Simplified predetermination of line current harmonics

In predetermining line current harmonics of controlled AC/DC converters, the effects of commutation and DC ripple must be taken into account frequently, as for example in the case of medium-size DC drive applications. Based on a suitable normalization, the dominant parameters determining the current harmonics are the line and DC side reactances, respectively, and the DC voltage. This forms the basis for a systematic comparison of the accuracy of analytical formulas, describing the commutation or the DC ripple effect only. By the aid of these results, the validity ranges of different approximation formulas can be estimated and the most important question answered concerning the proof of the conventional assumption of a “sufficiently” smoothed DC current. In order to predetermine line current harmonics as easily as possible, the most effective formula can be obtained out of corresponding decision areas. Thereby, the allowable error is restricted to 2% of the fundamental, confirmed by comparing results of digital simulation studies