Space-phasor model of 3-phase AC systems with current-source power converters. Part I: theoretical background

Abstract

The presented method for the calculation of 3-phase AC systems with DC link indirect converters is based on the perception that the stationary operation of converter systems can be treated as a periodic sequence of similarly transient processes. It combines the advantages of space phasor and Laplace transformations and leads to simple equivalent circuits using the standard theories for quadripole networks. Therefore, all network functions can be determined analytically. The developed method is presented on the example of a 6-pulse current link indirect converter. Based on the analytic calculation of the current in the DC link all other network variables can be determined analytically. Furthermore, the calculation rules for the harmonics are specified so that the interactions of the converter and the surrounding network can be characterized and evaluated exactly. The entire method can be extended to systems with two or more current converters (or flexible AC transmission systems) using the multiport theory.