Changeover circuit for anti-parallel three=phase bridges - displaces changeover time-point to minimise output current symmetry

摘要

The changeover circuit causes the time when changeover from one 3-phase bridge to the other to follow the phase shift between the passages through zero of the ac output voltage and the passages through zero of the ac output current's fundamental frequency. The asymmetry of the output current with time is measured. This asymmetry increases with the increasing difference between load angle and changeover angle. The asymmetry is determined by measuring the current flowing through one of the converter's outputs and is described by an electrical signal which is used to shift the changeover angle until the signal is a minimum.