Abstract: A power-supply system involving system interconnection includes a plurality of AC modules, each of which includes a solar cell module and an inverter unit which outputs a single-phase alternating current. The AC modules are connected to the single-phase three-wire distribution line such that the number of AC modules connected to the outer conductor R is the same as the number of AC modules connected to the outer conductor T. Each AC module has three junction pole pieces. Adjacent AC modules are connected to each other via a connecting cable connected to the junction pole pieces. Each AC module has a change-over circuit so as to be selectively connected to one of the outer conductors R or T. The power-supply system further includes an independent operation control device for independently operating the AC modules when the connection between the AC modules and the commercial electric power system is cut.