In islanded mode microgrid

the distributed generation（DG） units are operated in the parallel way. In the unequal line impedance condition

the traditional droop control is unable to proportionally share the reactive load. To solve this issue

we proposed an improved droop control strategy based on the line impedance estimator to eliminate the sharing error. Firstly

the relation between the droop control and line impedance was analyzed; secondly

the line impedance estimator of single unit based on the local measurement was built to identify the line impedance with high accuracy. In addition

a voltage compensation term related to the identification result was added to ensure proportional sharing in non-trival impedance condition. Finally

the proposed scheme was applied to a microgrid in MATLAB/Simulink software environment.The simulation results demonstrate the proposed active observer for line impedance is able to identify the line impedance accurately. Based on the estimation result of line impedance

it is able to compensate unmatched voltage drop accurately and make reactive power to share by a reasonable way. The proposed method does not need transmission system to transfer message of DGs

and does not meet the central controller to send synchronizing signal to make sure the synchronism of improved control. The research results prove that the proposed improved droop control strategy is effective.