Task Descriptions for the Voltage Security Margin Assessment Project
By Drs. G. Huang and A. Abur
Students: N. Nair , L. Zhao and H. Zhang,( not paid through this grant)
Task 1
Modeling of control devices, loads and transactions for stability evaluations.
Progress:


Modeling and effect of FACTS devices like TCSC, SVC and TCUL on voltage stability are
carried out. Please see attached papers on dynamic reserves and TCSC controllers.
Modeling of loads and effect of power factor on voltage stability carried out. It is observed that
different load models have significant impacts on the stability margin evaluation. Olease see the
attached report for details.
Subtasks:
1.1 Modeling FACTS devices
Input from industry: Network and device data. Insights about the dynamic and steady state operation of FACTS
devices.
Output: Report on how to incorporate FACTS device models into the stability margin calculations. Different
types of commonly used FACTS devices, such as TCSCs, UPFCs and SVCs will be investigated.
70% Finished: See attached report.
1.2
Modeling Tap-changing transformers for its reactive power drawing capability
Input from industry: Network and device data. Insights about the dynamic and steady state operation of tap
changing transformers.
Output: Report on how to incorporate tap-changing transformers models into the stability margin calculations.
70% Finished: See attached papers (dynamic reserve and TCSC controller)
1.3 Modeling exciters for its reactive power supporting and voltage regulating capability
Input from industry: Network and device data. Insights about the dynamic and steady state operation of tap
changing transformers.
Output: Report on how to incorporate exciter models into the stability margin calculations
70% Finished: See attached papers (dynamic reserve and TCSC controller)
1.4 Modeling loads
Input from industry: load-type data. Insights about the dynamic and steady state operation of different industrial
and consumer loads.
Output: Report on how to incorporate load models into the stability margin calculations.
40% Finished: See attached report.
1.5 Modeling transactions
Input from industry: load-type data. Insights about the dynamic and steady state operation of different industrial
and consumer loads.
Output: Report on how to incorporate load models into the stability margin calculations.
40% Finished: See attached paper (transaction based power flow)
Task 2
Use of Stability Margin and Stability Index Calculations
Progress

Voltage stability indicators, such as PV curves and L as an indicator in the report and index
paper, has been formulated and studied.

It is shown PV curves are not sufficient for indicators. For examples, resistance load, lighting
loads. etc., the lower part of the PV curve do not indicate instability. The system can sustain at
the lower curve.

The applicability of the indicator L for the various cases have been looked into and verified. It
has been found that the indicator L gives an information as regards to the stability margin from
the steady state voltage collapse point.

Some dynamic voltage stability situations are simulated using EUROSTAG and the
applicability of the index L investigated. It has been observed that L calculated on the simulated
data at the instance of the largest dip in the voltage at the load bus following a disturbance can
give information as regards to the voltage stability margin.

An OPF based algorithm to evaluate load curtailment incorporating voltage stability margin has
been formulated based on the proposed index L.
Subtasks:
2.1. Develop a program according to the new models to simulate the dynamic responses
Input from industry: Network data, scenarios of faults and new developed models
Output: Simulations to show effects of our modeled loads, transformers, controls, etc.
70% Finished: See attached paper (TCSC controller and index paper)
2.2. Analysis of Modeling Impacts
Input from industry: Network data , scenarios of faults, transactions and new developed models
Output: Investigation results. Applying various types of scenarios to observe the performance of the various
models on stability margins. Issues of stability indices, utilization indices, early stability indicators, will be
investigated and demonstrated.
40% Finished: Program (Mat based Prototype) developed. Need to do: correctness checking.
See attached report and index paper.
2.3. Use of stability indices as a transaction scheduler
Input from industry: Network and transaction data for power exchanges.
Output: Demonstrate the utilization of stability indices developed in 2.2 in suggesting allowed transactions to
maintain stability margins.
10% Finished: Collecting some information and theoretical preparing.
2.4
Use of utilization indices developed in 2.2 as basis for auxiliary service charges.
Input from industry: Capital costs for different control devices
Output: Demonstrate the effectives of control and basis for charges.
10% Finished: Collecting some information and theoretical preparing. Need to do: Begin to work.
2.5
Use of 2.4 results as equipment investment indicators based on 2.4 results
Input from industry: Capital costs for different control devices, considered locations
Output: Demonstrate the potential utilization and anticipated capital recovery rate.
Yet to begin!
2.6 Tests and documentation
Input from industry: Network, control and transaction data.
Output: Project report including test case results. Test results for base case and those cases with controls and
transactions.
Yet to begin!
Task 3
Transaction based stability margin and utilization factors calculation
Progress

A transaction based power flow (TBPF) analysis procedure has been developed.

A prototype program for TBPF has been developed in MATLAB

TBPF gives an accurate allocation for use-to-transmission among different market players. The
utilization of MW flows and, Mvar flows, MVA flows, transmission losses and reactive power
losses to bilateral transactions is part of the TBPF solution.

The TBPF is bound to have extensive potentials for the deregulated power market, such as loss
allocation, parallel flow evaluation, congestion management and settlement, reactive power
pricing, Flowgate and ATC assessment etc

High computation efficiency

With appropriate logic modification, common power flow programs embedded in EMS function
can be readily extended for TBPF purpose.
Subtasks
3.1 Formulate the transaction based power flow analysis problem
Input from industry: Insights about the loss allocations for bilateral transactions.
Output: Report on how to incorporate the loss into bilateral transactions.
70% finished! See attached paper (transaction based paper)
3.2 Develop software for transaction based power flow analysis for decompositions
Input from industry: Network data and transaction data.
Output: Associated flows with transactions.
50% finished! See attached paper (transaction based paper)
3.3 Develop software to calculate utilization factor for control equipments
Input from industry: Network data, transaction data and control data.
Output: Program that reads in network, control and transaction data to calculate the contribution and utilization
factors for each controls.
30% Finished: Developing some parts of program; Need to do: finish program work and check the correctness of the
program.
3.4 Develop software for finding decomposed utilization factors and stability margins for individual transactions.
Combining results from 3.2 and 3.3 to decompose the margins and utilization factors to individual transactions.
10% Finished: Collecting some information and theoretical preparing. Need to do: Begin to work.
3.5 Test case and documentation
Input from industry: Input the scenarios developed by task 2 to demonstrate the applications our developed
programs. Documentation of the developed software and test cases in form of reports and publications. Software
and its manual.
Yet to begin!
Task No:
1.1
1.2
1.3
1.4
1.5
2.1
2.2
2.3
2.4
2.5
2.6
3 mo
3 mo
70%
70%
70%
40%
40%
70%
80%
P
P
N
N
Schedule of Tasks
3 mo
3 mo
3 mo
CR
CR
CR
DCR
DCR
CR
C
R
B
B
P
B
P
3 mo
B
3 mo
3 mo
3.1
3.2
3.3
3.4
3.5
70%
50%
30%
P
N
D&C
B
C
R
P
P
B
P: Preparing some information and theory background
N: Not begin to work yet;
R: Report is needed;
C: Need to do some Correctness checking;
D: Develop the program
B: Begin to work
Desired Input from the Industry:


Real measurement data that records voltage stability scenarios for us to check if our L index will
correctly predict the problem.
Real measurement data that indicate PV curve monitoring do not work for lighting or resistance
loads. But we will demonstrate that our L indicator will work.