A timing controller (C1) in an inverter, an inverter controller (C30), and a plurality of converter controllers (C21 to C26) are connected via a communication line (L2). The timing controller (C1) is configured to provide timing signals to the respective inverter controller (C30) and converter controllers (C21 to C26) in predetermined time cycles which have been set in advance. The respective timing signals are provided so as to prevent two or more of the inverter (30) and converters (21 to 26) from starting to be driven at the same time.
