Reference Voltage Self-Equalization-Based Modulation Strategy for Open-End Winding PMSM Fed by Dual Three-Level Inverters With Common DC Bus

For the open-end winding permanent magnet synchronous motor (OEW-PMSM) fed by dual three-level inverters with a common dc bus, it is necessary to balance the neutral point (NP) voltage and suppress the zero-sequence current to improve system performance. The traditional methods to solve these two problems are usually contradictory and are difficult to obtain satisfactory results. This article proposes a novel modulation strategy to deal with this dilemma. In this strategy, the NP voltage balance is achieved by automatically equalizing the distribution proportion of the reference voltage of OEW-PMSM between the two inverters. At the same time, the strategy makes full use of the control freedom brought by dual inverters to control the three-phase voltages of OEW-PMSM independently, in order to ensure that the average value of zero-sequence voltage in a sampling period is zero in any case, and thus greatly reducing the zero-sequence current. The experimental results verify the effectiveness and feasibility of this strategy.