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Currently VIENNA rectifier is getting more and more applications due to its advantages of simple structure, high power density and low switching stress. However, for the VIENNA rectifier, neutral-point voltage unbalance and neutral-point oscillation issues are still not well solved, which may reduce the capacitor life, deteriorate the ac input current, and even endanger the reliable operation of this converter. At present, the commonly used method is adjusting the action time of the redundant small vectors through the deviation of the capacitor voltage, which can solve the neutral-point voltage unbalance issue, but cannot suppress low-frequency oscillation of neutral-point voltage. A method of adjusting the action time of redundant small vectors by the dynamic adjustment factor is proposed in this paper, which can solve neutral-point voltage unbalance and neutral-point voltage low-frequency oscillation issues synchronously by making the amount of neutral-point charge deviation be compensated to zero during the adjacent switching period. Control performance comparison between the adopted method and traditional method is then analyzed in this paper. Finally, the feasibility and effectiveness of the proposed method are verified by simulation.
Inspec keywords: capacitors; voltage control; power capacitors; switching convertors; electric current control; rectifying circuits; PWM invertors
Subjects: Power convertors and power supplies to apparatus; Other power apparatus and electric machines; Voltage control; Control of electric power systems; Capacitors; Current control