A Stability Enhancement Method Based on Adaptive Virtual Resistor for Electric-hydrogen Hybrid DC Microgrid Grid-connected Inverter Under Weak Grid

For the impedance mismatch of a grid-connected inverter connected to a weak grid, impedance analysis and Nyquist criterion reveal that the positive resistance can effectively improve the stability. A traditional virtual resistor (TVR) indeed increases the output resistance of the system, but it is difficult to adapt to a wide range of grid impedance changes, which extends transient response time. To address this issue and apply the research on the weak grid to an actual DC microgrid (MG), this paper proposes a stability enhancement method based on adaptive virtual resistor (AVR) for an electric-hydrogen hybrid DC MG grid-connected inverter under weak grid, which will be added as an independent control module to the grid-connected inverter. Composed of a TVR and dynamic resistor, AVR can enhance the resistance of the system and dynamically follow the grid impedance change, thereby improving the stability and adaptability of the grid-connected inverter under impedance variation. An electric-hydrogen hybrid DC MG simulation platform is established based on RT-LAB real-time simulator. Through comparative experiments of multiple setting scenarios, the effectiveness of the proposed AVR-based stability enhancement method was verified, and the stability of the DC bus voltage and power distribution under different operating scenarios were successfully realized.

Automated summary

This paper proposes a stability enhancement method based on adaptive virtual resistor for addressing impedance mismatch issues in a grid-connected inverter connected to a weak grid. Through experimental verification, the effectiveness of the proposed method in improving the stability of DC bus voltage and power distribution under different operating scenarios was successfully demonstrated.