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2009
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IEEE Transactions on Power Systems, 2007
This paper deals with power fluctuations from wind farms. The time range in focus is between one minute and up to a couple of hours. In this time range, substantial power fluctuations have been observed during unstable weather conditions. A wind power fluctuation model is described, and measured time series from the first large offshore wind farm, Horns Rev in Denmark, are compared to simulated time series. The comparison between measured and simulated time series focuses on the ramping characteristics of the wind farm at different power levels and on the need for system generation reserves due to the fluctuations. The comparison shows a reasonable agreement between simulations and measurements, although there is still room for improvement of the simulation model.
Wind Energy, 2008
This paper deals with modelling of power fluctuations from large wind farms. The modelling is supported and validated using wind speed and power measurements from the two large offshore wind farms in Denmark. The time scale in focus is from 1 min to a couple of hours, where significant power fluctuations have been observed from these wind farms. Power and wind speed are measured with 1 s sampling time in all individual wind turbines in almost 1 year, which provides a substantial database for the analyses. The paper deals with diversified models representing each wind turbine individually and with aggregation of a wind farm to be represented by a single large wind turbine model.
Journal of Wind Engineering and Industrial Aerodynamics, 2002
This paper presents a wind model, which has been developed for studies of the dynamic interaction between wind farms and the power system to which they are connected. The wind model is based on a power spectral description of the turbulence, which includes the coherence between wind speeds at different wind turbines in a wind farm, together with the effect of rotational sampling of the wind turbine blades in the rotors of the individual wind turbines. Both the spatial variations of the turbulence and the shadows behind the wind turbine towers are included in the model for rotational sampling. The model is verified using measured wind speeds and power fluctuations from wind turbines. r
The inclusion of wind power in power systems is steadily increasing around the world. This incorporation is forcing the utilities to assess its influence on the dynamics of power systems. Therefore, it is important to evaluate the information resulting from models that simulate the dynamic interaction between wind farms and the power systems they are connected to. Such models allow performing the necessary preliminary studies before connecting wind farms to the grid. The purpose of this paper is to show by means of simulations the voltage fluctuations caused by a wind farm linked to a weak power system. A model for dynamic performance of wind farms is presented. Moreover, a wind speed model and a wind turbine model are briefly presented. The results of the effects of the wind farm on the grid performance are shown in a testing power system through different settings.
2001
A dynamic model of the wind farm Hagesholm has been implemented in the dedicated power system simulation program DIgSILENT. The wind farm consists of six 2MW NM2000/72 wind turbines from NEG-Micon. The model has been verified using simultaneous power quality measurements on the 10 kV terminals of a single wind turbine and power performance measurements on two wind turbines. The verification shows a generally good agreement between simulations and measurements, although the simulations at higher wind speeds seem to underestimate the power and voltage fluctuations. A way to improve the simulation at higher wind speeds is suggested. This report has passed the internal review performed by Peter Hauge Madsen Frede Blaabjerg ISBN 87-550-2912-4 ISBN 87-550-2913-2 (Internet) ISSN 0106-2840 Print: Pitney Bowes Management Services Denmark A/S, 2001 Risø-R-1281(EN) 3
Renewable Energy, 2011
A spatial and temporal analysis of wind power generation characteristics was conducted in order to determine the implications of intermittent wind generation dynamics on the profile of the electric loads that must be balanced by dispatchable electrical generators on the electric grid. A parametric analysis was conducted to evaluate the sensitivity of the typical magnitudes of wind power fluctuations on different timescales, power variation range, typical daily and seasonal wind profiles to wind farm size and regional distribution. A methodology to evaluate wind dynamics based on power spectral density analyses have been developed. Results indicate that increasing the size of a local wind farm significantly reduced the magnitude of wind power fluctuations on timescales faster than 12 h, with the largest reductions occurring at the fastest timescales. Additional reductions in power fluctuations can be achieved with the implementation of local and regional distribution of wind turbines in disperse high wind areas. In these cases, it was discovered that the timescale band within which the largest reductions in power fluctuations occurred was dependent on regional geographic features, and did not necessarily correspond to the fastest timescales. In addition, it was also discovered that the aggregation of wind power from different regions could produce a more uniform frequency distribution of power fluctuation reductions.
Wind Energy, 2005
Studies of the effects that wind power production imposes on the power system involve assessing the variations of large-scale wind power production over the whole power system area. Large geographical spreading of wind power will reduce variability, increase predictability and decrease the occasions with near zero or peak output. In this article the patterns and statistical properties of large-scale wind power production data are studied using the data sets available for the Nordic countries. The existing data from Denmark give the basis against which the data collected from the other Nordic countries are benchmarked. The main goal is to determine the statistical parameters describing the reduction of variability in the time series for the different areas in question. The hourly variations of largescale wind power stay 91%-94% of the time within ±5% of installed capacity in one country, and for the whole of the Nordic area 98% of the time. For the Nordic time series studied, the best indicator of reduced variability in the time series was the standard deviation of the hourly variations. According to the Danish data, it is reduced to less than 3% from a single site value of 10% of capacity.
2007 IEEE Power Engineering Society General Meeting, 2007
Power Systems, IEEE Transactions on, 2007
In this paper a wind park dynamic model is presented together with a base methodology for its application to power system studies. This detailed wind generation model addresses the wind turbine components and phenomena more relevant to characterize the power quality of a grid connected wind park, as well as the wind park response to the grid fast perturbations, e.g. low voltage ride through fault. The developed model was applied to the operating conditions of the selected sets of wind turbine experimental benchmark data from Azores and Alsvik wind parks, both for steady and transient operation of the grid. The results show a fairly good agreement in the relevant range of frequencies and indicate the model may be used as a tool for power system studies.
IEEE Transactions on Power Systems, 2007
In Denmark, incorporation of wind power into the power system is increasing whereas power generation from the large conventional power plants is reducing. The common concern has become maintenance of reliable and stable operation of the Danish power system with a large amount of wind power-the large wind power system. At present, maintaining the voltage stability of such a large wind power system relies on strong ac connections to neighboring power systems with sufficient reactive power and voltage control and on control of central power plants in Denmark. This paper presents the results of a stability investigation carried out by the Danish transmission system operator (TSO), Energinet.dk, for the case of almost island operation of the Western Danish wind power system. The main ac lines connecting Western Denmark to the synchronous area of the Union for the Coordination of Transmission of Electricity (UCTE) were out of service and the wind power generation was high. The investigation has shown that the reactive power and voltage control of the domestic power plants is essential for maintaining short-term voltage stability of the Western Danish wind power system and becomes even more relevant when ac connections to the strong transmission system of the UCTE are out of service. The results presented in this paper may also be relevant for the operators of the power systems that are in island ac operation and with plans for significant commissioning of wind power-Great Britain, Ireland, Tasmania, etc.
7th International Workshop on Large Scale …, 2008
In this paper, the impact of the wind time variability and the spatial smoothing effect in mountainous complex terrains, usually taken as 1/sqrt(N) for fast fluctuations, is studied. The dimension of the regions, the type of electrical clustering of large numbers of wind turbines and the local meteorological effects are addressed and conclusions drawn on selected experimental case studies.
Every passing day wind energy becomes more indispensable part of power systems. So this increasing require the analysis of wind turbine impact on the grid. In this study, possible effect of wind turbine which is connected to Turkish distribution grid are analyzed. Distribution grid system is modeled with NEPLAN power system analysis simulator program. Finally, results are presented.
2004
The thesis first presents the basics influences of wind power on the power system stability and quality by pointing out the main power quality issues of wind power in a small-scale case and following, the expected large-scale problems are introduced. Secondly, a dynamic wind turbine model that supports power quality assessment of wind turbines is presented. Thirdly, an aggregate wind farm model that support power quality and stability analysis from large wind farms is presented. The aggregate wind farm model includes the smoothing of the relative power fluctuation from a wind farm compared to a single wind turbine. Finally, applications of the aggregate wind farm model to the power systems are presented. The power quality and stability characteristics influenced by large-scale wind power are illustrated with three cases. In this thesis, special emphasis has been given to appropriate models to represent the wind acting on wind farms. The wind speed model to a single wind turbine includes turbulence and tower shadow effects from the wind and the rotational sampling turbulence due to the rotation of the blades. In a park scale, the wind speed model to the wind farm includes the spatial coherence between different wind turbines. Here the wind speed model is applied to a constant rotational speed wind turbine/farm, but the model is suitable to variable speed wind turbine/farm as well. The cases presented here illustrate the influences of the wind power on the power system quality and stability. The flicker and frequency deviations are the main power quality parameters presented. The power system stability concentrates on the voltage stability and on the power system oscillations. From the cases studied, voltage and the frequency variations were smaller than expected from the large-scale wind power integration due to the low spatial correlation of the wind speed. The voltage quality analysed in a Brazilian power system and in the Nordel power system from connecting large amount of wind power showed very small voltage variations. The frequency variations analysed from the Nordel showed also small variations in the frequency but it also showed that the wind turbines excites the power system in the electromechanical modes. Concerning the stability analysis, the study cases showed that large-scale wind power modifies the voltage stability of the power system and can cause power oscillations. It is showed here that the reactive power from the wind farms is the key factor on the voltage stability problem. During continuous operation, the distributed wind power variations did not give any problems to the power system stability concerning the power oscillations. v
Wind Energy, 2005
Owing to an increasing penetration of wind turbines and large wind farms in electrical power systems, the wind turbines start influencing the overall power system behaviour. Dynamic wind farm models for power system studies have been presented in Part 1 of the article. In this contribution, these models are applied in a number of case studies to determine the impact of wind farms on the power grid. Four turbine concepts are evaluated with respect to their grid interaction. Case studies involving normal behaviour, voltage dip behaviour, voltage control capability and behaviour during frequency deviations will be presented.
2008
Short-term power fluctuations from wind farms may affect interconnected-grid operating costs and stability. With the increasing availability of wind power worldwide, this has become a concern for some utilities. Under electric industry restructuring in the United States, the impact of these fluctuations will be evaluated by examining provisions and costs of ancillary services for wind power. However, the magnitude of the impact and the effect of aggregation of multiple turbines are not well quantified due to a lack of actual wind farm power data. This paper analyzes individual turbine and aggregate power output data from the German "250-MW Wind" data project. Electric system load following and regulation impacts are examined as a function of the number of turbines and turbine spacing in order to quantify the impacts of aggregation. The results show a significant decrease in the relative system regulation burden with increasing number of turbines, even if the turbines are in close proximity.
Wind Energy, 2007
The power system of Denmark is characterized by significant incorporation of wind power. Presently, more than 20% of the annual electricity consumption is covered by electricityproducing wind turbines. The largest increase in grid-incorporated wind power is expected to come from large (offshore) wind farms operating as large wind power plants with ridethrough solutions, connected to the high-voltage transmission system and providing ancillary services to the system. In Denmark there are presently two offshore wind farms connected to the transmission system: Horns Rev A (160 MW rated power in the western part of the country) and Nysted (165 MW rated power at Rødsand in Eastern Denmark). The construction of two more offshore wind farms, totalling 400 MW by the years 1. Averaged over 1 year, the implemented ensemble technique has a potential of at least 20% better forecasts of wind power compared with a single forecast. 36 V. Akhmatov et al.
2001
A dynamic model of the wind farm Hagesholm has been imple-mented in the dedicated power system simulation program DIgSILENT. The wind farm consists of six 2MW NM2000/72 wind turbines from NEG-Micon. The model has been verified using simultaneous power ...
2008
Short-term power fluctuations from wind farms have the potential to negatively affect interconnected grid operational costs and stability. With wind power growing at a rapid pace worldwide, this has become an increasing concern. In the context of electric industry restructuring in the U.S., these fluctuations are evaluated by examining costs and provisions for ancillary services. However, the magnitude of the
IEEE Transactions on Energy Conversion, 2004
In this paper, a wind energy converter (WEC) model for the analysis of power fluctuations at an isolated wind plant is presented. The model includes the drive train dynamics, a firstorder model for the asynchronous generator, and the power controller. The influence of each element is studied, and the conditions that can provoke oscillations in the power delivered by the WEC are considered. A set of measurements carried out during the setting of an isolated wind plant in the Canary Islands (Spain) is the basis for this study. In these measurements, an oscillatory behavior has been observed when wind speed was high.
2007
Page 1. Fluctuations of offshore wind generation - Statistical modelling P. Pinson∗, LEA Christensen, H. Madsen Informatics and Mathematical Modelling, Technical University of Denmark, R. Petersens Plads, Lyngby, Denmark ...
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