Bidirectional power management in hybrid AC-DC islanded microgrid system

Abstract

This paper addresses the interconnection of two ac and dc subgrids via a voltage source converter (VSC) to facilitate a bidirectional power exchange and increase the system reliability. The control of the interfacing VSC is achieved by two schemes; autonomous and communication-based. The autonomous control might fail to operate in a large scale islanded hybrid system due to the variations in the generation characteristics of the individual distributed generation (DG) units (such as droop coefficients or set points variations, loss/connection of units, etc.). A centralized power management controller is therefore proposed to achieve an accurate, efficient and minimized power exchange. The proposed method can be generalized to large scale hybrid systems. Small signal stability analysis has been conducted to investigate the influence of the communication delays on the system stability. Time domain simulations are presented to show the effectiveness of the proposed technique.