Research On Fuzzy Self-tuning PID Control Of The Wind Turbine Variant Pitch System With Clearance

The wind turbine variant pitch control system is one key technology of wind turbine control system, it improved the efficiency and electricity quality of the wind power generation system. However, the clearance exist in hinge of the electro-hydraulic control mechanism of the wind turbine variant pitch system increased the Pitch Angle overshoot and aggravate flapping in the process of variant pitch. To solve above problems, the formation mechanism of clearance in hinge is analyzed and AMESim model of the electro-hydraulic control system with clearance nonlinearity is found, the influence of clearance to the wind turbine variant pitch control system with conventional PID is simulated and analyzed. For the clearance in hinge, the compensation control strategy is proposed: based on the conventional PID, combine with the Fuzzy control, the Fuzzy self-tuning PID control is found, then, according to the “continuous contact model” of clearance, the fuzzy inference rules is made and then through this fuzzy rules, the online self-tuning PID controller parameters is realized.The characteristics of the movement at clearance is analyzed and the work law of the wind turbine pitch at the clearance is obtained: when the pitch error work in the clearance period,(1) when the pitch error rate is large, in order to maintain stable pitch, appropriately reduce the proportional gain and increase the integral gain; to ensure the rod quickly across the clearance, but not so excessive overshoot, increase the differential gain.(2) when the pitch error rate is small, in order to ensure the pitch response speed, increase the proportional gain, in order to maintain the stability of the pitch and does not overshoot, take moderate integral gain and differential gain. According to this law, the fuzzy rule considering clearance is developed, and the wind turbine pitch PID controller parameters online self-tuning is realized.Using AMESim software and LabVIEW software co-simulation method, the wind turbine pitch electro-hydraulic control system with clearance is simulated and compared with conventional PID, the simulation results show that: with the increase of the clearance, the overshoot process is larger and the more the number of shock numbers; The Fuzzy self-tuning PID control algorithm makes the overshoot and the pitch shock number down, the influence of the clearance is reduced effectively and making the pitch more stable. With the Fuzzy self-tuning PID control algorithm, the pitch control system quality is improved.Finally, Based on the wind turbine pitch electro-hydraulic control system experiments platform with clearances, the encoder feedback measurement method is studied, according to the actual wind turbine pitch system parameters, Fuzzy self-tuning PID and conventional PID control system was studied under no-load conditions, when the clearance is 0mm、0.2mm、0.4mm、0.6mm and 0.8mm,the results showed that: with the increase of the clearance, the larger the amount of system overshoot; when the clearance is less than 0.2mm, Fuzzy self-tuning PID control system’s overshoot is zero, the conventional PID control system’s overshoot is 15%; when the clearance is equal to 0.4mm, Fuzzy self-tuning PID control system’s overshoot is 10% and the conventional PID control system’s overshoot is 20%; when the clearance are 0.6mm and 0.8mm, the conventional PID appear dramatic slight concussion in the adjustment process the settling time becomes longer, and concussion sustained at the target location in the later adjustment period, On the contrary, Fuzzy self-tuning PID control system is smooth, no shocks. So we can see that, compared to the conventional PID controllers, Fuzzy self-tuning PID has a good compensation effect for the clearance.