1. Resource Data Needed For Dynamic Simulations
And the problems created by incorrect or incomplete data

2. Importance of Accurate Modeling
Source: BPA Presentation to NERC Planning Committee, Dec. 7, 2010

3. Importance of Accurate Modeling
Source: Transmission Research Colloquium Sacramento, CA September 11, 2008

4. Importance of Acc Modeling
Source: Transmission Research Colloquium Sacramento, CA September 11, 2008

5. Generator Modeling in Dynamics
Stability Studies are interested in calculating the response of machines connected to the system in three time frames following an event:
Sub-transient – a few cycles
Transient – a few cycles to several seconds
Steady State
The dynamic response of the system is studied during a stability study. Three time frames are important.
Stability studies analyze the state and response of the system as it changes through time. Each increment in time is typically 0.1 cycle. The solution to each increment is saved for the areas and parameters of interest and then reviewed to understand the performance of the system.
Subtransient is 1 time step to a few cycles.
Transient is a few cycles to several seconds.
Steady State occurs when the system remains unperturbed for a significant amount of time.
A common practice is to begin stability studies with a “Flat Start” case. The “Flat Start” case is intended to provide engineers with a base case that represents the steady state of the system.

6. Generator Modeling in Dynamics
Pmax, Pmin, Qmax, Qmin
MVA BASE and Zsource
Unsaturated Sub-transient Reactance
Dynamic Models and Parameters
Transformer (GSU) Data
Collection System Data
Under/Over Voltage set points
Under/Over Frequency set points
All of these parameters are necessary to model the system in Dynamics.

7. Resource Asset Registration Form1
Generator Details
Labels
What is the MVA base that the following data is based on?
MVA
What is the kV base that the following data is based on? kV
Direct Axis Subtransient reactance, X"di (Unsaturated) pu
Direct Axis Transient reactance, X'di (Unsaturated)
Positive Sequence Z (Unsaturated)
R in p.u.
X in p.u.
Negative Sequence Z (Unsaturated)
Zero Sequence Z (Unsaturated)
Direct Axis Subtransient reactance, X"dv(Saturated)
p.u.
Direct Axis Transient reactance, X'dv (Saturated)
Positive Sequence Z (saturated)
Negative Sequence Z (saturated)
Zero Sequence Z (saturated)
This presentation will focus on the items highlighted in red.

8. Generator Data In PSSE
Pmax, Pmin, Qmax, Qmin, Mbase, Rsource and Xsource values in PSSE

9. MVA Base Transmission line parameters MVABASE = 100 MVA
Transformers and Machines may use
MVA Rating
Arbitrary
Per Unit Values need to be Accompanied by their MVABASE and kVBASE Base values
The value for MVAbase can be confusiing.
Transmission line parameters must all be calculated on a 100 MVAbase.
However, transformer and machine impedances most often do not use 100 MVAbase.
The values are typically found in a datasheet or on a nameplate that specifies the MVAbase and the impedances.
The per unit values for generators and transformers must be accompanied by the value for MVAbase and Kvbase used to calculate the per unit values.
It is preferred that the values reported in RARF match the values reported on supporting manufacturers data sheets for machines.

10. Generator Model in PSSE
This drawing is simple representation of the generator model used in dynamic simulations. The generator is represented as an ideal current source that passes through impedances that represent the machine, a step up transformer, and a collection system equivalent.
The representation of the collection system is important for proper modeling in plants that are connected to the system via a long transmission line or have multiple units that feed a single point of interconnections through an expansive collection system.

11. Generator Model in PSSE
The magnitude and phase of the source current are determined
at any instant as a function of the instantaneous values of generator state variables (i.e., rotor circuit flux linkages, shaft speed, and rotor angle).
The magnitude of the source current is inversely proportional to the Zsource.
As Zsource increases, source current decreases.

12. Dynamic Impact of increased QMAX and MBASE values
Larger QMAX and MBASE values suggest more dynamic reactive compensation from a generator is available for system voltage recovery contribution.
Study results will be overly optimistic and will mask system dynamic voltage issues.
MBASE values are a source of reference for calculation many generator dynamic model parameters
Unit inertia (H constant) =
Generator impedances
Exciter and Governor limits
MVAbase also affects other generation parameters such as the Unit Intertia and the Exciter and Governor limits.

13. Dynamic Impact of increased QMAX and MBASE values
CenterPoint Energy System dynamic bus voltages after a large disturbance
Actual QMAX and MBASE data
Larger QMAX and MBASE data from current RARF
These charts show the effect of a larger Qmax and MVAbase value. These plots are the result of simulations before and after Qmax and MVAbase values were increased.
The phenomena here is similar to the underlying cause for what happened the WECC in 2004
Results in 3824 MW of Under Voltage Load Shedding
Results in 0 MW of Under Voltage Load Shedding

14. Generator Dynamic VAR output example

15. Resource Asset Registration Form1
Generator Details
Labels
What is the MVA base that the following data is based on?
MVA
What is the kV base that the following data is based on? kV
Direct Axis Subtransient reactance, X"di (Unsaturated) pu
Direct Axis Transient reactance, X'di (Unsaturated)
Positive Sequence Z (Unsaturated)
R in p.u.
X in p.u.
Negative Sequence Z (Unsaturated)
Zero Sequence Z (Unsaturated)
Direct Axis Subtransient reactance, X"dv(Saturated)
p.u.
Direct Axis Transient reactance, X'dv (Saturated)
Positive Sequence Z (saturated)
Negative Sequence Z (saturated)
Zero Sequence Z (saturated)
This presentation will focus on the items highlighted in red.

16. What is Saturation
Saturation is the state reached when an increase in applied external magnetizing field H cannot increase the magnetization of the material further, so the total magnetic field B levels off.
The flux linkages in a synchronous machine are primarily through air and are not significantly affected by saturation.
Generator models recognize that the extent of the saturation effect depends upon both rotor (field) and stator currents.
Accordingly, the models derive the effective saturated parameters of the machine at each instant by internal calculation from the specified (constant) unsaturated values of machine reactances and the instantaneous internal flux level.
The user should enter unsaturated values of all machine reactances in setting up Dynamics data for simulation, and must enter an appropriate set of open-circuit magnetization curve data for each machine.

17. What is Saturation
Straight line is the “air-gap line” used to determine the field voltage/current.
Curved line is an indication of the degree of saturation.
Equations here can be used to provide data
Saturation Factors needed in Model data
The line departing from the straight line is the Open Circuit Saturation characteristic of the machine and indicates the degree of saturation in the rotor and stator iron.

18. Typical Models for a Conventional Generator
Gov.
Exciter
Gen
Gov.

19. Sample Model Data Sheets

20. Sample Model Data Sheets

21. Sample Model Data Sheets

22. Generator Data Additional Data Needed-
User Models need application notes for models;
data sheets
dyr files
ERCOT Confidential
Stability Study Model (if applicable)
Embed a PDF (zip) (
ERCOT Confidential
One Line Diagram
Embed a PDF or CAD One Line Diagram below:

23. Protection Tabs Undervoltage and Overvoltage
Plant Voltage Protection
Label
Instantaneous Undervoltage Trip
p.u.
Undervoltage 1
Time 1
sec
Undervoltage 2
Time 2
Undervoltage 3
Time 3
Undervoltage 4
Time 4
Instantaneous Overvoltage Trip
Overvoltage 1
Overvoltage 2
Overvoltage 3
Overvoltage 4

24. Protection Tabs Under-frequency and Over-frequency
Plant Frequency Protection
Label
Instantaneous Underfrequency Trip Hz
Underfrequency 1
Time 1
sec
Underfrequency 2
Time 2
Underfrequency 3
Time 3
Underfrequency 4
Time 4
Instantaneous Overfrequency Trip
Overfrequency 1
Overfrequency 2
Overfrequency 3
Overfrequency 4

25. Additional Information
Breaker Interruption Time
Label
cycles
Turbine VRT Capability
Provide Manufacturer's technical document / Simulation results / Test Result, etc. Describing the turbine technology & VRT options purchased with turbine, if any
Do Personnel (onsite operator/Engineer etc.) have control to enable/disable or change the settings for voltage ride-through
Y/N
Does the resource use dynamic reactive devices (SVC/STATCOM, etc.) at the wind farm? - (Note: Capacitor Banks used for conventional reactive support cannot be considered as dynamic reactive devices) - If yes, please provide supporting documentation. (Manufacturer's technical document, PSS/E model etc.)
Provide Turbine Voltage & Frequency Protection Settings as per Manufacturer - Technical document and/or spec sheet
Does the resource have Plant Voltage Protection? If yes, please provide supporting documentation.
Does the resource have Feeder Voltage Protection? If yes, please provide supporting documentation.

26. Maintaining Data Critical
Upgrades
Exciters
Turbine
Stabilizer additions
Reactive devices (Caps, Reactors, D-Vars, SVCs)
New
Preliminary to Commissioning
Generator tests should provide the data needed to update the appropriate data sheets.
Some Resource Owners are providing detailed engineering reports containing the model parameters and test data used to establish the parameters.