Demonstration of a simple power-flow analysis of a PV-Plant using OpenDSS.
Introduction
Power flow studies plays an important role in supporting decision making in the power systems
field. Since modeling power flow with multiple load sources can be quite complex, several
tools have been developed to facilitate power flow studies at the grid level. OpenDSS is a
power distribution system simulator (DSS) from EPRI. In a nutshell, it allows you to solve the power flow for the fundamental
grid frequency.
This example illustrates the application of the Typhoon HIL software in the field of Power
Systems by co-simulation with the OpenDSS software. Typhoon HIL and OpenDSS can be
interfaced together by means of a voltage-power exchange over the power system bus. That
interface happens at the HIL SCADA level through Python APIs. It works by providing the
OpenDSS simulation with information about power injections on a specific bus, solving a
snapshot of the power flow, and then providing a new voltage setpoint at that same bus to
the emulation running on the HIL device. On the OpenDSS side, the interfaced bus is any
regular bus (P, Q node); on the Typhoon HIL side, the interfaced bus is a three-phase
voltage source with a three-phase power measurement connected at its terminals.
Model description
The model of the PV plant consists of a photovoltaic panel, an average model of a
PV inverter, and a three-phase voltage source. The PV inverter (average) component is used
directly from the Microgrid Library.Figure 1. Grid-connected average PV inverter modelFigure 2. PV inverter subsystem
The OpenDSS model consists of an equivalent grid source, a transformer, and a constant power
load connected to the same bus.Figure 3. OpenDSS model
Bus voltages from OpenDSS control, the grid component in Typhoon HIL, and the PV
inverter P and Q powers are fed back into the bus. OpenDSS then makes a power flow snapshot
and updates the bus voltages. Figure 4. Voltage-power exchange between two models
Simulation
This application comes with a pre-built SCADA panel shown in Figure 5. It offers the most essential user interface
elements (widgets) to monitor and interact with the simulation at runtime, allowing you to
further customize it according to your needs.
An OpenDSS installation is not required for Typhoon HIL Control Center to access the
load flow solver on the same PC. Since the Typhoon HIL is Python-based, all you need in
order to use the OpenDSS simulation is to import OpenDSSDirect.py in the Typhoon HIL SCADA
initialization file. This is accessesed via the Open panel intialization
dialog button in the HIL SCADA menu bar. This file is a cross-platform Python
package that implements a direct library interface to the OpenDSS engine. Finally, it is
necessary to save all the files (.tse, SCADA etc.) in the same folder. Figure 5. SCADA panel
The functionality of this inverter is very straightforward. When the inverter is enabled, it
will reach the maximum power point. There is also a possibility to set the reactive power in
the Inverter Control options. For voltage-power exchange between the two models it is
necessary to first enable communication and then turn the inverter on. There is also a
contactor in OpenDSS controlled through HIL SCADA which should be closed. For the power flow
report, it is necessary to click the Generate power flow report
button. Figure 6. SCADA panel
Figure 7 shows the power flow report in
the case when the switch is closed. As the figure shows, the active and
reactive power are almost equal with only small variations in values. This is due to the
transformer, which has a series of inductances, as well as a magnetizing inductance.
Figure 7. Power flow report obtained when the switch is closed
Figure 8 and Figure 9 demonstrate the case when the switch is open.
In this case, the voltage on the common bus is 0, as are the powers that the inverter sends
to OpenDSS. Figure 8. SCADA_panel when the switch is open
Figure 9. Power flow report obtained when the switch is open
Table 1. Minimum requirements
Files
Typhoon HIL files
examples\models\power systems\opendss power flow co-simulation
opendss power flow co-simulation.tse,
opendss power flow co-simulation.cus,
opendss_model.dss,
PV_250KW.ipvx
Minimum hardware requirements
No. of HIL devices
1
HIL device model
HIL402
Device configuration
1
Test automation
We don’t have a test automation for this example yet. Let us know if you wish to contribute and we will gladly have you signed on the application note!
