Research Of Neutral Point Voltage Balance Of Vienna Rectifier Based On One-Cycle-Control

As a typical kind of three-level neutral point clamped type rectifiers, VIENNA rectifier has the advantages of less switches, high power factor, low voltage stress on power device and simple control structure. As an inherent question of neutral point clamped type rectifiers, the question of the fluctuation in the neutral-point-potential is a very important content while studying VIENNA Rectifier.Firstly, this paper described the topology of VIENNA Rectifier, introduced the characteristics and advantages of a new six-switch VIENNA rectifier topology compared to traditional three-switch VIENNA rectifier topology. It also introduces the single-phase and three-phase rectifying operating principle of six-switch VIENNA topology. Furthermore, the mathematical models of VIENNA rectifier in static abc coordinate system, two-phase α β coordinate system and two-phase rotating dq coordinate system were studied.Secondly, this paper introduced the basic theory of one-cycle control (OCC) and OCC-APFC technique. According to the OCC-APFC technique, two operating modes are described. They are three phase independent model and decoupling mode of dual-boost in series. The part of control of the two modes were analyzed in detail.In this paper, for six-switch VIENNA rectifier topology, two switches of every phase were controlled separately, which makes circuit loss less than synchronization control.Thirdly, for question of the fluctuation in the neutral-point-potential(NPP), a detailed analysis of fluctuation mechanism of NPP was shown in this paper with the OCC based three-phase three-level VIENNA rectifier as the research object. The three times harmonic of input currents and the improved zero-sequence voltage were proposed to inject into the three phase sampled currents. The influence of three times harmonic injection to NPP was also analyzed. Based on the above, the equalizing voltage ring was proposed to introduce in the traditional OCC strategy. These control strategy could restrain the fluctuation of NPP. Above all, this paper also discussed the optimization inject coefficient.At last, this paper designed parameter for the main components of the main circuit through theoretical analysis and had circuit simulation by using matlab. Through simulation, VIENNA rectifier could achieve the goal of power factor correction either work in three-phase-independent model or work in decoupling mode of dual-boost in series. The fluctuation of NPP had been restrained by adding the NPP control strategy which proved the correctness of this paper.