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Annual Meeting
North Carolina State University
Project PI: Subhashish Bhattacharya
January 17-19-2017
December 8 2015
1
Role in WBG Technology
Transformerless Intelligent Power Substation
Wolfspeed 10kV SiC MOSFET Characterization
High voltage isolated DC-DC power supply
Intelligent Gate Driver
2
Project Objectives
• Design, develop and validate a 15 kV isolated gate driver
(GD) for 10kV SiC MOSFET .
• GD to operate in the range of 10-20kHz.
• Integrated diagnostics and protection features.
• Develop test beds to validate the GD functioning in
various converter topologies
• Team comprises of Post Doc, PhD students with
previous experience in gate drive, MV converter designs,
implementation, tests and validation (ARPA-E project on
15kV SiC IGBT and TIPS System), 3 new PhD students
and 2 hourly students.
3
Accomplishments and Outcomes
• The current technological readiness level is 3.
– Analytical and experimental critical function and
proof of concept.
• Barriers to further maturity
– Packaging
– Testing methods and circuits
– Insulation levels and dielectric requirements
– HV Isolated power supply
4
Summary of Basic Gate Driver Spec.
Specification
Turn-on Voltage
Turn-off Voltage
Supply Input Voltage
Switching Frequency
Turn-on Gate Resistance
Turn-off Gate Resistance
Isolation Voltage
dv/dt capability
Isolation Transformer Coupling
Capacitance
5
Value
18 V -> 20V
-5 V
9-10 V
Up to 20 kHz
10-33 Ω
10-15 Ω
Up to 15 kV
> 50 kV/µs
< 5 pF (1- 100 MHz)
Gate Driver High Frequency Transformer
: Nano-crystalline core
 Cp (Coupling Capacitance) of 1.4 pF
 Lm (Magnetizing Inductance) of 1.1 mH
Isolation test (≥ 15 kV )
of DC power supply
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Isolation Test Standard
 Motor Drives Applications – IEC 61800-5-1 (Not Available)
 Information Extracted – Two Sources*,**
 Insulation Testing – Three Tests (AC, Impulse and Partial
Discharge)
System Voltage
(kV RMS)
AC Voltage Test
(kV RMS)
Impulse Voltage
(kV Peak)
6
16
53
14
36.4
108
20
54
130
35
91
200
* R. Steiner, P. K. Steimer, F. Krismer and J. W. Kolar, "Contactless energy transmission for an
isolated 100W gate driver supply of a medium voltage converter," Industrial Electronics, 2009.
IECON '09. 35th Annual Conference of IEEE, Porto, 2009, pp. 302-307.
** http://www.ti.com/lit/wp/slyy080/slyy080.pdf
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Isolation Test Standard
AC Voltage Test – Temporary AC Overvoltage
 As per Standard – For 5 Sec No Discharge
 Performed – For 5 Minutes To Verify Robustness (12 kV RMS, 60 Hz
Hipotronics Hypotester HD 115A Limitation)
1)
2) Impulse Voltage Test – Switching and Lighting Impulses
 Very High Voltage (53 kV Peak) – No Lab Facilities
 With External Partner – Maybe In Future
3) Partial Discharge Test – Partial Discharge During Working State
 Not Required* – Low Voltage Across Solid Insulation as Majority
Voltage Across Air Gap
 Performed – 15 kV DC Test
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Test Setup
 Circuit Diagram
 Physical Setup
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Prototype 1
 Ferrite Toroid with Kapton Tape
 AC and DC Test – No Discharge
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Prototype 2
 Amorphous Core with PCB Windings
 AC (6kV) and DC (12 kV) Test – Discharge
11
Prototype 3
 Double Galvanic Isolation with Ferrite Cores
 AC and DC Test – No Discharge
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Prototype 4
 Potting Immersed
 AC and DC Test – No Discharge
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Prototype 5
 Nano-Crystalline Core
 AC and DC Test – No Discharge
14
Remarks
 Measurement of Coupling Capacitance Through AC Test
– Not Accurate
 Low AC Current Sensitivity of Hipotester and NonAvailability of Very Low Current Probe
 Future Task – Insight into Effective Coupling Capacitance
at Higher Voltages for Common Mode Noise Suppression
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Existing Design
Old design
Ferrite Toroid with
Kapton Tape
3.5pF at 10MHz
Isolation transformer inter-winding coupling
capacitance
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Gate Driver Isolation Transformers
Cores for isolation
 Amorphous core
 Nano-crystalline core
 Ferrite cores
 Double galvanic isolation
Windings
 24 AWG varnished wire
 10 turns on primary, 11 and 5 turns on secondaries
 PCB windings
Insulation
 Three layers of nomex (0.38mm) and five layers of kapton
(>30kV)
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Intelligent gate driver
6kV, 10A, Rg_initial = 50Ω, Active circuit with 4.7Rg
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Parameters/Functions
Isolation Voltage
Isolation Capacitance
Drive Voltages
Value [Units]
20 kV
< 1.5 pF
+20/ − 5 V
Optical Communication
Vds(on), Ids , T
Shoot-through Protection
Protections
Active Gating
Vgs Controlled
Local OT, OC, ST
Clock Timed
Validation of IMGD: Short-circuit test
10kV SiC MOSFET
IMGD
1kV/div
10V/div
50 A/div
•
•
•
•
•
10kV/10A SiC MOSFET
(golden pack module from
CREE, Inc)
Short circuit voltage: 3kV
Short circuit time: 5μs
Turn-off current : 150 A
Time to current zero: 2.5μs
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Characterizing Wolfspeed 10 kV SiC
MOSFET Modules
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Wolfspeed Modules
Wolfspeed Power Module
10kV, 10A SiC MOSFET
Wolfspeed Halfbridge Module
Double pulse circuit
with Wolfspeed copack module and a
SiC-JBS diode
SiC
JBS
diode
4mH
inductors
Wolfspeed Copack Module
Version 1
gate driver
APEI
copack
module
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Wolfspeed Modules – double pulse test Tj = 220C
Turn-on at 6kV/10A
Turn-off at 6kV/10A
• Turn-on
• dV/dt: 59 kV/µs
• Eon: 9.6 mJ
• Turn-off
• dV/dt: 32.7 kV/µs
• Eon: 2.25 mJ
22
Wolfspeed Modules – double pulse test Tj = 1500C
Turn-on at 6kV/10A
Turn-off at 6kV/10A
• Turn-on
• dV/dt: 68 kV/µs
• Eon: 10.0 mJ
• Turn-off
• dV/dt: 30.4 kV/µs
• Eon: 2.15 mJ
23
Experimental results for high
fundamental frequency converter
3kV DC, 900 V ac rms, 20 kHz switching frequency
Load currents
Converter switching line
voltage
1.8 kW load for 60 Hz fundamental
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Load currents (2 A/div)
Converter switching line voltage
(5 kV/div)
1.45 kW load for 1000 Hz fundamental
Experimental results series connection of two
10kV SiC MOSFET devices with RC snubber
Balanced static & dynamic voltage sharing between two 10kV SiC MOSFETs at 12kV
DC bus voltage with RC snubber.
[Ch3: Top device VGS (20 V/div); Ch2: Total voltage (1 kV/div); Ch4: Bottom device VDS (1 kV/div);
Math1: Ch2-Ch4: Top device VDS (1 kV/div) Ch1: Bottom device current: ID(5 A/div);]
Pathway to Market
• Benchmarking against available 6.5kV Si-IGBT commercial gate
drivers
• Insulation and dielectric material specification and development for
power supply isolation transformer
• Protocols for optical and electrical communications to enable
diagnostics and prognostics
• Packaging of module and gate-driver with adequate isolation
• EMI/EMC qualification and validation in MV converter
• Identify industry partner for commercialization of HV GD for WBG
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devices from 3.3kV to 15kV
Broader Impact on the WBG Community
 HV IGD enables SiC based Medium Voltage converters which are more
efficient compared to Si based MV converters
 Increases reliability of these high power density converters – by providing
diagnostics and prognostics by the IGD
 Market segments impacted: High Speed Machines, PV, Wind Energy
 Easily adaptable to other SiC devices as 6.5kV JFET, 15kV IGBT
 Reduction in the size, weight and volume of Si based MV drives with gears for
compressor applications with SiC based MV converters with high fundamental
frequency
 With large scale production, the cost will come down since the electricity
saving is significant
 Potential for Job Creation, Economic impact
 Workforce Development and Education – training large no. students
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Aspirations for PowerAmerica
• How would you like to see the Institute evolve
– As a leader in defining best manufacturing practices in the field of WBG devices
and associated peripherals
– As a body setting up standards for product qualifications and procedures
– Spearheading skill-development for continued leadership in the area
• Most valuable role the Institute can play
– Aggregate associated industries and universities under one umbrella for
achieving compatibility between different products in terms of qualifications, test
procedures and even interfaces between products.
• What you will do to help the Institute grow
– Put an effort towards early commercialization of products like gate drivers
required for WBG industry
– Educate and spark interest in the young undergraduate and graduate students
towards WBG technology.
• Unique opportunities/gaps the Institute can exploit
– Thermal challenges in utilizing these devices for higher power and voltage
– Impact and mitigation of EMI/EMC issues arising due to high slew rates
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– High frequency and high temperature magnetics
Publications
• Sachin Madhusoodhanan, Krishna Mainali, Awneesh Tripathi, Kasunaidu Vechalapu,
Subhashish Bhattacharya; "Medium Voltage (≥ 2.3 kV) High Frequency ThreePhase Two-Level Converter Design and Demonstration using 10 kV SiC
MOSFETs for High Speed Motor Drive Applications", accepted for publication in
proceedings of APEC 2016, California, March 2016.
• Krishna Mainali, Sachin Madhusoodhanan, Awneesh Tripathi, Kasunaidu Vechalapu,
Ankan De, Subhashish Bhattacharya; "Design and Evaluation of Isolated Gate
Driver Power Supply for Medium Voltage Converter Applications", accepted for
publication in proceedings of APEC 2016, California, March 2016.
• Awneesh Tripathi, Krishna Mainali, Sachin Madhusoodhanan, Akshat Yadav,
Kasunaidu Vechalapu, Subhashish Bhattacharya; "A MV Intelligent Gate Driver for
15kV SiC IGBT and 10kV SiC MOSFET", accepted for publication in proceedings of
APEC 2016, California, March 2016
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Other related publications
• Vechalapu, K.; Tripathi, A.; Mainali, K.; Baliga, B.J.; Bhattacharya, S., "Soft switching characterization of 15 kV SiC n-IGBT
and performance evaluation for high power converter applications," in Energy Conversion Congress and Exposition
(ECCE), 2015 IEEE , vol., no., pp.4151-4158, 20-24 Sept. 2015
• Vechalapu, K.; Bhattacharya, S.; Van Brunt, E.; Sei-Hyung Ryu; Grider, D.; Palmour, J.W., "Comparative evaluation of 15 kV
SiC MOSFET and 15 kV SiC IGBT for medium voltage converter under same dv/dt conditions," in Energy Conversion
Congress and Exposition (ECCE), 2015 IEEE , vol., no., pp.927-934, 20-24 Sept. 2015
• Vechalapu, K.; Bhattacharya, S.; Aleoiza, E., "Performance evaluation of series connected 1700V SiC MOSFET devices,"
in Wide Bandgap Power Devices and Applications (WiPDA), 2015 IEEE 3rd Workshop on , vol., no., pp.184-191, 2-4 Nov. 2015
• Madhusoodhanan, S.; Mainali, K.; Tripathi, A.; Patel, D.; Kadavelugu, A.; Bhattacharya, S.; Hatua, K., "Performance
evaluation of 15 kV SiC IGBT based medium voltage grid connected three-phase three-level NPC converter," in Energy
Conversion Congress and Exposition (ECCE), 2015 IEEE , vol., no., pp.3710-3717, 20-24 Sept. 2015
• Tripathi, A.; Mainali, K.; Madhusoodhanan, S.; Patel, D.; Kadavelugu, A.; Hazra, S.; Bhattacharya, S.; Hatua, K., "MVDC
microgrids enabled by 15kV SiC IGBT based flexible three phase dual active bridge isolated DC-DC converter,"
in Energy Conversion Congress and Exposition (ECCE), 2015 IEEE , vol., no., pp.5708-5715, 20-24 Sept. 2015
• Madhusoodhanan, S.; Tripathi, A.; Patel, D.; Mainali, K.; Kadavelugu, A.; Hazra, S.; Bhattacharya, S.; Hatua, K., "Solid-State
Transformer and MV Grid Tie Applications Enabled by 15 kV SiC IGBTs and 10 kV SiC MOSFETs Based Multilevel
Converters," in Industry Applications, IEEE Transactions on , vol.51, no.4, pp.3343-3360, July-Aug. 2015
• Kadavelugu, A.; Mainali, K.; Patel, D.; Madhusoodhanan, S.; Tripathi, A.; Hatua, K.; Bhattacharya, S.; Ryu, S.-H.; Grider, D.;
Leslie, S., "Medium voltage power converter design and demonstration using 15 kV SiC N-IGBTs," in Applied Power
Electronics Conference and Exposition (APEC), 2015 IEEE , vol., no., pp.1396-1403, 15-19 March 2015
• Tripathi, A.K.; Mainali, K.; Patel, D.C.; Kadavelugu, A.; Hazra, S.; Bhattacharya, S.; Hatua, K., "Design Considerations of a
15-kV SiC IGBT-Based Medium-Voltage High-Frequency Isolated DC–DC Converter," in Industry Applications, IEEE
Transactions on , vol.51, no.4, pp.3284-3294, July-Aug. 2015
• Madhusoodhanan, S.; Tripathi, A.; Mainali, K.; Patel, D.; Kadavelugu, A.; Bhattacharya, S., "Distributed Energy Storage
Device integration with three phase distribution grid using a Transformerless Intelligent Power Substation," in Applied
Power Electronics Conference and Exposition (APEC), 2015 IEEE , vol., no., pp.670-677, 15-19 March 2015
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Project title: Medium Voltage Gate Drives
Objectives: To develop a Medium Voltage Gate Drives to enable fast
switching of 10 kV SiC power transistors with minimum isolation
voltage of 15 kV, should include desaturation protection, junction
temperature protection and low capacitance power supply
Major Milestones: Fully functional Medium Voltage Gate Drives
Major Equipment Acquisition:
Deliverables: Demonstration of Medium Voltage Gate Drives
operation in boost-buck circuit at 6kV dc, Reports and presentations
WBG Technology Impact





Enables SiC based Medium Voltage converters which
are highly efficient compared to Si based converters
Increases reliability of these high power density
converters - by providing diagnostics and prognostics by
the IGD
Market segments impacted: High Speed Machines, PV,
Wind Energy
Time frame for commercialization: 2 years
Easily adaptable to other SiC devices such as 6.5kV
JFET, 15kV IGBT
PowerAmerica
TPOC: Subhashish Bhattacharya
Email: [email protected] Phone: 919-744-1428 (cell)
More WBG Impact and Additional impacts




Reduction in the weight and volume of Si based
MV drives using gears for compressor
applications
With large scale production, the cost will come
down since the electricity saving is significant
Potential for Job Creation, Economic impact
Workforce Development and Education if
applicable
Jan 19th, 2017