Thesis

Load shedding and voltage management strategies for enhancing resilience in remote DC microgrids

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Awarding institution
  • University of Strathclyde
Date of award
  • 2025
Thesis identifier
  • T17464
Person Identifier (Local)
  • 202091771
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Qualification Name
Department, School or Faculty
Abstract
  • Reliable and efficient power systems are crucial in areas with limited access to electricity, such as sub-Saharan Africa. Over 50% of rural areas in this region remain disconnected from the national grid due to high transmission and distribution costs. Direct Current (DC) microgrids have emerged as a promising solution, offering advantages such as lower investment costs, improved flexibility, and direct integration of renewable energy sources such as solar power, which is abundant in Africa. The successful operation of DC microgrids requires robust control to regulate DC bus voltages, efficient power sharing between the distributed energy resources (DERs), and a dynamic response to disturbances. However, when the power demand of the loads exceeds the power generation from the DERs in the DC microgrid, voltage control alone cannot maintain the power balance. In such cases, it is necessary to shed some of the noncritical loads to prevent power shortages and enhance the system’s resilience against disruptions. This thesis addresses key challenges in voltage regulation and load management in DC microgrids through the development of enhanced DC bus voltage control and load-shedding strategies aimed at improving voltage stability and overall system resilience. First, it introduces a disturbance identification technique based on the rate of change of voltage (dv/dt), enabling rapid detection, localisation, and quantification of disturbances. This fast and accurate response is crucial in minimising system disruption and facilitating timely corrective actions. Second, an adaptive DC bus signalling (DBS) control strategy is proposed, which dynamically adjusts voltage thresholds according to load demand and generation levels. This approach improves system stability by preventing excessive voltage fluctuations and improving responsiveness during disturbances. Furthermore, when the system experiences a power deficit, the control scheme activates a load-shedding mechanism to maintain operational balance. Third, to Further strengthen system resilience, a novel load-shedding scheme is developed by integrating timer-based control with a mixed-integer linear programming (MILP) algorithm. This approach optimises the load shedding of non-critical loads during severe disturbances, effectively restoring power balance, reducing voltage sags, and minimising reliance on costly communication-based infrastructure. Simulation results demonstrate that the enhanced DBS control strategy effectively maintains power balance, limits DC bus voltage deviations to within +/-10% based on IEC standard, prevents voltage collapse, and enables smooth transitions between operational states without inducing power oscillations among DERs. Furthermore, the proposed MILP timer-based load-shedding scheme demonstrates superior performance over conventional and adaptive methods by delivering faster and more accurate load-shedding actions. This leads to better protection of critical loads and strengthens the overall integrity and resilience of the DC microgrids. The findings of this research make a significant contribution to improving the reliability, efficiency and resilience of DC microgrids. These positions DC microgrids as a viable energy solution: particularly well suited for remote areas, improved energy storage coordination, and the integration of renewable energy systems for electrification efforts in sub-Saharan Africa and other disaster-prone or underserved regions around the world.
Advisor / supervisor
  • Burt, Graeme
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