Direct Power Control of Three-Phase AC/DC Voltage Source Converters Under Unbalanced Conditions

This study introduces a direct power control (DPC) strategy for voltage-source converters (VSCs) connected to the grid, specifically when the network voltage is unbalanced. The DPC strategy is compared to a voltage-oriented control (VOC)-based PI controller strategy. The proposed method comprises a positive and negative sequence controller, which adjusts the output active and reactive power and removes the ripple of currents, respectively. The objective of the control is to eliminate negative current sequence components by regulating the instantaneous power flow while also reducing output current harmonics and power ripples. The mathematical model of the three-phase AC/DC VSC under unbalanced working principles and control strategies is discussed in-depth. A simulation is conducted using the MATLAB/Simulink platform to demonstrate the effectiveness of the proposed method.