Effects of modeling on the accuracy of harmonic analysis

Electronic switching in AC/DC converters generate harmonics. The level of the harmonics depends on the interaction of the interconnected AC and DC systems. In analysis methods for computing harmonic levels, the modeling of the AC power system and its effect on the computed harmonic spectrum, and the convergence of the solution method have not been adequately researched. A method which addresses these issues is proposed. The method is used to show that the choice of the AC system model is very critical since the harmonic distortion at the interface bus is the result of an interaction between the converter and the AC-system. The method consists of a comprehensive model of a converter substation, the AC power system, and the DC-system equivalent. A solution algorithm based on Newton´s method is proposed with improved convergence characteristics. A parametric study is presented to illustrate the effects of the AC power system model and the converter control system on the harmonic generation