Distributed independent controls for managing short circuit faults in MVDC power systems

Abstract

For Medium Voltage DC (MVDC) power systems, we greatly extend the coverage of local-information-based fault protection (LIFP), an approach defined for independent distributed management of short-circuit line-to-line faults that does not rely on any high-speed ship-wide communications, to arc faults under varying load conditions. The method for LIFP was previously developed for systems where all loads operate at steady state between each system reconfiguration [1][2]. But the power demand of system loads can be time varying and this characteristic complicates implementation of the LIFP method. On the other hand, emerging standards will ensure that power ramping rates will be limited for large loads and this provides the necessary means to extend the LIFP more broadly [3]. Using a reference system model, we demonstrate the effectiveness of an improved LIFP, which allows each system component to autonomously identify and appropriately react to the presence of a fault, without mis-tripping under the influence of load variations. For the load variation events with a ramping rate of 50A/ms, LIFP can successfully identify the incident and initiate adjustment of tripping thresholds within 4.5ms. Whereas for the arc faults tested, one at a time, throughout the system, LIFP is always true positive for disconnecting fault from the system.