A Battery-Energy-Storage-Based DC Dynamic Voltage Restorer for DC Renewable Power Protection

The limitation of theDC protection device confines the development of MV/LVDC grids. This paper presents a DC dynamic voltage restorer to exploit DC custom power devices for DC distribution networks in principle. It is based on an improved AC/DC dual active bridge and battery energy storage to maintain the voltage profile of sensitive loads in DC networks. The principle of the improved DC-DVR has been analyzed from the perspectives of the range of compensated voltage, current characteristics, and control strategy. Compared with other existing methods, the proposed DC-DVR features a simple structure, an easy control strategy, and the ability to mitigate both voltage sag and swell by injecting forward or reverse voltage. Experiment results demonstrate the correctness of the theoretical analysis and the feasibility of the proposed structure. A case study of DC doubly-fed induction generator (DFIG) interfaced with power grid is carried out, integrated with the proposed DC-DVR to verify the operation principle of the proposed scheme.