Traditionally, frequency domain calculations have been restricted to the linear elements of a power system while for the representation of nonlinear components, which are a significant source of harmonics, time domain methods have been used. This paper presents a methodology for the direct harmonic domain representation of static and dynamic nonlinear elements encountered in power systems.The essential contribution of the paper is the description of a general purpose computational package which can be used by developers of programs for power system harmonic analysis. Some of the basic routines of the package, written in Fortran 77, are given. Examples of possible applications are models of transformers, of fluorescent lamps, studies of iron losses, ferroresonance and inrush currents. The dynamic modeling of arcs for electric furnaces is novel and is presented in greater detail.

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a b s t r a c tSerbia has wind with a good capacity factor, the respectable potential of which has not hitherto been utilized. There are a number of proposed wind power projects with an envisaged capacity of up to 2500 MW and the project documentation has been developed for 1300 MW. Within the existing feed-in tariff scheme, only 500 MW are eligible. This limitation is set in a conservative manner bearing in mind moderation (balancing) needs due to the variability of wind power generation. The existing Serbian energy system, with significant hydro generation, available pumped storage hydro capacity, and strong interconnections has many moderators for variable wind generation and for reliable technical performance of the grid. In this study, energy imbalances under different levels of wind penetration into the Serbian energy system were analyzed. Possible new moderation strategies for lowering energy imbalances due to wind integration were evaluated using the EnergyPLAN tool and are presented in this paper.