1. Use of Node-Breaker Model in POM Suite/ROSE Software
Presented by Marianna Vaiman, V&R Energy
West Wide System Model and Basecase Reconciliation Task Force (WBRTF)
WECC WebEx Meeting
August 22, 2012
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

2. V&R Energy V&R Energy’s services include:
Comprehensive software tools for analyzing power system behavior
Vendor of POM Suite and ROSE applications
Advanced consulting services
Cutting edge scientific research
V&R is located in Los Angeles, CA
I'm convinced you (plural) are the only ones in the industry giving the proper thought and attention to the problems that transmission operators and planners are trying to manage
American Transmission Co.
V&R Energy’s software allows us to do in 20 minutes what normally takes about seven hours with our present system
East Kentucky Power
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

3. Physical and Operational Margins (POM) Suite
Available for real-time and off-line computations
Extremely fast:
8 to 10 times faster than similar applications
Very reliable and robust solution engine
Very flexible scripting
Handles extremely large contingency/fault lists:
Millions of N-1-1, N-2 contingencies during one simulation run
Hundreds of thousands of faults during one simulation run
Automates and expedites NERC compliance studies
Predicts and prevents cascading outages
Offers a boundary-based solution
Automatically determines optimal corrective actions to mitigate exceeding operating limits
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

4. POM Suite - Planning
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

5. POM Suite Use in Planning
NERC-compliance studies:
NERC TPL Standards Compliance (TPL-003, TPL-004)
Steady State Analysis
Transient Stability Analysis
NERC FAC-014 Standard Compliance
Establishing System Operating Limits
NERC PRC-023 Standard Compliance
Identification of 100kV- 200kV transmission lines
NERC MOD-001, 004, 006, 007, 008, MOD-028, 029, 030
Available transfer capability
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

6. POM Suite Use in Planning (cont)
Voltage stability analysis
AC transfer/load pocket and contingency analyses with visualization
Determines available transfer capability for each contingency
Determines interface flows
Automatically builds PV-curves
Transmission system expansion analysis
Reliability analysis
Using results of POM-OPM to compute reliability indices
Phase-shifter settings optimization to relieve post-contingency violations
Analysis of cascading outages
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

7. POM Suite – Real Time/ROSE
Same algorithms for off-line and real-time analysis
Model-based & measurement-based State Estimator
Integrated voltage and transient stability analyses
Boundary-based solution
Automatic analysis of cascading outages
Automatic remedial actions to mitigate steady-state & transient stability violations
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

8. POM Applications in Real-Time
Uses of POM Suite in Real-Time include:
State Estimation,
Voltage stability analysis,
Massive AC contingency analysis with remedial actions
Use of PMU data to perform voltage stability analysis, predict instability and alarm operators
Predicting cascading outages
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

9. Role of the Node-Breaker Model in POM Suite
Bridges real-time and off-line analysis
POM Suite/ROSE reads analysis includes:
Reading of export file in node-breaker model
Performing necessary topology processing
Performing steady-state analysis:
Voltage stability analysis, AC contingency analysis, RAS implementation, determining remedial actions, etc.
Automatic conversion of the node-breaker model to bus-branch model in Siemens PSS/E .raw file format for use in planning analysis
Saves the full model
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

10. POM Suite Integration with Other Applications
Easy integration with other applications
Reads node-breaker and bus-branch models
Node-breaker:
Export (“flat”) files from an EMS system,
CIM-compatible
Bus-branch:
Power flow cases in PTI PSS/E rev , GE-PSLF version 17 (and earlier), PowerWorld *.aux format
Solves and converts cases to POM internal format
Modified power flow cases may be saved for future use
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

11. POM Program Functionalities
Main program of the Package
Performs power flow computations
Performs massive AC contingency analysis for large power system models:
Fast AC contingency analysis
Automatically generates contingency lists/reads existing lists
Analyzes N‑1, N-1-1, and N‑2 contingencies
Identifies critical contingencies and associated violations
Monitors user-defined constraints:
Simultaneously monitors voltage stability, voltage and thermal constraints
Computes voltage stability margins
Simulates power transfers while monitoring constraints
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

12. Modes of POM Operation Basic Mode Advanced Mode Automatic Mode
Easy, fast computation of a particular contingency, load scaling, simulation of a power transfer
Constraints are graphically displayed
Advanced Mode
Flexibility of analysis using POM commands
Constraints are graphically displayed
Automatic Mode
Massive contingency analysis
Script Mode
Complete control of computations and output
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

13. Determining Optimal Remedial Actions (System Adjustments)
Fast, powerful and efficient remedial actions tool
Automatically alleviates violations during massive AC contingency analysis
Increases operating margins
RAS is incorporated through scripting
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

14. Remedial Actions Used in OPM
Applies a minimum amount of mitigation measures based on a user-defined priority schedule
Available remedial actions include:
MW Dispatch
MVar Dispatch
Capacitor and Reactor Switching
Transformer Tap Change
Phase Shifter settings
Line Switching (In and Out)
Switching Not Affected Lines
Load Curtailment
Optimal Capacitor, Reactor Placement and Size
OPM Operating Procedures
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

15. Analysis of Extreme Events
Automated analysis
Analysis scenario:
Quantify a power system’s ability to withstand cascading outages due to thermal and/or voltage violations
Quickly identify initiating events that may lead to cascading events
Impractical to apply all N-k contingencies in a bulk power system
Automatically identify potential cascading modes
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

16. A Boundary-Based Solution
Automatically identifies the operating region that satisfies N-1/N-1-1/N-2 reliability criteria
Finds AC limits for transfer scenarios based on voltage stability, voltage constraints, and thermal constraints
Computes dynamic security region
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

17. Operating Region that Satisfies Reliability Criteria
Automatically determines the most limiting contingencies
Secure operating region may be formed by several contingencies
The area formed by the most limiting contingencies is the area that satisfies N-1 and/or N-2 reliability criteria
Power system is secure only when operating within this area
Can be used in real-time, on-line and planning environments
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

18. POM – Transient Stability (POM-TS)
Fast and user-friendly dynamic simulation – execution time for a one second simulation is approximately 6 seconds for a bus case and dynamic models
Fully integrated into POM
Supports Library of dynamic models in Siemens PTI’s PSS/E and GE’s PSLF formats
Allows for easy inclusion of user-defined models through use of POM scripting
Satisfies NERC/WECC criteria
Performs fast fault screening in order to determine the most severe three-phase and unbalanced faults in the system
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

19. ROSE – PMU-based Analysis
Region Of Stability Existence - ROSE defines the range of phasor measurements or other system parameters
For which the system may securely operate in terms of the accepted N-k security criteria
Addresses the problem of utilizing the PMU data to increase the situation awareness of the operators and improve stability and reliability of the electric grid
For steady-state analysis: voltage stability, voltage constraint (voltage range and/or pre-to post contingency voltage drop) and thermal overloads may be simultaneously monitored, enforced and visualized on the boundary
For steady-state stability has two inputs: node-breaker or bus-branch model
Combinatory approach
Combines model-based (State Estimator data) and measurement-based (PMU data) computations
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

20. Use of Node-Breaker Model for Steady-State Stability Analysis
POM Suite/ROSE is used for steady-state analysis in real-time and off-line environments, including:
Voltage stability analysis:
Runs multiple user-defined scenarios;
Computations performed for each scenario are:
Determining interface limits;
Performing PV-curve analysis;
Performing VQ-curve analysis.
Automatic AC contingency analysis;
Reading of existing RAS;
Automatically determining optimal remedial actions as an advisory function for operators
Never collapses buses during its analysis
Always uses FULL NON-CONSOLIDATED MODEL
Very strong solution engine
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

21. Steady-State Voltage Stability Analysis Using Node-Breaker Model
PV-Curve and VQ-Curve are most frequently used steady-state techniques for voltage stability assessment
At selected buses
PV-curve analysis
Stresses the system in terms of load increase, power transfer and computes post- contingency voltages
Multiple power flow computations to determine the stability margin
VQ-curve analysis:
Adding a fictitious condenser bus
V is independent variable, Q injection is dependent
Provides a set of scheduled voltages at a bus
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

22. Reading Node-Breaker Model in POM Suite/ROSE
As export “flat” file is being loaded, its summary is displayed on the interface
As POM reads the export file and contingency lists, it performs topology processing
Generates a file that lists buses that were split and how they were split as a result of contingencies
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

23. Displaying Node-Breaker Model in POM Suite/ROSE
After export “flat” file is being loaded, it is displayed in the form of:
POM Data Tables
One-lines that are automatically built
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

24. Use of Node-Breaker Model for Voltage Stability Analysis
Node-breaker representation is used to:
Determine import limits on the interfaces
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

25. Use of Node-Breaker Model for Voltage Stability Analysis
Node-breaker representation is used to:
Compute and plot PV-Curves
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

26. Use of Node-Breaker Model for Voltage Stability Analysis
Node-breaker representation is used to:
Compute and plot VQ-Curves
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

27. Use of Node-Breaker Model for Analysis of a Particular Contingency
A particular contingency may be further analyzed:
On the base case
While stressing the system in terms of a power transfer, load scaling, etc.
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

28. Use of Node-Breaker Model for Determining Remedial Actions
Remedial actions may be further developed to:
Alleviate post-contingency violations
Voltage stability, voltage, thermal
Increase operating margins
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

29. Use of Node-Breaker Model for Automatic Contingency Analysis
Automatic massive AC contingency analysis may be performed
N-1, N-2 contingency analysis
RAS enabled/disabled
Post-contingency remedial actions may be automatically determined during massive computations
Critical contingencies, post-contingency violations and remedial actions reported
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

30. Challenges of Using Node-Breaker Model
Not a formal database:
Complex procedures for reading/processing of export “flat” file
Utilities/ISOs do not usually use this format internally
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

31. Advantages of Using Node-Breaker Model in POM Suite
Accurate representation of the real-time system:
An actual State Estimator snapshot
Accurate real-time contingency analysis:
Buses may be split, if necessary
Breakers are not being collapsed during power flow solution
Export file from EMS may be saved as a bus-branch model (in PSS/E .raw format):
All breakers are kept in the model as zero-impedance lines
Node-breaker model is used in POM Suite for:
Voltage stability, contingency analysis, system stressing (power transfer simulation, load scaling), RAS actions, any power flow computation
Copyright © V&R Energy Systems Research, Inc. All rights reserved.

32. Thank you!
Copyright © V&R Energy Systems Research, Inc. All rights reserved.