Optimal Fractional Order Proportional Integral Derivative Controller for Hydraulic Pitch Actuator of Wind Turbine Blade

Abstract

Due to the increase in power demand different electrical energy sources are considered in the world, wind energy is one of the renewable energy sources used to produce electrical energy based on the combination of a turbine and generator system. To improve the power production from wind energy larger turbine rotors are being built, which causes increased aerodynamics and other loads across the turbine blades, which results in a decrease in wind turbine efficiency and operating lifespan. The wind turbine blade pitch control system is a critical component for limiting mechanical overload on the overall system, as well as limiting the power of the turbine when the wind turbine is subjected to excessive wind speed. Therefore, this study develops an optimum controller for a hydraulic pitch angle actuator to control the wind turbine blade pitch angle and reduce loads on the blades when the system operates above rated wind speed. Bernoulli’s equation and mass conservation laws apply to model the hydraulic turbine blade pitch actuator. Fractional order PID (FOPID) controller is used to improve the performance of the pitching mechanism and a genetic algorithm (GA) is used to find the optimal parameters of the controller based on minimizing integral absolute error (IAE) objective function. The overall system analysis and optimization were performed by using MATLAB/SIMULINK 2020a. The performance of the FOPID compared with the PID controller and the performance has been evaluated based on different reference signal-tracking capabilities. From the simulation result for the unit step input, the GA FOPID controller gives a settling time of 0.1159sec, overshoot of 1.344%, and IAE of 0.010, the FOPID controller gives a settling time of 0.416 sec, overshoot of 13.427%, and IAE of 0.0351 and the GA-PID gives a settling time of 1.18 sec, overshoot of 29.74%, IAE of 0.1921. Similarly, the GA-FOPID maintains improved tracking performance by lowering the IAE value for both sinusoidal and staircase signals. When considering the effect of load torque at the blade root the GA-FOPID controller gives a settling time of 0.116 sec, and IAE of 0.01099, and the GA-PID controller gives a settling time of 1.188 sec, and an IAE of 0.1926. From the transient performance of the controller, the proposed GA-FOPID controller shows better performance than conventional PID. Lastly discuss the effect of turbine blade pitch angle change on tip speed ratio, rotor speed, mechanical power, and torque of wind turbine.