I have a 3 gas gensets which has a problem of fluctuation in both voltage for about 6 to 8 voltage and fluctuation in frequency for about 3 to 4 Hz please advise for this genset and if this problem is related to AVR only or may it related to the governor also as this genset has an electronic governor
Also I need to add that the type of load that we have in this site is not stable and variable load (sucker rod) and also we have low PF for about 0.55
In this site we have other types of gensets and not suffering for this problem and these other engines have a mechanical governor

I do not have enough details to answer this properly, however, you may have a problem due to the type of load you have on this machine. Electronic controls for generator sets today us zero crossing to determine the appropriate frequency. If you have three phase or single phase rectifiers as the major load, voltage notching caused by semiconductor commutation could cause the frequency variation which in turn affects the load impedance thus changing the output voltage. Look for this type of loading characteristic and add filtering as needed to the voltage sensing circuit of your generator.