Date of Award

December 2020

Document Type


Degree Name

Master of Science (MS)


Electrical Engineering

Committee Member

Sukumat Brahma

Committee Member

Johan Enslin

Committee Member

Ramtin Hadidi


The integration of renewable and distributed energy resources to the electric power system is expected to increase, especially at the distribution level. As more renewable generation connects to distribution systems, it is imminent that existing distribution feeders will be converted to microgrids. Microgrids are systems, typically at distribution voltage level, sustained by distributed and often renewable sources, that can operate in grid-connected and islanded modes. Microgrids offer resilience by providing the flexibility of supporting the grid in normal operation and operating as self-sustained islands when the grid is disconnected.

As the grid transforms to a modular system consisting of many microgrids, these microgrids will likely evolve from existing distribution feeders, and hence will be unbalanced in nature. As the world moves towards cleaner and renewable generation, some of these microgrids may be supplied by 100% inverter-based resources (IBRs). To increase resiliency and reliability, these microgrids will need to operate in both grid-connected and islanded modes. However, inverter control and feeder protection will need to be tuned to the operating modes of the microgrid. Protection system design for microgrids pose significant challenges due to bi-directional power flow and fault currents, lower fault current due to the inverter-based resources, and wide range of fault currents during different modes of operation.

This work offers an insight into the issues involved, by taking a case study of a real-world feeder located in the southwestern US that was converted to a microgrid with three solar PV units connecting to the feeder. Different inverter control configurations and adaptive protection using different settings for different operating conditions are proposed for safe operation of this microgrid. The solution also helps to create a framework for protection and coordination of other similar microgrids.



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