Decentralized Adaptive Control to Enhance Flexibility and Stability in Islanded DC Microgrid with Constant Power Loads

This paper proposes an adaptive decentralized control scheme for coordinated energy management in DC micro grids (DC-MGs) with multiple renewable sources, energy storage systems, and loads. The method addresses the intermittency of renewables and uncertainties in demand by employing electric spring technology as a smart backup unit. This technology enhances grid flexibility by controlling both the energy stored in batteries and the power dissipated by loads, when renew able sources–operating under Maximum Power Point Tracking (MPPT)–do not properly match load requirements. A decentralized adaptive droop-based controller is developed to balance bus voltage regulation with accurate current/power sharing. The controller adjusts droop gains based solely on local measurements to enhance performance while maintaining stable operating margins even in the presence of constant power loads, whose negative incremental impedance can compromise system stability. The stability margin is evaluated under systematic variation of DC-MG's elements, such as constant power loads, via small signal sensitivity analysis. Battery characteristics are integrated into the energy-sharing mechanism to maintain SoC balance and prolong battery lifetime. Considering all operating modes, the DC bus voltage facilitates seamless mode transitions and autonomous operation within the off-grid system. The effectiveness of the proposed method has been evaluated using MATLAB/Simulink software.