An Efficient Robust Power–Voltage Control for Three-Level NPC Converters in Microgrids
Lei Liu, Zhenbin Zhang, Yunfei Yin, Sergio Vázquez, Yuxin Zhao, Ralph Kennel
Abstract
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.