Determination of coherent clusters in a multi-machine power system based on wide-area signal measurements

This paper illustrates a new technique that identifies coherent clusters of synchronous generators in multi-machine power systems. The technique can be easily implemented in a wide-area measurement system. The importance of fast identification of coherent groups of generators based on wide-area signal measurements lies in its contribution to the design of wide-area based stability control schemes that aim to enhance the overall performance of the power system. The method uses a hierarchical clustering technique (Agglomerative Method) to classify any number of synchronous generators into a number of coherent groups. A new technique is proposed to take into account the influence of the type of events on the clustering. The clustering is based on coherency measures obtained from the time domain responses of the generators following system disturbances. These measures are used to evaluate the degree of coherency between any pair of generators. Thereafter, the clustering algorithm is used to cluster these coherent generators into coherent groups. It is suggested that generators´ rotor measurements can be obtained and therefore synchronised measurements of these quantities using Phasor Measurement Units (PMUs) technology can be acquired. Hence, the proposed clustering method could be integrated into a wide-area measurement system that enables fast identification of coherent clusters of generators. The proposed method is tested on the standard 16 generator 68 bus system.