Operational Resilience Assessment in DC Shipboard Microgrids: A Short-Term Energy Imbalance Approach Based on Frequency-Domain Metrics

DC shipboard microgrids (SMGs) are highly dynamic systems susceptible to failures due to a variety of cyber-physical disturbances, including extreme weather conditions and wartime operations. This paper proposes a frequency-domain approach for quantifying real-time operational resilience (OR) of DC SMGs against short-term disturbances. To this end, first, the drawbacks of time-domain OR evaluation using an energy imbalance index are discussed, particularly when applied to droop-controlled DC SMGs without secondary voltage restoration control. Subsequently, to address these drawbacks, two frequency domain metrics, namely ${\mathcal {H}}_{2}$ and ${\mathcal {H}}_{\infty}$ norms of candidate transfer functions (TFs) of the system, are proposed as quantifiable measures of OR. It is shown that the proposed frequency-domain metrics calculated for the bus impedance TF of the DC SMG provide intuitive results in terms of short-term energy imbalance and can be computed in real time. The case studies conducted for the study DC SMG under pulsed power load (PPL) disturbances demonstrate the drawbacks of the time-domain OR evaluation and the capability of the proposed frequency-domain metrics in OR evaluation of DC SMGs under various operation scenarios.