ISLANDING SCENARIOS FOR HIGH RELIABLE OPERATION OF DISTRIBUTION NETWORKS

Islanding is considered important problem that faces distributed generation. This problem occurs when the protection system takes a correct action to disconnect the fault as a result of that new isolated system is formed. This study introduces a methodology for performing intentional islanding with maximum possible benefits for distribution systems. The methodology is based on an advanced load shedding algorithm to achieve load generation balance and apply a control strategy to ensure a smooth transition from normal mode to island mode with high load power quality. Generally, the load shedding algorithm is applied to improve the reliability by serving maximum number of customers. Investigation of the dynamic behavior of the distribution network during transition due to intentional islanding is a main concern in this thesis. When operating in the island mode, the local supervisory control system can modify the generator frequency controller and voltage controller to guarantee high power quality for the new isolated system. In addition, it is suggested to assess the small signal stability of new islands to evaluate their performance and give priority among different alternatives. Small signal stability study is introduced for each island to check the stability for the new islands. IEEE 33bus system is taken as a case study to ensure the effectiveness of the introduced methodology. The analysis is performed for a case study with optimal DG locations and sizes. NEPLAN software is used for dynamics and small signal stability investigations.