Power Converter Sizing for a Switched Doubly Fed Machine Propulsion Drive

Doubly fed machines (DFMs) can be used to make variable speed drives (VSDs) that not only provide full shaft speed control but also avoid the need for a dc electrical bus capable of providing full mechanical shaft power. This makes the DFM attractive for any VSD application where the primary power source is ac. Switching configuration of the DFM on-the-fly opens up opportunity to operate the DFM on a wider speed range with reduced power electronics. This paper explores the design requirements for a switched DFM rotor power electronics in full-speed-range VSD applications, including propulsion drives. Tradeoffs are examined for power electronics sizing versus transient settling characteristics.