Direct power control with constant switching frequency for three-level PWM rectifier

This paper presents the mathematical model of the three-level voltage source PWM rectifier and deduces the relationships between instantaneous power and the vectors of the three-level rectifier from the theory of instantaneous reactive power. Then, a direct power control (DPC) scheme for three-level PWM rectifier with constant switching frequency is proposed. Space vector modulation (SVM) is applied to the scheme, and decoupling control for the active and reactive power during the dynamic course is realized. Compared to conventional DPC with bang-bang control by a switching table, the proposed method can not only realize the direct control for active and reactive power, but also operate under constant switching frequency. Experimental results show that unity power factor is achieved and the proposed method has the advantages of low harmonic distortion of current, excellent dynamic, and steady state performances.