Grid Forming Inverters for Microgrid Operation Enhancement

Modern electric power systems are confronted with several major challenges including the increasing frequency and severity of weather events, aging infrastructure, high material costs, cyber-attacks, and substantial delays in global supply chains. Microgrids provide a solution to these challenges by insulating customers from the power outages occurring in their local distribution system. A microgrid is a small independent power system with its own power generation and energy storage resources that can supply customers’ electricity needs. When an outage occurs, a circuit breaker will disconnect the microgrid from the distribution system. Successful operation of the microgrid requires one or more devices to provide a continuous stable voltage, which would normally be provided by the distribution system; these are known as grid-forming devices. This dissertation describes how direct current to alternating current inverters can be used as these grid-forming devices in microgrids. Investigation of several use cases demonstrated the unique characteristics of inverters that improve the operation of microgrids as compared to more conventional grid forming devices (e.g., back-up diesel generators). In spite of these benefits, inverters are more vulnerable to damage from temporary overcurrent and overload conditions, degrading the resilience of microgrids that rely upon inverters to be the grid-forming devices. This dissertation presents a solution that allows inverters to act as grid-forming devices while preventing temporary overcurrents and overloads. This solution enables the benefits of grid-forming inverters to be realized without compromising microgrid resilience.