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Increasing levels of wind power penetration in modern power systems has set intensively high standards with respect to wind turbine technology during the last years. Security issues have become rather critical and operation of wind farms as conventional power plants is becoming a necessity as wind turbines replace conventional units on the production side. This article includes a review of the basic control issues regarding the capability of the Doubly Fed Induction Generator (DFIG) wind turbine configuration to fulfill the basic technical requirements set by the system operators and contribute to power system security. An overview of ancillary services provided by wind turbine technology nowadays is provided, i.e. , fault ride-through capability, reactive power supply and frequency-active power control.

This report treats risk assessment of siting wind turbines close to highways in Denmark. The assessment only deals with the risk of total or partly failure of the turbines and the risk of ice throw from the blades. The report describes the fundamental methods, risk assessments as well as the assumptions and limitations the results are based on. The results is based on an example with a number of turbines sited alone the highway and presented as the risk per driven km on the highway. This report treats risk assessment of siting wind turbines close to highways in Denmark. The assessment only deals with the risk of total or partly failure of the turbines and the risk of ice throw from the blades. The report describes the fundamental methods, risk assess-ments as well as the assumptions and limitations the results are based on. The results is based on an example with a number of turbines sited alone the highway and presented as the risk per driven km on the highway.

System imbalance due to power fluctuation is the first concern of power grid with large scale wind power integration. Traditional studies are limited in time domain, where the modeling is not convenient enough. In this paper, a model based on frequency domain is proposed. This model is more precise, and capable to take some important factors, such as the layout of wind farm, into account. This paper also presents a fast engineering implementation of this model, which can be applied on different power system studies. The case studies show this model can perfectly evaluate the ramp rate and reserve requirement of power systems, no matter under normal or extreme weather condition, therefore the validity and flexibility of this model get proved.

This is the final report of a Danish research project “Grid fault and design-basis for wind turbines”. The objective of this project has been to assess and analyze the consequences of the new grid connection requirements for the fatigue and ultimate structural loads of wind turbines. The fulfillment of the grid connection requirements poses challenges for the design of both the electrical system and the mechanical structure of wind turbines. The development of wind turbine models and novel control strategies to fulfill the TSO’s requirements are of vital importance in this design. Dynamic models and different fault ride-through control strategies have been developed and assessed in this project for three different wind turbine concepts (active stall wind turbine, variable speed doublyfed induction generator wind turbine, variable speed multipole permanent magnet wind turbine). A computer approach for the quantification of the wind turbines structural loads caused by the fault ride-through grid requirement, has been proposed and exemplified for the case of an active stall wind turbine. This approach relies on the combination of knowledge from complimentary simulation tools, which have expertise in different specialized design areas for wind turbines. In order to quantify the impact of the grid faults and grid requirements fulfillment on wind turbines structural loads and thus on their lifetime, a rainflow and a statistical analysis for fatigue and ultimate structural loads, respectively, have been performed and compared for two cases, i.e. one when the turbine is immediately disconnected from the grid when a grid fault occurs and one when the turbine is equipped with a fault ride-through controller and therefore it is able to remain connected to the grid during the grid fault. Different storm control strategies, that enable variable speed wind turbines to produce power at wind speeds higher than 25m/s and up to 50m/s without substantially increasing the structural loads, have also been proposed and investigated during the project. Statistics in terms of mean value and standard deviation have been analysed and rainflow calculations have been performed to estimate the impact over the lifetime of a variable speed wind turbine.

The final report for IEA Wind Task 23, Offshore Wind Energy Technology and Deployment, is made up of two separate reports: Subtask 1: Experience with Critical Deployment Issues and Subtask 2: Offshore Code Comparison Collaborative (OC3). The Subtask 1 report included here provides background information and objectives of Task 23. It specifically discusses ecological issues and regulation, electrical system integration and offshore wind, external conditions, and key conclusions for Subtask 1. The Subtask 2 report covers OC3 background information and objectives of the task, OC3 benchmark exercises of aero-elastic offshore wind turbine codes, monopile foundation modeling, tripod support structure modeling, and Phase IV results regarding floating wind turbine modeling.

This report investigates the impact of wind power in large power systems. The motivation for this investigation is the ever-increasing wind energy penetration into the power systems throughout the world. A generic large power system model delivered by the Danish Transmission System Operator EnergiNet.dk is used in the presented study cases.

Reliability of offshore wind production under extreme wind conditions was investigated in this report. The wind power variability from existing and future large offshore wind farms in Western Denmark were simulated using the Correlated Wind model developed at Risø. The analysis was done for five years, with each year simulated with five random seeds, leading to a total of 25 annual wind power time series for six large offshore wind farms, summing up to a little over 330 wind turbines. Two storm control strategies were used. The analysis involved several aspects inspired from reliability studies. The aspects investigated are storm events occurrences and durations, storm control strategy impact on the capacity factor (lost production), the loss of production (power produced from wind drops below a certain threshold due to high wind speeds and storm controller) and finally, the wind power production ramp rates and reserves requirements.

Autonomous power systems are characterized by the absence of interconnections with neighbouring systems due to geographical, economic and political reasons. These systems face particular problems associated with safety and reliability during the design and operation procedure associated with safety and reliability. Typical problems include large variations in frequency because of the low inertia and the large fluctuations voltage due to the low short circuit ratio. The quality of the provided electricity to consumers is threatened. At the same time, special features of non interconnected systems, such as concentration of production in a limited number of power stations, the large size of the units in relation to the load, the need for larger spinning reserve due to the absence of interconnections, and the small stability margins raise the impact on safety and cost of operation. Under these conditions, the effective handling of transient phenomena arising due to serious disorders is particularly critical. The systems should respond adequately to dynamic events and ensure static and dynamic safety. The most common faults that may cause undesired events are the loss of transmission lines, the sudden loss of load, and short circuits – especially three phase errors – and loss of production units. Based on collected operational data, incidents of loss of unit during operation are quite common and cause serious problems, therefore require special treatment. In several cases, such events have led in the past in smaller or even general black-outs. These problems are becoming more intense due to the increasing penetration of wind power in the last decade. Since renewable energy sources and particularly wind energy have stochastic behaviour, the power output is not guaranteed. This is the main factor that imposes restrictions on the expansion because in general, distributed energy sources do not contribute to the control and regulation of the system in the same way as conventional units. Another important point, which differentiates the turbines compared with conventional synchronous generators used in electric systems, is associated with the technology of converting mechanical energy into electrical. The wind turbines are in large proportion