Abb Technology Ag

Hitachi Energy Switzerland Ag

Thomas Schaad

Jan Svensson

Philippe Maibach

Georgios Stamatiou

Marc Willomitzer

An AC-to-AC modular multilevel converter (MMC) is configured to be connected between a three-phase AC system and a single-phase AC system. The MMC includes a number of converter arms connected in a ring to allow a circulating current to be circulated in the ring through each of the converter arms. Each converter arm includes series-connected converter cells. Phase terminals are arranged in the ring between the converter arms such that each of the converter arms is separated from neighboring converter arms by at least one of the phase terminals. The phase terminals include respective terminals for each of a first phase, a second phase and a third phase of the three-phase AC system and respective terminals for each of a positive conductor and a negative conductor of the single-phase AC system.

AC-to-AC MMC with reduced number of converter arms

A method is disclosed for operating a converter circuit, in which controllable power semiconductor switches of the rectifier unit of a converter circuit are controlled by a rectifier switch signal and the controllable power semiconductor switches of the inverter unit of the converter circuit are controlled by an inverter switch signal. In order to reduce losses in the no-load state of the converter circuit, the rectifier switch signal is blocked in order to disconnect the controllable power semiconductor switches of the rectifier unit if defined conditions of the converter circuit are fulfilled.

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Oberbipp, Switzerland

Thomas Schaad