Environmental Engineering Reference
In-Depth Information
Main SW
Curr sen
Curr
sen
+
=
14V
.
K
1
HV
=
dc-dc conv
Battery
=
U
V
MCU
+
IGN
SW
C'md's
M-G
14V
CAN
W
Gnd
Inverter-
motor-
controller
Traction
inverter
CAN
comm
Rps
Fault
mgmt
Temperature
Figure 6.18 Hybrid propulsion system functional diagram
the wide voltage swing of HEV battery systems. This is clear, because HEVs have
no standard HV battery or ESS standard operating voltage. Voltages for the HV
ESS now range from 201 to 244 V, 278 to 330 V and higher. The half-H, bidir-
ectional, dc/dc converter of non-isolated design is recommended as the converter of
choice for hybrid vehicles. This fact is clear from the fact that Toyota THS-II
systems have implemented a bidirectional converter in Prius II, Prius III and Lexus
products since 2004 as the interface between the HV battery and the 650 V floating
bus in their single mode eCVT architecture. Schupbach and Balda [14] discuss
about how to develop a specific design for a 35 kW converter to manage a hybri-
dized battery consisting of battery plus ultra-capacitor and show that such a com-
bination can minimize overall ESS volume and mass while delivering same or
better performance.
In some cases the bidirectional dc/dc converter may require isolation between
the HV and LV ports. Walter and De Doncker [15] describe a 300 to 42 V dual
active bridge, isolated, bidirectional converter. In this power MOSFET design, the
switches operate at 100 kHz, minimizing the transformer and filter element size.
Other investigators are implementing dc/dc converters with SiC diodes in place of
the MOSFET internal diode for improved efficiency. Over the near term, the trend
will be to use SiC power switching elements for high temperature (200
C) and
high frequency of hundreds of kilohertz.
6.8 Thermal design
The limitations to power electronics beyond voltage and current stress are thermal
dissipation and heat removal. Thermal modelling of power electronic systems is
focused on removal of heat from the semiconductor chip via its thermal stack to a
cooling medium. In hybrid propulsion systems today,
liquid cooling via an
