A voltage at a point of common coupling (PCC) between a photovoltaic (PV) system and a power grid is regulated by a controller having a gain determined according to a gain function that is a function of a time. The gain function is determined based on an error between the voltage measured at the PCC and the reference voltage, and the gain is updated according to the updated gain function and a current instance of time. The controller generates a modulating signal using the updated gain and the voltage at the PCC is regulated according to the modulating signal.