An Efficient Robust Power-Voltage Control for Three-Level NPC Converters in Microgrids

High penetration of power converters may lead to power ripple, voltage swings, and weak antidisturbances for microgrids. Confronting these issues, this work proposes a robust control scheme, discrete-time super-twisting observer (DSTO)-embedded quasi-integral sliding-mode control (QISMC), for a three-level neutral-point-clamped power converter system, dramatically enhancing power/voltage regulation performance and antidisturbance capability. A fast convergence DSTO is deployed to offset multidisturbances caused by parameter mismatches, unknown loads, current path changes, switch mode noise, and self-compensating power/voltage tracking biases in QISMC. To further mitigate power/voltage steady-state error and boost system robustness, a new quasi-integral sliding-mode surface is built, inherently improving power/voltage tracking performance. Experimental data confirm that the proposed control outperforms the discrete-time extended-state-observer-based QISMC, DSTO-based quasi-sliding mode control, and discrete-time proportional-integral control in power/voltage, grid current harmonics, and robustness.