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1
Bhargava, Rajat. "Simulation models for variable speed electric drives." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq22571.pdf.
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Stefani, Andrea <1976>. "Induction Motor Diagnosis in Variable Speed Drives." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amsdottorato.unibo.it/2311/.
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Several diagnostic techniques are presented for the detection of electrical fault in induction motor variable speed drives. These techinques are developed taking into account the impact of the control system on machine variables and non stationary operating conditions.
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Maggs, John David. "Electromagnetic interference from variable speed motor drives." Thesis, Aston University, 1996. http://publications.aston.ac.uk/15347/.
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A methodology is presented which can be used to produce the level of electromagnetic interference, in the form of conducted and radiated emissions, from variable speed drives, the drive that was modelled being a Eurotherm 583 drive. The conducted emissions are predicted using an accurate circuit model of the drive and its associated equipment. The circuit model was constructed from a number of different areas, these being: the power electronics of the drive, the line impedance stabilising network used during the experimental work to measure the conducted emissions, a model of an induction motor assuming near zero load, an accurate model of the shielded cable which connected the drive to the motor, and finally the parasitic capacitances that were present in the drive modelled. The conducted emissions were predicted with an error of +/-6dB over the frequency range 150kHz to 16MHz, which compares well with the limits set in the standards which specify a frequency range of 150kHz to 30MHz. The conducted emissions model was also used to predict the current and voltage sources which were used to predict the radiated emissions from the drive. Two methods for the prediction of the radiated emissions from the drive were investigated, the first being two-dimensional finite element analysis and the second three-dimensional transmission line matrix modelling. The finite element model took account of the features of the drive that were considered to produce the majority of the radiation, these features being the switching of the IGBT's in the inverter, the shielded cable which connected the drive to the motor as well as some of the cables that were present in the drive.
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Larbes, Cherif. "Boost modulation : control of AC variable speed drives." Thesis, Lancaster University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304281.
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Khan, Hamid. "Optimised space vector modulation for variable speed drives." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2012. http://tel.archives-ouvertes.fr/tel-00999475.
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The dissertation documents research work carried out on Pulse Width Modulation (PWM) strategies for hard switched Voltage Source Inverters (VSI) for variable speed electric drives. This research is aimed at Hybrid Electric Vehicles (HEV). PWM is at the heart of all variable speed electric drives; they have a huge influence on the overall performance of the system and may also help eventually give us an extra degree of freedom in the possibility to rethink the inverter design including the re-dimensioning of the inverter components.HEVs tend to cost more than conventional internal combustion engine (ICE) vehicles as they have to incorporate two traction systems, which is the major discouraging factor for consumers and in turn for manufacturers. The two traction system increases the maintenance cost of the car as well. In addition the electric drives not only cost extra money but space too, which is already scarce with an ICE under the hood. An all-electric car is not yet a viable idea as the batteries have very low energy density compared with petrol or diesel and take considerable time to charge. One solution could be to use bigger battery packs but these add substantially to the price and weight of the vehicle and are not economically viable. To avoid raising the cost of such vehicles to unreasonably high amounts, autonomy has to be compromised. However hybrid vehicles are an important step forward in the transition toward all-electric cars while research on better batteries evolves. The objective of this research is to make electric drives suitable for HEVs i.e. lighter, more compact and more efficient -- requiring less maintenance and eventually at lower cost so that the advantages, such as low emissions and better fuel efficiency, would out-weigh a little extra cost for these cars. The electrical energy source in a vehicle is a battery, a DC Voltage source, and the traction motor is generally an AC motor owing to the various advantages it offers over a DC motor. Hence the need for a VSI, which is used to transform the DC voltage into AC voltage of desired amplitude and frequency. Pulse width modulation techniques are used to control VSI to ensure that the required/calculated voltage is fed to the machine, to produce the desired torque/speed. PWM techniques are essentially open loop systems where no feedback is used and the instantaneous values differ from the required voltage, however the same average values are obtained. Pulse width modulated techniques produce a low frequency signal (desired average value of the switched voltage) also called the fundamental component, along with unwanted high frequency harmonics linked to the carrier signal frequency or the PWM period. In modern cars we see more and more mechanical loads driven by electricity through digital processors. It is very important to eliminate the risk of electromagnetic interference between these systems to avoid failure or malfunction. Hence these unwanted harmonics have to be filtered so that they do not affect the electronic control unit or other susceptible components placed in the vicinity. Randomised modulation techniques (RPWM) are used to dither these harmonics at the switching frequency and its multiple. In this thesis a random modulator based on space vector modulation is presented which has additional advantages of SVM. Another EMI problem linked to PWM techniques is that they produce common mode voltages in the load. For electric machines, common mode voltage produces shaft voltage which in turn provokes dielectric stress on the motor bearings, its lubricant and hence the possibility of generating bearing currents in the machine that can be fatal for the machine. To reduce the common mode voltage a space vector modulation strategy is developed based on intelligent placement of zero vectors. (...)
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Okaeme, Nnamdi. "Automated robust control system design for variable speed drives." Thesis, University of Nottingham, 2008. http://eprints.nottingham.ac.uk/10584/.
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Traditional PI controllers have been largely employed for the control of industrial variable speed drives due to the design ease and performance satisfaction they provide but, the problem is that these controllers do not always provide robust performance under variable loads. Existing solutions present themselves as complex control strategies that demand specialist expertise for their implementation. As a direct consequence, these factors have limited their adoption for the industrial control of drives. To counter this trend, the thesis proposes two techniques for robust control system design. The developed strategies employ particular Evolutionary Algorithms EA), which enable their simple and automated implementation. More specifically, the EA employed and tested are the Genetic Algorithms (GA), Bacterial Foraging (BF) and the novel Hybrid Bacterial Foraging, which combines specific desirable features of the GA and BF. The first technique, aptly termed Robust Experimental Control Design, employs the above mentioned EA in an automated trial-and-error approach that involves directly testing control parameters on the experimental drive system, while it operates under variable mechanical loads, evolving towards the best possible solutions to the control problem. The second strategy, Robust Identification-based Control Design, involves a GA system identification procedure employed in automatically defining an uncertainty model for the variable mechanical loads and, through the adoption of the Frequency Domain H-infinity Method in combination with the developed EA, robust controllers for drive systems are designed. The results that highlight the effectiveness of the robust control system design techniques are presented. Performance comparisons between the design techniques and amongst the employed EA are also shown. The developed techniques possess commercially viable qualities because they elude the need for skilled expertise in their implementation and are deployed in a simple and automated fashion.
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Scheidiger, Michael. "Power System Harmonics Analysis of HighPower Variable Speed Drives." Thesis, KTH, Elektrisk energiomvandling, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-153676.
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Power system harmonics are a topic of significant concern when considering power quality issues in systems containing Variable Speed Drives. The extent to which grid-connected power electronics based motor drives affect power quality is tightly enforced through standards, and must be adhered to. To ensure compliance, harmonic models of Variable Speed Drives and relevant components of the connected power system are evaluated. When necessary, analysis results can be used to aid the design of additional harmonic mitigation measures. Harmonic assessments are most commonly carried out using time-domain models. This thesis details the fundamentals of harmonic assessment and mitigation measure design. Matlab implementations of those fundamentals are discussed, with comments regarding the accuracy and limitations of each. State of the art analytical harmonic models for Voltage Source Variable Speed Drives are analyzed and compared, from which a new model for 3-level inverter Variable Speed Drives is proposed. The new model can be implemented in any numerical computing environment and is thought to generate a harmonic current spectrum for an approximate judgement of harmonic compliance based on the current injection method.Övertoner i kraftsystem innehållande frekvensomriktare är ett viktigt ämne när el-kvalité behandlas. Den grad nätanslutna elektroniska motorsystem påverkar el-kvalitén är noggrant upprätthållen av standarder och måste följas därefter. För att säkerställa att standarder upprätthålls utvärderas modeller för frekvensomriktare och relevanta komponenter. När det anses nödvändigt kan resultaten vara vägledande för design av ytterligare övertonsminskande åtgärder. Utvärdering av övertoner görs i allmänhet med hjälp av modeller i tidsdomän. Denna uppsats går igenom grunderna för bedömning av övertoner och design av övertonsminskande åtgärder. Matlab-modeller av dessa diskuteras i termer av precision och begränsningar. De främsta analytiska modeller for frekvensomriktare undersöks och jämförs, varefter en ny modell av en växelriktare med 3 nivåer föreslås. Denna modell kan med enkelhet implementeras i numeriska datormiljöer och framställer ett frekvensspektrum av strömmen för en approximativ bedömning av el-kvalité baserad på ströminmatningsmetoden.
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Allaith, Noori A. "Intelligent power module for variable speed AC motor drives." Thesis, University of Bristol, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361134.
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Midoun, A. "PWM strategies for microprocessor control of variable speed drives." Thesis, University of Bristol, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.232790.
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Wheeler, Patrick W. "A matrix converter for variable speed AC motor drives." Thesis, University of Bristol, 1993. http://hdl.handle.net/1983/1eec4275-808a-4125-813b-4f6e00881f44.
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賴志強 and Chi-keung Lai. "Dynamic response of a variable speed pumping system." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1994. http://hub.hku.hk/bib/B31212360.
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Lai, Chi-keung. "Dynamic response of a variable speed pumping system /." Hong Kong : University of Hong Kong, 1994. http://sunzi.lib.hku.hk/hkuto/record.jsp?B20666305.
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Refoufi, L. "Steady state analysis of the chopper controlled static Kramer drive." Thesis, University of Newcastle Upon Tyne, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239814.
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Lewin, Paul Leonard. "Microprocessor control of a switched reluctance motor." Thesis, University of Southampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262359.
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Clark, Paul R. "Optimum PWM strategies for microprocessor controlled three phase inverters." Thesis, University of Bristol, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357755.
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Benidir, Mohamed. "A study of variable speed drives for the mining industry." Thesis, University of Nottingham, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254427.
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Chikwanda, Herbert Simbarashe. "The naturally commutated, converter-fed, variable speed induction machine drive." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/47805.
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Rouaud, Didier G. "Harmonic mitigation using a modified slip energy recovery system." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/14806.
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Magill, Robert Joseph. "Efficiency and loss evaluation of induction motors for variable speed drives." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367160.
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Sagar, Pidaparthi. "A knowledge-based control system model for variable speed a.c. drives." Thesis, Open University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253731.
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Abdessemed, Yassine. "The application of GTO thyristor in PWM variable-speed AC drives." Thesis, University of Bristol, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332278.
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Blödt, Martin Faucher Jean Regnier Jérémi. "Condition monitoring of mechanical faults in variable speed induction motor drives." Toulouse : INP Toulouse, 2006. http://ethesis.inp-toulouse.fr/archive/00000313.
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Torrey, David Allan. "Optimal-efficiency constant-speed control of nonlinear variable reluctance motor drives." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14713.
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Lovelace, Edward Carl Francis. "A mechanical-state observer for high-speed variable-reluctance motor drives." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/40232.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996, and Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1996.Includes bibliographical references (p. 191-192).
by Edward Carl Francis Lovelace.
M.S.
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Wu, Yunxiang. "A power loss study of small-to-medium variable speed drives." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611481.
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Anyang, Ernest Ohene. "The impact of variable speed drives on energy efficient induction motors." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/10028.
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Includes abstract.Includes bibliographical references.
In an era when the world is faced with diminishing resources and energy security concerns, the slightest energy savings can prove essential in energy conservation. Induction motors and motorised loads consume an estimated 60% of the total energy required in the South African industry. This figure stands at 40% worldwide. Energy Efficient induction motors have proven to be an effective solution in the quest to reduce energy consumption. In South Africa, there have been efforts to replace the standard motors already in operation with energy efficient motors. The South African Utility, ESKOM, through its energy efficiency motor programme, has been providing incentives to its industrial customers to speed up this process.
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Anderson, John A. "Designing and modeling a torque and speed control transmission (TSCT)." Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=1194.
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Thesis (M.S.)--West Virginia University, 1999.Title from document title page. Document formatted into pages; contains viii, 69 p. : ill. Includes abstract. Includes bibliographical references (p. 68-69).
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Shehada, Ahmed. "Novel Multilevel Converter for Variable-Speed Medium Voltage Switched Reluctance Motor Drives." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/85111.
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A novel multilevel converter that is especially suited for high speed multi-megawatt switched reluctance motor drives operating at the medium voltage level is presented. The drive is capable of variable speed, four-quadrant operation. Each phase leg of the converter contains an arbitrary number of cascaded cells connected in series with the phase winding. Each cell contains a half-bridge chopper connected to a capacitor. The converter is named the cascaded chopper cell converter. The modular nature of the converter with the ability to add redundant cells makes it very reliable, which is a key requirement for medium voltage drive applications. A comprehensive control algorithm that overcomes the challenges of balancing and controlling cell capacitor voltages is also proposed. A suitable startup algorithm to limit startup current and switching losses, as well as ensure that cell capacitor voltages remain controlled at startup, is suggested. Details of the drive design such as component sizing and control parameter selection are also discussed. A detailed simulation model is developed and explained, and simulation results are provided for primary validation. Operation with standard current and speed control is first simulated. Then a scheme that gives way to a controller that operates the drive in single-pulse mode is developed and presented. This single-pulse control scheme controls the turn-on and turn-off angles, as well as the energization voltage level, in order to obtain high efficiency. Practical considerations related to the drive such as reliability, efficiency, and cost considerations are also discussed. Finally, a detailed comparison of the proposed converter to another competing converter is performed. Besides its scalability to high voltages and powers, the reliability and efficiency of the proposed converter makes it also a candidate for sub-megawatt applications requiring minimum downtime, or any application where high efficiency or improved performance is required.
A small part of this work is also dedicated to brushless dc machines. Control methods for a new converter for brushless dc machines are proposed and verified via simulation. The main advantage of this converter with the proposed control is that it allows exact control of torque or speed up to twice the rated speed, without resorting to current phase advancing or other flux-weakening techniques.Ph. D.
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Kim, Jaehyuck. "Variable-Speed Switched Reluctance Motor Drives for Low-Cost, High-Volume Applications." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/77320.
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Demand for energy-saving variable speed drives in low-cost, high-volume appliances has increased due to energy and environmental concerns and hence the need to comply with new regulations. Switched reluctance motor (SRMs) have been considered by many as attractive alternatives for brush commutated motors or permanent magnet brushless dc motors (PMBDCMs) in such cost-sensitive applications. The SRMs' unique features such as simple and fault-tolerant structure and unidirectional flow of their phase currents endow them with the possibility of various configurations on both machine and converter topologies for different applications. In the present study, three different variable-speed motor drive systems are proposed, studied, and implemented for their deployment in low-cost, high-volume applications with the power rating of 1.5kW or less. Two different two-phase SRMs and three different power converters are employed to realize three different low-cost drive systems. The first drive system is realized using a novel converter requiring only a single-controllable switch and an asymmetric two-phase 8/4 SRM capable of self-starting and four-quadrant operation. The second drive system is realized using another novel converter requiring two controllable switches, that way to achieve better control and utilization of the asymmetric 8/4 motor. The target applications for both drive systems are low power, low performance drives such as fans, hand tools, small appliances, etc. The third system is realized using a high-speed two-phase 4/2 SRM and a split ac source converter, which is designed for high-speed applications such as vacuum cleaners, ultracentrifuges, etc. The control and design aspects for each drive system are studied. Selection of optimal firing angles and optimal number of winding turns are also investigated. All of the drive systems are first demonstrated on the position sensor-based speed-control scheme. To make the drive system even more cost-competitive, operation without the position sensor using the novel parameter insensitive sensorless control scheme is proposed and implemented. Concept, analysis, simulation, and experimental verification of the proposed sensorless scheme are discussed in detail.Ph. D.
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Thian, Boon Meng. "Methods for monitoring the condition of electrical machines fed from variable speed drives." Thesis, University of Aberdeen, 1991. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU034117.
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This thesis is concerned with the investigation and development of methods to monitor the condition of electrical machines, with particular reference to induction machines fed from variable frequency, power electronic supplies. A variety of techniques are suggested whereby the faults that most commonly afflict electrical machines can be identified. Techniques involving the detection and analysis of line current, frame vibration, and leakage magnetic field are proposed and developed to take account of the rich spectrum of harmonics that can be injected through the use of power electronic inverters. To do this it was necessary to produce methodologies that could differentiate between spectral components originating in the inverter, and those produced as a result of the fault. As an extension, two further monitoring techniques were developed in an attempt to provide a fully comprehensive strategem for assessing the health of electrical drives. They are sequence component monitoring, and pulsed eddy current monitoring. The former is an adjunct to those techniques previously mentioned, and when used in combination with them leads to a greater security of diagnosis. The use of pulsed eddy currents is aimed at the on line detection of material failure in the rotating shafts of the machines. For each technique suggested, a comprehensive theoretical basis is provided, and its effectiveness verified by suitable experiment.
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Hart, S. D. "Parameter optimisation and state estimation for machine control." Thesis, University of Surrey, 2001. http://epubs.surrey.ac.uk/843955/.
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This thesis is concerned with the modelling of electrical machines for use in variable-speed drives. Even when the structure of the model of the machine is known values have to be assigned to the parameters. In addition, it is usual for only some of the state variables to be measured, any others needed being estimated using the model. The present work is a study of methods of making on-line estimates of the model parameters, using a reduced number of measured states. To offer high level dynamic torque control the non-measured state variables must be indirectly estimated to a high degree of accuracy throughout the complete range of operating conditions. The state estimator is generally classified with respect to the degree of structural complexity. At one end of the spectrum the model is constructed with a very high level of complexity in order to describe fully the system during any operating conditions. Because of this structural accuracy, the model parameters can be fixed prior to running the machine under normal conditions. However, this scheme suffers from a high computational burden in the state estimation process, and requires sophisticated commissioning strategies in order to permit the complete identification of the relatively large parameter set. The alternative is to use a simpler model structure and update the parameters with sufficient speed on-line in order to compensate for the inherently larger structural error. In this thesis the latter method is considered and preferred, as it has a greater robustness to unforeseen system behaviour and is more compatible with existing control strategies. As a consequence of the simple estimator the identification scheme has to compensate for the considerable structural errors. To this end the strategy of full parameter set identification is described. Work has also been done, and is presented, concerning on-line parameter identification using genetic optimisation techniques, which are shown to be well suited to this type of problem. The first studies of modelling and parameter extraction were concerned with dc machines, for these were thought to be simpler to model and to understand. DC machines are also different, in that the simple model includes mechanical parameters, and so represents a more complete system than the models of the ac machine studied later. A number of standard, enhanced and novel parameter identification methods are analysed and implemented on a practical machine and drive test bench. Also included were state estimators, intended to permit speed-sensorless control; however, the limitations on the experimental rig, based as it was around a commercially available drive, meant that some of the testing had to be done by running the estimator off-line, using data recorded from actual runs as the input. The thesis is primarily concerned with the induction machine and specifically the parameters required to permit field and speed sensorless rotor field orientated vector control. Sufficient work was done to allow a preliminary experimental comparison of a number of algorithms. At this stage it appears that several of these could be developed into successful drives, the precise choice depending on the specific application.
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Murphy, Tyson M. "A Method for Evaluating the Application of Variable Frequency Drives with Coal Mine Ventilation Fans." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/31908.
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The adjustable-pitch setting on an axial-flow fan is the most common method of controlling airflow for primary coal mine ventilation. With this method, the fan operates at a constant speed dictated by its motor design. The angles of the blades are adjusted to change the amount of airflow and pressure to meet ventilation requirements. Typically, the fan does not operate at its optimum efficiency, which only occurs in a narrow band of air pressures and quantities. The use of variable frequency drives (VFDs), which control fan speed, provides a solution to this problem. VFDs are already used in various similar applications such as pumping and building ventilation. New technology now enables efficient VFD operation in medium voltage (2,300 â 6,900 V) fan applications. The primary benefit of a variable frequency drive is that it allows motors to operate at reduced speeds, and thus at a lower power, without a loss of torque. VFDs also allow for efficient operation over the entire life of the fan. The technical considerations of using a VFD are presented in this work, along with a method for choosing and modeling a variable speed fan to achieve maximum energy savings. As a part of this research, a spreadsheet program was developed that will calculate the optimum fan operating speed based on given fan data and specified operating conditions. A representative room and pillar coal mine is modeled to illustrate the selection and modeling process and as an example of the economic implications of using a VFD. The use of VFDs is shown to potentially yield large energy savings by increasing the fan efficiency over the life of the mine. Although there are definite power savings while using variable speed fans, the magnitude of these savings is specific to an individual mine and the operating conditions encountered. The determination of whether the use of VFDs is economically feasible requires analysis for the specific mine and its operating conditions. This work provides the background and a method for such an evaluation.Master of Science
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Caliskan, Hakan. "Modeling And Experimental Evaluation Of Variable Speed Pump And Valve Controlled Hydraulic Servo Drives." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12611090/index.pdf.
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In this thesis study, a valveless hydraulic servo system controlled by two
pumps is investigated and its performance characteristics are compared with a
conventional valve controlled system both experimentally and analytically. The
two control techniques are applied on the position control of a single rod linear
actuator. In the valve controlled system, the flow rate through the actuator is
regulated with a servovalvewhereas in the pump controlled system, two variable speed pumps driven by servomotors regulate the flow rate according to the needs of the system, thus eliminating the valve losses. To understand the dynamic behaviors of two systems, the order of the differential equations defining the system dynamics of the both systems are reduced by using the fact that the dynamic pressure changes in the hydraulic cylinder chambers become linearly dependent on leakage coefficients and cylinder chamber volumes above and below some prescribed cut off frequencies. Thus the open loop speed response of the pump controlled and valve controlled systems are defined by v second order transfer functions. The two systems are modeled in MATLAB Simulink environment and the assumptions are validated. For the position control of the single rod hydraulic actuator, a linear state feedback control scheme is applied. Its state feedback gains are determined by using the linear and linearized reduced order dynamic system equations. A linear Kalman filter for pump controlled system and an unscented Kalman filter for valve controlled system are designed for estimation and filtering purposes. The dynamic performances of both systems are investigated on an experimental test set up developed by conducting open loop and closed loop frequency response and step response tests. MATLAB Real Time Windows Target (RTWT) module is used in the tests for application purposes.
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Satiawan, I. Nyoman Wahyu. "Pulse width modulation control of dual-inverter supply for five-phase variable-speed drives." Thesis, Liverpool John Moores University, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.585478.
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Three-phase multi-level topologies have been drawing increased attention in the past two decades. The numerous advantages of multi-level supply include: good power quality (low voltage distortion and dv/dt), good electromagnetic compatibility, operation with a lower switching frequency (lower switching losses), high voltage capability, smaller common mode (CM) voltage (reducing the stress in the motor bearings). There are various topologies of multilevel converters. The main ones are the neutral point clamped (NPC), the flying capacitor (FC) and the cascaded converters. Another alternative is the dual two-level inverter configuration supplying an open-end winding machine. This topology has received growing attention due to its simple structure. The open-end topology has the advantages that the additional diodes used in the neutral- point-clamped (NPC) voltage source inverter (VSI) are not needed, leading to a saving in the overall number of components. Furthermore, the issue of proper capacitor voltage balancing does not exist if the supply is two-level at each winding side. Application of such a dual-inverter supply (with equal DC-links) enables drive operation with voltage waveform equivalent to the one obtainable with a three-level VSI. The advantages of multi-phase variable speed drives over the three-phase ones are numerous and include an increase of fault tolerance, the possibility to have several multi-phase machines connected in series and drive them independently with a single VSI and, when the machine is equipped with a concentrated winding, other, higher harmonics can also be used to increase the developed torque. This thesis explores the possibility of combining the multi-phase and open-end- winding multi-level topologies. In particular the five-phase open-end-winding topology is considered. General properties of the five-phase AC motor drives with sinusoidal winding distribution are at first reviewed, along with the previously developed two- level space-vector modulation algorithm for a five-phase two-level VSI. A mathematical model of the converter is developed and a detailed study of the available switching states and corresponding voltage space vectors is conducted. It is shown that, due to the large number of switching states available in the topology together with the additional requirements when driving a multi-phase machine, the design of a suitable modulation scheme is extremely challenging. Three different space-vector modulation methods are proposed in the thesis. The developed methods are relatively simple to implement since they consider each inverter individually hence breaking down the problem into one of simpler complexity. The three modulation methods and the performance of the five- phase drive are verified using simulations. Finally, a laboratory prototype is described, which utilises two two-level five- phase inverters connected across an open-end-winding five-phase induction machine. The three modulation schemes are implemented using a fast prototyping control system (dSP ACE) and the performance of the modulation techniques is compared. The motor is controlled in V/fmode, in open loop. It is demonstrated that two of the methods produce multi-level output waveforms and that one method offers superior performance, with reduced converter losses.
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Teotrakool, Kaptan. "Adjustable speed drive bearing fault detection via support vector machine incorporating feature selection using genetic algorithm." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/4845.
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Thesis (Ph. D.)--University of Missouri-Columbia, 2007.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on March 3, 2008) Vita. Includes bibliographical references.
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Neuroth, Matthias. "Design, implementation and performance of conventional and intelligent control schemes and speed estimators for variable speed induction motor drives." Thesis, University of Aberdeen, 1999. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU177656.
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This thesis discusses the implementation and performance of various conventional and artificial-intelligence-based control and estimation techniques for variable speed induction motor drives. The drive types considered are scalar drives, and high-performance vector and direct torque controlled drives. In the first part, various conventional control design techniques are developed and applied to conventionally controlled drives. The performance of these drives is compared to that of fuzzy logic controlled drives, for which a specific design method is developed using universal fuzzy logic controllers. The developed methods are studied using simulations and experimental results. Implementation issues are presented in detail. In the second part, the design and implementation of conventional and artificial-intelligence-based speed estimators for use in scalar, vector and direct torque controlled drives are discussed. The conventional estimators considered comprise both a mathematical-model-based speed estimator and a model-reference-adaptive-system-based speed estimator. The artificial-intelligence-based estimators considered use artificial neural networks which are trained on data collected in simulations. The performance of both types of estimator, in the entire operating range of the drive, is discussed extensively.
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Essah, David N. "New modeling techniques for power electronics based systems with application to switched reluctance drives /." free to MU campus, to others for purchase, 1999. http://wwwlib.umi.com/cr/mo/fullcit?p9962521.
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Jasim, Omar. "An extended induction motor model for investigation of faulted machines and fault tolerant variable speed drives." Thesis, University of Nottingham, 2010. http://eprints.nottingham.ac.uk/11285/.
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High performance variable speed induction motor drives have been commercially available for industrial applications for many years. More recently they have been proposed for applications such as hybrid automotive drives, and some pump applications on more electric aircraft. These applications will require the drive to operate in the presence of faults i.e. they must be “Fault Tolerant” and be capable of “Fault Ride Through”. The aim of this project was therefore to investigate fault ride through control strategies for induction motor drives, particularly with respect to open circuit winding or power converter faults. Three objectives were identified and addressed to meet this aim. a) A new simulation model for an induction motor was created which reflects both saturation and space harmonics effects within the drive under both symmetric (healthy) and asymmetric (faulted) conditions. The model has a relatively low computational requirement to allow it to be used in conjunction with the simulation of high performance control algorithms and power electronic equipment. For operation in both healthy and faulty conditions, comparisons show that the simulated saturation and space harmonic effects match those obtained from an experiment system. Therefore this model is a very useful tool for the development and optimisation of new control strategies for fault tolerant drive systems. b) A novel on-line fault detection and diagnosis algorithm based on the measurement of the third harmonic component in the motor line currents has been proposed. The location of the open circuit fault is detected based on detecting a magnitude reduction for the third harmonic component of the current flowing to the motor terminals, and can be implemented in real time to give a fast response with little additional computational overhead. c) A new open circuit fault tolerant control strategy has been designed for a delta connected induction machine suddenly affected by an open circuit winding fault. The fault ride through is achieved without any modification to either the power converter or the motor circuit. A novel feedforward compensation algorithm is introduced which considerably reduces the current and the torque ripple in the faulted drive motor. Two methods for controlling the neutral point voltage are also presented so that the available voltage capacity of the inverter is maximised in both normal and fault mode. For high speed operation, two different methods for field weakening control are presented, so that the available voltage capacity is maximized in both normal and fault mode. This thesis describes the theoretical derivation of the new models and algorithms, and presents experimental results from a 4kW laboratory prototype to validate the proposals. The full fault tolerant system is experimentally demonstrated on a delta connected machine which suffers an open circuit winding fault. The improved motor performance under fault conditions is clearly seen.
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Salib, Anton Samir. "Voltage Sag Ride-Through and Harmonics Mitigation for Adjustable Speed Drives using Dual-Functional Hardware." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/2834.
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Great portion of today's industry are Adjustable Speed Drives (ASD's) operated in order to fulfill certain processes. When these processes are critical ones or sensitive to voltage disturbances, that might take place due to inserting high load in an area near to the Point of Common Coupling (PCC) of the process or due to a short term outage, few tens of thousands up to millions of dollars will be lost once such interruptions (voltage sags) take place as a result of the process failure. On the other hand, a distorted voltage waveform at the PCC for some sensitive process might malfunction as a result of the high harmonic content of the voltage waveform. Utilities are required to deliver as pure as possible sinusoidal voltage waveform according to certain limits; thus, they might apply fines against the consumers who are responsible for producing high amounts of current harmonics that affect the voltage wave shape at the PCC in order to force them to improve the consumer's load profile by adding filters at PCC for instance. Utilities are charging the consumers who are drawing power at poor power factor as well. This thesis presents an ASD retrofitted with a dual-functional piece of hardware connected in series to its DC-link that is capable of handling the previously two mentioned problems. In other words, hardware that is capable of providing voltage sag ride-through during the voltage sag conditions on one side, on the other side, during the normal operating conditions, it is capable to mitigate the harmonic contents of the drawn current by the ASD's rectifier and to improve the power factor.
Survey on voltage sag ride-through for ASD's approaches are presented in the literature has been made. Approaches are classified as the topology utilized; first, topologies that utilizes energy storage elements that store energy to compensate the DC-link voltage with during the voltage sags, second, topologies retrofitting the DC-link itself with additional hardware to compensate the DC-link voltage. The first group is capable to provide voltage compensating during the full outages while the second can't. The presented voltage sag ride-through work of this thesis belongs to the second group.
Boost converter has been used as the hardware to compensate the DC-link voltage because of its simplicity and cheap price. An adaptive linear network (ADALINE) is investigated as the detection system to detect the envelope of the input voltage waveform. Once the envelope of the voltage goes below a certain level, the boost converter is activated to compensate the difference between voltage set point and the actual DC-link voltage. Simulation results supporting the proposed configuration are presented.
A third-harmonic current injection approach is utilized in this work in order to achieve total harmonic distortion (THD) mitigation from 32% to 5. 125% (theoretically). Two third-harmonic current injection networks have been investigated; one utilizes a real resistor, the other utilizes a resistor emulator to reduce the energy dissipated. The proposed controller for the resistor emulator does not require a proportional-integral (PI) controller.
As a result of the common devices between the voltage sag ride-through circuitry and the harmonic mitigation one, they can be integrated together in one circuitry connected in series with the DC-link of the ASD. And hence, the dual functionality of the hardware will be achieved. Simulation results supporting the theoretical results have been presented.
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Rim, Geun-hie. "Variable speed constant frequency power conversion with permanent magnet synchronous and switched reluctance generators." Diss., Virginia Tech, 1992. http://hdl.handle.net/10919/40015.
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Halilovic, Amer. "Experimental Transient Behaviour Characterisation of Induction Motor fed by Variable Frequency Drives for Pump Applications." Thesis, KTH, Elektrisk energiomvandling, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-157319.
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The use of variable frequency drives in centrifugal pump applications has raised the question of how to select a drive. Clogging obstacles in waste water applications create unknown transient loads for the pump system. A sudden load increase occurrence can clog the pump if the drive cannot supply enough current to reach the motor’s torque demand. In order to select a suitable drive, an empirical approach has been implemented, investigating three different drives. Results have shown that selecting a drive with the highest possible overload capabilities, even if for a short time is most suitable. Operation in vector speed control gives the most reliable operation if an automatic parameter tuning is performed by the drive.Användningen av frekvensomriktare i centrifugalpumpar har väckt fr ågan om hur en omriktare skall väljas. Igensättande objekt i avloppsvatten kan ge upphov till transienta laster i pumpsystemen. En oförutsedd lastökning kan sätta igen pumpen om frekvensomriktaren inte kan förse motorn tillräckligt med ström för att möta momentbehovet. För att välja en lämplig omriktare har ett empiriskt tillvägag ångssätt valts i en undersökning av tre olika omriktare. Resultat har visat att det är lämpligast att välja en omriktare med högst överbelastningskapacitet, även om under en kort tid. Vektor hastighetskontroll är metoden som ger stabil körning om omriktaren f ått automatiskt ställa in motorparametrarna.
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Chandramouli, G. "Design of a PC based Data Acquistion System for a Switched Reluctance Motor." Thesis, Virginia Tech, 1988. http://hdl.handle.net/10919/44777.
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The Switched Reluctance Motors(SRM) have gained considerable attention in the
variable speed drive market mainly due to the simple construction of the motor and
the possibility of developing low cost converters and controllers. As these machines
are under development, a considerable amount of research effort is directed to the
experimental performance evaluation of the SRM drives. System efficiency,
electromagnetic torque, torque ripple, output and losses are some of the required
measurements.Master of Science
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Lee, Cheewoo. "Analysis and Design of a Novel E-Core Common-Pole Switched Reluctance Machine." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/77319.
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In this dissertation, a novel two-phase switched reluctance machine (SRM) with a stator comprised of E-core structure having minimum stator core iron is presented for low-cost high-performance applications. In addition, three new magnetic structures for the E-core SRM comprising two segmented stator cores or a monolithic stator core are proposed for good manufacturability, mechanically robustness, ease of assembly, and electromagnetic performance improvement. Each E-core stator in the segmented structure has three poles with two small poles at the ends having windings and a large center pole containing no copper windings. The common stator pole at the centers in the segmented E-core is shared by both phases during operation. Other benefits of the common poles contributing to performance enhancement are short flux paths, mostly flux-reversal-free-stator, constant minimum reluctance around air gap, and wide pole arc equal to one rotor pole pitch. Therefore, two additional common poles in the monolithic E-core configuration are able to significantly improve efficiency due to more positive torque and less core loss by the unique design. Using a full MEC analysis, the effect of the common-pole structure on torque enhancement is analytically verified. Efficiency estimated from the dynamic simulation is higher by 7% and 12% at 2000 rpm and by 3% and 7 % at 3000 rpm for the segmented and single-body SRMs, respectively, compared to a conventional SRM with four stator poles and two rotor poles. The new E-core SRMs are suitable for low-cost high-performance applications which are strongly cost competitive since all the new E-core SRMs have 20% cost savings on copper and the segmented E-core SRMs have 20% steel savings as well. Strong correlation between simulated and experimentally measured results validates the feasibility of the E-core common-pole structure and its performance. A simple step-by-step analytical design procedure suited for iterative optimization with small computational effort is developed with the information of the monolithic E-core SRM, and the proposed design approach can be applied for other SRM configurations as well. For investigating thermal characteristics in the two-phase single-body E-core SRM, the machine is modeled by a simplified lumped-parameter thermal network in which there are nine major parts of the motor assembly.Ph. D.
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Blödt, Martin. "Condition Monitoring of Mechanical Faults in Variable Speed Induction Motor Drives - Application of Stator Current Time-FrequencyAnalysis and Parameter Estimation." Phd thesis, Institut National Polytechnique de Toulouse - INPT, 2006. http://tel.archives-ouvertes.fr/tel-00105482.
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Ce travail de thèse traite de la détection et du diagnostic de défaillances mécaniques par analyse du courant statorique dans les entraînements électriques à base de machine asynchrone. Deux effets d'un défaut mécanique, des oscillations de couple et une excentricité d'entrefer, sont supposés. La modélisation par approche des ondes de forces magnétomotrices et de perméance conduit à deux modèles analytiques du signal courant. La conséquence des défauts est soit une modulation de phase, soit une modulation d'amplitude du signal courant statorique. Ces phénomènes sont détectés par une analyse spectrale en régime permanent, ou des méthodes temps fréquence en régime transitoire. Les méthodes étudiées sont la fréquence instantanée, le spectrogramme et la représentation de Wigner-Ville. L'estimation paramétrique d'indices de modulation a également été traitée. Des résultats de simulation et expérimentaux permettent de valider les signatures et d'extraire de façon automatique des indicateurs de défaut. De plus, une méthode permettant la distinction des oscillations de couple d'une excentricité dynamique est proposée. L'étude est complétée par une implémentation sur DSP des méthodes temps-fréquence afin de démontrer la faisabilité d'une surveillance en ligne.
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Rodrigues, Wlamir. "Criterios para o uso eficiente de inversores de frequencia em sistemas de bombeamento de agua." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258179.
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Orientador: Edevar Luvizotto JuniorTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
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Resumo: Instalações de bombeamento são comumente encontradas em qualquer sistema que envolva o transporte de líquidos, como sistemas públicos de abastecimento. Num passado não tão distante, os projetos dessas instalações eram superdimensionados e, na maioria das vezes, nunca chegavam a operar em sua plenitude. A operação de controle de vazão, através de uma válvula na saída da estação de bombeamento, sempre foi uma ação nociva a estrutura em todos os sentidos, além do desperdício de energia elétrica que esse tipo de operação provocava. Paralelamente, a energia elétrica se tornou muito dispendiosa, e a sua geração muito mais complicada com impactos cada vez maiores no meio ambiente. Em condições tão desfavoráveis, o inversor de freqüência se tornou peca importante na missão de racionalizar o uso da energia elétrica sem afetar a operação do sistema. Neste trabalho são estudadas duas instalações de bombeamento da cidade de Campinas ¿ SP, dotadas de inversores de freqüência, onde são comparadas operações com e sem o uso deste dispositivo, suas vantagens e desvantagens, possibilidades e limitações. Com o auxilio de três modelos matemático-computacionais, um que reproduziu uma das instalações, outro de auditoria energética e um terceiro de otimização, especialmente desenvolvidos para esse estudo, foi possível a simulação de cenários operacionais, buscando extrair a máxima eficiência do inversor e a conseqüente otimização do sistema como um todo. Ao final do trabalho são propostos critérios, resultantes do estudo desenvolvido, que podem servir como parâmetros quando da adoção de inversores de freqüência em sistema de bombeamento
Abstract: The pumping systems are frequently found in any process which involves transport of liquids, like the public water systems. In a recent past, these pumping systems plans were oversized and, frequently, did not work in their full potential. The flow regulated by throttling has always presented, in all senses, a harmful effect to the installation. Moreover, this kind of action has caused waste of electric energy. Along with that the cost of electric energy has been increasing and its production has created damages to the environment. Since we have so many negative conditions, the variable speed drive has become the most important part to rationalize the use of electric energy causing no affect on the operation of the system. This work studies two pump stations located in the city of Campinas, which are operated with variable speed drives. At these pumping stations, comparisons are made with and without the use of this equipment, considering its advantages and disadvantages, its possibilities and limitations. Three mathematicmodels were especially developed for this study, the first to reproduce one of the systems, the second to make an energetic audit and the third to optimize the results. Making use of these three models it was possible to simulate operational scenarios to reach the maximum efficiency from variable speed drive and the optimization of the system as a whole. As a conclusion of this study, some criteria are presented to support the use of variable speed drive in the pumping system
Doutorado
Recursos Hidricos
Doutor em Engenharia Civil
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Blödt, Martin. "Condition Monitoring of Mechanical Faults in Variable Speed Induction Motor Drives. Application of Stator Current Time-Frequency Analysis and Parameter Estimation." Phd thesis, Toulouse, INPT, 2006. http://oatao.univ-toulouse.fr/7468/1/blodt.pdf.
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This Ph.D. thesis deals with condition monitoring of mechanical failures in variable speed induction motor drives by stator current analysis. Two effects of a mechanical fault are considered: load torque oscillations and airgap eccentricity. The analytical modelling using the magnetomotive force and permeance wave approach leads to two stator current models. The fault provokes amplitude or phase modulation of the fundamental current component. Suitable detection methods are spectral analysis and parameter estimation in steady state whereas time-frequency analysis is required during transients. Instantaneous frequency estimation, the Wigner Distribution and the spectrogram are studied. Simulation and experimental results validate the theoretical approach. Automatic extraction of fault indicators is proposed for an unsupervised monitoring system. Moreover, load torque oscillations and dynamic eccentricity can be discriminated with the proposed methods. The feasibility of an on-line monitoring system is demonstrated by a DSP implementation of the time-frequency analysis including indicator extraction.
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Athanasiadis, Nikolaos P. "Modelling, control and design of Flexible AC Transmission Systems (FACTS), custom power devices and variable speed drives for transmission and distribution architectures." Thesis, University of Strathclyde, 1999. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21441.
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The main tasks of power electronics in power transmission and distribution systems is to process and control the flow of electric energy by supplying voltages and currents in a form that is suitable for user loads. In recent years, the field of power electronics has experienced a large growth. Electric utilities expected that by the year 2000 over half of the electrical load may be supplied through power electronic systems. In order to take advantage of this highly developed technology a number of detailed modelling procedures and simulation facilities are needed. The work in this thesis is concentrated on modelling, control and design of various power electronic based models for use within transmission and distribution systems. The overall objective is to provide effective methods and tools for assessing the impact of the latest technology based on power electronic devices in the reinforcement of power system networks. The thesis clarifies modelling and control of various variable speed drive models, such as the six-step, PWM and vector control and gives a detailed account of the systematic derivation of equations that are necessary for the dynamic and transient analysis of a multi-machine multi-node power system with associated adjustable speed drives. Simulation of Flexible AC Transmission Systems (FACTS) models has also been developed for a number of devices including: the SVC (Static Var Compensator), the STATCON (Static Condenser) and the UPFC (Unified Power Flow Controller). The methodologies for development of the models are described and a number of case studies are included in order to give a broad overview of the applications and to prove the usefulness of the results. The last part of the thesis includes simulation, control and design of Custom Power Devices for use within distribution system architectures. It starts with a complete control system strategy for the modelling of a solid-state switch and continues with the modelling of a Dynamic Voltage Restorer model, using an innovative control system. The creation of the power electronics models library provides several opportunities for future developments, which are discussed in the concluding sections of the thesis.
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Sagarduy, Ochoa de Eribe Juan. "Iron losses in non-oriented steel subjected to matrix and DC-link converter supply : an experimental and analytical study on variable speed drives." Thesis, Cardiff University, 2009. http://orca.cf.ac.uk/54924/.
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A system approach to variable speed drives consisting of two low voltage induction motors (Y and A connection) fed by matrix and two-level DC-link converters is developed (chapter 7). The ratio of iron to copper winding losses is studied based on the induction motor equivalent circuit and constant V/f converter control. Electrical efficiency increased by up to 10% (partial load and low speed) in Y-connected motors fed by the matrix converter. While similar values of efficiency were observed in A-configured motors, up to 8% higher output power is extracted from the machines under two-level DC-link converter supply.
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Ali, Emad, Jürgen Weber, and Matthias Wahler. "A Machine Learning Approach for Tracking the Torque Losses in Internal Gear Pump - AC Motor Units." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-199438.
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This paper deals with the application of speed variable pumps in industrial hydraulic systems. The benefit of the natural feedback of the load torque is investigated for the issue of condition monitoring as the development of losses can be taken as evidence of faults. A new approach is proposed to improve the fault detection capabilities by tracking the changes via machine learning techniques. The presented algorithm is an art of adaptive modeling of the torque balance over a range of steady operation in fault free behavior. The aim thereby is to form a numeric reference with acceptable accuracy of the unit used in particular, taking into consideration the manufacturing tolerances and other operation conditions differences. The learned model gives baseline for identification of major possible abnormalities and offers a fundament for fault isolation by continuously estimating and analyzing the deviations.
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Bouwer, Pieter. "Modelling, design and implementation of a small-scale, position sensorless, variable speed wind energy conversion system incorporating DTC-SVM of a PMSG drive with RLC filter." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80242.
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Thesis (MScEng)--Stellenbosch University, 2013.Wind energy has proven to be a viable source of clean energy, and the worldwide demand is growing rapidly. Variable speed topologies, with synchronous generators and full-scale converters, are becoming more popular, and the e ective control of these systems is a current trend in wind energy research. The purpose of this study is the modelling, design, simulation and implementation of a small-scale, variable speed wind energy conversion system, incorporating the position sensorless direct torque control with space vector modulation, of a permanent magnet synchronous generator, including an RLC converter lter. Another aim is the development of a gain scheduling algorithm that facilitates the high level control of the system. Mathematical models of the combined lter-generator model, in the stationary and rotating reference frames, are presented and discussed, from which equivalent approximate transfer functions are derived for the design of the controller gains. The design of the controller gains, RLC lter components, gain scheduling concept and maximum power point tracking controller are presented. It is discovered that the RLC lter damping resistance has a signi cant e ect on the resonance frequency of the system. The system is simulated dynamically in both Simulink and the VHDL-AMS programming language. Additionally, the maximum power point tracking controller is simulated in the VHDL-AMS simulation, including a wind turbine simulator. The simulation results demonstrate good dynamic performance, as well as the variable speed operation of the system. The practical results of torque and speed controllers show satisfactory performance, and correlate well with simulated results. The detailed gain scheduling algorithm is presented and discussed. A nal test of the complete system yields satisfactory practical results, and con rms that the objectives of this thesis have been reached.