New technique of network partitioning for voltage collapse margin calculations

Voltage collapse is associated with a stress condition of power systems. Control actions must provide the desired results, otherwise a system may operate in an unknown condition. It has been shown that this unknown condition is associated with two regions of operation and the boundary between them. The boundary between the two regions is related to a singular load-flow Jacobian. To identify the critical bus, a reduction of the load-flow Jacobian in relation to each load bus is developed. To reduce the computational burden associated with large power networks, a network partitioning is proposed which is based on voltage variation at each load bus in relation to load variation at the other load busses. Comparison between the proposed method and network partitioning using Sanchis´ method is presented. The weak area of a power system is identified in the network partitioning; a weak area is defined as the area that contains the critical bus of the power network. To calculate the margins for each load bus of the weak area, the relation between load variation at each load bus and voltage magnitude and phase angle variations at the critical bus is normalised, one by one. The busses strongly connected to the critical bus have smaller load variation in relation to the busses weakly connected to the critical bus. The proposed method has been tested using the IEEE 24-bus and 300-bus systems