Protection and Control of Power Grids with up to 100% Penetration of Renewable Energy Sources

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Renewable energy sources have accounted for more than 80% of new electricity capacity added globally in recent years, triggering a paradigm shift in the operation of power grids. The inverter interfaces of these sources have unconventional fault responses and threaten the reliability of today's protection systems. This is evidenced by the steady growth in the number of disturbances that involve inverter-based resources (IBRs). As the shift in the generation mix intensifies, the critical absence of protection systems that are compatible with the characteristics of IBRs threatens a new era of declining grid reliability. Meanwhile, higher IBR penetration makes the operation of protective devices and inverter controllers increasingly interdependent. Addressing these challenges requires more than an either protection-only or control-only approach; a multifaceted, yet coherent, approach involving both protection and control is needed. Accordingly, the proposed research program addresses the following fundamental requirements of the future grid. 1. Development of protection systems for power grids supplied mainly or only by IBRs: When the IBR penetration is low, an IBR negatively affects primarily the relays of its direct tie-line. Since the number of IBR tie-lines in transmission networks is limited, IBRs have not yet seriously undermined the overall integrity of protection systems. When the share of IBRs rises, however, their impact will spread across the grid. This will elevate the protection challenges to a whole new level as the core design of existing relays was originally intended for the legacy power grid. This program will target a major redesign of the protection systems based on the IBRs' fault behaviour. 2. Devising inverter control schemes for the fault conditions of renewable energy-centric grids: To increase protection reliability, grid codes (GCs) attempt to make the IBR fault currents predictable. However, today's GCs still include uncertainties about the IBR fault current due to (i) some subtle but critical blind spots in the GCs, (ii) the GCs' silence about some emergent inverter control strategies, and (iii) some IBRs' undesired exemptions from certain GC provisions to accommodate the inflexibility of their control. This program will (i) shed light on so-far-unknown aspects of the GCs' fault current requirements, (ii) identify necessary changes in the next generation of GCs, and (iii) develop control schemes that satisfy these GC requirements. In addition to creating economic opportunities for Canada's energy sector, the technologies and HQPs delivered by this program enable large-scale grid integration of green energy sources, alleviating the environmental and socio-economic repercussions of climate change.