Standard Extended State Observer (SESO) and Sliding Mode Control (SMC) Combined Methods for Estimating States of the Photovoltaic (PV)/Boost Converter/DC Load System Subject to Mismatched Disturbances

This paper investigates the combination of the sliding mode control (SMC) and standard extended state observer (SESO) methods for estimating the states of a Photovoltaic system associated with a boost converter and DC load subject to mismatched disturbances. To assess the unknown state and the internal disturbance, including the external disturbance of the PV/Boost converter/DC Load system, the SESO based on Multiple Input Multiple Output (MIMO) systems is constructed around the nominal dynamic model for this purpose. Then, the sliding mode control is proposed to track the set references during disturbed periods. To ensure system convergence, the stability analysis of the system in the permanent regime, the extended state system, and the sliding mode control are studied. The robustness of the mixed proposed method has been tested against perturbations from the PV voltage and DC load current. It shows that the variation of the PV voltage and DC load current slightly influences the boost converter current and the DC bus voltage. On the other hand, there are gaps between the estimated and real disturbance parts (d1 and d2). However, even though the mixed methods do not accurately estimate the disturbance parts during the perturbed periods, they are robust to the studied system’s principal states (inductance current IL and bus DC voltage). Furthermore, the design and dimensioning of the gains used for good state stability are more structured. The simulation results, the performance indicators and the stability analysis of the mixed methods (SESO and SMC) demonstrate the effectiveness and robustness of the principal states of the PV/Boost converter/DC Load system.