Distributed Predictive Virtual Capacitance Control for Accurate Reactive Power Sharing in Islanded Microgrids

Abstract

Distributed renewable energy generation is one of the notable features of the emerging smart grid. These distributed generators (DGs), which require power electronic converter interfaces, are modularly connected to microgrids–which are the "building blocks" of the smart grid. However, one recurring challenge with AC microgrids is inaccurate reactive power sharing among voltage source converters (VSCs) that make up the DGs. This happens whenever the impedances of feeder lines that connect the different DGs to the microgrid bus are unequal. The state-of-the-art methods to these problems have two limitations: 1) loss of voltage regulation as equal/proportional reactive power sharing is achieved, and 2) use of high-bandwidth communication for wide-area applications. Therefore, in this paper, we address these problems as follows: first we introduce a novel predictive virtual capacitance control scheme that can both achieve more accurate reactive power sharing and also improve voltage regulation in VSCs, and second we achieve reactive power sharing among multiple VSCs with an improved consensus-based distributed control; this requires low-bandwidth is robust to communication interference, and provides plug-and-play capability. The effectiveness of these new methods are verified experimentally with PLECS RT-Box hardware-in-the-loop equipment on a microgrid system with four connected VSCs.