In shunt active power filter design, Kp and Ki values of PI controller for inner current control depends on crossover frequency. How can we select this frequency? What is the criterion to select proper crossover frequency. Is it depending on switching frequency? If Fs is switching frequency what should be the crossover frequency(Hz)? Kindly explain in detail
Dear Muhammed,
Theoretically, Crossover frequency is a property of the transfer function to be controlled. I assume you have a transfer function. If you do, then plot the bode plot of the transfer function and the frequency at which the magnitude plot crosses zero is the crossover frequency, and the difference between the corresponding phase angle and -180 deg. is know as the phase margin.
cross over frequency decides the speed of your controller by which the actual output (voltage or current) of your circuit follows the reference input. If the plant for which you are planning to design the controller is SMPS type of thing, then generally we take the cross over frequency as 1/5 to 1/10 of switching frequency of SMPS.
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