To solve the problem of DC microgrid instability caused by constant power load, a voltage stability control strategy based on a virtual DC machine (VDCM) is proposed. Taking the bidirectional DC/DC converter of energy storage as the research object, and based on the principle of a DC machine, the control strategy introduces a VDCM link on the basis of traditional droop control with the inductance current as the feedback quantity to increase the system damping and reduce the influence of constant power load on system stability. By establishing the small signal model of the DC microgrid with the proposed control strategy, the stability of the system when relevant parameters change is analyzed with the principle of impedance matching. Then the proposed control strategy is compared with the traditional VDCM control strategy. Finally, the simulation model and hardware experimental platform are built to verify the effectiveness of the proposed control strategy. The results show that the strategy makes the converter have the inertia and damping characteristics of a DC machine. This not only improves the stability of the system, but also improves the dynamic response performance to a certain extent. Its control effect is better than that the traditional VDCM control strategy.

This work is supported by the National Natural Science Foundation of China (No. 51977074).