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ENERGY MANAGEMENT SYSTEMOverview
April 20, 2023
Dr Shekhar KELAPURE
PSTI, Bangalore
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
Load Dispatch
Objective -> Operate/Drive the Power System
so that it is Stable
Reliable
Secure
OPTIMAL
Operate Power System “Efficiently”
What’s so big
3Dr Shekhar Kelapure
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 capture
“system knowledge” and “situation awareness”
And provide key indicators
4Dr Shekhar Kelapure
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 software programs and provide “key indicators”
Display data/measurements on “meaningful” displays
Send control commands
to operate the system “efficiently”
What is Energy Management System?
5Dr Shekhar Kelapure
DatabasesDatabases
Components of EMS
Presentation Layer
(DISPLAYS)
Presentation Layer
(DISPLAYS)
Automatic Generation Control
Automatic Generation Control
Economic DispatchEconomic Dispatch
Reserve/Cost Monitoring
Reserve/Cost Monitoring
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
Network Application FunctionsObjective – Analyze Power System performance from network (transmission and generation) perspective
To check
Base case violations
Optimal performance (Loss Minimization etc.)
Security Assessment & Enhancement
Fault Analysis
What we need –
“GOOD” measurements – Load, Gen, Flows info.
Transmission System Data – Capacities, R, X, B, Tap etc
Generation Data – Ratings & other parameters7Dr Shekhar Kelapure
NA Functions – used in EMS State Estimator
To identify Anomalies
Power Flow & Optimal Power Flow
To carry out simulations
To get optimal set-points
Contingency Analysis
What if Analysis (N-1, N-2 etc)
Security Assessment and Enhancement
Assessment and corrective actions
Load Forecast – Input to Simulations (NA functions)8Dr Shekhar Kelapure
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 detailsFormation of networks (Island wise)Mark viable islands (with Generation)
Network Topology
9Dr Shekhar Kelapure
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
BUS1CB4
BUS2CB1
BUS2CB2
BUS2CB3
10Dr Shekhar Kelapure
Network Topology – Node Terminology
Secondary bus
Primary bus
Bus Couplers
Incomer #2Incomer #1
Outgoing #1 Outgoing #2
Nodes with Unique ID
11Dr Shekhar Kelapure
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+j0.054
0.24-j0.36
-0.23+j0.045-0.71+j0.038
0.16-j0.003
-0.17+j0.0170.077-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 FLOWS
GENERATIONS
VOLTAGES (ANGLES?)
FREQUENCY
Real-Time Data superimposed on Line Network
12Dr Shekhar Kelapure
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
13Dr Shekhar Kelapure
Objective : Identify and correct Anomalies, Suppress Bad dataRefine 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
14Dr Shekhar Kelapure
State EstimatorRefine Measurements
System Info, Measurements and
switch statuses Network Topology
NO
Observable? Add Pseudo Measurements
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
15Dr Shekhar Kelapure
Measurements Bus Voltages Magnitudes (V) and AnglesGenerations (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 processLess Measurements – erroneous results (poor estimation)
Optimum - 1.5 to 2.8 times the state variables
Measurements
16Dr Shekhar Kelapure
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+j0.054
0.24-j0.360
0.23+j0.0450+j0
0.16-j0.003
-0.17+j0.0170+-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 P32
Q34 AND Q43
LOADS
P12
Q12
V12
Identify Measurement Errors
17Dr Shekhar Kelapure
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+j0.054
0.24-j0.360
0.23+j0.0450+j0
0.16-j0.003
-0.17+j0.0170+-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 = 0.0
Q12 = 0.0
V12 = 0.0
IGNORE
OR
REPLACE WITH
APPROPRIATE VALUES
18Dr Shekhar Kelapure
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+j0.0170+-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
19Dr Shekhar Kelapure
1.06 0.002.32 - 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+j0.054
0.18-j0.360
-0.17+j0.0450+j0
0.18-j0.003
-0.17+j0.0170+-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 1.0600.001 1.044-4.9801 1.012-12.731 1.020-10.34Power 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
20Dr Shekhar Kelapure
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 1.56
1 5 0.75 0.65
2 1 –1.53 –1.52
2 4 0.56 0.55
2 5 0.42 0.41
1.06 0.002.32 - 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+j0.054
0.18-j0.360
-0.17+j0.0450+j0
0.18-j0.003
-0.17+j0.0170+-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
Bad Data Identification
21Dr Shekhar Kelapure
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+j0.054
0.24-j0.36
-0.23+j0.045-0.71+j0.038
0.16-j0.003
-0.17+j0.0170.077-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
22Dr Shekhar Kelapure
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+j0.054
0.24-j0.36
-0.23+j0.045-0.71+j0.038
0.16-j0.003
-0.17+j0.0170.077-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
23Dr Shekhar Kelapure
Objective : To compute the power flow in the branchesthru the complex voltages for given load/ generation profile
Inputs : system information component parameters and connectivityload and generation profile, voltage set-points
output : voltage profile (voltage magnitude and angles)power flow calculationsloss calculationviolations (voltage magnitude and power flows) “MODELLING IS CRUCIAL”
Power Flow
24Dr Shekhar Kelapure
Kirchhoff’s 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
jjii
YVVQ
YVVP
sin
cos
1
1
Vi ith bus
To bus 1
V1
To bus j
Vj
To bus k
Vk
Yii
YijYi1 Yik
Power Flow – Basic equations
25Dr Shekhar Kelapure
Non-linear eqnsLinearize & solve Iteratively
CharacteristicsQuadratic ConvergenceNormally 3-5 iterationsReliable
Difficulty - Handling Large Matrices MISMATCHJACOBIAN
UPDATE
NBUSNBUSNBUS
NBUS
Q
P
VQQ
VPP
V
VV
QQV
PP
Q
P
1
Newton Raphson based Power Flow
What’s way out? Try de-coupling ?FDLF?
QVQV
PP
1
1
Assumptions
1. |V| ~ 1.0 p.u.
Bus angle ) very small2. Sin()=0 3. Cos()=1 4. R << X
26Dr Shekhar Kelapure
OUTPUT
SLK – Pgen , Qgen
PV - δ , Qgen
PQ - δ , |V|
In addition
Branch Pflow , Qflow
LOSSES PL , QL
SHUNT POWER
Power Flow, Inputs and OutputINPUTS
System DATA
LINE DETAILS(RXB)
XMER DETAILS(RXT)
GENERATOR DATA(QLT)
SHUNT DATA(B)
LOAD/GEN DATA
LOAD DATA
GENERATION DATA(PV)
TUNING PARAMETERS
27Dr Shekhar Kelapure
08/19/93 UW ARCHIVE 100.0 1962 W IEEE 14 Bus Test Case
BUS DATA FOLLOWS 14 ITEMS
1 Bus 1 HV 1 1 3 1.060 0.0 0.0 0.0 232.4 -16.9 0.0 1.060 0.0 0.0 0.0 0.0 0
2 Bus 2 HV 1 1 2 1.045 -4.98 21.7 12.7 40.0 42.4 0.0 1.045 50.0 -40.0 0.0 0.0 0
3 Bus 3 HV 1 1 2 1.010 -12.72 94.2 19.0 0.0 23.4 0.0 1.010 40.0 0.0 0.0 0.0 0
4 Bus 4 HV 1 1 0 1.019 -10.33 47.8 -3.9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0
5 Bus 5 HV 1 1 0 1.020 -8.78 7.6 1.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0
6 Bus 6 LV 1 1 2 1.070 -14.22 11.2 7.5 0.0 12.2 0.0 1.070 24.0 -6.0 0.0 0.0 0
7 Bus 7 ZV 1 1 0 1.062 -13.37 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0
8 Bus 8 TV 1 1 2 1.090 -13.36 0.0 0.0 0.0 17.4 0.0 1.090 24.0 -6.0 0.0 0.0 0
9 Bus 9 LV 1 1 0 1.056 -14.94 29.5 16.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.19 0
10 Bus 10 LV 1 1 0 1.051 -15.10 9.0 5.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0
-999
BRANCH DATA FOLLOWS 20 ITEMS
1 2 1 1 1 0 0.01938 0.05917 0.0528 0 0 0 0 0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
1 5 1 1 1 0 0.05403 0.22304 0.0492 0 0 0 0 0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
2 3 1 1 1 0 0.04699 0.19797 0.0438 0 0 0 0 0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
2 4 1 1 1 0 0.05811 0.17632 0.0340 0 0 0 0 0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
2 5 1 1 1 0 0.05695 0.17388 0.0346 0 0 0 0 0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
3 4 1 1 1 0 0.06701 0.17103 0.0128 0 0 0 0 0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
4 5 1 1 1 0 0.01335 0.04211 0.0 0 0 0 0 0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
4 7 1 1 1 0 0.0 0.20912 0.0 0 0 0 0 0 0.978 0.0 0.0 0.0 0.0 0.0 0.0
4 9 1 1 1 0 0.0 0.55618 0.0 0 0 0 0 0 0.969 0.0 0.0 0.0 0.0 0.0 0.0
5 6 1 1 1 0 0.0 0.25202 0.0 0 0 0 0 0 0.932 0.0 0.0 0.0 0.0 0.0 0.0
6 11 1 1 1 0 0.09498 0.19890 0.0 0 0 0 0 0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
6 12 1 1 1 0 0.12291 0.25581 0.0 0 0 0 0 0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
6 13 1 1 1 0 0.06615 0.13027 0.0 0 0 0 0 0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
-999
END OF DATA
IEEE Format
28Dr Shekhar Kelapure
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 .0390
7 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
29Dr Shekhar Kelapure
Objective : Optimize the system parametersfor 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 calculationsViolations (V, MW, MVAr) – remaining
Major difficulty : Getting well-behaved objective function and constraints as function of control variables
Optimal Power Flow
30Dr Shekhar Kelapure
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 loadingMaintain Load Generation Balance
Control Variables :Real Power Controls :
MW Gen, Tie-Line Flows, HVDC/FACTS set-points
Reactive Power ControlsGenerator voltage set-pointsVAr resources (Capacitors, Reactors, SVCs, Syn. condensers)Transformer taps
HIGHLY NON-LINEAR PROBLEM – Solved using Gradient, SLP or any other method
Problem Formulation
31Dr Shekhar Kelapure
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+j0.028
0.33-j0.08
-0.32+j0.10-0.99+j0.065
0.226+j0.041
-0.23-j0.010.11+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 = 0.00C
Power Flow Base case
32Dr Shekhar Kelapure
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+j0.045
0.33-j0.08
-0.32+j0.10-0.99+j0.073
0.226+j0.028
-0.23-j0.0030.10+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
C BSH_14 = 0.05
OPF – Loss Minimization
33Dr Shekhar Kelapure
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+j0.033
0.32-j0.08
-0.31+j0.10-1.01+j0.068
0.23+j0.039
-0.23-j0.0080.11+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 1.08
G1 = 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
34Dr Shekhar Kelapure
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+j0.045
0.33-j0.08
-0.32+j0.10-0.99+j0.073
0.226+j0.028
-0.23-j0.0030.10+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
C BSH_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
35Dr Shekhar Kelapure
Objective : Evaluation of the system performance under outages
Inputs : System information (Parameters and connectivity info)Load and generation profile, voltage set-pointsComponent modeling, Rating of the equipment
Output : List of CRITICAL contingencies leading to violations
Approach :Approximate simulation
Contingency Analysis
36Dr Shekhar Kelapure
Ranking
(Based on Per. Indices)
System Information and
Base Case State Estimator
Print results
Ranking List
Power Flow results for Top ranked outages
AnalysisFull Evaluation of Severe
Outages
List of credible outages (having
more probability of occurrence)
Efficient Screening
Contingency Analysis – Flow Chart
37Dr Shekhar Kelapure
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 shuntsTOTAL = 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
38Dr Shekhar Kelapure
Filtering/Screening Criteria1. Probability of occurrence2. 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
SevereCTGs
39Dr Shekhar Kelapure
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
ljoverloadi f
fP
2
1 max__
nbus
j j
jvoltagei V
VP
Severity Indices
Limits Type1 – Normal2 – Emergency3 – LoadShed
40Dr Shekhar Kelapure
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+j0.054
0.24-j0.36
-0.23+j0.045-0.71+j0.038
0.16-j0.003
-0.17+j0.0170.077-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
41Dr Shekhar Kelapure
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+j0.114
0.24-j0.085
-0.24+j0.097-0.70+j0.14
0.16-j0.011
-0.17+j0.0260.077+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
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+j0.096
0.149-j0.42
-0.148+j0.046-0.79+j0.072
0.16-j0.003
-0.17+j0.0250.076-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
43Dr Shekhar Kelapure
Objective : Evaluate optimal set-points to bring the system back to
normal state in post contingency scenarioInputs :
System information (Parameters and connectivity info)Load and generation profile, voltage set-pointsComponent modeling and constraintsList of severe contingencies
output : Post Contingency complex voltage profile (V, )Power flow calculations(after implementing optimized controls)
Two Approaches:Preventive ActionCorrective Action
Security Constrained Optimization
44Dr Shekhar Kelapure
Objective : min Overloads OR Voltage excursions
subject to : Satisfaction of load flow equationsLimits on the control variables (set-points)Maintain Load Generation BalanceMinimum deviation in set-pointsPre and post outage(each severe outage) constraints
Control Variables :1. Generator voltage setpoints2. VAr resources (capacitors, reactors, SVCs, syn. condensers)3. Transformer Taps 4. Generations (MW)5. Tie-Line Flows, HVDC/FACTs controllers
SCO – Preventive Action (PA)
45Dr Shekhar Kelapure
Challenges : Single Big problemLarge number of constraints
(considering all outages together)
Conflicts between constraintsMay lead to infeasible solutionCostly (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
46Dr Shekhar Kelapure
Objective : min Overloads OR Voltage excursions
subject to : Satisfaction of load flow equationsLimits on the control variables (set-points)Maintain Load Generation BalanceMinimum deviation in set-pointsOnly Post outage constraints for specific contingency
Control Variables :1. Generator voltage setpoints2. VAr resources (capacitors, reactors, SVCs, syn. condensers)3. Transformer Taps 4. Generations5. Tie-Line Flows, HVDC/FACTs controllers
SCO – Corrective Action
47Dr Shekhar Kelapure
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
48Dr Shekhar Kelapure
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
49Dr Shekhar Kelapure
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
50Dr Shekhar Kelapure
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
51Dr Shekhar Kelapure
Regression Analysis
Daily Load Curve :
Weekly Load Curve :
52Dr Shekhar Kelapure
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
53Dr Shekhar Kelapure
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
54Dr Shekhar Kelapure
Load Patterns
Advantage :
This can handle exceptions
i.e. special days like festivals
Procedure :
- Save the load patterns for the special days
- take it as base load and apply load growth
Easy and more accurate for the special days loads
55Dr Shekhar Kelapure
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
56Dr Shekhar Kelapure
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 be effectively 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
57Dr Shekhar Kelapure