A DC distribution network using voltage droop control strategy has good stability

but the ability to adjust the high frequency random power fluctuations is poor. Being suitable for the voltage droop control of DC distribution network

a virtual inertia control method is studied to accommodate the rapidity and stability of the regulator

and to improve the quality of the DC voltage. The control strategy can compensate for the system power shortage by the rapid adjustment of battery's charging and discharging rate

which is caused by the change in the battery's droop coefficient. Thus this control strategy can provide a virtual capacitance much larger than the actual capacitance at the DC side and improve the system inertia. At the same time

the theoretical analysis of the specific virtual inertia margin under different operating conditions is provided

so that the control strategy can adjust the droop coefficient on the basis of the allowed swing range adaptively

allowing the battery to provide variable inertia support in accordance with its virtual inertia margin. This ensures the full and rational use of the inertia margin. In order to verify the effectiveness of the proposed control strategy

a four-terminal wind-battery-based DC distribution network is established in MATLAB/Simulink. The results show that the proposed control strategy is able to improve the system's transient response

improve the quality of DC bus voltage

and smooth the power fluctuation between the AC grid and DC grid. This work is supported by National High Technology Research and Development Program of China(863 Program)(No. 2015AA050101).