Modified Speed Sensor-less Grid Connected DFIG based WECS

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This paper presents a new Phase Locked Loop (PLL) based slip speed estimator for speed sensor less field oriented vector control operation of variable speed grid connected Wind Energy Conversion System (WECS). Three phase rotor current is used to design a PLL based slip estimator for speed sensor-less vector control operation of rotor side converter. The proposed speed sensor-less grid connected Double Fed Induction Generator (DFIG) based WECS is used for decoupled control of stator active and reactive power to ensure maximizing the power generation at unity power factor under varying wind speed. The speed sensor-less Vector control scheme is also incorporated with an optimal speed tracking controller for maximum energy capture in the rated wind speed range and restrict the mechanical output power to the rated value using pitch angle control when the wind velocity crosses rated limit to prevent overloading and outage of the wind turbine. The proposed method does not require the information of rotor speed or position for speed sensor less DFIG based WECS unlike other published methods. Simulation has been carried out in MATLAB/Simulink environment and results have been analyzed. Results show that the proposed speed sensor-less DFIG system can operate at its optimum energy level for a wide range of wind speed and is capable for satisfactory operation of the variable speed WECS.