View
222
Download
0
Category
Preview:
Citation preview
7/28/2019 US Africa Abuja Ajjarapu
1/46
Power System Voltage Control and
StabilityV. Ajjarapu (vajjarap@iastate.edu)Iowa State University
Ames, USA
Third NSF Workshop on US-Africa
Research and Education Collaboration
Abuja, Nigeria, December 13-15, 2004
TECHNOLOGY &
ENVIRONMENT
ENERGY &
EDUCATION
TECHNOLOGY &
ENVIRONMENT
ENERGY &
EDUCATION
7/28/2019 US Africa Abuja Ajjarapu
2/46
Outline Introduction
Aim
Educators Involved
Area of Research POWER SYSTEM SECURITY AND CONTROL An Overview
Medium of Interaction Web based
Travel
Activities Planned
7/28/2019 US Africa Abuja Ajjarapu
3/46
Our Department
48 faculty
Power: 4 + 2
Over 30 power graduate students Typical undergraduate power class: 50
Mainly power systems: Security and
dynamics , risk analysis, economics andmarkets
State of the art power electronics lab
7/28/2019 US Africa Abuja Ajjarapu
4/46
Aim
Building African collaboration with ISU
researchers to build further understanding
of different power system case studies.
Developing a roadmap for future research
activities in power / energy, information
systems technology, environmental and
social dynamics, and education pedagogy
7/28/2019 US Africa Abuja Ajjarapu
5/46
Educators Involved
Prof. George O. Anderson, Univ. of
Botswana
Dr. Tanimu Abubakar, Ahmadu Bello
University, Zaria, Nigeria
Dr. Venkataramana Ajjarapu (with
support from EPNES ISU faculty)
Graduate/Undergraduate Students from
these Universities
7/28/2019 US Africa Abuja Ajjarapu
6/46
Research : POWER SYSTEM SECURITY AND
CONTROL:
Main Area of Expertise : Voltage Stability , Oscillatory
Stability, VAR Planning and dispatch , ATC :
Sub Area: Power Electronics and Real Time Control
The group is developing a comprehensive approach for voltage
and oscillatory stability analysis and control. This group is also
actively involved in the Available Transfer Capability(ATC)
evaluation as limited by voltage as well as oscillatory stability.Reactive power requirements and pricing required for deregulated
environment. These techniques will be applied to realistic
practical power networks.
7/28/2019 US Africa Abuja Ajjarapu
7/46
Our Groups Research
Overview Developing techniques that are very
effective for stressed power systems
A single tool can be adapted for cost
based security with timing of controlinformation
Available Transfer Capability (ATC) is part
of this research Web Based Security Tools for Distance
Education
7/28/2019 US Africa Abuja Ajjarapu
8/46
7/28/2019 US Africa Abuja Ajjarapu
9/46
7/28/2019 US Africa Abuja Ajjarapu
10/46
7/28/2019 US Africa Abuja Ajjarapu
11/46
Power Flow, CPF and EQTP
Conventional power flow program calculates
steady state solution for a given operating
condition.
Continuation power flow (CPF) traces a series ofpower flow solutions for a given scenario. You
can also trace the bottom of the PV curve.
Equilibrium Tracing Program (EQTP) is an
extension of CPF. DAE instead of pure powerflow equation is used to represent the power
system. It has the capability of detecting both
voltage and oscillatory instabilities.
7/28/2019 US Africa Abuja Ajjarapu
12/46
Security Margin Tracing
Illustration of voltage stability, oscillatory stability and damping ratio boundary
tracing
Damping ratio boundary for D= D0
Voltage stability margin boundary
Oscillatory stability margin boundary
A1A2
Predictor
Corrector
Parameter
Voltage
7/28/2019 US Africa Abuja Ajjarapu
13/46
Numerical results for Identification: CPF
7/28/2019 US Africa Abuja Ajjarapu
14/46
Example For Voltage Stability Boundary: Reactive
Power Variation
0 2 4 6 8 10 121200
1300
1400
1500
1600
1700
1800
shunt capacitance added at bus 8 (p.u.)
totalsystemloadmargin(MW)
7/28/2019 US Africa Abuja Ajjarapu
15/46
Optimal Margin Boundary
Tracing
7/28/2019 US Africa Abuja Ajjarapu
16/46
Basic Formulation
For a sequence of specified margin levels:
Minimize a cost function : f(U)
Subject to : Equality Conditions : F, G
Inequality constraints : IOptimality conditions :
Margin boundary conditions : Cobt
Results in a set of nonlinear equations of the form:
0
,...),,(
),,,,,(
),,,(
),,,(
xu
obt
hl
FfC
ssUYXI
UYXG
UYXF
7/28/2019 US Africa Abuja Ajjarapu
17/46
Formulation (Cont.)
The formulation could automatically generate
a whole set of cost based optimal control
configurations with each optimal control
configuration corresponding to specific
margin level that can be realized.
7/28/2019 US Africa Abuja Ajjarapu
18/46
Sample Result for OMBT
7/28/2019 US Africa Abuja Ajjarapu
19/46
Continuation Based Time
Domain Simulation
7/28/2019 US Africa Abuja Ajjarapu
20/46
Key Points
No divergence due to singularity of
Time step size is adjusted according to the
variation of dS/dt
Small time steps for fast dynamics and
large time steps for slow dynamics
7/28/2019 US Africa Abuja Ajjarapu
21/46
Trajectory Before and After a Line
Outage (with load variation)
0 20 40 60 80 100 120
0.94
0.945
0.95
0.955
0.96
0.965
0.97
0.975
0.98
0.985
time (sec)
volta
ge
ofBUS4
(p.u.)
Voltage Time Domain Trajectory
7/28/2019 US Africa Abuja Ajjarapu
22/46
QSS Simulation
0 50 100 150 200 2500.92
0.93
0.94
0.95
0.96
0.97
0.98
0.99
time (sec)
voltage
ofBUS4
(p.u.)
Voltage Time Domain Trajectory
7/28/2019 US Africa Abuja Ajjarapu
23/46
Overall Strategy
t
0 1 2 i
Scenario CredibleContingency Set
Cj{C1,C2, ,Cm}
No
No
Yes Yes
Trace Eigenvalue
for Hopf and
Damping Margin
Preventive
Control
Strategies
All Credible
Contingencies
Tested ?
Sufficient
Margin ?
j =j +1
i =i +1
Check for (A+AT)
singularity
Voltage stability margin
Oscillatory stability margin
Damping ration margin
(A+AT) singular
before SNB?
No
Yes
7/28/2019 US Africa Abuja Ajjarapu
24/46
Research Needs
On line monitoring :Fast calculations
Accuracy vs Speed
Timing Information: Fastvs Slow Collapse
Integration of Cost ofVoltage and OscillatoryStability Control inOverall Security
Assessment
7/28/2019 US Africa Abuja Ajjarapu
25/46
Optimal Strategies for Load Shedding :when, where and how much
7/28/2019 US Africa Abuja Ajjarapu
26/46
Capabilities at ISU
A method to quickly identifies voltage andoscillatory instability points.
The change in the instability margin
boundaries can be further obtained for any
large change in system parameters. Optimization and Time Domain Simulations
are part of Continuation Based Approach
An efficient eigenvalue tracking method isintroduced. Provides damping information
Provides eigenvalue and eigenvector sensitivity
information as a by product
7/28/2019 US Africa Abuja Ajjarapu
27/46
CapabilitiesCont..
Automatic PV Curve Tracing.
Field current and armature current limits are
included.
Provides true maximum power point byconsidering relevant dynamic factors.
There is no need for slack bus
Can solve unsolvable cases created by a lineor generator outages
7/28/2019 US Africa Abuja Ajjarapu
28/46
Capabilities Cont
Sensitivity Analysis (qualitative)
Screens the contingencies that may lead to
voltage collapse
Locates the weak areas , identifies the criticalgenerators
Provides voltage stability margin estimation
7/28/2019 US Africa Abuja Ajjarapu
29/46
Capabilities Cont..
Available Transfer Capability as Limited
by Voltage and Oscillatory Stability
Simulates simultaneous multi-area
transactions
Provides Transaction Sensitivity: Identifies
and ranks the transactions that are
detrimental to voltage stability Reactive power pricing /amount /location/ to
maintain voltage security
7/28/2019 US Africa Abuja Ajjarapu
30/46
Capabilities Cont..
Preventive and Corrective Strategies
Against the Voltage Collapse
Strategies for minimum load shedding
Strategies for under-voltage load shedding
Strategies to maintain a certain voltage
stability margin
7/28/2019 US Africa Abuja Ajjarapu
31/46
Capabilities Cont..
Development of Advanced Algorithms for
steady state, dynamic and time domain
simulations
A simulation engine that can allow transient
and quasi- steady state analysis
to obtain a comprehensive analysis to predict
and control instabilities When , where and how much control
7/28/2019 US Africa Abuja Ajjarapu
32/46
Capabilities Cont..
On Line Voltage Stability Monitoring and
Control:
Developing methodologies to utilize off line
studies for on line implementation
7/28/2019 US Africa Abuja Ajjarapu
33/46
Application to Botswana 32 Bus
Test System
7/28/2019 US Africa Abuja Ajjarapu
34/46
Botswana System (Cont..)
Demand : 243 MW
Supply
Local (coal): 128MW
ESKOM and SAPP : 115MWSimulation :
Software : Aristo (Advanced Real Time Interactive
Simulator for Training and Operation ) by ABB
Dr. Anderson applied this software for Power flow andFault analysis for 32 bus equivalent system
7/28/2019 US Africa Abuja Ajjarapu
35/46
Activities Planned wrt EPNES
Project (research)
Task 1: Setting up a test case for Botswana System
Task 2: Study the maximum loadability with respect
various contingencies and scenarios
Task 3: Apply margin sensitivity to find the
locations for shunt capacitors and series
capacitors
Task 4: Develop Automaton for backward algorithm
7/28/2019 US Africa Abuja Ajjarapu
36/46
Activities Planned (education)
Botswana group will participate in EE458
course
Develop I hour lecture material for this course
7/28/2019 US Africa Abuja Ajjarapu
37/46
1. Evolutionary history of the power industry; present industry structure;
2. Discrete optimization;
3. Power system operation;
4. Electricity markets;
5. Power system planning and cost-effective solutions;
6. Cost recovery for transmission investment; basics of public goodeconomics;
7. Cost-recovery models:
Tariff-based model; Performance-based model;
Market-driven model;
8. Tax treatment of transmission investments.
EE/Econ 458: Economic systems for planning in electric power
Students completing this course will be able to conduct studies in policy,
economics, & engineering associated with transmission expansion; they willenhance their skills using optimization methods for engineering & economic
problem-solving.
Will offer Fall 2004 on-campus, and via distance-education.
7/28/2019 US Africa Abuja Ajjarapu
38/46
Web Based
Interaction
7/28/2019 US Africa Abuja Ajjarapu
39/46
Characteristics
Platform (OS) Independent
Standardized System Input Files
Graphic PV Curves Output
Detailed Simulation Process Output
Margin Sensitivity
7/28/2019 US Africa Abuja Ajjarapu
40/46
Simulation Website
http://design-2.ece.iastate.edu/newsim/index.php
http://design-2.ece.iastate.edu/newsim/index.phphttp://design-2.ece.iastate.edu/newsim/index.phphttp://design-2.ece.iastate.edu/newsim/index.phphttp://design-2.ece.iastate.edu/newsim/index.php7/28/2019 US Africa Abuja Ajjarapu
41/46
Simulation Website Cont..
Input Files IEEE Common Data Format is adopted as the
input file for power system topology andparameters
Another standardized control file is used to
specify load and generation increase scenario
Sample Test System input files are provided
7/28/2019 US Africa Abuja Ajjarapu
42/46
Simulation Website Cont..
Upload Input Files
7/28/2019 US Africa Abuja Ajjarapu
43/46
Simulation Website Cont..
Download Sample Systems
7/28/2019 US Africa Abuja Ajjarapu
44/46
Multiple Simulation Outputs
Tabular Output
7/28/2019 US Africa Abuja Ajjarapu
45/46
Outputs Cont..
Graphic PV Curve
7/28/2019 US Africa Abuja Ajjarapu
46/46
Outputs Cont..
Generator Reactive Power Output
Recommended