Simulation is a major key to enhancing power system
diagnosis, design and operation. InterPSS -Internet technology based Power
System Simulation- is an open-source software system which simulates power
system, diagnosis design and operation. InterPSS is a cloud based software,
written in Java programming language, that’s easily accessible and it easily
simulates power system.
As the figure shows the different levels of architecture.
InterPSS simulation engine provides a detailed analysis for systems’
functionalities and architecture. The software provides a real-time simulation which
serves several frameworks. For instance, InterPSS is distinguished by its loosely
and flexible coupling system architecture. It allows power system solution
providers or third parties to plug in their own simulation modules. In addition,
it serves the system integrators to plug in their standard-based software
infrastructure and integrate it easily with InterPSS. (InterPSS,
InterPSS 2.0, n.d.)
InterPSS contains multiple functions analysis that are
available and other functions that are still under development. It contains,
for instance, AC and DC load flow simulation analysis. It sends simulation
requests with simulation input data which simulates the engine. The later
replies with a response after completing a certain calculation. It also includes function analysis for short
circuit, transient stability and distribution system analysis. Further
development for the software which includes harmonics analysis and protective
relay coordination. Moreover, it will include the dynamic stability and reliability
for small signals.
As it can be shown in the figure above, InterPSS 2.0
interface is also based on Google Spreadsheet. The User power system simulation
input data and simulation results and reports are all saved in Google’s drive.
The data is protected under Google’s Information Security and Privacy
properties. (InterPSS, InterPSS 2.0, n.d.)
Applications and implementations:
The software services currently provides three available
Recent technological advances allowed
network and software developments to possibly perform cloud grid computing for power
grids that are locally or remotely located. With traditional network and
computing technologies, it was impossible to meet the requirement of power
system real-time simulation due to the huge amount of contingency analysis
cases that should be evaluated in a short periodic time. Furthermore,
traditional computers used to have only a single CPU which hardly provides, for
instance, an accurate AC loadflow power network model. Thus, further manual
approximation and regularization needed to be done to reach that.
Modern network and cloud based computing have
successfully facilitated the traditional challenges. Grid computing solved power system real-time
simulation problems using multiple CPUs which provide an accurate AC loadflow
model. A Chinese university conducted an experiment using InterPSS Grid
computing. The research group simulated the loadflow based on 1245 buses and
1994 power branches.
Their contingency analysis was performed on
2500 N-1 by running 2500 full AC parallel AC loadflow. They installed InterPSS
on one computer as a master grid node and remote grid nodes agents in other
computers. The 2500 contingencies were created and simulated while running the
2500 AC loadflow. The results shows the 10 CPU and compared to the traditional
CPU-time in minutes
CPU-time in minutes
As the results demonstrated the linear
scalability that InterPSS grid computing provides. The 10 CPU allows real-time
The group also computed the transient
stability based on a thousand-transient stability parallel simulations. The results, according to the graph above,
show that InterPSS grid computing reached again a linear scalability.
There are two different ways to create
InterPSS simulation job as shown in the diagram.
On one hand, the Master
Node Job Creation is the default simulation behavior. From an abstract
overview, simulation jobs are created within the master node. The master node
then distributes the simulation to the remote nodes. Several simulation jobs can
be sent in a real-time. There is a certain threshold that these jobs can be
handled. If it exceeds thousands of simulation jobs, for example, the computer
network can get congested and the simulation may take longer.
On the other hand, the Remote
Node Job Creation is the manual simulation behavior. It is considered to be
more efficient in the case of N-1 contingency analysis. The list of contingencies
are sent simultaneously to each remote node. As a result, the simulation job
for the N-1 contingency, opening line Bus1 to Bus2, can be created at certain
Open Data Model (ODM):
ODM is an open-source model which initially
exchanges power system simulation data. Open Data Model doesn’t follow the IEEE
standard for exchanging loadflow data. It is observed that these formats are not
fully documented. Therefore, power engineering community shall utilize an open,
flexible and well-documented format for power system analysis for information
exchange. ODM, for instance, is based on XML schema which became a de facto
standard. According to InterPSS, there are several advantages representing the
loadflow data in XML format. XML format, for instance, is readable and easy to understand.
XML provides with a coherent script in which any power engineer can precisely
interpret. A common IEEE confusion, for
instance, whether the number 40.0 means load P or generation P in PU or Mw.
ODM model also provides a flexible
import/export utilities among different data formats.
The figure shows the multiple data formats
that ODM model can flexibly filter or convert. If ODM model becomes widely accepted
as a global standard, third party tools can be adapted to the model. For
example, Graphic one-line diagram editors or different simulation models, as
shown in the figure below, can be based on ODM model and become an open-source software
Unlike IEC CIM model which simulates the power
system operation state on both the physical and the logical view, the ODM model
implementation simulates only the logical view of the power system. However,
the nodal bus and branch are represented which are the most fundamental concepts
in power system. For instance, IEEE CDF consists if bus and branch records;
while, InterPSS raw data consists of bus and branch records; in addition to
other records which reference the bus and branch records.
A conducted study showed that ODM model is capable
of solving real world power system simulation problems. For instance, ODM XMl
document can be 4 times larger than IEEE CDF file, and it can be converted in
1.6 seconds per 2 Megabytes file (InterPSS, UCTE 2002 Sample
Loadflow Case, n.d.).