Nonlinear Backstepping Controller for Current Control of Grid-Connected Five-Level Inverter

This paper proposes the analysis and implementation of a nonlinear backstepping controller to regulate the current in Grid-tied five-level inverter system via an LCL filter. Designing a robust regulator for nonlinear systems is often a challenging task in control theory. The study addresses the challenges of enhancing the performance of the conversion system by selecting appropriate regulated variables and ensures synchronization between the signals of the grid and the five-level inverter. Additionally, it includes a grid current control using the backstepping control method. This method is based on the Lyapunov stability approach, involves switching a five-level inverter with high-frequency modulation, and employs Sinusoidal Pulse Width Modulation as the selected modulation strategy. The proposed system configuration and the implementation of the backstepping control method are discussed step-by-step to ensure the efficiency of the system analysis. Simulation results in the MATLAB/Simulink environment validate the theoretical analysis. The nonlinear backstepping controller demonstrates excellent performance in tracking reference signals and responds to abrupt changes in the reference, highlighting its effectiveness for current control in grid-connected inverter systems.