A New Approach for Three-phase Three-level Unity PF Rectifier Considering Alternative Performance Indices

The three-phase three-level unity PF rectifier can improve the power factor of three-phase rectifier. However, both the power factor (PF) and total harmonic distortion (THD) are degraded in low-output power region, because its "critical input inductor" is calculated for the nominal load condition. A novel reference compensation current strategy for three-phase three-level unity PF rectifier considering alternative performance indices was proposed based on the operation principle of this rectifier. The main concept of the proposed new design for optimal rectifier control lies in that the three-phase load currents are filtered through a current compensator, where the desired source currents after compensation are maintained sinusoidal/balanced or within permissible levels of current distortion and imbalance. In addition, the load power factor can be set to meet a specified target value. The simulation results show that the input power factor can be well improved and input current harmonics can be effectively eliminated under wide load variation.