of Transforming the energy matrix: Transition policies for the development of the distributed energy model

Journal of Peer Production, Jul 2015

This policy paper explores the model of distributed energy as a viable alternative to centralised... more This policy paper explores the model of distributed energy as a viable alternative to centralised models. To illustrate the model, which is characterised by (a) the use of renewable energy sources, (b) the empowerment of consumers through the democratisation of the means of energy production and distribution, and (c) the communal management of the relevant infrastructure, we look at four case studies, which suggest that energy production could be more effectively organised as a Commons, rather than as a commodity. This, we conclude, should be the fundamental principle underlying all public policy proposals aimed at the transformation of the energy sector.

Research paper thumbnail of Frequency control support and participation methods provided by wind generation

The increasing wind penetration in today's power grids has led to growing interest in the frequen... more The increasing wind penetration in today's power grids has led to growing interest in the frequency control capabilities of wind generation. Several publications have assessed this subject, proposing a variety of methods both on the levels of a single turbine and of a wind farm. This paper focuses on the role of wind generation in a system's primary frequency response. Wind turbine control methods that enable frequency support and control are presented. These methods are applied to models developed in Matlab/Simulink and indicative results are presented. The advantages and disadvantages of each method are discussed.

Research paper thumbnail of Simulation of Doubly Fed Induction Generator Wind Turbines

In this paper the basic operational characteristics of a variable speed wind turbine with doubly ... more In this paper the basic operational characteristics of a variable speed wind turbine with doubly fed induction generator are investigated using the software Mathlab/Simulink, ed.7.0.1. A specific control strategy is implemented according to the vector control strategy. Both 3rd and 5 th order models of the generator were developed and the effect of neglecting the stator transients is presented under voltage dip at the generator terminals. The Low Voltage Ride-Through capability is investigated and the results of voltage dip ride-through simulations are presented.

Research paper thumbnail of Operation and Control of Wind Farms in Non-Interconnected Power Systems

Wind Farm - Impact in Power System and Alternatives to Improve the Integration, 2011

The protection system was also modeled in the simulation platform. The settings for both under/ov... more The protection system was also modeled in the simulation platform. The settings for both under/over voltage and under/over frequency protection system are crucial for the operation and dynamic response of the system during transient instances. As mentioned in the Introduction, non interconnected system, like the one used in this report as a study case, face the problem of significant variations in voltage and frequency. The relays, which act on either the production (protection of the conventional units or protection of the wind turbines), or the demand side (relays attached on the Medium Voltage feeders) decide the disconnection of equipment or loads, when the limits set by the system operator (or the production unit user) are violated. Regarding the loads, this leads to the so called load shedding, which often determines also the dynamic security margins for the system. It is often the case, in isolated systems, with low inertia, that during frequency variations, large proportion of the load is disconnected to avoid further frequency drop and possible frequency instability, i.e. due to sudden loss of a production unit. The voltage and frequency protection system was modeled specifying the lower (or upper) limit of the value and the time duration, during which the variable measured, is out of the accepted range. One kind of under/over frequency protection operating in modern power systems is the so called ROCOF protection (Rate of Change of Frequency). The relays controlled by this system, open when the frequency changes at a rate faster than the specified one for a specific time. Thus, a part of the substation loads is disconnected. However, in many non-interconnected systems, especially those designed many decades ago, the under/over frequency protection system controlling the relays at substation loads measures the actual frequency and not the rate of change. Thus, if the frequency drops lower than a specified limit for specific time duration, the relay is ordered to open. As a case study the small size island system of Rhodes is used. Rhodes power system for the reference year 2012 includes a 150 kV transmission system, two power plants, distributed in the north and in the south, as shown in , and five wind farms. A significant proportion of the generation comes from wind turbines and diesel units. In 2012, the total installed wind power capacity and the maximum annual power demand are assumed to be about 48 MW and 233 MW, respectively (see ). The present Rhodes power system model is based on dynamic models of conventional generating units, loads and wind turbines. In order to be able to perform power system simulation studies for 2012, the present system model has to be modified with additional generating units and wind farms, which are expected to be online by the year of study, 2012, ). The protection system, mainly under/over frequency and voltage protection relay is also included in the dynamic power system model. In the reference year study 2012, five wind farms with different technologies will be connected online in Rhodes power system. depicts the wind turbine technology and the size of each wind farm.

Research paper thumbnail of Conocimientos libres, energía distribuida y empoderamiento social para un cambio de matriz energética

D. Vila-Viñas y X.E. Barandiaran (Eds.) BUEN CONOCER/FLOK SOCIETY: Modelos sostenibles y políticas públicas para una economía social del conocimiento común y abierto en el Ecuador, Jul 2015

El presente documento parte de un análisis de las políticas energéticas en Ecuador y de las neces... more El presente documento parte de un análisis de las políticas energéticas en Ecuador y de las necesidades del país en el contexto de los límites biofísicos del planeta, como base para proponer orientaciones y directrices estratégicas de política pública en el ámbito energético, así como un conjunto de casos y proyectos ilustrativos de las medidas propuestas. En particular, se consideran las condiciones para una transformación de la matriz energética del país que acompañe a la transformación productiva general, lo que implica disminuir la dependencia de los combustibles fósiles, fortalecer el rol de las energías renovables y descentralizar la producción energética, potenciando una escala productiva en la que la ciudadanía pueda pasar de ser mera consumidora de energía a participar en la producción y la gestión del sistema energético, a través de su mayor conocimiento y empoderamiento en la materia, lo
que en definitiva afecta no solo a la oferta energética, sino también a la demanda. Asimismo, son propuestas fundamentales la mejora de un conocimiento diversificado y ajustado al territorio, así como la puesta en común de los diseños y saberes técnicos al respecto.

Research paper thumbnail of Transforming the energy matrix: Transition policies for the development of the distributed energy model

Journal of Peer Production, Jul 2015

This policy paper explores the model of distributed energy as a viable alternative to centralised... more This policy paper explores the model of distributed energy as a viable alternative to centralised models. To illustrate the model, which is characterised by (a) the use of renewable energy sources, (b) the empowerment of consumers through the democratisation of the means of energy production and distribution, and (c) the communal management of the relevant infrastructure, we look at four case studies, which suggest that energy production could be more effectively organised as a Commons, rather than as a commodity. This, we conclude, should be the fundamental principle underlying all public policy proposals aimed at the transformation of the energy sector.

Research paper thumbnail of Frequency control support and participation methods provided by wind generation

The increasing wind penetration in today's power grids has led to growing interest in the frequen... more The increasing wind penetration in today's power grids has led to growing interest in the frequency control capabilities of wind generation. Several publications have assessed this subject, proposing a variety of methods both on the levels of a single turbine and of a wind farm. This paper focuses on the role of wind generation in a system's primary frequency response. Wind turbine control methods that enable frequency support and control are presented. These methods are applied to models developed in Matlab/Simulink and indicative results are presented. The advantages and disadvantages of each method are discussed.

Research paper thumbnail of Simulation of Doubly Fed Induction Generator Wind Turbines

In this paper the basic operational characteristics of a variable speed wind turbine with doubly ... more In this paper the basic operational characteristics of a variable speed wind turbine with doubly fed induction generator are investigated using the software Mathlab/Simulink, ed.7.0.1. A specific control strategy is implemented according to the vector control strategy. Both 3rd and 5 th order models of the generator were developed and the effect of neglecting the stator transients is presented under voltage dip at the generator terminals. The Low Voltage Ride-Through capability is investigated and the results of voltage dip ride-through simulations are presented.