Voltage Fluctuations Produced by the Fixed-Speed Wind Turbines during Continuous Operation. European Perspective

Since wind energy begun to have importance in some countries, several authors from different countries have presented in international publications the influence of such injection of energy over the power quality in the electrical power system. Since the concept of wind turbine employed at that time was mostly the asynchronous generator directly connected to the grid, the problems originated by the fluctuations in the power output of these generators (and therefore in the voltage, resposible of the flicker phenomenon) began to be a matter of concern for the scientific community. In Europe the Agencies and Universities in the Northern countries have pioneered the study of power quality of wind turbines and the problems of their integration into the grid. The collaboration between these agencies and universities has enabled their joint participation in the project funded by the Fourth Framework Program of the European Union "European Wind Turbine Testing Procedure Developments", completed in 2001 (Sorensen et al., 1999). This project provided cover for the then emerging standard IEC 61400-21.