Mining and utilization of reactive power capability of doubly fed induction generator systems for wind turbines

In practical operation, the DFIG systems have large free margin of power capacity which can be used for reactive power adjustment, which is often neglected. Mining and utilization of the reactive power capability of doubly fed induction generator systems for wind turbines are investigated in this paper. A mathematical model for steady state performance of DFIG WT is presented to analysis of the power characteristic and its control in DFIG systems. The limiting range of reactive power capacity of DFIG and physical limitations in reactive power production are derived in details. A simulation example that dispersing the DFIG WT at the end of an distribution network is given, of which reactive power control strategy, load variation and the change of wind speed are also taken into account. In this case, the voltage level of access point is improved, which demonstrates the validity of utilization of reactive power capability of DFIG WT as an additional continuous reactive power source for utilities.