Design and implementation of FLC and SVSC techniques for MPPT battery charging and dual-leg DC–AC conversion in hybrid electric power systems

Abstract

Hybrid renewable energy systems (HRES) commonly rely on multistage power conversion structures, which increase circuit complexity, switching losses, and overall system cost, while potentially decreasing conversion efficiency. To overcome these limitations, this study proposes a single-stage hybrid electric power system employing a fuzzy logic controller (FLC) for maximum power point tracking (MPPT)-based battery charging and a sliding variable structure controller (SVSC) for the control of a dual-leg DC–AC converter. The FLC enables efficient extraction of the maximum available power from the photovoltaic source under changing irradiance conditions, whereas the SVSC provides effective output-voltage regulation and enhanced dynamic performance during load disturbances. By combining voltage boosting and DC–AC conversion within a single power-conversion stage, the proposed topology reduces the number of conversion stages and associated components, thereby simplifying the overall system structure and offering the potential to reduce switching losses and implementation costs. The proposed system was evaluated through MATLAB/Simulink simulations. The results demonstrate that the converter can convert a 105 V DC input into a regulated 230 V (RMS), 50 Hz AC output under both resistive and resistive–inductive loading conditions. The simulated voltage total harmonic distortion (THD) was 2.84% for the resistive load and 2.41% for the resistive–inductive load, while the corresponding current THD values were 0.28% and 0.68%, respectively. To assess the practical feasibility of the proposed system, a laboratory-scale prototype was developed and experimentally tested. The measured voltage and current THD values were 2.50% and 2.31%, respectively. The experimental voltage THD shows good agreement with the simulation results, whereas the comparatively higher current THD can be attributed to practical non-idealities and losses associated with the hardware implementation. Overall, the simulation and experimental results confirm the effectiveness and practical applicability of the proposed FLC–SVSC-based control strategy for single-stage hybrid renewable energy conversion systems.