Effects of interaction among groups in a multigroup a.c.ߝd.c. convertor

The paper presents an analysis of the behaviour of multigroup convertors. In such convertors, for certain system configurations and operating conditions, an interaction takes place amongst convertor groups. The mechanism of interaction is analysed, and it is shown that this is due to a commutating impedance shared by the convertor groups. This interaction, which is expressed in terms of a coupling factor, is shown to affect rectification by a modification of the voltage waveform across the rectifying elements in the region of natural ignition. For inversion, the interaction modifies the waveform in the region of extinction. The various modes of operation and the boundary parameters between modes are derived, and overall regulation characteristics are shown. The analysis covers both positive and negative coupling facto´s, the relevance of compensating reactors and filters being stressed.