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Quantitative Resilience Metrics for Real-time Monitoring and Assessment of DC Microgrids in Naval Applications

Core Concepts
This paper proposes a novel set of quantitative resilience metrics to assess the operational resilience of DC microgrids in naval applications in real-time.
This paper introduces a comprehensive set of resilience metrics tailored for DC microgrids, particularly in the context of naval applications. The proposed metrics provide real-time tracking, computational efficiency, and compatibility with various microgrid designs. The key highlights and insights are: The paper proposes a voltage resilience index (RV) that quantifies the microgrid's ability to retain memory from past voltage perturbations and learn from them. A voltage vulnerability index (VVI) is introduced to evaluate the extent of voltage degradation during an event. A voltage degradation index (VDI) is developed to capture the temporal behavior of the system's voltage performance, providing insights into the onset, duration, and termination of the degradation phase. A voltage restoration efficiency index (VREI) is formulated to assess the microgrid's capability to rapidly recover its voltage to the desired level after a disturbance. The proposed metrics are validated through simulation studies involving sudden load changes and generator failures in a 6 kV MVDC shipboard microgrid. The results demonstrate the effectiveness of the metrics in tracking the microgrid's resilience in real-time. It is shown that the voltage recovery index VREI is closely related to the inertia of the DC microgrid, represented by the equivalent capacitance Ceq, and can accurately capture the microgrid's recovery speed after an event. The comprehensive set of resilience metrics introduced in this paper provides valuable real-time information to microgrid operators, enabling them to monitor the microgrid's resilience and identify potential deterioration over time. This is a significant advancement in the field of resilience assessment for DC microgrids in naval applications.
The percentage of voltage deviation from the reference value (voDC) during an event can reach up to 20%. The time taken for the microgrid to fully restore its voltage after an event can vary from 2 to 4 seconds, depending on the inertia of the system.
"Resilience is emerging as an evolving notion, reflecting a system's ability to endure and adapt to sudden and catastrophic changes and disruptions." "Given the significant electrical needs of naval ships, which encompass advanced weaponry, navigation systems, and communication apparatus, MVDC shipboard microgrids are considered in this paper." "To the best of our knowledge, there exists no previous research that presents a set of metrics within the context of real-time operational resilience assessment for DC microgrids that are capable of quantifying various event phases, ensuring computational efficiency, exhibiting compatibility, and offering real-time tracking."

Deeper Inquiries

How can the proposed resilience metrics be extended to assess the resilience of hybrid AC-DC microgrids in naval applications

The proposed resilience metrics for DC microgrids in naval applications can be extended to assess the resilience of hybrid AC-DC microgrids by incorporating additional parameters and considerations specific to hybrid systems. In hybrid AC-DC microgrids, the interaction between AC and DC components introduces new challenges and opportunities for resilience assessment. One way to extend the proposed metrics is to include metrics that account for the coordination and control strategies between AC and DC subsystems. This could involve developing metrics that evaluate the seamless transition between AC and DC modes, the effectiveness of power sharing between AC and DC sources, and the overall system stability during mode transitions. Furthermore, the resilience metrics can be adapted to capture the impact of hybrid configurations on system performance during both normal and abnormal operating conditions. This may involve assessing the resilience of hybrid microgrids to faults, disturbances, and cyber-physical attacks that can affect both AC and DC components. By integrating these considerations into the existing resilience metrics, a comprehensive assessment framework can be developed to evaluate the resilience of hybrid AC-DC microgrids in naval applications, ensuring the robustness and reliability of these complex systems.

What are the potential limitations of the voltage-based resilience metrics, and how can they be complemented by other performance indicators to provide a more comprehensive resilience assessment

While voltage-based resilience metrics provide valuable insights into the performance of DC microgrids, they have certain limitations that can be complemented by other performance indicators to offer a more comprehensive resilience assessment. One potential limitation of voltage-based metrics is their focus on a single aspect of system performance, which may not capture the full spectrum of resilience factors. To address this limitation, additional metrics related to system stability, frequency response, energy management, and communication network resilience can be incorporated into the assessment framework. By combining voltage-based metrics with metrics that evaluate system dynamics, control strategies, and communication protocols, a more holistic view of microgrid resilience can be obtained. This integrated approach can provide a deeper understanding of the system's ability to withstand and recover from various disturbances and threats. Furthermore, the use of multi-dimensional resilience metrics that consider not only technical aspects but also economic, environmental, and social factors can offer a more comprehensive assessment of microgrid resilience. By incorporating a diverse set of performance indicators, decision-makers can make informed choices to enhance the overall resilience of DC microgrids in naval applications.

What are the implications of the relationship between the voltage recovery index (VREI) and the microgrid's inertia (Ceq) on the design and optimization of DC microgrids for enhanced resilience in naval applications

The relationship between the voltage recovery index (VREI) and the microgrid's inertia (Ceq) has significant implications for the design and optimization of DC microgrids in naval applications to enhance resilience. A higher value of Ceq, representing greater virtual inertia in the system, can lead to improved stability and faster recovery of the microgrid voltage after disturbances. This relationship highlights the importance of designing DC microgrids with adequate inertia to enhance their resilience to sudden load changes, faults, and other disruptions common in naval applications. By optimizing the microgrid's inertia through appropriate sizing of energy storage systems, control strategies, and network configurations, the voltage recovery index can be enhanced, leading to quicker restoration of system performance post-events. This optimization process can involve dynamic control algorithms that leverage the system's inertia to dampen voltage oscillations and maintain grid stability during transient conditions. Overall, the relationship between VREI and Ceq underscores the critical role of inertia in enhancing the resilience of DC microgrids in naval applications. By considering this relationship in the design and optimization process, naval engineers can develop more robust and reliable microgrid systems that can effectively withstand and recover from disturbances, ensuring continuous power supply in challenging maritime environments.