Observer-Based Control Using Super-Twisting Technique for a PV-Wind-HESS-Based DC Microgrid Feeding Constant Power Loads

This article introduces a novel control strategy for a dc microgrid with integrated photovoltaic (PV) and wind energy sources, combined with a hybrid energy storage system (HESS) comprising a battery and a supercapacitor, feeding constant power loads (CPLs). The supercapacitor’s high power density is essential for absorbing transient power components, thus extending the battery’s lifespan. However, tightly controlled power electronic converters in this system, which behave as CPLs, potentially lead to instability. To address this, a control method based on super-twisting control (STC) and modified super-twisting observer (MSTO) is proposed for the HESS’s bi-directional converters. This approach improves the stability margin, enhances dynamic performance, and tightly regulates the dc bus voltage. In addition, a super-twisting sliding mode controller (STSMC) is employed to track the current reference from the maximum power point tracking (MPPT) algorithm under varying wind speeds in a permanent magnet synchronous generator (PMSG)-based wind system. Theoretical analyses and both simulation and experimental evaluations validate the effectiveness of the proposed control strategy in the PV-wind-battery-supercapacitor-based dc microgrid.