Sliding mode control for a single-phase grid-connected H-bridge NPC inverter with a symmetrical LCL filter.

Inverters are essential in converting solar panel-generated direct current (DC) into alternating current (AC) for seamless integration with electrical grids. This paper presents the modeling and analysis of a single-phase grid-connected H-bridge neutral point clamped inverter using the Sliding Mode Control (SMC) method. Addressing challenges in meeting control objectives – like fast dynamic response, precise reference tracking, robustness against parameter variations, cost-effectiveness, and compliance with grid standards such as low harmonic distortion and minimal DC transfer to the grid – the study employs the boundary layer method to minimize the SMC method's chattering phenomenon. The use of proportional-resonant (PR) control maintains the robustness of the SMC method against parameter changes, while the boundary layer effectively reduces chattering. A transfer function between the measured grid current and the reference grid current was also derived to investigate the effect of the filter parameters on the system. Furthermore, the proposed control method naturally mitigates resonance in the LCL filter and minimizes leakage current via a symmetrical LCL filter and specialized modulation scheme. Simulations conducted using MATLAB/Simulink® validate achievement of control objectives, steady-state performance, dynamic response, robustness to parameter variations, and adherence to grid standards. [ABSTRACT FROM AUTHOR]