Multiobjective Coordinated Control Strategy for Grid-Connected Inverter under Unbalanced Voltage Conditions

Abstract

To improve grid-connected inverter operation performance, a power oscillation and current harmonic suppression coordinate control strategy that considers the problem of overcurrent is proposed in this work. First, the internal relationship between power fluctuation suppression and current balance is analyzed, and then, combining dynamic regulation of the active and reactive power settings, the peak value of the grid-connected current is limited within a safe range. Second, a simplified Fourier transform algorithm is proposed for the detection of fundamental positive and negative sequence vector components and band-pass filtering the three-phase input signals. By simplifying the transform and introducing a recursion algorithm, the online computational complexity is reduced and the controller based on this algorithm is used as an inner current loop regulator. Finally, the controller was investigated using simulations, and experimental results indicated that the output power quality of the grid-connected inverter under unbalanced grid voltages can be substantially improved.