Model-predictive current control of grid-connected inverters for PV systems

Abstract

According to the mathematical model of three-phase grid-connected inverters, a model-predictive current control method is proposed in the two-phase static αβ-frame. Based on principle of model predictive control, a predictive model of grid-connected currents in the αβ-frame is established by using only once coordinate transformation to assess different voltage vectors of inverters and predict all possible output values. The voltage vector which minimizes the cost function is selected. Then the corresponding switching state is applied at the next sampling time to track the reference current. The proposed strategy has small amount of calculation and easy to be implemented. Simulation result explains that if the reference currents change dynamicly, model predictive current control has the ability of fast current regulation. The result shows that if the light intensity changes, the model predictive current control can track the maximum power point of the photovoltaic cell rapidly and transport active power to the grid. The output currents of the inverter change smoothly and low harmonic distortion.