A power system is provided for controlling a connection point power at a connection point with a power grid D. The power system includes a processing device that calculates a guidance command value for controlling the connection point power to achieve a target power, and a plurality of power control devices that each control the output power of mutually different types of control targets, based on a common guidance command value inputted from the processing device. Each of the plurality of power control devices calculates a target value of the output power, based on an optimization problem including a common evaluation function. The evaluation function includes the guidance command value and a design parameter for which a setting value set for each of the plurality of power control devices is substituted.