A Brief Review on Partially Isolated Bidirectional Multiport Converters For Renewable Energy Sourced DC Microgrids

Abstract

The increasing energy demand and the growing concern over the environmental effects of conventional sources augmented the integration of renewable energy sources as distributed generation units to the power grid. But integrating the renewable energy sources into the existing aged utility AC grids can introduce new difficulties such as an increase in voltage, synchronization, and protection issues. DC microgrids are becoming a solution to these problems by providing a reliable interface for connecting the renewable energy sources, storage, and the grid. Static power converters are required for matching the voltage levels of renewable energy sources and storages with that of the grid.  Recently, multiport power electronic converters are gaining importance because of their compact size, centralized control and simple power flow management techniques. In renewable energy sourced micro-grid, it is required to have a battery back-up to overcome the on-off nature of renewable energy sources. Also to meet the safety requirements, it is required to have an isolated bidirectional power transfer between the energy sources, battery and load. In such a case, a multiport converter with bi-directional power flow capability with necessary isolation is required to connect various renewable energy sources with load and battery facilities. Among the different categories of multiport converters, partially isolated multiport converters combine the advantages of isolated and non-isolated circuits by providing required isolation while improving the power density by maintaining compact circuit size. In this paper, a brief overview of partially isolated multiport dc-dc converter topologies for harvesting renewable energy in DC microgrids is presented.