Showing papers on "Turbine published in 2003"

Dynamic modeling of doubly fed induction generator wind turbines

Abstract: It is now recognized that many large wind farms will employ doubly fed induction generator (DFIG) variable speed wind turbines. A number of such wind farms are already in operation and more are planned or under construction. With the rising penetration of wind power into electricity networks, increasingly comprehensive studies are required to identify the interaction between the wind farm(s) and the power system. These require accurate models of doubly fed induction generator wind turbines and their associated control and protection circuits. A dynamic model has been derived, which can be used to simulate the DFIG wind turbine using a single-cage and double-cage representation of the generator rotor, as well as a representation of its control and protection circuits. The model is suitable for use in transient stability programs that can be used to investigate large power systems. The behavior of a wind farm and the network under various system disturbances was studied using this dynamic model. The influence of the DFIG control on the stability of the wind farm was also investigated by considering different control gains and by applying network voltage control through both stator side and rotor side converters.

Acoustic Analysis of Gas Turbine Combustors

Abstract: Combustion instability has become a major issue for gas turbine manufacturers. Stricter emission regulations, particularly on nitrogen oxides, have led to the development of new combustion methods, such as lean premixed prevaporized(LPP)combustion,to replacethetraditionaldiffusion e ame.However,LPPcombustionismuchmore liable to generate strong oscillations, which can damage equipment and limit operating conditions. As a tutorial, methods to investigate combustion instabilities are reviewed. Theemphasis is on gas turbine applications and LPP combustion. The e ow is modeled as a one-dimensional mean with linear perturbations. Calculations are typically done in the frequency domain. The techniques described lead to predictions for the frequencies of oscillations and the susceptibility to instabilities for which linear disturbances grow expotentially in time. Appropriate boundary conditions are discussed, as is the change in the linearized e ow across zones of heat addition and/or area change. Many of the key concepts are e rst introduced by considering one-dimensional perturbations. Later higher-order modes, particularly circumferential waves, are introduced, and modal coupling is discussed. The modeling of a simplie ed combustion system, from compressor outlet to turbine inlet, is described. The approaches are simple and fast enough to be used at the design stage.

Summary of the Delft University Wind Turbine Dedicated Airfoils

Abstract: This paper gives an overview of the design and wind tunnel test results of the wind turbine dedicated airfoils developed by Delft University of Technology (DUT). The DU-airfoils range in maximum relative thickness from 15% to 40% chord. The first designs were made with XFOIL. Since 1995 RFOIL was used, a modified version of XFOIL, featuring an improved prediction around the maximum lift coefficient and capabilities of predicting the effect of rotation on airfoil characteristics. The measured effect of Gurney flaps, trailing edge wedges, vortex generators and trip wires on the airfoil characteristics of various DU-airfoils is presented. Furthermore, a relation between the thickness of the airfoil leading edge and the angle-of-attack for leading edge separation is given.Copyright © 2003 by Delft University of Technology

Dynamic modeling of GE 1.5 and 3.6 MW wind turbine-generators for stability simulations

Abstract: GE power systems has an ongoing effort dedicated to development of models of GE wind turbine generators (WTG) suitable for use in system impact studies. This paper documents the present recommendations for dynamic modeling of the GE 1.5 and 3.6 MW WTG for use in system impact studies. The paper includes recommended model structure and data, as well the assumptions, capabilities and limitations of the resulting model.

Wind Turbine Control for Load Reduction

Abstract: This article reviews techniques for the control of wind turbines during power production. Pitch control is used primarily to limit power in high winds, but it also has an important effect on structural loads. Particularly as turbines become larger, there is increasing interest in designing controllers to mitigate loads as far as possible. Torque control in variable-speed turbines is used primarily to maximize energy capture below rated wind speed, and to limit the torque above rated, but it can also be used to reduce certain loads. The design of the control algorithms is clearly of prime importance. Additional sensors such as accelerometers and load sensors can also help the controller to achieve its objectives more effectively. By controlling the pitch of each blade independently, it is also possible to achieve important further reductions in loading. It is important to be able to quantify the benefits of any new controller. Although computer simulations are useful, field trials are also vital. The variability of the real wind means that particular care is needed in the design of the trials. Copyright © 2003 John Wiley & Sons, Ltd.

Comparison of fixed speed and doubly-fed induction wind turbines during power system disturbances

Abstract: The dynamic modelling of large (MW) capacity fixed and variable speed induction generator wind turbines is discussed. A reduced order dynamic machine model is derived suitable for modelling both fixed speed and doubly-fed asynchronous generator wind turbines. Control schemes for variable speed turbines, using doubly-fed induction generators (DFIG), are described and simulated. Speed control characteristics and converter protection of the DFIG are implemented in the model. The operation of the models during power system disturbances such as network voltage sags and three-phase faults, as well as the possibility of network voltage instability, are investigated. Simulation results are presented using typical turbine and network data for wind farm installations.

Representing wind turbine electrical generating systems in fundamental frequency simulations

Abstract: Increasing numbers of wind turbines are being erected. In the near future, they may start to influence the dynamics of electrical power systems by interacting with conventional generation equipment and with loads. The impact of wind turbines on the dynamics of electrical power systems therefore becomes an important subject, studied by means of power system dynamics simulations. Various types of power system dynamics simulations exist and the approach depends on the aspect of power system dynamic behavior being investigated. In this paper, the focus is on fundamental frequency simulations, also known as electromechanical transient simulations. In this type of simulation, the network is represented as an impedance matrix and only the fundamental frequency component of voltages and currents is taken into account in order to reduce the computation time. This simulation approach is mainly used for voltage and angle stability investigations. Models of wind turbine generating systems that match the fundamental frequency simulation approach are presented and their responses are compared to measurements.

Modern Control Design for Flexible Wind Turbines

Abstract: Control can improve energy capture and reduce dynamic loads in wind turbines. In the 1970s and 1980s, wind turbines used classical control designs to regulate power and speed. The methods used, however, were not always successful. Modern turbines are larger, mounted on taller towers, and more dynamically active than their predecessors. Control systems to regulate turbine power and maintain stable, closed-loop behavior in the presence of turbulent wind inflow will be critical for these designs. This report applies modern state-space control design methods to a two-bladed teetering hub upwind machine at the National Wind Technology Center (NWTC), which is managed by the U.S. Department of Energy's National Renewable Energy Laboratory (NREL) in Golden, Colorado. The design objective is to regulate turbine speed and enhance damping in several low-damped flexible modes of the turbine. Starting with simple control algorithms based on linear models, complexity is added incrementally until the desired performance is firmly established.

Large band simulation of the wind speed for real time wind turbine simulators

Abstract: In this paper we propose two modeling procedures for wind speed simulation. These procedures could be implemented on the structure of a wind turbine simulator during studies concerning stand-alone or hybrid wind systems. The evolution of a horizontal wind speed has been synthesized taking into account two components. The medium- and long-term component is described by a power spectrum associated to a specific site. The turbulence component is assumed to be dependent on the medium- and long-term wind speed evolution. It is considered as a nonstationary process. Two simulation methods for this component, using rational and nonrational filters are proposed. In both procedures, the turbulence model is defined by two parameters, which are either obtained experimentally, or adopted a priori, according to information from the considered site. Numerical results and implementation aspects are also discussed.

The History and State of the Art of Variable-Speed Wind Turbine Technology

Abstract: Early wind turbines used for performing mechanical work (pumping, grinding and cutting) optimized aerodynamics by being allowed to run at variable speed. Some of the earliest DC electric wind turbines were allowed to run at variable speed. With the advent of grid-connected AC turbines, rotational speeds were limited in order to control the wind turbine AC frequency output to equal the grid frequency. With the advent of semiconductor devices, attempts began as early as the 1970s to allow variable-speed operation of large-scale turbines. The introduction of a new generation of high-voltage, high-speed power electronic components allows a wide range of variable-speed operation for very-large-scale machines. Over the past 30 years a number of designs have been tested, a few of which have entered commercial operation. A number of these designs and their histories are described. A detailed description of a wide range of electrical methods for allowing variable-speed operation is provided. Copyright © 2003 John Wiley & Sons, Ltd.

Navier-Stokes and Comprehensive Analysis Performance Predictions of the NREL Phase VI Experiment

Abstract: A vortex lattice code, CAMRAD II, and a Reynolds-Averaged Navier-Stoke code, OVERFLOW-D2, were used to predict the aerodynamic performance of a two-bladed horizontal axis wind turbine. All computations were compared with experimental data that was collected at the NASA Ames Research Center 80- by 120-Foot Wind Tunnel. Computations were performed for both axial as well as yawed operating conditions. Various stall delay models and dynamics stall models were used by the CAMRAD II code. Comparisons between the experimental data and computed aerodynamic loads show that the OVERFLOW-D2 code can accurately predict the power and spanwise loading of a wind turbine rotor.

Wind power management system and method

Abstract: According to certain disclosed embodiments of the invention, there is provided a wind power management system to monitor performance of wind turbine generators situated in wind farms, each having a number of wind turbine generators A real-time wind power portfolio manager receives and stores in real-time data being produced by the wind turbine generator parks The manager has a reporting module for generating profile reports for the performance of the wind turbine generators The manager has a server to provide the reports on-line regarding the wind turbine generators The server stores the real-time data to enable the reports to be based on the history of the project for each one of the parks

Millimeter-Scale, MEMS Gas Turbine Engines

Abstract: The confluence of market demand for greatly improved compact power sources for portable electronics with the rapidly expanding capability of micromachining technology has made feasible the development of gas turbines in the millimeter-size range. With airfoil spans measured in 100’s of microns rather than meters, these “microengines” have about 1 millionth the air flow of large gas turbines and thus should produce about 1 millionth the power, 10-100 W. Based on semiconductor industry-derived processing of materials such as silicon and silicon carbide to submicron accuracy, such devices are known as micro-electro-mechanical systems (MEMS). Current millimeter-scale designs use centrifugal turbomachinery with pressure ratios in the range of 2:1 to 4:1 and turbine inlet temperatures of 1200-1600 K. The projected performance of these engines are on a par with gas turbines of the 1940’s. The thermodynamics of MEMS gas turbines are the same as those for large engines but the mechanics differ due to scaling considerations and manufacturing constraints. The principal challenge is to arrive at a design which meets the thermodynamic and component functional requirements while staying within the realm of realizable micromachining technology. This paper reviews the state-of-the-art of millimeter-size gas turbine engines, including system design and integration, manufacturing, materials, component design, accessories, applications, and economics. It discusses the underlying technical issues, reviews current design approaches, and discusses future development and applications.

Offshore wind turbine

Abstract: A wind energy conversion system optimized for offshore application. Each wind turbine includes a semi-submersible hull with ballast weight that is moveable to increase the system's stability. Each wind turbine has an array of rotors distributed on a tower to distribute weight and loads and to improve power production performance where windshear is high. As much of the equipment associated with each rotor as possible is located at the base of the tower to lower the metacentric height. The equipment that may be emplaced at the bottom of the tower could include a power electronic converter, a DC to AC converter, or the entire generator with a mechanical linkage transmitting power from each rotor to the base of the tower. Rather than transmitting electrical power back to shore, it is contemplated to create energy intensive hydrogen-based products at the base of the wind turbine. Alternatively, there could be a central factory ship that utilizes the power produced by a plurality of wind turbines to create a hydrogen-based fuel. The hydrogen-based fuel is transported to land and sold into existing markets as a value-added 'green' product.

Recuperated gas turbine engine system and method employing catalytic combustion

Abstract: A recuperated gas turbine engine system and associated method employing catalytic combustion, wherein the combustor inlet temperature can be controlled to remain above the minimum required catalyst operating temperature at a wide range of operating conditions from full-load to part-load and from hot-day to cold-day conditions. The fuel is passed through the compressor along with the air and a portion of the exhaust gases from the turbine. The recirculated exhaust gas flow rate is controlled to control combustor inlet temperature.

Aggregated modelling of wind parks in power system dynamics simulations

Abstract: Increasing numbers of wind turbines are connected to electrical power systems, in order to reduce the adverse environmental impact of conventional electrical power generation. A tendency can be observed to erect these turbines in wind parks, connected to the high voltage transmission grid. These parks effect the dynamic behaviour of power systems, because in wind turbines generator types that are different from the conventional synchronous generator are used. To investigate the impact of a wind park on the dynamics of the power system to which it is connected, an adequate model is required. In order to avoid the necessity of developing a detailed model of a wind park with tens or hundreds of wind turbines and their interconnections and to calculate the wind speed signal for each individual turbine, aggregated wind park models are needed. In the paper, aggregated models for wind parks equipped with either constant or variable speed wind turbines are presented. It is shown that results obtained with an aggregated model and with a detailed model show a high degree of correspondence, both for normal operation and for disturbances.

Wind turbine device

Abstract: A hybrid blade wind turbine device formed of at least a pair of straight outer airfoil blades, and a pair of inner helical wing blades, as supported for rotation within a safety protective cage structure, which wind turbine can be mounted in the vertical, horizontal, or other aligned operational positions. The inner helical half wing blades, being preferably somewhat shorter than the length of the outer airfoil blades, act to “regularize” the swirling wind regime flowing through the hybrid wind turbine, so as to maximize the efficiency of the outer airfoil blades. The helical half wing blades can be formed of individual segmented vane segments to provide improved operational capabilities for the overall hybrid wind turbine. To best harness annualized available wind conditions, the hybrid wind turbine can be customized, through modification of the number of vane segments, the selection of the specific shape of the outer airfoil blades, and the specific operational positioning of the outer airfoil blades. Alternatively, the helical half wing blades can be formed as generally smooth-walled blades.

Ceramic matrix composite gas turbine vane

Abstract: A hybrid vane ( 50 ) for a gas turbine engine having a ceramic matrix composite (CMC) airfoil member ( 52 ) bonded to a substantially solid core member ( 54 ). The airfoil member and core member are cooled by a cooling fluid ( 58 ) passing through cooling passages ( 56 ) formed in the core member. The airfoil member is cooled by conductive heat transfer through the bond (( 70 ) between the core member and the airfoil member and by convective heat transfer at the surface directly exposed to the cooling fluid. A layer of insulation ( 72 ) bonded to the external surface of the airfoil member provides both the desired outer aerodynamic contour and reduces the amount of cooling fluid required to maintain the structural integrity of the airfoil member. Each member of the hybrid vane is formulated to have a coefficient of thermal expansion and elastic modulus that will minimize thermal stress during fabrication and during turbine engine operation.

Advanced Gas Turbine Cycles

Abstract: A brief review of power generation thermodynamics. Reversibility and Availability. Basic gas turbine cycles. Cycle effeciency with turbine cooling. Full calculations of plant effeciency. Wet gas turbine plants. The combined cycle gas turbine (CCGT). Novel gas turbine cycles. The gas turbine as a cogeneration plant.

Method of operating a wind turbine

Abstract: A wind turbine has a generator (7) with a connected rotor (3) having a hub (4) and blades (5) rotatably connected to the hub for adjusting the pitch angle. In a method of operating such a wind turbine under climatic conditions, where there is a risk of icing on the blades and no or weak wind, the generator is used as a motor for driving the rotor and the pitch angle of the blades is adjusted to ensure that the resulting wind substantially hits the leading edge of the blades. Any ice formed may be removed by means of de-icing in a known manner.

Modeling of the UAE Wind Turbine for Refinement of FAST{_}AD

Abstract: The Unsteady Aerodynamics Experiment (UAE) research wind turbine was modeled both aerodynamically and structurally in the FAST{_}AD wind turbine design code, and its response to wind inflows was simulated for a sample of test cases. A study was conducted to determine why wind turbine load magnitude discrepancies-inconsistencies in aerodynamic force coefficients, rotor shaft torque, and out-of-plane bending moments at the blade root across a range of operating conditions-exist between load predictions made by FAST{_}AD and other modeling tools and measured loads taken from the actual UAE wind turbine during the NASA-Ames wind tunnel tests. The acquired experimental test data represent the finest, most accurate set of wind turbine aerodynamic and induced flow field data available today. A sample of the FAST{_}AD model input parameters most critical to the aerodynamics computations was also systematically perturbed to determine their effect on load and performance predictions. Attention was focused on the simpler upwind rotor configuration, zero yaw error test cases. Inconsistencies in input file parameters, such as aerodynamic performance characteristics, explain a noteworthy fraction of the load prediction discrepancies of the various modeling tools.

Analysis of biomass-residue-based cogeneration system in palm oil mills

Abstract: Palm oil mills in Malaysia operate on cogeneration system using biomass residue as fuel in the boiler. The boiler produces high pressure and temperature steam which expands in a backpressure steam turbine and produces enough electric power for the internal needs of the mill. The exhaust steam from the turbine goes to an accumulator which distributes the steam to various processes in the mill. The study were made on seven palm oil mills in the Perak state in Malaysia. The primary objectives of the study are to determine boiler and turbine efficiencies, energy utilization factor, oil extraction rate and heat/power ratio for various palm oil mills working under similar conditions and adopting same processes. The palm oil industry is one of those rare industries where very little attempt is made to save energy. The energy balance in a typical palm oil mill is far from optimum and there is considerable scope for improvement. Bench-marking is necessary for the components in the mill. Energy-use bench-marking can give an overview of energy performance of the mills. The calculations were done to get net gain in power when back pressure turbine is replaced by a condensing turbine. It was found that the boiler and turbine have low thermal efficiencies compared to conventional ones used in power plants due to non-homogeneity and non-uniform quality of the fuel. The extraction rate was around 0.188. The use of condensing turbine increase the power output by 60% and the utilization factor was found to be 65% for the cogeneration system.

Continuous reactive power support for wind turbine generators

Abstract: Real and reactive power control for wind turbine generator systems. The technique described herein provides the potential to utilize the total capacity of a wind turbine generator system (e.g., a wind farm) to provide dynamic VAR (reactive power support). The VAR support provided by individual wind turbine generators in a system can be dynamically varied to suit application parameters.

Differential geared turbine engine with torque modulation capability

Abstract: A method and apparatus for controllable distribution of power from a turbine of a gas turbine engine between two rotatable loads of the gas turbine engine, comprises transferring a shaft power of the turbine to the respective rotatable loads using differential gearing operatively coupled with the turbine and the rotatable loads, respectively; and controlling the power transfer using machines operatively coupled with the respective rotatable loads, operable as a generator or a motor for selectively taking power from one of the rotatable loads to drive the other of the rotatable loads, or the reverse.