Ralf Schelenz

Model predictive control of a wind turbine modelled in Simpack

Wind turbines (WT) are steadily growing in size to increase their power production, which also causes increasing loads acting on the turbines components. At the same time large structures, such as the blades and the tower get more flexible. To minimize this impact, the classical control loops for keeping the power production in an optimum state are more and more extended by load alleviation strategies. These additional control loops can be unified by a multiple-input multiple-output (MIMO) controller to achieve better balancing of tuning parameters. An example for MIMO control, which has been paid more attention to recently by wind industry, is Model Predictive Control (MPC). In a MPC framework a simplified model of the WT is used to predict its controlled outputs. Based on a user-defined cost function an online optimization calculates the optimal control sequence. Thereby MPC can intrinsically incorporate constraints e.g. of actuators. Turbine models used for calculation within the MPC are typically simplified. For testing and verification usually multi body simulations, such as FAST, BLADED or FLEX5 are used to model system dynamics, but they are still limited in the number of degrees of freedom (DOF). Detailed information about load distribution (e.g. inside the gearbox) cannot be provided by such models. In this paper a Model Predictive Controller is presented and tested in a co-simulation with SlMPACK, a multi body system (MBS) simulation framework used for detailed load analysis. The analysis are performed on the basis of the IME6.0 MBS WT model, described in this paper. It is based on the rotor of the NREL 5MW WT and consists of a detailed representation of the drive train. This takes into account a flexible main shaft and its main bearings with a planetary gearbox, where all components are modelled flexible, as well as a supporting flexible main frame. The wind loads are simulated using the NREL AERODYN v13 code which has been implemented as a routine to SlMPACK. This modeling approach allows to investigate the nonlinear behavior of wind loads and nonlinear drive train dynamics. Thereby the MPCs impact on specific loads and effects not covered by standard simulation tools can be assessed and investigated. Keywords. wind turbine simulation, model predictive control, multi body simulation, MIMO, load alleviation

Akustische Untersuchungen im Gesamtsystem Verbrennungsmotor-Getriebe

Die akustische Optimierung von Einzelkomponenten eines Maschinenverbundes, wie zum Beispiel Verbrennungsmotor mit Getriebe, fuhrt nicht immer zu einer Reduktion der Schallemission des Gesamtsystems. Im Verbund der akustisch optimierten Einzelkomponenten konnen unerwunschte und unvorhergesehene Wechselwirkungen auftreten und zu erhohter Schallemission fuhren. Aus diesem Grund ist es wichtig, bei der Entwicklung larmarmer Produkte die gesamte Schallentstehungskette von der Anregung bis zur Schallabstrahlung zu betrachten. In einem Gemeinschaftsprojekt ist am Institut fur Maschinenelemente der RWTH Aachen und am Lehrstuhl fur Verbrennungsmotoren der RWTH Aachen eine Simulationsmethodik entwickelt worden, die die gesamte „Maschinenakustische Entstehungskette“ eines Motor-Getriebeverbundes abbildet [1].

Hybrid NVH Simulation for Electrical Vehicles II - Structural Model

Introduction The FVA research project No. 682 provides a fast, modifiable simulation tool starting with a model for the electrical drive train and resulting in a binaural auralization in the car cabin. The tool enables developers to freely change the properties of the electric drive components and listen to the resulting acoustics within a short time span. For this purpose, a fully-coupled drive train simulation model has been developed for the calculation of surface velocities and forces. The goal is a valid high frequency (<5000Hz) Multi-Body-Simulation (MBS) model of the drive train which fulfills the requirements of the entire simulation method for a binaural auralization. Therefore, a possibility for implementation of electromagnetic forces is needed and the exporting of surface velocities and forces at specific points is necessary.

Application of CPS Within Wind Energy—Current Implementation and Future Potential

Wind energy is a growing market and features high development potential on many levels in the future. In order to make use of the manifold potential, available data of wind turbines needs to be analyzed and advanced measuring technologies and communication networks have to be implemented. Hence, application of Cyber Physical Systems (CPS) can be a powerful approach to further develop the wind energy sector. Currently applied forms of CPS in wind energy are CMS or SCADA systems. However, these systems are not sufficient enough as a more extensive data analysis and communication network is required. Therefore, a future CPS in wind energy is presented in this article, which is the proposed next step in wind energy development. This advanced CPS is capable to reduce O&M costs and considers all relevant parameters of the power grid in order to optimize the operation and increase the efficiency of wind turbines and farms.

Akustische Untersuchung im Gesamtsystem Verbrennungsmotor-Getriebe

Die akustische Optimierung der Einzelkomponenten von Maschinen und Aggregaten ist Gegenstand vieler abgeschlossener und laufender Forschungsvorhaben. Die getrennte akustische Optimierung an den Einzelaggregaten wirkt sich im Allgemeinen auch positiv auf das Gesamtgerauschverhalten einer Maschinenanlage aus, die aus mehreren Einzelkomponenten zusammengesetzt ist. Zunehmend werden die Konstrukteure bei steigenden Forderungen an die Gerauschminimierung jedoch mit dem Phanomen konfrontiert, dass die als Einzelkomponenten getrennt entwickelten, optimierten und erprobten Baugruppen im Zusammenspiel unerwunschte und unvorhergesehene Gerausche verursachen. Bei der Entwicklung neuer, larmarmer Produkte ist daher zu beachten, dass Anregung, Luftschall und Korperschall nicht unabhangige Grosen der Einzelaggregate, sondern abhangig von deren Zusammenwirken im Gesamtsystem sind.

Comparison of wind turbine loads inside a wake between engineering model and CFD calculation

Depending on location and inflow situations, a wind turbine experiences a variety of loads. Especially when considering that wind turbines are placed in a cluster. Inside wind farms, the wind turbines experience wake effects. This effect results in an increased turbulence intensity and therefore into higher loads onto the wind turbine components. Such increased load situation could lead to an early fatigue failure. For this reason, it is necessary to investigate the influence of wake effect on the wind turbine loading. Multiple wake models have been developed to represent and inspect the wake effects. This paper will utilize the method proposed by the IEC 61400 norm versus an inflow field generated by a Computational Fluid Model. The resulting 3D wind fields are used as an input into a multi-body simulation environment. This is done to determine the influence on the receiving wind turbine. The comparison will be inspected at the rotor hub coordinate system, as suggested by the Germanischen Lloyd, such that influencing parameter can be minimized. It was determined that in case of a partial wake inflow the results of the CFD indicate a higher load variation in bending and tilt direction.

Modelling of Wind Turbine Loads nearby a Wind Farm

Each wind turbine experiences a variety of loads during its lifetime, especially inside a wind farm due to the wake effect between the turbines. This paper describes a possibility to observe a load spectrum while considering wake effects in a wind farm by through the turbulence intensity. The turbulence intensity is distributed along the wind rose of Alpha Ventus. For each turbulence intensity, a Weibull characteristic is calculated. The resulting wind fields are used to determine the loads through a multibody simulation of an imaginary wind turbine located at FINO-1, representing a closely placed wind turbine at the outer edge of a wind farm. These loads are analyzed and summed up. As expected, the change of the turbulence intensity due to the wake effect has an impact on the internal loading of a wind turbine inside a wind farm. Based on the assumed loading conditions, the maximum loads increased by a factor of almost 2.5.

Coupling of electromagnetic and structural dynamics for a wind turbine generator

This contribution presents a model interface of a wind turbine generator to represent the reciprocal effects between the mechanical and the electromagnetic system. Therefore, a multi-body-simulation (MBS) model in Simpack is set up and coupled with a quasi-static electromagnetic (EM) model of the generator in Matlab/Simulink via co-simulation. Due to lack of data regarding the structural properties of the generator the modal properties of the MBS model are fitted with respect to results of an experimental modal analysis (EMA) on the reference generator. The used method and the results of this approach are presented in this paper. The MB S model and the interface are set up in such a way that the EM forces can be applied to the structure and the response of the structure can be fed back to the EM model. The results of this cosimulation clearly show an influence of the feedback of the mechanical response which is mainly damping in the torsional degree of freedom and effects due to eccentricity in radial direction. The accuracy of these results will be validated via test bench measurements and presented in future work. Furthermore it is suggested that the EM model should be adjusted in future works so that transient effects are represented.

New Drive Train Concept with Multiple High Speed Generator

In the research project RapidWind (financed by the German Federal Ministry for Economic Affairs and Energy under Grant 0325642) an alternative 6 MW drive train configuration with six high-speed (n = 5000 rpm) permanent magnet synchronous generators for wind turbine generators (WTG) is designed. The gearbox for this drive train concept is assembled with a six fold power split spur gear stage in the first stage, followed by six individual 1 MW geared driven generators. Switchable couplings are developed to connect and disconnect individual geared generators depending on the input power. With this drive train configuration it is possible to improve the efficiency during partial load operation, increasing the energy yield about 1.15% for an exemplary low-wind site. The focus of this paper is the investigation of the dynamic behavior of this new WTG concept. Due to the high gear ratio the inertia relationship between rotor and generator differs from conventional WT concepts, possibly leading to intensified vibration behavior. Moreover there are switching procedures added, that might also lead to vibration issues.

Feasibility of large-scale calorimetric efficiency measurement for wind turbine generator drivetrains

In the course of the global energy turnaround, the importance of wind energy is increasing continuously. For making wind energy more competitive with fossil energy, reducing the costs is an important measure. One way to reach this goal is to improve the efficiency. As the major potentials have already been exploited, improvements in the efficiency are made in small steps. One of the main preconditions for enabling these development activities is the sufficiently accurate measurement of the efficiency. This paper presents a method for measuring the efficiency of geared wind turbine generator drivetrains with errors below 0.5% by directly quantifying the power losses. The presented method is novel for wind turbines in the multi- MW-class.