Model-predictive control of three-phase voltage source rectifiers under unbalanced grid voltage conditions

A new indirect power control strategy based on model-predictive current control (MPCC) for three-phase voltage source rectifiers (VSR) is proposed. The proposed strategy regulates the instantaneous AC-side power to ensure stable DC-side voltage under unbalanced gird voltage conditions while no phase-locked loop (PLL) or coordinate transformations are needed. This presentation analyses the influence of AC-side inductance on the reference currents, and deduces the direct relationship between the grid-side current and the AC-side power with a basis of AC-side power mathematical model. To eliminate the impact of AC-side inductance on AC-side power and stabilize the AC-side power under the unbalanced input voltages, MPCC was utilized to regulate the grid-side current. Experiments on a VSR prototype were carried out to validate the effectiveness of the proposed strategy, and the results demonstrated that the ripple of DC-side voltage was reduced and the performance of VSR under unbalanced grid conditions was improved.