This thesis presents different state estimation techniques for speed sensorlees field oriented control of induction motors. The theoretical basis of each algorithm is explained in detail and its performance is tested with simulations and experiments individually. First, a stochastical nonlinear state estimator, Extended Kalman Filter (EKF) is presented. The motor model designed for EKF application involves rotor speed, dq-axis rotor fluxes and dq-axis stator currents. Thus, using this observer the rotor speed and rotor fluxes are estimated simultaneously. Different from the widely accepted use of EKF, in which it is optimized for either steady-state or transient operations, here using adjustable noise level process algorithm the optimization of EKF has been done for both states / the steady-state and the transient-state of operations. Additionally, the measurement noise immunity of EKF is also investigated. Second, Unscented Kalman Filter (UKF), which is an updated version of EKF, is proposed as a state estimator for speed sensorless field oriented control of induction motors. UKF state update computations, different from EKF, are derivative free and they do not involve costly calculation of Jacobian matrices. Moreover, variance of each state is not assumed Gaussian, therefore a more realistic approach is provided by UKF. In this work, the superiority of UKF is shown in the state estimation of induction motor. Third, Model Reference Adaptive System is studied as a state estimator. Two different methods, back emf scheme and reactive power scheme, are applied to MRAS algorithm to estimate rotor speed. Finally, a flux estimator and an open-loop speed estimator combination is employed to observe stator-rotor fluxes, rotor-flux angle and rotor speed. In flux estimator, voltage model is assisted by current model via a closed-loop to compensate voltage model&rsquo / s disadvantages.

Induction motors are widely used in industrial processes. The malfunction of a motor may not only lead to high repair costs, but also cause immense financial losses due to unexpected process downtime. Since thermal overload is one of the major root causes of stator winding insulation failure, an accurate and reliable monitoring of the stator winding temperature is crucial to increase the mean time to catastrophic motor breakdown, and to reduce the extraordinary financial losses due to unexpected process downtime. To provide a reliable thermal protection for induction motors fed by motor control devices, a dc signal-injection method is proposed for in-service induction motors fed by soft-starter and variable-frequency drives. The stator winding temperature can be monitored based on the estimated stator winding resistance using the dc model of induction motors. In addition, a cooling capability monitoring technique is proposed to monitor the cooling capability of induction motors and to warn the user for proactive inspection and maintenance in the case of cooling capability deterioration. The proposed cooling capability monitoring technique, combined with the proposed stator winding temperature monitoring technique, can provide a complete thermal protection for in-service induction motors fed by motor control devices. Aside from online thermal protection during a motor's normal operation, the thermal protection of de-energized motors is also essential to prolong a motor's lifetime. Moisture condensation is one of the major causes to motor degradation especially in high-humidity environments. To prevent moisture condensation, a non-intrusive motor heating technique is proposed by injecting currents into the motor stator winding using soft-starters. A motor's temperature can be kept above the ambient temperature due to the heat dissipation, so that the moisture condensation can be avoided. To sum up, active stator winding temperature estimation techniques for induction motors under both operating and de-energization conditions are proposed in this dissertation for both thermal protection and optimizing the operation of a motor system. The importance of these proposed techniques lies in their non-intrusive nature: only the existing hardware in a motor control device is required for implementation; a motor's normal operation is not interrupted.

Multi-level inverters play a significant role in high power drive systems for induction motors. Interest in multi-level inverters started with the three-level, neutral point clamped (NPC) inverter. Now there are many topologies for higher number of levels such as the, flying capacitor and cascaded H-bridge etc. The advantage of multi-level inverters is the reduced voltage stress on the switching devices, lower dv/dt and lower harmonic content. The voltage space vector structure in a multi-level inverter has a hexagonal periphery similar to that in a two-level inverter. In the over-modulation region in multi-level inverters, there is the presence of lower order harmonics such as 5th and 7th in the output voltage, and this can be avoided by using a voltage space vector scheme with more than six polygonal voltage space vectors such as 12, 18, 24 etc. These polygonal voltage space vectors can be generated by using multi-level inverter topologies, by cascading two-level inverter structures with asymmetric DC-links. This thesis deals with the development of 12-sided and 18-sided polygonal voltage space vector schemes for induction motor drives. With the 12-sided polygonal structure, all the 5th and 7th harmonic orders and 6n±1, n=1, 3, 5.. are absent throughout the modulation range, and in the 18-sided voltage space vector scheme, 5th, 7th, 11th and 13th harmonics are absent throughout the modulation range. With the absence of the low order frequencies in the proposed polygonal space vector structures, high frequency PWM schemes are not needed for voltage control. This is an advantage over conventional schemes. Also, due to the absence of lower order harmonics throughout the modulation range, special compensated synchronous reference frame PI controllers are not needed in current controlled vector control schemes in over-modulation. In this thesis a method is proposed for generating 12-sided polygonal voltage space vectors for an induction motor fed from one side. A cascaded combination of three two-level inverters is used with asymmetrical DC-links. A simple space vector PWM scheme based only on the sampled reference phase amplitudes are used for the inverter output voltage control. The reference space vector is sampled at different sampling rates depending on the frequency of operation. The number of samples in a sector is chosen to keep the overall switching frequency around 1kHz, in order to minimize switching losses. The voltage space vectors that make up the two sides of the sector in which the reference vector lies, are time averaged using volt-sec balance, to result in the reference vector. In the proposed 12-sided PWM scheme all the harmonics of the order 6n±1, n=1, 3, 5... are eliminated from the phase voltage, throughout the modulation range. In multi-level inverters steps are taken to eliminate common-mode voltage. Common-mode voltage is defined as one third of the sum of the three pole voltages of the inverter for a three phase system. Bearings are found to fail prematurely in drives with fast rising voltage pulses and high frequency switching. The alternating common-mode voltage generated by the PWM inverter contributes to capacitive couplings from stator body to rotor body. This generates motor shaft voltages causing bearing currents to flow from rotor to stator body and then to the ground. There can be a flashover between the bearing races. Also a phenomenon termed EDM (Electro-discharge machining) effect occurs and may damage the bearings. Common-mode voltage has to be eliminated in order to overcome these effects. In multi-level inverters redundancy of space vector locations is used to eliminate common-mode voltages. In the present thesis a 12-sided polygonal voltage space vector based inverter with an open-end winding induction motor is proposed, in which the common-mode voltage variation at the poles of the inverter is eliminated. In this scheme, there is a three-level inverter on each side of the open-end winding of the induction motor. The three-level inverter is made by cascading two, two-level inverters with unequal DC-link voltages. Appropriate space vectors are selected from opposite sides such that the sum of the pole voltages on each side is a constant. Also during the PWM operation when the zero vector is applied, identical voltage levels are used on both sides of the open-end windings, in order to make the phase voltages zero, while the common-mode voltage is kept constant. This way, common-mode voltage variations are eliminated throughout the modulation range by appropriately selecting the voltage vectors from opposite ends. In this method all the harmonics of 6n±1, n=1, 3, 5.. and triplen orders are eliminated. In the 12-sided polygonal voltage space vector methods, the 11th and 13th harmonics though attenuated are not eliminated. In the 18-sided polygonal voltage space vector method the 11th and 13th harmonics are eliminated along with the 5th and 7th harmonics. This scheme consists of an open-end winding induction motor fed from one side by a two-level inverter and the other side by a three-level inverter comprising of two cascaded two-level inverters. Asymmetric DC-links of a particular ratio are present. The 12-sided and 18-sided polygonal voltage space vector methods have been first simulated using SIMULINK and then verified experimentally on a 1.5kW induction motor drive. In the simulation as well as the experimental setup the starting point is the generation of the three reference voltages v, vB and vC . A method for determining the sector in which the reference vector lies by comparing the values of the scaled sampled instantaneous reference voltages is proposed. For the reference vector lying in a sector between the two active vectors, the first vector is to be kept on for T1 duration and the second vector for T2 duration. These timing durations can be found from the derived formula, using the sampled instantaneous values of the reference voltages and the sector information. From the pulse widths and the sector number, the voltage level at which a phase in the inverter has to be maintained is uniquely determined from look-up tables. Thus, once the pole voltages are determined the phase voltages can be easily determined for simulation studies. By using a suitable induction motor model in the simulation, the effect of the PWM scheme on the motor current can be easily obtained. The simulation studies are experimentally verified on a 1.5kW open-end winding induction motor drive. A V/f control scheme is used for the study of the drive scheme for different speeds of operation. A DSP (TMS320LF2407A) is used for generating the PWM signals for variable speed operation. The 12-sided polygonal voltage space vector scheme with the motor fed from a single side has a simple power bus structure and it is also observed that the pole voltage is clamped to zero for 30% of the time duration of one cycle of operation. This will increase the overall efficiency. The proposed scheme eliminates all harmonics of the order 6n±1, n=1, 3, 5…for the complete modulation range. The 12-sided polygonal voltage space vector scheme with common-mode elimination requires the open-end winding configuration of the induction motor. Two asymmetrical DC-links are required which are common to both sides. The leg of the high voltage inverter is seen to be switched only for 50% duration in a cycle of operation. This will also reduce switching losses considerably. The proposed scheme not only eliminates all harmonics of the order 6n±1, n=1, 3, 5…for the complete modulation range, but also maintains the common-mode voltage on both sides constant. The common-mode voltage variation is eliminated. This eliminates bearing currents and shaft voltages which can damage the motor bearings. In the 18-sided polygonal voltage space vector based inverter, the 11th and 13th harmonics are eliminated along with the 5th and 7th. Here also an open-end winding induction motor is used, with a two-level inverter on one side and a three-level inverter on the other side. A pole of the two-level inverter is at clamped to zero voltage for 50% of the time and a pole of the three-level inverter is clamped to zero for 30% of the time for one cycle of operation. The 18-sided polygonal voltage space vectors show the highest maximum peak fundamental voltage in the 18-step mode of 0.663Vdc compared to 0.658Vdc in the 12-step mode of the 12-sided polygonal voltage space vector scheme and 0.637Vdc in the six-step mode of a two-level inverter or conventional multi-level inverter (where Vdc is the radius of the space vector polygon). Though the schemes proposed are verified on a low power laboratory prototype, the principle and the control algorithm development are general in nature and can be easily extended to induction motor drives for high power applications.

The analysis of the feature and application of linear induction motors at work have been performed; mathematical models of linear motors have been studied; mathematical description of induction machine have been presented; coordinate transform have been studied; dynamic equations in moving and move-less systems of axes of linear induction motor have been presented; the analysis of the classification of induction drives control modes have been performed. Four models of the frequency-regulated electric drives with linear induction motors have been studied: when the motor is supplied from variable frequency mains supply, when the motor is supplied from frequency converter, when frequency is changed by program, when frequency is changed in close-loop by vector control system. The characteristics of those models have been compared and performed. The received results are summarized in the conclusions.

Baigiamajame magistro darbe nagrinėjama elektros pavaros su tiesiaeigiu asinchroniniu varikliu konstrukciniai ypatumai, savybės, mechaninės charakteristikos bei kokybės rodikliai. Programiniu paketu MathCAD 2001 Professional yra sudarytas matematinis tiesiaeigio asinchroninio variklio modelis. Tyrimas atliekamas eksperimentiniu būdu, keičiant TAV parametrus (Reynoldso skaičių, neferomagnetinį sluoksnį, oro tarpą, induktoriaus plotį, variklio apvijų skaičių ir pan.), gaunamos tam tikram modeliui būdingos mechaninės charakteristikos. Magistro darbe pateikiama bendra elektros pavarų su tiesiaeigiais asinchroniniais varikliais apžvalga ir jų savybių analizė. Tiriamoji dalis apima apibendrinto tiesiaeigio asinchroninio variklio matematinio modelio sudarymą ir mechaninių charakteristikų tyrimą programiniu paketu MathCAD 2001 Professional. Programa skaičiavimo rezultatus pateikia grafiniu pavidalu. Gauti rezultatai yra analizuojami ir apibendrinami. Išnagrinėjus teorinius ir praktinius tiesiaeigio asinchroninio variklio darbo režimų aspektus, pateikiamos išvados ir pasiūlymai. Tyrimo rezultatai gali būti panaudoti elektros pavarų su tiesiaeigiais asinchroniniais varikliais racionaliam ir optimaliam realizavimui greitaeigių elektros pavarų technologinėse sistemose. Darbą sudaro 7 dalys, įvadas, literatūros elektros pavaros su tiesiaeigiu asinchroniniu varikliu klausimais apžvalga, tyrimo tikslas ir uždaviniai, skaičiuojamoji dalis, tyrimo rezultatų apibendrinimas, išvados ir... [toliau žr. visą tekstą] / In master thesis researching high-speed electric drive with Linear Induction Motor (LIM) design peculiarities, internals and indexes of quality. Using program MathCAD 2001 Professional was created mathematical model of Linear Induction Motor. By changing Linear Induction Motor parameters (Reynolds's number, SE thickness, air gap, inductor width, number of coils and etc) getting for the defined model appropriate mechanicals characteristics. In master thesis the view of electric drive with Linear Induction Motor has been reviewed and their features analyzed. In the investigation part involves the creation of Linear Induction Motor mathematical model and investigation of mechanicals characteristics on program pack MathCAD 2001 Professional. The program displays results in graphical form. The results are analyzed and generalized. After analyzing theoretical and practical LIM motor aspects of operations, conclusions and suggestions are formed. The results of research can be used for rational and optimal realization of LIM in various technological systems. Structure: introduction, literature electrical drive with LIM questions review, research purpose and tasks, calculation part, summary of research results, conclusions and suggestions, references.

In industrial drives market, requirements related to control quality and price of drives are important. In low cost drives, one of the aims is achieving speed estimation accuracy. Since motor parameters are required to estimate speed and sometimes it is impractical to do no-load and locked rotor tests, it is necessary to estimate motor parameters from motor label or by simple measurements. Throughout this study, some of parameter estimation and speed estimation methods found in literature are investigated and some new methods are proposed. These methods are applied to three induction motors and estimation results are compared with test results. Advantages and disadvantages of these methods are investigated. As a result of this study, the most suitable parameter and speed estimation methods amongst these methods are obtained for low cost motor drives.

In this thesis, a practical vector controlled elevator drive is presented. Indirect vector control of induction machine is investigated in theory and then implemented. Control technique is compared with scalar control and induction machine is compared with dc motor. The operation of the system depends on induction machine parameters, so how to accurately and automatically obtaining of the parameters is also presented. Finally, the elevator system is introduced, the application of this control system to the elevator system is described and a basic elevator control system is simulated.

O objetivo deste trabalho consiste na implementação de arquiteturas de sistema inteligentes em Processadores Digitais de Sinais (DSP) visando, sobretudo, o controle em tempo real de motores de indução trifásicos. Para tanto, propõe-se uma abordagem fuzzy para o controle de velocidade de motores de indução trifásicos baseado na metodologia de ajuste de tensão e freqüência (Volts/Hertz) proveniente de um inversor PWM, de modo que o fluxo no entreferro seja mantido constante. O enfoque principal consiste no desenvolvimento do sistema de controle em hardware considerando o estudo dinâmico do controlador frente às variações de conjugado de carga, cujo desempenho da metodologia proposta será avaliado mediante simulações computacionais e ensaios experimentais realizados em laboratório. / The objective of this work consists of the implementation of intelligent system architecture in Digital Signal Processor (DSP) aiming at the real-time three-phase induction motor control. Therefore, a fuzzy logic speed control drive system for three-phase induction motor is proposed, whereas the control methodology is based on voltage and frequency (Volts/Hertz) adjustment of a PWM inverter so that the airgap flux maintains constant. The main focus concerns about hardware development of the control system considering the controller dynamic response study in relation to load torque variations, from which the proposed methodology performance is evaluated by means of computational simulation and experimental results obtained in laboratory.

This work proposes a comparative performance analysis of control and estimation techniques applied to three-phase induction motors with discrete realization, using a fixed-point digital signal processor based platform. Some modifications in original algorithms are proposed to improve the performance of the techniques in study. Initially, an historical review about the induction motors drives and a bibliographical review of the main speed estimation techniques implemented in DSP were accomplished. Then, different models of the induction machine are obtained using the semi-stationary reference frames. From the machine model, two speed controllers are projected: a classical PI controller, that is widely used in industrial environment and a robust model reference adaptive controller, objecting to compensate disturbances and unmodeled dynamics. After that, two estimation techniques based on 1M model are selected to project high-performance speed sensorless drives and later comparison. One of these schemes is extremely spread in academic and industrial environrnents, it is based on a model reference adaptive system (MRAS) and the other one is projected from a modified recursive least squares (MRLS), that is presented as a highperformance altemative solution. In the development of this work are displayed simulation results using the MatlabTM software, real-time simulations in DSP platform, and finally, experimental results. After these results analysis, it is possible to determinate which of these sensorless speed controllers proposed present satisfactory dynamic response for a wide range of speed, including low and null rotations, in situations of load disturbances and parametric variation. / Este trabalho propõe uma análise comparativa do desempenho de técnicas de controle e estimação de velocidade, com realização discreta no tempo, aplicadas a motores de indução trifásicos, utilizando plataforma com base em um processador digital de sinais de ponto-fixo. Algumas modificações em algoritmos existentes na literatura são propostas para melhorar o desempenho das técnicas em estudo. Inicialmente, uma revisão histórica sobre a evolução dos sistemas de acionamento para motores de corrente alternada e uma revisão bibliográfica das principais técnicas de estimação de velocidade implementadas em DSP são realizadas. Em seguida, são obtidos diferentes modelos para o motor de indução trifásico representados em referenciais semi-estacionários. A partir do modelo da máquina foram projetados dois controladores de velocidade: um controlador clássico e amplamente utilizado no meio industrial (PI), e, com o objetivo de compensar distúrbios e dinâmicas não modeladas, um controlador adaptativo robusto por modelo de referência (RMRAC) é implementado. Para o projeto de servomecanismos sensorless de alto desempenho, duas técnicas de estimação de velocidade baseadas no modelo do MI foram selecionadas. Uma delas é amplamente difundida. no meio acadêmico e industrial, sendo fundamentada em um sistema adaptativo por modelo de referência (MRAS) e outra tem base em um algoritmo de mínimos quadrados recursivos modificado (MRLS) e é apresentada como uma alternativa de alto desempenho. No desenvolvimento deste trabalho, resultados de simulações utilizando o software Matlab@, simulações em tempo-real em plataforma DSP, e por fim, resultados experimentais são apresentados. A partir destes resultados, parte-se para avaliação para determinar quais dos controladores sensorless analisados apresentam resposta dinâmica satisfatória em uma larga faixa de velocidade, inclusive em condições de velocidade baixa e nula, e também diante de situações de variação de carga e de parâmetros.

Made available in DSpace on 2016-12-12T20:27:38Z (GMT). No. of bitstreams: 1 Eduardo Henrique Couto.pdf: 1926472 bytes, checksum: 2b4464d74812fd9a1dc1cf69975b8f1f (MD5) Previous issue date: 2013-12-06 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / When the three phase induction motor is vector-controlled driven, is considered the mathematical model as a set of linear equations, so that the control is more effective only over an operation point. However, when changing that point, control can pass to not respond properly, causing unwanted errors of speed, position or even instability. Such behavior are due to mismatch of the real behavior of the motor, which is non-linear and time-varying system, and the mathematical model used in the project. Thus, parametric identification techniques allow the motor parameters to be determined online, tracking its time variation. The focus of the thesis is to present a general background of the subject and show the results obtained using techniques of parametric identification, more specifically exploring the least squares method to fit the parameters of the motor in closed loop. / Quando o motor de indução trifásico é acionado em malha de controle vetorial, é considerado o modelo matemático como um conjunto de equações lineares, por isso o controle é mais efetivo somente sobre este ponto de operação. Entretanto, quando se muda esse ponto, o controle pode passar a não responder mais adequadamente, causando erros indesejáveis de velocidade, posição e até mesmo a instabilidade. Tais fatos ocorrem devido à descasamentos entre o comportamento real do motor, que é não linear e variante no tempo, e o modelo matemático utilizado para o projeto. Dentro de tal contexto, as técnicas de identificação paramétrica permitem que os parâmetros do motor sejam determinados de forma online, monitorando sua variação no tempo. O foco principal deste trabalho é apresentar um cenário geral do assunto e mostrar os resultados obtidos usando as técnicas de identificação paramétrica, mais especificamente explorando o método dos mínimos quadrados para ajustar os parâmetros do motor em malha fechada