Supervisor:
Frede Blaabjerg

Co-Supervisor:
Saeed Peyghami

Assessment Committee:
Associate Professor Baoze Wei (Chair)
Professor Allessandra Parisoi, University of Manchester, England
Professor Pierluigi Mancarella, University of Melbourne, Australia

Moderator:
Mateja Novak

Abstract:

Microgrids which are combining various renewable energy sources with
conventional power generation and storage systems, play a pivotal role in the pursuit of a sustainable and secure energy supply. However, their reliable and stable operation poses significant challenges due to the inherent complexity and variability of renewable energy sources. Additionally, the prevalence of power electronics in microgrid components intensifies these challenges, as they inherently exhibit higher failure rates compared to conventional power system components. Furthermore, the
small size, lower inertia, and strong coupling between variables in microgrids mean that even minor disturbances can disrupt stable operation and affect dynamic performance. Recognizing the critical importance of addressing dynamic failures initiated from stability challenges in the design and operation of microgrids, this thesis aims to develop a comprehensive solution for doing concurrent engineering design. It is noted that conventional design guidelines often focus solely on component failures
or static failures, neglecting the impact of dynamic failures and their constraints.
However, these dynamic failures can have a significant impact on both short-term and long-term operation of microgrids, ultimately deteriorating the overall risk of the system. Therefore, the need to address these dynamic failures in microgrid design and operation is paramount for ensuring their reliable and stable performance.
To address these concerns, the first step is to introduce a new design guideline that provides a specific roadmap for integrating stability issues into conventional risk assessment models and methods. This framework enables simultaneous evaluation of both static and dynamic failures in microgrids, considering different time resolutions.
If the overall risk is deemed unacceptable, the microgrid will undergo redesigning, starting from the component level up to the system level. The redesign strategies may involve reconfigurations within the microgrid, adjustments to the quantity and size of specific components, and the selection of appropriate renewable energy sources.
To address the diverse impacts of stability issues on system risk, the proposed model introduces a comprehensive guideline for addressing all stability challenges in microgrids. This involves conducting root cause analyses and time domain simulations to identify instability causes, followed by determining the feasibility of incorporating specific stability challenges as constraints or limitations in the reliability modeling. Some stability challenges may be excluded from the analysis due to their
duration or low significance in the overall system risk. This approach allows for the analysis of various short-term and long-term challenges and mitigates their impacts on system risk through appropriate system redesign measures.
This multi-domain design framework offers practical solutions to do risk assessment and mitigate stability issues during both the planning and operation phases of microgrids. Case studies and comparative analyses further validate the efficacy of the proposed framework, demonstrating its ability to understand and analyze the reliability and stability of microgrid systems and reduce the system risk.