Practical boundary of static voltage stability region in cut-set power space of power systems

A method to approximate the boundaries of static voltage stability region (SVSR) in cut-set power space of electrical power systems is presented. Firstly, a critical cut-set in the sense of voltage stability divides the system into two separate parts, i.e. concentrated weak-node region and non weak-node region. Then with the active and reactive power flow in the branches of a critical cut-set as coordinates, the boundary of SVSR in cut-set power space is obtained by fitting lots of critical points searched by continuous power flow (CPF) with a hyper-plane through the least-square approach. This method not only gives an efficient way to reduce the power system dimensions, but also is convenient for operators to monitor power systems security. The hyper-plane which describes the boundary of SVSR in cut-set power space makes it very useful in analyzing, assessing and optimizing power system security. Examples on various IEEE test systems and EPRI 1000 power system show that this method can approximate the SVSR boundaries with a satisfied accuracy.