Research and Education on Power Electronics for Power Systems Fred - - PowerPoint PPT Presentation

Research and Education on Power Electronics for Power Systems

Chicago, IL October 31, 2019

Fred Wang fred.wang@utk.edu

NSF Workshop on Power Electronics- enabled Operation of Power Systems

CURENT at a Glance

• CURENT was established in 2011 as a 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 26 faculty members

and 130 graduate students

• UTK is the lead institution with 10 core faculty members in power

systems and power electronics (5 each), and >100 graduate students in power systems and power electronics (about half and half)

• About 40 industry and government members
• Courses
• 5 undergraduate courses (1 junior level, 4 senior level)
• ~15 graduate courses

2

CURENT Vision

• A nation-wide transmission grid that is fully monitored and dynamically controlled for high efficiency, high

reliability, low cost, better accommodation of renewable sources, full utilization of storage, and responsive load.

• A new generation of electric power and energy systems engineering leaders with a global perspective coming

from diverse backgrounds. Power Grid

WAMS

FDR PMU

PSS Generator

Storage HVDC Wind Farm FACTS Solar Farm Responsive Load Communication

Wide Area Control of Power Grid

Measurement & Monitoring Communication Actuation

3

CURENT Research Roadmap

Year 1~3 Generation I

Regional grids with >20% renewable (wind, solar), and grid architecture to include HVDC lines System scenarios demonstrating a variety of seasonal and daily

• perating conditions

Sufficient monitoring to provide measurements for full network

• bservability and robustness against

contingencies, bad topology or measurement data Closed-loop non-local frequency and voltage control using PMU measurements Renewable energy sources and responsive loads to participate in frequency and voltage control

Year 4~6 Generation II

Reduced interconnected EI, WECC and ERCOT system, with >50% renewable (wind, solar) and balance of other clean energy sources (hydro, gas, nuclear) Grid architecture to include UHV DC lines connecting with regional multi-terminal DC grids, and increased power flow controllers System scenarios demonstrating complete seasonal and daily operating conditions and associated contingencies, including weather related events on wind and solar Full PMU monitoring at transmission level with some monitoring of loads Fully integrated PMU based closed-loop frequency, voltage and oscillation damping control systems, and adaptive RAS schemes, including renewables, energy storage, and load as resources

Year 7~10 Generation III

Fully integrated North American system with >50% energy (>80% instantaneous) inverter based renewable resources (wind, solar) and balance of conventional (hydro, gas, nuclear) Grid architecture to include UHV DC super- grid and interconnecting overlay AC grid and FACTS devices Controllable loads (converter loads, EV, responsive) and storage for grid support Fully monitored at transmission level (PMUs, temperature, etc.) and extensive monitoring of

• f distribution system

Closed loop control using wide area monitoring across all time scales and demonstrating full use of transmission capacity and rights-of-way Automated system restoration from outages

4

Needs, Challenges, and Opportunities for Grid Power Electronics

5

Emerging System Needs

• High % of renewable energy sources; Energy storage
• Power electronics interfaced loads (often CPL)
• New types of grids (e.g. DC, microgrids)

Challenges and needs for Power Electronics

• Converter cost, reliability, size, and grid compliance
• Grid support functions
• Knowledge on system interactions and coordination

Opportunities

• New power electronics technologies including WBG technologies
• New system modeling, analysis, design, and control techniques
• New advances in communication, control, and data analytics
• Education

Continuous Variable Series Reactor

6

Full-rated CVSR Prototype DC Controller

Benchmark SiC Impact on Grid Power Electronics

7

Si b dG N b d 20 40 60 80 100 120 140 160 180

Cost ($)

GaN-Based PV Inverter

42 cm 15 cm

Filters Power stage 32%

Thermal Devices

Line filter EMI filter

GaN-based Si-based

8

System Level Benefits of SiC-Based Converter

1MW PV array 200 kW BESS 400 kW critical Load PCC switch

AC bus DC bus

Medium voltage Grid 200 kW CHP 600 kW non-critical Load

FFT of PCC current Si-based solution SiC-based solution Configuration of MV microgrid 1 kHz

9

Grid Emulator Hardware Testbed

Generator I Output Inductors Generator II Load I Rectifier Building Power DC Bus Short Distance Transmission Line Emulator

Cluster 1 Cluster 2 Cluster n Cluster n+1

Long Distance Transmission Line Emulator HVDC

Cluster n+2 Cluster m

M

• n

i t

• r

i n g

Hardware Room Visualization and Control Room

CTs, PTs FDR, PMU

C

• n

t r

• l

CAN Bus

Real three-phase power flow with inverters emulating various generation, load, storage, ac or dc transmission lines Actual control, measurement (CTs, PTs, PMUs) communication, cyber physical infrastructure

10

Test Scenario – Inverter-Based HTB System Stability

* 9 9 clc

G I Yoc9 Zov1

* 1 1 clv

G V Z1-6 Zov2 Z2-6

* 2 2 clv

G V Z6-7 Z7-9 Z9-10 Zov3 Zov4

* 3 3 clv

G V

* 4 4 clv

G V Yoc7

* 7 7 clc

G I Z3-10 Z4-10 6 7 9 10 YB7R YB7L G1 G2 L7 L9 G3 G4

+ − + − + − + −

i1 (v1) i2 (v2) i7 (v7) i9 (v9) i3 (v3) i4 (v4) 1 2 3 4 Area 1 Area 2 100 200 300 400 500 600 700 800 900 1000 1100 100 200 300 400 500 600 700 800 900 1000 1100

Voltage-feedforward ωffv [Hz] Current loop bandwidth ωc [Hz] Stable Unstable Stability boundary Experiment cases ωc =1000 Hz ωc =200 Hz Stable Unstable G2: i2a [20 A/div] [t: 100 ms/div] L7: i7a [20 A/div] G4: i4a [20 A/div] L9: i9a [20 A/div]

11

Test Scenario – Inverter-Based HTB System Stability

12

Grid Support Function Implementation & Testing in HTB

13

2 4 6 8 10 0.65 0.7 0.75 0.8 0.85 0.9 0.95 2 4 6 8 10 59.2 59.4 59.6 59.8 60 60.2

Wind Turbine Active Power (p.u.) Area Frequency (Hz) Time (s)

MPPT with inertia emulation MPPT Base case with generator Voltage mode with storage Voltage mode

Renewable energy sources working modes implemented Frequency response evaluation Operation under grid fault

Virtual Synchronous Generator (VSG) Control for Renewable Integration

Current exceeds limit after fault Load/Fault current VSG current Without current limit Current exceeds limit during fault Unstable Stable Stable 10s/div 50A/div

79 79.5 80 80.5 81 81.5 82 82.5

• 3
• 2
• 1

1 2 3

Time (s) Output Current (p.u.)

VSG Output Current w/o Limitation

There could be current excursions during or after a fault With limit and control Load/Fault current VSG current With limit no control Without current limit Unstable Stable Stable With limit and control With limit no control

Experimental result in HTB two area system

14

Power Electronics Interfaced Load Models

EV charger active power consumption:

DC/DC Load bus EV charger Remote bus

Vmbus, fbus

PLL

vd, vq id, iq

Modeling algorithm Detailed EMT model Equivalent TS model

EV charger modeling principle in TS simulator

15

Small-signal Stability Analysis and Design of DC Grids

10 0 10 1 10 2 10 3 10 4 20 40 60 80

Magnitude/dB DC impedance models of MMC

10 0 10 1 10 2 10 3 10 4

Frequency/Hz

• 100

100 200

Phase/deg

Circuit-based Simualtion Model I Model II Proposed Model

vdc ^ 2Larm 3 2Rarm 3 idc ^

• GcirVdcref idc

^

vdc 2Larm 3 2Rarm 3 idc 6Csub N Larm 2 Rarm 2 Cac ua ub uc ia ib ic

vdc 2Larm 3 2Rarm 3 idc ddcNVCsub ^ ^ ^ DdcNvCsub ^

Model I: no submodule capacitor voltage dynamics Model II: no circulating current control dynamics Proposed model: consider both submodule capacitor and circulating current dynamics Experimental setup Simulation results vs model results

MMC

CPL

16

Smart and Flexible Microgrid with Low-cost Open Source Controller

Field Test Location

G1 G2 G4 PV Wind turbine

Load 1 Load 2 Distribution line Load 4

BESS

Critical Load

Load 3 Power electronic converter Load 5 Load 6 Load 7 Normally closed switch Normally open switch SW1 SW2 SW3 SW4 SW5 SW6 SW7 SW8 SW9 SW10 SW11 SW12 SW13 SW14 Load 8 Load 9

G3

Load 10 SW15

17

Microgrid Controller HTB Test – Resynchronization Process

18

SiC-based Multifunctional Power Conditioning System (PCS) for Asynchronous Microgrid

• Develop asynchronous microgrid PCS module employing

10 kV SiC MOSFETs with > 10 kHz equivalent switching frequency and grid support functions

• 100 kVA/13.8 kV three-phase four-wire PCS DC/AC

converter built and tested at nominal AC output.

• Grid functions of the PCS, including low/high

voltage/frequency ride through, faults, unbalance load support, grid stabilizer, etc., validated in HTB. 100 kVA/13.8 kV Three-phase PCS converter Three-phase PCS testing at 13.8 kVac

PV array Wind Turbine Energy Storage System Backup Generator Loads Grid side switchgear

AC bus DC bus

Medium voltage Grid Active Power Filter Wind Turbine PV array CHP Microgrid side switchgear Microgrid PCS

19

CURENT Graduate Education

Hardware Experiment Demo Simulation Software Hands-on Project Learn to Use Tools in the Mechanical Shop 100 kW Drive Building & Testing DOE WBG Trainees

• Students with system view,

joint power system & power electronics knowledge

• Training of team work,

communication and technical skills

20

Closing Remarks

• It is a golden age for power electronics for power systems
• Technologies like WBG power semiconductors offer additional
• pportunities
• Need to look at converters and beyond
• Collaboration between power electronics and power systems

disciplines is essential

• Education is a key

21

Acknowledgements

This work was supported primarily by the ERC Program of the National Science Foundation and DOE under NSF Award Number EEC-1041877 and the CURENT Industry Partnership Program. Other US government and industrial sponsors of CURENT research are also gratefully acknowledged.

22