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This article highlights a voltage instability when the bidirectional interlinking converter (BIC) of a hybrid ac–dc microgrid operates as a constant power load (CPL). The instability is attributed to the impedance interactions seen at the dc port of the BIC. The BIC is operated with two different controllers, viz., a PI controller and a model predictive controller (MPC). In order to avert the instability, prohibiting impedance interactions is proposed as a design objective while determining the bandwidth of the PI controller. However, since a flexible control over bandwidth is not available with MPC, an active damping technique is proposed to address the instability. The proposed technique works equally well for the PI controllers with fixed or predetermined bandwidths. An important feature of the proposed technique is that it does not interfere with the original objectives of the controllers, once the instability is addressed. The technique comprises only one tuning factor, which does not depend on the BIC's internal parameters. As a result, it can easily be implemented as a general stabilizing scheme in any BIC. The efficacy of the proposed technique is verified through simulations, frequency-domain impedance analyses as well as experiments on a laboratory prototype of the BIC. [ABSTRACT FROM AUTHOR]

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 BlC 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 be 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. [ABSTRACT FROM AUTHOR]