A Hybrid Controller Assisted Voltage Regulation and Power Splitting Strategy for Battery/Supercapacitor System in Isolated DC Microgrid

The hybrid energy storage system (HESS) on a direct current (DC) microgrid aims to ensure rapid and accurate dc bus voltage control. However, the conventional control approaches are challenging to implement with minimal setting time and overshoot, which can cause significant variations in dc bus voltage. The PI controllers used in traditional techniques add an extra lag to the control loop and increase the difficulty of parameter tuning. Additionally, using a power splitting scheme based on a traditional first-order low-pass filter (LPF) delays the control loop and slows down system dynamics. To address this issue, a hybrid control strategy that employs a proportional-integral controller for dc bus voltage control and a simple prediction control for duty calculation is proposed in this work. An improved power splitting scheme is incorporated for HESS, which reduces the effect of LPF on the battery current reference calculation and enhances the dynamics of the dc microgrid. Furthermore, a voltage regulation loop is added to guarantee the charging of the SC without affecting the dc microgrid operation. The proposed method is validated through detailed simulation and experimental studies that show improved dc bus voltage control and HESS power-sharing.