Extended chopper capability for wind turbines with doubly fed induction generator in wind farms with weak grid connection

This paper presents a methodology to extend the chopper capability for Type 3 wind turbines. Therefore, the grid side converter is controlled to absorb active power infeed from the stator into the DC-link chopper of the DFIG-converter. PSCAD EMTDC simulation results show that the presented chopper- and grid side converter control strategy reduces the grid side active power output during LVRT while maintaining electrical torque and mechanical load up to a certain point. The results depict that Type 3 WTG using the GSC-chopper-control algorithm can ride through faults at weak grid connection points reducing the active power grid infeed without further electrical torque reduction compared to strong grid connection fault scenarios. Additional results show a solution for the compensation of drive train damping active power fluctuation that are usually injected after fault clearance of Type 3 wind farms. This solution helps to reduce mechanical stress of the drive train of Type 3 wind turbines which are introduced by grid faults and improves Type 3 LVRT behaviour especially at weak grid connection points.