Recognition and simulation of electromagnetic transients in power systems of Southern Vietnam

This paper presents a research of electromagnetic transients in power systems based on the three issues: identification of voltage transient disturbances, analysis of power system transient, and modeling of distributed-parameter transmission lines. The first issue includes (a) recognizing the presence of power quality disturbances in supply voltage and (b) classifying any existing deviations from a particular type. Various techniques using artificial neural networks and Fuzzy associative memories, Neuro-Fuzzy systems based on Wavelet transform are used to identify power quality disturbances. The second issue is to analyze the power system transients using the wavelets technique as opposed to the trapezoidal rule method. A novel developed algorithm has the following properties: 1) it is time-domain working, so that circuit nonlinearity can be handled and numerical accuracy can be well controlled, unlike the frequency-domain method where numerical error may become uncontrollable during the inverse Laplace transform; 2) the wavelets property of localization in both time and frequency domains makes a uniform approximation possible, which is generally not achieved in time-stepping methods. The last issue is to model a transmission line based on passive network synthesis for representing the nonlinear frequency dependence of the characteristic impedance matrix function. The synthesized passive network of interconnected RLC elements preserves at any frequency the inherent stability property of this matrix function for any power transmission circuits. The network parameters are identified using the constrained optimization by which the synthesized network response is matched with the actual response derived from the characteristic impedance matrix. With the trapezoidal rule of numerical integration applied to individual elements of the synthesized network, discrete time-domain recursive sequences are derived, and then included in the overall transmission circuit model. The- network synthesis procedure developed is applied to a representative transmission line, and comparative studies indicate high accuracy being achieved. The research is then applied and validated to a southern of Vietnam power system in study.