Design of an adaptive controller to capture maximum power from a variable speed wind turbine system without any prior knowledge of system parameters

Even though some wind turbine manufacturers are no longer active, and are not willing to disclose their intellectual property, their turbines are still in operation. Since the exact values of wind turbine parameters like the aerodynamic model, drive-train model and generator parameters are not always accessible, the design of a controller which does not require prior knowledge of the system parameters can be very useful and effective. As a result, this paper proposes a disturbance observer-based controller to harvest the maximum power from a wind turbine system with fully unknown parameters. To reduce control efforts, a disturbance observer is designed to estimate unknown nonlinear terms caused by unknown model parameters in the presence of unknown control coefficient that uses only the tracking error to estimate nonlinear disturbance. Compared with previously published works, in this paper, both aerodynamic model and drive-train model parameters are assumed to be fully unknown. Closed-loop stability of the proposed controller is analyzed by the Lyapunov stability theorem. To demonstrate the performance of the proposed controller, it is compared with some existing controllers. Comparative simulation results show its effectiveness. Furthermore, although the proposed controller does not require system parameters and includes fewer tuning parameters, it shows the same tracking performance as the other three controllers. The numerical comparative results are listed in a table, which shows that Mean Square Error (MSE) of the proposed controller is 75% less than minimum MSE of the other three controllers of previous works, while its control effort is 1.7% higher than the minimum control effort of the other three.

Compound Helicopter X3 in High-Speed Flight: Correlation of Simulation and Flight Test

This work presents the correlation of simulation results and flight-test data for a high-speed (V = 220 kt), high advance ratio (μ > 0.5) flight of the compound helicopter X3. The simulation tool chain consists of state-of-the-art coupling between the computational fluid dynamics (CFD) code FLOWer and the comprehensive analysis tool HOST. By applying a freeflight trim procedure, the experimental flight state is accurately represented in the simulation. The deviations of most trim controls is below 1°, and the maximum deviation is less than 1.4°. The analysis of the high-fidelity CFD results illustrates key features of the flow physics at this high advance ratio, such as wake interactions, reverse flow, and advancing side loading. The correlation of rotor dynamics data between simulation and flight test is favorable. Good accordance is demonstrated for flap bending moments, torsion moments, and pitch link loads. In contrast, the correlation is weaker for the chord bending moments for which it is shown that the interblade damper and drive train model mostly determine the structural loads.

Computational Design Scheme for Wind Turbine Drive-Train Based on Lagrange Multipliers

The design optimization of wind turbines and their subsystems will make them competitive as an ideal alternative for energy. This paper proposed a design procedure for one of these subsystems, which is the Wind Turbine Drive-Train (WTDT). The design of the WTDT is based on the load assumptions and considered as the most significant parameter for increasing the efficiency of energy generation. In industry, these loads are supplemented by expert assumptions and manipulated to design the transmission elements. In contrary, in this work, the multibody system approach is used to estimate the static as well as dynamic loads based on the Lagrange multipliers. Lagrange multipliers are numerical parameters associated with the holonomic and nonholonomic constraints assigned in the drive-train model. The proposed scheme includes computational manipulations of kinematic constraints, mapping the generalized forces into Cartesian respective, and enactment of velocity-based constrains. Based on the dynamic model and the obtained forces, the design process of a planetary stage of WTDT is implemented with trade-off’s optimization in terms of gearing parameters. A wind turbine of 1.4 megawatts is introduced as an evaluation study of the proposed procedure, in which the main advantage is the systematic nature of designing complex systems in motion.

TRANSIENT MODELING OF A SMALL HYDROKINETIC TURBINE

In recent years, great attention has been given to the study of hydrokinetic turbines for power generation. Such importance is due to the use of clean energy technology by using renewable sources. Therefore, this work aims to present a relevant methodology for the efficient design of horizontal-axis hydrokinetic turbines with variable rotational speed. This methodology includes the Blade Element Method (BEM) for determining the turbine power coefficient, since BEM is widely used in the hydrokinetic turbine design due to its good agreement with experimental data. In addition, the dynamic equation of the driveline is used, taking into account the BEM to provide the rotor hydrodynamic torque coupled with the drive train model, including the multiplier and the electric generator. In this case, the modeling of the whole system comprises the hydrodynamic information of the rotor, the mass-moment of inertia, frictional losses and electromagnetic torque imposed by the generator. The theoretical results were obtained for the transient rotational speed and compared with field data measured from small hydrokinetic turbine installed at the Arapiranga-Açu creek, which is located in the city of Acará, Pará, Brazil.

Analysis and Optimization of Flexible Supported Drive Train in a Wind Turbine

Based on conventional drive train model of wind turbines, a planetary gearbox with flexible supporting between gearbox case and nacelle base is considered, and the coupled dynamic model of the drive train system is derived. The gearbox inner vibration performances are evaluated under different flexible parameters by means of dynamic simulation. It is shown that natural frequencies of each shaft are drifting while damping and elastic coefficients changing. Analysis also reveals that the flexible supporting mitigates torsion vibrations of each shaft. To minimizing torsion vibrations, a new searching approach is used to find out optimal parameters of the flexible supporting. Simulation results show that dynamic torque loads of the drive train are reduced, which is useful to wind turbine structure design.

Experimental Verification of Stick–slip Motion between Two Rolling Contact Surfaces

In this paper, a simplified drive train model with stick-slip nonlinearity is introduced for the study of stick-slip motion between the driving tires and the flywheel. Laboratory based tests are designed to investigate stick-slip motion of the tires contacting with the flywheels which simulate vehicle inertia. A description of the powertrain test rig, the associated instrumentation, the test inputs and operation conditions are provided. The experimental results are similar to those obtained from the numerical analysis using the introduced drive train model. They verify the validity of the stick-slip model, and demonstrate that stick-slip occurred frequently between the driving tires and the flywheels. The normal tire force applied to the flywheel is one of the key parameters affecting stick-slip motion. And there exists an upper limit beyond which the tire and flywheel will stick together at all time. It is found that the frequency of stick-slip motion is independent of normal tire force and is close to the natural frequency of the tire-flywheel contacting power transmitting system.