| Ensuring the stable and efficient conversion of wind energy by wind turbines depends not only on the reliability of the wind power generation equipment itself,but also on the wind turbine control system.The yaw drive keeps the rotating surface of the wind turbine perpendicular to the wind direction to ensure that the turbine blades capture the maximum swept area.In a wind energy conversion system,the role of the yaw control system is to quickly and smoothly align the wind direction when the direction of the wind speed vector changes,so that the turbine can obtain the maximum wind volume.Large grid-connected wind power systems use wind sensors and yaw motors to actively yaw.With the increasing capacity of wind turbines,the importance of the yaw system has gradually become prominent.This paper analyzes the yaw data of Unit 5 of a wind farm located in Hunan Province through the SCAD A system of XEMC Windpower Co.,Ltd..A two-level economic model predictive control(TL-EMPC)yaw strategy is proposed,and the level is divided according to the wind speed previewed by lidar:In the first level,the control strategy of the CART3 turbine was improved,and the yaw threshold based on a fixed discrete period was set,and the discrete period was 20s,making it more suitable for the MPC yaw strategy;In the second level,the control strategy uses EMPC to establish a cost function directly linked to the economy with a discrete period of 60s.The yaw control method of the EMPC used in this paper does not need to use a quadratic cost function for optimization like the traditional MPC,but uses a cost function that is directly linked to economic performance.Based on lidar wind measurement,a cost function based on yaw power loss and yaw bearing equivalent damage is proposed.Compared with most MPC yaw strategies,wind direction information is only used as the variable parameter of the objective function.In this paper,both wind speed and wind direction are used as the target.The variables of the function,and the weight coefficients are calculated separately through the Pareto curve in different wind speed intervals.By simulating the yaw process under wind field conditions,the look-up table of the yaw bearing DEL in the yaw execution process is pre-generated,and the damage equivalent load is included in the objective function,so that DEL and power loss can be quantitatively evaluated.A discrete adaptive yaw speed subset is proposed,and an improved bring-in solution method is used to solve the minimum economic cost function,so that different yaw speeds can be selected under different average wind speeds and yaw errors.Fatigue loads at critical locations potentially provide room for improvement and increase feasibility in practical engineering.In addition,in view of the deficiency that the current LiDAR wind measurement usually adopts the Taylor assumption and ignores the actual evolution process of the wind,a wind evolution model is established and applied to the LiDAR wind measurement process.Finally,in the Bladed simulation software,the XE112-2000 wind turbine of XEMC Windpower Co.,Ltd.was used as a model,and compared with the traditional yaw control to verify the effectiveness of the TL-EMPC yaw strategy. |
