A Generalized Droop Strategy for Interlinking Converter in a Standalone Hybrid Microgrid.

The existence of ac and dc grid leads to a new concept of hybrid microgrid in which both grids are tied by an interlinking converter (ILC). Various control schemes of ILC have been discussed in literature but there is a lack of a generalized, autonomous control which considers the tie line capacity between ac and dc grids. In addition, the majority of schemes involve switching between control modes which increases power losses. To address these issues, this paper presents a generalized droop scheme of ILC for power sharing and control in a standalone hybrid ac/dc microgrid. A 3-dimensional plane is proposed where the axis correspond to dc voltage, ac frequency and converter power. The converter utilizes frequency droop at ac terminal and voltage droop at dc terminal so any change in voltage or frequency results in active power flow from an underloaded to overloaded grid. A corresponding mathematical model is also presented which determines the impact of load change on frequency and dc voltage. The proposed scheme enables autonomous power transfer in both directions without any form of communication. A comparison between the traditional normalization scheme and proposed scheme is also presented where it is observed that this method reduces the frequency deviations and transient response time, thereby giving a better performance. Both the simulations and experimental results confirm the validity of the proposed model. [ABSTRACT FROM AUTHOR]