Hybrid Energy Storage System for Voltage Stability in a DC Microgrid Using a Modified Control Strategy

In renewable based DC microgrids, energy storage devices are implemented to compensate for the generation-load power mismatch. Usually, Battery Energy Storage Systems (BESS) are used, but they cannot meet the transient load demand due to low power density leading to voltage fluctuations. For this reason, Supercapacitor Storage Systems (SCSS) are used. In this respect the controller used for regulating the power electronic interface must respond quickly to feed the power from SCSS to the grid. In this paper, a decoupled controller for both BESS and SCSS are designed based on k-type compensators and Lagrange Interpolation (LI) based controllers are designed for BESS and SCSS controllers respectively. As compared to conventional control strategies based on LPF/HPF - PI based controllers, the proposed control strategy possesses a faster response and ensures a reduced voltage fluctuation. Furthermore, the need for converter voltage and current sensing device is reduced and with the obviation of the LPF/HPF filters the complexity and processing time of the converter is reduced.