Second-Order Sliding-Mode Control for Three-Level H-Bridge-Based Unified Power Quality Conditioner With Vanilla Feedforward Neural Network

This article proposes a modified three-wire three-level H-bridge-based unified power quality conditioner (UPQC) without any transformer in the shunt part and controlled by using second-order sliding-mode control (SOSMC). Thus, this topology has less component count than that in the flying-capacitor- and neutral-point-clamped-based UPQC. The isolated operation of the series part of the UPQC leads to distortion in the mitigated load voltage. An SOSMC based on the supertwisting algorithm is proposed to defeat this problem. The SOSMC eliminates the differentiation requirement, thereby suppressing noise amplification compared to the first-order sliding-mode control (FOSMC). In addition to these advantages, the chattering problems are also minimized compared to FOSMC. Thus, this technique provides robustness and dynamic response during systems' external and parameters' perturbation. Furthermore, in the SOSMC controller, the compensation voltage and current references are predicted by using an artificial neural network (ANN). The ANN model uses a vanilla feedforward neural network with only two hidden layers. The proposed ANN is developed by considering the instantaneous and delayed components. Consequently, it allows for a simpler model by reducing the number of hidden layers. The total harmonic distortion (THD) of the mitigated voltage is reduced to 0.65% and the mitigated current THD is 1.22%.