How to initialize dynamic studies from static study results

Background

This example explains how and why you could use a static study result to initialize a dynamic study using the gridmo platform. Below you can also find a step-by-step tutorial and a downloadable example you can run on your Engine.

Why initialize from static study results?

Generator interconnection studies are increasingly being completed using multiple power systems software packages, where the results from each package must be benchmarked. It can be difficult to ensure accurate benchmarking across different software packages. One approach to improve the alignment of the dynamic results between packages is to initialize the dynamic studies using the results from a common static study.

For example, you may have a complex generating system with multiple tap changers, switched reactive plant (harmonic filters, SVCs etc) and want to use the result of a static study completed in PSS®E or PowerFactory to initialize a dynamic study in a different software package, such as PSCAD™.

Common values exported from static static study results

The following values are commonly exported from static study results and used to initialize dynamic studies:

• Plant statuses:
  • Tap positions of any on-load tap changers (see OUTPUT, VAL=TAPRATIO).
  • Step positions or status of any switched reactive plant (e.g. SVCs, switched caps, harmonic filters).
• static study results:
  • Voltage magnitude at a bus, typically the infinite or reference bus for the generating system (see OUTPUT, VAL=V).
  • Voltage angle at a bus, typically the infinite or reference bus for the generating system (see OUTPUT, VAL=ANGLE).
• Generating system target values:
  • Power factor target on a line, typically the line connecting the generating system to the grid (see OUTPUT, VAL=PF).
  • Voltage droop target on a line/bus, typically the line connecting the generating system to the grid (see OUTPUT, VAL=VDROOPTARGET).

tip

You can download the complete example project file used in this tutorial from the below link. This downloadable example uses a PSS®E Static Node (or optionally a PowerFactory Static Node) to calculate a static study and export the voltage magnitude at the infinite bus. This result is then imported into PSCAD™ as the initial conditions for a dynamic study of a solar farm. The result is benchmarked with a PSS®E Dynamic result (and/or optionally a PowerFactory Dynamic) result. The models required to run this simulation are packaged with the gridmo Engine - no further configuration is required.

tip

Simple generating systems (those with simple tap changer controls and no dynamic/switched reactive plant) may not require initialisation from a static simulation at all.

Specifically, if you only require infinite bus voltage to be calculated to achieve a desired point of connection (POC) voltage, you can use the following Commands to turn on smiby's automatic infinite bus voltage calculation function in the PSCAD™ Node's Commands field - removing the need for a static simulation to calculate the infinite bus voltage altogether.

Add the following to a PSCAD™ Node's Actions field to turn on auto infinite bus voltage calculation mode

SET, CNAME=smiby, PARAM=auto_vinf_enabled, VAL=1 //1 to enable, 0 to switch to manual vinf mode
SET, CNAME=smiby, PARAM=auto_vinf_poc_v, VAL=PUT_POC_V_DESIRED_IN_PU
SET, CNAME=smiby, PARAM=auto_vinf_poc_p, VAL=PUT_POC_V_DESIRED_IN_MW
SET, CNAME=smiby, PARAM=auto_vinf_poc_q, VAL=PUT_POC_V_DESIRED_IN_MVAR

Example

In the following worked example, we are going to configure a PSS®E static simulation to export the voltage magnitude at the infinite bus. We will then use this value to initialize a PSCAD™ simulation of a solar farm.

note

The following example assumes you have a basic understanding of the gridmo platform. If you are new to gridmo, please see the Getting started guide.

1) Start a new gridmo Project and add the following Nodes

• Start Node
• PSS®E Static Node (or PowerFactory Static Node)
• PSCAD™ Node
• Plot Node
• End Node

2) Connect the Nodes as per below

3) Configure the PSS®E Static Node

• Double click on the PSS®E Static Node to open the configuration window.
• Set the Model to gridmo\wecc-solar\psse\solar.sav to use an example 175 MW solar farm's PSS®E case file.
• Select the Define simulation & Define outputs tab.
• Under the Commands field, add the following Commands:

PSS®E Node's Commands field

SET, LINE=1000->999#1, STATUS=IN, SCR=7.5, XR=4
CONTROL, GEN=999#1, Q=VDIRECT, ATBUS=1000, VTARGET=1.00, QMIN=-9999, QMAX=9999
CONTROL, GEN=91003#S1, ATLINE=1001->1000#1, P=175
CONTROL, GEN=91003#S1, ATLINE=1001->1000#1, Q=FIXED, QTARGET=0
SOLVE
OUTPUT, BUS=999, VAL=V, NAME=i_v_at_inf

• The above Commands:
  • Set the SCR and X/R ratio for this example SMIB model to 7.5 and 4 respectively.
  • It then controls the example solar farm to achieve P=175 MW, Q=0 MVAr at the solar farm's connection point.
  • It also uses the infinite bus generator to achieve 1.00 pu voltage at the connection point.
  • Finally, it outputs the voltage magnitude at the infinite bus and assigns the name i_v_at_inf inside the gridmo simulation. This is creating an Internode Variable.

4) Configure the PSCAD™ Node

• Double click on the PSCAD™ Node to open the configuration window.
• Set the Workspace to gridmo\wecc-solar\pscad\wecc_solar_wspace.pswx to use the same solar farm's PSCAD™ workspace file.
• Select the Define simulation tab.
• Set the Simulation time [seconds] to 10 seconds.
• Under the Actions field add the following actions

PSCAD™ Node's Actions field

CONTROL, CH=SCR, AT=0, VAL=7.5
CONTROL, CH=XR, AT=0, VAL=4
SET, CNAME=smiby, PARAM=vinf, VAL={{i_v_at_inf}}
CONTROL, AT=0, CH=1, VAL=1
CONTROL, AT=0, CH=2, VAL=0
CONTROL, AT=5, CH=2, VAL=0.1

The above Commands:

• Set the SCR and X/R ratio for this example SMIB model to 7.5 and 4 respectively.
• Set the parameter called vinf (which is the initial voltage magnitude at the infinite bus) to the value of i_v_at_inf which comes from the PSS®E Static Node (an Internode Variable).
• Sets channel 1 (which is connected to the solar farm's active power control) to 1 per unit (meaning maximum power e.g. 175 MW) and channel 2 (which is connected to the solar farm's reactive power control) to 0 per unit (meaning 0 MVAr). Note these values could also be exported from the static simulation using an OUTPUT, LINE=..., VAL=..., NAME=... Command.
• Finally, we make a change in the reactive power control channel 2 at 5 seconds to 0.1 per unit (e.g. 17.5 MVAr).

5) Configure the PSCAD™ output channels

• Add the following output channels to the PSCAD™ Node

PSCAD™ Node's Output field

OUTPUT, TITLE=smiby_POC_VOLT, VAL=V, NAME=i_ch_poc_v
OUTPUT, TITLE=smiby_POC_P, VAL=PQS, NAME=i_ch_poc_p
OUTPUT, TITLE=smiby_POC_Q, VAL=PQS, NAME=i_ch_poc_q

The above Commands:

• Output the voltage magnitude at the point of connection (POC) to the grid and assign the name i_ch_poc_v
• Output the active power at the POC and assign the name i_ch_poc_p
• Output the reactive power at the POC and assign the name i_ch_poc_q

6) Configure the Plot Node

• Double click on the Plot Node to open the configuration window.
• Set the Plot type to PDF to output a PDF file.
• Enter an output file name, such as PSSE to PSCAD initialisation
• Enter a plot title, such as Example SMIB initialisation from PSSE
• In the Define Subplots tab:
  • Set the x-axis minimum 3 and maximum to 10
  • Under Subplots select 1 page, 2 rows and 3 columns.
  • Click on the + to add a new subplot. For each subplot:
    • Enter a title in Subplot title, such as Vpoc
    • Under y-axis Channels enter each of the Internode Variables with the double curly brackets, such as {{i_ch_poc_v}}

7) Launch the Simulation

• Launch the simulation
• The output plot should show a PSCAD™ simulation initialized from the static simulation results, specifically:
  • It should reach a steady state voltage magnitude of 1.00 pu at the connection point.
  • It should reach a steady state active power of 175 MW at the connection point.
  • It should reach a steady state reactive power of 0 MVAr at the connection point.

8) Review the results

An example of the PSSE to PSCAD initialisation.pdf example plot is shown below.

We can see that the PSCAD™ simulation has been initialized to the desired values (1.00 pu, 175 MW and 0 MVAr) from the static simulation.