1

Development and Demonstration

of CURENT Testbed Systems

Kai Sun

University of Tennessee, Knoxville

Presentation at i-PCGRID Workshop

March 30th, 2016

22

CURENT – NSF/DOE ERC

• Selected by National Science Foundation (NSF) and Department of

Energy (DOE) as one of four for funding (from a few hundred in

response to solicitation across all of Engineering).

• Base budget: ~$4M/year for 5-10 years. Other: $2-3M/year

• First and only ERC devoted to power system wide area controls.

• Partnership across four universities in the US and three international

partner schools. Many opportunities for collaborations.

• 50+ industry members have expressed commitment to join. Presently

have over 31 members.

• Center began Aug. 15th 2011; Third year renewal passed with

recommended funding through 2019.

33

• High penetration of renewable

energy sources

• Flexible DC and AC

transmission

• Accommodate load and

source variability, responsive

load

• Improved situational

awareness, ultra-wide-area

control

Multi-terminal HVDC

Ultra-Wide-Area Resilient Electric Energy Transmission Networks

44 4

55

Day Hour Minute Second Cycle

Device

Substation

Region

Balancing

Authority

Wide Area

Ultra-wide

Area

AGC

LTC

AVR

UFLS

SVC

Fixed Comp.

RAS

Schemes

Unit

CommitmentEconomic

Dispatch

PSS

HVDC

Device

Protection

Today’s Operations Some wide area and some fast but not both

Limited communication

Minimal sensing

Traditional uncoordinated controlsDistributed coordinated actuation with

extensive measurements

66

CURENT Testbeds: Participants and Research Projects

• Faculty members: Leon Tolbert, Fred Wang, Kevin Tomsovic, Yilu Liu, Fran Li,

Kai Sun, Hector Pulgar, Hairong Qi, Stella Sun, Jian Huang (UTK); Ali Abur (NEU);

Joe Chow & Jian Sun (RPI)

• Industry Participants: ABB, GE, Dominion, ORNL, ISO-NE, NYISO, Tektronix,

Vacon, OPAL-RT, National Instruments

• Projects:

1. Large-scale Testbed I – Virtual Grid Simulator with an EMCS (Energy

Management & Control System)

2. Large-scale Testbed II – US Grid Model Development

3. Hardware Testbed – Hardware-based Reconfigurable Grid Emulator

77

Large-scale Testbed (LTB-I): Virtual Grid Simulator

Real time software platform

continuously emulating grid operations

under small/large disturbances

• EMCS (Energy Management & Control

System) of the Future

• Develop virtual grid simulators (VGS)

on both academic (Matlab) and

commercial (ePhasorSim) platforms

• Both in-house and commercial (e-

terravision) control room functions

• Stream measurements in real time

• Demonstrate new measurement-based

stability and control algorithms

• GIS-based wide-area visualization

88

LTB-I Demo 1: MATLAB-based Platform

GIS

Visualization

Main Control Panel

SE Results

99

LTB-I Demo 2: Commercial Platform

ePHASORsim

• Interfaced through same

communication protocol

• Plug n’play functionality with other

software

• Real-time hardware platform

scalable to large systems

GIS

Visualization

1010

LTB-II: US Grid Model Development

Objective: Reduced-order models of US power grids for

demonstration of future interconnections with high renewable

penetration and for design and verification of wide-area control

methodologies.

Research focus:

• EI, WECC EROCT model reduction

• HVDC systems

Multi-Terminal HVDC and overlay HVDC systems in EI and WECC systems

Interconnection of WECC, EI and ERCOT via HVDC

Implementation of HVDC Overlay with renewables

1111

EI Model Reduction

• Started from a 30,000-bus

detailed EI model

• Used the DYNRED program to

obtain the reduced model

• Retained dominant dynamics as

monitored by FNET

• Performed dynamic simulation

on the reduced model and tested

against the full system response

1212

HVDC in EI System

• Used MT-HVDC system to deliver

renewable energy from Midwest

and off-shore wind to New York

and New England load areas

• Built and validated the MT VSC

HVDC model in PowerTech DSA

• Developed fast voltage control of

VSC

• Tested the transient performance

by simulations

Multi-terminal HVDC in New England

HVDC overlay of NPCC system

1313

WECC System Reduction

• Developed reduced model from the

original 179-bus system and

capture main system behaviors

• Added wind farms and

synchronous condensers

• Conducted N-1 contingency

analyses and tuned the system to

represent actual WECC transfer

limits of major paths

• Benchmarked voltage regulation

and frequency response to large

generator trips

1414

HVDC Overlay for WECC

• Delivering higher % of

renewable energy within

WECC

• Providing transmission

paths from wind power in

Montana and solar power in

Arizona to load centers in

the west coast

• Enabling the interconnection

with ERCOT

1515

Interconnection of WECC, EI and ERCOT via B2B HVDC

HVDC overlay grid for entire US (courtesy of MISO)

1616

Year 4~6

Generation II

• Reduced North American system model with >

50% penetration of renewables and HVDC

connections

• Extension of frequency & voltage control

models to North American grid and for

damping control and transient stability control

• Communication system modeling including

cyber attacks

• Scenario development for North American grid

Year 7~10

Generation III

• Large model of North American system

with >50% renewables and HVDC

connections

• Fully integrated system model of real

time communication, coordinated

control, actuators, monitoring and load

response

• Detailed scenarios for contingencies

and cyber attacks sufficient to

demonstrate resilience

LTB Demonstration Plan

1717

Hardware Testbed (HTB): Power Converter-based

Reconfigurable Grid EmulatorObjective: hardware implementation and emulation of a power grid that has interconnected generation

sources and loads with real measurement, communication, and control.

Research focus: emulated various grid scenarios with interconnected clusters of scaled-down

generators, loads, and energy storage.

WT II

DC

cab

le 1

DC

cab

le 2

DC cable 4

DC cable 3

VSC 4

1G1 5 6

G2 2

3

G3/WT III

1110

G44

97 8

L7 L9C7 C9

10 km25 km 25 km10 km

110 km 110 km

VSC 3

VS

C 2

VS

C 1

12 13

L12

L13

G14

14

110 k

m

66 k

m

33 km

WT I

Wind FarmWind Farm

Three-Area

System

Area 1Area 2

Area 3

Multi-Terminal

HVDC

1818

Hardware Testbed Architecture Generator I

Output

Inductors

Generator II

Load I

RectifierBuilding

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

Monitoring

Hardware Room

Visualization and Control Room

CTs, PTs FDR, PMU

ControlCAN Bus

Grid Operators (students)

1919

Development of the Emulators in HTB

Emulators

Generator Emulator Synchronous generator

Load Emulator

Induction machine

Constant impedance, constant current, and constant power load (ZIP)

Wind Emulator

Wind turbine with permanent magnetic synchronous generator (PMSG)

Wind turbine with doubly-fed induction generator (DFIG)

Solar Emulator Solar panel with two-stage PV inverter

Transmission Line Emulator

Back-to-back converter to emulate AC transmission lines

Energy Storage Emulator Compressed air, batteries, ultra-capacitors, and flywheels

RT Simulator Interface Emulate large scale power system in Real-time Simulator

HVDC Emulator Back-to-back converter to emulate DC transmission

Fault Emulator Emulate three-phase and line-to-line short circuit fault

Voltage Type

Current Type

Year 4

Accomplishment

2020

Multiple Simultaneous Control Functions

∆ω

∆P12

B1

ACE

s

KI

ACE Based AGC

Margin

Not

Enough

Transfer

Active

Power Limit

Monitoring

Reactive

Power

Support

Voltage Limit Monitoring and Control

PMU Based AGC

Economic Dispatch

Trajectory Generationfor Rotor

Angle

Trajectory Tracking for Rotor Angle,

Frequency and Acceleration

Global Control Level Local Control Level

PMU

Dispatch, Irradiance/Wind speed

Variable irradiance level, wind speed, and

load power consumption can be sent to

the emulators.

Different operating mode can

be selected: MPPT, inertia

emulation, voltage regulation

mode, etc.

State Estimation

Measurements

Pi, Qi, Pf, Qf, V, I, θij State

Estimator

V, θ

Topology

Processor

Different

Control Block

Network

Observability

Check

Various

Controllers

Local Area

Frequency

DeviationPSS

To Excitation

Power System Stabilizer

Frequency

Difference

Between AreasWADC

To Excitation

Wide-area Damping

Controller

Renewable Energy Mode

Selection

2121

HTB Demonstration Plan

Year 4~6

Generation II

• Implementation of sensing, monitoring,

actuation, and protection in real-time.

• Integrate with real-time simulation.

• Scenario demonstrations (multiple HVDC

links between wide areas, major tie line

and wind farm outage dynamic effects,

coordinated power flow control over large

distances, demonstrate system resilience

to attacks, energy storage impact).

Year 7~10

Generation III

• Coordinated high penetration renewable

control demonstration.

• Automatic real time reconfiguration for

selected outage scenarios.

• Ultra-wide-area coordinated real-time

communication and control on a system

hardened against coordinated cyber

attack.

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HTB Demo 1 – High Renewable Penetration

Scenario

• Replace one unit in Area 1 by an onshore wind farm;

together with offshore wind provided by HVDC,

system renewable penetration can reach 80%.

• Event triggered by a HVDC converter failure

Solution

• Frequency and voltage support from

onshore wind farm and the HVDC converters

• Curtailment and voltage mode control when necessary

• Integration of energy storage to further enable grid

support controls

Expected outcome

• System frequency and voltage

within acceptable ranges

0 2 4 6 8 10

0.65

0.7

0.75

0.8

0.85

0.9

0.95

0 2 4 6 8 1059.2

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

HTB scenario test results

2323

Scenario

• 50% renewable penetration

• One poorly damped inter-area oscillation mode between Area 1 and Area 2

Wide-area Damping Controller (WADC)

• Based on the measurement-driven model, which is identified by using ring-down data and ambient data.

• Controller input: frequency difference between Area 1 and Area 2

• Controller output added to exciter voltage reference of Generator 1

System disturbance

• Load change or line trip

HTB Demo 2 – Wide-area Damping Controller

0 5 10 15 20 25 30 35 40-3

-2

-1

0

1

2x 10

-3

t(s)

f 1 -

f4(p

.u.)

without control

with control

Frequency deviation Tie-line power, Bus 7-Bus 9

0 5 10 15 20 25 30 35 400.18

0.2

0.22

0.24

0.26

0.28

0.3

0.32

t(s)

PB

us7-B

us9 (

p.u

.)

without control

with control

0 2 4 6 8 10 12 14

0

5

10

time (s)

Dam

pin

g R

atio (

%)

without control

with control

Estimated damping ratio using Matrix Pencil

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HTB Demo 3 – Measurement-Based Voltage Stability Monitoring and Control for Load Areas

• Monitor the transfer margin of each tie lines by a measurement-based method using a multi-terminal network equivalent

• Demonstrating better accuracy than a traditional Thevenin equivalent method

Load Area

External

System

2525

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.

2626

RTDS Interface with HTB

Two RTDS

interfaces

with the HTB

G1

Area 1

G2 LD7

1 6

2

7HTB

G3

G4

310

4

9

Transmission

Line LD9

Area 2

Emulator 1

Emulator 2 Emulator 3

Emulator 4

Emulator 5Emulator 6

2.45 mH

1.2 mH

0.7 mH

2.5 mH

0.7 mH

0.7 mH10.7 mH

RTDS

Po

wer

Inte

rface

+ -

12

Dig

ital

Inte

rface

Po

wer

Inte

rface

+ -

12

Dig

ital

Inte

rface

12 133 mH

10 mH 6 mH

LD12 LD13

G5

152.5 mH

HVDC1 HVDC2

Area 3 in RTDS

Areas 1 & 2 in HTBRTDS Interface Attributes

• Expanding HTB to more than

40 buses

• Unique system that has both

control and power hardware

interface

2727

CURENT Research Thrusts