New method of harmonic analysis of power electronic converter and cycloconverter for high-power industrial drives

Large converters and cycloconverters in applications of high-power industrial drives are main harmonic sources in power system. A new method of harmonic analysis for converters and cycloconverters is proposed in this paper. The theoretical fundamentals of this method are that the operation processes of converter and cycloconverter feature the characteristics of discrete sample and modulation, and also are cycling, and that the dynamics of converter and cycloconverter can be represented by several eigen current equations. Recording the sampling data at switching points, computing the harmonics of eigen current equations, and synthesizing those harmonics, the harmonics or side harmonics of the integrated system containing ac and de sides, or ac network side and ac motor side can be obtained. The suggested method has the advantages of less memory capacity needed, fast computation and high accuracy. This method is very useful and effective in estimating the harmonic sources, predicting the harmonic flow and propagation and researching the harmonic suppression and elimination.