DFIG modelling and the relevance of model simplification

There has been a fast growing demand for the application of doubly fed induction generators (DFIG) in wind power plants in recent years. They have in particular dominated the market in last two years. DFIG is an ideal candidate to satisfy the requirements of the recently proposed challenging grid codes. However, many uncertainties still exist or at least there are no published reports regarding validated comprehensive DFIG models. This paper attempts to clarify the existing ambiguities in modelling of DFIG under various operating conditions. The paper deals with detailed modelling of DFIG in stator-flux oriented reference frame using vector control algorithm. The model includes the current controllers for the rotor-side and grid-side converter. It investigates the influence of various subsystems (including model simplifications) on DFIG simulation results using the power system analysis package DIgSILENT PowerFactory. It also suggests appropriate control strategies for a selected set of network operating conditions and topologies.