SINGLE PHASE GRID CONNECTED INVERTER CURRENT CONTROL METHOD BASED ON SMC WITH LCL FILTER

Abstract

A novel current control technique for a single-phase Neutral Point Clamped (NPC) multilevel inverter has been proposed, which is used to inject power into the grid and regulate the DC link voltage. The primary challenge lies in controlling the system due to the LCL filter's resonance and the difficulty in generating the filter capacitor's reference voltage. To address these issues, a novel Sliding Mode Control (SMC) algorithm is introduced, which inherently suppresses the LCL resonance without additional damping methods. The system employs a Multiple Loop Control (MLC) structure, featuring an outer current control loop and an inner proportional resonant (PR) voltage control loop. This inner loop effectively minimizes the capacitor voltage steady-state error and mitigates the SMC-induced chattering, thereby enhancing overall system performance and robustness. Furthermore, a hysteresis band switching technique with a dual frequency band is used for pulse generation. Simulation and experimental results, conducted on a three-level NPC T-type inverter, validate the effectiveness and robust performance of the proposed control strategy under varying conditions and external disturbances.