Dissertation Defense

Managing Uncertainties in Grid-Integration of Distributed Energy Resources: Safety, Stability, and Optimality

Sijia Geng

Electric power systems are undergoing drastic transformations from centralized fossil-fuel-based generation to renewable and distributed energy resources (DERs). However, DERs are typically small in capacity and renewable generation is inherently variable, rendering hundreds of millions of uncertain control points. Moreover, DERs are typically connected to the grid through inverter interfaces, resulting in dynamic characteristics that are vastly different to traditional synchronous generators. These technical challenges must be addressed to guarantee safe and stable system operation and a successful transition to a clean energy future.

This dissertation addresses the critical issues of safety and stability of power systems that integrate substantial renewable DERs. Specifically, theoretical results are developed to analyze the impacts of uncertainties on system dynamics, enabling an efficient safety verification algorithm. Secondly, the dynamic characteristics of inverter-based power systems are investigated. Two distributed inverter control schemes are proposed to achieve autonomous grid-interconnection and safety certification. Thirdly, rigorous stability guarantees are established for distributed controllers that exploit the collective capability of DERs to balance voltages across the distribution network.

Furthermore, this dissertation establishes a design process for next-generation off-grid energy systems, such as renewable-only microgrids and community-based energy hub systems that incorporate multiple energy carriers. The variability and uncertainty of renewable resources are explicitly managed. This design process promotes local clean energy generation and rural area electrification.

Chair: Professor Ian Hiskens