Predictive current control for grid-connected inverters under unbalanced grid voltage

Based on the mathematic models of grid-connected inverter under unbalanced grid voltage, the control strategy were proposed to implement the balance of three-phase current, eliminate the ripple in active and reactive power, in which the current reference of the positive sequence and the negative sequence for the different control targets was deduced. And then, based on the two-phase stationary reference frame, a predictive current control scheme was proposed to implement the accurate control of the positive sequence and the negative sequence current, which can eliminate the bad effects to the operation performance of grid-connected inverter, caused by the current sampling delay and the sequence decomposition. The feasibility of the proposed algorithms and control strategy were validated by experimental studies on a 3 kVA grid side converter system.