Comparison of doubly-fed induction generator and brushless doubly-fed reluctance generator for wind energy applications

Phd ThesisThe Doubly-fed Induction Generator (DFIG) is the dominant technology for variable-speed wind power generation due in part to its cost-effective partially-rated power converter. However, the maintenance requirements and potential failure of brushes and slip rings is a significant disadvantage of DFIG. This has led to increased interest in brushless doubly-fed generators. In this thesis a Brushless Doubly-Fed Reluctance Generator (BDFRG) is compared with DFIG from a control performance point of view. To compare the performance of the two generators a flexible 7.5kW test facility has been constructed. Initially, a classical cascade vector controller is applied to both generators. This controller is based on the stator voltage field orientation method with an inner rotor (secondary stator) current control loop and an outer active and reactive power control loop. The dynamic and steady state performance of two generators are examined experimentally. The results confirm that the BDFRG has a slower dynamic response when compared to the DFIG due to the larger and variable inductance. Finally a sensorless Direct Power Control (DPC) scheme is applied to both the DFIG and BDFRG. The performance of this scheme is demonstrated with both simulation and experimental results.Engineering and Physical Sciences Research Council (EPSRC) and Overseas Researcher Scholarship (ORS

Aerospace Medicine and Biology: A continuing bibliography with indexes (supplement 133)

This special bibliography lists 276 reports, articles, and other documents introduced into the NASA Scientific and Technical Information System in September 1974

Modelling, Monitoring, Control and Optimization for Complex Industrial Processes

This reprint includes 22 research papers and an editorial, collected from the Special Issue "Modelling, Monitoring, Control and Optimization for Complex Industrial Processes", highlighting recent research advances and emerging research directions in complex industrial processes. This reprint aims to promote the research field and benefit the readers from both academic communities and industrial sectors

Some drive train control problems in hybrid i.c engine/battery electric vehicles

This thesis describes the development of a microprocessor based control system for a parallel hybrid petrol/electric vehicle. All the fundamental systems needed to produce an operational vehicle have been developed and tested using a full sized experimental rig in the laboratory. The work begins with a review of the history of hybrid vehicles, placing emphasis on the ability of the petrol electric design to considerably reduce the consumption of oil based fuels, by transferring some of the load to the broad base of fuels used to generate electricity. Efficient operation of a hybrid depends on the correct scheduling of load between engine and motor, and correct choice of gear ratio. To make this possible torque control systems using indirect measurements provided by cheap sensors, have been developed. Design of the control systems is based on a theoretical analysis of both the engine and the motor. Prior to final controller design, using the pole placement method, the transfer functions arising from the theory are identified using a digital model reference technique. The resulting closed loop systems exhibit well tuned behaviour which agrees well with simulation. To complete the component control structure, a pneumatic actuation system was added to a 'manual gearbox' bringing it under complete computer control. All aspects of component control have been brought together so that an operator can drive the system through simulated cycles. Transitions between modes of operation during a cycle are presently based on speed, but the software is structured so that efficiency based strategies may be readily incorporated in future. Consistent control over cycles has been ensured by the development of a computer speed controller, which takes the place of an operator. This system demonstrates satisfactory transition between all operating modes

Thin Wall Structure by Welding

Manufacturing of thin wall structure by wire arc additive manufacturing (WAAM) is on the main application of additive manufacturing. 3D-printing technology has significant advantages over traditional milling and machining techniques or welded analogs. Thin wall structure constitutes an essential and growing proportion of engineering construction, within common areas as in structural aerospace and large scale-components. The dissertation utilized a layer-wise production technique known as gas arc tungsten arc welding (GTAW), performed by a programmed KUKA-30 robot. The thesis aspect of welded structures is the degree of how disposable the product is after manufactured, due to the different set of welding parameters. Therefore are an investigation of residual stresses and deformation implemented by different structure geometries. The research includes two practical and analytical experiment tests in addition to an FEA-simulation. The experiments involve; ultrasound measurement by a self-programmed measuring device developed by BiT, calculation due to measured deformation along the welding length and simulation performed in ANSYS. Findings of the methods implicate an estimated value of residual stresses and distortion in the thin wall structure and substrate. Through ten tests of the welding process can the technique of this technology state as slow with frequently sources of error, using the KUKA-30 robot welding system for a certain height. The level of residual stresses depends on the severity of the manufacturing process, which this research confirmed a generally low value along the length of the structural components and base plate due to the parameters developed in this study

Development and Testing of a New Transport Protocol Optimized for Multimedia Internet Transactions.

The TCP/IP protocol, which carries over 95% of data across the Internet, was first published in 1974 at a time when packet-switching was a new technology and computer communications were dominated by the virtual-circuit paradigm. Computer networking has changed dramatically in the past quarter-century, but the underpinnings of TCP have remained virtually unchanged. Many of TCP's most significant design assumptions are no longer valid in the modern Internet. As a result, TCP typically exhibits extremely poor performance including congestion, underutilization of bandwidth, and server overload. Despite these facts, and increasing evidence that TCP/IP is not suited to many of the application protocols it supports, only incremental improvements have been widely researched and no viable alternatives have come to prominence. This dissertation proposes a new transport protocol, the Multimedia Transaction Protocol (MTP), which has been created to meet the needs of modern applications operating in a modern network environment. This new protocol has been designed to handle transaction style client-server interactions across an unreliable, highly congested, packet-switched network. Experimental and simulation results show that MTP provides an order of magnitude improvement in throughput while contributing to network stability and greatly reducing latency. This work characterizes the modern transport environment, describes the design and implementation of MTP, and presents initial test results

Advances in Condition Monitoring, Optimization and Control for Complex Industrial Processes

The book documents 25 papers collected from the Special Issue “Advances in Condition Monitoring, Optimization and Control for Complex Industrial Processes”, highlighting recent research trends in complex industrial processes. The book aims to stimulate the research field and be of benefit to readers from both academic institutes and industrial sectors

Full-field vibrometry by high-speed digital holography for middle-ear mechanics

Hearing loss affects approximately 1 in 10 people in the world and this percentage is increasing every year. Some of the most common causes of hearing loss are disorders of the middle-ear. Early detection and diagnosis of hearing loss as well as research to understand the hearing processes depend on medical and research tools for quantification of hearing capabilities and the function of the middle-ear in the complex acousto-mechanical transformation of environmental sounds into vibrations of the middle-ear, particular of the human tympanic membrane (TM or eardrum). Current ear exams assess the state of a patient’s hearing capabilities mainly based on qualitative evaluation of the healthiness of the TM. Existing quantitative clinical methods for description of the motion of the TM are limited to either average acoustic estimates (admittance or reflectance) or single-point displacement measurements. Such methods could leave examiners and researchers blind to the complex spatio-temporal response of the nanometer scale displacements of the entire TM. Current state-of-the-art medical research tools provide full-field nanometer displacement measurements of the surface of the human TM excited by steady state (tonal) stimuli. However, to fully understand the mechanics of hearing, and the complex acousto-mechanical characteristics of TM in particular, new tools are needed for full-field high-speed characterization of the nanometer scale displacements of the human TM subjected to impulse (wideband) acoustic excitation. This Dissertation reports the development of a new high-speed holographic system (HHS) for full-field nanometer transient (i.e., \u3e 10 kHz) displacement measurement of the human middle-ear and the tympanic membrane, in particular. The HHS allows spatial (i.e., \u3e500k data points) and temporal (i.e., \u3e 40 kHz) resolutions that enable the study of the acoustical and mechanical characteristics of the middle-ear at a level of detail that have never been reached before. The realization of the HHS includes the development and implementation of novel phase sampling and acquisition approaches that allow the use of state-of-the-art high-resolution (i.e., \u3e5 MP) and high-speed (\u3e 80,000 fps) cameras through modular and expandable control architectures. The development of novel acquisition approaches allows the use of conventional speed (i.e., \u3c20 fps) cameras to realize high-temporal resolutions (i.e., \u3c15 us) at equivalent sampling rates of \u3e 50,000 fps with minimum hardware cost and modifications. The design and implementation of novel spatio-temporal phase sampling methods utilize the high temporal resolution (i.e., \u3c 5 us exposure) and frame rate (i.e., \u3e80,000 fps) of high-speed cameras without imposing constraints on their spatial resolution (i.e., \u3e20 um pixel size). Additionally, the research and in-vivo applications capabilities of the HHS are extended through the development and implementation of a holographic otoscope head (OH) and a mechatronic otoscope positioner (MOP). The large (i.e., \u3e 1 GB with \u3e 8x10^9 parameters) spatio-temporal data sets of the HHS measurements are automatically processed by custom parallel data mining and interpretation (PDMI) methods, which allow automatic quantification of medically relevant motion parameters (MRMPs), such as modal frequencies, time constants, and acoustic delays. Such capabilities could allow inferring local material properties across the surface of the TM. The HHS is a new medical tool that enables otologists to improve the quality of diagnosis and treatments as well as provides researchers with spatio-temporal information of the hearing process at a level of detail never reached before