A power conversion device that is configured to perform power conversion between a DC circuit and an AC circuit, the power conversion device comprising: power conversion circuitry including a plurality of sub modules connected in series to each other; a first control device and a second control device configured to generate a first control command and a second control command respectively for controlling operation of each of the sub modules; and a first relay device and a second relay device configured to transmit the first control command and the second control command respectively to each of the sub modules, wherein the first control device and the second control device are configured to receive, from a predetermined external device, instruction information indicating either a first system or a second system, as a system that controls operation of each of the sub modules, wherein the first system includes the first control device and the first relay device, and the second system includes the second control device and the second relay device, each of the first control command and the second control command includes: a drive command configured to drive a switching element (22A, 22B) included in each of the sub modules; abnormality determination information configured to indicate whether abnormality is present in a control device; and the instruction information, each of the sub modules includes: a PWM controller configured to perform PWM control for the switching element; and a selector configured to select either the first system or the second system, based on the abnormality determination information and the instruction information that are included in each of the first control command and the second control command, the selector selects the second system as a system to control operation of each of the sub modules, in response to occurrence of abnormality to the first control device that is detected based on the abnormality determination information of the first control command, even when the instruction information indicates the first system, and the PWM controller performs PWM control for the switching element in accordance with the drive command included in the second control command for the selected second system. power conversion circuitry including a plurality of sub modules connected in series to each other; a first control device and a second control device configured to generate a first control command and a second control command respectively for controlling operation of each of the sub modules; and a first relay device and a second relay device configured to transmit the first control command and the second control command respectively to each of the sub modules, wherein the first control device and the second control device are configured to receive, from a predetermined external device, instruction information indicating either a first system or a second system, as a system that controls operation of each of the sub modules, wherein the first system includes the first control device and the first relay device, and the second system includes the second control device and the second relay device, each of the first control command and the second control command includes: a drive command configured to drive a switching element (22A, 22B) included in each of the sub modules; abnormality determination information configured to indicate whether abnormality is present in a control device; and the instruction information, each of the sub modules includes: a PWM controller configured to perform PWM control for the switching element; and a selector configured to select either the first system or the second system, based on the abnormality determination information and the instruction information that are included in each of the first control command and the second control command, a drive command configured to drive a switching element (22A, 22B) included in each of the sub modules; abnormality determination information configured to indicate whether abnormality is present in a control device; and the instruction information, each of the sub modules includes: a PWM controller configured to perform PWM control for the switching element; and a selector configured to select either the first system or the second system, based on the abnormality determination information and the instruction information that are included in each of the first control command and the second control command, the selector selects the second system as a system to control operation of each of the sub modules, in response to occurrence of abnormality to the first control device that is detected based on the abnormality determination information of the first control command, even when the instruction information indicates the first system, and the PWM controller performs PWM control for the switching element in accordance with the drive command included in the second control command for the selected second system.