Investigation of optimal operation method for Permanent Magnet Synchronous Motor drive system with 3-level inverter

In this paper, an optimal converter drive method for Permanent Magnet Synchronous Motor (PMSM) with a 3-level inverter is discussed in terms of loss minimization. The 3-level inverter can change an operation mode between two modulations namely, PWM and 1´pulse modulation at a decided point. In this paper, we discuss the interchange point for the two modulations subject to the total loss of PMSM drive system in regards to the motor speed. First, the analysis on intersection point between PWM and 1´pulse modulation is demonstrated, and then the results show, that the motor drive system achieves the highest efficiency with PWM before the intersection point. On one hand, implementation of 1´pulse modulation can achieve the highest efficiency.