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PMU simulation and application for power system stability monitoring

Harmeet Kang

Areva Technology Centre –

Stafford, UK

Sept. 2009 MOSCOW

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Historical Perspective

Impossible to compare data from geographically different locations

No context to the measurements

Slow RTU data

Technology cost prohibitive

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What is a Phasor

IEEE C37.118 specifies that the angle is 0 degrees when the maximum of the signal to be measured coincides with the GPS pulse and -90 degrees if the positive zero crossing coincides with the GPS pulse.

peak

1pps

Xr (n)

Xi (n)

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Measurement

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PMU device basics

GPSReceiver

Microprocessors

Oscillator

A/D

Analog

Digital

IEEE C 37 .118 DataElectrical

signal

Digitised Samples

Data Frame over Serial or Ethernet

(TCP /UDP )P847 PMU

Anti Aliasing

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PMU device basics

GPSReceiver

Microprocessors

Oscillator

A/D

Analog

Digital

IEEE C 37 .118 DataElectrical

signal

Digitised Samples

Data Frame over Serial or Ethernet

(TCP /UDP )P847 PMU

Anti Aliasing

Phase delays /Variable

CT/VT

Mag/Angle Errors

Fixed delay in gathering data

Small error

Small error

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GPS input

Time

Output Site 1

Light ON

Light OFF

Time

Output Site 2

Light ON

Light OFF

200ms+/- 1ms

<100 ns

Leading edge istiming point

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Acceptable Total Vector Error (TVE)

Where Xr (n) and Xi (n) are the measured real and imaginary components and Xr and Xi are the reference values. This measurement accuracy varies with the magnitude and frequency of the input signal.

1% TVE ~ 0.5 degrees ~ 26 sec @60Hz

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Measurement Window

Internal Reference

Measurement Window

GPS

Filter Coefficients are chosen to provide

A zero degrees phase shift if the middle of the window

corresponds to the peak of the signal

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Filter Length

0

0.2

0.4

0.6

0.8

1

1.2

0 0.5 1 1.5 2 2.5 3 3.5 4

Harmonic

Gai

n

One Cycle

Three Cycles

Seven Cycles

Programmable

1 – 7 Cycles

Default - 5 Cycles

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Impact of Filter Length

Noise Rejection

-60

-55

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

0 20 40 60 80 100

Frequency

Gain

(dB

)

1 Cycle

3 Cycles

7 Cycles

Particularly important to have good noise rejection

as inter area and local oscillations are around 0.1 -3 Hz

-1.5

-1

-0.5

0

0.5

1

1.5

0 0.2 0.4 0.6 0.8 1 1.2 1.4

50 Hz

50 Hz+5% 48 Hz.

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PMU’s in a System

PMU1 PMU2

PMU3 PMU4

PDCE-terra

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Phasor Data Transfer

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IEEE C37.118 Protocol

Configuration => To PDC

Header =>To PDC

Data => To PDC

Command <= From PDC

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PMU Locations and Number of

»Which feeders are key to the interconnection between grid regions

»Which nodes exhibit large shifts in power angle based on a loss of generation, load and change in topology.

»Which areas are of interest from a load modelling perspective

»Which areas of the grid are known to contain dynamic stability issues

»Which areas can form frequency Islands

»Which areas of the grid are prone to voltage collapse

»Which nodes will be most beneficial for the current state estimator improvement and a future linear state estimator

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PMU Locations and Number of

Phenomena

Power Angle

Load Dynamics

Stability monitoring

Frequency Islands

Voltage Collapse

State Estimation

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System Study and Virtual PMU’s

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Application of PMU’s in Power System Stability

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Small Signal Stability

Ability of a power system to maintain synchronism

When subjected to small disturbances.

In today’s practical power systems, the small signal

Stability problem is usually of insufficient damping

of system oscillations

Ref: Power System Stability and Control

Prabha Kundur

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Small Signal Stability

0 5 10 15 20 25 30 35 402.02

0.01507

1.982.025

2.015

Y t( )

400 t

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System Oscillations

Ref: UNDERSTANDING POWER SYSTEM STABILITY

Michael J. Basler and Richard C. Schaefer

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Oscillations

f t( ) ed t sin b t( )

0 2 4 6 8 10 12 14 161

0

1

d>0

f t( )

t

d 0.5

f t( ) ed t sin b t( )

0 2 4 6 8 10 12 14 162000

0

2000

d<0

f t( )

t

Negative damping produces an unstable oscillation

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Power Transfer Between Two Systems after a disturbance

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PMU Data

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Modal Analysis

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1

3

5

7

9

0.5 1 1.5 2 2.5 3

Freq (Hz)

Am

pli

tud

e /

Dam

pin

g

-25

-20

-15

-10

-5

0

5

10

15

20

25

Ph

ase(r

ad

)

Amplitude P

Damping P

Phase P

-1

1

3

5

7

9

0.5 1 1.5 2 2.5 3

Freq(Hz)

Am

pli

tud

e/D

am

pin

g

-25

-20

-15

-10

-5

0

5

10

15

20

25

Ph

ase(r

ad

)

Amplitude K

Damping K

Phase K

Oscillatory Modes and associated

damping factors for two buses in a

system after a small

disturbance

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Frequency Mode Amplitude Damping Factor Phase

5.915093601 0.154921691 3.803229646 -0.56479

-5.915093601 0.154921691 3.803229646 0.564785

2.528276218 6.166677265 5.96187498 12.05712

-2.528276218 6.166677265 5.96187498 -12.0571

0.11361277 0.052975648 -0.243568244 -0.08402

-0.11361277 0.052975648 -0.243568244 0.084017

1.160329029 0.016464454 1.228181975 0.067127

-1.160329029 0.016464454 1.228181975 -0.06713

2.004414648 13.74912722 7.02501959 57.03535

-2.004414648 13.74912722 7.02501959 -57.0354

5.886455596 0.059326209 3.676118362 -0.39502

-5.886455596 0.059326209 3.676118362 0.395017

5.816091733 0.268517515 4.184619447 -0.7797

-5.816091733 0.268517515 4.184619447 0.779701

0.499234685 9.092862427 4.838452008 18.89328

-0.499234685 9.092862427 4.838452008 -18.8933

1.323992576 6.44246368 4.988312993 26.19057

-1.323992576 6.44246368 4.988312993 -26.1906

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Significance of Negative Damping

-10

-8

-6

-4

-2

0

2

4

6

8

10

0 2 4 6 8 10 12 14

-1.5

-1

-0.5

0

0.5

1

1.5

d=7.025

d=4.88

d=-0.24

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Effect of Data Transmission rate of application

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1. 2

1. 4

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1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106 113 120 127 134 141 148 155 162 169 176 183 190 197

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0. 2

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1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106 113 120 127 134 141 148 155 162 169 176 183 190 197

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1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106 113 120 127 134 141 148 155 162 169 176 183 190 197

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1 9 17 25 33 41 49 57 65 73 81 89 97 105 113 121 129 137 145 153 161 169 177 185 193

Every PMU measurement

Every second PMU measurement

Every tenth PMU measurement

Every second

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Operator View of PMU data

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Thank You