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The generation of wind energy deliberately becomes a significant part of generated electrical power in developed nations. Factors like fluctuation in natural wind speed and the use of power electronics present issues related power quality in wind turbine application. Following to the fact that there have been remarkable increase of wind energy in the electrical energy production worldwide, the effect on power quality and power system stability caused by wind power is considered significant, and hence the evaluation of this effect is crucial and obligatory. In order to examine and evaluate the characteristics of power quality of grid-integration of wind power in a persistent and authentic manner, several guidelines were introduced and established. One of the widely used guideline to define power quality of wind turbine is IEC standard 61400-21. Moreover, power system operator demands wind turbines to tolerate a certain voltage dip in some countries. The wind turbines concepts such as doubly-fed induction generator wind turbine and the direct driven wind turbine wind turbine with a permanent magnet synchronous generator are considered as the most promising concepts among other wind turbine types since they can operate in wide range of wind speed. The major goal of this PhD work is to examine the power quality character aspects of these wind turbine concepts. The power quality problems were calculated according to that devised by IEC- 61400-21 and then compared afterwards. The research includes the evaluation of the following power quality characteristics: voltage dip response, current harmonics distortion, control of active and reactive power and voltage flicker. Besides the IEC-standard 61400-21, the study also looks into the short-circuit current and fault-ride through with specifications provided by some grid codes, as power system stability is greatly influenced by these aspects. In order to achieve the research's goal, a reliable dynamic model of wind turbine system and control are required. Thus a complete model for both wind turbines systems was developed in PSCAD/EMTDC simulation-program which is the fanatical power system analysis tool, which can achieve a complete simulation of the system dynamic behaviour from the wind turbine. Two controllers are adopted for wind turbine system, converter control and pitch angle control. The converter controlled by a vector control in order to regulate the active and the reactive power whereas the pitch control scheme is put to function to limit the aerodynamic power in high wind speed. The ability of providing adequate state steady and dynamic performances are what wind turbine assures, as examined by simulation results, and via this, problems related to power quality caused by integrating wind turbines to the grid can be studied by wind turbine model.

Modular multilevel converter type voltage source converter (MMC-VSC) is a potential candidate for present and future HVdc projects. The d-q decoupled control system is widely used to control MMC-VSC systems. Selection of PI-controller parameters for MMC-VSC systems is a challenging task as control loops are not completely decoupled. Since there is no widely accepted method to tune these control loops, the industry practice is to use the trial and error approach that requires a great amount of time. Therefore, it is required to develop a systematic procedure to tune PI-controllers considering necessary system dynamics and also to propose guidelines for control system design. This thesis introduces a systematic procedure to determine PI-controller parameters for the d-q decoupled control system. A linearized state-space model of an MMC-VSC system is developed to calculate the frequency-domain attributes. The control tuning problem is formulated as an optimization problem which is general and any meta-heuristic method can be used to solve the problem. In this thesis, the simulated annealing is applied to solve the problem. The efficacy of the tuned parameters is tested on the electromagnetic transient model of the test system on the real-time digital simulators (RTDS). In addition, it is shown that the proposed method is suitable to tune PI-controller parameters for MMC-VSC systems connected to strong as well as weak ac networks. Further, this thesis investigates the effects of d-q decoupled controller parameters, phase-locked loop (PLL) gains, and measuring delays on the stability and performance of the MMC-VSC test system. It is shown that the converter controllers have greater influence on the system stability and the impact of PLL gains is negligible unless very high PLL gains are used. In addition, the negative impact of measuring delays in instantaneous currents and voltages is also analysed by performing eigenvalue and sensitivity analysis. Finally, a set of guidelines for control design of MMC-VSC systems is summarized. In general, the proposed control tuning procedure would be useful for the industry to tune PI-controllers of MMC-VSC systems. Furthermore, the proposed methodology is generic and can be adapted to tune of any dynamic device in power systems. / February 2017

Estuda-se o problema de sintonia de controladores, objetivando-se a formulação do problema de sintonia ótima de controladores. Busca-se uma formulação que seja geral, ou seja, válida para qualquer estrutura de controlador e qualquer conjunto de especificações. São abordados dois temas principais: especificação de controladores e sintonia ótima de controladores. São compiladas as principais formas de especificação e avaliação de controladores e é feita a formulação do problema de sintonia de controladores como um problema padrão de otimização. A abordagem proposta e os conceitos apresentados são então aplicados em um conjunto de exemplos. / The problem of control tuning is studied, aiming the formulation of the optimal control tuning problem. A general formulation, valid for any controller structure and any set of specifications, is sought. Two main themes are addressed: controller specification and optimal controller tuning. The main ways of controller specification and assessment are compiled and the optimal controller tuning problem is formulated as a standard optimization problem. The proposed approach and the presented concepts are then applied in a set of examples.

Maintaining the pH of a fluid or a solution at a specific value is a concern in many industrial processes, wastewater management, and food and pharmaceutical production. Given the importance of controlling pH in many processes, the objective of this thesis is to study and compare the effectiveness of some controller algorithms to control the pH of a process. In this study, the performance of three controller algorithms, namely PID, fractional PID and LA controllers, is evaluated for the control of a simple neutralization process using conventional controller performance metrics. Performance metrics used are the response time, the Integral of the Time weighted Absolute Error (ITAE), the Integral of the Squared Error (ISE), and the Integral of the Squares of the changes (ΔU) in the manipulated variable (ISDU). The three controllers were therefore tuned to minimize one or a combination of the controller performance metrics. Results show that PID, fractional PID and LA controllers implemented and tested in this research are all worthy controllers for maintaining pH of the neutralization process. Simulation results show that the three controllers can be used with confidence to cope with the high nonlinearity of a pH neutralization process provided that the process is properly designed. The relative small gain in performance obtained with the fractional PID controller, compared to a linear PID controller, suggests that it is not worth resorting to a fractional PID controller given its complexity and higher computation effort. Results show that PID and LA controllers are easy to implement with short response time and low ITAE and ISDU performance metrics.

Estuda-se o problema de sintonia de controladores, objetivando-se a formulação do problema de sintonia ótima de controladores. Busca-se uma formulação que seja geral, ou seja, válida para qualquer estrutura de controlador e qualquer conjunto de especificações. São abordados dois temas principais: especificação de controladores e sintonia ótima de controladores. São compiladas as principais formas de especificação e avaliação de controladores e é feita a formulação do problema de sintonia de controladores como um problema padrão de otimização. A abordagem proposta e os conceitos apresentados são então aplicados em um conjunto de exemplos. / The problem of control tuning is studied, aiming the formulation of the optimal control tuning problem. A general formulation, valid for any controller structure and any set of specifications, is sought. Two main themes are addressed: controller specification and optimal controller tuning. The main ways of controller specification and assessment are compiled and the optimal controller tuning problem is formulated as a standard optimization problem. The proposed approach and the presented concepts are then applied in a set of examples.

This thesis attempts to tune any controller without the mathematical model knowledge of the system it is controlling. For that purpose, the optimization algorithm of MATLAB&reg / 6.5 / Nonlinear Control Design Blockset (NCD) is adapted for real-time executions and combined with a hardware-in-the-loop simulation provided by MATLAB&reg / 6.5 / Real-Time Windows Target (RTWT). A noise-included model of a DC motor position control system is obtained in MATLAB&reg / / SIMULINK first and simulated to test the modified algorithm in some aspects. Then the presented methodology is verified using the physical plant (DC motor position control system) where tuning algorithm is driven mainly by the real system data and the required performance parameters specified by a user defined constraint window are successfully satisfied. Resultant improvements on the step response behavior of DC motor position control system are shown for two case studies.

This work focuses on modeling and real-time control of a motion simulator for dynamic testing of a two-axis gyro-stabilized head mirror used in modern tanks. For this purpose, a six-degree-of freedom Stewart Platform which can simulate disturbances on the stabilized head mirror during operation of the tank is employed. Mathematical models of the Stewart Platform are constructed using MATLAB and ADAMS. Control system infrastructure is constructed and real-time control system elements are employed. Controller tuning is achieved by using the developed mathematical models in MATLAB. These parameters are applied in the real-time control system and fine tuning is achieved. Accuracy of the motion simulator is tested by mounting an Inertial Measurement Unit on the Stewart Platform. Further control system strategies are discussed by means of simulation.

This work focuses on modeling, parameter estimation, and real-time position control of a two axis Gimbaled Mirror System (GMS) which is designed and manufactured to move an IR spot generated by an Infra Red Scene Generator System (IRSGS) in two orthogonal axes (elevation and azimuth) within the IR scene which is also generated by the IRSGS. Mathematical models of the GMS, the control system, and the disturbance torque originated from the movements of Flight Motion Simulator (FMS), on which the IRSGS will be mounted, are constructed using MATLAB&reg / /Simulink&reg / and MATLAB/Simulink/SimMechanics&reg / . Parameter estimations of the GMS and control system elements are achieved using MATLAB/Simulink Parameter Estimation Tool&reg / . The controller tuning is performed using the developed mathematical models in MATLAB/Simulink environment. Optimized digital PID controllers are implemented in the real-time control system. Performances of the controllers for both GMS axes are evaluated by both real system tests and simulation runs / and the results of these runs are compared. Controller performances under the effect of disturbances are analyzed by using the mathematical models developed in the MATLAB/ Simulink environment.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2017-12-18T11:49:36Z No. of bitstreams: 2 Dissertação - Douglas Freire de Carvalho - 2017.pdf: 23722781 bytes, checksum: 3e99befa0116cb9ca768d092c541c055 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-12-18T11:50:09Z (GMT) No. of bitstreams: 2 Dissertação - Douglas Freire de Carvalho - 2017.pdf: 23722781 bytes, checksum: 3e99befa0116cb9ca768d092c541c055 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-12-18T11:50:09Z (GMT). No. of bitstreams: 2 Dissertação - Douglas Freire de Carvalho - 2017.pdf: 23722781 bytes, checksum: 3e99befa0116cb9ca768d092c541c055 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-11-20 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / This work presents study of nonlinear predictive controller, tuned by optimization process, applied to independent excitation DC motor speed control, controlled by fully controlled three phase rectifier. The methodology starts from the construction of the workbench that represents the real system followed by the development and validation of the computational model. The optimization process promotes the obtaining of optimized parameters for the nonlinear model based predictive controller to be implemented in the real process. Comparisons are made between the control technique proposed with classical control techniques, in computational and real environment. The results indicate the prominence of the proposed technique to be used in control of non-linear systems where seeks smaller errors even with disturbance insertions. / Este trabalho apresenta estudo de controlador preditivo não linear, sintonizado por processo de otimização, aplicado ao controle de velocidade de motor de corrente contínua de excitação independente acionado por retificador trifásico totalmente controlado. A metodologia parte da construção da bancada que representa o sistema real seguida pelo desenvolvimento e validação de modelo computacional. O processo de otimização, promove a obtenção de parâmetros otimizados para o controlador preditivo não linear baseado em modelos a serem implementados no processo real. São realizadas comparações entre a técnica de controle proposta com técnicas de controle clássicas, em ambiente computacional e real. Os resultados indicam a proeminência da técnica proposta a ser empregada em controle de sistemas não lineares onde busca-se menores erros mesmo com inserção de distúrbios.