A power source can have a significant impedance that can make power factor correction of a resistive load a possibility. For example if the output impedance of the generator is net inductive (the most likely situation) then to give the load maximum power a capacitor in series is used to counter the inductive impedance that would otherwise drop a few volts.
It's called obtaining maximum power transfer and IS related to the impedance of the source. See the diagram below: -
The source has loss Rs and series inductance Xs. The load has a capacitance placed in series that totally cancels the inductive reactance and on the right you are left just with just the equivalent circuit.
This is power factor correction of a source rather than a load.