Alternative Transients Program Simulations Research Articles

Computation of Transient Profiles along Nonuniform Transmission Lines Including Time-Varying and Nonlinear Elements Using the Numerical Laplace Transform

Electromagnetic transients are responsible for overvoltages and overcurrents that can have a negative impact on the insulating elements of the electrical transmission system. In order to reduce the damage caused by these phenomena, it is essential to accurately simulate the effect of transients along transmission lines. Nonuniformities of transmission line parameters can affect the magnitude of voltage transients, thus it is important to include such nonuniformities correctly. In this paper, a frequency domain method to compute transient voltage and current profiles along nonuniform multiconductor transmission lines is described, including the effect of time-varying and nonlinear elements. The model described here utilizes the cascade connection of chain matrices in order to take into consideration the nonuniformities along the line. This technique incorporates the change of parameters along the line by subdividing the transmission line into several line segments, where each one can have different electrical parameters. The proposed method can include the effect of time-dependent elements by means of the principle of superposition. The numerical Laplace transform is applied to the frequency-domain solution in order to transform it to the corresponding time-domain response. The results obtained with the proposed method were validated by means of comparisons with results computed with ATP (Alternative Transients Program) simulations, presenting a high level of agreement.

Evaluating Harmonic Distortions on Grid Voltages Due to Multiple Nonlinear Loads Using Artificial Neural Networks

This paper presents a procedure to estimate the impacts on voltage harmonic distortion at a point of interest due to multiple nonlinear loads in the electrical network. Despite artificial neural networks (ANN) being a widely used technique for the solution of a large amount and variety of issues in electric power systems, including harmonics modeling, its utilization to establish relationships among the harmonic voltage at a point of interest in the electric grid and the corresponding harmonic currents generated by nonlinear loads was not found in the literature, thus this innovative procedure is considered in this article. A simultaneous measurement campaign must be carried out in all nonlinear loads and at the point of interest for data acquisition to train and test the ANN model. A sensitivity analysis is proposed to establish the percent contribution of load currents on the observed voltage distortion, which constitutes an original definition presented in this paper. Initially, alternative transient program (ATP) simulations are used to calculate harmonic voltages at points of interest in an industrial test system due to nonlinear loads whose harmonic currents are known. The resulting impacts on voltage harmonic distortions obtained by the ATP simulations are taken as reference values to compare with those obtained by using the proposed procedure based on ANN. By comparing ATP results with those obtained by the ANN model, it is observed that the proposed methodology is able to classify correctly the impact degree of nonlinear load currents on voltage harmonic distortions at points of interest, as proposed in this paper.

Simulation of a Self-excited Three-phase Induction Generator Using the EMTP/ATP

Three-phase self-excited induction generators (SEIGs) are often used as energy conversion devices in micro-grids for renewable energy sources such as wind, pico-hydro, bio-gas, etc. A three-phase SEIG is modeled in this paper using the Alternative Transients Program (ATP), which is a version of the Electro-Magnetic Transients Program (EMTP) commonly used in universities and private/governmental power companies. The generator’s performance at different excitation, rotating speeds and loading conditions is to be studied. Although modeling of SEIG has been well documented in literature, few have reported the use of ATP to model the SEIG, leaving several important functions of this powerful tool untapped for renewable energy applications. To bridge this gap, examples of how to model and simulate an SEIG with balanced and unbalanced loading conditions are presented. Results obtained by the analytical model, experiments and ATP simulation will be compared.

Study of MPPT Control Method for Large-scale Power Conditioning System in Hokuto Mega-solar System

AbstractFeed-in Tariff system was started from July 2012 in Japan. According to the act, the electricity energy generated from large-scale Potovoltaic (LSPV) generating stations is bought for 42 yen per kWh including tax for 20 years. This price is about 3 times as large as a normal electricity rate. However it is still important to improve efficiency of the LSPV system in order to return high investment as soon as possible. The New Energy and Industrial Technology Development Organization (NEDO) advertised for consignment research business called “Verification of Grid Stabilization with Large-scale Photovoltaic Power Generation Systems” in 2006. 2MW PV system was constructed for this research in Hokuto City and five-year tests were finished in 2011. In the research, we clarified a MPPT control method for large-scale power conditioning systems (LS-PCS) to get more PV energy efficiently. Results were confirmed by ATP (Alternative Transients Program) simulations and also the field. The verification test res...

High-Impedance Bus Differential Protection Modeling in ATP/MODELS

This paper presents a modeling of a high-impedance bus differential protection logic using the ATP (Alternative Transients Program) MODELS language. The model is validated using ATP simulations on an electrical system consisting of a sectionalized bus arrangement with four transmission lines (TLs) and two autotransformers. The obtained results validate the model and present some of the advantages of using this type of bus protection, such as fast and safe operation, even when under adverse conditions such as current transformers (CTs) magnetic core saturation upon the occurrence of external faults.

Charging Current Compensation for Distance Protection

One difficulty of the application of line protections to long transmission lines is the influence of the large capacitance of the line. When a fault occurs on a long line, relatively large magnitude harmonic components of current and voltage are superimposed on the fundamental frequency component due to the large capacitance of the line. This harmonic component can cause oscillation of the distance measurement. It is difficult to remove the harmonic component completely because the order of the harmonic component varies with several conditions. Our research has shown that the degree of oscillation can be reduced significantly by compensating for the charging current in the impedance calculation. This proposed charging current compensation (CCC) method provides an excellent result under all conditions. In this paper, the calculation method of CCC is introduced and good performance of CCC for the application to long overhead lines and to the long cable line is proven based on Alternative Transient Program simulations.

ATP modelling and field tests of the ac voltage regulator in the Palmar hydroelectric power plant

This paper presents a detailed description of a synchronous generator excitation control system in the Palmar power plant, Uruguay. It also describes the most important aspects of the Alternative Transients Program (ATP) modelling of the ac voltage regulator and exciter. Some records of time response of the excitation control system to step change in input are included. Some results of ATP simulations of the field tests mentioned before are included. Finally a comparison was made between the obtained results from simulations and those obtained from field tests in order to validate the models developed.

Atp simulation for arc‐furnace flicker investigation

AbstractAn arc‐furnace model consisting of non‐linear, time‐varying resistance, realized by the Alternative Transients Program (ATP), is presented in this paper. It is shown that the model is appropriate for flicker investigation in electrical networks supplying arc furnaces, constituting a valid alternative to the linear arc modelling realized by amplitude modulation of voltage generators. Block diagram of the procedure for ATP modelling of the nonlinear, time‐varying arc resistance, dynamic voltage‐current characteristic of the furnace electric arc, voltage and current arc waveforms and characteristic curves of an arc furnace, obtained by ATP simulation, are presented, referring to circuit parameters taken from an actual plant and to a sinusoidal law for arc‐length time variation. Aflickermeter ATP simulation is realized to derive equivalent voltage‐variation values in agreement with the actual flicker measurements.