Fred Wang EPIC 2018

Overview of Recent Power Electronics Research in CURENT: Fred Wang fred.wang@utk.edu Presentation at

13th Annual EPIC Pittsburgh, PA October 15, 2018

CURENT UTK at a Glance • CURENT was established in 2011 as a 10 year $40M US NSF/DOE Engineering Research Center, the first US DOE-NSF ERC and only one with a power system focus • CURENT involves four US institutions with about 25 faculty members and 130 graduate students • UTK is the lead institution with nine core faculty members in power systems and power electronics, four affiliated faculty, about 100 graduate students with mostly PhD students, a number of post docs, and undergraduate students • 36 industry and government partners • Close collaboration with Oak Ridge National Lab 2

Engineered Systems

CURENT Research Thrusts Testbeds Hardware Testbed

Barriers

Large Scale Testbed

Fundamental Knowledge

Enabling Technologies

Monitoring Modeling Control Situational Awareness & Visualization

Wide-area Measurements

Estimation Communication & Cybersecurity

Modeling Methodology

• • • •

System complexity Model validity Multi-scale Inter-operability

Actuation Barriers

Control Design & Implementation

Control Architecture Economics & Social Impact 3

System-level Actuation Functions

• Poor measurement design • Cyber security • Actuation & control limitation

• Barriers Actuator & Transmission Architecture

• Lack of wide-area control schemes • Measurement latency • Inflexible transmission systems

Power Electronics Research Application Focus Utility Grid and Alternative/Distributed Energy Systems

Transportation Power Systems

Technology Focus and Projects • Grid     

Power electronics converter based grid emulator HVDC converters and systems Low-cost, high reliability FACTS converters Grid support and interface with renewable energy sources and energy storage Microgrids & multi-converter system design and control

• WBG Application and Transportation  

 

Device: SiC & GaN characterization, driving, & protection Device module/phase-leg: online condition monitoring, adaptive dead-time setting & compensation, decoupled IPM, packaging, series/paralleling Converter: high-efficiency, high-density WBG converters for transportation, renewable, data center, medical applications Other converters and converter systems 5

Grid Emulator Testbed Architecture Hardware Room DC Bus

Short Distance Transmission Line Emulator

Generator I

Building Power

Rectifier

Long Distance Transmission Line Emulator

Generator II HVDC Load I

Cluster 1

Cluster n+1

Output Inductors

Cluster n+2

Cluster 2

Cluster m

g n ir ot i n o M

CTs, PTs

FDR, PMU

lo rt n o C

Cluster n

CAN Bus

Visualization and Control Room

Emulator Categories Developed

Multi-terminal HVDC System Demo AC Grid I

VSC 1

DC cable 3

DC cable 4

AC Grid II

DC cable 1 VSC 3

VSC 4

DC cable 2

VSC 2

Wind Farm I

Wind Farm II

Notional NPCC system with DC grid connected offshore wind

8 MT-HVDC testbed with HMI command panel

Implemented Renewable Energy Source Working Modes in HTB

1-9

Test Scenario – Inverter-Based HTB System Stability YB7L YB7R

Area 1 Zov1

+ − + −

G V Zov2 2 * clv 2 2

Z1-6 i2 (v2) Z2-6

G3 3 G V* i3 (v3) Zov3 clv 3 3 Z3-10 i4 (v4) Z9-10 * Z4-10 Z 4 ov4 Gclv 4V4 * G I i9 (v9) clc 9 9 G4 10

Z6-7

Gclc 7 I 7*

i7 (v7)

Yoc7 L7

ωc =1000 Hz Stable

Z7-9

Yoc9 L9

ωc =200 Hz Unstable

G2: i2a [20 A/div] L7: i7a [20 A/div] G4: i4a [20 A/div]

Current loop bandwidth ωc [Hz]

G V

1 6 i1 (v1)

Stable Unstable

+ −

* clv1 1

+ −

Area 2

1100 1000 900 800 700 600 500 400 300 200 100 0

L9: i9a [20 A/div] [t: 100 ms/div] 10

Stability boundary Experiment cases

100 200 300 400 500 600 700 800 900 1000 1100

Voltage-feedforward ωffv [Hz]

ARPA-E Project: Continuously Variable Series Reactor DC Controller

Magnetic Amplifier Controller

Smart and Flexible Microgrid Local protective devices

System control

Local controllers Normal open smart switch Normal closed smart switch

PCC

Microgrid central controller

PCC

Electrical network Communication and control network

PCC 13

Benchmark Study of SiC for Distribution Grid  Efficient, power-dense, and low cost converters  Enable direct grid-connection, eliminate LF transformer PV array  System-level functionalities  Enable new applications AC bus  

Asynchronous microgrid High % DER integration Medium voltage Grid

Wind Turbine Energy Storage System

DC bus

Normally-on Switchgear *

Normally-off Switchgear

Solid sate Breaker *

Loads

Diesel Generator

ve Power Filter CHP generator

* Switchgear and solid state breaker can be replaced by other equipment with same functions

Summary of Weight Comparison •

SiC-based NPC saves 86% weight @10 kHz and 87% weight @20 kHz • SiC-based MMC saves 65% weight @10 kHz and 66% weight @15 kHz 4000 3000

Weight (kg)

3500 2500 2000 1500 1000 500 0

Group1

Group2A Group2B Group3A Group3B

heatsink with device

Cap

Output filter

Bus bar

Housing

10000 9000 8000 7000 6000 5000 4000 3000 2000 1000 0

Group1

Group2A Group2B Group3A Group3B

heatsink with device Cap Output filter Bus bar Housing Transformer

w/ transformer

w/o transformer 15

â&#x20AC;˘

For grid-connected mode, interface converter can have similar functions as DER converters: APF, enhanced stability, LVRT For islanded mode, the SiC based MG side converter can function as stabilizer

FFT of PCC current

â&#x20AC;˘

System-level Functionalities of SiC-based Asynchronous Microgrid Interface Converter

Technology Focus and Projects • Grid     

• WBG Application and Transportation  

 

Challenges of WBG Converters

 Converter Level ― High frequency, EMI, performance, cost…  Module Level ― Dead-time setting and compensation, condition monitoring, IPM  Device Level ― Characterization, gate drive, device level protection 18

GaN Device Characterization

• •

Rg,ext J)

•

Performed comprehensive characterization of GaN Systems GS66508P including sweeps over voltage, current, junction temperature, and gate driver circuits Designed and implemented test procedure to isolate effects of Miller cross-talk in a phase leg, for total switching loss analysis Developed new technique for I-V alignment (deskew) that requires no additional fixtures or test setup Derived analytical model to explain significant increase in turn-on loss with elevated temperature, as well as the lack of a Miller plateau at turn-on 0

100

GaN Systems GS66508P (650 V e-mode)

5 10 15

Total Switching Loss (

•

40 0

Load current (A)

I-V Alignment Technique

10 kV SiC MOSFET Test • • •

Tested switching performance up to 7 kV dc-link voltage, from 25°C to 150°C Designed gate driver including short circuit protection and > 100 V/ns immunity 10 kV SiC MOSFET with Gate Driver 10 kV circuit breaker as protection of double pulse test platform vgs: 12.5 V/div

vds: 2.5 kV/div id: 12.5 A/div

di/dt = 0.6 A/ns

Esw=17.9 mJ

Measurement Equipment

Decoupling 10 kV SiC MOSFET Cap Hot Plate

dv/dt = 93.1 V/ns 50 ns/div

Switching Waveforms at 7 kV dc-link voltage, 100°C junction temperature 20

DC-link Cap Circuit Breaker

Double Pulse Test Platform

Intelligent Gate Drive for Fast Switching and Cross-talk Suppression ď ą Gate voltage and gate loop impedance are actively regulated under different switch states

Intelligent gate drive circuit

Control logic & 4 level gate voltage

Device Level Protection for WBG  Dedicated protection circuit based on desaturation techniques with < 200 ns response time

 Limited short-circuit withstand capability due to small chip area and high current density

Buffer Output

Gate Drive Input PWM

DESATURATION DETECTION

DssRsat1

Buffer Output Rg

Rsat2 Cblk

Vdesat Dblk

Rdg Mdg

Comparator

+ Vdesat_th

-5V

Logic Control

vds (200 V/div)

195 ns response time id (50 A/div) vgs (10 V/div) Protection Threshold:5 V t1

t2 t3

vdesat (5 V/div) t (200 ns/div)

Dead-time Setting & Compensation for WBG Power Electronics

ď ą Power loss decreases by 12% at full load and 18.2% at light load by adaptive dead-time regulation ď ą Gate assist circuits can be embedded into gate drive IC as well 23

Online Condition Monitoring for SiC Devices Capturing 3 SiC Timing Conditions

vds : 250 V/div

IL : 5 A/div

Junction Temperature Monitoring in real-time for SiC Devices

•

Capture signal: 2 V/div

•

vgs : 10 V/div

•

td_off

tvc toff

Incorporated an innovative online condition monitoring system into the intelligent gate driver for SiC devices. Turning “device-level” monitoring into “converter-level” improvements. Work is continuing to expand and dedicated to improve the performance of WBG devices in various applications.

Device Level Monitor

Converter Level Benefit

Detailed benefit

Turn-off Delay Time (td_off)

Junction Temperature Monitoring

Reliability and Lifetime Enhancement

Turn-off Time (toff)

Dead-Time Optimization

Power Loss Reduction

Voltage Commutation Time (tvc)

Dead-Time Compensation

Power Quality Enhancement

Impact of Motor & Cable on Drive Design ― Motor + cable (ton) ― DPT (ton or toff)* --- Motor + cable (toff) ― Motor (ton) --- Motor (toff) tsw (600 V/ 5 Ω)

tsw (pu)

Esw (pu)

― Motor + Cable (Esw) ― DPT (Esw)* Esw (600 V/ 5 Ω) ― Motor (Esw)

IL (A)

* Other data are normalized based on DPT

IL (A)

 Cooling system cannot be designed based on switching loss from typical DPT  Switching frequency and dead time cannot be set based on switching time from DPT 25

Auxiliary Network to Improve HF Impedance

ZL Auxiliary network

ď ą Insert an auxiliary network to increase high frequency impedance of induction motor 26

Switching Waveforms Comparisons

32% ↑ 1% ↑

42% ↑ 7% ↑ 1. DPT: double pulse tester with inductor load 2. IM-PC: pulse tester with induction motor + power cable 3. IM-PC-AN: pulse tester with 27 IM + PC + auxiliary network

100% ↑ 12.5% ↑

Low Parasitic SiC Module with Double-sided Cooling

Gen-II double-sided module

Gen-I double-sided module

ď&#x201A;§ Island design for vertical interconnection. ď&#x201A;§ Decoupling capacitors are embedded in the module. ď&#x201A;§ Laminated bus terminals are used for easy connection.

Simulation Experiment

Gen-II Design

đ?&#x2018;łđ?&#x2018;łđ?&#x2019;&#x2026;đ?&#x2019;&#x2026;đ?&#x2019;&#x2026;đ?&#x2019;&#x2026; of Gen-I module

đ?&#x2018;łđ?&#x2018;łđ?&#x2019;&#x2026;đ?&#x2019;&#x2026;đ?&#x2019;&#x2026;đ?&#x2019;&#x2026; of Gen-II module

6.59 nH

2.60 nH

6.03 nH

1.63 nH

WBG Device Based High Efficiency Power Supplies

Full Load Efficiency:

98.8%

Front end rectifier: 7.5 kW, 480 Vac to 400 Vdc SiC devices 29

96.6%

HV intermediate DC/DC converter: 300 W, 400 V to 12 V GaN devices 29

91.2%

87%

Point-of-load DC/DC converter: 200 W, 12 V to 1 V GaN devices (Auburn)

GaN Based Universal Battery Charger Vienna-type three-level PFC, 450 kHz A

+ C

Three-level dc-dc converter, 833 kHz 3-L Buck

3-L LLC K1

28 V

C -

ac-dc

dc-dc

EMI 30 filter

270V

Controller board

(TMSF28377D DSP)

Solar ADEPT â&#x20AC;¢ ARPA-E sponsored, Wolfspeed and Danfoss led 12.4 kV, 1MW direct-connected PV inverter based on 10 kV-SiC UPS

120VAC

PLC 24V PS Power supply

COMM

Fieldbus

DC/DC ENABLE LV INU ENABLE LV INU RAMP

12 cmd signals I/O Fieldbus 06 fdbk signals 8 analog ch

DSP Decimator

Interface? 12 cmd signals 06 fdbk signals 8 analog ch

Wizard 12 cmd signals 12 cmd signals 12 fdbk signals 12 fdbk signals 8 analog ch 8 analog ch 3 VCO fdbks for DCV 3 VCO fdbks for DCV

DSP Decimator

Common Control Bd

12 cmd signals 06 fdbk signals 8 analog ch

I/O

Power supply

Fieldbus I/O

Common Control Bd

Sigma/ delta

Power supplies

6kV

Q1 Q1

TX1

15mH

20mH

160nF

VBUS resistor divider

cable Gate drivers

Cap bleeder resistor

6kHz 50kW

LCL

CFB-A1

Designed for 10% current ripple

H1 HS

Q2 D2

Feedback VCOs

PEBB-B1 Feedbacks

Gate drivers

Power supplies

Feedbacks

Q1 Q1

Power supplies cable Gate drivers

5kHz 50kW

Q3 CFB-B1

1kV

6kV

30kHz 85kW

Feedback VCOs

PEBB-C1 Feedbacks

Gate drivers

Power supplies

Feedbacks

Q1 Q1

Power supplies cable Gate drivers

5kHz 50kW

Q3 CFB-C1

1kV 30kHz 85kW

6kV

Q2 D2

Feedback VCOs

PEBB-A2

Feedbacks

PV SubCombiner 12-24 Strings 72-144kW

Non-Isolated DC/DC Boost Converter with MPPT

PV SubCombiner 12-24 Strings 72-144kW

Non-Isolated DC/DC Boost Converter with MPPT

PV SubCombiner 12-24 Strings 72-144kW

Non-Isolated DC/DC Boost Converter with MPPT

PV SubCombiner 12-24 Strings 72-144kW

Non-Isolated DC/DC Boost Converter with MPPT

Q1 TX2

Power supplies cable Gate drivers

5kHz 50kW

6kV

Feedback VCOs

PEBB-B2

Feedbacks

Power supplies cable Gate drivers

5kHz 50kW

Q1 D1

6kV

Q2 D2

Feedback VCOs

PEBB-C2

Feedbacks

Q1 D1

Power supplies cable Gate drivers

5kHz 50kW

6kV

Power supplies

Optical interface

1kV 30kHz (SS) 85kW

15kV VCB

24V PS

[AMC1304L25]

Gate drivers

CLKs for Delta-Sigma ?

VBUS fdbk Delta-Sigma

PEBB-A1 Feedbacks

12.4kV +/-10%

AUX ISO I/O

CFB-A1 CFB-B1 CFB-C1

Fiber count per PEBB: (4) gate command (4) gate feedback (Concept gd format) (1) DC voltage feedback

Interface? 12 cmd signals 06 fdbk signals 8 analog ch

Grid Voltage Fbk

Sigma/ Delta

Medium Voltage PCS for Microgrid  The overall objective is to develop an asynchronous microgrid PCS module employing 10 kV SiC MOSFETs with > 10 kHz equivalent switching frequency to deliver at least 100 kW power at a required ac voltage level of 13.8 kV, achieving



Control interface PCS module controller

Sensors

Gate drives & protection

Sensors

Gate drives & protection

DC link

Filter

Thermal Management System

Sensors

Filter SiC based power conversion

SiC based power Power stage conversion

PCS module

Microgrid Interface 13.8 kV



Efficiency target of 98%; 95% with low/partial load (<30% loading) Volumetric density of 4 m3/MW, footprint of 3 m2/MW, and specific power of 15 kW/kg Sufficient bandwidth (voltage control bandwidth > 300 Hz and current control bandwidth > 1 kHz) for both the grid-facing and microgrid-facing functions

Grid Interface 13.8 kVac



DOE WBG Traineeship Program • $3 Million, 5-year DOE sponsorship – one of the only two awardees in the nation • Funds US Citizen Graduate students • Hands-on coursework and research leveraging WBG • Emphasizes internships with industry & national labs

Acknowledgements

This work was supported by the ERC Program of the National Science Foundation and DOE under NSF Award Number EEC1041877 and the CURENT Industry Partnership Program. Other government and industry sponsors are also acknowledged.

Thank You! 34