Virtual Flux Direct Power Control for Vienna Rectifier Under Unbalanced Grid

Abstract

The Vienna rectifier is being broadly utilized in many industrial applications, which makes it essential to address its challenges. This article conducts the virtual flux-based direct power control and proposes an improved switching table for the Vienna rectifier under a balanced or unbalanced grid's voltage. Accordingly, the proposed method improves the THD of the three-phase input current when the grid voltage is unbalanced. Moreover, employing the virtual flux concept eliminates using three-phase input voltage. This results in reducing the cost of the converter. One of the challenges in the Vienna rectifier is to consider the current direction in the control design. Accordingly, the proposed switching table is designed based on the input current's sector. Furthermore, the positive and negative sequences of the input currents and virtual flux are utilized to correctly estimate the instantaneous input active and reactive power under the unbalanced grid voltage condition. Moreover, the proposed method can balance the output capacitors in balanced and unbalanced grid voltage conditions. This method possesses a high dynamic response due to hysteresis bands. Finally, a 430-watt laboratory prototype of the Vienna rectifier is implemented, and the accuracy of the proposed VFDPC is verified through the experimental results.