## Answer

Jun 07, 2018 - 04:32 AM

Hi,

maybe these plots and pieces of information help you to understand my problem:

I have the simple gird that you can find attached and at the simulation time of 0.3 seconds I start adding a disturbance voltage source to the grid. For analyzing the harmonics, I use the FFT component of the master library.

My base frequency of the FFT is 50 Hz and I increase the frequency of the disturbance voltage source by 50 Hz in every run. For frequencies that are couples of 400 Hz I get some unstable which are not zero. Do you know why? Is it a numerical error and how can I get rid of it? Unfortunately, I do not know how you change the numerical integration method in PSCAD.

Furthermore, I have to mention that the results become better when I simulated with a lower solution time step. At first, the solution time step was 50 µs. With a solution time step of 5 µs I have these instabilities only for 2 or 3 frequencies.

Thanks!!!

Niklas

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