Events at Department of Energy Technology

PhD defence by Alex Buus Nielsen


20.09.2021 kl. 14.00 - 17.00


Alex Buus Nielsen, AAU Energy, will defend the thesis "Topology Optimization for High Efficiency Silicon Carbide Based Ground Power Unit"


Topology Optimization for High Efficiency Silicon Carbide Based Ground Power Unit


Alex Buus Nielsen


Professor Frede Blaabjerg


Associate Professor Pooya Davari, Bo Vork Nielsen (ITW GSE), Søren Dahl (ITW GSE)


Associate Professor Pooya Davari


Associate Professor Daniel-Ioan Stroe, Aalborg University, Denmark (Chairman)
Professor Yan-Fei Liu, Dept. of Electrical and Computer Engineering Queens University, Canada
Uffe Borup, Everfuel, Denmark


The modern society has been constantly developing towards a higher integration of electronic equipment and components.  This is seen not only in homeappliances  e.g.   computers,  smart  phones,  lighting,  and  electrical  vehicles,but  also  in  a  variety  of  industrial  applications  e.g.   motor  drives  and  tran-sitioning  from  hydraulic  to  electronic  systems.   The  primary  driver  for  thisdevelopment  is  the  advancement  in  power  semiconductors  technology  thatallow highly efficient, reliable, cheap, and compact power electronic converters.  The latest power semiconductor advancement is the production of market available Wide Band Gap (WBG) devices, especially Silicon Carbide (SiC)devices. These devices exhibit far superior performance compared to the current generation silicon based devices.  The superior performance allows for a potential even further increase in efficiency and power density, due to the highly reduced loss characteristics. A power electronics application area that is based on silicon devices is the Ground Power Unit (GPU) application. A GPU converts electrical power from a power source, typically the electrical grid, to aircrafts landed in the airports. By  using  a  GPU  to  supply  electrical  power  to  the  aircraft,  the  aircrafts  jet engines  can  be  idled  or  shut  off  which  improves  safety,  reduces  pollution,and reduces noise in the vicinity of the aircraft.  The main operation of the GPU  is  to  ensure  a  high  quality  and  robust  output  voltage,  such  that  the aircraft can operate sufficiently before take off. Because of the silicon based GPU, it has reached a technological optimization limit, where efficiency and power density improvement potentials are minor andwould  be  expensive.  Therefore,  the  technological  limits  of  the  GPU are addressed by investigating the potential of a SiC integration.  The main optimization potential of components in the GPU was identified as the passive components. With a potential high frequency operation of SiC devices, it could be possible to increase the power density of the GPU. To exploit the potential benefits of SiC devices a power electronics topology analysis has been conducted. The analysis both includes a system level and  converter  level  comparison. The  proposed  topologies  were  compared based on semiconductor efficiency, circuit and control complexity, passive filter size, electrical performance, and semiconductor cost.  The result showed that a SiC based solution could not only improve efficiency and power density by using a high frequency isolation power electronics converter, but simultaneously make use of simple and reliable converter topologies.  Furthermore,a  parallel  modular  GPU  system  has  been  proposed  due  to  the  benefits  of cheaper  and  more  efficient  SiC  converter  modules,  with  an  introduced  redundancy that allows for easier maintenance and reduced production time. Finally some of the selected SiC topologies have been designed and modelled  using  a  multi-objective  optimization  process. The  process  proposed magnetics, semiconductor, heat sink, capacitor, and auxiliary component models to investigate the trade-off between efficiency and power density with an elevated switching frequency. Similarly,using  experimentally  validated  models,  the  power  density  of  an  entire  SiC GPU inverter has been shown to potentially by increased by a factor of two compared to a Si IGBT inverter, with a simultaneous higher efficiency.

THE DEFENCE will be IN ENGLISH - all are welcome.



AAU Energy