Testing Operation and Coordination of DC Solid State Circuit Breakers.

An approach for testing the operation and coordination of medium-voltage dc solid state circuit breakers (SSCB) for shipboard power systems is described. For the considered application, the rate of rise of current during a short-circuit is limited primarily by a small cable inductance. This high rate of rise, coupled with the need to interrupt the current prior to exceeding the limits of the power electronic switches in the SSCBs, necessitates a coordinated protection scheme which can isolate the fault within a matter of microseconds. Challenges in such tests include the high-voltage, high current, high rates of change of current, and the interconnection of devices within a system. Testing of the SSCBs in a system context presents a challenge, as the MVDC system to which these are to be applied has not been realized in hardware. In order to verify the operation of the SSCBs within a system context, a combination of tests and analyses are employed, including off-line simulation, controller hardware-in-the-loop simulation, hardware testing of a single SSCB, and coordination testing with multiple SSCBs. Results are described for testing of 1 kV devices, but the approach is developed to allow for extension for devices of higher voltage ratings.