Active Vector Modification for Circulating Current Suppression of Paralleled Inverters Using Two-Step Sector Indexing-Based Discontinuous SVPWM

Due to the discrepancy of paralleled inverters, the zero-sequence circulating current (ZSCC) is a critical issue in a paralleled inverter fed permanent magnet synchronous machine (PMSM) drive system. The conventional solution to this issue is to adjust the duration of two zero vectors; however, it will not be appropriate under the discontinuous space vector pulsewidth modulation (DSVPWM) control using only one zero vector. For overcoming the above issues, an active vector modification (AVM)-based ZSCC suppression and a two-step sector indexing (TSSI)-based DSVPWM are proposed in this article. It uses both reference voltage and current vectors to jointly determine the drive signals in a two-step manner, which avoids the circulating current jump due to the coexistence of different zero vectors and can also reduce the switching loss by 50% in theory. Meanwhile, the low-frequency ZSCC can be online suppressed by a proposed real-time modification of durations of active vectors, which is finally verified together with the proposed TSSI method on a PMSM fed by two paralleled inverters.