Date of Award


Publication Type


Degree Name



Electrical and Computer Engineering


Current limitation, Inverter protecion, Microgrid protection, Optimal protection coordination, Power oscillations elimination, Transformer-less


Maher Azzouz



Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.


Inverter-interfaced distributed generators (IIDGs) face issues related to disruptive power oscillations and overcurrent during unbalanced faults. This thesis focuses on a specific type of IIDGs known as the four-wire IIDG, often referred to as a transformer-less (TL)-IIDG. The TL-IIDG stands out as it possesses the unique capability to completely eliminate power oscillations in both active and reactive power. This is made possible by the addition of a fourth wire, which enhances control capabilities. To address these challenges, a triple current control (TCC) strategy is devised. It leverages sequence currents within a synchronous frame of reference, allowing the creation of a versatile set of reference currents designed to mitigate power oscillations arising from any type of imbalance. Additionally, a fundamental link between power and current magnitude is established. This forms the basis for a current limitation scheme aimed at safeguarding the TL inverter against overcurrent issues. This scheme effectively imposes a limit on current magnitude, causing a corresponding reduction in power magnitude, all while preserving the primary control objectives. Furthermore, the study involves the integration of four TL inverters equipped with the newly developed TCC and current limitation scheme into a 9- bus Canadian grid-connected system. The research concludes with an examination of optimal protection coordination (OPC) for the 9-bus Canadian system, considering various fault scenarios. The objective is to determine the settings for overcurrent relays (OCRs), along with the total operating time. This analysis serves to demonstrate the viability of this control approach within the OPC framework, ensuring that all constraints are upheld.