PSS/E Based Network Frequency
Response Analysis Tool
Yu (Terry) Tian, MSc student, tian7@ualberta.ca
Nov. 06, 2013
Department of Electrical and Computer Engineering, University of Alberta
Motivation
Software Algorithm
Resonance: Because of the existence of both inductive and
Read PSSE Case File
capacitive components in the system, at certain frequencies,
resonance conditions might occur at some buses. If the
resonance occurs at a bus where a harmonic current is injected
into the system, an overvoltage will be observed.
Retrieve steady state bus voltage V(0) from PSS/E
Frequency Scan: A frequency scan is a plot of the driving-point
/ transfer impedance at a system bus versus frequency. The bus
of interest is one where a harmonic source exists. The frequency
scan is a very effective tool to detect resonances which appear as
peaks (parallel resonance) and valleys (series resonance) in the
plot of impedance magnitude vs. frequency.
One of the most common ways to obtain the harmonic impedance
is by using EMTP software. This requires a significant manual
labour to collect a huge amount of information and to model a
usually large interconnected network. Hence it is desirable to
have a software that can run frequency scan directly on a PSSE
case file, which stores all the system information and is well
maintained by utility companies.
Modify PSSE case for each frequency
Passive Load
Generator
𝑍𝐺 ℎ = 𝑅𝐺 + 𝑗ℎ𝑋𝐺
Series Impedance Model
Transformer
𝑍𝑇 ℎ = 𝑅𝑇 + 𝑗ℎ𝑋𝑇
Transformer tap ratio and phase
shift in three sequence are also
included in the model.
𝑉2
𝑅 + 𝑗𝑋 =
𝑃 − 𝑗𝑄
𝑍𝑙𝑜𝑎𝑑ℎ = 𝑅 + 𝑗ℎ𝑋
CIGRE Model
𝑅1 = 𝑉 2 /𝑃
Transmission Line
𝑅𝑙𝑜𝑎𝑑𝑠ℎ = 𝑅1
𝑋𝑙𝑜𝑎𝑑𝑠ℎ = 0.073ℎ𝑅1
PSSE Network Frequency Response Tool
A Python software package developed by PDS-Lab which
analyzes network frequency response on the selected PSS/E
case file. Since the PSS/E itself does not have harmonic analysis
functions, this software can be treated as an 'add-on' of PSS/E.
Typical applications of this software include:




Identify Resonance
 Equipment Sizing
Filter Design
 Equipment Loading Assessment
Verify Standards/Limits Compliance
Harmonic Problem Troubleshooting
𝑋𝑙𝑜𝑎𝑑𝑝ℎ
PI Model
𝑍 ℎ = 𝑅 + 𝑗ℎ𝑋
Shunt Element
𝐵 ℎ =𝐵×ℎ
𝐺 ℎ =𝐺
Distributed Line Model
𝐵 ℎ = 𝐵 × ℎ 𝑐𝑎𝑝𝑎𝑐𝑖𝑡𝑖𝑣𝑒 𝑠ℎ𝑢𝑛𝑡
Long line effect is considered.
𝐵 ℎ =𝐵÷ℎ
 Interact with PSSE directly
 Support up to 50000 buses
 User friendly interface
Frequency
Scan
Harmonic
Calculation
Case File
Positive-Sequence Impedance
Zero-Sequence Impedance
Driving Point Impedance
Transfer Impedance
Spectrum / Waveform Output
Comply IEEE 519 Standard
Capacitor Loading per IEEE 18
𝑉𝑖 − 𝑉𝑖(0)
𝑍𝑖𝑖 =
𝐼𝑖
 Reliable validated result
 Highly customizable
 Easy install/uninstall
ETAP
CYME
Our Tool
ETAP case CYME case PSSE case
√
√
√
×
×
√
√
√
√
×
×
√
√
√
√
×
√
√
×
√
√
Software Graphical User Interface (GUI)
𝑉𝑗 − 𝑉𝑗(0)
𝑍𝑖𝑗 =
𝐼𝑖
Left figure shows IEEE 14 bus
system. A shunt capacitor bank
is to be installed at bus 13 to
support voltage and to improve
power factor. The following two
options are analyzed through a
frequency scan study at bus 13:
IEEE 14 Bus System Diagram
Option 1
Option 2
Add 2 Mvar capacitor
bank at bus 13
Add 1.8 Mvar capacitor
bank at bus 13
Very high impedance at 19th
harmonic, not good
Switching Transient Simulation GUI
Transfer impedance:
Software Demo
Frequency scan result at bus 13
Frequency Scan GUI
𝑖𝑛𝑑𝑢𝑐𝑡𝑖𝑣𝑒 𝑠ℎ𝑢𝑛𝑡
Apply a fault at bus i, Bus voltages after the fault (Vi and Vj), and fault
current at bus i (Ii) are retrieved from PSS/E fault analysis result.
Driving point impedance:
Software Features
ℎ𝑅1
=
𝑄
6.7
− 0.74
𝑃
Frequency scan result at bus 13
Lower impedance at 19th harmonic,
better than option 1