By analyzing the blade loading conditions at different azimuth angles during the process of triggering yaw over-limit shutdown in wind turbines, it is pointed out that the unbalanced blade loading under large yaw angles is the root cause of the extreme load in the hub center. The effects of pitch angle and yaw angle direction on the unbalanced loading are studied. Based on the original control strategy, an IPC variable-speed shutdown strategy based on the blade azimuth angle is introduced to reduce the aerodynamic imbalance of the turbine under negative large yaw, greatly reducing the extreme loads in the hub and yaw bearing centers in accordance with IEC standards. Taking a 7.0 MW offshore wind turbine as example and conducting load calculations under yaw over-limit operating conditions, comparative analysis shows that the IPC variable-speed shutdown strategy based on blade azimuth angle can reduce the overturning bending moment introduced by unbalanced thrust, achieve the goal of reducing turbine loads, and provide a reliable basis for load reduction under specific wind conditions.
Key words
wind turbines /
blades load alleviation /
yaw control /
individual pitch control /
Bladed simulation
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