The energy conversion relationship between the capacitor energy storage and the mechanical kinetic energy of the rotating electrical machine during dynamic variations in voltages of DC distribution networks is analyzed. The definition of DC voltage inertia based on the virtual capacitance is clarified

and the control strategy to improve the rotating motor’s voltage inertia in DC distribution networks is proposed. By introducing voltage fluctuation signals

the current control of the synchronous generator-side converter and the power curve coefficient of the variable-speed wind turbine are corrected. The rotor speed of the two kinds of generator and the DC voltage of the distribution network are coupled

so that the two kinds of generator can release or absorb rotational kinetic energy when the system voltage varies and provide inertial support for DC voltages based on energy variation simulation of the charging and discharging of capacitors. A six-terminal DC distribution network simulation system is established

test results on which verify that the proposed control strategy can effectively suppress the DC voltage fluctuations under the unba-lanced power by taking advantage of the voltage inertial provided by synchronous generators and wind turbines

which effectively improves the system transient stability.