PROJECT TITLE :

Stability Enhancement Based on Virtual Impedance for DC Microgrids With Constant Power Loads

ABSTRACT:

In this paper, a converter-based dc microgrid is studied. By considering the impact of each part in dc microgrids on system stability, a multistage configuration is employed, which includes the supply stage, interface converter stage between buses, and customary load stage. So as to check the overall stability of the above dc microgrid with constant power hundreds (CPLs), a comprehensive little-signal model comes by analyzing the interface converters in every stage. The instability issue induced by the CPLs is revealed by using the standards of impedance matching. Meanwhile, virtual-impedance-primarily based stabilizers are proposed in order to boost the damping of dc microgrids with CPLs and guarantee the stable operation. Since droop management is commonly used to reach proper load power sharing in dc microgrids, its impact is taken into consideration when testing the proposed stabilizers. By using the proposed stabilizers, virtual impedances are used in the output filters of the interface converters in the second stage of the multistage configuration. In particular, one of the virtual impedances is connected in series with the filter capacitor, and the opposite one is connected at the output path of the converter. It can be seen that by using the proposed stabilizers, the unstable poles induced by the CPLs are forced to maneuver into the stable region. The proposed methodology is verified by the MATLAB/Simulink model of multistage dc microgrids with 3 distributed power generation units.