How to calculate the natural frequency of the power system.

I have a simulink model and i need to calculate its natural frequency which is used in a some othe calculation related to this model.

In actual, I create a model and the variables get values from the matlab command window because i write coding. I want to know about any command or any simulikn block that calsulate the natural frequency of the run model.

[Image Analyst]

Can't you just subtract the mean of the signal, then take the fft, then look for the frequency with the max value?

[Muhammad Asad]

first thanks for your response. I do the same like: 1st drag a block of mean then drag a block of fft and in coding i get the max value of fft output (maxfrq=max(out.fft)

I have a five differential equation system and i just put the output of speed block as the input of mean block. is it is true. spped is the required target in my system. it shows 1.034. or i need to do something different?

[Image Analyst]

sorry, I'm not famliar with Simulink. But you have to subtract the mean off the original signal, not from the FFT of the signal because if you don't, and the mean of the signal is not zero, then the max of the FFT will probably be at the DC (zero frequency) location, not at the dominant frequency location.

[Sam Chak]

Hi @Muhammad Asad

Can you search your Power Systems textbooks and show the equation or formula to determine the natural frequency of the power system?

This will probably help us to guide you how to achieve that in MATLAB/Simulink.

Answer 1

[Yash]

Hello Muhammad Asad,

I understand that you are facing issues while calculating the natural frequency of a power system.

Since you have the output signal of the model, calculating the natural frequency becomes straightforward. You can follow the steps outlined below:

1. Calculate the mean of the output speed signal using a mean block. This will provide you with the average value of the signal.
2. Use a subtract block to subtract the mean value from the original signal. This step helps eliminate the DC component of the signal, leaving only the oscillatory part.
3. Use the FFT (Fast Fourier Transform) analyzer of the Powergui block to analyze the resulting signal and determine the frequency with the highest magnitude. The FFT analyzer will provide you with the frequency spectrum of the signal, and you can identify the peak frequency from there.

If you encounter any issues while using the FFT analyzer in the Powergui block, you can refer to the following MATLAB Answer for assistance: https://www.mathworks.com/matlabcentral/answers/300733-fft-analysis-tool-in-powergui

I hope these steps help address your query.

Best Regards,

Yash