Research On Disturbance Source Locating Of Low Frequency Oscillation In Power Systems

The first task is to judge the position of disturbance source quickly and accurately when the low frequency oscillation caused by local disturbance source occurs in the power system. The technology of disturbance source location contains two major issues,one is the accuracy and applicability of the theoretical criterion, and the other is the effectiveness of searching strategy. The research results in the domestic and foreign related fields are reviewed and analyzed in this paper firstly. Not only the types and mechanisms of low frequency oscillation but also the advantages and disadvantages of existing disturbance source location method are introduced. On this basis, the two issues above are studied deeply, and a set of methods is put forward for disturbance source location in this paper.The reasons why the steady points of low frequency oscillation may be time-varying are analyzed firstly, then the energy function of a specific construction form is decomposed into state energy, reciprocation energy and dissipation energy by mathematical derivation. The flow of dissipation energy shows the origin and destination of disturbance energy, so it can be used to identify the specific location of disturbance source. A recognition method for electrical quantities' steady points is also proposed based on cubic spline interpolation in order to meet the needs of energy calculation.A new thought of disturbance source location is proposed. The mechanism that disturbance source influences the units in the grid is analyzed firstly, then the relationship of phase distribution along the tie line is analyzed based on the simplified oscillation model of two machine, and a disturbance source location method for low frequency oscillation based on oscillation phase difference is proposed. The phase of oscillation with physical meaning is calculated by Hilbert-Huang transform, the oscillation phase difference is calculated to describe the oscillation phase relation of two points. The direction of the disturbance source can be traced according to the criterion of network information, and the specific disturbance source can be determined directly according to the criterion of local information in power plant. Based on the identification of disturbance source in unit level, the electromagnetic torque and mechanical torque is decoupled to synchronous torque and damping torque, and the effect of damping torque is accumulated segmently to evaluate the damping state of units' control system.On the basis of location criterion research above, the online search strategy is proposed in the fifth chapter, and the incompleteness of PMUs in power grid is also considered. Firstly, the region of disturbance source is locked quickly through thedissipation energy of section between provinces and partitions, then the specific location of the disturbance source is searched by using the suspicious-nodes-intersection positioning method and the surrounding-points positioning method based on the maximum spanning tree with active power as the weight.