Robust fault-tolerant control in offshore wind turbines for actuator and sensor faults with advanced sliding mode controllers

Abstract

Clean energies as a source of power generation have grown in recent years as a solution for climate change. One of the most notable power sources is the use of wind turbines, especially those installed offshore, since their driving force is abundant, inexhaustible, and affordable, and they do not generate any emissions when operating. However, faults on different parts of the turbines are common and of particular importance in the hydraulic pitch system since they occur due to air in the system or stuck sensors, causing downtime and reducing the reliability of the system. These interruptions can result not only in high maintenance and repair costs but also in reduced renewable energy production, affecting the reliability and economic viability of wind energy as an alternative to fossil fuels. To address these challenges, it is crucial to develop robust and fault-tolerant control systems that maintain optimal operation of offshore wind turbines even under adverse conditions, thus ensuring their effective contribution to the transition towards a more sustainable and clean energy matrix. This thesis work addresses the challenge of ensuring robust and fault-tolerant control in offshore wind turbines, specifically in the context simultaneous and multiple failures in the blade control system. Two robust con- trollers based on sliding modes were developed: one using a PID+ST technique and the other employing a PID+ASM. These controllers were extensively compared with a baseline PI con- troller to evaluate their performance under faulty conditions. The research focused on a 5MW wind turbine, employing a simulation approach using tools such as FAST, MATLAB, and Simulink. Detailed analyses were conducted to assess the ability of the proposed controllers to maintain system performance and stability in the presence of blade control system fail- ures. The results demonstrated that both robust controllers showed significant improvements in terms of constant power generation and maintaining constant generator speed. However, it was observed that the controller based on adaptive sliding modes outperformed Super Twist-ing in terms of overall performance. This finding suggests that the adaptive approach offers better responsiveness and adaptability to variable and complex conditions in marine environ- ments. This study contributes to the advancement in the design and development of robust and fault-tolerant control systems for offshore wind turbines, with significant implications for improving the reliability and operational efficiency of such systems in critical and challenging environments.