There is an increasing interest in steady-state analysis of electric power systems with convertors. Harmonic analysis can be performed in the frequency domain with iterative methods that are comprehensive and efficient but may present convergence problems; this drawback can be overcome by employing appropriate models of convertors. The authors present steady-state mathematical models of line commutated convertors to be included in an iterative harmonic analysis of a power system. To avoid convergence problems and to save the accuracy of the results as well as the computational efficiency, the models are developed including AC and DC frequency dependent impedances and by solving AC and DC side equations as a whole, thus keeping a closed form solution. All nonideal conditions are taken into account.