HGO based Stator Side Converter Control with Reduced Current Sensors of RT-DFIG for WECS

Model-based speed estimation, a well-known mechanical sensorless control method, implements FOC in a doubly fed induction generator (DFIG) based wind energy conversion system (WECS) in both stator-tied and rotor-tied configurations. High gain observers (HGO) are popular due to their stable exponential convergence, resistance to parametric variations, and ease of deployment with a fixed gain parameter. A minimum of four to six current sensors mounted on rotor and stator terminals are required for rotor-tied DFIG (RT-DFIG) HGO design. An alternative HGO design for mechanical speed estimation is proposed in this paper. It enables RT-DFIG sensorless FOC control with only two current sensors. Since fewer physical components are required to complete the system, complexity and cost are reduced. The elimination of two existing sensors improves hardware reliability. The proposed algorithm uses only two stator current sensors. The proposed reduced sensor HGO architecture is tested in Matlab/Simulink for both static and dynamic wind conditions. Compared to the existing HGO design, this HGO with a reduced sensor performs well under diverse operating conditions.