Simulation is a major key to enhancing power systemdiagnosis, design and operation. InterPSS -Internet technology based PowerSystem Simulation- is an open-source software system which simulates powersystem, diagnosis design and operation. InterPSS is a cloud based software,written in Java programming language, that’s easily accessible and it easilysimulates 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 whichserves several frameworks. For instance, InterPSS is distinguished by its looselyand flexible coupling system architecture. It allows power system solutionproviders or third parties to plug in their own simulation modules.
In addition,it serves the system integrators to plug in their standard-based softwareinfrastructure and integrate it easily with InterPSS. (InterPSS, InterPSS 2.0, n.d.)InterPSS contains multiple functions analysis that areavailable and other functions that are still under development. It contains,for instance, AC and DC load flow simulation analysis. It sends simulationrequests with simulation input data which simulates the engine.
The laterreplies with a response after completing a certain calculation. It also includes function analysis for shortcircuit, transient stability and distribution system analysis. Furtherdevelopment for the software which includes harmonics analysis and protectiverelay coordination. Moreover, it will include the dynamic stability and reliabilityfor small signals. As it can be shown in the figure above, InterPSS 2.
0interface is also based on Google Spreadsheet. The User power system simulationinput data and simulation results and reports are all saved in Google’s drive.The data is protected under Google’s Information Security and Privacyproperties. (InterPSS, InterPSS 2.0, n.d.) Applications and implementations:The software services currently provides three availableservices. – Grid Computing:Recent technological advances allowednetwork and software developments to possibly perform cloud grid computing for powergrids that are locally or remotely located.
With traditional network andcomputing technologies, it was impossible to meet the requirement of powersystem real-time simulation due to the huge amount of contingency analysiscases that should be evaluated in a short periodic time. Furthermore,traditional computers used to have only a single CPU which hardly provides, forinstance, an accurate AC loadflow power network model. Thus, further manualapproximation and regularization needed to be done to reach that.
Modern network and cloud based computing havesuccessfully facilitated the traditional challenges. Grid computing solved power system real-timesimulation problems using multiple CPUs which provide an accurate AC loadflowmodel. A Chinese university conducted an experiment using InterPSS Gridcomputing. The research group simulated the loadflow based on 1245 buses and1994 power branches. Their contingency analysis was performed on2500 N-1 by running 2500 full AC parallel AC loadflow. They installed InterPSSon one computer as a master grid node and remote grid nodes agents in othercomputers. The 2500 contingencies were created and simulated while running the2500 AC loadflow.
The results shows the 10 CPU and compared to the traditionalsingle CPU. Single CPU-time in minutes 10 CPU-time in minutes Acceleration ratio 250 26 9.4 As the results demonstrated the linearscalability that InterPSS grid computing provides. The 10 CPU allows real-timecomputational speed.
The group also computed the transientstability 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 createInterPSS simulation job as shown in the diagram. 1- On one hand, the MasterNode Job Creation is the default simulation behavior.
From an abstractoverview, simulation jobs are created within the master node. The master nodethen distributes the simulation to the remote nodes. Several simulation jobs canbe sent in a real-time.
There is a certain threshold that these jobs can behandled. If it exceeds thousands of simulation jobs, for example, the computernetwork can get congested and the simulation may take longer.2- On the other hand, the RemoteNode Job Creation is the manual simulation behavior.
It is considered to bemore efficient in the case of N-1 contingency analysis. The list of contingenciesare sent simultaneously to each remote node. As a result, the simulation jobfor the N-1 contingency, opening line Bus1 to Bus2, can be created at certainremote nodes. – Open Data Model (ODM):ODM is an open-source model which initiallyexchanges power system simulation data. Open Data Model doesn’t follow the IEEEstandard for exchanging loadflow data.
It is observed that these formats are notfully documented. Therefore, power engineering community shall utilize an open,flexible and well-documented format for power system analysis for informationexchange. ODM, for instance, is based on XML schema which became a de factostandard. According to InterPSS, there are several advantages representing theloadflow 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 preciselyinterpret.
A common IEEE confusion, forinstance, whether the number 40.0 means load P or generation P in PU or Mw. ODM model also provides a flexibleimport/export utilities among different data formats.
The figure shows the multiple data formatsthat ODM model can flexibly filter or convert. If ODM model becomes widely acceptedas a global standard, third party tools can be adapted to the model. Forexample, Graphic one-line diagram editors or different simulation models, asshown in the figure below, can be based on ODM model and become an open-source softwaretools. Unlike IEC CIM model which simulates the powersystem operation state on both the physical and the logical view, the ODM modelimplementation simulates only the logical view of the power system. However,the nodal bus and branch are represented which are the most fundamental conceptsin power system.
For instance, IEEE CDF consists if bus and branch records;while, InterPSS raw data consists of bus and branch records; in addition toother records which reference the bus and branch records. A conducted study showed that ODM model is capableof solving real world power system simulation problems. For instance, ODM XMldocument can be 4 times larger than IEEE CDF file, and it can be converted in1.6 seconds per 2 Megabytes file (InterPSS, UCTE 2002 Sample Loadflow Case, n.d.).