Oscillatory Current Management for DC Microgrids with High Penetration of Single-Phase AC Loads

This paper presents a comprehensive control scheme for the autonomous operation of a dc microgrid with high penetration of single-phase and unbalanced ac loads. An oscillatory component is introduced into current of dc microgrid through inverter-connected single-phase ac or three-phase unbalanced loads. In such a condition, a conventional droop controller cannot appropriately share the oscillatory components of loads among distributed generation (DG) units. The main merit of this paper is to present an effective control strategy to share the high-frequency current among the power sources of dc microgrid. The DG units are considered as reliable hybrid power conversion system which can meet load demands and support transients. The proposed control system consists of a two control blocks. A multi-loop voltage control unit is employed to regulate the microgrid voltage. Furthermore, a virtual impedance loop is implemented to share dc current and oscillatory components among power sources. The effectiveness of the proposed control scheme is verified by using digital time-domain simulation studies in the PSCAD/EMTDC software environment.