Even when a fault occurs on an electric power system, a command signal based on appropriate calculation is given to a distributed power supply. Provided is a control apparatus configured to control a plurality of distributed power supplies connected to an electric power system. The control apparatus comprises: a first calculation unit configured to calculate in advance reactive electric power to be output by each of the distributed power supplies in the event of a fault on the electric power system; and a command output unit configured to output, to each of the distributed power supplies, a command signal for causing each of the distributed power supplies to output the reactive electric power calculated in advance by the first calculation unit when it is detected that a fault has occurred on the electric power system.