Abstract: DC microgrid usually consists of a plurality of power electronic converters with feedback control

connected to a common DC bus. Although the control loop design of each individual converter has a good stability

margin，the interconnection of multiple power and load converters can cause stability and performance problems due to potential interactions. Therefore，in order to ensure the dynamic performance of the interconnected power converter system，a method worth studying is to monitor the on-line stability of the DC bus and dampen the impedance of the DC bus properly. Firstly，the expression of DC bus impedance was derived from the voltage or droop loop gain of source-side converter. Secondly，the estimation of busbar impedance peak was given based on the dynamic behavior index of the system with phase margin. Then，it was proposed that the peak impedance of the bus can be monitored continuously by injecting a sinusoidal signal into the voltage（or drooping）loop. Then，the monitored values can be used to automatically adjust the voltage regulator to keep the bus impedance in a known allowable impedance region.Finally，the effectiveness and superiority of the proposed method were verified by simulation and experiment.

      Key words: DC microgrid ；power converter ；stability ；estimation ；bus impedance