A novel small signal model of multi-bus microgrids for modeling interaction of droop controllers through the power network

Microgrid (MG) consists of distributed generation (DG) units, which supply MG loads via the power network. Droop-based control system has been proposed for power sharing implementation among DG units in MGs. The droop control performance is based on the power network variables, which makes it easy to implement. As the control system at the primary level, the droop controller plays a major role in secure operation of MGs in terms of stability concern. However, the lack of high band-width communication links, low X/R ratio of grid impedance and fast response power converters make the droop-based MGs exposed to instability. In this work, a suitable small signal model is developed to assess the droop control system performance and stability. In the proposed model, droop controllers' interaction through the transmission network is modeled appropriately. The proposed model reveals unstable regions which have not been discovered by the conventional parallel-based small signal models.