Reduced-Order State Observer-Based Feedback Control Methodologies for Doubly Fed Induction Machine

In this paper, a reduced order state observer for doubly fed induction generator (DFIG) is designed that estimate the states just using stator voltage and power measurements. Further, the proposed state observer is used to provide two control strategies for rotor side converter: 1) state estimator based state feedback control; and 2) state estimator based vector control. The state observer and controllers were tested for varying wind conditions using a full-order dynamic model with a real-time simulation platform. First, the proof-of-concept is verified on a grid integrated DFIG considering aggregated grid model represented by an infinite bus. Then, the architecture is validated on a modified IEEE 39-bus system connected with a wind farm. The results confirm that the proposed state observer coupled with existing control for DFIG provides better tracking of the system output without the need for feedback measurements, and at the same time reduces the controller design complexity. Also, these state estimator based controllers eliminate the need of rotor current sensors.