Studies On Key Assessment Technology Of Transmission Sections And Faults In Power System

Ensuring operation of power grid safely and efficiently is the main objectives for modern power system development. In recent years, high-performance computer technology has been able to achieve the minute level data analysis in power grid with the scale of ten thousands nodes. The grid control center can be provided with multi-time scale information source by Supervisory Control and Data Acquisition/Energy Management System (SCADA/EMS) and Wide Area Measurement System (WAMS). All these conditions give the possibility of online assessment in inter-regional power grid. In this paper, based on multiple information sources, with the objectives of studies on key assessment technologyoftransmission sections and faults, the outputs of the thesis are listed as follows:Based on studying the limitations of the research on the application of transmission section, two novel transmission section recognition methods are proposed. According to the characteristics of power flow transferring after cutting overload branch, by means of the conceptions of cut-vertex, block and the shortest path in graph theory, a cut-vertex and path searching based transmission section recognition method is presented. Meanwhile, system interconnection is selected by the electric distance and contraction partition is set by interconnection nodes. Finally, with the principle of consistency of power flow, the method for determining tie-line and the node contraction partition is proposed and the transmission corridor is determined. Through the studies of these two transmission section recognition methods, multi-angle understanding system of transmission section is established.Aim at some problems of the rapid quantitative assessment on weak transmission sections in power system, a voltage collapse indices based method for practical computation of total transfer capability is proposed. Compared to the traditional continuation power flow method, the proposed method has the following four characteristics:the proposed method is based on the original Newton method for power flow calculation, and won’t appear continuation power flow extended Jacobian matrix singular phenomenon; voltage collapse indices would be calculated according to Jacobian matrix, this parameter can lead the whole state dispatched process, the system load (and power generation) state accurate positioning to the turning point; the proposed method would select appropriate inference step size automatically according to Jacobian matrix to ensure the entire network load (and power generation) approaching to the system turning point accurately; the whole state dispatched process is based on the calculation of the Jacobian matrix without every state dispatched step having complete Newton iterative process, So that the computation speed can be improved significantly.The traditional conventional power flow calculation method has a bigger process, and is difficult to applied to the rapid assessment of total transfer capability and weak transmission section.A non-iterative power flow based method for practical computation of total transfer capability is proposed in this paper. The Taylor series was introduced into the load flow calculation. This novel method enables the real-time calculation of total transfer capability rapidly.Traditional fault location algorithm always based on some ideal measurement information condition, which made its application in actual power grid faces many problems.An effective fault location technique for transmission grids based on fault observability model is presented, and it provides a fault location scheme with the incomplete information condition in power system. High accuracy in fault location is achieved by using an accurate distributed parameter line model for the transmission lines. The performed work is provided with high performance which is featuring robustness to the uncertainties in fault inception angle, load current and fault path resistance. The transient fault data is obtained from PMUs in the proposed technique, and it does not require any information of the source impedance. This novel fault location technique does not need to be solved in an iterative manner and the calculation is fast.traditional signal analysis methods has large errors in dealing with power system fault transient signal.A modified Empirical Mode Decomposition (EMD) filtering based adaptive dynamic phasor estimation algorithm for removal of exponentially decaying DC Offset isproposed in this paper.To solve the problem of too much computational cost in the real-time implementation, this paper makes some improvement on EMD for real-time operation, including the improvement on sifting method, optimum envelopes curve fitting and a short data series selecting.