Minimum Load Shedding Calculation Based on Static Voltage Security Region in Load Injection Space

It is meaningful to get a clear cognition on the geometric shape of the system's static voltage security region (SVSR) when doing voltage stability assessment or preventive/corrective control. Sometimes the boundary of SVSR is too complex to be represented by only one hyper-plane. In this paper, an innovative method based on clustering theory is used to fit the boundary of SVSR in load injection space. Firstly, critical points of voltage collapse are calculated, whose local tangent plane's normal vectors can also be derived in the load injection space. Secondly, critical points are classified according to the similarity of normal vectors by using Fuzzy C-Means (FCM) clustering methods. Then, the boundary of SVSR is divided into couples of plane which are fitted by critical points in the same class. Base on the more accurate description of SVSR in load injection space, minimum load-shedding calculation can be done very fast with satisfied precision. Visualization of this method on an IEEE6-bus system gives a clear demonstration and the test results validate the correctness of the presented method.