Overview of Modelling and Advanced Control Strategies for Wind Turbine Systems

Abstract

Abstract:The motivation for this paper comes from a real need to have an overview of the challenges of modelling and control for very demanding systems, such as wind turbine systems, which require reliability, availability, maintainability, and safety over power conversion efficiency. These issues have begun to stimulate research and development in the wide control community particularly for these installations that need a high degree of "sustainability". Note that this represents a key point for offshore wind turbines, since they are characterised by expensive and/or safety critical maintenance work. In this case, a clear conflict exists between ensuring a high degree of availability and reducing maintenance times, which affect the final energy cost. On the other hand, wind turbines have highly nonlinear dynamics, with a stochastic and uncontrollable driving force as input in the form of wind speed, thus representing an interesting challenge also from the modelling point of view. Suitable control methods can provide a sustainable optimisation of the energy conversion efficiency over wider than normally expected working conditions. Moreover, a proper mathematical description of the wind turbine system should be able to capture the complete behaviour of the process under monitoring, thus providing an important impact on the control design itself. In this way, the control scheme could guarantee prescribed performance, whilst also giving a degree of "tolerance" to possible deviation of characteristic properties or system parameters from standard conditions, if properly included in the wind turbine model itself. The most important developments in advanced controllers for wind turbines are also briefly referenced, and open problems in the areas of modelling of wind turbines are finally outlined.

A Flexible Maximum Power Point Tracking Control Strategy Considering Both Conversion Efficiency and Power Fluctuation for Large-inertia Wind Turbines

“…Wind shear is not taken into account, because the effective wind speed is calculated as an average value of the fixed-point wind speed over the whole rotor. The statistical approach of fluctuations is introduced in [1]. The main parameters in the simulations are listed as follows, P rated = 2 MW, R w = 40 m, V w_rated = 11 m/s, N gear = 83.531, J = 56.27 × 10 5 kg·m 2 , C pmax = 0.48, λ opt = 8.1 [3,31].…”

“…With more and more attention being paid to environmental problems, wind energy has become one of the most important renewable energy sources to develop and utilize [1,2]. Although wind turbine control techniques have been developed for several decades, there are still many tough control problems to be solved.…”

Comparative Analysis of Decoupling Control Methodologies and H∞ Multivariable Robust Control for Variable-Speed, Variable-Pitch Wind Turbines: Application to a Lab-Scale Wind Turbine

“…When the wind speed is below its nominal value (region II), the control objective is to maximize the power captured from the wind. Over the nominal wind speed (region IV), the control goal is to maintain the power output at the rated power [2]. Although two control inputs (pitch angle and generator torque) are usually available, typical power control schemes use blade pitch angle as the only control input to keep the torque constant at its nominal value [3,4].…”

Strategic Maintenance Scheduling of an Offshore Wind Farm in a Deregulated Power System

“…In addition, a sensitivity analysis is carried out that deduces that the electricity price is one of the major parameters affecting the outcomes. Moreover, [24,25] mention that there is also a need for improving the way the condition monitoring features are being currently exploited as the transportation costs and scheduling of the transport mediums include the majority of the costs [26]. Furthermore, the study in [27] performs a sensitivity analysis in order to find out the most important parameters affecting O&M. It concludes that repair duration and labor working shift length are two of the most significant variables influencing the cost; maintenance resource availability and components' failure rates are the other two impacting availability.…”