IEEE Power Electronics Magazine - June 2022 - 46

1.5 kV
Input Voltage
1:6/8
Turns
Ratio
7-8 kV
Output Voltage per
Module
N Modules
Connected in Series
PV/Wind +
Battery Bank
Generation
(1 kV-1.5 kV)
HVDC
Transmission
(500 kV-750 kV)
Up to 1.7 kV
Si IGBTs or
SiC MOSFETs
20 kHz to
40 kHz
Transformer
10 kV
SiC MOSFETs
FIG 8 Proposed design of bidirectional soft switching resonant LVDC-HVDC converter.
transformer-coupled topology hereon. As seen in Figure 8,
the LVDC (1-2 kV) power generated from green sources
undergoes an initial high frequency switching stage in the
order of a few kHz. Since this stage faces a LVDC/MVDC
input, the switching transistors can be Si IGBTs or SiC
transistors depending on the trade study between cost
and performance as both transistor types have breakdown
voltages up to 1.7 kV. The generated high frequency
MVDC output acts as the primary input for a high-frequency
transformer (SST) which has superior characteristics
in terms of weight, volume, and modularity over the
conventional line-frequency transformer. High-frequency
suitable magnetic core materials, such as nanocrystalline
core, are utilized for this application. The turns ratio can
also be designed according to the input voltage from the
generation side. The turns ratio cannot be manipulated to
achieve HVDC outputs due to the breakdown voltage limitations
of the output power transistors. Taking 10 kV SiC
MOSFET as an example, the output must be less than 10 kV
(~7-8 kV). However, the output power electronics module
can be replicated in a series arrangement to achieve the
desired HVDC output. The number of SiC power electronics
output modules N is directly correlated to the required
HVDC output. The modular proposed model will face
some challenges at the power electronics level and system
level. The details about the power electronics-based
challenges like inadequacy of a single device to interface
HVDC, switching losses at HVDC operation, device-level
isolation and control, high-frequency transformer tradeoff
design between insulation and thermal management; and
system level challenges like reliability issues, system isolation
and dc protection, and system complexity have been
extensively discussed [28] and some of them are still ongoing
research topics.
46 IEEE POWER ELECTRONICS MAGAZINE z June 2022
Conclusions
Electrification of almost everything by green sustainable
electric power is an economic solution to address climate
emergency. A large amount of green electric dc power generated
by photovoltaics and/or wind turbines and stored in
batteries is wasted in current ac electricity infrastructure.
Based on silicon carbide power electronics, we propose
HVDC transmission of bulk power by dc-dc power converters.
Power electronics with higher performance, higher reliability,
and low-cost power has the potential to provide
transformative transformation of power transmission, distribution,
and utilization.
About the Authors
Rajendra Singh (srajend@clemson.edu) is D. Houser
Banks professor in the Holcombe Department of Electrical
and Computer Engineering and Automotive Engineering
at Clemson University, Clemson, South Carolina, USA.
He is also the Executive Director of Electrification of
Transportation minority program. With proven success in
operations, project/program leadership, R&D, product/
process commercialization, and start-ups, Dr. Singh is a
leading technologist. He is fellow of IEEE, SPIE, ASM and
AAAS. He has received a number of national and international
awards. In 2014, he was honored by US President
Barack Obama as a White House " Champion of Change
for Solar Deployment " for his leadership in advancing
solar energy with photovoltaics technology. In 2019, he
received Hind Rattan Award presented by Bibek Debroy,
chairman of the Economic Advisory Council to Prime
Minister Narendra Modi.
Prahaladh Paniyil (ppaniyi@clemson.edu) is a PhD
candidate in the Holcombe Department of Electrical and
Computer Engineering at Clemson University, Clemson, SC,
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