Virtual Inertia Control Strategy for Improving Damping Performance of DC Microgrid with Negative Feedback Effect

Voltage of DC microgrid is prone to oscillation, originated from the following three factors: 1) negative damping performance of the DC converter; 2) interaction between the power converter and DC network; and 3) positive feedback (PF) of DC voltage control loop. Analogous to the relationship between the force and velocity of motion, it derives the functional relationship between DC current and DC voltage. The motion of DC voltage can be illustrated by the derived vectors since transfer functions between DC current and DC voltage have the corresponding phase and gain at a specific frequency. It is found that it forms a PF when the damping of the DC converter is negative, which can destabilize DC-side voltage at the oscillated frequency. However, a negative feedback can stabilize the system and make the DC voltage attenuated. A virtual inertia (VI) control strategy is proposed for the enhancement of damping performance and forming a negative feedback for the system. The proposed theoretical analysis is demonstrated by Star-Sim hardware-in-the-loop (HIL) experiments.