Pitch Control of Three Bladed Large Wind Energy Converters—A Review

Abstract

Modern multi-megawatt wind turbines are currently designed as pitch-regulated machines, i.e., machines that use the rotation of the blades (pitching) in order to adjust the aerodynamic torque, such that the power is maintained constantly throughout a wide range of wind speeds when they exceed the design value (rated wind speed). Thus, pitch control is essential for optimal performance. However, the pitching activity is not for free. It introduces vibrations to the tower and blades and generates fatigue loads. Hence, pitch control requires a compromise between wind turbine performance and safety. In the past two decades, many approaches have been proposed to achieve different objectives and to overcome the problems of a wind energy converter using pitch control. The present work summarizes control strategies for problem of wind turbines, which are solved by using different approaches of pitch control. The emphasis is placed on the bibliographic information, but the merits and demerits of the approaches are also included in the presentation of the topics. Finally, very large wind turbines have to simultaneously satisfy several control objectives. Thus, approaches like collective and individual pitch control, tower and blade damping control, and pitch actuator control must coexist in an integrated control system.

A Review of Recent Aerodynamic Power Extraction Challenges in Coordinated Pitch, Yaw, and Torque Control of Large-Scale Wind Turbine Systems

“…The authors also found that by combining fuzzy systems, neural networks, and search algorithms, they could build diffuse neural networks with evolutionary capabilities to implement and represent human thoughts in pitch-controlled systems effectively. Following this, a complete review of the collective and individual pitch control, damping control, and pitch actuator control of large-scale wind energy converters was investigated in [83]. However, these reviews have not focused broadly on investigations into the coordinated pitch/yaw and generator torque control of super-large WTSs.…”

Active Edgewise Blade Damping Control of Large Wind Turbines by Using the Pitch Controller and an Interval Observer

“…The control signal, which is applied to all pitch actuators, is the pitch angle (pitch demand), and the feed-backed signal is the generator rotational speed. The rated generator rotational speed serves as the set-point (see [35] for a review). The main challenge is that very few inputs (only the three blade pitch actuators) are available for all control functions, so different control objectives are normally contradictory, and a compromise is required.…”

Wind farm control for wake-loss compensation, thrust balancing and load-limiting of turbines

“…In variable-speed, variable-pitch machines, the rotational speed, and the grid frequency are decoupled due to an indirect connection between generator and grid, which is carried out, nowadays, by the so-called back-to-back converters [48]. This concept is about 25 years old and allows wind turbines to down-regulate by reducing their speed while the grid frequency is maintained.…”