Three-phase ac-to-dc-to-ac converter

A three-phase ac-to-dc-to-ac power converter system with reduced power loss, comprising:

• (a) a first, a second and a third ac input terminal for inputting a first-, a second- and a third-phase ac voltage;
• (b) a first, a second and a third ac output terminal for outputting a first-, a second- and a third-phase ac voltage;
• (c) a three-phase ac-to-dc converter circuit connected to the ac input terminals, the three-phase ac-to-dc converter circuit comprising a plurality of ac-to-dc conversion switches and a pair of outputs for providing a dc output voltage;
• (d) storage means connected between the pair of outputs of the three-phase ac-to-dc converter circuit for storing output energy therefrom;
• (e) a three-phase dc-to-ac converter circuit connected between the storage means and the ac output terminals, the three-phase dc-to-ac converter circuit comprising a plurality of dc-to-ac conversion switches for providing the three-phase ac output voltages;
• (f) a bypass switch connected between a preselected one of the ac input terminals and a preselected one of the ac output terminals;
• (g) ac-to-dc converter control means connected to the three-phase ac-to-dc converter circuit for controllably driving the ac-to-dc conversion switches thereof;
• (h) dc-to-ac converter control means connected to the three-phase dc-to-ac converter circuit for controllably driving the dc-to-ac conversion switches thereof either in or out of synchronism with the three-phase ac input voltages;
• and
• (i) bypass switch control means connected to the bypass switch for holding the bypass switch closed when the three-phase dc-to-ac converter circuit is being driven in synchronism with the three-phase ac input voltages, and open when the three-phase dc-to-ac converter circuit is being driven out of synchronism with the three-phase ac input voltages.