Abstract: 

The increasing penetration of inverter-based distributed energy resources (DERs) has transformed modern power systems into low-inertia, weakly damped networks, posing critical challenges for resilient operation. This dissertation proposes a comprehensive framework to enhance the resilience of inverter-based power systems, with particular focus on service restoration, real-time validation, and stability analysis under communication delays. First, a multi-layer cyber-physical service restoration framework is developed for inverter-dominated distribution systems. The restoration problem is formulated as a Mixed Integer Second-Order Cone Program (MISOCP) that incorporates dynamic stability constraints. A distributed multi-agent system (MAS) is also introduced to autonomously coordinate restoration through real-time information discovery, task scheduling, and DER control. The framework’s efficacy is validated on a modified IEEE-123 node test feeder, accounting for network reconfiguration, communication latencies, and multiple fault scenarios. Second, a Controller-in-the-Loop (CIL) real-time testbed is constructed using OPAL-RT simulators and Raspberry Pi-based distributed controllers. Real-time validation of the proposed restoration framework is performed with integrated consensus-based secondary control for voltage and frequency regulation. Highspeed Redis middleware is employed to manage data exchange across cyber and physical layers. Finally, the dissertation presents a detailed stability analysis of islanded inverter based microgrids (MGs). A nonlinear time-delayed state-space model is developed to capture hierarchical inverter controls, network dynamics, and communication effects. Both small-signal (eigenvalue-based) and large-signal (Lyapunov based) methods are employed to assess delay-dependent stability margins. The analysis demonstrates the critical role of grid-support functions in enhancing operational stability and survivability post-restoration.  The findings contribute toward scalable, communication-aware resilience strategies for future inverter-dominated smart grids.

Final Thesis Defense Committee: 

1. Dr Faisal Nadeem (External Examiner), Associate Professor EE, UET Taxila 

List of Publications: 

Journals:  

1. C. T. Hassan and T. M. Jadoon. and A. Arif (2025). “Delay-dependent small stability analysis of inverter-based islanded microgrids”. IET Smart Grid. 10.1049/stg2.12206.

Conferences:

1. C. T. Hassan and T. M. Jadoon, “A Framework for Service Restoration of Cyber-Physical Power Systems,” 2023 IEEE PowerTech, Belgrade, Serbia, 2023, pp. 1-7, doi: 10.1109/PowerTech55446.2023.10202848.

2. C. T. Hassan and T. M. Jadoon, “A Multi-Agent FLISR Model for Smart Grids,” 2023 IEEE PowerTech, Belgrade, Serbia, 2023, pp. 1-6, doi: 10.1109/PowerTech55446.2023.10202874.

3. C. T. Hassan and T. M. Jadoon, “Cyber-Physical Design and Implementation of Service Restoration Framework for Islanded Power Systems,” 2023 International Conference on Future Energy Solutions (FES), Vaasa, Finland, 2023, pp. 1-9, doi: 10.1109/FES57669.2023.10183314.

4. C. T. Hassan and T. M. Jadoon, “Large-Signal Stability Analysis of Low- Inertia Dynamic Microgrids During Black-Start,” 2024 IEEE Workshop on Control and Modeling for Power Electronics (COMPEL), Lahore, Pakistan, 2024 pp. 1-5, doi: 10.1109/COMPEL57542.2024.10614051

5. C. T. Hassan and T. M. Jadoon, “Modeling and Stability Analysis of Inverter based Networked Microgrids,” 2025 IEEE PowerTech, Kiel, Germany 2025, June 29-July 3. Accepted for publication.