Environmental Engineering Reference
In-Depth Information
industry partners. The FREEDM systems centre is headed by Prof. Alex Huang at
NCSU. It is because of these focused activities that power electronics has become an
important part of the twenty-first century power processing, and if this trend con-
tinues then it will contribute to the development of highly effective electric ESSs.
Power MOSFET technology continues to rule high frequency applications, and
recent developments in silicon carbide (SiC) have enabled continuous operation at
175
C and 10 kV [27]. With SiC MOSFET and junction barrier Schottky (JBS)
diode, a dc/dc converter capable of 25 kHz switching at 4 kV was demonstrated.
Beyond SiC is the recent emergence of commercially viable gallium nitride
(GaN) power semiconductors that offer even higher figures of merit [28]. In com-
ing years the high electron mobility transistor (HEMT) in GaN power semi-
conductors will enable an order of magnitude improvement over silicon devices.
GaN on silicon epitaxial processed devices are already capable of power processing
at 6 MHz and eventually 20-50 MHz with appropriate circuit topologies.
On the high power front for medium voltage systems, for example, Class 3
chargers for hybrid bus and PHEV and BEVs are typically silicon based IGBT, IGCT,
and now a new reverse conducting IGBT, RC-IGBT or as ABB refers to it, the BIGT, a
bimode IGBT [29]. The converter needed to interface a high power ultra-capacitor
pack of 100-150Wh with a PHEV or BEV lithium ion pack would require on the order
of 600 A, 1,200 V IGBT to meet the power, efficiency and switching frequency
requirements. For high power battery charging, the insulated gate commutated thyr-
istor (IGCT) that switches like a transistor but conducts like a thyristor and includes an
integrated diode could be used. However, since IGCT is a GTO derived device
switching frequencies over 1 kHz limit the package and inductor size gains. The newly
introduced BIGT promises performance gains in high power conversion of the same
order of magnitude that was realized when moving from soft punch through (SPT) to
enhanced SPT (SPT
+
) as shown in Figure 4.23. In the BIGT the diode is processed
5.5
SPT
5
4.5
SPT*
4
3.5
3
2.5
2
1.5
0
1,000
2,000
3,000
Voltage class (V)
4,000
5,000
6,000
7,000
Figure 4.23 IGBT conduction voltage versus rating with current density as
parameter SPT
+
devices for each voltage class are improved over
SPT base devices (used with permission, ABB [from Reference 29])
