PMU-Based Distributed State Estimation with the ... · PDF filePanama-Romeville 230 kV Transmission Line Case: Device: PANROM_A ... PSERC Seminar, June 17, 2008 PSERC 15 GPS Synchronized

PSERC Seminar, June 17, 2008 PSERC1

A. P. Sakis MeliopoulosGeorgia Power Distinguished Professor

School of Electrical and Computer Engineering

Georgia Institute of Technology

PMU-Based Distributed State Estimation with the

SuperCalibratorPSERC Seminar

June 17, 2008


Presentation Outline

The Need for State Estimation

Evolution of State Estimation Technology

GPS Synchronized Measurement Technology

The SuperCalibrator Approach

Implementation and Demonstration (VIWAPA,

May 5-6, 2008)

Future Directions


The Need for State Estimation

1965 Blackout

Edward Teller (member blue ribbon committee)

compared the electric power system with a

dinosaur: Big Body – Small Brain, reflecting on the

fact that at the time the communications

infrastructure and information transmittal was in its

infancy.


Basic Assumptions:

• Positive Sequence Model

• P, Q, V Measurement set

• Near-Simultaneous

Measurements

• Single Frequency

Basic Assumptions:




Measurements


Implications:

• Balanced Operation

• Symmetric Power System

• Biased State Estimator

• Iterative Algorithm

Implications:





Hardware:

• Sensors for P, Q and V

• Accuracy: 1 to 3%

• Communications – mostly

dedicated

• SCADA

Hardware:

• Sensors for P, Q and V

• Accuracy: 1 to 3%

• Communications – mostly

dedicated

• SCADA

Development of the State Estimator – ca 1968


Evolution of Supervisory

Control – State Estimation in

Power Systems


Indicator

Control

Control Center

CommunicationsTerminal

EncoderDecoder

UserInterface

RTU IED DisturbanceRecorders

Relays

GPS

LocalComputer

CommunicationsTerminal

To Data Base Remote Access

SCADA

SCADA circa 1923

SCADA circa 2003

SCADA Evolution


Forward to August 2003

Recommendation 22Evaluate and adopt better real-time tools

for operators and reliability coordinators.

From

US-Canada Power System Outage Task Force

Contributing Factors

Inadequate Situational Awareness


Real Time ModelState Estimation

ApplicationsLoad Forecasting

Optimization (ED, OPF)

VAR Control

Available Transfer capability

Security Assessment

Congestion management

Dynamic Line Rating

Transient Stability

EM Transients, etc.

Visualizations

Markets: Day Ahead, Power Balance,

Spot Pricing, Transmission Pricing

(FTR, FGR), Ancillary Services

Present Operating Model


Basic Tools for Grid Visibility:

SCADA (unfiltered) and SE (filtered)

The objective of SE is to provide a reliable real time model

How Well is it Done, What is the Accuracy

Two Major Issues(a) Data Reliability/Accuracy and (b) Automation

Can We Make All Information Available to All

Constituent Part of the Electric Grid Enterprise?

(The Promise of Automation)


(a) SCADA Transducers: 1 to 3%

(b) Modern Relays: 0.1 to 1%

(c) GPS-Synchronized Equipment:

Magnitude 0.1% to 1%, Phase: 0.01 to

0.05 Degrees at 60 Hz.

(Systematic Errors Can Be Easily

Accounted for)

(b) System Asymmetries (4 to 6%

differences among phases)

(c) System Imbalance (0 to 12% among

phases – based on personal

observations)

(d) Instrumentation Channel Errors (0.02 to

3%)

Present State of the Art

Phase Conductor

Pote

ntial

Tra

nsfo

rmer

CurrentTransformer

PMUVendor A

Burden

Instr

um

enta

tion

Cable

s

v(t)

v1(t)v2(t)

Burdeni2(t)i1(t)

i(t)

Attenuator

AttenuatorAnti-AliasingFilters

RelayVendor C

PMUVendor C

Measurement Layer IED Vendor D


Instrumentation Errors:Voltage Measurement Example

Phase A Magnitude Error: 1.46%

Phase A Phase Error: 0.41 degrees

Phase A Magnitude Error: 1.46%

Phase A Phase Error: 0.41 degrees


Why Do We Need High Accuracy?

Use of raw data for various monitoring, prediction

and control may lead to large errors

If we consider a 50 mile long 230 kV line, rated 400 MVA and

evaluate the required accuracy in voltage magnitude and phase

angle measurements to achieve a 1% accuracy in power flow

then we have the following pairs:

Voltage Magnitude: 0.5%, Phase Angle: 0 degrees

Voltage magnitude: 0.4%, Phase Angle: 0.03 degrees




Basic Assumptions:




Measurements


Basic Assumptions:




Measurements


Implications:





Implications:





Sources of Error:

• GPS-Synchronized

Equipment: Magnitude 0.1%

to 1%, Phase: 0.01 to 0.05

Degrees at 60 Hz

• SCADA: 1 to 3%

• System Asymmetries

(4-6% differences among

phases)

• System Imbalance

(0-12% among phases)

• Instrumentation Channel

Errors (0.02-3%)

Sources of Error:

• GPS-Synchronized

Equipment: Magnitude 0.1%

to 1%, Phase: 0.01 to 0.05

Degrees at 60 Hz

• SCADA: 1 to 3%

• System Asymmetries

(4-6% differences among

phases)

• System Imbalance

(0-12% among phases)

• Instrumentation Channel

Errors (0.02-3%)

Traditional State Estimator

Time Response:

• Centralized State Estimator Response (minutes)

Time Response:

• Centralized State Estimator Response (minutes)


Important ExampleWhat Are the Limits of Traditional State Estimation?

Close

ENTERGY: Panama-Romeville 230 kV Line - Dynamic Rating project

P 136.5 MW, Q 11.80 MVar

S = 137.0 MVA, PF = 99.63 %

S

Van = 130.7 kV, -5.908 Deg

Vbn = 131.0 kV, -125.5 Deg

Vcn = 131.3 kV, 114.6 Deg

Van

Vbn

Vcn

Ia = 369.9 A, -11.56 Deg

Ib = 335.0 A, -130.5 Deg

Ic = 341.4 A, 110.5 DegIa

Ib

Ic

Panama-Romeville 230 kV Transmission Line

Case:

Device:

PANROM_A

PANROM_B

PANROM_C

PANROM_A

PANROM_B

PANROM_C

Voltages

Currents

3 Phase Power Voltage

CurrentPer Phase Power

Phase Quantities

Symmetric Comp

PANROM_NRef

Device Terminal Multimeter

L-G

L-L

Side 1 Side 2

Impedance

Program W inIGS - Form IGS_MULTIMETER

Close

ENTERGY: Panama-Romeville 230 kV Line - Dynamic Rating project

P 136.5 MW, Q 11.80 MVar

S = 137.0 MVA, PF = 99.63 %

S

Vp = 131.0 kV, -5.613 Deg

Vn = 439.8 V, -110.2 Deg

Vz = 297.1 V, -129.2 Deg

Vp

Ip = 348.7 A, -10.56 Deg

In = 13.28 A, -32.91 Deg

Iz = 8.890 A, -19.62 DegIp

InIz

Panama-Romeville 230 kV Transmission Line

Case:

Device:

PANROM_A

PANROM_B

PANROM_C

PANROM_A

PANROM_B

PANROM_C

Voltages

Currents

3 Phase Power Voltage

CurrentPer Phase Power

Phase Quantities

Symmetric Comp

PANROM_NRef

Device Terminal Multimeter

L-G

L-L

Side 1 Side 2

Impedance

Program W inIGS - Form IGS_MULTIMETER

kVeV

kVeV

j

pos

j

an

0

0

613.5

908.5

0.131~

7.130~

kVeI

AeI

j

pos

j

a

0

0

56.10

56.11

7.348~

9.369~


GPS Synchronized Measurements

Enable Distributed State Estimation


History of GPS-Synchronized

Measurements

Efforts to Develop Technologies with Accurate Time Synchronization

Started in the Early 80’s. Examples:

Missout & Girard, 1980

Bonanomi, 1981

Phadke, 1989-90

These efforts resulted in technologies with time synchronization accuracy

that was several tens of microseconds.

In 1992, Macrodyne (Jay Murphy) introduced the first PMU (Phasor

Measurement Unit) capable of taking measurements with synchronization

comparable to GPS clock accuracy (microsecond accuracy)


Macrodyne 1620 PMU

A/D Converter

( Modulation)

Input Protection &Isolation Section

OpticalIsolation

P Mem

ory

PLL

Digitized Data2880 s/s

A/D Converter

( Modulation)

Input Protection &Isolation Section

OpticalIsolation

Sampling Clock

GPSReceiver

Digitized Data2880 s/s

1PPS IRIGB

GPSAntenna

DataConcentrator(PC)

Display&

Keyboard

RS232

MasterWorkstation

OpticalIsolation

OpticalIsolation

AnalogInputsV : 300VI : 2V

Released to Market January 1992

CHARACTERISTICS

Individual Channel

GPS Sync

Common Mode

Rejection Filter with

Optical Isolation

16 bit A/D Modul.

Time Precision 1 s

0.02 Degrees at 60 Hz

Time Precision 1 s

0.02 Degrees at 60 Hz


NYPA’s Harmonic Measurement System Using GPS

Synchronized Measurements (Macrodyne’s PMUs)

I

Global Time

Reference

(GPS)

GPS

Receiver

Micro

processorA/D

Phasor data

(time stamped)Serial

Communication

Port

Filt

er

To Control Center

Harmonics Data

Concentrator

(Located in Atlanta)

PMU Block Diagram

V

GPS Antena

ADD Bulletin

Board System

GIC Data

Concentrator

Located at NYPP

PMU

Computer

PMU

Computer

PMU

Computer

Asymmetric Power

System Model

New York Power Authority

NYPA Project Launched: 1993, Completed: 1998NYPA: Shalom Zelingher, Bruce Fardanesh

GaTech: Meliopoulos & Cokkinides

First Wide Area Monitoring System

In Eastern Interconnection

First Wide Area Monitoring System

In Eastern Interconnection


The SuperCalibrator Concept…

Develop a State Estimator that Addresses all of the Above

Issues

IMPORTANT FEATURE:

The presence of GPS Synchronized Measurements

Allows Full Decentralization of the State Estimation

Process

IMPLEMENTATION:

Formulate the State Estimation Problem for Each

Substation. Transport the Substation State Estimates to

Control Center and Synthesize the System State

Develop a State Estimator that Addresses all of the Above

Issues

IMPORTANT FEATURE:

The presence of GPS Synchronized Measurements

Allows Full Decentralization of the State Estimation

Process

IMPLEMENTATION:

Formulate the State Estimation Problem for Each

Substation. Transport the Substation State Estimates to

Control Center and Synthesize the System State


The SuperCalibrator is a Substation Based

State Estimator with the Following

Features:

Eliminates Model Biases(Full Three-Phase Model with Neutrals, etc.)

Eliminates Imbalance Biases(Single Phase or Three Phase Measurements)

Eliminates Biases From Instrumentation

Channel Errors(Model is Augmented with Instrumentation)

Robustness(Model Quadratization)

20


The SuperCalibrator is conceptually very simple. The basic

idea is to provide a model based error correction of substation

data and in particular RELAY DATA. The basic idea is to utilize

a high fidelity model of the substation, (three-phase, breaker-

oriented model, instrumentation channel inclusive and data

acquisition model inclusive). Then all substation data obtained

with any device, PMU, meter, relay, SCADA, etc. is expressed

as a function of the state of the high fidelity substation model.

The SuperCalibrator uses (a) a static state estimator algorithm,

and (b) a dynamic state estimator algorithm.

GPS Synchronized Relays Make the Process Robust and

the Results Globally Valid

The SuperCalibrator Concept


SuperCalibrator Schematic Representation

Phase Conductor

Pote

ntial

Tra

nsfo

rmer

CurrentTransformer

PMUVendor A

Burden

Instr

um

enta

tion

Cable

sv(t)

v1(t)v2(t)

Burdeni2(t)i1(t)

i(t)

Attenuator

AttenuatorAnti-AliasingFilters

RelayVendor C

PMUVendor C

Measurement Layer

Super-Calibrator

Data

Processing

IED Vendor D

LA

NLA

N

FireWall

Encod

ing/D

ecodin

gC

ryp

tog

raph

y

Model Based Data Validation and Information Extraction(Redundancy, Bad Data Rejection, Statistical Estimation, etc.)


SuperCalibrator

Implementation on the

VIWAPA System


Demonstration (Pilot) Project

Pilot project for demonstrating the application of the SuperCalibrator concept for

distributed state estimation on the US Virgin Islands power network.

St. Thomas Island

St. John

Island

US Virgin Islands consist of the main islands of St. Croix, St. John and St. Thomas, along with

many other surrounding minor islands.

The network is a stand-alone power system and is not connected to the US national power

grid.

The SuperCalibrator is implemented on the St. Thomas and St. John Islands power system –

the system has five substations and a generating plant.

Each substation has at least one SEL 421 relay or SEL 734 with GPS-synchronized

measurement capability.


Implementation

Substation Model

Substation State

Measurements

Pseudo-measurements

Estimation Method


Substation Model

• Physically Based Component Modeling

• Explicit Representation of Phase Conductors, Neutrals,

Ground Conductors and Grounding – accounts for ground

potential rise

• Explicit Representation of Breakers, Switches

• Explicit Representation of Instrumentation and Relay Inputs

Integrated with the Power System


SuperCalibrator ImplementationSubstation Configuration – Long Bay – 3D Model


SuperCalibrator ImplementationSubstation Configuration – Long Bay










SuperCalibrator ImplementationState Estimation Configuration – Long Bay


SuperCalibrator ImplementationState Estimation Configuration – Long Bay


State Definition Substation

V1e

~V2e

~

V3e

~V4e

~

V1s

~V2s

~

Definition of State for a Substation

sV1

~Vector of dimension 4: nscsbsas VVVV ,1,1,1,1

~,

~,

~,

~

sV2

~Vector of dimension 4: nscsbsas VVVV ,2,2,2,2

~,

~,

~,

~

eV1

~Vector of dimension 4: necebeae VVVV ,2,2,2,2

~,

~,

~,

~

…… …

eV4

~Vector of dimension 4: necebeae VVVV ,4,4,4,4

~,

~,

~,

~

SuperCalibrator

Static State Estimation

Substation State


SuperCalibrator Measurement Set

• Any Measurement at the Substation from Any IED

(Relays, Meters, FDR, PMUs, etc.)

• Data From at Least one GPS-Synchronized Device

• Pseudo-Measurements

Kirchoff’s Current Law

Remote End State Measurement

Missing Phase Measurements

Neutral/Shield Current Measurement

Neutral Voltage


SuperCalibrator Measurement SetGPS-Synchronized Measurements

~~~~,, NkAk VVz

~

~

~

~

~

~

~

~~

,

,

,

,

,

,

,,1,,1

Ck

Bm

Am

Ck

Bk

Ak

T

AkdAkd

V

V

V

V

V

V

CIz

GPS-Synchronized Measurements

Voltage Phasor

Current Phasor


SuperCalibrator Measurement SetNon-Synchronized Measurements

j

meassync eAA~~

alpha is a synchronizing unknown variable

Cos and sin of alpha are unknown variable in the state

estimation algorithm

There is one alpha variable for each non-synchronized relay


SuperCalibrator Measurement SetNon-Synchronized Measurements

2~~ 2

,, NkAk VVz

*

,

,

,

,

,

,

,,1,,,1

~

~

~

~

~

~

~Re

Ck

Bm

Am

Ck

Bk

Ak

T

AkdAkAkd

V

V

V

V

V

V

CVPz

Non-Synchronized Measurements

Real Power

Voltage Magnitude

22

,,,,

2

,,,, iNkiAkrNkrAk VVVV

cossin(

sincos

~~

imagreal

imagreal

j

meassync

AAj

AA

eAA

Example 1

Example 2


Substation k

IS

~IR

~

VS

~

VR

~

Line i

R

S

R

S

V

V

YY

YY

I

I~

~

~

~

2221

1211

SS

mpseudo VYZYZIZYZVR

~~~2122

1

222221

1

2222

,II

1

2221

1211

2221

1211

YY

YY

ZZ

ZZ

SuperCalibrator Measurement Set:Remote End State Measurement

Line i Equations

Solve for V at remote end

Where:

Expected Error: 0.01%

Demonstration Example


Substation

I4

~

I3

~

I5

~I6

~I1

~

I2

~

SuperCalibrator Measurement Set:Kirchoff’s Current Law

0~~~

621 III

0~~~~~

212431 mIIIkIIk




SuperCalibrator Measurement Set:Missing Phase Measurements

0~~ 0

/

240, j

a

mpseudo eVVns

Assume There is a Phase A Voltage Phasor Measurement.

Assume there is no Phase C Measurement.

THEN:

Expected Error: Less than 3%


SuperCalibrator: Estimation Method

synnonphasor kkJMin

2222

*~~

~~~~,, NkAk VVz

~

~

~

~

~

~

~

~~

,

,

,

,

,

,

,,1,,1

Ck

Bm

Am

Ck

Bk

Ak

T

AkdAkd

V

V

V

V

V

V

CIz

2~~ 2

,, NkAk VVz

*

,

,

,

,

,

,

,,1,,,1

~

~

~

~

~

~

~Re

Ck

Bm

Am

Ck

Bk

Ak

T

AkdAkAkd

V

V

V

V

V

V

CVPz

GPS-Synchronized Measurements Non-Synchronized Measurements

Voltage Phasor

Current PhasorReal Power

Voltage Magnitude

22

,,,,

2

,,,, iNkiAkrNkrAk VVVV


SuperCalibrator: Estimation Method

synnonphasor kkJMin

2222

*~~

Solution

xhzAxx 1

WHWHHA TT 1where:

EfficiencyExample, Long Bay Substation, High End PC

One Iteration: 18,000 multiply-adds (0.002 seconds)

Compute Matrix A: Variable (sparsity) – Almost Invariant (0.010 secs)


State Estimation Performance Evaluation

Chi-Square Test

Step 1: Compute the state estimate x*

Step 2: Evaluate the function

Step 3: Compute p(k) = 1 - P(a/k2, m-n)

where:

P(a/k2,u) is the probability that J < a

and u is the degrees of freedom

2

* ~~

k

arrJ H

W


Performance Achievement

Visualization is Updated 4 Times a Second


Overall Performance MetricChi-Square Test

Master Report Provides Overall SE Performance in Terms of k factor


SuperCalibrator – Storing and Retrieving Data

Program XfmHms - Page 1 of 1

c:\wmaster\xfm\datau\viwapa_001 - Apr 08, 2008, 16:42:01.500000 - 2.0 samples/sec - 1024 Samples

16:43 16:44 16:45 16:46 16:47 16:48 16:49

59.99

59.99

60.00

60.00

60.00

60.00

60.01

60.01

60.01 Long_Bay_Substat_Frequency (Hz)VIW_LONGBAY_B305_Frequency (Hz)VIW_LONGBAY_B307_Frequency (Hz)SelFmpDevice_Frequency (Hz)SelFmpDevice_Frequency (Hz)

-176.0

-156.4

-136.8

-117.3

-97.73

-78.17

-58.62

-39.06

-19.50 Long_Bay_Substat_V1LPM_PHA (Degrees)VIW_LONGBAY_B305_V1LPM_PHA (Degrees)VIW_LONGBAY_B307_V1LPM_PHA (Degrees)SelFmpDevice_V1_PHA (Degrees)SelFmpDevice_V1_PHA (Degrees)


16:46:02 16:46:06 16:46:10 16:46:14 16:46:18 16:46:22 16:46:28

-79.94

-77.71

-75.48

-73.25

-71.02

-68.79

-66.56

-64.33

-62.09 Phase Angle (Degrees)

Tutu

Long Bay

East End

SuperCalibrator – Storing and Retrieving Data


SuperCalibrator ImplementationExample of Measurement/Pseudo-M Count – Long Bay

Long Bay Substation

Number of Analog Measurements: 318 real

Number of Pseudo-measurements: 72 real

Number of Status Measurements: 15

Future:

Beckwith Relay Measurements: 2

Number of States: 24+20

Long Bay 35 kV Bus: 3 (complex)

Long Bay 13 kV Bus: 3 (complex)

RHPP 35 kV Bus: 3 (complex)

East End 35 kV Bus: 3 (complex)

Redundancy

886%


SuperCalibrator: Estimation MethodScalability

Large Substation ImplementationAssumptions: 3 kV levels,70 relays, 5 PMUs, 35 breakers

Number of Analog Measurements: 1500 real

Number of Pseudo-measurements: 340 real

Number of Status Measurements: 35

Number of States: 54+65=119

EfficiencyHigh End PC

One Iteration: 220,000 multiply-adds (0.022 seconds)

Compute Matrix A: Almost Invariant - Compute Once Upon SetUp


Summary

• The SuperCalibrator Concept was Introduced to Solve the Limitations

of Traditional State Estimators:

1. System Asymmetries,

2. Voltage Imbalance,

3. Instrumentation Channel Error.

• The SuperCalibrator Concept has Been Successfully Demonstrated on

Several Systems Including a Small Five-Substation Power System

• State Estimation rates of FOUR PER SECOND has been achieved

• The SuperCalibrator Approach is Scalable to Any Size System


Future Directions


Real Time ModelState Estimation

ApplicationsLoad Forecasting

Optimization (ED, OPF)

VAR Control

Available Transfer capability

Security Assessment

Congestion management

Dynamic Line Rating

Transient Stability

EM Transients, etc.

Visualizations

Markets: Day Ahead, Power Balance,

Spot Pricing, Transmission

Pricing (FTR, FGR), Ancillary

Services

Present State of the Art: Separation of C&O and P&C

Control & Operation Protection & Control

The Infrastructure for Both Functions is Based on

Similar Technologies: Thus the Opportunity to Merge,

Cut Costs, Improve Reliability

Component

Protectiongenerators, transformers,

lines, motors, capacitors,

reactors

System

ProtectionSpecial Protection

Schemes, Load Shedding,

Out of Step Protection, etc.

CommunicationsSubstation Automation,

Enterprize, InterControl

Center


From ThisFrom This

To ThisTo This

PSERC Project T38 – Substation of the Future

Documents

PMU-Based Distributed State Estimation with the ... · PDF filePanama-Romeville 230 kV Transmission Line Case: Device: PANROM_A ... PSERC Seminar, June 17, 2008 PSERC 15 GPS Synchronized