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    A comparison of LMI and GA based robust controller designs for VSC HVDC
    (IEEE, 2006)
    Durrant, Martyn
    ;
    Werner, Herbert
    ;
    Abbott, Keith
    A controller is required for a VSC HVDC (Voltage Source Converter High Voltage Direct Current) terminal that provides good performance across a range of operating conditions. A nominal mixed sensitivity H∞ design is first presented. An LMI based robust H∞ design and two genetic algorithm based direct search methods methods are then applied to optimize the same H∞ norm across an operating range to provide robust performance. It is demonstrated that in this application the controllers designed by direct search using GA give better robust performance than the LMI based method. The principal reason for this is that unlike LMI based methods they do not guarantee quadratic stability across the operating range, even though stability across the operating range is demonstrated.
    Publicationtype: Conference Paper
      23
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    Automated generation and assessment of affine LPV models
    (IEEE, 2006)
    Kwiatkowski, Andreas
    ;
    Boll, Marie-Theres
    ;
    Werner, Herbert
    LPV representations of given nonlinear or parameter dependent plants are usually not unique, and different models lead to different achievable performance when LMI techniques are used to design LPV controllers. To facilitate the construction of suitable LPV plant models, a method for automated generation of affine LPV representations has been developed and is presented in this paper. Moreover, a heuristic measure for the "quality" of different LPV models is discussed. The proposed method has been implemented in Matlab and is illustrated with a practical application: construction of an affine LPV model for the problem of charge control of a car engine.
    Publicationtype: Conference Paper
      102
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    Synthesis of low-order controllers for LPV systems using LMIs and evolutionary search
    (IEEE, 2006)
    Chughtai, Saulat S.
    ;
    Werner, Herbert
    A procedure for designing robust and gain-scheduled controllers for linear parameter-varying (LPV) systems is proposed that exploits known bounds on the rate of parameter variation to reduce conservatism. Recent results on stability analysis of LPV systems with known bounds on the rate of parameter change, using the concept of quadratic separators have been extended to compute a measure of worst-case performance of an LPV system by solving an LMI problem. The problem of synthesizing robust and gain-scheduled controllers leads to a bilinear matrix inequality, and a hybrid approach to solving this problem based on LMI solvers and genetic algorithms is proposed in this paper. Two design examples illustrate the efficiency of the proposed method.
    Publicationtype: Conference Paper
      35