Multidisturbances Compensation for Three-Level NPC Converters in Microgrids: A Robust Adaptive Sliding Mode Control Approach

Reliable control schemes are critical to ensuring converter operation in microgrids. This work proposes a robust adaptive sliding mode control for the three-level neutral-point-clamped power converter with multidisturbances. Specifically, an adaptive observer-based proportional (P) voltage controller is proposed to accurately and quickly regulate dc-voltage in real-time identifying unknown equivalent dc-loads, compensating for the active power reference. To track the reference, a disturbance observer-based integral sliding mode controller (ISMC) is adopted to dramatically enhance the power tracking performance in case of parameter mismatches and bias caused by current path changes and switch mode noise. In addition, a sliding mode observer coupled with P control is established to balance dc-link (two) capacitors, rejecting harmonic injection and power ripple behaviors. Experimental data confirm that the proposed control scheme outperforms super-twisting observer-based ISMC, super-twisting algorithm, and proportional-integral control schemes in the transient/steady state operations in terms of dynamic response, grid current harmonic distortions, and robustness.