Power system clustering islanding method considering bus voltage controllability

Even if the constraint of generators' coherency and active power balance has been satisfied in the traditional controlled islanding analysis methods, the power flow of the islands could be unacceptable due to the lack of the reactive power support. It is largely results from the inappropriate structure of the islands. Inappropriate structure of the islands causes the abnormal bus voltage, and it even results in the unconvergence of power flow. In order to solve the problem, a controlled islanding analysis method is proposed. The idea of this method is using the bus voltage controllability constraint to adjust the islands' surface. The basic theory of the method is one kind of highly efficient clustering islanding method. The bus voltage controllability constraint is composed by the constraint from the VQ sensitivity between buses and reactive power capacity of power sources. Firstly, the electrical sensitivity between the buses is expressed as a distance, and reactive power source capacity is expressed as a supporting range; Secondly, these two influence factors are obviously displayed and reflected by the corresponding change of the buses' distance; Thirdly, in accordance with the active power supporting relationship between the buses, the corresponding distance are adjusted for expressing the relationship in an orthogonal way; Lastly, after integrate the relationship distance of active power balance and the voltage controllability, the improved islanding scheme can be obtain by the basic clustering islanding method. In addition, in the research, a new electrical distance expression which combines the active power balance and the voltage controllability is proposed; At the last step of the method, an improved K-Medoids clustering algorithm is used to obtain the controlled islanding scheme. Case studies and results comparisons show the effectiveness of the proposed method. The voltage level of islands becomes better after the access of supporting relationship between the reactive power source and the bus voltage.