Research On Digital One-Cycle-Controlled VIENNA Rectifier Based On DSP

With the continuous development of power electronics technology, because of the stable DC voltage output and less low-frequency harmonic contained, the fully-control rectifier devices have been widely applied in various sectors of social production, playing an positive role in improving production efficiency and promoting economic development and have been an indispensable part of morden industrial production processes. VIENNA rectifier is a typical three-level rectifier circuit, compared with the two-level PWM rectifier, harmonic contained by input current is less at the same switching frequency and control mode and the voltages each switch beared is only half of the DC bus voltage. Compared with other three-level PWM rectifier, VIENNA rectifier also has the advantage of containing less switches and no danger for direct conduction, it attracts widespread attention from home and abroad.Firstly, this paper analyzes the topology and working principle of the VIENNA rectifier in detail, also deduces the mathematical model of VIENNA rectifier under three-phase static abc coordinate system using state-space aceraging method. Then, it studies the basic theory of one-cycle control in depth, analyzes the theory of one-cycle-control method controlling VIENNA rectifier by deriving formulas and the core control equations have been obtained. This paper proposes a realization method of digital one-cycle-control controlling VIENNA rectifier, compared with analogue one-cycle-control, digital one-cycle-control has the advantages of high integration degree for components and more flexible for designing control method.Subsequently, to solve the problem of the unbalance of neutral-point-potential for three-level VIENNA rectifier, this paper proposes the third-harmonic injection method, which can obviously reduce the AC capacity voltage pulsation. Based on third-harmonic injection method, it further injucts zero sequence component into bridge switch function to eliminate neutral point deviation, and form improved neutral-point-potential balance method. This method can eliminate neutral-point-potential pulsation and control the capacity voltage in the ideal range.Finally, it designs the software and hardware system for VIENNA rectifier in detail, containing selection for main circuit parameters selection, designing for controlling circuit and software system and building the experimental platform. It realizes the digital control using one-cycle-control for VIENNA rectifier through experiment, besides, the simulation and experimental results under balanced and unbalanced load also verify the effectiveness of proposed methods.