A power conversion apparatus and a power conversion system that ensure safety capable of reliably performing an emergency stop and have a failure monitoring function are provided. The command signal for emergency stop of the power conversion apparatus between the supervisory monitoring and control device and the power conversion apparatus is to be a dual system, and the supervisory monitoring and control device monitors a performance of emergency stop of the power conversion apparatus by delaying the start of operation for a predetermined time from the operation command signal output. The supervisory monitoring and control device check a soundness of the power conversion apparatus by generating a test operation signal during that delay period.