Simultaneous design of pitch control and active tower damping of a wind turbine by using multi-objective optimization

Collective pitch control (CPC) and active tower damping control (ATDC) are currently two standard control loops of practically all commercial large-sized, variable-speed, horizontal axis wind turbines. Both control loops are highly coupled and therefore they perform in a contradictory manner: while an optimal CPC increases loads in the first fore-aft tower frequency, the ATDC damps these loads by modifying the pitch angle, i.e. detuning the CPC. Thus, the main problem is to find controller parameters that produce the best possible compromise between both controllers. In the current work, the controllers for CPC and ATDC are designed by using a cooperative game-theoretic approach, whose solution is found by using multi-objective parametric optimization. Simulation results show that the proposed method yields satisfactory performance for both control loops

Retraction phase analysis of a pumping kite wind generator

Airborne wind energy systems have developed very fast in the past five years. One of the most promising systems is the so called pumping kite wind generator, which is based on a cycle of two phases: the traction or generation phase and the retraction or consumption phase. An optimal balance between both phases is crucial in order to obtain an economically viable system. This work is devoted to the investigation of the retraction phase, i.e. the reel-in phase of a pumping kite wind generator, from the theoretical point of view. The most common approaches for the implementation of the retraction phase in the literature are studied from the point of view of the energy as well as time consumption. The first step of this work is the modeling of the dynamic behavior of the system during the tether reel-in process including the aerodynamic coefficients of a ram-air kite and by performing computational simulations. Perfect control is supposed. Hence, assumed that the control system shows its best performance, results of performed simulation experiments confirm that the behavior of the retraction phase is ruled by the system dynamics. The net energy gain of the complete cycle particularly depends on the efficiency of the retraction phase

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

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

Multiobjective Optimal Control of Wind Turbines: A Survey on Methods and Recommendations for the Implementation

Advanced control system design for large wind turbines is becoming increasingly complex, and high-level optimization techniques are receiving particular attention as an instrument to fulfil this significant degree of design requirements. Multiobjective optimal (MOO) control, in particular, is today a popular methodology for achieving a control system that conciliates multiple design objectives that may typically be incompatible. Multiobjective optimization was a matter of theoretical study for a long time, particularly in the areas of game theory and operations research. Nevertheless, the discipline experienced remarkable progress and multiple advances over the last two decades. Thus, many high-complexity optimization algorithms are currently accessible to address current control problems in systems engineering. On the other hand, utilizing such methods is not straightforward and requires a long period of trying and searching for, among other aspects, start parameters, adequate objective functions, and the best optimization algorithm for the problem. Hence, the primary intention of this work is to investigate old and new MOO methods from the application perspective for the purpose of control system design, offering practical experience, some open topics, and design hints. A very challenging problem in the system engineering application of power systems is to dominate the dynamic behavior of very large wind turbines. For this reason, it is used as a numeric case study to complete the presentation of the paper