Sliding Mode Control for NPC Converters via a Dual Layer Nested Adaptive Tuning Technique

In this article, on the basis of an existing dual layer nested (DLN) adaptive sliding-mode control (ASMC) strategy, an observer-based sliding-mode control strategy with an improved DLN adaptive tuning mechanism (IDLN-ASMC) is proposed for a three-level neutral-point-clamped converter. The proposed controller not only ensures good system performance but also mitigates two problems of the existing DLN-ASMC strategy. Meanwhile, three objectives are achieved. First, an adaptive supertwisting algorithm is utilized in the power tracking loop to converge power tracking errors to bounded regions in finite time. Next, a disturbance observer-based IDLN-ASMC strategy is proposed in the dc-link voltage regulation loop to regulate the dc-link voltage to its reference value. Finally, a simple proportional-integral controller is used in the dc-link voltage-balancing loop to reduce the voltage difference between the two dc-link capacitors. The results of simulation and experiment demonstrate the effectiveness and superiority of the proposed strategy.