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Abstract: The efficiency of a finite element mass consistent model for wind field adjustment depends on the stability parameter which allows adjustment from a strictly horizontal wind to a pure vertical one. Each simulation with the wind model leads to the resolution of a linear system of equations, the matrix of which depends on a function , i.e., , where and are constant, symmetric and positive definite matrices with the same sparsity pattern for a given level of discretization. The estimation of this parameter may be carried out by using genetic algorithms. This procedure requires the evaluation of a fitness function for each individual of the population defined in the searching space of , that is, the resolution of one linear system of equations for each value of . Preconditioned Conjugate Gradient algorithm (PCG) is usually applied for the resolution of these types of linear systems due to its good convergence results. In order to solve this set of linear systems, we could either construct a different preconditioner for each of them or use a single preconditioner constructed from the first value of to solve all the systems. In this paper, an intermediate approach is proposed. An incomplete Cholesky factorization of matrix is constructed for the first linear system and it is updated for each at a low computational cost. Numerical experiments related to realistic wind field are presented in order to show the performance of the proposed preconditioning strategy. [ABSTRACT FROM AUTHOR]

Abstract: This paper examines the application of structured singular value (SSV) theory to analyse robust stability of complex power systems with respect to a set of structured uncertainties. Based on SSV theory and the frequency sweep method, techniques for robust analysis of large-scale power systems are developed. The main interest is focused on determining robust stability for varying operating conditions and uncertainties in the structure of the power system. The applicability of the proposed techniques is verified through simulation studies on a large-scale power system. In particular, results for the system are considered for a wide range of uncertainties of operating conditions. Specifically, the developed technique is used to estimate the effect of variations in the parameters of a major system intertie on the nominal stability of a critical inter-area mode. [Copyright &y& Elsevier]