To address the issues of uneven output current distribution and voltage drop in energy storage unit converters under traditional droop control, an improved scheme is proposed. Firstly, an AC small-signal disturbance is introduced on the basis of traditional droop control to formulate a frequency-current composite droop control strategy, achieving precise proportional current distribution among distributed power converters in DC microgrids. Secondly, the large-signal stability criterion for microgrids under the improved droop control is derived based on mixed potential function theory. Finally, MATLAB/Simulink simulations demonstrate that the proposed frequency droop control strategy effectively achieves accurate current distribution in converters while validating the correctness and effectiveness of the stability criterion. Additionally, the critical range for sudden increases in constant power loads and the feasible domain for voltage controller parameters are determined for specific DC microgrid structural parameters.