Evaluation of silicon carbide power electronic components for hybrid and electric vehicles

Abstract

continuously growing penetration of electric (EV) and hybrid electric (HEV) vehicles,  reinforced  by  the  need  for  increased  energy  savings,  drove  the  research  towards  power  electronic  components  with  superior  material  properties.  Wide-bandgap  (WBG)  power  semiconductor materials such as Silicon Carbide (SiC) offer significant improvements in power  converter’s performance as they allow higher operating voltage, higher switching  frequency  and higher maximum operating temperature. As a consequence, it is expected to be utilized  in traction DC-DC converters where high efficiency, high power density and lower cooling  requirements are desired while, simultaneously, achieving significa nt reductions in the total  weight and volume of the powertrain. The improved features introduced by SiC MOSFETs on DC-DC converter topologies  employed  in  EVs  and  HEVs  are  investigated  and  experimentally  verified.  Initially,  a  non-isolated  half-bridge  DC-DC converter  topology  is  designed  with  operating  principles  that  correspond to a converter found on energy management systems of HEVs or fuel cell vehicles.  The operating principle of the converter is presented and the bi-directional flow of energy  aspect  is explained.  Subsequently,  the  design  has  been  modelled  and  evaluated  on  a  simulation software that considered the operating stages of the converter by also accounting  for the gate driving circuit and the predefined cooling requirements. Finally, a test prototype  was  built  in  custom-made  printed  circuit  board  (PCB)  and  validated  in  terms  of  reliable  operation and circuit efficiency. The benefits from utilizing SiC power semiconductors are presented under constant  24 V loading conditions and 80 kHz switching  frequency. A constant voltage was maintained  through automatically modulating the gate driving signal, whereas an efficiency of around  96% was achieved due to fast switching times introduced by SiC MOSFETs and thus the reduced  switching  losses.  The  efficie ncy  of  the  system  is  dependable  on  the  MOSFET  operating performance and therefore an exposure of the transistors in environmental conditions was  considered for each individual SiC MOSFET provided by different suppliers.  Significant attention has been paid to rapid temperature change, extreme humidity,  mechanical vibration and accelerated ageing tests that aim to address possible degradation  and defects in the SiC material. The effect of the testing process was examined in component-level, by assessing the electrical characteristics of the SiC MOSFETs, as well as in converter-level by evaluating potential efficiency reductions and operating flaws. Finally, verification of  the  conditions  under  which  each  individual  change  occurred  is  of  equal  importance  for  prospective improvements in the transistor and converter alike.

Original document

The different versions of the original document can be found in:

• http://hdl.handle.net/2117/123213 under the license http://creativecommons.org/licenses/by-nc-nd/3.0/es/