Open Loop Control Of Large Wind Turbine Blades Load Based On Deformable Trailing Edge Flaps

To date,the main trend of wind energy development is that the capacity of wind turbines is increasing and the size of blades is lengthening.The use of longer blades makes the load of wind turbines more complex,and more susceptible to damage,and thus a shorter service life of the turbine.In addition,with the implementation of the parity access policy,it is necessary to strictly control the cost throughout the life cycle of wind turbines.Therefore,higher requirements are put forward for the load control of wind turbines.Trailing edge flap is one of the most effective flow control methods to reduce the load of wind turbines,which has attracted considerable attention from domestic and foreign scholars in recent years.Current research shows that the co-design of the blade with trailing edge flaps can effectively reduce the load.The design of trailing edge flap control system is one of the important steps.Nevertheless,for actual wind turbines,whether the trailing edge flaps should be controlled by open loop or closed loop control has not yet been clear.In order to solve this problem,we carry out the secondary development on the original intelligent blade simulation platform,and independently writes the trailing edge flap open loop control simulation platform.The open loop control function is in the form of sine function and square wave function,and the trailing edge flaps on the three blades are independently controlled.Based on the simulation platform,the open loop control simulation of trailing edge flaps under different inflow conditions was carried out to explore the open loop control law of trailing edge flaps.Firstly,the influence of different amplitude and frequency on the open loop control effect was simulated under shear flow.The results display that the open loop control system can effectively decrease the flap-wise fatigue load,especially when the wind speed is higher than the rated wind speed,and can reduce up to 66%of the blade root flap-wise moment fluctuation.When the rotor rotation frequency is 1P,the flap-wise moment of the blade root can be sufficiently controlled,but swinging at other frequencies will introduce interference at the corresponding frequency and the power spectral density at the corresponding frequency is also increased.After trailing edge flap controlling,the fluctuation of rotor thrust rises,which exercises a negative impact on the tower,especially the pitch moment of the tower base.Turbulence is a vital factor affecting the fatigue load of wind turbine.It is more meaningful to study the ability of open loop trailing edge flap control to reduce the fatigue load of the blade under the turbulence condition.The results represent that when the wind speed is higher than the rated wind speed,the open loop control can effectively reduce the fatigue load of the blade,and the standard deviation of blade root flap-wise moment can be reduced by 20%after control.Finally,a simulation study was carried out under the condition of extreme coherent wind gust to explore the ability of trailing edge flap open loop control to control the extreme load.According to the operation characteristics of the wind turbine,the entire operation process is divided into four working areas.When the wind turbine works in different working areas,the optimal swing amplitude parameters are different.Therefore,the control of different regions according to the characteristics of the unit’s yaw and pitching change is helpful to give full play to the control ability of the trailing edge flap.In summary,trailing edge flaps can effectively reduce blade fatigue and ultimate load without affecting the output power.The results provide a reference for the design of trailing edge flaps open loop controller and have a certain significance for promoting the large-scale industrial application of trailing edge flaps.