Operation Region of Doubly Fed Induction Generators Based on Rotor Slip under Maximum Power Point Tracking Control and Power Dispatch

Abstract Quantification to the operation region of wind turbine generators is critical for them to participate in active/reactive power dispatch and frequency/voltage control, functioning similarly to the synchronous generators. Although it is well known that operation region of doubly fed induction generators is decided by the current/capacity limits of the stator, rotor, and grid-side converter, it is found in this article that the operation region consists of a cluster of curves based on rotor slips and is thus related to wind speeds and control modes. The slip affects both reactive power capability and active power range. The solution to slip for maximum power point tracking control and power dispatch modes is proposed, including rotor speed limit and power flow constraints. Numerical results show that under the maximum power point tracking mode, higher wind speed yields lower rotor slip and a wider operation region. Under the power dispatch mode, pitch angle regulation yields the same operation region, while different power settings correspond to different VAR capabilities; rotor speed regulation yields different slips and operation regions. When keeping other conditions the same for power dispatch, the pitch angle regulation yields a larger operation region than rotor speed regulation.