Why is there DC offset present and how can this be removed?

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I have a simple system as shown below:
consisting of a 11kV three phase voltage source with parameters:
Phase shift: 0
Frequency: 50Hz
Source impedance: X/R ratio of 3
SCL: 10e6
This is simply connected to a 11kv/400V transformer with an open circuit on the other side. The transformer has values:
Rated Power = 1.2e6
Frequency = 50Hz
Winding 1 = Wye with N port
Winding 2 = Delta 1 o'clock
The transformer impedances are:
This is a very simple circuit but I'm getting very detrimental DC offset in the currents which is producing a 50Hz component in power:
Shown above are the three phase currents. Why is there so much DC offset? and how can this issue be solved?

Answers (1)

Joel Van Sickel
Joel Van Sickel on 22 May 2023
The issue is that the initial conditions are unbalanced and as it's an open circuit with very little current flowing, it'll take a very long time for the system to reach it's steady state balanced operation. You can set the system to start in steady state in the solver configuration block options to fix this problem.




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