Modeling and Control of Low-Voltage DC Microgrid With Photovoltaic Energy Resources
The use of DC microgrids is a promising concept that could improve power system reliability and stability in the future. The advantages of microgrids in general include an increase in energy efficiency through lowered energy transmission and operational costs, a reduced carbon footprint through the integration of renewable energy resources, and improvements in power quality and availability to end users through the use of advanced control techniques. DC microgrids have the potential to provide additional advantages, including decreasing interconnection conversion levels of distributed energy resources and energy storage systems, and preventing the propagation of power system disturbances.
Power system research groups around the world are investigating the DC microgrid concept through simulation platforms and experimental setups. Several strategies have been proposed for the control of DC microgrids, including hierarchical, distributed, and intelligent control strategies. In this work, PSCAD/EMTDC simulation environment was used for the modeling and simulation of a DC microgrid. A power management strategy was then implemented in order to ensure voltage regulation and seamless transition between grid-connected and isolated modes. The strategy is based on an autonomous distributed control scheme in which the DC bus voltage level is used as an indicator of the power balance in the microgrid. The autonomous control strategy does not rely on communication links or a central controller, resulting in reduced costs and enhanced reliability. As part of the control strategy, an adaptive droop control technique is proposed for PV sources in order to maximize the utilization of power available from these sources while ensuring acceptable levels of system voltage regulation. These goals are achieved by avoiding the curtailment of renewable energy until violation of the voltage regulation limit occurs. The adaptive droop control then curtails the output power of the PV sources and, at the same time, restores the DC voltage level to within an acceptable tolerance range.