An analytical method for predicting current harmonics produced by an ac/dc converter under unbalanced supply voltage

This paper proposes an analytical method for calculating both characteristic and uncharacteristic harmonic currents produced by a six-pulse AC/DC converter under unbalanced supply voltage. The method allows the mathematical relationship between the complex unbalance factor (i. e. ratio of negative-sequence voltage to positive-sequence voltage) and the resulting harmonic currents (magnitudes and phases) to be found. An approximate harmonic model derived from the analysis is also proposed. Comparisons between the basic analytical model, the approximate model and the digital simulation results are given to validate the analysis.