Optimization Strategies For Power And Load Control Of Large Wind Turbines

As a result of the rapid socio-economic growth,the world’s demand for energy resources emerge of blowout growth,conventional fossil energy extraction and consumption was substantially raised,the depletion of conventional fossil fuels and fossil energy brought about the environment pollution and other issues.In order to cope with the energy crisis,the various countries in the world has solved these problems from two aspects: on the one hand the exploitation of fossil fuels take appropriate measures to control,the optimization of industrial structure achieve energy-saving emission reduction;the other hand,energy technology and sustainable energy develop technical skill.Wind power is developed rapidly in the energy,it will not have an impact on the natural environment in the use of the process like coal,oil and other conventional fossil fuels,wind energy in the use of the process will not pollution to the natural environment,a wide range of wind energy can be recycled,etc.,the wind power technology in the field of sustainable energy research and development is important.With the increasing capacity of the wind turbine,the complexity of the unit becomes larger,so that the fragile wind turbine is more likely to resonate and so on,which seriously affected the safety and stability of the wind turbine.At the same time,the wind turbine in the turbulence,wind shear and tower shadow effect,the turbine has strong tilt and lateral movement,so that the wind turbine also bear variety of static loads and dynamic loads,such as aerodynamic loads,gravitational loads,structural loads,and gyro loads,which can lead to greater load and fatigue loads on wind turbines,it will damage to the wind turbine and affect its operating life.At the same time,the load will lead to wind turbine plane to capture the wind power fluctuations,it is difficult to ensure that the generator output power of high quality.The power control and loads optimization should be as the research objective in large wind turbine.The main contents and structure are as follows:(1)Large wind turbine is nonlinear and complex multivariable strong coupling system,it is difficult to establish the accurate system model and the aerodynamic load mathematical model.This paper is the basic idea of the wind power equivalent transformation,the aerodynamic theory of energy conversion is introduced.Secondly,the dynamic characteristics of large wind turbine are analyzed in detail.The influence of wind speed characteristics such as turbulence effect,wind shear and tower shadow effect on the vibration of large wind turbine was studied,and the main influence of dynamic load of wind turbine was obtained.And the wind speed model in the rotation plane of the wind turbine was established.Finally,the aerodynamic load of the wind turbine was analyzed by using the blade element momentum(BEM)theory.The influence of the aerodynamic load was deduced in wind turbine on the turbulence effect,the wind shear and the tower shadow effect,and the wind rotor torque and fatigue were simulated,the aerodynamic model of wind turbine based on BEM was established in FAST.The simulation results of wind turbine aerodynamic load considering turbulence effect,wind shear and tower shadow effect was given,and the results have verified the validity of the model.(2)A radial basis function neural network(RBFNN)optimization model predictive control was proposed for large wind turbines.In accordance with the complexity and uncertainty of wind turbine operation,a linear model based on the blade element momentum theory was established and the influencing factors of the proposed model were evaluated.The model predictive control taking into full account three degrees of freedom control multivariate was enforced by RBFNN prediction model,which meets the requirements of specified operation region.Additionally,the RBFNN prediction model with the memory of complicated rules and changed trend was trained by a great deal of historical data.The RBFNN in combination with model predictive control solves global optimization problems and improves the dynamic performance of system.Experimental results for large wind turbine verified the effectiveness of the proposed method.(3)Individual pitch controller based on fuzzy logic control for wind turbine load mitigation was proposed.It has motivated the development of blade individual pitch control methodologies of large wind turbine.This study analyzes on the aerodynamic linearization model,Coleman coordinate transformation and wind turbine blade unbalanced load for individual pitch control.The controllers are designed in order to optimize a trade-off among several control objectives such as blade root moment and generator torque.Three different fuzzy logic controls had been used in the controllers,the first one related to blade pitch angle and electromagnetic torque control variables to meet specified objectives for operation region,the second control model and the third model related to d-q axis blade moment in non-rotating frame of reference.Likewise,the optimization criteria of fuzzy logic controller consider for each controller objective to mitigate fatigue loads and regulate output power.Finally,the effectiveness of proposed method is verified by experimental results for wind turbine.The results proved that the fatigue loads in the turbine are reduced obviously.(4)Approach to model predictive control of large wind turbine using light detection and ranging measurements(LIDAR)was proposed,it achieved wind speed disturbance feedforward compensation control.First,the blade element momentum(BEM)theory have analyzed the wind turbine loads and LIDAR forecast wind speed of the rotor windward side,used of extended Kalman filter reconstruct unknown nonlinear wind turbine model for prediction horizon state values real-time processing,it solved the minimum objective function to get the current system time of the optimal control strategy,to minimize the reference trajectory and the output value.Finally,the experiments of results show that combination of LIDAR and model predictive control can improve power coefficient of large wind turbines and mitigate the fatigue load of wind turbine.In the end,the main innovations of the dissertation are summarized,and the fields for further investigation are expected.