Fuzzy Logic System-Based Sliding-Mode Control for Three-Level NPC Converters

Nowadays, power converters have become the key to overcoming many challenges, so as to achieve more efficient transportation systems. Sliding-mode control (SMC) has become one of the preferred choices for power conversion applications because of its insensitivity to external disturbances. However, it is a challenge to suppress the chattering phenomenon. To solve this problem, in this article, a fuzzy logic system-based SMC strategy is proposed for three-phase three-level neutral-point-clamped power converters to improve the disturbance rejection ability, dc-link voltage regulation ability, and power tracking ability with good chattering suppression ability. The proposed controller is composed of three control loops. In the power tracking loop, a fuzzy super-twisting algorithm is proposed to force the active power and reactive power tracking their reference values. A fuzzy observer-based fuzzy SMC method is used in the dc-link voltage regulation loop to regulate the dc-link voltage to the reference value. Then, in the dc-link voltage balancing loop, a simple proportional-integral control strategy is utilized to balance the voltages of two dc-link capacitors. Finally, three groups of experiments are provided to validate the effectiveness and superiority of the proposed strategy.