Three phase dynamic load fails earlier than expected

Hello,

I have created a Simulink model simulating a three phase dynamic load connected to a controlled three phase (AC) voltage source. The source produces sinoid Voltage signals for a time frame of 0 to 366s when connected to a resistor. However when connecting it to a three phase dynamic load with external control of P,Q (the same behavior however is observed even without connecting it to an external P,Q) for a discrete simulation with 0.02s step and stop time 366 after about 2.7 s the pu voltage returned as an output from the Three-phase-dynamic-load is N/A resulting in a wrong simulation and monitoring the sources output it also stop generating voltage after 2.7 s. The expected behavior would be for both the voltage source and the pu votlage measurements fot the three-phase-dynamic-load to not be N/A after 2.7s.

My circuit is the following:

The scope after the bus B33X-012 and when running the simulation:

On the contrary, the scope after the bus B33X-012 without connecting the three phase dynamic load:

This issue appears every time I run the simulation.

Also, when I run the simulation in diagnostic viewer appears this warning:

Result of power is undefined in 'substation_test/87023072247/Three-Phase Dynamic Load/Model/PLL/Automatic Gain Control/Fcn2'

[Saurav]

Can you provide your Simulink Model to help you better.

Answer 1

[MULI]

Hi @Despoina Papageorgiou,

I understand that you are facing an issue with the Three-Phase Dynamic Load in your Simulink model, where the output per-unit voltage becomes N/A after 2.7 seconds.

• The issue you are experiencing is likely due to the large step size (0.02s) in your simulation.
• The Three-Phase Dynamic Load, which includes control loops like PLL and AGC, requires a smaller step size to accurately calculate power and impedance.
• Try to set the simulation step size to 100e-6 to 2e-6 seconds under Simulation > Model Configuration Parameters > Solver and observe the changes.