Power Factor Control Method Based on Virtual Capacitors for Three-Phase Matrix Rectifiers

Abstract

This paper proposes a novel input power factor control method based on a concept of virtual capacitors to provide unity input power factor for three-phase matrix rectifiers. The proposed algorithm introduces, at the input terminal of the matrix rectifier, an imaginary input capacitor generated by modifying a reference vector of the space vector modulation method. The virtual input capacitor, which is fictitiously built in parallel with an input LC filter, successfully compensates for the leading power factor of the LC filter of the matrix rectifier. Thus, the proposed method yields a unity power factor operation despite the presence of the LC filter of the three-phase matrix rectifier. In addition, under a condition when the unity power factor operation cannot be realized, the proposed algorithm adjusts a virtual capacitance to obtain a maximum achievable power factor operation. Because the proposed technique yields the input power factor control by introducing the virtual capacitor and adjusting a reference space vector, the proposed algorithm can be easily incorporated with conventional space vector modulation algorithms for the three-phase matrix rectifiers. Thus, the proposed method can control input power factor without employing proportional-integral controllers used in conventional power factor control methods for the matrix rectifiers, leading to simple control structure and straightforward tuning process for power factor control.