Control system for three=phase converter - applies voltage varying at output frequency times number of phases to three converter sections

TLDR: In this article, a three phase converter with a return section for each phase, for operating a machine at high loads and low speeds, with their output sides star connected, reduces the blind loading.

Abstract: The three phase converter with a return section for each phase, for operating a machine at high loads and low speeds, with their output sides star connected, reduces the blind loading. Within the control region, each section is fully controlled by a variable additional voltage. The resulting combined output voltage is sinusoidal. Each section is cyclically reversed at the output frequency of the direct converter. The frequency of the additional control voltage corresponds to the output frequency multiplied by the number of phases. The control voltage is obtained from the differences of maximum and minimum sinusoidal values.