D-Σ digital control for a three-level T-type grid-connected inverter

In this paper, a current control is studied based on D-Σ digital control to improve the grid-connected performance for a three-level T-type inverter. The control principle is analyzed in accordance with the single-phase equivalent circuit of the three-level T-type inverter. The influence of the neutral-point voltage on both output current error and modulation signal is discussed, and the relationship expression is deduced. Finally, a simulation circuit of 5kVA three-level T-type grid-connected inverter is built, which proves the effectiveness of D-Σ digital control, and verifies that the control has excellent dynamic and static performances.