The proposed research will investigate the role that advanced power semiconductor module design can play in improving the efficiency and increasing the capacity of Voltage Source, HVDC converters. Growing use of HVDC for integration of renewable energy sources and transnational electricity transmission is driving development HVDC technologies. Within Europe there are over 20 HVDC schemes currently planned and under construction most of which will employ new IGBT based Voltage Source Converter (VSC) technology. The development of new multi-level converters greatly raised DC operating voltages in VSC converters and improved their performance. Despite these significant advances, there are still strong drivers to raise both capacity and efficiency. To date multi-level HVDC typically utilises high voltage power semiconductor modules originally designed for other applications. At projected deployment rates, VSC-HVDC is likely to become one of the key markets for high voltage power. The size of this potential market justifies the development of a new power semiconductor switch, specifically designed around the needs of multi-level VSC converters. Such a power switch will be a composite of high capacity multi-device module and an associated intelligent gate drive which can optimise module performance in multi-level VSC systems. It is proposed that such techniques can provide significant gains in both converter capacities and efficiency at a reduced cost.

This project proposes a paradigm shift in the operational management and use of power converters that entails active reliability management. This involves predicting failure and managing the remaining useable life of the power converter. Power electronic converters are indispensable to modern civilisation. They are responsible for electrical power conversion for a range of applications that span the few watts for portable hand-held electronics to several gigawatts for entire electrical power networks. Over the past few decades, the need for industrial decarbonisation has intensified the research into more efficient and reliable power electronic devices, components and converters. This is because power electronic converters are required for integrating renewable energy sources (solar, wind, tidal etc.) into the electrical system. Furthermore, electric transportation, which is seen as critical for reducing green-house emissions, relies very heavily on power electronics. Hybrid and full electric vehicles require power converters to control the traction machine, likewise, electric trains require power converters. Marine propulsion has also adopted the electric paradigm with the gas driven turbine replaced by a converter driven electrical motor. However, as power converters are driven at increasingly higher power densities, several reliability concerns have been recognised. The power converters are comprised of power modules, which in turn are comprised of switching power semiconductor devices in an electrically isolating but thermally conducting package. The reliability of the power semiconductor device and its mechanical interconnects has been intensely investigated by industrial and academic researchers over the last decade. Silicon devices have been the principal technology in power electronics for the last few decades however, silicon carbide and gallium nitride devices have emerged as viable alternatives. These new devices are referred to as wide bandgap devices because they have energy bandgaps larger than that of silicon. The simply means that they can withstand more energy thereby increasing the efficiency of power conversion. The reliability of these WBG semiconductors is increasingly becoming a very important topic since these new devices are gaining increasing market penetration. In applications with high failure costs, for example, automotive traction, aerospace and grid connected converters, the uptake of new technology is slow. By developing technologies that can improve the reliability of these new devices and monitor their health on-line, the uptake of new WBG power modules is very significantly de-risked. This project aims to do just this, by providing a condition monitoring and health management platform for WBG based power electronic modules.

In pursuit of Carbon net-zero, it is imperative to develop technologies that enhance the efficiency and reliability of energy conversion, e.g. in drivetrain and rapid chargers of electric vehicles (EVs). To put this into context, the larger battery size (i.e. 350 kWh at 800 V & 440 A for higher consumption) and long-range driving nature of heavy-duty EVs mandate ubiquitous access to extremely fast chargers at 350 kW for financially justifiable charging delays. These are proposed to directly connect to 11 kV feeders by high-frequency solid-state-transformers (SST), needing energy-dense fast power modules. Literature indicates that the emergence of wide-bandgap semiconductor devices, especially Silicon Carbide devices, enables us to deliver ultra-efficient reliable converters that deliver the next leap. Wide-bandgap power electronics is, however, currently being slowed down due to issues such as high dV/dt, common-mode interference and degradations. This means the full potential of wide-bandgap devices is still far from being obtained. The IEEE International Technology Roadmap for Wide-Bandgap Power Semiconductors (ITRW) has indicated that to unlock this potential, these limitations must be broken-through by 2028. As the UK is leading toward automotive electrification with a ban on the sale of new petrol & diesel engines by 2030, the UK needs to develop this technology locally, and earlier than this, to remain a global competitor in 'driving the electric revolution'. Research on SiC devices has shown that they are prone to progressive degradations, with a 'memory' effect that leads to a drift of electrothermal parameters away from the datasheet values. This can lead to failures in long-term operations. Nevertheless, it is demonstrated that under certain conditions the devices can recover to close to the initial state, if the devices are subjected to specific electrical and thermal conditions. This proposal, in a nutshell, aims to take advantage of these findings to explore ways of controlling and reversing degradation in devices using non-contact sensors which feed information to smart, active gate drivers, which, in turn, control the recovery of the power devices. To this end, this New Investigator Award project aims to make the power electronic core of these power converters responsive to operating conditions and functional degradations. This will be achieved by closing the loop between detection of change in SiC devices and how devices are controlled via their gates. This would permit SiC devices to be operated safely at higher switching speeds and thus efficiencies, than current datasheet limits allow. This is because datasheet nominal values are conservative in order to take every situation into account, whereas new situational awareness will allow these limits to be safely exceeded when appropriate. This is so important, particularly in the case of SiC power conversion, because whilst it is successfully taking over from silicon, it is also known that the potential performance of SiC is over an order higher than today's systems. Being able to safely break through these nominal limitations will reduce converter volume in cars and aircraft 2x or more, and bring a similar reduction in power loss in wind and solar power generation. Perhaps most importantly, it will reduce operational risk, by changing to safer driving modes as devices age or overheat. For example, this will reduce the cost of offshore wind power generation by generating more power at a lower risk of damage, and allow maintenance to be pre-empted. In the future, responsive power conversion with awareness of operating conditions and degradation could allow electric vehicles to detect the onset of drive failure, and activate a safe mode to get people home.