A system and method for controlling a grid-connected inverter to provide negative sequence current during unbalanced grid operating conditions. The system uses a combination of feedforward and feedback controls to compute voltage signals which are used to control the inverter switches. The system includes both positive and negative sequence current controllers with voltage feedforward terms. The measured grid voltage is directly fed forward to the positive sequence control through a predictive algorithm, so that the instantaneous voltage information is kept, reducing the influence of grid voltage harmonics on the quality of the output current. The predictive voltages include positive, negative and harmonic component information of the grid voltage signals.