Control of grid‐connected converter based on model prediction control under unbalanced grid voltage

Abstract

Due to the asymmetry of load, the ageing of transmission line, the asymmetry of power grid voltage and so on, grid-connected converter often appears grid voltage unbalance at the point of common coupling. Especially for some high-power grid-connected converter device, if the unbalanced conditions is ignored, it will produce non-characteristic harmonics, three-phase grid current unbalance and so on that will affect the stable operation of grid-connected converter, even ruin it. Therefore, it is necessary to study the control of grid-connected converter under unbalanced grid voltage. In view of the advantages of model predictive control in high-power converter, the control of grid-connected converter under unbalanced grid voltage based on finite control set model predictive control is studied. The goal is to control the three-phase grid current balance and enhance the stability operation of the grid-connected converter under unbalanced grid voltage. The grid-connected converter is modelled in two-phase stationary ( αβ ) coordinate system, and the model predictive control of grid-connected converter is deduced under unbalanced grid voltage. Based on the theoretical analysis, the simulation results show the effectiveness of the proposed control strategy.