Houria Siguerdidjane

Nonlinear Control of a Variable-Speed Wind Turbine Using a Two-Mass Model

The paper presents a nonlinear approach, using a two-mass model and a wind speed estimator, for variable-speed wind turbine (WT) control. The use of a two-mass model is motivated by the need to deal with flexible modes induced by the low-speed shaft stiffness. The main objective of the proposed controllers is the wind power capture optimization while limiting transient loads on the drive-train components. This paper starts by an adaptation of some existing control strategies. However, their performance are weak, as the dynamics aspects of the wind and aeroturbine are not taken into consideration. In order to bring some improvements, nonlinear static and dynamic state feedback controllers, with a wind speed estimator, are then proposed. Concerning the wind speed estimator, the idea behind this is to exploit the WT dynamics by itself as a measurement device. All these methods have been first tested and validated using an aeroelastic WT simulator. A comparative study between the proposed controllers is performed. The results show better performance for the nonlinear dynamic controller with estimator in comparison with the adapted existing methods.

Nonlinear Control of Variable-Speed Wind Turbines for Generator Torque Limiting and Power Optimization

To maximize wind power extraction, a variable-speed wind turbine (VSWT) should operate as close as possible to its optimal power coefficient. The generator torque is used as a control input to improve wind energy capture by forcing the wind turbine (WT) to stay close to the maximum energy point. In general, current control techniques do not take into account the dynamical and stochastic aspect of both turbine and wind, leading to significant power losses. In addition, they are not robust with respect to disturbances. In order to address these weaknesses, a nonlinear approach, without wind speed measurement for VSWT control, is proposed. Nonlinear static and dynamic state feedback controllers with wind speed estimator are then derived. The controllers were tested with a WT simple mathematical model and are validated with an aeroelastic wind turbine simulator in the presence of disturbances and measurement noise. The results have shown better performance in comparison with existing controllers.

Nonlinear Control of Variable Speed Wind Turbines without wind speed measurement

A nonlinear approach, for variable speed wind turbines control, is presented by considering that there is no wind speed measurement. The control objective below rated wind speed is to maximize the extracted energy from the wind while reducing mechanical loads. The existing control techniques do not take into account the dynamical aspect of the wind and the turbine, which leads to significant power losses, besides, they are not robust. In order to bring some improvement and to evaluate the applicability efficiency of the nonlinear controllers, so then, nonlinear static and dynamic state feedback controllers with wind speed estimator are derived. The controllers are tested upon a mathematical model and are validated with a wind turbine simulator, in presence of disturbances and measurement noise. The results indeed show significant improvements in comparison with the existing controllers.

Nonlinear control of variable speed wind turbines for power regulation

A nonlinear controller has been designed for variable speed wind turbines electric power regulation. The efficiency and reliability of wind power is shown to be depending on the applied control strategy of the wind turbine. Up to now, classical regulation is implemented only. However, under sudden wind profile variations, the wind turbine performance decrease which may cause troubles in the electrical network. For the limitation of mechanical loads and rotational speed variations, and to avoid the wind turbine stall above rated wind speeds while controlling the output power, a cascade structure asymptotic output tracking based approach has been applied. Simulations and validation have been performed using the wind turbine modelling and using wind turbine simulator as well. The wind turbine is torque generator controlled. The required performance is met for both

Some control strategies for a high-angle-of-attack missile autopilot

Abstract Recent interest in high maneuverability and stealth in missiles has triggered new investigations in estimating the potential and applicability of recent theoretical control methods as well as how they can meet industrial demands. Since the work presented here is closely related to an industrial application it is desirable to deal primarily with classical regulators. In this paper, two nonlinear methods are considered: `Approximate feedback linearization’ and the `asymptotic output tracking’ approach. Simulation results are given.

Three-Axes Missile Autopilot Design: From Linear to Nonlinear Control Strategies

A three-axes skid-to-turn missile autopilot design is presented. The modeling is that of a missile developed by AerospatialeMatraMissiles.Variouscontrollawshavebeencomparedinordertoestimatetheirpotentialandtheir applicability: classical linear time-invariant control and static and dynamic approximate input-output linearizing feedbacks. The robustness is studied, and the best results, in terms of stability, performance, and robustness, are shown to be obtained by using a special type of nonlinear dynamic control. The simulation results are explained using a table of comparison.

Experimental comparison of linear and nonlinear controllers for a magnetic suspension

We present an experimental comparison of a linear controller and two nonlinear controllers for a simple magnetic suspension. The linear controller is the classical PID, and the nonlinear controllers are based on a strategy called interconnection and damping assignment.

Frequency Stabilization for Multi-area Thermal–Hydro Power System Using Genetic Algorithm-optimized Fuzzy Logic Controller in Deregulated Environment

Abstract—This article develops a model of load frequency control for an interconnected two-area thermal–hydro power system under a deregulated environment. In this article, a fuzzy logic controller is optimized by a genetic algorithm in two steps. The first step of fuzzy logic controller optimization is for variable range optimization, and the second step is for the optimization of scaling and gain parameters. Further, the genetic algorithm-optimized fuzzy logic controller is compared against a conventional proportional-integral-derivative controller and a simple fuzzy logic controller. The proposed genetic algorithm-optimized fuzzy logic controller shows better dynamic response following a step-load change with combination of poolco and bilateral contracts in a deregulated environment. In this article, the effect of the governor dead band is also considered. In addition, performance of genetic algorithm-optimized fuzzy logic controller also has been examined for various step-load changes in different distribution unit demands and compared with the proportional-integral-derivative controller and simple fuzzy logic controller.

Nonlinear dynamic autopilot design for the non-minimum phase missile

We propose some new ideas to stabilize the center of mass of high angle of attack missile. The dynamics which describe a missile are known to be non-minimum phase. We first design a controller arising from the local linear controllers integration with respect to some of the state variables. Next, from the concept of nonlinear asymptotic tracking problem, we propose to circumvent the non-minimum phase phenomenon and to achieve the stabilization by appropriately choosing some of the parameters which govern the exponential decaying of the error function between the output of the system under consideration and the reference desired function. These parameters satisfy the Hurwitz polynomial. In both cases, it is shown that the required missile performances are met.

Robust nonlinear control strategy for HVDC light transmission systems technology

In this study, two robust nonlinear control strategies are investigated to control the HVDC Lighttrade transmission systems. The controllerpsilas design are based on the sliding mode control (SMC) and Lyapunovpsilas control methodologies to deal with the nonlinearities introduced by requirements to power flow and line voltage. First, the steady state mathematical model of the HVDC Light system is developed and the decoupled relationship between the controlling variables is investigated. Then, the SMC and Lyapunov control techniques are resorted to govern the DC link voltage and to control the active and reactive powers. The main feature of this hypothesis is the robustness with respect to parameterspsila variations. Saturation, sigmoid and hyperbolic functions are used to avoid the issue of ldquochatteringrdquo caused by imperfect switching in the SMC. Based on Lyapunov method, the controller guaranteeing convergence of the state trajectory is developed. The robust nonlinear controllers are demonstrated through simulation studies on HVDC Light transmission systems using MATLABcopy-Simulink software. Dealing with systems of high power ratings up to 300 MW, the simulation results show that the controllers contribute significantly toward improving the dynamic behaviour, enhancing the system stability and damping the oscillations over a wide range of operating conditions and parameters uncertainties.