Abstract
A novel fuzzy rule is proposed to adopt a positive pitch strategy when the error between the measured and rated generator speed becomes large and continues to increase, and to adopt a negative pitch strategy when the error is small. The improved approach is introduced into the normal Fuzzy-Proportional-Integral (Fuzzy-PI) control strategy by dividing the fuzzy rules into four areas and analyzing the design method for each area. Furthermore, a low pass filter is used to reduce the ultimate loads of the pitch driver caused by the novel fuzzy rules. The modeling of the wind turbine load under turbulent wind conditions is conducted in GH Bladed, and MATLAB/Simulink is used to interact with the modeling to verify the novel Fuzzy-PI control. The results show that, compared with normal Fuzzy-PI control, the novel Fuzzy-PI control can greatly reduce the ultimate loads and fatigue loads of the pitch driver. The novel Fuzzy-PI control not only reduces the extremum of power deviation, but also decreases some ultimate loads and fatigue loads of the tower base and the blade root. It can reduce these loads by up to 21.53% under the normal turbulent wind condition and by up to 18.14% under the extreme turbulent wind condition.
Highlights
Wind power has been developing rapidly worldwide due to fossil fuel energy depletion and environmental pollution
Compared with PI control, variations of −33.86% in the maximum of absolute value (MOAV) of power deviation and +8.33% in the MOAV of pitch rate were recorded by the novel Fuzzy-PI control
An improved approach was introduced into the normal Fuzzy-PI control strategy by dividing the fuzzy rules into four areas and analyzing the design method for each area
Summary
Wind power has been developing rapidly worldwide due to fossil fuel energy depletion and environmental pollution. The horizontal axis wind turbine (HAWT), especially on large-scale HAWT, has taken much of the wind energy market because of its high efficiency of harvesting wind energy. When facing complex atmospheric conditions, the elimination or mitigation of excessive loads for modern large-scale turbines is very necessary because it lessens the manufacture cost of turbines by reducing design requirements and extends the life of wind turbine key components [2]. Challenges of the controller design in wind turbines are introduced by the large moment of inertia and nonlinearity of wind turbines [3], along with random natural wind speeds with wide variation ranges. PID has a simple structure and high reliability, its parameters are fixed and cannot meet the multiple time-varying and nonlinear characteristics of wind turbines. Fuzzy control technology is based on fuzzy reasoning and linguistic rules; the influence of the Energies 2020, 13, 6086; doi:10.3390/en13226086 www.mdpi.com/journal/energies
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