Design and Evaluation of Different Order Sliding Mode Control Strategies for Current Control in T-Type Grid-Tied Inverters

This paper presents the design, implementation, and comparative analysis of three current control strategies for a 0.2 MW three-phase Neutral Point Piloted (NPP) T-type inverter connected to the grid. The study compares Proportional-Integral (PI) controller, a first-order Sliding Mode Controller (SMC), and a Pseudo-Second-Order Super-Twisting Sliding Mode Controller (STSMC), all applied to the inner current control loop. The inverter is modeled with an RL output filter for current shaping and grid interfacing. While PI controllers offer simplicity, they suffer from limited disturbance rejection and tracking performance. Classical SMC improves robustness but introduces chattering. The proposed STSMC reduces chattering while preserving the benefits of SMC. Simulation results in MATLAB/Simulink assess each controller's performance in terms of power injection and harmonic compliance with IEEE 519. The study highlights the superior transient and steady-state behavior of higher-order SMC methods.