Wind Power Variability and Singular Events

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.

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.

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.

Journal of Solar Energy Engineering, 2003

The National Renewable Energy Laboratory (NREL) started a project in 2000 to record long-term, high-frequency (1-Hz) wind power data from large commercial wind power plants in the Midwestern United States. Outputs from about 330 MW of installed wind generating capacity from wind power plants in Lake Benton, MN, and Storm Lake, Iowa, are being recorded. Analysis of the collected data shows that although very short-term wind power fluctuations are stochastic, the persistent nature of wind and the large number of turbines in a wind power plant tend to limit the magnitude of fluctuations and rate of change in wind power production. Analyses of power data confirms that spatial separation of turbines greatly reduces variations in their combined wind power output when compared to the output of a single wind power plant. Data show that high-frequency variations of wind power from two wind power plants 200 km apart are independent of each other, but low-frequency power changes can be highly correlated. This fact suggests that time-synchronized power data and meteorological data can aid in the development of statistical models for wind power forecasting.

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.

2005

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.

IEEE Instrumentation & Measurement Magazine, 2014

2007 IEEE Power Engineering Society General Meeting, 2007

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

Wind Power, 2010

Source: Wind Power, Book edited by: S. M. Muyeen, ISBN 978-953-7619-81-7, pp. 558, June 2010, INTECH, Croatia, downloaded from SCIYO.COM www.intechopen.com Wind Power 290

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.

Wind Turbines, 2011

Electric power is a very unusual product. It must be constantly available for the customers but its massive storage is not possible. Therefore, electric power needs to be generated as it is used. Furthermore, it is usually generated far from the customers. All these factors make it difficult to control and assure the quality of electric power. There is no procedure that allows the removal of the poor electric power. Consequently, it is necessary to define preventive and monitoring procedures that guarantee a minimum level of power quality and hence the correct behavior of the equipment connected to the power distribution system. Perfect power quality means that the voltage is continuous and sinusoidal with a constant amplitude and frequency. Low-frequency conducted disturbances are the main defects that could compromise power quality. These are classified in the following groups: harmonics and interharmonics, voltage dips and short supply interruptions, voltage unbalance, power frequency variations and voltage fluctuations or flicker. In the last years the use of wind farms and other distributed power generation systems has drastically increased. The question that needs to be raised is how those new generation systems will affect to the whole grid. A portion of the answer must be obtained from the impact that they have on the power quality. In principle, wind energy can be considered a risky source in terms of power quality. Moreover, when wind turbines are part of the grid the power, quality seems to be a complex issue which highly depends on the interaction between the grid and the wind turbines. The main impact on the grid by the wind turbines, concerning power quality, is related to voltage changes and fluctuations, harmonic content, power peaks and flicker. The presence of these disturbances is determined by meteorological conditions and by the technical features of the wind turbine: continuously variable output power due to wind shear, tower shadow or turbulences; performance of electrical components such as generators and transformers; aerodynamic and mechanical behavior of the rotor.. . The power quality of the wind turbines must be certified on the basis of measurements performed according to international standards and guidelines. On one hand, the IEC 61400-21 standard is the reference normative for the certification of the power quality of wind turbines (IEC-61400-21 Ed. 2.0, 2008). The first edition was published in 2001 and it specifies the main relevant features of power quality that should be measured in a wind turbine. This standard establishes the procedures for the measurement and assessment of power quality characteristics of grid-connected wind turbines. According to it, measurements should be performed for harmonic content, flicker, voltage drops as well as active and reactive power, during normal and switching operations. To obtain those characteristics, the measurements should be made on the basis of long time-series of current and voltage, always depending on 24 www.intechopen.com 2.1 Current harmonics, interharmonics and higher frequency components Voltage and current harmonics are usually present on the utility network. Non-linear and electronic loads, rectifiers and inverters, are some sources which produce harmonic content. The effects of the harmonics include overheating, faulty operation of protections, equipment failures or interferences with communication systems. The standard specifically defines different procedures to assess the harmonics, interharmonics and higher frequency components for a wind turbine working under continuous conditions and operating with reactive power as close as possible to zero. This means that, if applicable, 548