Single-phase three-level grid-connected inverter based on direct adaptive fuzzy control

Abstract

Single-phase three-level grid-connected inverter is widely used in high-voltage applications, which can be connected to the grid through a single inductor (L filter) or an LCL filter. The control schemes for an LCL-based grid-connected inverter are more complex than those for an L-based one to damp the resonance of the LCL filter. In this paper, a robust nonlinear direct adaptive fuzzy control scheme is proposed to control both the L- and LCL-based inverters. The principle of the inverter is introduced, especially the space vector pulse width modulation method for the single-phase three-level inverters. Then, the theory of the direct adaptive fuzzy control is described. Based on the theory, the current controller for both types of grid-connected inverters is designed. The closed-loop stability is proved based on the Lyapunov theory. Finally, simulations are conducted to verify the effectiveness of the controller. The results show that both the L- and LCL-based grid-connected inverters operate well with strong robustness under the same controller.