A Novel Control Scheme for Enhancing the Transient Performance of an Islanded Hybrid AC-DC Microgrid

This paper proposes a novel ancillary feature in bidirectional interlinking converter (BIC) for enhancing the transient performance of an islanded hybrid ac-dc microgrid. The system under consideration includes an ac microgrid with a mix of inertial and non-inertial sources integrated with a dc microgrid through a BIC. The existing BIC control schemes do not judiciously utilize the inertial sources [like the synchronous generator (SG)] as short-term storage for enhancing the transient performance of the system. Since both the microgrids are interfaced through a BIC, this can he achieved by adaptively varying its output frequency during disturbance in the ac microgrid. In the proposed scheme, the BIC is operated as a virtual synchronous generator (VSG) and its output frequency is deliberately increased/decreased during the disturbance. The change in BIC output frequency results in circulating current between the BIC and the SG. Since the BIC voltage phasor leads/lags the SG voltage phasor, it results in the utilization of the inertia of SG as storage. It provides a cost-effective solution by reducing the dependence of the scheme on storage, thereby minimizing the storage requirement while maintaining the transient stability of the system. The proposed control strategy is validated through simulations and experiments.