Parallel connected multiple drive system using small auxiliary inverter for numbers of PMSM

This paper discusses a multi-parallel drive system for permanent magnet synchronous motors (PMSMs). This system proposes to use two different functions of inverter, a main inverter to drive parallel connected PMSMs and an auxiliary inverter to suppress the vibration of the motor speed. However, the power capacity of the auxiliary inverter depends on the speed response. In this paper, the performance of the proposed system is discussed. From the frequency characteristics, it is clarified that the power capacity of the auxiliary inverter is lower than 10% of the main inverter when the frequency components included in the speed command are less than 12 rad/s. As a result, the experimental results demonstrated that the proposed system can reduce the speed vibration from 400 r/min to nearly 0 r/min with damping control in the prototype of 1500-W PMSM drive system. The experimental results well agree with the theoretical analysis results.