Abstract:
Hybrid electric vehicles (HEV’s) are a very important part of today’s
transportation system as they are bridging the gap between fully electric vehicles and
conventional internal combustion vehicles (ICV’s). They have much higher efficiencies
and lower emissions than ICV’s, while still having the ability to travel long range and
refuel conveniently. The advantages offered by HEV’s have caused several major
automobile manufacturers to develop HEV’s for public use and they are also being
developed for military use. With the necessity of high performance vehicles the need
arises for investigations on the converter generated harmonics which may become
increasingly important. This is because there are several problems associated with
harmonics including, high frequency interference, additional heat, mechanical stresses
and audible noise (vibration) that may shorten the life of the equipment involved in
HEV’s and lower their reliability.
This thesis models, predicts, and mitigates the dc bus harmonics that are
reflected by power electronic converters. It includes the investigation of dc bus
harmonics through sine-triangle pulse width modulation (SPWM) analytical derivations (open and closed form) and switching function approaches, as well as verification
through Simulink and PSpice simulations, which all showed very good correlation. The
resulting dc bus harmonics were also compared against MIL-STD-461 distortion limits.
In the case where MIL-STD-461 was not met, mitigation techniques involved
increasing the size of the dc bus capacitor. For further comparison, the space vector
PWM (SVM) switching function approach has also been implemented in the
simulations. Next, an experimental verification is presented and compared with a
Simulink simulation which operates at approximately the same parameters. The final
section of this report presents an overall comparison of the output line-to-line voltage
harmonics, and the dc currents, for all of the above approaches.
