16 September 2016

NCSU's SiC-based inverter achieves 12.1kW/L, close to DOE's target of 13.4kW/L by 2020

Researchers at the Future Renewable Electric Energy Distribution and Management (FREEDM) Systems Center at North Carolina State University (NCSU) have used off-the-shelf silicon carbide (SiC)-based components to develop an inverter with greater efficiency in a smaller, lighter package that could improve the fuel-efficiency and range of hybrid and electric vehicles (HEV/EV).

"Our silicon carbide prototype inverter can transfer 99% of energy to the motor, which is about 2% higher than the best silicon-based inverters under normal conditions," says FREEDM Center director Iqbal Husain, ABB Distinguished Professor of Electrical and Computer Engineering at NC State. "Equally important, the silicon carbide inverters can be smaller and lighter than their silicon counterparts, further improving the range of electric vehicles," adds Husain, who co-authored two papers related to the work. "New advances we've made in inverter components should allow us to make the inverters even smaller."

A major factor limiting public acceptance of electric vehicles is 'range anxiety' (fear of not being able to travel very far or getting stuck at the side of the road). The new SiC-based inverter is able to convey 12.1 kilowatts of power per liter (kW/L) – close to the US Department of Energy (DOE) goal of developing inverters that can achieve 13.4kW/L by 2020. In comparison, a 2010 electric vehicle could achieve only 4.1kW/L. "Conventional, silicon-based inverters have likely improved since 2010, but they're still nowhere near 12.1kW/L," Husain notes. "But, frankly, we are pretty sure that we can improve further on the energy density that we've shown with this prototype," he adds. That's because the new inverter prototype was made using off-the-shelf SiC components, and FREEDM researchers have recently made new, ultra-high-density SiC power components that they expect will allow them to get closer to the DOE's 13.4kW/L target once it's incorporated into next-generation inverters.

In addition, the design of the new power component is more effective at dissipating heat than previous versions. This could allow the creation of air-cooled inverters, eliminating the need for bulky (and heavy) liquid cooling systems. "We predict that we'll be able to make an air-cooled inverter up to 35kW using the new module, for use in motorcycles, hybrid vehicles and scooters," Husain says. "And it will boost energy density even when used with liquid cooling systems in more powerful vehicles."

The existing SiC inverter prototype was designed to go up to 55kW – the sort of power you'd see in a hybrid vehicle. The researchers are now in the process of scaling it up to 100kW – akin to what you'd see in a fully electric vehicle – using off-the-shelf components. They are also in the process of developing inverters that make use of the new, ultra-high-density SiC power component that they developed on-site.

A paper on the inverter 'Design Methodology for a Planarized High Power Density EV/HEV Traction Drive using SiC Power Modules' is being presented at the IEEE Energy Conversion Congress and Exposition (ECCE) in Milwaukee (18-22 September). Lead author is Ph.D. student Dhrubo Rahman, and co-authors are Ph.D. students Adam Morgan, Yang Xu and Rui Gao, plus research professors Wensong Yu and Douglas Hopkins of NC State's Department of Electrical and Computer Engineering, along with Husain.

A paper on the new ultra-high-density SiC power component 'Development of an Ultra-high Density Power Chip on Bus Module' is also being presented. Lead author is Yang Xu, and co-authors are Yu, Husain and Hopkins, as well as Harvey West, a research professor in NC State's Edward P. Fitts Department of Industrial and Systems Engineering.

The research was performed with the support of the PowerAmerica Institute, a public-private research initiative housed at NC State and funded by the DOE's Office of Energy Efficiency and Renewable Energy under award number DE-EE0006521. FREEDM, a National Science Foundation (NSF) Engineering Research Center (ERC), aims to facilitate the development and implementation of new renewable electric-energy technologies.

See related items:

ABB contributing $2.5m as partner in five-year Next Generation Power Electronics Innovation Institute

US DOE selects NCSU to lead $140m Next Generation Power Electronics Innovation Institute

Tags: Power electronics SiC

Visit: www.ncsu.edu/power