How to calculate electromechanical modes from Simulink power-system model?

Dear colleagues!

I have a power-system model in Simulink, built using Simscape library. The model includes several simplified synchronous machines, pi-section lines and impedance loads. I successfully perform load-flow calculations and time-domain simulations using Discrete phasor simulation type. Now I am interested in getting electromechanical modes of this model (frequencies in the range between 0.3 and 3 seconds). How do I do that? By using Model Linearizer I am able to obtain A, B, C and D matrices, but the eigenvalues of A matrix do not show frequencies I expect (they are much lower, in the range of 1e-4). Just in case I tried the same procedure on a Kundur 2-area model (power_PSS) in which electromechanical modes are known, but I am still having same problems.

I would appreciate any kind of support!

Answer 1

[Riya]

Hi,

Calculating the electromechanical modes of a power system in Simulink involves linearizing the nonlinear model around a stable operating point and then analysing the eigenvalues of the resulting linear state-space model.

You can follow the steps below:

• Simplify the Model: Simplify the model to isolate the electromechanical dynamics if possible. Remove or replace elements that contribute to fast dynamics that are not of interest.
• Consider using specialized modal analysis tools that are designed for power system stability analysis, such as Power System Analysis Toolbox (PSAT) or commercial software like PSS/E, which may offer more robust calculation of electromechanical modes.

For more information you can refer following article for more information:

https://www.mathworks.com/matlabcentral/answers/6621-electromechanical-actuator?s_tid=answers_rc1-2_p2_MLT