Energy management system for LVDC island networks

Abstract

Environmental concerns have led to increased penetration of renewable energy sources into the power grid. Many researches have considered localized and small-scale renewable energy sources supplying microgrids-small-scale localized distribution networks-as a backup to the main grid. Further, the aging of traditional transmission networks has led some researchers to propose islanded operations of the microgrid; the grid is isolated from the main grid and operates independently. However, islanded operations face many challenges such as power quality, voltage regulation, network stability, and protection. Moreover, renewable energy sources are unreliable and intermittent. Recent developments in power electronics have made it possible to develop competitive and reliable low-voltage DC (LVDC) distribution networks. Further, advances in information and communications technology (ICT) have led to smart grids in which various devices in the network can communicate with each other and/or a control center. In this paper, we consider an islanded LVDC smart microgrid that uses renewable energy sources. An energy management system (EMS) that ensures efficient energy and power balancing and voltage regulation is proposed for the network. The DC network utilizes solar panels for electricity production and lead-acid batteries as energy storage to support the production. The EMS uses the master/slave method with robust communication infrastructure to control the production, storage, and loads. The logical basis for the EMS operations has been established by proposing functionalities for the network components and defining operation modes that encompass all situations. During loss-of-power-supply periods, load prioritizations and disconnections are used to maintain power supply to at least some loads. The successful performance of the proposed EMS to maintain energy balance in the network has been demonstrated by simulations.