Ensuring system security and stability is an ever-present concern in power system engineering due to the crucial importance of reliable power supply in modern society. The growth of renewable energy increases the number of power electronic converters present in the power network since they are needed to interface non-conventional forms of generation to standard 50 or 60 Hz system. This changes the network's physical structure and causes new threats to security. Compared to conventional power equipment, power electronic converters are subject to rigid capacity constraints which make them prone to lose functionalities during large disturbances and trigger fault cascading. On the other hand, converters have higher flexibility and faster response which enable more versatile patterns of dynamic control. Therefore, a new methodology for both converter design and system operation is needed to take advantage of the strengths and mitigate the weaknesses of converters in supporting grid security. This problem is difficult because power electronic converters have sophisticated internal dynamics which further interact with a complex power network with a vast number of nodes and uncertain disturbance scenarios. What adds to the difficulty is that converters and networks are created by very different owners and supply chains that newly come together but still have different perspectives and technical languages. This fellowship aims to establish a common technology framework for converter manufacturers and network operators, and find a systematic methodology and practical tools for grid-supportive converter design and converter-based grid security management. The proposed research sets out to do three things. First, it will find analytical methods to quantify the support provided by and stress placed on converters regarding network security, from which converter design guidelines will be derived to optimize the security support functions in a cost-effective way. Second, it will build computational platforms for network operators to use a vast number of converters synergistically for real-time security management. Third, it will develop proof-of-concept prototypes, demonstrate their application potential in a complex power system, and promote commercialization and standardization.

It is very important that the electrical power grid is secure and reliable. Almost all aspects of our lives are dependent on electricity, from basic needs like heating and lighting to medical technology and vast city infrastructure and transportation systems. Just one day of blackout would cost the UK billions of pounds in lost revenue from businesses that are unable to operate - and the impact on society would be enormous. It is also very important that we begin, as a nation, to generate more electricity from low-carbon, renewable technologies such as solar and wind power. This is essential to ensure that we slow the effects of climate change and develop energy resources which will last for future generations. Renewable energy sources are unpredictable - we just don't know exactly how much electricity we can generate from the wind turbines or solar panels day-to-day. We can make predictions but they are uncertain predictions - we can't make guarantees. Unfortunately this doesn't help when it comes to making sure our electricity supply is secure and reliable. Electrical demand has to be balanced with electrical generation at every instant. We presently don't have the technology to store electricity on a large scale (we can't build batteries that could power the whole country), and the unpredictability of large numbers of wind farms and solar panels makes it harder and harder to keep the system balanced. Get this balance wrong, and the system could collapse, potentially resulting in a nation-wide blackout. To make matters worse, this is just one source of uncertainty among many others that affect the performance of electricity grids. For example, the wide-scale uptake of electric vehicles will add lots more demand for electricity which can literally move around the network - so not only is there uncertainty over when the vehicle is charged, but also where it is charged. There is a pressing need to fully understand how uncertainties will impact on the performance of power systems. This begins by building an understanding of which uncertainties are the most important. There are so many potential sources of uncertainty that getting enough data to understand how they all change would be completely impractical. Instead, if we can identify the most important uncertainties - the critical uncertainties that dominate the way the electricity grid behaves - we can focus our future attention on understanding those first, and stopping them from causing any problems. Identifying these uncertainties is not a simple task and requires new tools and techniques to be developed. These tools not only need to examine all possible consequences of all the possible scenarios (as it is usually unexpected scenarios that cause the most problems), but also need to quantify the importance of different sources of uncertainty in practical terms so power system engineers can be confident in the decisions they are making. This project will develop these tools in the form of new software algorithms which will be thoroughly tested to find their strengths and limitations. This work will provide the foundation for future research on uncertainty in electrical power grids, helping to identify and solve critical issues to improve the security and reliability of the electricity supply.

The UK needs to reduce the amount of fossil fuels it uses for heating / transport to reduce the amount of carbon dioxide we emit into the atmosphere. Replacing fossil fuels will only be possible through the use of more electricity generated from low carbon sources (nuclear, wind, solar and marine). Estimates suggest the electricity transmission system may need to carry a peak power four times higher than is carried today. The power that flows through the transmission system will also become more intermittent as wind and solar power is dependent on variable weather conditions. We therefore need to develop a new generation of equipment that can be used to carry electricity from generator to customer. This equipment needs to be cost-effective and have a minimal impact on the environment (whether this be measured in terms of visual impact, noise, ability to recycle at end of life or a whole range of other factors). The advances in disciplines such as material science mean there are many exciting opportunities to examine new ways to manufacture and operate transformers, overhead lines, cables and circuit breakers that will be used on the electrical transmission system. We need to have facilities that are capable of translating underpinning science at the scale of full size transmission system equipment. We need to ensure we can test objects measuring some metres in length with a maximum weight of thousands of kilograms. We need to apply over 400,000 volts continuously to this equipment and at times up to 1.6 million volts to simulate the impact of lightning. We can only do that using a specialist facility that includes a large space into which we can place equipment and the high voltage test sets. The test supplies must be capable of testing equipment when we spray water onto surfaces in a way that represents rainfall. It must operate 'quietly' and allow us to measure extremely small electromagnetic signals associated with failures in insulation systems. Delivering this test facility will ensure we can help the efforts to decarbonise the UK energy system. The facility will allow the UK academic community to play a leading role in the global research community that is developing new insulation systems and the next generation of transmission system equipment. Working with the new full-size substation being developed by National Grid to test equipment for prolonged periods, we will attract industry to the UK and will support the efforts of smaller companies to convert their ideas into reality. Through the facility we will train the next generation of engineers who will support the efforts to develop a low carbon electricity system that is reliable and provides low cost energy to customers for many years to come.

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.

Managers, consultants, and security engineers have responsibility for delivering the security of possibly large, complex systems. Policy-makers and industry/business leaders, on the other hand, have responsibility for ensuring the overall sustainability and resilience of information ecosystems that deliver services, including those in commercial, governmental, intelligence, military, and scientific worlds. Despite these differences in focus and scope, both groups must make security policy design decisions that combine a wide range of competing, often contradictory concerns. Considering this range of stakeholders, we are motivated by the following closely related questions: For a given system, with a given set of stakeholders operating in given business and threat environments, how do we determine what is an appropriate (i.e., effective, affordable) security policy? What attributes should be protected, to what extent, in what circumstances? What impact on business operations is acceptable, and at what financial cost? Such an analysis will, if it is to be achievable and robust, be dependent on the provision of rigorous economic and mathematical models of systems and their operations. How are we to express and reason about policies so that their effectiveness against the desired security outcomes and their impact upon the stakeholders and business operations can be understood? Our hypothesis, supported both by extensive background work and experience in an industrial setting and by extensive background mathematical work, is that a marriage of the modelling techniques of logic with those of mathematical economics will provide an appropriate framework. We aim to establish a mathematical basis for a systems security modelling technology that is able to handle the structural aspects of systems, the stochastic behaviour of their environments and, specifically, a utility-theoretic representation of security policies and their effectiveness. The development of this theory poses significant challenges. We need to reconstruct utility theory to take advantage of the sophisticated account of actions provided by the mathematical models of processes common in theoretical computer science. Another technique of theoretical computer science, Hennessy-Milner logic, provides a logical characterization of process behaviour; this will need to be enhanced to enable specification of properties involving utility- and game-theoretic concepts, such as Pareto optimality and equilibrium properties. The development of this novel mathematics must be driven and guided throughout by the policy decision-making applications, and we must explore how the methodology used in previous work can be extended and generalised to take advantage of this new mathematics.