Improved LVRT Performance of Direct Drive Wind Turbines by Torque Limitation and DriveTrain Damping Control

Intermittent nature of wind energy conversion system (WECS) can influence the stable operation of grid and the transient events in grid system can influence the electrical and mechanical components of the wind turbines. Low voltage ride-through (LVRT) is among the important grid connection requirement for wind energy conversion systems for a stable grid. Traditionally, the wind turbine satisfies the LVRT criterion by using the braking chopper which stresses the electrical system. In this paper, a torque limitation and drivetrain damping control are proposed as an add-on feature to the traditional braking chopper control which ensures better LVRT capability without overloading the braking chopper and the mechanical system. The proposed control method is verified by using a 2 MW model of a direct wind turbine developed in MATLAB Simulink and performance is compared with conventional braking chopper and torque limitation methods.