A power flow control system for an interconnected power system, the interconnected power system comprising a plurality of electrical subsystems; an abstract framework configured to work as a utility maximiser under constraints (that applies to the electrical subsystems by specifying their capabilities, expected behavior and a simplified view of their internal state);and a plurality of agents. Each agent is responsible of one or a plurality of the electrical subsystems, comprises means configured to express an internal state of the electrical subsystem within a common system of coordinates, and has communication means configured to communicate among agents according to a protocol. The abstract framework means enables a composition of a set of the interconnected electrical subsystems into a further subsystem for which a further internal state is expressed within the same common system of coordinates used before, the further internal state being communicated with other agents according to the protocol.