In a motor drive system with inverter parallel connection, a laying cable impedance is identified by a test pulse, and a cross current suppression control gain is optimized to provide a power conversion apparatus that does not require a coupling reactor. In the motor drive system 1 in which the outputs of A-bank and B-bank inverters 20A and 20B are connected in parallel, a test pulse is outputted from the drive control unit 30 provided with the PWM controller 33 to the A and B bank inverters before operation. The laying cable impedance is identified from the DC voltage Vdc at the time of test pulse output and the response currents IA and IB. An adjustment gain is calculated from the ratio of installed cable impedance to specified cable impedance. Then, the proportional gain KP is multiplied to optimize the adjustment gain, and an on-delay time based on the optimized adjustment gain GL×KP is calculated during operation. The gate signal corrected by the calculated on-delay time is outputted to the corresponding inverter gate.