Modeling VSC with Active/Reactive Current Excitation and Internal Voltage Response for Grid Amplitude/Frequency Modulation Dynamics Analysis

This paper provides a method and a system based on current pulse excitation and frequency spectrum analysis, which can complete battery impedance spectrum test and analysis. By exerting current excitation onto the battery, synchronously measuring current excitation and terminal voltage response, we count the amplitude spectrum and phase spectrum for current excitation and terminal voltage response under different frequencies. Also, we count the battery impedance under different frequencies according to spectrums of I and U, to get the complete spectrogram for the battery impedance. The technology provides a new solution for calculating and predicting the charge state and health state of the storage battery.

The aim of this work is to analyze different formulations of the voltage excitation problem and the current intensity excitation problem for the time-harmonic eddy-current approximation of Maxwell equations in the case of a conductor with electric ports. Two formulations based on the introduction of a vector magnetic potential and their finite element approximation are analyzed.

The application of hybrid excited synchronous generator as a part of autonomous wind turbine is studied in a case of load and wind speed changes. The control system of autonomous wind turbine ensures maximum wind turbine power output at any given wind speed. Maximum power achieved by excitation current control in additional field winding. The excitation current and power control of generators is developed based on minimization of local functionals of instantaneous values of first order derivative of electromagnetic energy. It provides robustness to parametric and coordinate disturbances and high quality of control. On the example of an experimental sample of a synchronous generator with hybrid excitation the studies of maximum output power control of autonomous wind turbine were carried out. The study is carried out in a case of wind speed variation from 3 to 8 m/s and load increasing by 50%. The graphs of output power of wind turbine, speed and torque of generator, excitation and armature voltage sand currents are given.

Generator or alternator is a device that has a function to convert or transform mechanic energy to electricity. Electricity conversion need process with giving strengthening with excitation current to coil magnetic field that placed on sync generator. Excitation current that flows on magnetic field coil will cause magnetic flux. Generator sync on PLTU unit 3 and 4 PJB UP Gresik use excitation system with excitation static type, this type of excitation it uses carbon brush as a media to conduct excitation current, this excitation system use the output of sync generator. In reality this excitation current which exist on PLTU unit 3 and 4 have to should always be taken care so the system can operate normally and commonly the fault that happened is under excitation and over excitation so it can be prevent. Step taken to avoid damaging the generator sync that caused by excitation current, steps that have to be taken are understanding the characteristic of system excitation setting, anchor current, voltage generator, and loading. The value of loading is very affecting the value of excitation current that injected to generator, the purpose of this process of excitation current injection is to maintain the stability from sync generator voltage so that the condition is staying on its normal condition.

In this paper, the hysteresis characteristics of a transformer core are determined from limited on-line measured voltages and currents under certain excitations. A method for calculating the magnetization curve and hysteresis loops of the transformer core under various excitation is developed based on limited excitation conditions, and using the deep neural network, support vector regressor and the Wlodarski model. The coercivity and the amplitude of magnetic field strength of hysteresis loops can be captured with high accuracy based on this method. Then, a finite element model of the transformer core is constructed to predict the distributed magnetic flux density and the excitation current using the calculated hysteresis loops. The currents from various excitation voltages on two different transformer structures are also measured to compared with simulated currents. The outcome indicates that the overall hysteresis loops and magnetization curve of the transformer core may be useful for modeling the magnetic field and excitation current under any voltage excitation.

We present a method to model organic light-emitting devices driven by a current source in the context of drift-diffusion models. The method is extended to the case of voltage excitation, and calculations with current and voltage excitation are compared. An advantage over the application of Poisson's equation is that standard numerical solvers can be used for the ordinary differential equations that result from the spatial discretization of the model equations. We employ the model to calculate I- V characteristics and to examine the transient response of an organic light-emitting diode under pulsed current operation. The approach is generalized to the case of an arbitrary number of layers.

We give a systematic presentation of voltage or current intensity excitation for time-harmonic eddy-current problems. The key point of our approach resides in a suitable power law that permits us to understand the role of voltage excitation. We also shed light on the influence of the boundary conditions on the proposed formulations.

Synchronous machines are basic components of systems. Their steady-state performance is a fairly important subject. In general, synchronous generators are connected to network systems through the transmission lines. Therefore, stability analysis is made including the whole system. In this study, a synchronous machine has been examined alone and V-curves have been obtained for motor current amplitude, and wave shape variations have been researched for lagging PF operation. As is known, synchronous machines have to be excited with direct current. In synchronous machines inductive, resistive or capacitive performance as motor mode operation can be obtained by varying amplitude of excitation current. In the generator mode operation, the amplitude of the voltage generated by the synchronous machine can be adjusted with excitation current. In this study, changing of the stability limit of the synchronous motor has been investigated experimentally by changing the amplitude of excitation beside wave shape variations. V-curves and stability limits obtained, studied with five different shapes of the excitation voltage, are listed as excitation with pure direct current supplied from a battery, excitation with vibratory direct current supplied from a generator, excitation current with square and sinusoidal wave rectified half waveform and excitation current with sinusoidal wave rectified full waveform.

SummaryIn this paper, we consider some potential formulations of electrostatic as well as time‐harmonic eddy current problems with voltage or current excitation sources. The well‐posedness of each formulation is first established. Then, the reliability of the corresponding residual‐based a posteriori estimators is derived in the context of the finite element method approximation. Finally, the implementation in an industrial code is performed, and the obtained theoretical results are illustrated on an academic and on an industrial benchmark. Copyright © 2015 John Wiley & Sons, Ltd.

As the calculation of transformer no-load characteristics measured by low-frequency test method is not perfect, different interpolation methods are explored to fit and convert the transformer's volt-ampere characteristics under power frequency (50 Hz) excitation to find the best interpolation fitting conversion method. The no-load test of transformer is carried out by using 10 Hz, 15 Hz, 20 Hz low-frequency square wave and triangular wave excitation. Then the measured excitation voltage, excitation current and no-load loss are converted to those of 50 Hz sine wave excitation. The converted volt-ampere characteristic curve is calculated by the proposed algorithm, and compared with the measured results under the 50 Hz sine wave excitation. Experiments show that under the condition that the magnetic flux amplitudes are equal at each frequency of non-sinusoidal and sine waves, whether it is square wave or triangular wave excitation, the volt-ampere characteristic curve converted to the 50 Hz sine wave excitation by the proposed method can better approximate the curve of the measured 50 Hz sine wave excitation. The average values of the relative errors of the converted excitation current of the three frequencies are within 4%, and those of the converted excitation voltage of the square wave are within 1.1%, and those of the converted excitation voltage of the triangular wave are within 0.47%. Compared with the generalized Steinmetz equation method and the multi-frequency method, the proposed method has a better conversion effect and can almost replace the no-load test results of the 50 Hz sine wave, which has practical value in engineering.

For an electric power system (EPS) of the combined propulsion complex (CPC), working on a constant-power hyperbola (CPH), the strategy of managing power distribution between propulsion electric motors and own needs consumers has been improved. The study reported here aimed to reduce fluctuations in current consumption and load by optimizing voltage controllers and the rotation frequency of generator assemblies (GA). The system of EPS GA voltage and frequency stabilization was synthesized by determining, in the system of equations, the dynamics of the values of EPS links' time constants and the coefficients that correspond to control parameters. To define the characteristics of the control signals from the regulators of EPS GA rotation frequency and excitation voltage, the laws that control the speed and excitation current were calculated. After sampling the coefficients of the GA speed control regulator, the tasks for the excitation voltage controller were determined. The methodology of data acquisition was applied on the basis of a correlation between the EPS characteristics and the experimental characteristics of GA. The system of EPS dynamics equations was optimized in accordance with the structure and settings of the optimal controller and the probability of a situational error by using Spearman's rank correlation coefficient. The optimization has made it possible to reduce the likelihood of a situational error during the synchronization of GA and enable the stable operation of GA close to the mode of operation on CPH. The power controller was tested under the mode of changing the load of own needs with the power levels of EPS on CPH in the range of 50‒100 % of the rated power. The range of deviations of the current consumed with an enabled GA rotation controller was 10 % of the average value. The range of EPS power deviations with the power controller turned on was 5 %.

The Nigeria 330 KV integrated power network consisting of seventeen (17) generating stations, sixty four (64) transmission lines and fifty two (52) buses is studied, to investigate the time limits of stability before, during and after occurrence of a three phase (3-θ) fault on the largest generating station (Egbin) and to determine also the most affected generating stations and buses in the network.Theswing and torque equations expressed in time domain was used for the study and the network was modeled in ETAP transient analyzer environment. Transient stability time limit of the system was set to operate at maximum value of ten (10) seconds. Before the fault (between 0.000secs-0.0006secs), the system dynamics was not affected and the peak values of terminal current, rotor angle, frequency,mechanical and electrical power obtained were observed to be within stability region. However, as the fault occurred between 0.0006 secs-0.042 secs, the system dynamics changes, thus affecting the quadrature axis. This change in quadrature axis affected the individual generator’s exciter current, exciter voltage, electrical power, mechanical power, frequency, rotor angle and terminal current, though still remain within stability boundary. However, when the fault is cleared within this time, the system returns to its stability region. When the fault lasted beyond 0.042 secs, there is loss of system synchronism. Generating stations that were majorly affected are Omotosho, Sapele, AES and Delta stations. It was observed that the bus voltages connected to these stations deviated from the statutory limit of 313.45 KV-346.5 KV. Their bus voltage values were: Omotosho (361.42KV), Sapele (358.42 KV), AES (350.43 KV) and Delta (364.32 KV). The other buses connected to the other generating stations were however not affected. The province’s population is expected to grow by about 28 percent – or about 3.7 million people – by 2030 and become increasingly urbanized. The structure of the economy will also change as the high-tech and service sectors grow and demand from large industries is expected to grow moderately.

Modeling of MEMS resonator piezoelectric disc by means of an equicharge current source method

The temperature of the semiconductor bridge increases due to the Joule heat effect in the way of capacitive discharge voltage excitation and current excitation, but the temperature distribution and the effect of different excitation methods and different sizes on the temperature change are not very clear; aiming at this problem, the temperature distribution of the semiconductor bridge after electrical energy excitation is simulated by finite element simulation. The effects of excitation mode and bridge area size on the temperature rise process of the bridge were studied by the control variable method; finally, the high-temperature area of the bridge body is only distributed in the bridge area, the temperature of the bridge body is positively correlated with electrical energy but negatively correlated with the area of the bridge area, and the current excitation method is better than the effect of voltage excitation. In addition, the conclusion is that the appropriate increase in excitation energy and the reduction of bridge size can help the temperature rise to improve the efficiency of the semiconductor bridge in practical applications.

The electrical tomography technology is a multi-phase flow detection technology. This technology has the advantages of non-radiation, non-invasive and visualization, can be widely used in traditional energy field and new energy field. The permittivity and conductivity, as the basic electrical parameters of material, are closely related to the distribution of material in multiphase flow. However, in the actual multiphase flow, due to the non-uniform distribution of permittivity and conductivity in time and space, the accuracy and validity of measuring instruments are challenged. The main target of this research is to investigate the application of electrical capacitance tomography (ECT), electrical resistance tomography with voltage excitation (ERTv) and electrical resistance tomography with current excitation (ERTc) on the multiphase flow with complex permittivity and conductivity distribution. The final objective based on the above research is to provide suitable tomography modual for different multiphase flow process. The experimental results show that ECT is suitable for measuring dry gas-solid fluids. ERTv is better for measuring high water content gas-solid fluids and low conductivity gas-liquid fluids, while ERTc is better for measuring continuous phase conductivity gas-liquid fluids.