Este trabalho apresenta um estudo de controladores repetitivos e ressonantes-repetitivos aplicados a fontes ininterruptas de energia (UPSs, do termo em inglês, Uninterruptible Power Supplies). Primeiramente, o desempenho dos controladores repetitivos é analisado a partir das exigências e dos procedimentos de testes definidos pela norma IEC 62040-3. A partir destes resultados, são discutidas as principais causas para o erro de seguimento de um sinal de referência e é avaliado o impacto de metodologias de correção aplicadas na função de transferência do controlador repetitivo. No contexto dos controladores ressonantes-repetitivos duas topologias são analisadas: a primeira é composta por um controlador ressonante sintonizado na frequência fundamental do sinal a ser seguido em paralelo com um controlador repetitivo sintonizado na mesma frequência; a segunda topologia é composta pelo mesmo paralelo entre os controladores ressonante e repetitivo, mas um filtro complementar é adicionado em série com o controlador repetitivo visando alocar a operação de cada controlador em faixas de frequências distintas. Então uma variação do controlador ressonante-repetitivo com filtro é proposta, na qual o filtro é utilizado para corrigir a fase do laço do controlador repetitivo e consequentemente aumentar a magnitude nas frequências de interesse. A partir desta estrutura proposta, uma representação no espaço de estados do sistema em malha fechada é obtida e o projeto do controlador é realizado através da solução de um problema de otimização com restrições na forma de Desigualdades Matriciais Lineares (do inglês, Linear Matrix Inequalities - LMIs). Resultados de simulação utilizando Matlab/PSIM são apresentados para demostrar a melhoria de desempenho do sistema com o controlador proposto. / This work presents a study of repetitive and resonant-repetitive controllers applied to Uninterruptible Power Supplies (UPSs). First, the performance of repetitive controllers is analyzed in terms of requirements and test procedures defined in the IEC 62040-3 standard. From these results the main causes of the reference tracking error are discussed and the impact of correction methodologies applied to repetitive controller transfer function is evaluated. In the context of the resonant-repetitive controllers two topologies are analyzed: the first is composed of a resonant controller tuned to the fundamental frequency of the signal to be followed in parallel with a repetitive controller tuned to the same frequency; the second topology is composed of the same parallel connection between the resonant and the repetitive controllers but a complementary filter is added in series with the repetitive controller aiming to restrict each controller action to different frequency bands. Then a variation of the resonant-repetitive controller with a filter is proposed, in which the filter is used to correct the phase of the repetitive controller loop and consequently increase the magnitude at the frequencies of interest. From this proposed structure, a state space model representing the closed loop system is obtained and the controller design is carried out by the solution of an optimization problem based on LMI (Linear Matrix Inequality) constraints. Simulation results in Matlab/PSIM are presented to demonstrate the improvement on system performance with the proposed controller.

Este trabalho apresenta um estudo de controladores repetitivos e ressonantes-repetitivos aplicados a fontes ininterruptas de energia (UPSs, do termo em inglês, Uninterruptible Power Supplies). Primeiramente, o desempenho dos controladores repetitivos é analisado a partir das exigências e dos procedimentos de testes definidos pela norma IEC 62040-3. A partir destes resultados, são discutidas as principais causas para o erro de seguimento de um sinal de referência e é avaliado o impacto de metodologias de correção aplicadas na função de transferência do controlador repetitivo. No contexto dos controladores ressonantes-repetitivos duas topologias são analisadas: a primeira é composta por um controlador ressonante sintonizado na frequência fundamental do sinal a ser seguido em paralelo com um controlador repetitivo sintonizado na mesma frequência; a segunda topologia é composta pelo mesmo paralelo entre os controladores ressonante e repetitivo, mas um filtro complementar é adicionado em série com o controlador repetitivo visando alocar a operação de cada controlador em faixas de frequências distintas. Então uma variação do controlador ressonante-repetitivo com filtro é proposta, na qual o filtro é utilizado para corrigir a fase do laço do controlador repetitivo e consequentemente aumentar a magnitude nas frequências de interesse. A partir desta estrutura proposta, uma representação no espaço de estados do sistema em malha fechada é obtida e o projeto do controlador é realizado através da solução de um problema de otimização com restrições na forma de Desigualdades Matriciais Lineares (do inglês, Linear Matrix Inequalities - LMIs). Resultados de simulação utilizando Matlab/PSIM são apresentados para demostrar a melhoria de desempenho do sistema com o controlador proposto. / This work presents a study of repetitive and resonant-repetitive controllers applied to Uninterruptible Power Supplies (UPSs). First, the performance of repetitive controllers is analyzed in terms of requirements and test procedures defined in the IEC 62040-3 standard. From these results the main causes of the reference tracking error are discussed and the impact of correction methodologies applied to repetitive controller transfer function is evaluated. In the context of the resonant-repetitive controllers two topologies are analyzed: the first is composed of a resonant controller tuned to the fundamental frequency of the signal to be followed in parallel with a repetitive controller tuned to the same frequency; the second topology is composed of the same parallel connection between the resonant and the repetitive controllers but a complementary filter is added in series with the repetitive controller aiming to restrict each controller action to different frequency bands. Then a variation of the resonant-repetitive controller with a filter is proposed, in which the filter is used to correct the phase of the repetitive controller loop and consequently increase the magnitude at the frequencies of interest. From this proposed structure, a state space model representing the closed loop system is obtained and the controller design is carried out by the solution of an optimization problem based on LMI (Linear Matrix Inequality) constraints. Simulation results in Matlab/PSIM are presented to demonstrate the improvement on system performance with the proposed controller.

The main aim of this research project is to extend theories of four-wheel-steering as developed by J. Ackermann to include an individually steered four-wheel steering system for passenger vehicles. Ackermann’s theories, including theories available in this subject area, dwell much on vehicle system dynamics developed from what is called single track model and some call it a bicycle model. In the bicycle model, the front two wheels are bundled together. Similarly, the rear wheels are bundled together. The problem with this is that it assumes two front wheels or two rear wheels to be under the same road, vehicle and operating conditions. The reality on the ground and experiments that are conducted are to the contrary. Therefore this study discusses vehicle disturbance rejection through robust decoupling of yaw and lateral motions of the passenger vehicle. A mathematical model was developed and simulated using Matlab R2008b. The model was developed in such a way that conditions can be easily changed and simulated. The model responded well to variations in road and vehicle conditions. Focus was in the ability of the vehicle to reject external disturbances. To generate yaw moment during braking, the brake on the left front wheel was disconnected. This was done because lateral wind generators, as used by Ackermann, were not available. The results from both simulations and experiments show disturbance rejection in the steady state. Copyright / Dissertation (MSc)--University of Pretoria, 2010. / Mechanical and Aeronautical Engineering / unrestricted

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A method to adapt the Generalized Predictive Control parameters to improve broadband disturbance rejection was developed and tested. The effect of the parameters on disturbance rejection has previously been poorly understood and a trial and error method was used to achieve adequate results. This dissertation provides insight on the effect of the parameters, as well as an adaptive tuning method to adjust them. The study begins by showing the effect of the four GPC parameters, the control and prediction horizons, control weighting &lambda , and order, on the disturbance rejection and control effort of a vibrating plate. It is shown that the effect of increases in the control and prediction horizon becomes negligible after a certain point. This occurs at nearly the same point for a variety of &lambda 's and orders, and hence they can be eliminated from the tuning space. The control effort and closed-loop disturbance rejection are shown to be highly dependant on &lambda and order, thereby becoming the parameters that need to be tuned. The behavior is categorized into various groups and further investigated. The pole and zero locations of the closed-loop system are examined to reveal how GPC gains control and how it can fail for non-minimum phase plants. A set of fuzzy logic modules is developed to adapt &lambda with order fixed, and conversely to adapt order with &lambda fixed. The effectiveness of the method is demonstrated in both numerical simulations and laboratory experiments. / Ph. D.

Este trabalho apresenta um estudo da discretização de controladores ressonantes aplicados a fontes ininterruptas de energia (UPSs, do termo em inglês, Uninterruptible Power Suppllies). Primeiramente, diferentes métodos de discretização serão considerados na obtenção de um modelo em tempo discreto da UPS. Além disso, estes métodos serão comparados do ponto de vista frequencial para a definição da formulação do controlador ressonante a ser utilizado. Então, uma metodologia de projeto robusto do controlador ressonante em tempo discreto é proposta a partir de uma representação em espaço de estados do sistema em malha fechada e os parâmetros do controlador são obtidos através da solução de um problema de otimização convexa sujeito a restrições na forma de Desigualdades Matriciais Lineares (do inglês, Linear Matrix Inequalities - LMIs). A estratégia proposta foi validada por meio de resultados de simulação e experimentais obtidos com um inversor comercial de 3,5 kVA considerando os critérios estabelecidos na norma IEC 62040-3. Nestas condições, demonstrara-se um desempenho melhor do que os obtidos com a discretização do controlador projetado em tempo contínuo, sobretudo quando consideradas frequências de amostragem menores. / This work presents a study about discrete-time resonant controllers applied to uninterruptible power supplies (UPSs). First, different discretization methods are considered to obtain an equivalent UPS discrete-time model. Moreover, these methods are compared in the frequency domain in order to define the resonant controller structure to be employed. Then, a robust design methodology to the discrete-time resonant controller is proposed using a state-space representation of the closed-loop system and the controller parameters are obtained by solving a convex optimization problem subject to constraints in the form of Linear Matrix Inequalities (LMIs). The proposed strategy was validated by means of simulation and experimental results obtained with a 3.5 kVA commercial inverter taking into account the IEC 62040-3 norm requirements. In this conditions, a better performance was achieved than those obtained through discretization of a continuous-time controller, especially when considering smaller sampling frequencies.

Submitted by Sandro Camargo (sandro.camargo@unipampa.edu.br) on 2015-05-09T20:45:31Z No. of bitstreams: 1 117110026.pdf: 2752105 bytes, checksum: bd6b8c2341ad7ebc5b553fad3338b56f (MD5) / Made available in DSpace on 2015-05-09T20:45:31Z (GMT). No. of bitstreams: 1 117110026.pdf: 2752105 bytes, checksum: bd6b8c2341ad7ebc5b553fad3338b56f (MD5) Previous issue date: 2014-12-01 / O controle de conversores eletrônicos de potência tem recebido muita atenção devido às suas inúmeras aplicações. Destacam-se especialmente aplicações em problemas de qualidade de energia, onde é necessário injetar uma corrente na rede elétrica de acordo com uma referência. A conexão de conversores na rede elétrica, no entanto, apresenta diversos desafios, como a existência de incerteza paramétrica na planta e distúrbios advindos da rede. Além disso, inerentemente ao seu funcionamento, conversores eletrônicos de potência geram componentes harmônicas de comutação que precisam ser filtradas. A tendência atual das estratégias de controle é o relaxamento da exigência clássica de conhecimento completo da planta a ser controlada, buscando robustez com relação às incertezas paramétricas. Este trabalho apresenta uma estratégia de controle capaz de rejeitar distúrbios e apresentar bom desempenho frente a incertezas, utilizando técnicas de controle multimalhas e controle adaptativo. Por fim, são apresentados resultados de simulação, e resultados experimentais que mostram o bom funcionamento do sistema. / Voltage-source converter control is being very exploited due to its numerous applications. Special attention is given to energy quality applications, which demand the injection of currents in the grid according to a reference current. The connection of converters to the grid, however, presents several challenges such as parametric uncertainty associated to the plant and disturbances coming from the grid. Furthermore, inverters generate switching harmonics that need to be filtered. The tendency in control strategies is the relaxation of the classical requirement of complete knowledge of the plant, seeking robustness with respect to parametric uncertainties. This work presents a control strategy capable of disturbance rejection and good performance in relation to uncertainties, using Multi-Loop and Adaptive control techniques. Simulation results are presented, and experimental results show the good behavior of the proposed system.

L'intégration des sources d'énergies renouvelables sur le réseau électrique est complexe en raison de leur nature intermittente et décentralisée. Le micro-réseau est une approche prometteuse pour interconnecter des générateurs distribués (DGs) locaux, alimenter des charges locales et également échanger de l'énergie avec le réseau électrique de manière contrôlée. Ce mode de production/consommation locales permet d'éviter la transmission d'électricité sur de longues distances, et implique donc une plus grande efficacité. Ces travaux se concentrent sur l'analyse et le contrôle du micro-réseau continu afin que les DGs se répartissent l'alimentation des charges et qu'ils maintiennent également la tension du bus continu. À l'équilibre, les contraintesde la commande du statisme classique (droop control) pour un système comportant de multiples DGs sont analysés, et une méthode de compensation mixte est proposée pour améliorer simultanément le maintien en tension et le partage du courant de charge. En dynamique, le modèle global du système est construit en introduisant une inductance virtuelle dans le circuit équivalent du DG, puis plusieurs modèles d'ordre réduit sont examinés pour vérifier leur efficacité dans l'analyse de la stabilité du système. Un modèle multi-échelle d'ordre réduit (RMM) est proposé afin de conserver les contraintes temporelles ainsi que de réduire la complexité du système. Enfin, une méthode basée sur le contrôle de rejet de perturbation active (ADRC) est présentée afin de mettre en oeuvre le contrôle local de la tension des DG en prenant en compte l'échelle de temps. Cette méthode permet d'améliorer la dynamique du système de contrôle en ajustant la largeur de bande passante de la commande et de l'observateur. Les analyses et les méthodes de contrôle proposées sont vérifiées par des essais expérimentaux dans notre plateforme au laboratoire. / The direct integration of renewable energy resources to the utility grid is pretty tough due to their intermittent feature and dispersed nature. Microgrid is one promising approach to gather the local distributed generators (DGs), supply local loads as well as exchange power with the utility grid as a controllable unit. This local-generation-localconsumption mode is able to avoid the long distance power transmission, thus can benefit a higher efficiency. The control aim of DC microgrids is to make the multiple DGs share the load properly as well as maintain the DCbus voltage stable. In steady state, the constrains of the classic droop control in multiple DGs environment are analyzed, and a mixed compensation method using common current is proposed to improve the voltage and load sharing performance simultaneously. In dynamic state, the system comprehensive model is constructed by the introduction of virtual inductor in the equivalent circuit of the DG, then several reduced-order models are examined to check their effectiveness for the system stability analysis. A reduced-order multi-scale model (RMM) is proposedto keep major time scale information as well as reduce the system complexity. Finally, an active disturbance rejection control (ADRC) based control method is proposed to realize the time scale droop control. It can effectively adjust the dynamic of the local control by adjusting the bandwidth of the Linear Extend State Observer or/and the controller. The proposed analysis and control methods are verified by experimental tests in our laboratory platform.