<p>Before a new flight control system is released for flight, a huge number of simulations are evaluated to find weaknesses of the system. This process is called flight clearance. Flight clearance is a very important but time consuming process. There is a need of better flight clearance methods and one of the most promising methods is the use of optimization. In this thesis the flight clearance of a simulation model of JAS 39 Gripen is examined. Two flight clearance algorithms using two different optimization methods are evaluated and compared to each other and to a traditional flight clearance method.</p><p>In this thesis the flight clearance process is separated into three cases: search for the worst flight condition, search for the worst manoeuvre and search for the worst flight condition including parameter uncertainties. For all cases the optimization algorithms find a more dangerous case than the traditional method. In the search for worst flight condition, both with and without uncertainties, the optimization algorithms are to prefer to the traditional method with respect to the clearance results and the number of objective function calls. The search for the worst manoeuvre is a much more complex problem. Even as the algorithms find more dangerous manoeuvres than the traditional method, it is not certain that they find the worst manoeuvres. If not other methods should be used the problem has to be rephrased. For example other optimization variables or a few linearizations of the optimization problem could reduce the complexity.</p><p>The overall impression is that the need of information and problem characteristics define which method that is most suitable to use. The information required must be weighed against the cost of objective function calls. Compared to the traditional method, the optimization methods used in this thesis give extended information about the problems examined and are better to locate the worst case.</p>

Before a new flight control system is released for flight, a huge number of simulations are evaluated to find weaknesses of the system. This process is called flight clearance. Flight clearance is a very important but time consuming process. There is a need of better flight clearance methods and one of the most promising methods is the use of optimization. In this thesis the flight clearance of a simulation model of JAS 39 Gripen is examined. Two flight clearance algorithms using two different optimization methods are evaluated and compared to each other and to a traditional flight clearance method. In this thesis the flight clearance process is separated into three cases: search for the worst flight condition, search for the worst manoeuvre and search for the worst flight condition including parameter uncertainties. For all cases the optimization algorithms find a more dangerous case than the traditional method. In the search for worst flight condition, both with and without uncertainties, the optimization algorithms are to prefer to the traditional method with respect to the clearance results and the number of objective function calls. The search for the worst manoeuvre is a much more complex problem. Even as the algorithms find more dangerous manoeuvres than the traditional method, it is not certain that they find the worst manoeuvres. If not other methods should be used the problem has to be rephrased. For example other optimization variables or a few linearizations of the optimization problem could reduce the complexity. The overall impression is that the need of information and problem characteristics define which method that is most suitable to use. The information required must be weighed against the cost of objective function calls. Compared to the traditional method, the optimization methods used in this thesis give extended information about the problems examined and are better to locate the worst case.

L'intégration des liaisons à courant continu dans les systèmes électriques permet d’accroitre les possibilités de pilotage des réseaux, ce qui permet d’en améliorer la sûreté et de raccorder de nouveaux moyens de production. Pour cela la technologie VSC-HVDC est de plus en plus plébiscitée pour interconnecter des réseaux non synchrones, raccorder des parcs éoliens offshore, ou contrôler le flux d’énergie notamment sur des longues distances au travers de liaisons sous-marines (liaison NorNed). Les travaux de cette thèse portent sur la modélisation, la commande non-linéaire et la stabilisation des systèmes VSC–HVDC, avec deux axes de travail. Le premier se focalise sur la conception et la synthèse des lois de commandes non-linéaires avancées basées sur des systèmes de structures variables (VSS). Ainsi, les commandes par modes glissants (SMC) et le suivi asymptotique de trajectoire des sorties (AOT) ont été proposées afin d’assurer un degré désiré de stabilité en utilisant des fonctions de Lyapunov convenables. Ensuite, la robustesse de ces commandes face à des perturbations et/ou incertitudes paramétriques a été étudiée. Le compromis nécessaire entre la robustesse et le comportement dynamique requis dépend du choix approprié des gains. Ces approches robustes, qui sont facile à mettre en œuvre, ont été appliquées avec succès afin d’atteindre des performances dynamiques élevées et un niveau raisonnable de stabilité vis-à-vis des diverses conditions anormales de fonctionnement, pour des longueurs différentes de liaison DC. Le deuxième vise à étudier l’influence de la commande du convertisseur VSC-HVDC sur l'amélioration de la performance dynamique du réseau de courant alternatif en cas d’oscillations. Après une modélisation analytique d’un système de référence constitué d’un groupe connecté à un convertisseur VSC-HVDC via un transformateur et une ligne, un contrôleur conventionnel simple PI est appliqué au niveau du convertisseur du système pour agir sur les oscillations rotoriques de la machine synchrone. Cette commande classique garantie une amélioration acceptable des performances dynamiques du système; surtout pour l'amortissement des oscillations de l'angle de puissance de la machine synchrone lors de défauts. / The integration of nonlinear VSC-HVDC transmission systems in power grids becomes very important for environmental, technical, and economic reasons. These systems have enabled the interconnection of asynchronous networks, the connection of offshore wind farms, and the control of power flow especially for long distances. This thesis aims the non-linear control and stabilization of VSC-HVDC systems, with two main themes. The first theme focuses on the design and synthesis of nonlinear control laws based on Variable Structure Systems (VSS) for VSC-HVDC systems. Thus, the Sliding Mode Control (SMC) and the Asymptotic Output Tracking (AOT) have been proposed to provide an adequate degree of stability via suitable Lyapunov functions. Then, the robustness of these commands has been studied in presence of parameter uncertainties and/or disturbances. The compromise between controller’s robustness and the system’s dynamic behavior depends on the gain settings. These control approaches, which are robust and can be easily implemented, have been applied to enhance the system dynamic performance and stability level in presence of different abnormal conditions for different DC link lengths. The second theme concerns the influence of VSC-HVDC control on improving the AC network dynamic performance during transients. After modeling the Single Machine via VSC-HVDC system in which the detailed synchronous generator model is considered, the conventional PI controller is applied to the converter side to act on damping the synchronous machine power angle oscillations. This simple control guarantees the reinforcement of the system dynamic performance and the power angle oscillations damping of the synchronous machine in presence of faults.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work proposes two vector control schemes for permanent magnet synchronous motors. They are destined to speed and position control, respectively, and are based on a control law called VS-RMRAC. Not being yet applied to the electric machines control, the VS-RMRAC control law presents robustness features that are potentially advantageous from the point of view of the closed loop PMSM dynamics. It also presents well established design and robust stability conditions, which makes its digital implementation easier. Both control structures are described and its respective design methods are presented. From simulation results, the behavior and performance of both structures are analyzed in face of load disturbances and parameter uncertainties. The speed control scheme and its simulation results are validated experimentally. This scheme is digitally implemented with fixed-point arithmetic using a TMS320F2812 DSP. Both schemes with its potentialities and limitations are then discussed. / Este trabalho propõe duas estratégias de controle vetorial para motores síncronos a ímãs permanentes (MSIP s). Destinam-se ao controle de velocidade e de posição, respectivamente, e são baseados em uma lei de controle chamada VS-RMRAC. Não tendo sido aplicado ainda ao controle de máquinas elétricas, a lei de controle VS-RMRAC apresenta características de robustez que são potencialmente vantajosas do ponto de vista da dinâmica em malha fechada de MSIP s. Também apresenta condições de projeto e estabilidade robusta bem estabelecidas para o tempo discreto, o que facilita sua implementação digital. Ambas as estruturas de controle são descritas e suas respectivas metodologias de projeto são apresentadas. A partir de resultados de simulação, o comportamento e desempenho de ambas são analisados frente a perturbações de carga e incertezas paramétricas. O esquema de controle de velocidade e seus resultados de simulação são validados experimentalmente. Este esquema é implementado digitalmente com aritmética de ponto fixo utilizando DSP TMS320F2812. As potencialidades e limitações de ambos os esquemas são, por fim, discutidos.