An Inertia and Damping Control Method of DC–DC Converter in DC Microgrids

In DC microgrids, the inherent inertia from DC capacitors is low and the DC bus voltage is susceptible to power fluctuations, which results in low DC voltage quality. In this article, an inertia and damping control (IDC) method is proposed and applied in the energy storage system to strengthen the inertia and damping of DC microgrids. The proposed control strategy is obtained based on the charging and discharging conversion form of capacitors and aims to control the external characteristics of converters in DC microgrids to improve its inertia and damping feature. The small signal model of the proposed control strategy is built to identify the stability and dynamic characteristic. In order to eliminate the abrupt change in the beginning of the voltage dynamic characteristic, a feedforward control is implemented and the dynamic characteristic is revised. Then by analyzing system stability, the range of virtual inertia control coefficient and damping control coefficient are determined. Finally, hardware- in-the-loop (HIL) simulation based on RT-LAB is carried out to verify the validity of the above theoretical analysis and control strategy. In this simulation, the proposed control strategy is implemented in the energy storage system, which provides inertia support to smooth the DC voltage under power fluctuations.