Ups does not work on home generator

Question

hi
i just bought a APC back-ups Es 500v(BE 500y-IN)
it does not get charged or work on the home generator.
i stay in a small town in india and state electricity is very scarce an infrequent so we depend mostly in home generatoras.
i asked the service guy and he said may be the generator frequency is too low.
is there any device to get the right frequency or is there any thing i can try
please advice