Reliability, Condition Monitoring and Health Management Technologies for WBG Power Modules

Lead Research Organisation: University of Warwick
Department Name: Sch of Engineering

Abstract

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.

Planned Impact

Renewable Energy Sector: This project is set to make significant impact in the renewable energy sector by accelerating the uptake of wide bandgap (WBG) technologies into grid connected power electronics. Historically, the electrical power system has had little or no power electronics since the 3-phase AC power transformer sufficed for AC power conversion and the bulk of electrical power was generated by an interconnection of synchronous generators concentrated in power stations. However, as the need to connect renewable power sources like off-shore windfarms and solar farms became imminent, power electronic converters started to play an increasingly important role in the power system. For the last few decades, silicon thyristor technology has been the work-horse for grid connected converters based on line-commutated current source topologies. More recently, silicon IGBTs in direct-bonded-copper (DBC) and pressure-packaging have become mainstreamed into voltage source converter topologies for high voltage direct current (HVDC) and Flexible Alternating Current Transmission System (FACTS) technologies. With silicon approaching its theoretical limits set by fundamental material properties, WBG devices have emerged with SiC set to displace silicon in medium/high voltage applications and GaN set to displace silicon in high frequency applications. One of the biggest obstacles to the uptake of WBG technologies has been its unknown reliability performance compared to silicon behind which there is decades of reliability data and experience. As the WBG devices are used more aggressively, industrial users, particularly grid connected converter operators, will become more concerned about on-line failure of power modules in the field. Unlike the information and communication technology sector where disruptive post silicon technologies are rapidly adopted, the severe consequences of on-line field failure in grid connected power electronics forces the industry to be much more conservative in adopting new technologies. The impact of this project will contribute to the de-risking of WBG technologies in grid connected converters by producing a condition monitoring and health management system to pre-empt catastrophic field failures. The idea is to run diagnostic tests on the power module on-line and report to the user on the health status of the power devices and packaging. This will give imminent warning of reliability problems and converter failure.
Electric Transportation Sector: The electrification of transportation is seen as critical to the effort to de-carbonise industrial societies. This project will impact the electric transportation sector by accelerating the penetration of WBG devices into converter applications where efficiency, power density and reliability are key performance metrics. Power electronics is crucial to electric transportation since the electric drive virtually replaces the internal combustion engine as the actuation mechanism. The efficiency, power density and reliability of the power converter has been point of significant academic and industrial research whether in automotive, rail, aerospace or marine propulsion applications. High frequency switching, high power density and high temperature cooling are seen as fundamental to improving electric transportation systems, however, this must not come at the expense of reduced reliability. Condition monitoring and health management can bridge this gap and unleash the potential of WBG semiconductors in electric transportation.
Medium Voltage Industrial Drives: A very significant proportion of electrical power consumed in industrial societies is done so medium voltage industrial drives in a myriad of applications. These drives are typically based on silicon IGBT technologies and the potential to move to SiC technology is widely recognised. This project will improve the performance and reliability of medium voltage electric drives.

Publications

10 25 50
 
Description This project has the targeted objectives of further understanding the reliability concerns in SiC and GaN power devices and how to improve the prospects of their implementation through condition monitoring. Since starting the project, we have discovered further electrical reliability problems in SiC power devices and novel ways of characterizing them. These additional reliability problems make condition monitoring more difficult since the condition monitoring system is itself affected by the reliability of the devices. We have also discovered new techniques of characterizing threshold voltage drift in GaN power devices. As part of the project, we have developed gate driver techniques for characterizing these reliability issues however, implementing these in an industrial context remains very challenging. The technology readiness level of the proposed solution is still very low.
Exploitation Route Further industrial engagement is required to raise the TRL level of the research
Sectors Electronics,Energy,Transport

 
Description Characterization of field stop IGBTs 
Organisation Bourns
Country United Kingdom 
Sector Private 
PI Contribution Developing expertise for the measurement and characterization of the latest generation field stop IGBTs
Collaborator Contribution 10,000 GBP for purchasing conusmmables required for developing the test set up
Impact A test and characterization system for the latest generation power transistors
Start Year 2018
 
Description Design collaboration with Nidec Control Techniques 
Organisation Control Techniques Drives Ltd
Country United Kingdom 
Sector Private 
PI Contribution Two contracts for a co-design collaboration between Nidec Control Techniques and the University have been carried out.
Collaborator Contribution There was a financial contribution (confidential), and exchange of valuable expertise.
Impact Outcomes Knowledge and design expertise transferred to company. Application and product design expertise transferred to university. Research and development roadmap of the company has been influenced.
Start Year 2019
 
Description Quietening Waveforms Technical Workshop 2020 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Engineering Directors, Chief Engineers, and other senior decision makers from 10 Power Electronics companies (global corporations with a strong UK presence, or UK companies) took part in an interactive workshop with 4 sessions. The first, on high-bandwidth measurement of high-performance power electronics had been requested at the previous workshop. The other sessions opened up research questions faced by the research groups at Imperial, Edinburgh, Strathclyde, and Bristol. The sessions contained on average 5 questions, and industry and academia discussed possible methods and pitfalls for about 2/3 of the time.
The workshop was ended with a discussion on how universities can enhance their support of industry with courses, knowledge exchange and other types of interaction. The attendees requested a follow-up workshop, and a course for graduate engineers. Two representatives from EPSRC were present at the workshop.

Outcomes:
This workshop furthered the common understanding between industry and university research groups, and led to new relationships between engineers and researchers.
The Quietening Waveforms project benefited from the wealth of experience of the industry attendees, who were very active and forthcoming with advice and ideas. Generally everyone felt they had learned new things, and were supportive of continuing this workshop series in the same discussion-based format. The EPSRC reps commented on the collaborative nature and openness of discussion of this event.
Year(s) Of Engagement Activity 2020
 
Description Reliability and Condition Monitoring workshop for WBG devices 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Industrial collaborations have arisen from the workshop
Academic collaborations have arisen from the workshop
Year(s) Of Engagement Activity 2018
URL http://www.powerelectronics.ac.uk/events/event-records/wide-bandgap-device-reliability-and-condition...