Design and implementation of an energy-management system for a grid-connected residential DC microgrid

Abstract

The design and implementation of an energy-management system (EMS) applied to a residential direct current microgrid (DC-μG) is presented in this work. The proposed residential DC-μG is designed to provide a maximum power of one kilowatt by using two photovoltaic arrays (PAs) of 500 W, a battery bank (BB) of 120 V-115 Ah, a supercapacitor module of 0.230 F and a bidirectional DC-AC converter linked to the AC main grid (MG). The EMS works as a centralized manager and it defines the working operation mode for each section of the DC-μG. The operation modes are based on: (1) the DC-link bus voltage, (2) the generated or demanded power to each section of the DC-μG and (3) the BB's state of charge. The proposed EMS-during the several working operation modes and at the same time-can obtain the maximum energy from the PAs, reduce the energy consumption from the main grid and keep the DC-link bus voltage inside a range of 190 V ± 5%. The EMS and local controllers are implemented by using LabVIEW and NI myRIO-1900 platforms. Moreover, experimental results during connection and disconnection of each DC-μG sections and different on-the-fly transitions are reported, these results focus on the behavior of the DC bus, which shows the DC bus robustness and stability. The robustness of the DC-μG is demonstrated by maintaining a balance of energy between the sources and loads connected to the DC bus under different scenarios.