A carrier-based discontinuous space vector modulation for three-level NPC inverter

Abstract

This paper presents carrier-based discontinuous space vector pulse width modulation (DSVPWM) method for three-level three-phase neutral point clamped (NPC) voltage source inverter (VSI). Based on the relationship between space vector pulse width modulation (SVPWM) and carrier based modulation, a simplified DSVPWM method for three-phase inverter is introduced by skillfully arranging two zero voltage vectors. In this method, the conventional space vector modulator with equal division of zero voltage vector time is modified to generate different discontinuous modulating waves. The switching sequences for six basic types of discontinuous PWM are studied. It includes DSVPWMmax, DSVPWMmin, DSVPWM0, DSVPWM1, DSVPWM2, and DSVPWM3. According to the carrier-based PWM, simplified SVPWM, and traditional discontinuous PWM strategies, the DSVPWM strategies called as DSVPWMx, including six basic types of DSVPWM and eight novel types of DSVPWM, are proposed and studied. By this method, switching losses of inverter are optimized and life expectancy of inverter can be increased using a suitable discontinuous modulation technique. The proposed method is theoretically analyzed, and verified by simulation results.