Multi-Domain Virtual Prototyping Techniques for Wide-Bandgap Power Electronics

Power electronics is a key component in a low-carbon future, enabling energy-efficient conversion and control solutions for a wide variety of energy and transportation applications. Power electronics technology enables electric and hybrid vehicles, it is the underpinning technology for the next generation of fuel-efficient "More Electric" Aircraft, and is essential for the operation of high speed rail services. It allows connection of renewable energy sources to the national grid and allows us to more efficiently use the electricity distribution networks we have. In summary, it has the potential to allow almost all electrical devices to become smaller, lighter or more efficient.

Until recently, power electronic systems have been based around Silicon transistors but inherent limitations of these devices present a limit to how small, light and efficient a power electronic enabled system can be. Next generation power electronics will utilise Wide Bandgap (WBG) power transistors, made from materials such as Silicon Carbide (SiC) and Gallium Nitride (GaN) which are able to overcome the limitations of Silicon. This is achieved by having transistors that can operate at much higher frequencies, operate at higher voltages and higher temperatures, and dissipate less of the power they process as heat.

The problem is that our current understanding and experience of power electronic system design is derived from Silicon systems, and that the design of Silicon systems is less critical to achieving optimal performance. To fully exploit the potential of WBG based systems we must understand the challenges posed by the more extreme operating range of WBG devices, and tailor system designs accordingly. High frequency operation means that the electromagnetic design of systems is critical, to avoid unreliable power electronic systems and to prevent power electronic systems affecting other devices through electromagnetic emissions. High frequency operation also theoretically allows the reduction in size of passive filter components (inductors and capacitors) which can significantly reduce system size and weight (increased power density), however the behaviour of smaller passive components operating at higher frequencies is difficult to predict and they can suffer from thermal management problems. High power density power electronic systems, with WBG semiconductors able to operate at higher temperatures place increased thermal stresses on packaging and interconnection methods that were originally developed to deal with Silicon based systems, and this can adversely affect system reliability. An optimal WBG based system design must consider how component choice, system geometry and construction techniques affects each of these challenges, but as the challenges are coupled, any changes to a design to try to solve one problem can cause new problems in another area. Effects such as electromagnetic interference and reliability are also notoriously difficult to predict with extensive experience, and the behaviour of the wide-bandgap semiconductors themselves is different to their Silicon counterparts.

This research will develop the tools that power electronic system designers need to be able to design optimal WBG systems, right-first-time, on a computer - Virtual Prototyping. This will allow faster design times, as fewer physical prototypes must be built, and it will allow engineers with Silicon system experience to quickly develop high performance WBG systems. We will do this by developing mathematical techniques that can be applied to predict how a potential system will behave in the electromagnetic, thermal, mechanical, reliability and semiconductor domains. These techniques will then be combined into a proof-of-concept design tool that will be demonstrated on real wide-bandgap systems developed at the partner institutions, and through parallel work in the linked CA, RHM, and HI projects.

This project will contribute to the delivery of the underpinning research undertaken within the UK EPSRC Centre for Power Electronics which will reinforce the UK Power Electronics industry by providing it with the knowledge, tools and techniques required to capitalise on the emergence of wide-bandgap semiconductors.
The global power electronic market was estimated to be worth £135bn (2011), growing at a rate of 10% per year[1]. Within this, there is significant interest for the adoption of WBG devices with the market for these alone estimated to increase from $0.25bn in 2016 to $1.25bn in 2020[2]. Knowledge and tools produced by this project have the potential to enable UK industry to capitalise on this growth market and provide significant benefits to the UK economy.

Specific technical outputs include: the development of efficient simulation techniques suited to the multi-domain simulation of power electronics; demonstration of how these techniques can improve the performance of wide-bandgap systems; and an understanding of the multi-domain physics that underpins the successful operation of high frequency, high temperature, and high reliability power electronic systems. Potential beneficiaries of these outputs in the UK are:
- Power electronics system and converter manufacturers who want to realise the true benefits of wide-bandgap power electronic systems
- Producers of design and simulation software who are interested in understanding how novel simulation techniques could improve the performance of their software and how their existing software offerings could be tailored to the power electronics market
- Wider engineering industry who may be interested in how optimally designed wide-bandgap power electronics enhance the performance of their existing products (e.g. automotive or aerospace organisations)
- Ultimately the wider public who will benefit from the small, lighter, more reliable power electronic enabled devices that can result from wide-bandgap power electronic systems, optimally designed using virtual prototyping techniques.

This project will enable the design of power electronic systems that: allow efficient power conversion; enable a cleaner environment through use in electric/hybrid vehicles, rail, 'more electric' aircraft, and ship propulsion; facilitate the use of renewable energy sources and more efficient electricity distribution systems. The project will therefore benefit society by reducing greenhouse emissions and providing opportunity for meeting future CO2 targets.

As part of the Centre for Power Electronics, the project will provide a greater supply of young researchers, PhD students, and engineers and help to address the skills shortage in power electronics through embedding the generated knowledge and skills into undergraduate and postgraduate teaching, technical workshops, and industrial lectures.

This impact plan will be managed as an activity of the Hub of the Centre, through the Executive Management Team and the affiliated Industry Advisory Group as well as through the five topics via four routes:
1. Establish the Centre brand as a natural point of contact for power electronics expertise through active dissemination; build the public image of power electronics/engineering and its importance to society.
2. Promote the transfer of knowledge and IP gained from the research to the UK industrial community and stimulate new business activity.
3. Contribute to the development of relevant policy through engagement with national government, national and international funding bodies and professional societies.
4. Build collaborative links with leading academic groups and other relevant industrial organisations around the world.

[1] "Power Electronics: A Strategy for Success,", UK Government, October, 2011.
[2] R. Eden, "The World Market for Silicon Carbide & Gallium Nitride Power Semiconductors - 2016, IHS Technology," 2016.