Source Management in DC-Microgrids: An Industrial Application

Industrial direct current (DC) microgrids offer multiple advantages for production factories. They enable higher energy and resource efficiency not only for the production energy supply but also for integrating renewable energy resources. The basic control method of DC microgrids, namely droop control, fits the industrial application due to its decentralized and robust nature. However, in the case of droop control, the DC bus voltage deviates from the nominal value for slowly fluctuating load situations. For this reason, an additional control level for voltage restoration, called secondary control or source management, is necessary. This paper presents hierarchical control for voltage restoration in industrial DC microgrids. The control shifts the current supplied to the DC bus in case the load increases over or decreases below a defined voltage band for a certain period. In addition, the designed control is tested on a real industrial DC microgrid which includes typical industrial loads of up to 50 kW, such as robots of different sizes and CNC machine tools. The control performance with different parameters of the source management is assessed. The results show that the designed control restores the voltage level without creating instabilities in the microgrid for all tested scenarios.