Voltage and Current Controllability in Multi-Microgrid Smart Distribution Systems

Microgrids with distributed energy resources are becoming inevitable parts of modern distribution systems. With the advancements in power-electronics-based converters, such resources will have the potential to effectively resolve voltage/current control issues in multi-microgrid distribution systems. In this paper, a probabilistic index is defined to measure the controllability of voltages and currents in the buses and lines of single- and multi-microgrid distribution systems. Then, a multi-microgrid system is assessed in terms of voltage and current controllability and it is shown that the controllability can be improved by redesigning the microgrids. For this purpose, a novel comprehensive index is defined for optimally clustering active distribution systems into a multi-microgrid system with optimized reliability, supply-security and controllability. The well-known PG&E 69-bus distribution system is selected as a study system. Through several sensitivity studies, the robustness of the design and the effects of interconnecting different distributed reactive sources and distributed energy storage resources capacities on the designed system are investigated.