NEW TECHNIQUE OF NETWORK PARTITIONING FOR VOLTAGE COLLAPSE MARGIN CALCULATIONS

Voltage collapse is associated with a stress condition of power system s. Control actions must provide the desired results, otherwise a syste m may operate in an unknown condition. It has been shown that this unk nown condition is associated with two regions of operation and the bou ndary between them. The boundary between the two regions is related to a singular load-flow Jacobian. To identify the critical bus, a reduct ion of the load-flow Jacobian in relation to each load bus is develope d. To reduce the computational burden associated with large power netw orks, a network partitioning is proposed which is based on voltage var iation at each load bus in relation to load variation at the other loa d busses. Comparison between the proposed method and network partition ing using Sanchis' method is presented. The weak area of a power syste m is identified in the network partitioning; a weak area is defined as the area that contains the critical bus of the power network. To calc ulate the margins for each load bus of the weak area, the relation bet ween load variation at each load bus and voltage magnitude and phase a ngle variations at the critical bus is normalised, one by one. The bus ses strongly connected to the critical bus have smaller load variation in relation to the busses weakly connected to the critical bus. The p roposed method has been tested using the IEEE 24-bus and 300-bus syste ms.