Parallel operation of PWM inverters for high speed motor drive system

This paper describes a topology with a parallel operation of PWM inverters for high speed motor drive systems. High speed motors have been widely used in industries to reduce system size and improve power conversion efficiency. However, the high speed motors sometimes suffer from core losses caused by PWM current ripples; noting that the phase inductance, L_s, of a high speed motor is smaller than that of ordinary motors, it is significant that the current ripple generated by a Pulse Width modulation(PWM) inverter becomes noticeable in the high speed motor. In the proposed topology, three PWM inverters are connected in parallel through nine coupled inductors. Compared to the PWM current ripple of the conventional single inverter system, that of the proposed scheme can be conspicuously reduced without the voltage drop at the inductors. In this paper, a theoretical analysis of the output voltage of the proposed topology is presented, and then the validity of the proposed method is verified by experimental results.