Enhanced Grid Frequency and DC-Link Voltage Regulation in Hybrid AC/DC Microgrids Through Bidirectional Virtual Inertia Support

AC mains frequency and dc-link voltage are two of the most important parameters that determine the stability of hybrid ac/dc microgrids. Frequency and voltage deviations beyond the acceptable threshold can lead to unscheduled load curtailments, cascading failures, or even power system blackouts. To enhance the stability of hybrid ac/dc microgrids, this article proposes a hybrid microgrid with bidirectional virtual inertia support, where virtual inertia is introduced to slow down dc voltage and ac frequency changes, thus enhancing the system stability. The proposed approach allows significant reductions in voltage and frequency fluctuations. With a standard hybrid microgrid configuration, inertia is delivered to both ac and dc subgrids via the change of bidirectional interlinking converter control. Specifically, the bidirectional interlinking converter uses the dc voltage of the dc grid and ac frequency of the ac grid as inputs through a proportional-integral (PI) controller and regulates the active power between two subgrids so that inertia and other supportive functions are implemented. To validate the merits of the proposed approach, experimental results are provided. According to experimental results, the frequency nadir, rate-of-change-of-frequency, and dc bus voltage deviation can be improved by the proposed strategy of bidirectional virtual inertia support in the hybrid ac/dc microgrid.