Modified Back-Stepping Sliding Mode Controller With Robust Observer-Less Disturbance Rejection for DC Microgrid Applications

The proportional-integral-based double-integral sliding mode control suffers from linearization issues, restricted eigenvector-based state trajectory placement, and reduced robustness. To address these issues, this article describes a reduced-order dual-loop adaptive feed-forward double-integral back-stepping sliding mode control technique for a dc–dc converter used in dc microgrids. The proposed technique enables an observerless mitigation of unmodeled uncertainties using an adaptive feed-forward compensation. An ultimate compensatory feed-forward term is introduced to circumvent overall unmodeled converter uncertainties. The compensatory term also ensures a chattering-free faster reaching condition, that is selected based on a nonlinear pseudo sliding manifold (PSM). PSM is a non-singular extended-order fixed-time convergent manifold. The proposed technique uses double-integral back-stepping method to derive the control signal and PSM to mitigate the uncertainties. ADC and sensor uncertainties are corrected using a higher-order generalized polynomial weighted least squares convex optimization. To further support the compensation action, feed-forward constants of the proposed control loop are tuned online using a hybrid controller design approach considering loop shaping analysis, boundary conditions of parameter variations and small-signal closed-loop stability analysis. Experimental verification of the proposed control technique is carried out along with simulation analysis to ascertain the proposed technique against different test conditions, and comparisons are drawn with conventional techniques.