Extreme loads calculate and security analysis of wind turbine variable pitch actuator

Pitch actuator endures complex load during operation process of wind turbine, and its load-bearing capacity influences the safe operation of whole wind turbine. In this paper, according to the operation control requirements of wind turbine, all kinds of complex operation conditions of pith actuator are taken into account, and GL-bladed software is used to calculate the load of pitch actuator. And then based on IEC61400-1: 2005, this paper uses extrapolation method of extreme load to acquire the extreme load of pith actuator´s driving torque which may occur once in 50 years. In the third part of this paper, the maximum loads that wind turbine operates under extreme turbine wind, extreme coherent gust with direction change and extreme wind shear, are extracted as the extreme load sample of pith actuator´s driving torque. And then using principle of statistics, this paper puts forward a new method which is based on confidence interval theory to estimate the extreme load of pith actuator. Considering the safety and economic benefits of wind turbine, this paper finally recommends that, the extreme load calculated by extreme load extrapolation method should be as a safety threshold which is used to judge whether pitch drive system is failure or not in design of pith actuator, while extreme loads value calculated by confidence interval method should be used as a rated design load reference value .This method are verified in simulation experiment of 3.0 MW direct drive wind turbine design.