| Nowadays,the competition in the wind power market is fierce.Only by mastering the core technology and making breakthroughs and innovations in the key technologies of wind power can we firmly control the market and remain invincible.Electro-hydraulic actuator system is a technical solution that combines the advantages of traditional hydraulic and electric variable pitch.In this work,the working mode and control method of the designed 2MW electro-hydraulic actuator system are studied systematically by combining mathematical modeling analysis and control research.The main research contents and conclusions are as follows:1.This work designs and improves the hydraulic circuit to meet the needs of variable pitch on the basis of the working principle and working mode of the existing electro-hydraulic actuator.ADAMS software was used to calculate the functional relationship between the pitch angle and the hydraulic cylinder expansion and contraction.Then the BLADED software is used to calculate the pitch load of the2 MW wind turbine as the gist for the selection of hydraulic components and motors.The hydraulic integrated block is designed according to the characteristics of the hydraulic circuit,the structure of the hydraulic components and the motor.Three-dimensional parts were assembled and the modal of the electro-hydraulic actuator was analyzed using the assembly model.The vibration range of the 3rd and4 th modes is the largest compared with other modes.At the same time,the harmonic response has the largest resonance amplitude between the 3rd and 4th mode frequencies.So the natural frequency of the actuator is between 50 Hz and 75 Hz.2.According to the structure and working principle of the 2MW electro-hydraulic actuator system,four working modes can be completed: open pitch,closed pitch,normal pitch operation and emergency closed pitch.The mathematical models and AMEsim simulation models of the main components of the system are established based on the relevant theories of wind turbines,hydraulic systems and permanent magnet servo AC motors.Using the advantages of AMEsim multi-system co-simulation,hydraulic systems,mechanical systems,permanent magnet servo motors and control systems were built.The electro-hydraulic actuators were studied in the operation of opening,closing,normal pitch operation and emergency closing through simulation.The results show that the system can achieve the design indexesof normal oar opening,oar closing and emergency oar closing,but in the stage of oar changing operation,the wave peaks and troughs following sinusoidal signals will appear flat head phenomenon that will affect the system performance.The main reasons for this phenomenon are motor reversing,oil compensation valve switching,hydraulic lock switching.Moreover,the tracking speed and amplitude of the system will decrease significantly under PID+PID control with the increase of the input signal frequency.Considering the efficiency decline caused by gear pump wear,internal and external leakage of hydraulic cylinder,air melts into oil and complex load in the later period of electro-hydraulic actuator.The influence of pump efficiency decline,internal and external leakage of hydraulic cylinder,oil melted into air and load on system response was studied by using AMEsim batch processing function.The results show that all the above faults will affect the response characteristics of the system,especially the leakage of the hydraulic cylinder,the application of sine and step load.This will cause the following curve of the system to be deformed.The significantly increased oil intake air will intensify the flat head of following the curve trough,which will affect the system response performance.3.Aiming at the shortcomings of PID+PID control,it is proposed to improve the response characteristics of the system by algorithm.The control link in this work is mainly composed of a position loop,a speed loop and a current(torque)loop.The position loop and the speed loop are composed of traditional PID controllers.Due to their inherent defects,an automatic disturbance rejection controller is proposed to replace the position,forming an auto disturbance rejection + PID control scheme.The results show that this control method is superior to PID+PID control,the follow-up of the command signal,the resistance to load shock and correction ability,and compensation for changes in system components structural parameters(Pump efficiency decreases,resulting in reduced displacement)are significantly better than the latter.This work aims at the problems of traditional hydraulic variable pitch and electric variable pitch,so as to introduce electro-hydraulic actuators into the wind turbine variable pitch system.Firstly,the pitch load calculation and component selection were carried out.Secondly,the mathematical model of the main components was established.Finally,the system was simulated and analyzed with the help of AMEsim and MATLAB platform.The results show that the electro-hydraulic actuator system can complete the wind turbine pitching task accurately and quickly,autodisturbance rejection technology can effectively solve the defects of traditional PID control and improve the system response. |
