The main purpose of this research project is to develop a system theory of more advanced generation power system control in order to achieve a harmonized power supply under a large penetration of photovoltaic (PV) power systems. More specifically, this project aims to develop a power system control framework and methodology fully exploiting PV/demand power prediction as well as focusing on functions and properties of a middle layer consisting of various kinds of power aggregators such as demand-response aggregators, electricity-trading balancing groups, and cooperative electric power converters in addition to both sides of supply and demand. This research is performed from the following five viewpoints: PV power prediction, supply and demand control, consumer-side control, control of power transmission and distribution systems, and basic systems theory.