A power conversion apparatus includes power conversion circuitry including a plurality of sub-modules connected in series to each other, a control device to generate a control command for controlling operation of the plurality of sub-modules, and a relay apparatus to relay communication between the control device and the plurality of sub-modules. For each sub-module of the plurality of sub-modules, the relay apparatus generates path information indicating a communication path from the control device to the sub-module, and outputs the generated path information to the sub-module. Each sub-module of the plurality of sub-modules generates identification information of the sub-module based on the path information corresponding to the sub-module.