Dynamic Control of Region of Attraction Using Variable Inductor for Stabilizing DC Microgrids with Constant Power Loads

DC microgrids with power electronic converter units are prone to become unstable due to the well-known negative impedance characteristic of constant power loads. For such systems, the global stability cannot be assumed. It is known that the transient stability of the system can be degraded by large and fast disturbances due to the reduced stability region. As a result, the system gets to operate outside the stability region and becomes unstable even if the steady-state operating point is in the stable region. To overcome this problem, a dynamic stabilizer that controls the stability region using variable inductor is proposed to guarantee stable operation during transient-states. The proposed scheme is straightforward and can be implemented with minimal power consumption. Furthermore, it is robust for parameter variation. The feasibility of the proposed method is verified experimentally.