PSTI_EMS

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ENERGY MANAGEMENT SYSTEM

Overview

October 10, 2011

Dr Shekhar KELAPURE

PSTI, Bangalore

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What we cover

Load Dispatch

Why EMS

What is EMS

Components of EMS

Network Applications Framework

State Estimator

Power Flow & Optimal Power Flow

Contingency Analysis

Load Forecast

Dr Shekhar Kelapure 2

What we do NOT cover

Generation Applications

Fault Analysis

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Load Dispatch

Objective -> Operate/Drive the Power System

so that it is Stable

Reliable

Secure

OPTIMAL

Operate Power System Efficiently

Whats so big

3Dr Shekhar Kelapure

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Why Energy Management System (EMS)?

What is expected from the Dispatcher?

Stable/reliable/secure and optimal Operation

What the Dispatcher need to know? Complete knowledge about the system

(Parameters and models of the System components)

And Knowledge of the Situation Situation Awareness

(Real Time data of the system)

EMS Mechanism to capturesystem knowledge and situation awareness

And provide key indicators


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Mechanism to hold the system knowledge

Mechanism to capture real time data (meas)

Analog measurements (P, Q, V, F, )

Digital measurements (Status - CBs etc)

Validate the measurements

Analyze system performance using softwareprograms and provide key indicators

Display data/measurements on meaningfuldisplays

Send control commands

to operate the system efficiently

What is Energy Management System?


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DatabasesDatabases

Components of EMS

Presentation

Layer

(DISPLAYS)

Presentation

Layer

(DISPLAYS)

AutomaticGeneration Control

AutomaticGeneration Control

Economic DispatchEconomic Dispatch

Reserve/CostMonitoring

Reserve/CostMonitoring

Unit Commitment/Scheduling

Unit Commitment/Scheduling

Data Validation(State estimator)Data Validation

(State estimator)

Power Flow

Optimal Power Flow

Power Flow

Optimal Power Flow

Contingency AnalysisContingency Analysis

Fault AnalysisFault Analysis

Data Acquisition(SCADA)

Data Acquisition(SCADA)

Load ForecastLoad Forecast

6

Network Application Generation Application

Data Layer

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Network Application Functions

Objective Analyze Power System performance from

network (transmission and generation) perspective

To check

Base case violations

Optimal performance (Loss Minimization etc.)

Security Assessment & EnhancementFault Analysis

What we need

GOOD measurements Load, Gen, Flows info.

Transmission System Data Capacities, R, X, B, Tap etc

Generation Data Ratings & other parameters


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NA Functions used in EMS

State Estimator

To identify Anomalies

Power Flow & Optimal Power Flow

To carry out simulations

To get optimal set-points


What if Analysis (N-1, N-2 etc)

Security Assessment and Enhancement

Assessment and corrective actions

Load Forecast Input to Simulations (NA functions)


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Objective :

Filter out Dead system components

Establish connectivity information and

Define the LIVE(Energized) network with

Inputs :

System Components Details,

Switch Statuses and the Measurements (V, Power Flows,

injections etc)

Output :

Live(energized) network details

Formation of networks (Island wise)

Mark viable islands (with Generation)

Network Topology


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COMPONENT DETAILS

GEN1 BUS1

GEN2 BUS2

GEN3 BUS3

SYNCON1 BUS6

SYNCON2 BUS8

TRANS1 BUS5 BUS6

TRANS2 BUS4 BUS9

LINE1 BUS1 BUS2

LINE2 BUS1 BUS5

LINE3 BUS2 BUS3

Network Topology Formation

SWITCH DETAILS

BUS1CB1

BUS1CB2

BUS1CB3

BUS1CB4BUS2CB1

BUS2CB2

BUS2CB3


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Network Topology Node Terminology

Secondary bus

Primary bus

BusCouplers

Incomer #2Incomer #1

Outgoing #1 Outgoing #2

Nodes withUnique ID


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1.060.002.32 - j 0.17

1.045-4.980.183 + j 0.295

1.055-15.67-0.061 - j 0.016

1.05-15.73-0.135 - j 0.058

1.035-16.47-0.149 - j 0.056

1.057-15.3-0.035 - j 0.018 1.052-15.51

-0.09 - j 0.058

1.01-12.73-0.942 + j 0.44

1.021-8.77

-0.076 - j 0.018

1.07-14.83-0.112 + j 0.068

1.09-13.6600 + j .172

1.02-10.34-0.478 + j 0.039

1.057-15.3-0.295 - j 0.166

1.57-j0.17

-1.53+j0.31

0.56-j0.003

0.73+j0.06

0.42+j0.02-0.40+j0.003

-0.73+j0.053-0.73+j0.053

0.63-j0.14

0.75+j0.06

-0.62+j0.16

-0.55+j0.0540.24-j0.36

-0.23+j0.045-0.71+j0.038

0.16-j0.003

-0.17+j0.017

0.077-j0.026

-0.076-j0.025

0.015+j0.01

0.17+j0.075

-0.17-j0.08

-0.015-j0.01 0.051+ j0.02

0.065+j0.038

DIGITAL DATA

BUS1CB1 CLOSE

BUS1CB2 OPEN

BUS1CB3 CLOSE

BUS1CB4 CLOSE

BUS2CB1 CLOSE

BUS2CB2 CLOSE

BUS2CB3 OPEN

BUS2CB4 CLOSE

BUS2CB5 CLOSE

BUS2CB6 CLOSE

BUS2CB7 OPEN

BUS3CB1 OPEN

ANALOG DATA

P, Q FLOWSGENERATIONS

VOLTAGES (ANGLES?)

FREQUENCY

Real-Time Data superimposed on Line Network


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CONNECTIVITY INFO

ISLAND #1

GEN1 BUS1

GEN2 BUS2

GEN3 BUS3

SYNCON2 BUS8

TRANS1 BUS5 BUS6

TRANS2 BUS4 BUS9

LINE1 BUS1 BUS2

LINE2 BUS1 BUS5

LINE3 BUS2 BUS4

ISLAND #2

LOAD12 BUS12

Network Topology - Output


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Objective :

Identify and correct Anomalies, Suppress Bad data

Refine the measurement set to form the State of the system

Inputs :

Energized System Components Details

(Connectivity + Parameters)

Switch Statuses (CBs, ISOs)

Measurements (V, Power Flows, Loads, Generations)Tuning Parameters (Tolerances, Statistical Info etc)

Output :

Estimated complex voltages,

Estimated P and Q injections and flowsError Analysis, List of Bad Data

Methodology : Weighted Least Square (WLS)

State Estimation


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State EstimatorRefine Measurements

System Info,Measurements and

switch statusesNetwork Topology

NO

Observable? Add PseudoMeasurements

Print resultsVoltage profile

Loads and Generations

Real/ reactive flowsMeas Vs EstimatesBad Data Processing

Identify/suppress bad data

acceptable?YES

YES

NO

State Estimator (SE) Data Flow


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Measurements

Bus Voltages Magnitudes (V) and Angles

Generations (Pgen and Qgen) and Loads (PL and QL)

Flows(real and reactive) at either end of lines/ transformerSize 4 x Nlines(Flows) + Nbus (V) + Ngen (Gen)

Output

State variables (complex voltages at all buses 2 x NBUS)

? How many measurements are required?

More measurements slower the estimation process

Less Measurements erroneous results (poor estimation)

Optimum - 1.5 to 2.8 times the state variables

Measurements


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1.062.32 - j 0.17

1.0450.183 + j 0.295

1.055

-0.061 - j 0.016

1.05-0.135 - j 0.058

1.035

-0.149 - j 0.056

1.057-0.035 - j 0.018 1.052

-0.09 - j 0.058

1.01-0.942 + j 0.44

1.021

-0.076 - j 0.018

1.07-0.112 + j 0.068

1.0900 + j .172

1.02-0.478 + j 0.039

1.057-0.295 - j 0.166

1.57-j0.17

-1.53+j0.31

0.56-j0.003

0.73+j0.06

0.42+j0.02-0.40+j0.003

-0.43+j0.053

0.63-j0.14

0.75+j0.06

-0.62+j0.16

-0.55+j0.0540.24-j0.360

0.23+j0.0450+j0

0.16-j0.003

-0.17+j0.017

0+-j0

0+j0

0.0+j0.0

0.17+j0.075

-0.17-j0.082.32 - j 0.17

0.0+j0.00.051+ j0.02

0.065+j0.038

INCONSISTANCIES

FLOWS

P15 AND P51

P23 AND P32Q34 AND Q43

LOADS

P12

Q12

V12

Identify Measurement Errors


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1.062.32 - j 0.17

1.0450.183 + j 0.295

0.0

-0.0 - j 0.0

1.05-0.135 - j 0.058

1.035

-0.149 - j 0.056

1.057-0.035 - j 0.018 1.052

-0.09 - j 0.058

1.01-0.942 + j 0.44

1.021

-0.076 - j 0.018

1.07-0.112 + j 0.068

1.0900 + j .172

1.02-0.478 + j 0.039

1.057-0.295 - j 0.166

1.57-j0.17

-1.53+j0.31

0.56-j0.003

0.+j0.0

0.42+j0.02-0.40+j0.003

-0.43+j0.053

0.63-j0.14

0.75+j0.06

-0.62+j0.16

-0.55+j0.0540.24-j0.360

0.23+j0.0450+j0

0.16-j0.003

-0.17+j0.017

0+-j0

0+j0

0.0+j0.0

0.17+j0.075

-0.17-j0.082.32 - j 0.17

0.0+j0.00.051+ j0.02

0.065+j0.038

Suppress Erroneous Measurements

REMOVE

INCONSISTANCIES

SUPRESS

P51

P23

Q34

LOADS

P12 = 0.0Q12 = 0.0

V12 = 0.0

IGNORE

OR

REPLACE WITH

APPROPRIATE VALUES


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1.062.32 - j 0.17

1.0450.183 + j 0.295

0.0-0.0 - j 0.0

1.05-0.135 - j 0.058

1.035-0.149 - j 0.056

1.01-0.942 + j 0.44

1.021-0.076 - j 0.018

1.07-0.112 + j 0.068

1.0900 + j .172

1.02-0.478 + j 0.039

1.057-0.295 - j 0.166

1.57-j0.17

-1.53+j0.31

0.56-j0.003

0.+j0.0

0.42+j0.02

-0.40+j0.003

-0.43+j0.053

0.63-j0.14

0.75+j0.06

-0.62+j0.16

-0.55+j0.054

0.24-j0.360

0.23+j0.0450+j0

0.16-j0.003

-0.17+j0.017

0+-j0

0+j0

0.0+j0.0

0.17+j0.075

-0.17-j0.080.0+j0.0

0.051+ j0.02

0.065+j0.038

1.057-0.035 - j 0.018 1.052

-0.09 - j 0.058

Check Observability

UNOBSERVABLE - Enable to estimate due to insufficient measurements

Calculations beyond the reach of available measurements

OBSERVABILITY

Insufficient

Measurements @

BUS10 and BUS11

??WHAT TO DO?? - - - - - - - - - - - - - - - - - - - - ADD PSUEDO MEASUREMENTS


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1.060.002.32 - j 0.17

1.044-4.980.183 + j 0.295

0.0-0.0 - j 0.0

1.05-15.73-0.135 - j 0.058

1.035-16.47-0.149 - j 0.056

1.057-15.3-0.035 - j 0.018 1.052-15.51

-0.09 - j 0.058

1.012-12.73

-0.942 + j 0.44

1.023-8.77-0.076 - j 0.018

1.07-14.83-0.112 + j 0.068

1.09-13.6600 + j .172

1.02-10.34-0.478 + j 0.039

1.057-15.3-0.295 - j 0.166

1.56-j0.17

-1.52+j0.31

0.56-j0.003

0.+j0.0

0.41+j0.02-0.38+j0.003

-0.63+j0.053

0.61-j0.14

0.65+j0.06

-0.59+j0.16

-0.55+j0.0540.18-j0.360

-0.17+j0.0450+j0

0.18-j0.003

-0.17+j0.017

0+-j0

0+j0

0.0+j0.0

0.17+j0.075

-0.17-j0.080.0+j0.0

0.051+ j0.02

0.065+j0.038

ESTIMATES :

Voltages

1 1.0600.00

1 1.044-4.980

1 1.012-12.73

1 1.020-10.34

Power Flows

1 2 1.56 0.170

1 5 0.65 +0.060

2 1 1.52 +0.31

2 4 0.55 0.003

2 5 0.41 +0.020

Estimation Output


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IDENTIFY BAD DATA

Voltages

Measu Estimat

1 1.060 1.060

2 1.045 1.044

3 1.010 1.012

4 1.020 1.0204

Power Flows

Meas Estimat

1 2 1.57 1.561 5 0.75 0.65

2 1 1.53 1.52

2 4 0.56 0.55

2 5 0.42 0.41

1.060.002.32 - j 0.17

1.044-4.980.183 + j 0.295

0.0-0.0 - j 0.0

1.05-15.73-0.135 - j 0.058

1.035-16.47-0.149 - j 0.056

1.057-15.3-0.035 - j 0.018 1.052-15.51

-0.09 - j 0.058

1.012

-12.73-0.942 + j 0.44

1.023-8.77-0.076 - j 0.018

1.07-14.83-0.112 + j 0.068

1.09-13.6600 + j .172

1.02-10.34-0.478 + j 0.039

1.057-15.3-0.295 - j 0.166

1.56-j0.17

-1.52+j0.31

0.56-j0.003

0.+j0.0

0.41+j0.02-0.38+j0.003

-0.63+j0.053

0.61-j0.14

0.65+j0.06

-0.59+j0.16

-0.55+j0.0540.18-j0.360

-0.17+j0.0450+j0

0.18-j0.003

-0.17+j0.017

0+-j0

0+j0

0.0+j0.0

0.17+j0.075

-0.17-j0.08

0.0+j0.00.051+ j0.02

0.065+j0.038

Bad Data Identification


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1.060.002.32 - j 0.17

1.045-4.980.183 + j 0.295

1.055-15.67-0.061 - j 0.016

1.05-15.73-0.135 - j 0.058

1.035-16.47-0.149 - j 0.056

1.057-15.3-0.035 - j 0.018 1.052-15.51-0.09 - j 0.058

1.01-12.73-0.942 + j 0.44

1.021-8.77-0.076 - j 0.018

1.07-14.83-0.112 + j 0.068

1.09-13.6600 + j .172

1.02-10.34

-0.478 + j 0.039

1.057-15.3-0.295 - j 0.166

1.57-j0.17

-1.53+j0.31

0.56-j0.003

0.73+j0.06

0.42+j0.02-0.40+j0.003

-0.73+j0.053

0.63-j0.14

0.75+j0.06

-0.62+j0.16

-0.55+j0.0540.24-j0.36

-0.23+j0.045-0.71+j0.038

0.16-j0.003

-0.17+j0.017

0.077-j0.026

-0.076-j0.025

0.015+j0.01

0.17+j0.075

-0.17-j0.08

-0.015-j0.01 0.051+ j0.02

0.065+j0.038

OMIT BAD MEAS

Power Flows

Meas Estimat

1 5 0.75 0.65

5 1 0.43 -0.63

Bad Data Suppression


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1.060.002.32 - j 0.17

1.045-4.980.183 + j 0.295

1.055-15.67

-0.061 - j 0.016

1.05-15.73-0.135 - j 0.058

1.035-16.47

-0.149 - j 0.056

1.057-15.3-0.035 - j 0.018 1.052-15.51

-0.09 - j 0.058

1.01-12.73-0.942 + j 0.44

1.021

-8.77-0.076 - j 0.018

1.07-14.83-0.112 + j 0.068

1.09-13.6600 + j .172

1.02-10.34-0.478 + j 0.039

1.057-15.3-0.295 - j 0.166

1.57-j0.17

-1.53+j0.31

0.56-j0.003

0.73+j0.06

0.42+j0.02-0.40+j0.003

-0.73+j0.053

0.63-j0.14

0.75+j0.06

-0.62+j0.16

-0.55+j0.0540.24-j0.36

-0.23+j0.045-0.71+j0.038

0.16-j0.003

-0.17+j0.017

0.077-j0.026

-0.076-j0.025

0.015+j0.01

0.17+j0.075

-0.17-j0.08

-0.015-j0.01 0.051+ j0.02

0.065+j0.038

Final Estimation

This becomes the base case for the remaining Network Analysis Functions


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Objective :

To compute the power flow in the branches

thru the complex voltages for given load/ generation profile

Inputs : system information

component parameters and connectivity

load and generation profile, voltage set-points

output : voltage profile (voltage magnitude and angles)

power flow calculations

loss calculation

violations (voltage magnitude and power flows)

MODELLING IS CRUCIAL

Power Flow


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Kirchhoffs current Law

Power Injection at ith

bus Si = Vi x Ii*

?? Set of Simultaneous Non-linear equations ??

Gauss Seidel (only for very small systems)Newton Raphson (Normally used)

Fast Decoupled (Modified Newton Raphson)

( )

( )jiijij

n

jjii

jiijij

n

j

jii

YVVQ

YVVP

+=

+=

=

=

sin

cos

1

1

Vi ithbus

To bus 1

V1

To bus j

Vj

To bus k

Vk

Yii

YijYi1 Yik

Power Flow Basic equations


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Non-linear eqns

Linearize & solve Iteratively

Characteristics

Quadratic Convergence

Normally 3-5 iterations

Reliable

Difficulty - Handling Large Matrices MISMATCHJACOBIANUPDATE

NBUSNBUSNBUS

NBUS

Q

P

V

QQV

PP

V

VV

QQV

PP

Q

P

=

=

1

Newton Raphson based Power Flow

Whats way out? Try de-coupling ?FDLF?

[ ] [ ] [ ]

[ ] [ ]QV

QV

PP

=

=

1

1

Assumptions

1. |V| ~ 1.0 p.u.Bus angle ) very small

2. Sin()=0

3. Cos()=1

4. R

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OUTPUT

SLK Pgen , Qgen

PV - , Qgen

PQ - , |V|

In additionBranch Pflow , Qflow

LOSSES PL , QL

SHUNT POWER

Power Flow, Inputs and Output

INPUTS

System DATA

LINE DETAILS(RXB)

XMER DETAILS(RXT)

GENERATOR DATA(QLT)

SHUNT DATA(B)

LOAD/GEN DATA

LOAD DATA

GENERATION DATA(PV)

TUNING PARAMETERS


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BUS WISE RESULTS IN TABULATED FORM

sr_no bus_no v_mag v_angle(rad) p_inj q_inj

1 1 1.0600 .0000 2.3238 -.1707

2 2 1.0450 -.0870 .1830 .2950

3 3 1.0100 -.2221 -.9420 .0440

4 4 1.0700 -.2589 -.1120 .0682

5 5 1.0900 -.2385 .0000 .1716

6 6 1.0186 -.1805 -.4780 .03907 7 1.0623 -.2385 .0000 .0000

8 8 1.0207 -.1532 -.0760 -.0180

9 9 1.0567 -.2673 -.2950 -.1660

10 10 1.0517 -.2708 -.0900 -.0580

11 11 1.0573 -.2671 -.0350 -.0180

12 12 1.0551 -.2735 -.0610 -.0160

13 13 1.0503 -.2745 -.1350 -.0580

14 14 1.0351 -.2875 -.1490 -.0560**********************************************************

BUS WISE DETAILED RESULTS

results for bus number 1

voltage(pu) 1.0600 angle(deg) -.0001

flow to (MW/MVAr) 2 1.5689 -.1744

flow to (MW/MVAr) 8 .7549 .0610

line charging (MVAr) -.0573

shunt injection (MVAr) .0000

Injections P/Q (MW/MVAr) 2.3238 -.1707

****************************************************************

results for bus number 2

voltage(pu) 1.0450 angle(deg) -4.9830

flow to (MW/MVAr) 1 -1.5259 .3056

flow to (MW/MVAr) 3 .7325 .0595

flow to (MW/MVAr) 6 .5629 -.0027

flow to (MW/MVAr) 8 .4136 .0243

line charging (MVAr) -.0917

shunt injection (MVAr) .0000

Injections P/Q (MW/MVAr) .1830 .2950

****************************************************************

Power Flow Results

SUMMARY

********************************************************

total generation P/Q (MW/MVAr) 2.5068 .4081

total load P/Q (MW/MVAr) -2.3730 -.3510

system losses P/Q (MW/MVAr) -.1339 -.5522

total charging (MVAr) .2830

total shunt power (MVAr) .2122

********************************************************

OR You can print them in IEEE Format exactly same as input

So that other programs can read it easily


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Objective : Optimize the system parameters

for better performance

Inputs : System information (parameters & connectivity)load and generation profile, set-points(V, t, MW)

component modeling and constraints

Output : Voltage profile (voltage magnitude and angles)Optimized power flow calculations

Violations (V, MW, MVAr) remaining

Major difficulty :Getting well-behaved objective function and

constraints as function of control variables

Optimal Power Flow


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Objective :

Minimize PLOSS

or Overload Alleviations

Subject to :

Satisfaction of load flow equations (Power Balance)

Limits on the control variables (set-points)Limits on line/transformer loading

Maintain Load Generation Balance

Control Variables :

Real Power Controls :

MW Gen, Tie-Line Flows, HVDC/FACTS set-points

Reactive Power Controls

Generator voltage set-points

VAr resources (Capacitors, Reactors, SVCs, Syn. condensers)

Transformer taps

HIGHLY NON-LINEAR PROBLEM Solved using Gradient, SLP or any other method

Problem Formulation


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LOSS REDUCTION

REAL POWER LOSSES

(UNOPTIMISED)BSH_14=0.0

0.2893 p.u.

1.060.003.36 + j 0.41

1.015-6.990.256 + j 0.322

0.98-23.6

-0.085 - j 0.022

0.97-23.7-0.189 - j 0.0812

0.94-24.88

-0.209 - j 0.078

0.983-23.0-0.049 - j 0.025 0.97-23.3

-0.126 - j 0.0812

0.96-18.88-1.319 + j 0.134

0.97-12.67

-0.106 - j 0.025

1.0-22.27-0.15 + j 0.13

1.037-20.2800 + j .24

0.96-15.03-0.67 + j 0.054

1.057-15.3-0.295 - j 0.166

2.28+j0.19

-2.18+j0.08

0.80+j0.08

1.05+j0.15

0.59+j0.09-0.57-j0.03

-1.02-j0.03

0.88-j0.10

1.08+j0.27

-0.87+j0.14

-0.77+j0.0280.33-j0.08

-0.32+j0.10-0.99+j0.065

0.226+j0.041

-0.23-j0.01

0.11+j0.039

-0.107-j0.036

0.022+j0.013

0.247+j0.11

-0.24-j0.104-0.07 - j 0.03

-0.022-j0.013 0.073+ j0.036

0.091+j0.062

BSH_14 = 0.00

C

Power Flow Base case


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LOSS REDUCTION

REAL POWER LOSSES

(UNOPTIMISED)

BSH_14=0.0

0.2893 p.u.

REAL POWER LOSSES

(OPTIMISED)

BSH_14=0.05

0.2854 p.u.

Loss Reduction

1.35%

1.060.003.35 + j 0.34

1.018-7.010.256 + j 0.322

0.995-23.42-0.085 - j 0.022

0.99-23.54-0.189 - j 0.0812

0.97-24.86-0.209 - j 0.078

0.997-22.8-0.049 - j 0.025 0.99-23.1

-0.126 - j 0.0812

0.96-18.82

-1.319 + j 0.134

0.98-12.68-0.106 - j 0.025

1.02-22.09-0.16 + j 0.13

1.048-20.1800 + j .24

0.97

-15.02-0.67 + j 0.054

1.057-15.3-0.295 - j 0.166

2.27+j0.15

-2.18+j0.13

0.80+j0.07

1.04+j0.14

0.59+j0.08-0.57-j0.018

-1.02-j0.006

0.88-j0.12

1.08+j0.25

-0.87+j0.14

-0.77+j0.0450.33-j0.08

-0.32+j0.10-0.99+j0.073

0.226+j0.028

-0.23-j0.003

0.10+j0.035

-0.106-j0.032

0.021+j0.009

0.244+j0.098

-0.24-j0.09

-0.07 - j 0.03

-0.021-j0.009 0.072+ j0.017

0.091+j0.061

CBSH_14 = 0.05

OPF Loss Minimization


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1.060.002.90 + j 0.28

1.025-5.820.68 + j 0.322

0.992-22.42-0.085 - j 0.022

0.98-22.5-0.189 - j 0.0812

0.97-24.86-0.209 - j 0.078

0.994-21.8-0.049 - j 0.025 0.98-22.1-0.126 - j 0.0812

0.97-17.61-1.319 + j 0.134

0.98-11.72-0.106 - j 0.025

1.014-21.11-0.16 + j 0.13

1.048-19.1200 + j .24

0.97-13.95

-0.67 + j 0.054

1.00-21.73-0.413 - j 0.232

1.897+j0.104

-1.835+j0.086

0.83+j0.083

1.059+j0.148

0.62+j0.09-0.60-j0.027

-0.952-j0.026

0.85-j0.11

1.00+j0.24

-0.84+j0.14

-0.79+j0.0330.32-j0.08

-0.31+j0.10-1.01+j0.068

0.23+j0.039

-0.23-j0.008

0.11+j0.039

-0.107-j0.036

0.022+j0.013

0.244+j0.113

-0.24-j0.10-0.07 - j 0.03

-0.021-j0.013 0.072+ j0.036

0.090+j0.062

Overload Min

REAL POWER FLOWS

(UNOPTIMISED)

1 2 2.27

1 5 1.08G1 = 3.35

G2 = 0.256

REAL POWER FLOWS

(OPTIMISED)

1 2 1.897

1 5 1.00

G1 = 2.90

G2 = 0.68

OPF Overload Alleviation


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1.060.003.35 + j 0.34

1.018-7.010.256 + j 0.322

0.995-23.42-0.085 - j 0.022

0.99-23.54-0.189 - j 0.0812

0.97-24.86-0.209 - j 0.078

0.997-22.8-0.049 - j 0.025 0.99-23.1

-0.126 - j 0.0812

0.96-18.82

-1.319 + j 0.134

0.98-12.68-0.106 - j 0.025

1.02-22.09-0.16 + j 0.13

1.048-20.1800 + j .24

0.97-15.02-0.67 + j 0.054

1.057-15.3-0.295 - j 0.166

2.27+j0.15

-2.18+j0.13

0.80+j0.07

1.04+j0.14

0.59+j0.08-0.57-j0.018

-1.02-j0.006

0.88-j0.12

1.08+j0.25

-0.87+j0.14

-0.77+j0.0450.33-j0.08

-0.32+j0.10-0.99+j0.073

0.226+j0.028

-0.23-j0.003

0.10+j0.035

-0.106-j0.032

0.021+j0.009

0.244+j0.098

-0.24-j0.09

-0.07 - j 0.03

-0.021-j0.009 0.072+ j0.017

0.091+j0.061

CBSH_14 = 0.05

Voltage Alleviation

Voltage V_14

(UNOPTIMISED)

BSH_14=0.0

0.94 p.u.

Voltage V_14

(OPTIMISED)

BSH_14=0.05

0.97 p.u.

OPF Voltage Alleviation


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Objective :

Evaluation of the system performance under outages

Inputs :System information (Parameters and connectivity info)

Load and generation profile, voltage set-points

Component modeling, Rating of the equipment

Output :

List of CRITICAL contingencies leading to violations

Approach :Approximate simulation



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Ranking

(Based on Per. Indices)

SystemInformation and

Base CaseState Estimator

Print results

Ranking List

Power Flow results forTop ranked outages

AnalysisFull Evaluation of Severe

Outages

List of credibleoutages (having

more probability ofoccurrence)

Efficient Screening

Contingency Analysis Flow Chart


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Possible outages :

All lines, transformers, generators, shunts, loads

For 14 bus sample system,Total number of single component outages

17 lines + 3 transformers + 2 generators + 3 shunts

TOTAL = 25 + (?multiple outages?)

WHAT IF the System size is 1000 buses?

Challenge : 1500 AC load flow simulations of 1000 bus system

Take considerable time

Contingency Analysis possible contingencies


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Filtering/Screening Criteria

1. Probability of occurrence

2. Use of approx. analysis like

Power flow with less tolerance

Power flow 1 iteration, esp. for overload analysis

Network equivalents (outage impact - local)

Ranking SEVERE contingencies based on

performance indices

- overload index

- voltage index

Full AC power flow analysis

for top ranked contingencies

Processing Approach

1500

150

15

Possible CTGs

Credible CTGs

Severe

CTGs


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Normally used performance Indices

- overload index

- voltage index

- Based on Type of limit violated and % violations

Index = 1000 x Type of limit violated

+ (100 + %violation)

e.g. Emergency limit violated by 12%Index = 2112

2

1 max_

_ =

=

nline

j lj

lj

overloadi

f

fP

2

1 max_

_ =

=

nbus

jj

j

voltageiV

VP

Severity Indices

Limits Type

1 Normal

2 Emergency

3 LoadShed


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1.060.002.32 - j 0.17

1.045-4.980.183 + j 0.295

1.055-15.67-0.061 - j 0.016

1.05-15.73-0.135 - j 0.058

1.035-16.47-0.149 - j 0.056

1.057-15.3-0.035 - j 0.018 1.052-15.51

-0.09 - j 0.058

1.01-12.73-0.942 + j 0.44

1.021-8.77-0.076 - j 0.018

1.07

-14.83-0.112 + j 0.068

1.09-13.6600 + j .172

1.02-10.34-0.478 + j 0.039

1.057-15.3-0.295 - j 0.166

1.57-j0.17

-1.53+j0.31

0.56-j0.003

0.73+j0.06

0.42+j0.02-0.40+j0.003

-0.73+j0.053

0.63-j0.14

0.75+j0.06

-0.62+j0.16

-0.55+j0.0540.24-j0.36

-0.23+j0.045-0.71+j0.038

0.16-j0.003

-0.17+j0.017

0.077-j0.026

-0.076-j0.025

0.015+j0.01

0.17+j0.075

-0.17-j0.08

-0.015-j0.01 0.051+ j0.02

0.065+j0.038

Base Case Power Flow Results


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1.060.002.75 - j 0.13

1.025-5.91-0.217 - j 0.127

1.055-16.67-0.061 - j 0.016

1.05-16.73-0.135 - j 0.058

1.033-17.47-0.149 - j 0.056

1.056-16.3-0.035 - j 0.018 1.05-16.51

-0.09 - j 0.058

1.01-14.00-0.942 + j 0.20

1.012-9.66-0.076 - j 0.018

1.07

-15.84-0.112 + j 0.113

1.09-14.6700 + j .194

1.01-11.34-0.478 + j 0.039

1.053-16.3-0.295 - j 0.166

1.92+j0.09

-1.86+j0.10

0.53-j0.065

0.726-j0.04

0.38-j0.036-0.37+j0.06

-0.80+j0.045

0.66-j0.16

0.83+j0.09

-0.65+j0.18

-0.52+j0.1140.24-j0.085

-0.24+j0.097-0.70+j0.14

0.16-j0.011

-0.17+j0.026

0.077+j0.076

-0.0767-j0.025

0.016+j0.01

0.17+j0.078

-0.17-j0.07

-0.016-j0.01 0.053+ j0.03

0.067+j0.044

Example - Generator Outage

Dr Shekhar Kelapure

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1.060.002.33 - j 0.10

1.045-4.490.183 + j 0.219

1.055-17.4-0.061 - j 0.016

1.05-17.45-0.135 - j 0.058

1.034-18.06-0.149 - j 0.056

1.056-16.9-0.035 - j 0.018 1.05-17.05

-0.09 - j 0.058

1.01-13.25-0.942 + j 0.078

1.011-10.66-0.076 - j 0.018

1.07

-16.6-0.112 + j 0.117

1.09-15.100 + j .187

1.012-11.66-0.478 + j 0.039

1.055-16.8-0.295 - j 0.166

1.42-j0.14

-1.38+j0.25

0.75-j0.006

0.82+j0.05

0.0+j0.00.0+j0.0

-0.87+j0.074

0.38-j0.14

0.91+j0.09

-0.38+j0.15

-0.72+j0.0960.149-j0.42

-0.148+j0.046-0.79+j0.072

0.16-j0.003

-0.17+j0.025

0.076-j0.027

-0.0754-j0.026

0.014+j0.01

0.17+j0.079

-0.17-j0.08-0.046 - j 0.026

-0.014-j0.01 0.046+ j0.03

0.057+j0.046

Example Line outage


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Objective :

Evaluate optimal set-points to bring the system back to

normal state in post contingency scenario

Inputs :System information (Parameters and connectivity info)

Load and generation profile, voltage set-points

Component modeling and constraints

List of severe contingencies

output :

Post Contingency complex voltage profile (V, )

Power flow calculations

(after implementing optimized controls)

Two Approaches:Preventive Action

Corrective Action

Security Constrained Optimization


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Objective : min Overloads OR Voltage excursions

subject to : Satisfaction of load flow equations

Limits on the control variables (set-points)


Minimum deviation in set-points

Pre and post outage(each severe outage) constraints

Control Variables :

1. Generator voltage setpoints

2. VAr resources (capacitors, reactors, SVCs, syn. condensers)

3. Transformer Taps

4. Generations (MW)

5. Tie-Line Flows, HVDC/FACTs controllers

SCO Preventive Action (PA)


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Challenges :

Single Big problem

Large number of constraints

(considering all outages together)

Conflicts between constraints

May lead to infeasible solution

Costly (Contingency may not happen at all)

Then WHY?

For some severe contingencies, post-outage controls

rescheduling may not be possible due to time limitations

Preventive Action - Challenges


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Objective : min Overloads OR Voltage excursions

subject to : Satisfaction of load flow equations

Limits on the control variables (set-points)


Minimum deviation in set-points

Only Post outage constraints for specific contingency

Control Variables :1. Generator voltage setpoints

2. VAr resources (capacitors, reactors, SVCs, syn. condensers)

3. Transformer Taps

4. Generations

5. Tie-Line Flows, HVDC/FACTs controllers

SCO Corrective Action


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Advantages :

Since occurrence of contingency is NOT certain, keeping

post contingency plans ready is better (Preparedness)

Separate optimization problem for each outage case

Sometimes it may NOT be possible to make changes after

outage

Challenges :

Post contingency scenario Time is crucial

Whether to go for PA/CA?For severe contingencies where the execution of CA is not

possible, then check the probability and consequences and

implement PA

Corrective Action


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Load Forecast

Objective :

To get the accurate forecast of system/ area loads

Inputs :

Load History (Normally stored from actual SCADA data)

Loads are function Weather data

Effective weather forecast

Weather history data

Formula to get derived forecast variable

Planning Inputs


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Load Forecast Types

Short Term:

Forecast Load for next hour (for every 5 mins)

Forecasting Emergencies in Operations (Real Time)

Medium Term

Forecast Load for a week (hourly forecast)

Normally used in operations (daily planning)

Long Term

Forecast Load for > 1 Year (monthly forecast)

Normally used in Planning


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Load Forecast Methodologies

Regression Technique:

Based on Historical load data and weather forecast

Similar day forecast

Based on the similar weather day in history

Load Patterns (Save cases)

Saved Load curved in history can be used to forecast

With appropriate scaling/shifting etc


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Regression Analysis

Daily Load Curve :

Weekly Load Curve :


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Regression Technique

Important to Note :

Load curved are cyclic in nature over the week

(e.g. Load pattern is similar on all Mondays)

With appropriate Load growth (say 12% over year)

Thus Regression Technique can effectively be used

Challenges :

Loads are highly dependent on weather (Rains?)

Special days (festivals have different load patterns)

Planning impact can not be handled


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Similar Day Forecast

Advantage :

Takes care of weather dependencies

Procedure :

- Get the weather forecast for the selected day

- Identify similar weather day in history

(closest match)

- take it as base load and apply load growth

Easy and more accurate for the weather sensitive loads


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d li i

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Load Forecast Applications

Power System Planning

As Pseudo Measurements in State Estimator

Power Flow Simulation Studies

Generation Applications

Unit Commitment

Hydrothermal Scheduling

Maintenance Scheduling

Awareness of worst situations and Readiness


L d F S

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Load Forecast - Summary

Load Forecast highly dependent on

Historical Data

Weather Data/ forecast

Types of Load Forecast

All techniques (regression + similar day + load patterns) need to beeffectively used to get better results

Other techniques : Artificial Neural Network etc.

For Long terms Load Forecasting

Appropriate Load growth and the planning indices are crucial


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