IEEE Power Electronics Magazine Compendium - March 2018 - 89

Table
1. TIPS AFEC loss distribution at 3-kHz,
-
100-kVa, 13.8-kV grid at 22-kV dc bus.
loss component

UPF Mode

statcoM Mode

Total switching loss (W)
Total conduction loss (W)
Total loss (W)
Efficiency (%)

440
102
542
99.46

370
79.5
449.5
99.55

Table
2. TIPS DABC loss distribution at 10 kHz,
-
100 kVA at 22-kV dc bus to 800-V dc bus operation.
loss component

Value

MV-side switching loss (W)
MV-side conduction loss (W)
LV-side switching loss (W)
LV-side conduction loss (W)
HF transformer loss (W)
Total loss (W)
Efficiency (%)

601. 86
84.06
86.34
511.05
390
1,673.31
98.33

-Table 3. TIPS LV converter loss distribution

at 20-kHz, 100-kVA, and 800-V dc bus.
loss component

UPF

statcoM

One converter switching loss (W)
One converter conduction loss (W)
One converter total loss (W)
Total loss for three converters (W)
Efficiency (%)

99
246
345
1035
98.97

105
197
302
906
99.04

- Table 4. TIPS overall loss distribution.

loss component

FEc
lV side
(UPF) DaBc (UPF)

Switching loss (W)
440
688.2
Conduction loss (W)
102
595.1
HF transformer loss (W)
390
Total loss (W)
542 1,673.3
Efficiency (%)
99.46 98.33

297
738
1,035
98.97

total loss
1,425.2
1,435.1
390
3,250.3
96.75

Figure 15 shows the TIPS system experimental test setup
in the laboratory.

TIPS Loss Analysis
The power loss in each of the three stages of the TIPS is
calculated from Piecewise Linear Electrical Circuit Simulation thermal simulations based on experimentally measured loss data of the 15-kV SiC IGBT, 1,200 V SiC MOSFET,
and HF transformer. The loss is calculated for a 100-kVA
TIPS system. Tables 1-3 summarize this loss information
for each stage. The total loss of the TIPS is given in Table 4.
The reverse recovery loss of the 10-kV SiC JBS diode is
assumed to be negligible.

Conclusions
The foremost advantage of the 15-kV SiC IGBT is that it
enables simplified converter topologies for MV applications.
This feature is exploited by the proposed three-phase all-SiC
SST, the TIPS system, with a simple three-level topology for
13.8-kV MV grid interface. This article highlights the characteristics of the 15-kV SiC IGBT, MV isolated gate driver,
AFEC, DABC, LV converters, and their associated controls
for TIPS system demonstration. The multistage modular
structure of the TIPS system enabled the testing of individual
phases up to 10 kV, 7.5 kW before integrating them into the
overall closed-loop system. The MV gate driver was evaluated up to 11 kV, with dv/dt of over 100 kV/ns to handle the
high-stress conditions imposed by fast switching 15-kV SiC
IGBTs. The design issues of the LCL filter for the MV gridtied AFEC as well as the control techniques for multistage
converter integration are presented. The importance of lowcapacitance design of the isolation HF transformers in
DABC is emphasized based on the MV experimental results.
The design methods and considerations presented in
this article serve as guidelines for development of MV SiCbased power-conversion systems, which have the potential
to play a vital role in next-generation distribution power
systems control and operation, MV motor drives for many
applications, and MV grid-tied converters for renewable
energy integration.
At this time, the 15-kV SiC IGBT used in the TIPS system
is experimental and not commercially available. With future
commercialization of HV SiC devices, more industries
focusing on grid-connected power electronics will develop
commercial SSTs applied to distributed renewable energy
integration, MV motor drives, MV traction applications, MV
shipboard power systems, disaster-recovery transformers,
and many other applications.

About the Authors
Krishna Mainali (kmainal@ncsu.edu) received his B.E.
degree in electrical and electronics engineering from the
National Institute of Technology, Karnataka, India, in 2002
and his M.Eng. and Ph.D. degrees from the Department of
Electrical and Computer Engineering, National University of
Singapore (NUS) in 2005 and 2011, respectively. From 2008
to 2011, he was a member of the teaching staff at NUS.
From 2011 to 2013, he worked as a research scientist at the
Institute of Microelectronics, A*STAR, Singapore. His current research interests include electromagnetic compatibility in power electronics, solid-state transformers, and renewable energy applications. He is currently working as a postdoctorate researcher at the Future Renewable Electrical
Energy Delivery and Management Systems Center, North
Carolina State University, Raleigh.
Awneesh Tripathi (aktripat@ncsu.edu) earned his
B.Tech. degree in electrical engineering from Harcourt Butler Technological Institute, Kanpur, India, in 2006 and his
M.E. degree in electrical engineering from the Indian Institute of Science, Bangalore, India, in 2008. He worked at
September 2015

z IEEE PowEr ElEctronIcs MagazInE

Table of Contents for the Digital Edition of IEEE Power Electronics Magazine Compendium - March 2018