The packaging of the modules is designed to satisfy requirements for series and parallel interconnection among modules, high power density, high thermal efficiency, small size, and light weight. Each module includes four output power connectors — two for serial and two for parallel output power connections among the modules. Each module also includes two signal connectors, electrically isolated from the power connectors, that afford four zones for signal interconnections among the SOI controllers. Finally, each module includes two input power connectors, through which it receives power from an in-line power bus. This design feature is included in anticipation of a customdesigned power bus incorporating sockets compatible with “snap-on”� type connectors to enable rapid replacement of failed modules.

The distributed control hardware and software enable power conversion to continue uninterrupted when as many as two modules fail. Essential to distributed control is an arbitrated, shared communication bus. The arbitration protocol enables asynchronous bidirectional messaging without concern for data collisions and loss of messages. In tests of the four-module system in which failures of as many as two modules were simulated, measurement results showed that the system reconfigured itself rapidly enough in response to the failures to continue delivering power to a load without interruption and with minimum output-voltage sag. The transient time associated with a failure was found to be <5 ms, of which <350 μs was consumed by software and the rest was consumed by operation of bypass relays.

This work was done by Alexander Lostetter and Steven Franks of Arkansas Power Electronics International, Inc. for Glenn Research Center.

Inquiries concerning rights for the commercial use of this invention should be addressed to NASA Glenn Research Center, Innovative Partnerships Office, Attn: Steve Fedor, Mail Stop 4-8, 21000 Brookpark Road, Cleveland, Ohio 44135. Refer to LEW-18008-1.