Co-ordinated voltage control strategy for a doubly-fed induction generator (DFIG)-based wind farm

The penetration of wind power into electricity networks is increasing and many large wind farms use doubly-fed induction generator (DFIG) based wind turbines. A voltage control strategy for a DFIG-based wind farm is essential for compliance with some wind farm connection requirements. Such a control strategy may also have commercial benefits. This paper presents a voltage control strategy and illustrates the advantages of this methodology when applied to a DFIG implemented wind farm connected either to a transmission system or embedded within a distribution system. Dynamic linear time invariant models of the DFIG including its associated voltage source convertor and controllers are derived in the synchronous d-q reference frame. In addition, the local on-load tap changer is modelled as a finite state machine and the co-ordinated controllers for both systems are described. Simulation results are presented to illustrate the effectiveness of the controllers within both a transmission system and a distribution system.