scholarly journals An Approach to Steady-State Power Transformer Modeling Considering Direct Current Resistance Test Measurements

Sensors ◽  
2021 ◽  
Vol 21 (18) ◽  
pp. 6284
Author(s):  
Henrique Pires Corrêa ◽  
Flávio Henrique Teles Vieira
Keyword(s):  
Steady State ◽  
Direct Current ◽  
Low Voltage ◽  
Power Transformer ◽  
Short Circuit ◽  
Load Flow ◽  
Resistance Test ◽  
Model Parameters ◽  
Extended Model ◽  
Proposed Model

Measurements obtained in transformer tests are routinely used for computing associated steady-state model parameters, which can then be used for load flow simulation and other modeling applications. The short circuit and open circuit tests are most commonly performed with this purpose, allowing estimation of series and parallel branch transformer parameters. In this study, an extended model is proposed which does not employ the usually assumed cantilever circuit approximation and explicitly accounts for transformer connection resistance. An estimation of the proposed model parameters is enabled by usage of additional measurements yielded by the direct current (DC) resistance test. The proposed approach is validated by means of an experiment carried out on a real distribution power transformer, whose results demonstrate that the proposed model and parameter computation approach effectively decompose total transformer resistance into winding and contact components. Furthermore, the numerical results show that contact resistance is not negligible especially for low voltage windings, which reinforces the usefulness of the proposed model in providing detailed modeling of transformer resistances.

Axial Nonlinear Mechanical Vibrations of Large Power Transformer Windings During Short Circuit

2001 ◽  
Author(s):  
Jian-Xue Xu ◽  
Zhen-Mao Chen
Keyword(s):  
Steady State ◽  
Shooting Method ◽  
Single Phase ◽  
Power Transformer ◽  
Short Circuit ◽  
Mathieu Equation ◽  
Response Force ◽  
Dynamical Response ◽  
Large Power ◽  
The Time Domain

Abstract In this paper, the axial nonlinear vibrations of the transformer winding under steady state operation case and short circuit case are studied in single degree and multi-degree models. In the case of having ampere-turn balance, the steady state response of the former model is obtained by using multi-scale method and periodic shooting method, analytically and numerically. At the same time, the computing method of Jacobi matrix in the periodic shooting method has been modified, so that the computing CPU time is saved. For multi-degree mechanical model of a single phase transformer windings, the time domain response and relation between the response and various parameters are obtained by Runge-Kutta method. For ampere-turn unbalance case, an electric-mechanical coupled problem, that the electric force depends the displacement of the winding are foomed, and the nonlinear forced Mathieu equation is established for this problem; and then the nonlinear dynamical response and global dynamical behaviors are analyzed. Finally, for a 20 MVA single phase three windings transformer, a series of short circuit experiments have been performed and the axial dynamical response force, magnetic field, strain etc. have been measured. The theoretical results well agree with the experimental results.

scholarly journals Steady-state modeling and analysis of PWM current source drives

2021 ◽  
Author(s):  
Behrang Azizi Ghanad
Keyword(s):  
Steady State ◽  
Low Voltage ◽  
Mechanical Load ◽  
Short Circuit ◽  
Current Source ◽  
Parameter Tuning ◽  
Simulation Software ◽  
Drive System ◽  
State Condition ◽  
Steady State Condition

Current source converter based ac motor drives are increasingly used in medium voltage high power applications due to their simple converter topology, inherent four-quadrant operation, reliable short circuit protection and motor friendly waveforms. The behavior of the current source drive system in the steady state condition is studied in this thesis. The main objective of this investigation is to optimize the dc link inductance, which is one of the most expensive components of the drive system. The first research focus of this thesis is to model the current source drive system in steady state condition. Different parts of the drive system such as the induction motor, mechanical load and the complicated field oriented control (FOC) scheme are simplified for the steady state operation mode. This model has two main features: 1) substantially reduced simulation time, and 2) simplified control loop design without any control parameter tuning and control instability problem. Secondly, the characteristic of the dc link circuit is investigated using the developed steady state drive system model in MATLAB Simulink. The effect of the cd link inductance on the input LC resonant frequency is studied. The value of the dc current ripple is calculated under different conditions, and the effects of different system parameters on the ripple value is investigated. Furthermore, a user-friendly simulation software is developed for the dc choke optimization. Experiments are conducted on a low-voltage (30hp, 480V) current source drive system test setup at Rockwell Automation Canada, with which the developed simulation model is verified.

scholarly journals Constant Voltage Model of DFIG-Based Variable Speed Wind Turbine for Load Flow Analysis

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8549
Author(s):  
Rudy Gianto
Keyword(s):  
Steady State ◽  
Power Systems ◽  
Power Factor ◽  
Power Plants ◽  
Flow Analysis ◽  
Load Flow ◽  
Constant Voltage ◽  
Load Flow Analysis ◽  
Proposed Model ◽  
Doubly Fed

At present, the penetration of wind-driven electric generators or wind power plants (WPPs) in electric power systems is getting more and more extensive. To evaluate the steady state performances of such power systems, developing a valid WPP model is therefore necessary. This paper proposes a new method in modeling the most popular type of WPP, i.e., DFIG (doubly fed induction generator)-based WPP, to be used in power system steady state load flow analysis. The proposed model is simple and derived based on the formulas that calculate turbine mechanical power and DFIG power. The main contribution of the paper is that, in contrast to the previous models where the DFIG power factor has been assumed to be constant at unity, the constant voltage model proposed in this paper allows the power factor to vary in order to keep the voltage at the desired value. Another important contribution is that the proposed model can be implemented in both sub-synchronous and super-synchronous conditions (it is to be noted that most of the previous models use two different mathematical models to represent the conditions). The case study is also presented in the present work, and the results of the study confirm the validity of the proposed DFIG model.

Computation of Radial Electromagnetic Forces on Power Transformer LV Windings due to Short-Circuit Currents

2013 ◽  
Vol 732-733 ◽  
pp. 1069-1073 ◽  
Author(s):  
Han Bo Zheng ◽  
Jin Hua Han ◽  
Wei Wang ◽  
Xiao Gang Li ◽  
Yu Quan Li
Keyword(s):  
Mechanical Stress ◽  
Case Studies ◽  
Calculation Method ◽  
Electromagnetic Force ◽  
Radial Direction ◽  
Low Voltage ◽  
Power Transformer ◽  
Short Circuit ◽  
Leakage Flux ◽  
Short Circuit Currents

The short-circuit electromagnetic force in radial direction induces critical mechanical stress on a power transformer. In this paper, the radial short-circuit forces which are exerted on transformer low voltage (LV) windings are investigated. Firstly, the mechanisms of leakage flux and short-circuit electromechanical forces in transformer coils are analyzed. Afterwards, based on IEC standards followed by short-circuit tests, calculations of radial short-circuit forces and evaluations of the ability to withstand short currents in LV windings are developed. The case studies and comparisons with improved measures show that the evaluation and calculation method is feasible and effective, and this method also offers three useful ways to strengthen the ability to withstand short-circuit currents for transformer windings.

Modeling of Biomimetic Robotic Fish Propelled by Passive Tail with Suitable Rigidity

2011 ◽  
Vol 304 ◽  
pp. 186-190
Author(s):  
Qing Song Hu ◽  
Juan Chen ◽  
Hua Zhou
Keyword(s):  
Steady State ◽  
Optimal Design ◽  
Physical Properties ◽  
Robotic Fish ◽  
Experimental Results ◽  
Model Parameters ◽  
Plastic Foil ◽  
Proposed Model ◽  
Biomimetic Robotic Fish ◽  
Fundamental Physical

This paper proposes a physics-based cruising speed model for biomimetic robotic fish propelled by the passive plastic foil actuator. Inspired by biological body and fins, a plastic foil with suitable rigidity and innovative structure are designed to acquire better propelling effect. The model captures the speed based on the analysis of the interaction between the tail and the water which considers the hydrodynamics. Experimental results have shown that the proposed model is able to predict the steady-state cruising speed of the robotic fish under a periodic actuation input. Since most of the model parameters are expressed in terms of fundamental physical properties and geometric dimensions, the model is expected to be beneficial in optimal design of the robotic fish.

scholarly journals Steady-state modeling and analysis of PWM current source drives

2021 ◽  
Author(s):  
Behrang Azizi Ghanad
Keyword(s):  
Steady State ◽  
Low Voltage ◽  
Mechanical Load ◽  
Short Circuit ◽  
Current Source ◽  
Parameter Tuning ◽  
Simulation Software ◽  
Drive System ◽  
State Condition ◽  
Steady State Condition

Current source converter based ac motor drives are increasingly used in medium voltage high power applications due to their simple converter topology, inherent four-quadrant operation, reliable short circuit protection and motor friendly waveforms. The behavior of the current source drive system in the steady state condition is studied in this thesis. The main objective of this investigation is to optimize the dc link inductance, which is one of the most expensive components of the drive system. The first research focus of this thesis is to model the current source drive system in steady state condition. Different parts of the drive system such as the induction motor, mechanical load and the complicated field oriented control (FOC) scheme are simplified for the steady state operation mode. This model has two main features: 1) substantially reduced simulation time, and 2) simplified control loop design without any control parameter tuning and control instability problem. Secondly, the characteristic of the dc link circuit is investigated using the developed steady state drive system model in MATLAB Simulink. The effect of the cd link inductance on the input LC resonant frequency is studied. The value of the dc current ripple is calculated under different conditions, and the effects of different system parameters on the ripple value is investigated. Furthermore, a user-friendly simulation software is developed for the dc choke optimization. Experiments are conducted on a low-voltage (30hp, 480V) current source drive system test setup at Rockwell Automation Canada, with which the developed simulation model is verified.

scholarly journals Thermal modelling of oil-filled power transformer TM - 160/10

2019 ◽  
Vol 21 (5) ◽  
pp. 141-151
Author(s):  
Nguen Tien ◽  
K. H. Gilfanov
Keyword(s):  
Software Package ◽  
Power Loss ◽  
Low Voltage ◽  
Power Transformer ◽  
Short Circuit ◽  
Thermal Characteristics ◽  
Operating Mode ◽  
Transformer Oil ◽  
Maximum Temperature ◽  
Heat Flows

The results of modeling the thermal characteristics of the dry and oil-filled power transformer TM-160/10 in idle and short circuit modes are presented. The electrical, geometric and thermal characteristics of the TM-160/10 transformer are determined. Computer modeling is performed in the software package ANSYS 17.1. The 2D distributions of temperature and density of heat flows in the transformer in the longitudinal and transverse sections are determined. It is shown that the use of transformer oil for cooling the transformer significantly reduces the temperatures in the active part. The temperature distribution occupies the range of 67-91 °С. Accordingly, the temperature of the most heated part is 91 °C and also corresponds to the low voltage winding. The dependence of the most heated point of the transformer on the operating mode was studied. A formula is proposed for calculating the maximum temperature of a transformer as a function of power loss.

scholarly journals A mathematical model for zoonotic transmission of malaria in the Atlantic Forest: Exploring the effects of variations in vector abundance and acrodendrophily

2021 ◽  
Vol 15 (2) ◽  
pp. e0008736
Author(s):  
Antônio Ralph Medeiros-Sousa ◽  
Gabriel Zorello Laporta ◽  
Renato Mendes Coutinho ◽  
Luis Filipe Mucci ◽  
Mauro Toledo Marrelli
Keyword(s):  
Mathematical Model ◽  
Steady State ◽  
Atlantic Forest ◽  
Zoonotic Transmission ◽  
Model Parameters ◽  
Transmission Cycle ◽  
Proposed Model ◽  
Vector Mosquito ◽  
Forest Strata ◽  
Human Infections

Transmission foci of autochthonous malaria caused by Plasmodium vivax-like parasites have frequently been reported in the Atlantic Forest in Southeastern and Southern Brazil. Evidence suggests that malaria is a zoonosis in these areas as human infections by simian Plasmodium species have been detected, and the main vector of malaria in the Atlantic Forest, Anopheles (Kerteszia) cruzii, can blood feed on human and simian hosts. In view of the lack of models that seek to predict the dynamics of zoonotic transmission in this part of the Atlantic Forest, the present study proposes a new deterministic mathematical model that includes a transmission compartment for non-human primates and parameters that take into account vector displacement between the upper and lower forest strata. The effects of variations in the abundance and acrodendrophily of An. cruzii on the prevalence of infected humans in the study area and the basic reproduction number (R0) for malaria were analyzed. The model parameters are based on the literature and fitting of the empirical data. Simulations performed with the model indicate that (1) an increase in the abundance of the vector in relation to the total number of blood-seeking mosquitoes leads to an asymptotic increase in both the proportion of infected individuals at steady state and R0; (2) the proportion of infected humans at steady state is higher when displacement of the vector mosquito between the forest strata increases; and (3) in most scenarios, Plasmodium transmission cannot be sustained only between mosquitoes and humans, which implies that non-human primates play an important role in maintaining the transmission cycle. The proposed model contributes to a better understanding of the dynamics of malaria transmission in the Atlantic Forest.

Nonlinear dynamic analysis of periodic ferroresonance based on a novel hysteresis approach

2016 ◽  
Vol 30 (09) ◽  
pp. 1650164 ◽  
Author(s):  
Mi Zou ◽  
Wen-Xia Sima ◽  
Ming Yang ◽  
Qing Yang ◽  
Licheng Li ◽  
...  
Keyword(s):  
Steady State ◽  
Power Systems ◽  
Power Transformer ◽  
Nonlinear Dynamic Analysis ◽  
Stability And Convergence ◽  
Iron Core ◽  
Voltage Transformer ◽  
Proposed Model ◽  
Transformer Model ◽  
Transient And Steady State

Ferroresonance is one of the most harmful and longest known power quality disturbances in the history of AC power systems. The ability of predicting transient and steady-state ferroresonance simulations mainly depends on the accuracy of the power transformer model. Most existing voltage transformer models apply single-valued nonlinear functions to represent the core nonlinearities. This study, based on our previous work, proposes a newly improved and accurate transformer iron core hysteresis model for ferroresonance simulation by extension of the classical arctangent model. To verify the proposed model’s accuracy and superiority, three different ferroresonant voltage and current waveform simulations were performed using both the proposed model and renowned EMTP Type-96 model under the same system parameters. In addition, simulation results were compared with the corresponding experimental measurements. The results indicate that the proposed model is easily implemented using numerical modeling method with good stability and convergence, and is sufficiently accurate for both transient and steady-state periodic ferroresonance analysis.

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