Fuzzy logic and state machine control-based hybrid energy management system of power sharing with smart mode-transition for DC microgrid

• A hybrid energy management system integrating fuzzy logic and state machine control is developed for DC microgrid applications. • Lead-acid batteries, lithium-ion batteries, and supercapacitors are coordinated to achieve optimal power sharing among the heterogeneous storage elements. • An adaptive switching mechanism is introduced, enabling seamless and intelligent transitions between control strategies. • The proposed approach enhances DC bus voltage stability, particularly under rapidly fluctuating and variable load conditions. • The control strategy mitigates dynamic stress on the batteries, thereby improving the operational lifetime and reliability of the overall energy storage system. Direct Current Microgrids (DCMGs) are an attractive solution to address increasing needs for effective energy management leading to enhance system reliability, improve operational efficiency, and extend the lifespan of the DC energy sources. They effectively balance energy production and consumption either in connection with the main utility grid or functioning independently in islanded mode. Recent DCMG studies have emphasized fuel-cell operation while giving limited attention to battery performance. Moreover, the Energy Management Strategy (EMS) typically produces abrupt control actions, and the absence of supercapacitors (SC) in the Hybrid Energy Storage System (HESS) exacerbates system oscillations and weakens overall stability. A hybrid energy management system combining fuzzy logic and state machine control is developed for DC microgrids. Lead acid, lithium ion batteries and supercapacitor are used and coordinated for optimal power sharing. A smart transition mechanism is introduced enabling adaptive and seamless controller switching. DC bus voltage (DCBV) stability is enhanced under rapid and variable load conditions. Battery dynamic stress is reduced and overall storage system lifetime and reliability are improved. The HESS equipped with the proposed energy management system exhibits reduced DCBV deviations (2.2%) with improved time response 5 seconds, which in turn mitigates the power shortage in the DCMG load demand (6% instead of 10%). This enhanced performance, together with improved power-sharing capabilities, contributes to an extension of the battery lifetime. This integrated approach not only improves the overall performance and reliability of the DCMG but also plays a vital role in prolonging the service life of the HESS used in the system.