Research On The Control System Of Stepping Motor Variable Pitch Control For Wind Turbine Generator

With the increase of the diameter of wind turbine,Stifness of wind turbine blade declined,slowing the wind turbine output response and the fluctuation range.Especially in high wind conditions,the speed and active power regulation performance of wind turbine is not good,it affects the stability of active power output of wind turbine generator units and power grid operation seriously.On this condiction,wind shear effect and tower shadow effect become obviously.Not only the uneven load distribution of the blades,but also the wind turbine blades are not balanced.Due to the wind turbine cabin and tower vibration,causing fatigue failure and affecting the life of the wind turbine and safety.In order to reduce the vibration of wind turbines and the fluctuation of active power output,the variable pitch control method is adopted in large wind turbine.The traditional power controller generally adopted PI control strategy,the research on the power fluctuation is mainly focused on the control strategy now.To solve this problem,in this paper,stepping motor is used as the control system of variable pitch control system,the control performance of the variable pitch control system is adopted to improve the stability'of active power output of wind turbine.Firstly,the structure of several kinds of variable pitch control system of wind turbine is discussed,the main characteristics of stepping motor are analyzed,and the principle scheme of the stepping motor control system is presented;Secondly,wind turbine basic working principle,wind turbine operation characteristics,pitch control method and its characteristics are described;and the establishment of a wind turbine,direct drive permanent magnet generator,variable flow device and stepping motor mathematical model.Thirdly,using PSCAD/EMTDC to simulate wind turbine modeling,respectively for DC motor and step stepper motor as the executive mechanism of system simulation,get the first-order jump velocity pitch angle and power variation curve.By comparison,it is concluded that the static torque of stepping motor is large and the load change is small,so the load torque fluctuation can be reduced.Finally,selecting Siemens S7224XPCPU module as programming controller,motor and drive hardware on lab,simulating step type electric variable pitch system control performance experiment.The experimental results show that,stepping electric variable pitch system work stable performance,the regulating quality to achieve the desired effect.