OUTPUT POWER CONTROL APPARATUS

An output-power control apparatus is provided in an electric power system connecting a secondary battery system (2) and a power generator (3) in parallel, and controls output power of the electric power system. The output-power control apparatus detects output power of the power generator (3), and controls output voltage of the secondary battery system (2), based on a value obtained by subtracting the detected output power of the power generator (3) from an output power instruction for controlling the output power.