Development of a Self-Healing strategy for future smart microgrids

Microgrid is expected to supply its local loads independently. But, due to intermittency of wind and solar-based energy resources as well as the load uncertainty, it is probable that a microgrid experiences power deficiency. This problem can be mitigated by coupling the overloaded microgrid to another neighbouring microgrid that has surplus power. Considering a distribution network composed of several islanded microgrids, defining the suitable microgrids to be coupled to the overloaded microgrid is a challenge. A microgrid overload management technique is developed in this thesis which first identifies the overloaded microgrid(s) and then selects the most suitable neighbouring microgrids. The alternative selection is based on different criteria such as available surplus power, reliability, supply security, power loss, electricity cost and emissions in the selected microgrids. Moreover, the frequency and voltage deviation in the system of coupled microgrids are considered in the selection. In addition, the thesis evaluates the impact of the weightings of each criterion on the outcome of the alternative selection strategy and presents the sensitivity of the selection procedure on the weightings of each criterion since each criterion weighting has the potential to vary the outcome of the alternative selection therefore the impact of every criteria is found to be crucial. Therefore, a dynamic multi-criteria decision-making algorithm is developed for this purpose. To contemplate the uncertainties in the considered distribution network, a cloud theory-based probabilistic analysis is deployed as the research framework and the performance of the developed technique is evaluated in MATLAB. Once a selection is identified, the interconnection should take place, but before that, a synchronisation between selected microgrids is required for a safe and appropriate interconnection between them and thereby in this thesis, the transition stage forming a system of coupled microgrids is also discussed, and a suitable and practically applicable strategy is developed which facilitates their synchronisation before interconnection. The performance of the developed strategy is evaluated by time-domain simulation studies in PSCAD/EMTDC