Optimal Bus Voltage Regulation in DC Microgrids Using LQI Control and Moving-Horizon Estimation for a Sepic/Zeta Battery Interface

This work deals with the design and implementation of a battery charger/discharger controller based on the Sepic/Zeta topology oriented to the management of energy excess or deficits in a DC microgrid. The system must guarantee the DC bus voltage regulation during battery charging and discharging conditions and to operate correctly under different ratios between bus and battery voltages. To meet these requirements, a Linear-Quadratic-Integral (LQI) control strategy complemented with a Moving Horizon Estimation (MHE) is proposed. The control objective is formulated as an optimal control problem solved using LQR control theory, to which an integrator is added to eliminate the steady-state error. Incorporating MHE allows for an accurate estimate of the states, enhancing the controller performance and robustness to disturbances. In addition, a Feed-Forward control is integrated to increase the dynamic performance against sudden variations in the bus current. The LQI-MHE combination demonstrates efficient energy management under typical dynamic conditions of a DC microgrid, ensuring consistent system performance in the face of fluctuations in both charging and discharging operation. Finally, the results validate the effectiveness of the proposed approach, highlighting its potential in real applications with battery energy storage systems integrated in DC microgrids.