PV Analysis Tool
EETC-NSS
PV Applications in PSS®E
Why?
• Determine real power transfer or load level limit
How?
• Manually solve multiple power flow cases, record results, prepare tables or
plots ⇓ time consuming, prone to human errors
• Use automation tools such as Python or IPLAN to initiate calculations and
display graphical results ⇓ consistent calculation procedure, but require
programming knowledge
• Use new PV & QV Analysis features ⇓ fast and simple
PV Analysis Basics
• Investigate relationship between power transfer and voltages.
• As transfer (or load) increases, system reactive consumption increases and
voltages fall.
• Want to find maximum power transfer (or load supply) level before voltage
collapse – knee of the curve.
• Perform many power flow solutions and plot results.
V
Knee of the
Curve
Transfer
Limit
P
PV Analysis Procedures in PSS®E
• Prepare power flow base case
• Run DFAX to input subsystem, monitored element and contingency description
files
• Select PV analysis options
• Initiate calculations
• View graphical results
Prepare Base Case
Must Have:
• Valid reactive limits of generators and other reactive support devices
• Generator MW limits for redispatch, if applicable
• Branch ratings, if needed
DFAX
• Read contingency analysis raw data files:
• Subsystem description file (.SUB)
• Monitored element file (.MON)
• Contingency description file (.CON)
• Output binary file (.DFX)
• Input to contingency
analyses
• Input to PV &
QV calculations
How to Accessing PV Analysis Module?
What is PV Analysis Run Options?
Transfer
Increment
Power
Flow
Solution
Stopping
Criteria
Transfer
Dispatch
Method
Subsystem
Selection
Input & Output Files
Analysis Options (cont,)
select contingency
solution options
select basecase
solution options
leave disabled… not adjusting
other generation to resolve
loading issues
this is handled
automatically…
PV_ENGINE_6
for this example…
total transfer is 180 MW
in 10 steps of 18 MW each
select
solution method
no effect if not checking limits
normally set to Rate B
for this example:
both source and
sink generation will
change proportional
to up or down
reserve margin
choose No Limits…
just incase your
transfer exceeds
your generator limits
choose No Limits…
unless doing a
load-load transfer
(which makes
no sense)
0.00 means use existing
load power factor.
no effect if not a load
transfer
leave disabled… not wanting to
stop transfers for
low voltage or overloads
verify subsystem names
should be populated
from DFAX file
type in a name for the .pv file
click Go to run the PV Analysis
Parts of PV Analysis
Power Flow Solution Options
• Solution engine – Fixed slope decoupled or full Newton-Raphson.
• Automatic adjustments options for base case & contingency case – taps,
area interchange, switched shunts, treatment of induction machines, etc.
• Generator var limit.
• Dispatch mode.
• Mismatch tolerance.
Subsystems - source & sink (from DFXfile)
Transfer Dispatch Methods
Dispatch methods:
• DFAX generation and/or load
• Scale by machines MW, MBASE,
reserve (PMAX-PGEN)
Observe MW Limits
Economic dispatch (ECDI) file (with
option to include unit commitment
Loads Power factor can
scaled to new powerfactor
be
PV Analysis:
Transfer Increments
• Initial transfer increment - Adjust “dispatch” in source & sink by normal step
size.
• Tolerance - If solution at normal step fails to converge, retry from last
converged point using binary search technique.
• Negative minimum incremental transfer - Extend PV curve below zero transfer
level.
PV Analysis
Stopping Criteria
1-“Transfer increment tolerance” reached
2-“Maximum incremental transfer” reached
3-“Branch loading threshold” reached (optional).
for List of branches defined in MON file
4-“Minimum monitored bus voltage” reached (optional).
List of buses defined inMON file.
Use voltage limits from:
a-One global minimum limit
b-Set of normal and/or
Emergency voltage limits
from bus data Record
"for
this
option
Voltage
limits in MON file are not
used"
Other PV Analysis Options
• Choice to terminate using bus voltage limit set, instead of one global minimum
voltage.
• Provide message in progress window when terminating due to loading or
voltage limit violations.
• Scale New load by increasing/decreasing with specified power factor.
•Allow overlapping definition of source and sink buses.
•Redispatch for load/generation
imbalance during contingency.
Different P-V Analysis
Solution Engines
• Original PV_ENGINE (V30): Each contingency is applied at base transfer, then
transfer level is increased.
• PV_ENGINE_2 (V31): Transfer level is increased, then the entire set of
contingencies is applied to pre-contingency case at each transfer increment.
Allows different sets of automatic adjustments for pre-contingency and postcontingency solutions.
• PV_ENGINE_3 (V32): Similar to PV_ENGINE_2, but also allows specification
of negative minimum incremental transfer.
PV Analysis
Graphical Output
Select
Graph
Type
Select
Base &
Cont
Cases
Select Bus
or
Generator
Y-axis
elements
Selected
PV Analysis
Plot Options
Double click on
numbers for
axis options
More Graphics for PV (or QV) Analysis
Curves can be displayed
singularly or together
For multi-graph
PV Analysis
Multi-Graph Printing
•
•
•
•
Right-click in graph area
Choose option to copy in Bitmap or Metafile format to clipboard
Paste to other document
Can also copy legends
PV Analysis
Save Case Options
User may save solved power flow cases in ZIP file:
• At only the maximum transfer reached for each contingency
• At all transfer increments, for every contingency
Open individual cases by:
File > Import > Restore Incremental Save Case
Exporting PV/QV Results to Excel
• Select data/results to export:
• PV or QV Solution Results
• Define data/results file
• Define Excel workbook file
• Select quantities to export
• Select Contingencies
Getting Raw Data Results
select PV Solution
specify your .pv file
auto populated
select what tabs you want
if this dialog does not pop-up
_WXPATH = r'C:\Python27\lib\site-packages'
os.environ['PATH'] = _WXPATH + ';' + os.environ['PATH']
try this code in the Python command line, then run again
select what contingencies you want
click the Export button
Retrieving PV Analysis Results from a File
All run options
retrieved from
.PV file.
Model a Given Transfer Level (VIP)
• Use transfer adjustments similar to those in PV analysis.
• Choose a desired incremental transfer level.
• Changes will be applied to base case to create a new power flow at desired
transfer level.
• Suitable for detailed investigations after PV analysis