1,721,007 research outputs found
Design of Transverse Flux Permanent Magnet Machines for Large Direct-Drive Wind Turbines
No full textIn order to maximize the energy harnessed, to minimize the cost, to improve the power quality and to ensure safety together with the growth of the size, various wind turbine concepts have been developed during last three decades. Different generator systems such as geared and direct-drive generator systems have been developed. Based on energy yield, reliability and maintenance problems, direct-drive generator systems have been regarded as a better concept than geared generator systems. Among different generator types, the permanent magnet synchronous generator (PMSG) is superior in overall efficiency. The PMSG has also been discussed as a concept with higher force density than the electrically excited (EE) generators. PMSG can thus be small and lightweight compared to induction generators and direct-drive electrically excited synchronous generators (EESG DD). Therefore, this thesis focuses on the research of the direct-drive permanent magnet synchronous generator system (PMSG DD) for large wind turbines. The main objective of the thesis is to find a design solution for large direct-drive wind generators with highest possible energy yield and lowest possible cost.Electrical Power EngineeringElectrical Engineering, Mathematics and Computer Scienc
Optimized Permanent Magnet Generator Topologies for Direct-Drive Wind Turbines
No full textThe thesis deals with the issue of cost reduction in direct-drive generators for wind turbines. Today, the combination gearbox-medium-speed (1000-2000 rpm) induction generator largely dominates the market of MW-scale wind turbines. This is due to the lower costs of the gearbox option compared to the costs of gearless systems. Nevertheless, there is an acute interest among researchers and wind turbine suppliers in the possibility of removing gears and slip rings from the drive train, leading to lower maintenance (no oil is required and slip rings can be avoided) and higher reliability due to the absence of wear between gears. The direction followed by the thesis is the investigation and comparison of various permanent magnet (PM) machine topologies. The aim is to identify the topology(ies) with the lowest cost/torque and highest torque/ mass. A new TFPM geometry, called TFPM machine with toothed rotor, is derived in the. The new machine topology has the following characteristics: the stator is single-sided, the rotor PM and flux concentrators are independent from the build-up of mechanical tolerances, the installation of rotor parts (PM and flux concentrators) can be automated and the flux circulation allows laminated steel to be used in the stator core. A prototype of the TFPM machine with toothed rotor is presented. The comparison between TFPM machines with toothed rotor and conventional PM synchronous machines is discussed. Comparison of the cost/torque and torque/mass of the two machine topologies for diameters ranging between 0.5 m and 3.0 m showed favorable expected performances of the TFPM machine with toothed rotor for diameters of 0.5 m and 1.0 m. However, diameters larger than 1.0 m favored the conventional PM synchronous machine with/without flux-concentration. Using the results of the optimization process, the costs of active material are computed for a 1.5 MW wind turbine. It is found that active material represents about 5% of the total turbine cost, while previous estimates indicated that the generator costs are rather between 30% and 40% of a complete direct-drive wind turbine. Therefore, further optimiza¬tion of direct-drive machines should also include the costs of manufacturing and the costs of the mechanical structure.Electrical Engineering, Mathematics and Computer Scienc
Structural Flexibility of Large Direct Drive Generators for Wind Turbines
No full textThe trend in wind energy is towards large offshore wind farms. This trend has led to the demand for high reliability and large single unit wind turbines. Different energy conversion topologies such as multiple stage geared generators, single stage geared generators and gearless (direct drive) generators have been coupled to the wind turbine in the last decades. Direct drive generators based on permanent magnet technology have a high efficiency, less components and lower speeds that can translate to high energy yield and less maintenance demand. However, the mass of such direct drive generators can be significantly higher than of other geared generators. This thesis focuses on the issue of mass reduction of large direct drive generators in wind turbines. The main objective of this thesis is to investigate methods of mass reduction in large direct drive generators in wind turbines especially mass reduction by introducing structural flexibility in the generator. This allowance in structural flexibility is enabled by the use of magnetic bearing technology.EPPElectrical Engineering, Mathematics and Computer Scienc
Cost optimising design alternatives for the primary distribution system on Floating Liquid Natural Gas vessels
No full textThe global demand for natural gas is growing as gas is a cleaner partner to renewable energy than oil and coal. To be able to exploit remote offshore gas fields Shell is developing a floating facility to produce, treat and liquefy natural gas, called a Floating Liquid Natural Gas (FLNG) vessel. To make the FLNG vessel a cost effective option for LNG production the costs of the vessel need to be reduced. This thesis evaluates which changes to the current electrical system on FLNG vessels are able to reduce the total costs of the vessel. For this evaluation a current design of an electrical system for FLNG vessels is used as a template, but reference is also made to all-electric electrical systems that have a larger total load. The possible changes are evaluated in three areas: First an estimate on the cost advantages of implementing each change to the electrical system is made. Besides the equipment and installation costs also the cost impact of the required space and weight of the equipment is taken into account. Secondly the technical operational performance of the system is evaluated using simulations of the electrical system. A final evaluation is made for the impact of the change to system performance factors such as safety, availability, maintenance and efficiency. The analysis shows that a cost reduction of approximately 30 M USD can be achieved by removing large HV transformers from the system, resulting in an electrical system with one voltage level less than the original design. The electrical performance simulations show that a number of additional changes are required to keep the short-circuit current levels of the system within the switchgear ratings. Alternative system designs are proposed for currently typical 130 MW systems and for future all-electric systems with a total load of over 300 MW.Electrical Engineering, Mathematics and Computer ScienceElectrical Sustainable EnergyDC systems, Energy conversion & Storag
Rough design of a 10 MW HTS wind generator
No full textSustainable Energy TechnologyElectrical Power EngineeringElectrical Engineering, Mathematics and Computer Scienc
Limits, modeling and design of high-speed permanent magnet machines
No full textThere is a growing number of applications that require fast-rotating machines; motivation for this thesis comes from a project in which downsized spindles for micro-machining have been researched (TU Delft Microfactory project). The thesis focuses on analysis and design of high-speed PM machines and uses a practical design of a high-speed spindle drive as a test case. Phenomena, both mechanical and electromagnetic, that take precedence in high-speed permanent magnet machines are identified and systematized. The thesis identifies inherent (physical) speed limits of permanent magnet machines and correlates those limits with the basic parameters of the machines. The analytical expression of the limiting quantities does not only impose solid constraints on the machine design, but also creates the way for design optimization leading to the maximum mechanical and/or electromagnetic utilization of the machine. The models and electric-drive concepts developed in the thesis are evaluated in a practical setup which includes a slotless PM motor with a short rotor supported by aerostatic bearings.Electrical Power EngineeringElectrical Engineering, Mathematics and Computer Scienc
Control of magnetic bearings in wind turbines
No full textDirect drive generators applied to large wind turbines present some problems, such as very heavy and expensive price. The use of magnetic bearings has a possibility to reduce the weight of the direct drive generator. The control system for such magnetic bearings is considered. In the beginning, the thesis discusses the problems of direct drive generators in large wind turbines, introduces a hybrid concept of active magnetic bearings, gives a demonstrator of magnetic bearings used in this project, and presents a basic control system of active magnetic bearings. For the purpose of support such magnetic bearings in wind turbines, this thesis gives a complete control system. This control system includes electrical circuits and decentralized control method. The implementation of the electrical circuits is distributed into two PCBs. The decentralized control method is designed with six PID controllers. Finally, in order to improve the stability of the system, the H-infinity control method is suggested to magnetic bearing system in wind turbine applications.Electrical Power EngineeringElectrical Engineering, Mathematics and Computer Scienc
Modeling and topology investigation of modular machines for wind generator systems
No full textWind energy has recently come to constitute more than 10% of the electric power consumed in the EU. As the wind industry is rapidly growing, wind turbines grow larger and new models are soon expected to reach ratings of 10 MW. The development of offshore wind farms is another major trend in the industry. Offshore farms are particularly suitable for installation of large turbines, able to utilize the stronger winds available. However, in case of an offshore failure, it could require weeks to access and repair the turbine. Even in onshore farms, the turbine size cannot allow frequent disconnections. In this context, increasing turbine availability emerges as a critical issue: Modularity is seen as a promising approach to respond to this need. Modular systems can be decomposed into a number of independent 'modules' or components. Such systems can have their faulted modules bypassed and continue operation after fault, increasing system availability. Less frequent and easier repair can also achieved. Different levels of modularity have been proposed: Systems with modular converters or systems with modularity both in the converter and machine, with possible levels of modularity in the machine itself. Focusing on the machine-side of modularity, this thesis aims to produce a comparative study of the main modular machine topologies proposed in literature. The first step to address this problem, is to propose some promising machine topologies, suitable for modular design. Subsequently, a 2-D analytical model is developed, able to account for different types of winding. The model calculates important quantities to evaluate electromechanical performance (Back-EMF, Power, cogging torque) and efficiency (iron loss, copper loss). Analytical modelling results are validated by means of FEM modelling. The validated analytical model is then used to carry a first level comparison of numerous modular winding machines. The designs which perform best in terms energy yield, efficiency and cost are promoted for a second level comparison, where further modularity is introduced. This time, the machine stator is segmented and different segmentation ideas are applied. The segmented designs are compared by means of FEM. After the optimal design is selected, the flux gaps introduced in the stator core are considered, and the influence of gap width on the machine performance is investigated.Electrical Engineering, Mathematics and Computer ScienceElectrical Power Processin
Hydraulic drivetrains for wind turbines: Radial piston digital machines
No full textSustainable Energy TechnologyElectrical Power EngineeringElectrical Engineering, Mathematics and Computer Scienc
Design of 2.25 MW, permanent magnet direct drive generator for wind energy applications with concentrated windings and reduction of eddy current losses in the rotor back iron
No full textElectrical Power EngineeringElectrical Engineering, Mathematics and Computer Scienc
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