Current Optimization for Nonunity Power Factor and Unbalanced DC-Link Voltage in Three-Phase Vienna Rectifiers

The suppression of current zero-crossing distortion and dc-link voltage oscillations has been a key research focus for three-phase Vienna rectifiers in recent years. In addition, under variable power factor (PF) operation, the phase difference between the input current and grid voltage increases the likelihood of the Vienna rectifier entering a nonsynthetic interval at a high modulation index. This prevents the effective synthesis of the reference voltage vector, leading to severe current distortion and voltage oscillations. In order to reduce the impact of the nonsynthetic interval on the three-phase Vienna rectifier, this article proposes a nonunity power factor current optimization (NUPF-CO) strategy to effectively reduce the negative impact of the nonsynthetic interval on system performance. This strategy allows the three-phase Vienna rectifier to avoid current zero-crossing distortion, even under variable power factor operation and actively unbalanced output voltage, while ensuring good neutral point current disturbance suppression and improving voltage utilization. Finally, a 2.5 kW three-phase Vienna rectifier is constructed for verification. The performance of the proposed NUPF-CO strategy under variable power factor conditions is compared with that of conventional strategies.