An adjustable gain three port converter for battery and grid integration in remote location microgrid systems

Abstract The battery-grid integration (BGI) is the crux of microgrid systems that not only performs the energy management but also coordinates distributed energy resources and loads. The prevailing BGIs are either individual power converters based, which cause low efficiency and high cost, or multiport converter (MPC) based, which involve a higher component count and/or the lower voltage limit restriction in the DC port. With the increased penetration of distributed energy resources, the demand for MPCs with a wider buck-boost voltage gain capability is unavoidable. They can be used to interface low voltage sources like fuel cells, photovoltaic panels, batteries, etc. To perform the basic functionalities in BGI converters, like the power transfer from the storage to the grid and vice versa at different working conditions, the bidirectional capability in DC and AC ports is mandatory. This paper proposes a high voltage gain, bidirectional buck-boost port based hybrid MPC, called as an energy cushion multiport converter (ECMPC), for the integration of batteries with the single-phase AC microgrid (SPACMG). The ECMPC has three ports, among them one is the bidirectional AC port for the grid, the second one is the bidirectional DC port for the battery, and the last one is a DC output port for the common usage. The modes of operation with an appropriate switching sequence is detailed and a control scheme is also suggested. The performed comprehensive simulation analysis guides the component selection and the design of the converter. The critical comparison of the suggested converter with the prevailing single-phase bidirectional DC-AC converters being employed in the BGI is also presented. The theoretical study is supported by a laboratory corroboration. The system is managed for a minimal energy wastage through anew suggested minimal wastage energy management system (MWEMS). The system in the entirety is implemented and controlled by an ALTERA field-programmable gate array, ALTERA QUARTUS II 12.0SP2 processor.