Electrical power systems are undergoing unprecedented changes that increase the levels of complexity and uncertainty, mainly driven by decarbonisation targets on the way to achieving net zero operation and addressing climate change. As an example, towards this direction the UK government has set a bold target for zero carbon electricity by 2035. Increasing complexity comes from the introduction of a large number of converter-interfaced devices (CID) that exhibit very different dynamic behaviour, governed to a large extent by control. In addition, uncertainty in power system operation is increasing, due to the intermittent behaviour of renewable sources but also increasingly by social behaviour through EVs and potential electrification of heating as well as complex market and power industry structures. This leads to an exploding search space of possible operating conditions and contingencies, which is particularly challenging for computationally intensive stability assessment and dynamic studies. This aspect coupled with the increasing complexity of dynamic behaviour, makes identifying critical operating conditions and contingencies challenging. Consequently, these developments raise the need for improved representation and understanding of dynamic phenomena as well as fast and informative dynamic security and stability assessment. Both aspects are crucial in order to avoid potentially hidden risks of instability that in the worst-case scenario can lead to widespread events and even blackouts. Consequently, the aim of this proposal is to develop methods, tools and models needed to achieve a secure, resilient and cost-effective power system operation. Building on progress made in the initial part of the fellowship, the extension will continue focusing on two main directions. From one hand, it will develop tools, methods and models to represent and investigate the changing dynamic behaviour of power systems in order to capture new arising dynamic phenomena, spanning both transmission and distribution (e.g. offshore/onshore wind, solar PVs, HVDC links, EVs, heat pumps, electrolysers, etc.). On the other hand, it will develop novel machine learning based and data-driven methods for the fast and informative stability assessment as well as the estimation of the stability boundary. This direction will enable unique understanding of the dynamic behaviour that will lead to ancillary services and control to mitigate or alleviate the impact of disturbances and improve system security and resilience. In addition, the fellowship extension will continue and ramp-up engagement with industrial partners to capture practical aspects and fine tune developed methodologies to pave the way for real world applications. In effect, the results of the fellowship will enable more secure, resilient and potentially more cost-effective operation of power systems due to better knowledge of system stability limits. Consequently, much higher integration of renewables and new technologies with various technical and environmental benefits can be achieved in order to meet bold decarbonisation targets in a secure, resilient and cost-efficient manner.

Co-created and delivered with industry, REWIRE will accelerate the UK's ambition for net zero by transforming the next generation of high voltage electronic devices using wide/ultra-wide bandgap (WBG/UWBG) compound semiconductors. Our application-driven, collaborative research programme and training will advance the next generation of semiconductor power device technologies to commercialisation and enhance the security of the UK's semiconductor supply-chain. Power devices are at the centre of all power electronic systems. WBG/UWBG compound semiconductor devices pave the way for more efficient and compact power electronic systems, reducing energy loss at the power systems level. The UK National Semiconductor Strategy recognises advances in these technologies and the technical skills required for their development and manufacture as essential to supporting the growing net zero economy. REWIRE's philosophy is centred on cycles of use cases co-created with industry and stakeholders, meeting market needs for devices with increased voltage ranges, maturity and reliability. We will develop multiple technologies in parallel from a range of initial TRL to commercialisation. Initial work will focus on three use cases co-developed with industry, for transformative next generation WBG/UWBG semiconductor power electronic devices: (1) Wind energy, HVDC networks (>10 kV) - increased range high voltage devices as the basis for enabling more efficient power conversion and more compact power converters; (2) High temperature applications, device and packaging - greatly expanded application ranges for power electronics; (3) Tools for design, yield and reliability - improving the efficiency of semiconductor device manufacture. These use cases will: improve higher TRL Silicon Carbide (SiC) 1-2kV technology towards higher voltages; advance low TRL devices such as Gallium Oxide (Ga2O3) and Aluminium Gallium Nitride (AlGaN), diamond and cubic Boron Nitride (c-BN) towards demonstration and ultimately commercialisation; and develop novel heterogenous integration techniques, either within a semiconductor chip or within a package, for enhanced functionality. Use cases will have an academic and industry lead, fostering academia-industry co-development across different work packages. These initial, transformative REWIRE technologies will have wide-ranging applications. They will enhance the efficient conversion of electricity to and from High Voltage Direct Current (HVDC) for long-distance transfer, enabling a sustainable national grid with benefits including more reliable and secure communication systems. New technologies will also bring competitive advantage to the UK's strategically important electric vehicle and battery sectors, through optimised efficiency in charging, performance, energy conversion and management. New use cases will be co-developed throughout REWIRE, with our >30 industrial and policy partners who span the full semiconductor device supply chain, to meet stakeholder priorities. Through engagement with suppliers, manufacturers, and policymakers, REWIRE will pioneer advances in semiconductor supply chain management, developing supply chain tools for stakeholders to improve understanding of the dynamics of international trade, potential supply disruptions, and pricing volatilities. These tools and our Supply Chain Resilience Guide will support the commercialisation of technologies from use cases, enabling users to make informed decisions to enhance resilience, sustainability, and inclusion. Equity, Diversity, and Inclusivity (EDI) are integral to REWIRE's ambitions. Through extensive collaboration across the academic and industrial partners, we will build the diverse, skilled workforce needed to accelerate innovation in academia and industry, creating resilient UK businesses and supply chains.

There is an urgent need for new power electronic technologies to underpin the transition to net zero. The imminent risks for our planet have been highlighted by UN's Intergovernmental Panel on Climate Change calling our current status 'code red' for human driven global heating in its scientific report published in 2021. Deploying power electronics in renewable generation systems enables smart control of grid networks and efficient energy utilization. This is also true of transportation, which in turn will support a dramatic reduction of the 72% of global primary energy consumption currently wasted world-wide. In this programme grant (PG), we develop a transformative next generation of Aluminium Gallium Nitride (AlGaN) Solid-State Circuit Breakers (SSCBs), with greatly improved efficiency and greater voltage range, to many kVs, enabling anticipated global energy savings >20% compared to continuing with current technologies. Circuit breakers are critical components for safe, reliable electrical power systems, including for power-electronics-dense grids, but a step-change in performance is needed. According to the major power electronics company ABB / Hitachi Energy, SSCBs are 'the weakest link in next-generation electricity infrastructure'. The slow response time of existing mechanical circuit breakers available on the market risks damaging sensitive equipment. The alternative use of Silicon (Si) - based SSCBs, although providing superior switching speed (<1 microseconds) versus mechanical circuit breakers (>100 microseconds), and offering the fast circuit protection critically needed for high-performance power distribution, presently suffer from high conduction losses and are often limited at best to 4-5 kV safe operation for a single chip. Higher voltage ranges are required in increasingly more complex and varied application areas including electric planes and ships. For example, Si-based SSCB inefficiencies would contribute up to an additional 600 Mtons of CO2 emissions per year if implemented in the global cruise liner industry alone. The vision and ambition is to address current roadblocks in power electronics by developing new SSCBs. The limitations in existing technologies can be largely eliminated using ultrawide bandgap AlGaN SSCBs, which conservatively have a 100x improvement in efficiency compared to existing commercial high-voltage devices such as Si insulated-gate bipolar transistors and Silicon Carbide (SiC) metal oxide semiconductor field effect transistors, to enable efficient, compact SSCBs with minimal cooling requirements. In 20 years, it is expected that these highly efficient ultrawide bandgap AlGaN power electronic components will have displaced all other technologies such as Si and SiC for high-current high-voltage uses, e.g. in power distribution and transportation such as in trains, maritime and planes, helping enable a carbon neutral society. The underlying physical reason for the great benefit of using AlGaN is its much greater bandgap (up to 6.2 eV) compared to Si (1.1 eV) and SiC (3.2 eV). The commonly used power electronics Baliga Figure of Merit, i.e. the suitability of a material for power electronics, of AlGaN is nearly 1,800 compared to 1 for Si and 340 for SiC, enabling a revolution in what power electronics will be able to deliver. Many interlinked technological challenges need to be addressed, including AlGaN materials growth, and methods to enable large enough layer thicknesses, alongside the development and fabrication of new device concepts to achieve high performance and reliable AlGaN SSCBs. The PG will be driven by the realization of transformative device prototypes, with ever increasing complexity, challenge and innovation during the course of the PG, ultimately driving UK research in this area towards end-application prototypes. The high-power application space is huge, and developments will be steered by involving end-users in a co-creation role for the SSCB prototypes.

In 2019 48.5% of the 32 GW daily average energy demand in the UK was carbon-free - contributed by wind farms, solar and nuclear energy, alongside energy imported by subsea interconnectors and biomass. This trend supports the "net zero" commitment signed by the government in 2019. However, significant technologies still need to be developed to enable this goal. One key such technology is high voltage direct current (HVDC) grid level transmission which will enable the "supergrid". This is a network of long distance power transmission lines across and between countries and those aforementioned energy production facilities, particularly in remote locations such as offshore wind farms. Increasing the efficiency and power rating of each grid interconnection (as well as reducing their volume and weight) it would mean more widespread implementation and hence better energy security, lower carbon footprint and better energy economy for the UK. Within most interconnectors, 50% of the volume is the power electronics devices, traditionally made from Silicon technology. Silicon Carbide (SiC) has clear advantages over current Silicon technology such as high temperature and higher frequency operation, with lower resultant system weight and volume. Recently, commercially available SiC power devices have recently entered the market with force, predicted to be worth $2bn by 2024, with rapid growth in this technology is being actively driven by a number of early adopters in the automotive sector, e.g. Tesla. However for high voltage (>1.7 kV) power transmission, bipolar Silicon devices (IGBTs, GTOs) are more efficient - so the technology must presently be chosen relative to application. To remove this restriction, SiC power devices of all types can be additionally bolstered by SuperJunction (SJ) technology, improving the efficiencies of the material and fully ready to challenge Si technology. This proposal intends on developing new 6.5 kV SiC SJ materials and devices technology for the goal of increased power transmission. Current research in SiC SJ devices consists only of a handful of reports on single devices, whilst encouraging, the technology is still in its infancy. The UK has an opportunity to develop the technology from the ground up and become a serious international name. The major challenge being that SiC processing methods fall short of being able to mass-produce the superjunction material, with one method being expensive and complicated, another requiring very tight precision of parameters and the last compromising on current rating. Specifically here we propose to develop Trench Epitaxy (TE), which deposits crystalline materials in very high aspect ratio micro trenches. The deposition method is chemical vapour deposition (CVD), which is accepted as the industry gold standard of fast throughput, high quality materials production and so must be the method of choice when developing this technology. The challenges in developing TE lie in the transport of the gases to the bottom of the trenches to a) etch the material, b) condition it ready for deposition and c) fully refilling the trenches with modified material and d) ensuring the surface is returned to its previous state. The more complex challenges lie in the non-mutually exclusive chemical nature of the work, where a change in one parameter may change many more. Warwick currently houses the only industrial SiC CVD in the UK, has a dedicated SiC device fabrication cleanroom and many analytical tools so is the ideal place for the UK to enter this field with the view to contributing to the technology at the point of entry. The University of Warwick is a key member of EPSRC Centre for Power Electronics and is part of the £17M APC-12 ESCAPE (End-to-end Supply Chain development for Automotive Power Electronics) project which is developing a UK centred SiC production line, led by McLaren, so pathways exist of fully implementing TE SiC SJ technology after development.