Proposed frequency decoupling-based fuzzy logic control for power allocation and state-of-charge recovery of hybrid energy storage systems adopting multi-level energy management for multi-DC-microgrids

This paper proposes a decentralized multiple-Direct-Current-Microgrid (multi-DCMG) system to supply affordable load demands while addressing challenges posed by Hybridized-Energy-Storage-Systems (H-ESS) limitations, consumption/generation complexities, and renewables volatility. The paper's contributions include a system feasibility assessment for isolated users and a demonstration of the effectiveness of the control strategies adopted. To improve system resiliency and reliability, the proposed system adopts a high-control level for energy/power balances, using a Mamdani 50 rule-based Fuzzy Logic energy management system (FL-EMS) to supervise State-of-Charge (SoC) recovery. The low-control level manages/supervises DC-DC power converters' powers adopting Proportional-Integral (PI), Hysteresis-Current-Controller (HCC), and Linear-QuadraticRegulator (LQR) in closed-Control-loops, besides an advanced low-pass-filtering (A-LPF) for load frequency decoupling. The results show that the proposed H-ESS outperformed single-ESS systems in dynamic load changes and renewables' uncertainty, and supercapacitors improved load supply, voltage regulation, and current tracking. However, expensive costs and slow restoration of H-ESS banks from critical SoCs are major drawbacks. The global system assessment demonstrated promising results through proper FL-EMS setpoint computation, stable Bus voltage with 0.55-6.9% deviations due to robust controllers, accurate SoC recovery of HESS batteries at critical SoCs (<10% and >90%), fast and accurate convergence with 3.35-3.37% mismatch, and 99.3% supply efficiency at minor power losses of 0.7-1.55%.

Automated summary

This paper presents a decentralized multi-DCMG system to address the challenges of H-ESS limitations, consumption/generation complexities, and renewables volatility, while providing affordable load demands. The proposed system utilizes a high-control level for energy/power balances and a fuzzy logic energy management system to supervise SoC recovery. The low-control level consists of robust controllers and advanced filtering techniques for load frequency decoupling. The results show that the H-ESS outperforms single-ESS systems in dynamic load changes and renewables' uncertainty, but high costs and slow SoC restoration are major drawbacks. The global system assessment demonstrates promising results in terms of stable Bus voltage, accurate SoC recovery, and high supply efficiency with minor power losses.