Hybrid modelling and control of single-phase grid-connected NPC inverters

In this paper, a grid-connected single-phase neutral point clamped inverter is represented by a hybrid model with both continuous and discrete dynamics. A novel state-feedback switching control law is proposed in terms of linear matrix inequalities (LMIs) which can drive the output current to track a sinusoidal reference. The main advantage of this method is that the switching states of the inverter are directly determined by the controller. Another advantage is that the switching law can be obtained off-line, which significantly reduces the online computation burden. Then the neutral point voltage ripple is minimized by a capacitors voltage balancing controller. Simulation results confirm the feasibility and performance of the proposed control scheme.