The Research On Re-cut-in Control Strategy Of Wind Turbines

The wind resource is abundant during typhoons.For the place where the wind resource is scarce in the whole year,the wind turbine manufacturers will try to make full use of the wind to generate electricity.During this period,the wind turbine will carry extraordinary both static and dynamic load.In order to avoid the wind load exceeding the designed wind load,a recut-in wind speed(generally 23m/s)has been set.When monitoring wind speed is greater than the cut-out wind speed(constant value 25m/s),the wind turbines brake and stop until the wind speed falls below the recut-in wind speed to start the turbines connected to the grid.Because the typhoon generally last for about from 2 to 4 hours,when the wind speed fluctuates near the cut-out speed,the recut-in control of 23m/s may fail in short time,and the turbine will frequently start and stop,which may obviously result in the failure probability of the wind turbine and speed up the aging of the unit components.In order to solve this problem,the wind speed of four typical New Zealand stations for 5 years are researched to study the recut-in control of wind turbines under typhoon conditions.Based on the frequent start and stop of fans during typhoons,A method of wind speed combined with time dead zone is put forward,and the selection of the optimal dead zone scenario is based on the premise that the maximum possible number of reductions in downtime,which is within the acceptable range of shutdown losses.The results of numerical simulation show that the combined dead zone scheme of different wind farms is not unique,and the number of downtime and the cost of cutting out for one time are better than the current control system using the single wind speed dead zone.In addition,the recut-in control of fans based on the prediction of moving average wind speed is studied.It divides the wind speed into three stages,rising,holding and falling,and predicts the wind speed in the next 2 hours.On the basis of the analysis of the distribution of wind speed under the typhoon,the prediction interval of the short-term wind speed forecast is constructed,and further implied to recut-in control.The simulation analysis shows that the proposed method can not only effectively reduce the frequency of the wind turbine cutting out during the typhoon,but also reduce the loss of power generation caused by the cut-out.Only if the control strategy is changed without equipment transformation,the proposed method is feasible.