Abstract-Soft switching has the
potential of reducing switch stresses and of lowering the switching
losses as compared to hard switching. For this reason, several
soft switching topologies have been presented in the literature.
Each topology has some advantages. Their operation, however, requires
additional active and/or passive elements. This introduces additional
cost and complexity. To understand the effectiveness of the soft
switching technique, when applied to electric vehicle (EV) and
hybrid electric vehicle (HEV) systems, it may be necessary to
first evaluate their system requirements and performances. This
evaluation process would require knowledge of the vehicle dynamics.
The vehicle load requires a special torque-speed profile from
the drive train for minimum power ratings to meet the vehicle's
operational constraints such as, initial acceleration and gradability.
The selection of motor and its control for EV and HEV applications
is dictated mainly by this special torque-speed requirement. As
a consequence, this requirement will have a strong influence on
the converter operation. This paper makes an attempt to evaluate
EV and HEV running in both standard FTP75 city driving cycle and
highway driving cycle. The analysis will be carried out for several
most commonly used electric motors operating on the optimal torque-speed
profile. Special attention will be given to the converter losses.
Features of the soft switching will be evaluated in the context
of the dynamic vehicle power flow and the system losses, as well
as the power converter requirements. The relative significance
of soft switching for EV and HEV systems will then be established.
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