UNIfying Grid-FOllowing And Grid-foRMing Control In Inverter-based Resources (UNIFORM)
Lead Research Organisation:
University of Southampton
Department Name: Sch of Electronics and Computer Sci
Abstract
The ambitious decarbonisation energy targets of the UK and worldwide will lead to unprecedented levels of inverter-based resources (IBRs) (e.g. wind, solar, electric vehicles) into the power system. National Grid ESO, partner of the project, forecasts a threefold IBR increase from about 10GW in 2020 to approximately 30GW by 2028. This rapid transformation of our power system comes with new opportunities, as well as new operational and stability challenges. The power electronics (inverters) of IBRs allow for faster and much more programmable operation compared to the machines of conventional power plants, but they also behave very differently during disturbances (e.g. line faults, generator trip). This different dynamic response gives rise to a multitude of inverter-driven instabilities in the network, with National Grid ESO raising a red flag for such complications in distant wind farms in North Scotland by 2030 due to weak grid, and for the entire GB network with the rapid reduction of its system inertia. Not resolving these issues equals to limiting the IBR penetration into our network and failing our net-zero targets.
These challenges relate primarily to the dynamic behavior of the inverters. Conventionally, IBRs have been operating in 'grid-following' mode (GFL), that is behaving like a current source in the network. Lately, 'grid-forming' (GFM) has emerged as an alternative that emulates voltage-source characteristics. However, recent findings show that while GFL fails at weak grid, GFM also fails at strong grid, hence neither technology is a silver bullet for all grids and conditions. As a compromise to this, system operators are currently looking into distributing GFL and GFM inverters across the network in the "right mix", which is really a makeshift measure and cannot address the issue fully.
UNIFORM approaches this problem from an entirely new perspective. Instead of mixing individual current and voltage sources within the network, we will combine these two behaviors within the inverter itself. By unifying the GFL and GFM modes into a universal 'Composite V-I source', every single inverter can emulate a hybrid voltage/current response at a programmable ratio depending on the grid conditions. That essentially means a universal controller that (i) synchronizes robustly to any grid, and (ii) emulates an inverter output that ensures the best possible stability outcome. This will be the steppingstone in unlocking the true potential of IBRs and increase the stability margin of any IBR-driven network, thus paving the way for the envisioned 100%-IBR power system.
A rare academia-industry partnership is formed to implement this idea. The University of Southampton will be leading the project, leveraging on the PI's specialization on inverter control, and closely working with the international partner NTUA (Prof Nikos Hatziargyriou), world-leading expert in grid stability. National Grid ESO will be sharing case studies and real-life experience from the GB network, while Smart Power Networks will be guiding the experimental validation phases towards industrial exploitation. An elaborate knowledge exchange and research visits plan will establish a strong partnership with unique and complementary skillsets that will innovate in the emerging area of 'inverter-driven power systems'. These tools and knowledge have the potential to not only facilitate meeting our energy targets, but also boost our position as a global leader in a field with tremendous industrial and commercial potential worldwide.
These challenges relate primarily to the dynamic behavior of the inverters. Conventionally, IBRs have been operating in 'grid-following' mode (GFL), that is behaving like a current source in the network. Lately, 'grid-forming' (GFM) has emerged as an alternative that emulates voltage-source characteristics. However, recent findings show that while GFL fails at weak grid, GFM also fails at strong grid, hence neither technology is a silver bullet for all grids and conditions. As a compromise to this, system operators are currently looking into distributing GFL and GFM inverters across the network in the "right mix", which is really a makeshift measure and cannot address the issue fully.
UNIFORM approaches this problem from an entirely new perspective. Instead of mixing individual current and voltage sources within the network, we will combine these two behaviors within the inverter itself. By unifying the GFL and GFM modes into a universal 'Composite V-I source', every single inverter can emulate a hybrid voltage/current response at a programmable ratio depending on the grid conditions. That essentially means a universal controller that (i) synchronizes robustly to any grid, and (ii) emulates an inverter output that ensures the best possible stability outcome. This will be the steppingstone in unlocking the true potential of IBRs and increase the stability margin of any IBR-driven network, thus paving the way for the envisioned 100%-IBR power system.
A rare academia-industry partnership is formed to implement this idea. The University of Southampton will be leading the project, leveraging on the PI's specialization on inverter control, and closely working with the international partner NTUA (Prof Nikos Hatziargyriou), world-leading expert in grid stability. National Grid ESO will be sharing case studies and real-life experience from the GB network, while Smart Power Networks will be guiding the experimental validation phases towards industrial exploitation. An elaborate knowledge exchange and research visits plan will establish a strong partnership with unique and complementary skillsets that will innovate in the emerging area of 'inverter-driven power systems'. These tools and knowledge have the potential to not only facilitate meeting our energy targets, but also boost our position as a global leader in a field with tremendous industrial and commercial potential worldwide.
