A method to reduce zero-sequence circulating current in three-phase multi-module VSIs with reduced switch count

A new zero-sequence circulating current (ZSCC) reduction method for multi-module VSIs (MVSIs) consisting of P three phase inverters that are connected in parallel is proposed in this paper. Four-switch inverter modules are used instead of conventional six-switch modules to reduce cost. In the paper, the effectiveness of the proposed ZSCC reduction method is studied using selective harmonic elimination PWM (SHE-PWM). The proposed ZSCC reduction method can remove about P times the number of harmonics using the same switching frequency as compared to more conventional methods, as explained later in this proposal. The concepts discussed in the paper are confirmed with results obtained from an MVSI experimental prototype.