Transient stability studies in grids with great wind power penetration. Modelling issues and operation requirements

Two main issues are addressed in this paper. First, models for dynamic studies are described, justifying simplifications that cannot be performed for other studies, such as power quality studies. Variable speed wind turbines (with doubly fed induction generator), very widely used nowadays, require also an adequate modelling of the control system, according to the time constants and integration step that are used in transient stability studies. Secondly, transient stability studies involving wind energy conversion systems are presented. These studies include fixed speed and variable speed devices, and several situations on the grid are considered. The results are compared and conclusions are drawn out from them. The problem of the required protections is addressed, in relation with the requirements of connection standards for wind energy conversion systems. These subjects are applied to the Spanish situation, where a great amount of wind penetration is foreseen for the next years.