A control system for a photovoltaic (“PV”) power plant that includes a plant-level control system for implementing plant-level control functions at power generation sites of the plant, a supervisory system for supervisory control and data acquisition of the plant, and a communications network connecting the plant-level control system, the supervisory system, and plant devices is described. Methods of controlling a PV plant using the plant-level control system and the supervisory system and methods of regulating power characteristics in power generation sites are also described.