discrete control

Discrete Stability Controls for Transient and Oscillatory Stability

Douglas Wilson, Natheer Al-Ashwal (Psymetrix, UK)

Hallgrimur Halldorsson (Landsnet, Iceland)

Stephen Boroczky (AEMO, Australia)

24th July 2013

IEEE GM Discrete Control - 23/07/2013 - P 2

Introduction

Introduction

Oscillations

Transients

Conclusions

Qestions

Addressing dynamics issues

Constraint relief and security

Observing and controlling

Roadmap to Real-Time Stability Actions

7

15

22

2

Psymetrix & Alstom WAMS Activities

Advanced Phasor

Framework

• Data Management

• Analysis Tools

• Visualisation

Phasor

Applications

• Reliability

• Constraint Relief

• Dynamic Performance

• Renewables Integration

• Wide-Area Control &

Protection

Consulting

Services

• WAMS Deployment

• Dynamics & Control

• Operations & Planning

Guidance

• Power System Analysis

IEEE GM Discrete Control - 23/07/2013 - P 3

2012/13 Distribution:

Wind control; microgrid

1999 National Grid:

Security Constraint relief

Global Activities

Addressing Power System Challenges

2009 Energinet.dk: Renewable

integration, oscillations

2006 Iceland: PSS tuning,

Islanding Defence, Model

2009 Colombia: Frequency

stability, governor tuning

1995 Scottish Power: 1st

install, constraint relief

2000 Powerlink/AEMO: Synchronising

QND / NSW, constraint relief

2011 Eskom: Large WAMS, EMS integration (4,200 phasors)

2011 Manitoba:

SVC-POD tuning

WECC:

300+ PMUs,

CC integration

Short-Term Voltage Stability & Voltage Rise

Long-Term Voltage Stability

Oscillatory Stability

Frequency Stability

Local & Differential Fault Protection

Transient Stability

N-x Transient / Area Angular Stability

Thermal Limits

Phasor-based Wide Area Control

P5

15 minutes Operator Dispatch

Human-in-the-Loop

3-15 seconds Automated

Dispatch

200-600ms

Phasor Primed 16-200ms

Equipment

Protection

0.6-3s

Phasor Triggered

Guided Operator Response

Automated Control Response

Phasor-based Wide Area Control Control Room EMS/DMS/WAMS Protection

Pre-contingency operations

IEEE GM Discrete Control - 23/07/2013 - P 5

Measuring Dynamic Response

SCADA

WAMS

4 sec SCADA:

apparently small change

PMU data shows much

larger frequency swing and

poorly damped oscillations

WAMS Accurate time-

alignment, hence phase

displacement, is key to

identifying sources of

oscillation problems

WAMS shows grid

dynamic response,

hence use in transient &

oscillation applications

IEEE GM Discrete Control - 23/07/2013 - P 6

Oscillation Constraint Relief and Security

Introduction

Oscillations

Transients

Conclusions

Questions

Addressing dynamics issues

Constraint relief and security

Observing and controlling

Roadmap to Real-Time Stability Actions

7

15

22

2

IEEE GM Discrete Control - 23/07/2013 - P 7

• Australia – 3 damping constraints, ∑488MW, depending PhasorPoint

• Iceland – network procedures address oscillation risk (ring split)

• Colombia – Thermal / hydro dispatch constraint for frequency stability

• UK – oscillation security warning & operational guidance

Control-room Oscillation Management

Examples of WAMS-based oscillation management

Australia

3 Oscillation

Constraints

+128MW

+160MW +200MW

AREA 1

AREA 2

• Uncertainty in model limit

• Use margin if well damped

• Reduce limit if poorly damped

IEEE GM Discrete Control - 23/07/2013 - P 8

Examples of Control-Room Implementations

Presentation title - 23/07/2013 - P 9

Landsnet, Iceland WAMS mapboards for

Network & Balancing

Oscillation

Indicator

Since 1999

National Grid, UK Simple Oscillation warning

indicator & operational rules

XM Colombia V. Low frequency oscillation

monitoring hydro/thermal

balance

Oscillations Islanding

Oscillation Event Management, Australia

• Occasional instability events

• Onset time & mode frequency to diagnose

• Real-time location tools of interest

11:14:50 11:15:10 11:15:30 11:15:50 11:16:10 11:16:30

-220

-200

-180

-160

-140

Ra

w D

ata

P

ow

er

(M

W)

11:14:50 11:15:10 11:15:30 11:15:50 11:16:10 11:16:30 0

10

20

30

40

Time

0.6

Hz M

od

e

De

cay T

ime

(se

c)

3% damping

1% damping

Separation avoided, 10 April 2004

Event #1 2004 Generator returned to

service after maintenance with control

issue. Interstate line 150MW oscillations

@ 0.6Hz – separation risk. Generator

rejection restored stability.

Event #2 2010 Generator AVR

malfunction, instability of 0.3Hz QNI

mode, growing to 150MW. Operator

location tests, then AVR state change

restored stability, without generator

rejection.

#1

#2

Oscillation Source Location: Nearest PMU

P1

P2

c11 c

12

c22 c

21

Pd2 Pd1

P1

P2

c11

c12

c21

c22

Pd1

2 generators,

identical damping

2 generators,

only 1 damping

Identify PMU nearest contributing sources Which group of generators?

Which location within group?

Identify changes where damping degraded

Can use sparse PMU monitoring

No currents

IEEE GM Discrete Control - 23/07/2013 - P 11

Western Power, Australia

MGA

NBT

PJR

KW

ALB

MU

MRT

EMDWKT

50mHz, 0.045Hz

Low frequency common mode, 0.045Hz

Same amplitude everywhere

Small phase difference identify sources

IEEE GM Discrete Control - 23/07/2013 - P 12

Western Power, Australia

Source/Sink Location Map, 0.045Hz

Geographic area of main

source identified.

Degrees of 0.045Hz

Mode Phase Shift (NOT 50Hz voltage angle)

IEEE GM Discrete Control - 23/07/2013 - P 13

Manitoba Hydro 0.009Hz Governor Mode Northern Collector System

2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3

6

8

10

12

14

x 10-3

Fre

quency (

Hz)

Event_MH121001_1100to1500LocalMH

2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 320

40

60

80

100

120

140

P2P

Am

plitu

de (

mH

z)

2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3

-0.6

-0.4

-0.2

0

0.2

0.4

P A

mplitu

de in p

hase w

ith F

(M

W))

Time (Hours)

Kettle : K3-dc

Kettle : K1-nac

Kettle : K1-dc

Kettle : K2-dc

Limestone : H1

Limestone : H2

Longspruce : GS-L1

Longspruce : GS-L2

Longspruce : GS-L3

Longspruce : GS-L4

Longspruce : GS-L5

Osc

illat

ion

Am

plit

ude

O

scill

atio

n C

ontr

ibu

tion

Raised oscillation

amplitude

Specific signals

show raised

contribution

(NOT Amplitude)

NOTE: The oscillations occur in the Northern Collector System, connected to the

Eastern Interconnection by a DC corridor

Un

it Po

we

r Ou

tpu

ts

IEEE GM Discrete Control - 23/07/2013 - P 14

Observing and Controlling Transient Stability

Introduction

Oscillations

Transients

Conclusions

Questions

Addressing dynamics issues

Constraint relief and security

Observing and controlling

Roadmap to Real-Time Stability Actions

7

15

22

2

IEEE GM Discrete Control - 23/07/2013 - P 15

Angle-based Wide Area Defence

SW FREQ

E FREQ

Smelter load

132kV ring power

Main generation area

Loss of Large

Smelter in SW

Islanding

Frequency rises

rapidly

Nearby generators change

speed/angle quickly

Frequency rises

more slowly

Trip Gen

proportionally

in correct zone

Angle difference

increase

IEEE GM Discrete Control - 23/07/2013 - P 16

Disturbance Record – 1 Sept 2010

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7-100

-80

-60

-40

-20

0

20

40

Time (sec)

Angle

diffe

rence (

rad)

SIGALDABLANDA

A

BLANDAB

FLJOTSDALUR

KRAFLAFLJ

BusA

FLJBusB

HRA

HRA-FLJ

Diff: 25º

Time: 0.23s

HRA-FLJ

Diff: 50º

Time: 0.41s

Blanda bus tie

opening T=0.5s

-0.2 0 0.2 0.4 0.6 0.8 1

50

50.2

50.4

50.6

50.8

51

Time (sec)

Syste

m F

requency (

Hz)

SIGALDABLANDA

A

BLANDAB

FLJOTSDALUR

KRAFLAFLJ

BusA

FLJBusB

HRA

HRA Frq >50.2Hz

Time: 0.04s

Slower Frq

rise at FLJ

HRA

FLJ

IEEE GM Discrete Control - 23/07/2013 - P 17

∆𝛿 Threshold ∆𝛿

∆𝑓

∆𝑓 Threshold

∆𝛿, ∆𝑓 Relationship

WADS Generation Tripping

Angle Difference

Frequency Difference

Landsnet WADS Triggering Zone

IEEE GM Discrete Control - 23/07/2013 - P 18

Testing with Measurements & Simulation

Pink background =

trip criteria met

Measurements show:

• Restraint when not

required

• Triggering when required

• Confirm thresholds

Simulations show:

• Triggering conditions

met for “family” of

problems

• Threshold levels

• Effectiveness of actions

IEEE GM Discrete Control - 23/07/2013 - P 19

Brazil Separation Example

Other systems show same Area Transient Stability Behaviour

• Similar Δδ & ΔF characteristics

• Separation occurs 5 sec from initial fault

• Other separation events 0.5 to 5s

• Feasible timeframe for action

Loss of Sync

Angle diff

increase 5s

ΔF sustained

5s

Fault

Event Fault Loss of Sync

#1 3 sec & 5 sec

#2 0.8 sec

#3 2.1 sec

#4 0.5s & 0.9s

GB Transient Stability Boundary with Wind

δ

(δ)

δ P

Scotland-England Boundary

~ 3.5GW Transient Stability Limit (P)

~ 1.5GW Wind Capacity in Corridor

Volatility in corridor capability

Expressing Limit as Angle?

• Transient stability closely related

to angle difference

• Should operators run to

Angle, not MW limit?

• Should new HVDC link

control by Angle?

Observing and Controlling Transient Stability

Introduction

Oscillations

Transients

Conclusions

Questions

Addressing dynamics issues

Constraint relief and security

Observing and controlling

Roadmap to Real-Time Stability Actions

7

15

22

2

IEEE GM Discrete Control - 23/07/2013 - P 22

Control Room

• Procedures for oscillations established

• Further operator guidance needed

• Transient stability benefits from angle limit thresholds

Conclusions

Automation

• Δδ, Δf for defence action proportional to system need

• Response time for wide area angle separation is feasible

• Principle applies to many inter-angle separation threats

Roadmap to Real-Time Stability Actions

Growing experience through WAMS improves control actions

www.psymetrix.com