An Improved Virtual DC Machine Control for Inertia Enhancement in DC Microgrid

Virtual DC Machine (VDCM) control is a promising approach for providing inertia support in DC microgrids, thus enhancing voltage stability. However, it suffers from a complex model and difficult parameter tuning. For this issue, an improved VDCM (IVDCM) control strategy is proposed, offering several advantages over the conventional VDCM (CVDCM) control. Specifically, compared to CVDCM, the voltage recovery control in IVDCM is moved after the VDCM loop, and a capacitor current feedback is adopted in the current inner loop. The improved control structure enables the IVDCM to provide more inertial power and mitigate the DC bus voltage fluctuations. Furthermore, the small-signal output impedance of the IVDCM can be simplified into a second-order model. The time-domain expressions for the DC output voltage are then derived, and the dynamic performance indices and constraints of the IVDCM are established, defining the feasible region for IVDCM control parameters. Consequently, an intuitive approach for control parameter design is achievable. Simulation and experimental results demonstrate the effectiveness of the proposed IVDCM control strategy and the associated parameter design method.