Running Multiple PSS/E Simulations

Summary
This application note describes how to use EnFuzion with PSS/E. EnFuzion speeds up PSS/E simulation runs by using multiple computers.

What is Power System Simulator for Engineering (PSS/E)?
Power System Simulator for Engineering is an integrated, interactive program from Siemens Power Transmission & Distribution, Inc., Power Technologies International (Siemens PTI) for simulating, analyzing and optimizing power system performance. It makes available to the user methods in many technical areas, including: power flow, fault analysis, dynamic simulation, open access and pricing, transfer limit analysis and network reduction.

How Does EnFuzion Speed Up PSS/E Simulations?
EnFuzion helps with PSS/E simulations in many ways. It schedules execution of multiple PSS/E simulations on all available computers. By distributing execution over multiple computers, the results are obtained faster or more simulations can be performed in the same time period. Additional EnFuzion benefits include optimum resource utilization and reliable execution by working around computer failures. This maximizes engineer's productivity by handling all aspects of job scheduling.

How Is EnFuzion Used With PSS/E?
This note shows in detail how PSS/E simulation runs are executed faster using multiple computers.

EnFuzion is optimized for parametric simulations, where the same basic simulation is executed many times with different input parameters. Parametric simulations are commonly used in analysis of power systems for tasks, such as dynamic stability studies, power flow (N-1/N-2), short circuit analysis, VQ curve analysis and available transfer capability (ATC) and operational transfer capability (OTC) studies. Such simulations produce a large number of jobs, sometimes numbered in thousands. Since the jobs are independent, they can be executed concurrently on multiple computers, which results in significantly shorter simulation time. The following is an overview of steps that are required to speed up PSS/E based parametric simulations by using multiple computers with EnFuzion:

1. install EnFuzion and PSS/E on the local computer and on all remote computers that will be used to execute PSS/E simulations,
2. configure EnFuzion by determining an EnFuzion user account on all remote computers and specifying remote computers in the enfuzion.nodes file on the local computer,
3. prepare a PSS/E based parametric simulation,
4. prepare an EnFuzion script, called simulation.pln, that describes the simulation,
5. specify the number of simulations by clicking on simulation.pln. This step produces simulation.run.
6. start execution on remote computers by clicking on simulation.run. A text window shows an execution log and progress.

Steps 1. to 4. are required only once and can be done as part of EnFuzion installation. Steps 5. and 6. are performed once for each simulation execution. Each step is described in detail below.

Installation of PSS/E and EnFuzion
The installation requires the following steps:

• Install the PSS/E software on all computers that will execute the simulations.
• Install the EnFuzion software on the computer that will control the simulations and on all computers that will execute the simulations. The controlling computer is called EnFuzion Root. The executing computers are called EnFuzion Nodes.

Details on PSS/E and EnFuzion installation are described in their respective user manuals.

EnFuzion Configuration
The EnFuzion Root and Nodes must be configured, so that the Root is able to utilize the Nodes.

The following steps configure EnFuzion:

• For each EnFuzion Node computer, determine account that will be used to execute jobs on that computer. This can be an existing account. Otherwise, create a new account.
• Describe EnFuzion Nodes in the enfuzion.nodes file on the EnFuzion Root computer. Default location for the file is C:\EnFuzion\config. Each line in the file contains computer name, user name on that computer and user's password.

Further details on EnFuzion configuration are described in the EnFuzion user manual.

Preparation of PSS/E Parametric Simulation
A parametric simulation executes the same model many times with different input parameters. On the EnFuzion Root computer, organize your parametric simulation as follows:

• place input files that are common to all simulations in directory called data-common. These are basic input data files, describing power system characteristics, basic parameters and similar. If any user dynamic libraries, such as DSUSR.DLL and IPLUSR.DLL, are required, place them in this directory as well.
• place each set of input files, specific to only one simulation, in a directory, called data-. Replace with the simulation number, starting with 1. The files for the first simulation are placed in directory data-1, for the second simulation in data-2 and so on.
• in the data-common directory, prepare a control IDV file for PSS/E, called control.idv, that controls a single simulation in a batch mode. The control file assumes that all input files are taken from the current working directory and that all results are stored to the results directory.

PSS/E parametric simulations and their associated directories can be organized in many different ways. The organization above is just one example used for this application note. EnFuzion is very flexible and can be easily adapted to suit specific requirements.

Preparation of EnFuzion Script - simulation.pln
EnFuzion script in simulation.pln is a simple list of commands that describe how to execute a parametric simulation. These commands control the copying of files between the EnFuzion Root computer and Nodes and execution of the PSS/E application.

The following is simulation.pln EnFuzion script, which is used for the PSS/E parametric simulation described above:

    # node initialization, copy common files to a remote computer

    task nodestart

	node:mkdir data

        copy data-common/* node:data

    endtask

    # job execution:

    #     copy job specific files, execute PSS/E, copy back the result

    task main

        # copy job specific files

        copy data-$count/* node:data

        # execute the PSS/E simulation with batch options

	node:cd data

        node:execute pssds4 -gnikool off -inpdev control.idv

        # copy directory with results back to the local computer

        copy node:result/* result-$count

    endtask

    # parameter to specify the number of jobs

    parameter count integer range from 1 to 1 step 1;

task nodestart initializes each node computer that will execute simulations. It creates a directory data and copies common input files to that directory. Since the files are copied only once, this initialization step saves significant network traffic. It avoids the need to copy the files separately for each simulation. This task is executed once for each computer that will execute individual simulations. task main copies simulation specific files to the remote computer, executes the simulation and copies results back to the EnFuzion Root computer. $count is replaced with a job number, which is different for each job. This task is performed once for each simulation on the computer that is scheduled to execute the simulation. A separate directory containing simulation specific files is created for each simulation. Since each simulation executes in its own directory, this ensures that simulations do not interfere with each other, when multiple simulations are executed on the same computer. The common input files, which were transferred to the computer during the nodestart task, are automatically copied to this directory before the simulation starts executing, so there is no need to make any special provisions for the common files. The directory is deleted after the simulation completes, which prevents accumulation of files on remote computers. parameter specifies the total number of simulations. Variable count is a job number, initialized to one simulation.

Specifying Number of Simulations
To specify the number of simulations:

• click on simulation.pln, which brings up a window,
• type the number of simulations in the To field,
• select File and Save Run to save the number of simulations.
• select File and Exit to exit the program.

This step produces simulation.run file, which contains description of all the simulations.

Executing the Simulation
To execute all the simulations on remote computers:

• click on the simulation.run, which starts the execution.

A text window shows an execution log and progress. While the program is running, a Web based interface is available at http://:10101. Replace Further information
This application note describes how EnFuzion is being used with PSS/E from Shaw Power Technologies Inc.. It uses EnFuzion 7 release. You can find out more about the use of EnFuzion for power utilities on the Axceleon Web site at www.axceleon.com.

Axceleon thanks Siemens PTI for feedback and assistance with the note. You can find out more about PSS/E at http://www.pti-us.com/pti/software/psse/index.cfm.