Study On Characteristics Of Inter-area Low Frequency Power Oscillation In Interconnected Power Grid

With the interconnecting of large transmission grid, the phenomenon of low frequency oscillation (LFO) happens more and more frequently in China, which constitutes severer threat to system security than transient stability, and it becomes the main obstacle for the the safety and stability of the power grid. Only offline calculation of small disturbance stability can't guarantee the stability, so we hope to analyse the low frequency oscillation on-line so that we can predict its performance and provide appropriate measures when oscillations occur. According to the current research status of on-line analysing LFO , a new method——Regional Mode Analysis(RMA) is proposed. This paper aims at how to realize the RMA , and the main cotent are as follow.Firstly, the article devide our concerning oscillatotry modes into local modes and inter-area modes by using the concept of the participation factor matrix and electroechanical swing loop participation ratio. Then the inter-area modes are classified by setted threshold values. i.e., inter-area mode participated mainly by inter grid generator and inter-area mode participated mainly by external grid generator and inter-area mode participated mainly by both external grid generator and inter grid generator. So it's shown that the classfication of oscillatotry modes in RMA is right.Secondly, the quantitative relation between the mode of tie-line power oscillation and eigenvalues to the equillbrium of overall power grid has been studied. The problems to be solved are which modes dominate the dynamic performance of tie-line power oscillation and what relationship between the mode of tie-line power oscillation and inter-area modes. The article's answer is that the iner-area mode dominates the dynamic performance when the tie-line power oscillate. e.t. the dominated modes of tie-line power oscillation are excited inter-area modes. So it is a feasible method which getting inter-area mode of power system by anlyzing the tie-line power oscillation on line in RMA, and the tie-line power oscillation is obtained by SCADA/WAMS system.Finally, basis of a typical system, we research how the parameters of the equivalent generator affect concerning local modes and inter-area modes and propose a method of adjusting equivalent generator parameters along the criterion which not only maintains the values of concerning modes but also keeps the characteristics of tie-line power oscillation consistent when surffering the same small perturbation in the equivalent system.