Three-Phase Reference Voltage Independent Control-Based Discontinuous Modulation Algorithm for Open-End Winding PMSM Fed by Dual Three-Level Inverters With Common DC Bus

This article proposes a novel modulation strategy forthe open-end winding permanent magnet synchronous motor (OEW-PMSM) fed by dual three-level inverters with common dc bus. First, by constructing a virtual orthogonal zero-sequence current, the tracking of the sinusoidal signal is transformed into the tracking of the dc signal, which improves the performance of suppressing the zero-sequence current. Second, making use of the characteristic that the phase voltage of the OEW-PMSM can be controlled independently, the neutral point voltage is balanced by synchronously adjusting the reference voltages of the dual inverters in each phase, which does not need to inject zero-sequence voltage like in the traditional method and will not conflict with the suppression of the zero-sequence current. Finally, by carefully setting the adjustment direction and amplitude of the reference voltages of dual inverters, the switching times are reduced to the same level as that of the single inverter, and the switching loss of the two inverters is equalized. The experimental results verify the effectiveness and feasibility of this strategy.