State-Space Variation Induced Instability During Mode Switching in Multi-Source DC Microgrid

DC bus signaling strategy is a common solution for achieving multi-mode autonomous operation in multi-source DC microgrids. This strategy often results in two different types of mode switching, which are classified based on whether state-space variation occurs before and after the switch. This paper investigates the voltage instability caused by state-space variation during mode switching of multi-source DC microgrid. Firstly, this paper analyzes how the dynamic behavior of the mode switching influences system stability and provides a state-space switching stability analysis method. The switching process may cause the system state to deviate from the region of attraction (ROA), thereby triggering system instability. Additionally, the mechanism of state-space variation induced instability during mode switching is revealed: mode switching involves mutual coupling among the adjustment processes of different source control strategies. This coupling exacerbates power imbalance, ultimately leading to system instability. To improve stability, an extended mode scheduling control method has been proposed by introducing transition modes to address the power imbalances during the mode switching. Finally, the experimental results verify the analytical mechanism and control method.