Improvement of energy conversion efficiency and damping of wind turbine response in grid connected DFIG based wind turbines

摘要

This paper examines dynamic performance of DFIG based wind turbine regarding torsional electromechanical oscillations when the wind turbine is controlled in power control mode. In the power control mode, the stator active power is set to its reference value, where the reference active power is determined based on a predefined power-speed curve. Torsional oscillations associated with the poorly torsional modes may reduce the aerodynamic efficiency, deteriorate the power quality and increase stresses on the drive train system. The paper indeed analytically investigates the drive train dynamics for different operating regions of the power-speed curve. It is shown that under some operating points, torsional oscillations are well damped and the DFIG control improves the damping of torsional modes. On the other hand, at some regions of the power-speed curve, the DFIG control does not provide significant damping action on the torsoinal modes. Then a wind turbine stabilizer (WTS) is implemented to suppress torsional vibrations in the drive train system. The role of the WTS is to add positive damping to the generator rotor oscillations by controlling the active power and providing a component of electrical torque proportional to the rotor speed deviations. (C) 2017 Elsevier Ltd. All rights reserved.