Secondary Current Research Articles

Robust control technique in power converter with linear induction motor

Induction motors are widely used in industrial applications as actuators, thanks to their simplicity of construction, which is subsequently reflected in low-cost maintenance. This paper shows the behavior of a three-phase power converter with a linear induction motor (LIM) as load, using a quasi-sliding control technique for output voltage regulation and a new control technique to control chaos. Digital pulse width modulation (DPWM) techniques are widely used to control electronic power converters. The controller proposed in this paper was designed using zero average dynamic (ZAD) and fixed point inducting control (FPIC) techniques. The ZAD-FPIC control strategy was designed and applied to a three-phase converter with linear induction motor load. Since it is not possible to measure the secondary currents, a secondary current observer was included in the system. Finally, bifurcation diagrams are shown as a technique for tuning controller parameters in ZAD-FPIC controllers. For the illustration of numerical results a simulation of the linear induction motor drive controlled was made by MATLAB/Simulink. The designs were tested in a rapid control prototyping (RCP) system based on digital signal processing (DSP) for dSPACE platform, using the 1103 controller card and control desk interface.

A Novel AlGaN/GaN Transient Voltage Suppression Diode with Bidirectional Clamp Capability.

This work proposes a novel AlGaN/GaN transient voltage suppression (TVS) diode (B-TVS-D) with bidirectional clamp capability, which consists of a small-size AlGaN/GaN monolithic bidirectional switch, two 2DEG-based current-limiting resistors (R1A/R1C, in parallel connection between the gate electrodes and the neighboring ohmic-contact electrodes (anode/cathode)), and a 2DEG-based proportional amplification resistor (R2, in parallel connection between two gate electrodes). It is demonstrated that the proposed B-TVS-D possesses a symmetrical triggering voltage (Vtrig) and a high secondary breakdown current (Is, over 8 A, corresponding to 12 kV human body model failure voltage) in different directional electrostatic discharge (ESD) events. The proposed diode can effectively enhance the electrostatic discharge robustness for the GaN-based power system. It is also verified that R1A/R1C and R2 have an important impact on Vtrig of the proposed B-TVS-D. Both the decrease in R2 and increase in R1A/R1C can lead to the decrease of Vtrig. In addition, the proposed B-TVS-D can be fabricated on the conventional p-GaN HEMT platform, making the ESD design of the GaN-based power system more convenient.

Effect of MeV ion induced heating on secondary electron emission from Si surface and estimation of local temperature

We report the variation of secondary-electron yield and target temperature with the variation of ion beam intensity during 100 MeV N+5 bombardment on Si surfaces. Theoretical understanding of secondary-electron emission during ion bombardment predicts no variation of yield with ion beam intensity. We discovered that the variation of secondary-electron yield arises due to the rise of local temperature at ion impact sites of the target. The secondary-electron yield first decreases with the increase of ion beam current but subsequently, it increases with the further rise of beam current. The initial decrease is due to the temperature-dependent change of electrochemical potential of Si. The considerable increase of the secondary-electron yield with a further increase of ion beam current is caused by local surface heating and subsequent additional thermionic electron emission. We have estimated the surface temperature of ion-impact sites by separating the thermionic electron current from the collisional secondary electron current.

An Artificial Neural Network Developed in MATLAB-Simulink for Reconstruction a Distorted Secondary Current Waveform. Part 2

Recently, there has been an increased interest in the use of artificial neural networks in various branches of the electric power industry including relay protection. The operation of the traditional microprocessor-based relay protection device is based on calculation the RMS values of the monitored current and voltage signals and its comparison with the predetermined thresholds. However, calculated RMS values often do not reflect the real processes occurring in the electrical equipment under protection due to, for example, current transformer saturation. In this case secondary current has a characteristic distorted waveform, which is significantly differs from its ideal (true) waveform. This causes underestimation of the calculated RMS value of the secondary current compared to its true value; also, it causes a trip time delay or even to a relay protection devices operation failure. In this regard, one of the perspective applications of the artificial neural network for the relay protection purposes is the current transformer distorted secondary current waveform restoration due to its saturation. The article describes in detail the stages of the practical implementation of the artificial neural networks in the MATLAB-Simulink environment by the example of its use to reconstruct the distorted secondary current waveform of the saturated current transformer. The functioning of the developed neural networks was verified in the MATLAB-Simulink environment; with the use of the SimPowerSystems component library a model was implemented which allow simulating the current transformer saturation, accompanied by the secondary current waveform distortion, and its further restoration using developed artificial neural networks. The obtained results confirmed the ability of the neural networks that had been developed to almost completely restore the distorted secondary current waveform. Thus, it seems promising to use pre-trained artificial neural networks in real relay protection devices, since such use will ensure the speed of real relay protection devices; their operation reliability will also increase.

The Secondary Electron Collection Effect of Biased Printed Circuit Board Traces in Box IEMPs

Under X-ray irradiation, a printed circuit board trace with a positive bias voltage within an electronic enclosure could generate a secondary electron collection effect. This effect is attributed to box internal electromagnetic pulses and can result in the collection of nearby secondary electrons outside the trace and generate a secondary electron current. A secondary electron collection effect model is established based on yield models of secondary and backscattered electrons as well as motion models of the primary, secondary, and backscattered electrons. Compared with the existing models, the results obtained through this model are more accurate. The results show that an increase in bias voltage and X-ray fluence could enhance the secondary electron current and an increase in X-ray fluence could significantly change the waveform of the current, which includes advancing the first peak time and delaying the maximum peak because of the space-charge-limited effect. The influence of a biased trace on an adjacent unbiased trace depends on the secondary electron collection distance. Moreover, if two adjacent traces have opposite bias voltages, the secondary electron current of the positively biased trace could be enhanced whereas that of the negatively biased trace could be weakened.

Neutral Reactor Structures for Improved Single Phase Auto Reclosing in Multi-Circuit Multi-Voltage Transmission Lines

In this paper, novel neutral reactor structures are proposed to mitigate the secondary arc current (SAC) in non-conventional Multi-circuit Multi-voltage Transmission lines (MCMVTLs). The parameters of the reactors in the structure are optimized using the Non-dominated Sorting Genetic Algorithm II (NSGA-II). The optimization algorithm, coded in Python, regulates the multiple runs of an Electromagnetic Transients (EMT) simulation program to minimize the secondary arc current. The optimization trials are run in parallel on a 64 core computer to minimize the solution time. A detailed arc model was tested on the EMT program (PSCAD). Using this model and optimized parameters in the proposed neutral reactor schemes, the SAC is indeed extinguished in acceptable times. The SAC and TRV for neutral reactors with optimized parameters are up-to 68 and 77%, respectively, lower than the ones with parameters calculated by the conventional approach which ignores inter-circuit coupling. Meanwhile, the extinction times are up-to 46% faster. As a result, single-phase auto-reclosing in MCMVTLs is viable.

Experimental Study on the Extinction Characteristics of Secondary Arc Under Different Secondary Arc Currents Near Outdoor Insulator

On the transmission lines, the secondary arc is the arc that remains at the fault point after the short-circuit current is interrupted, which may pose a threat to the stable operation of the power system. In this article, the extinction characteristics of secondary arc near an outdoor insulator under different secondary arc currents are studied experimentally. The secondary arc has different extinction characteristics under different secondary arc currents of 10, 30, and 50 A. The arcing time, length, morphology, diameter, and breakdown voltage of secondary arc are discussed. Experimental results show that, with the increase in the secondary arc current, the arcing time also increases. The development of the secondary arc has stage characteristics. The length of the secondary arc increases steadily in the first stage and fluctuates greatly in the second stage. In addition, during the single discharge in the second stage, the morphology of the secondary arc will change significantly. The breakdown voltage of the upper electrode in the negative polarity is higher than that in the positive polarity, and it is found that this polarity effect is related to the motion of the secondary arc in space. The research results could provide some reference for investigating the physical characteristics and suppression measures of secondary arc.

A Novel Bidirectional AlGaN/GaN ESD Protection Diode.

Despite the superior working properties, GaN-based HEMTs and systems are still confronted with the threat of a transient ESD event, especially for the vulnerable gate structure of the p-GaN or MOS HEMTs. Therefore, there is still an urgent need for a bidirectional ESD protection diode to improve the ESD robustness of a GaN power system. In this study, an AlGaN/GaN ESD protection diode with bidirectional clamp capability was proposed and investigated. Through the combination of two floating gate electrodes and two pF-grade capacitors connected in parallel between anode or cathode electrodes and the adjacent floating gate electrodes (CGA (CGC)), the proposed diode could be triggered by a required voltage and possesses a high secondary breakdown current (IS) in both forward and reverse transient ESD events. Based on the experimental verification, it was found that the bidirectional triggering voltages (Vtrig) and IS of the proposed diode were strongly related to CGA (CGC). With CGA (CGC) increasing from 5 pF to 25 pF, Vtrig and IS decreased from ~18 V to ~7 V and from ~7 A to ~3 A, respectively. The diode’s high performance demonstrated a good reference for the ESD design of a GaN power system.

The.main types of wind turbines-generators in the power supply system

THE PURPOSE. This paper considers the problem of relay protection functioning when the current transformer reaches the saturation mode which is provided by transient processes.METHODS. MATLAB Simulink software environment allows reproducing the method of statespace representation by using structural blocks. The model is verified by comparison the time to saturation, obtained by calculation and according to the graphical data of the model. The separation of variables method extracts and graphically displays the investigated components.RESULTS. This paper reveals that applying the requirements of IEC 61869-2:2012 standard, which determines the worst combination of series of unfavorable factors for current transformers in transient mode, can influence a serious impact on the correct operation of relay protection based on current, reactance or differential principle of action. Saturation of the current transformer can lead to both negative results: false operation of relay protection devices and their failure.CONCLUSION. According to the results of the study, it was determined that the presence of a DC component in the primary short-circuit current has the greatest effect on the protection operation. The delays in the restoration of the RMS value of the short-circuit current reached up to 0.3 seconds, which is comparable with the response time of the second protection zones for microprocessor-based relay protection devices. The DC component of the primary current and the presence of residual magnetic induction of the current transformer provides the largest content of the magnetization current, the largest angular error and also the largest content of the second harmonic component in the secondary short-circuit current.

The Influence of the 3rd Harmonic of the Distorted Primary Current on the Self-Generation of the Inductive Current Transformers

This paper investigates for transformation of the distorted current the low order higher harmonic self-generation phenomenon of tested inductive current transformers. The influence of the main component and the 3rd harmonic of the distorted primary current on the RMS values of the 5th, 7th and 9th order self-generated higher harmonics is analyzed. This research indicate that the change of the RMS value of the 3rd harmonic of the distorted primary current causes variation of the lower order higher harmonics generated in to the secondary current. Therefore, this is a challenging phenomenon which have to be considered while compensating the values of current error and phase displacement of the inductive CTs during transformation of the distorted currents.

A Novel Anti-DC Bias Energy Meter Based on Magnetic-Valve-Type Current Transformer

The direct current will cause the electromagnetic current transformer (CT) saturation, which will lead to the measurement error of some energy meters using CT for current sensing. This article presents a novel anti-dc bias energy meter. In the proposed approach, the magnetic-valve-type current transformer (MVCT) is used as the current sensor in the meter instead of conventional CT. As a result, the distorted secondary current can be fully compensated within MVCT when the core gets saturated. The principle of the new technology is described in detail. The simulations and experiments are performed to verify the correctness and feasibility of this novel energy meter when measuring load power consumption with dc bias.

ЕЛЕКТРОХІМІЧНА ГІДРОГЕНІЗАЦІЯ ФРОНТАЛЬНОЇ ПОВЕРХНІ СОНЯЧНИХ ЕЛЕМЕНТІВ ТА ЇХ ДОСЛІДЖЕННЯ МЕТОДАМИ МАСС-СПЕКТРОСКОПІЇ

Purpose. Texturing of the silicon surface, both by chemical and electrochemical etching, is an integral part of the technology of modern high-performance silicon solar cells. The texture on the front surface of the solar cells not only reduces reflection losses, but also helps to capture long-wave light in the SC structure, thereby expanding its operating spectral range and increasing the short-circuit current. In this regard, the study of the PSi layer in a nanotexture by mass-spectroscopy on the functional properties of the frontal silicon surface, which was pre-textured, is of particular interest. Methodology. The study of all stages of formation of hydrogenated porous structure and identification of technological patterns that affect the characteristics of the obtained nano-, meso-, macropores are very important, because most of the porous parameters are laid at the stage of formation of nucleation (seed) centers. In order to improve the passivating properties of PSi layers used in solar cells, the process of electrochemical hydrogenation of PSi as on p - type silicon substrates with a resistivity of 0.1 ÷ 10 Ohmsm also on substrates with a formed emitter junction n+- p of conductivity was studied. Various solutions were used as the electrolyte, such as (HF: C2H5OH=1: 1), (HF: C2H5OH=1:2) and so on. The current density and anodizing time varied over a wide range of values, which allowed the formation of PSi layers with different porosity and thickness. A solution of HF: C2H5OH = 1: 1 was used as the electrolyte. The anodizing current and time varied over a wide range of values to obtain PSi layers with different porosity and thickness. To determine the conditions of the process of electrochemical hydrogenation of PSi during its cathodic polarization, potentiostatic current-voltage curves of the system Pt (anode)-electrolyte-porous silicon/ silicon (cathode) for electrolytes with different chemical composition were taken. Finding. Comparison of the surface appearance of Baysix type multicrystalline silicon samples before and after hydrogen hydrogenation in an electrolyte based on hydrofluoric acid ((HF: C2H5OH=10:1), (HF:C2H5OH=10:2) and so on), both in the secondary ion Spectra and in the image of the distribution of elements over the surface (mass spectral ion microscope and Ion microzond mode). Originality. We get a 2D image (size 200x200 microns) of the surface of the current of secondary ions H+ hydrogen and 2D image of the secondary ion current of molecular SiH2+ the surface of a Baysix type multicrystalline substrate passivated with hydrogen by hydrogenation, which is comparable to the optical image of a pure silicon surface that has been hydrogenated. From the form of 2D-ion images, as well as their individual parts, it can be seen that all the difference in the current intensity of the secondary ions is due to the topography of the surface of the samples. Practical value. The prospects of creating efficient solar cells using multifunctional multi-textures of porous silicon are shown. References 24, figures 6.

Intensifications reactive power during of asymmetric network outages in dual-stator winding generators

<span lang="EN-US">The paper proposes a protection to dual stator generator, reluctance rotor, from asymmetrical fault. Which prevents the dual stator generator, reluctance rotor, from electrical sage through working process in order to avoid any interruption in the generator-grid connection. The procedure consummated with injecting suitable reactive power during the fault period. The proposed method that makes it possible for wind turbine application via dual stator winding generators (DSWRG) synchronous mod to stay connected to the grid during asymmetrical faults. It has been built according to trusted simulating mode considering all tested parameters according to experiment work. The expirment, consider the DC link side stability and care about the behavior and performance of machine side parameter. As well the machineability is evaluated to ride through asymmetrical fault by observing the secondary side current which has a big role in saving grid side converter. The control takes a response within 200 ms after fault trigger recognition. The generator ability of dynamically remaining connected stable and existing in the network, which is sustained a series voltage disturbance by injecting appropriate amount of reactive power. The main interest required in this paper is the capability of a machine to overcome the asymmetrical fault.</span>

A Quasi-Z-Source-Based Inductive Power Transfer System for Constant Current/Constant Voltage Charging Applications

This article proposes a quasi-Z-source (qZS)-based Inductive Power Transfer (IPT) system for Electric Vehicles (EVs) charging applications. The IPT systems use the magnetic field to transfer power between two coils wirelessly, achieving improved reliability, safety and less environmental impact. Compared to the conventional IPT system, the proposed qZS-IPT system simultaneously achieves DC/DC regulation and DC/AC conversion through a single-stage conversion, thus lowering the cost and complexity of the system. Moreover, the reliability of the system is improved thanks to the qZS network shoot-though immunity and the reduced number of switches. To ensure the battery efficient charging and long service life, the constant current/constant voltage (CC/CV) method is considered. With the proposed innovative modulation scheme, the qZS can easily change between buck and boost modes, respectively, lowering or increasing the secondary side current. A theoretical analysis is presented for system design. Simulation results based on a 25 kW (200 V/135 A) low duty EV charger are presented to verify the effectiveness of the proposed scheme. Experimental tests are performed on a 150 W scale-down prototype to validate the analysis and demonstrate the effectiveness of the proposed qZS-IPT system for CC/CV chargers.

Numerical Study on Mechanism and Optimization of Pulsed Discharges Without Voltage Plateau Phase

In recent years, pulsed discharges at atmospheric pressure have attracted extensive attention due to their remarkable discharge advantages. In this article, a fluid model is applied to investigate a new type of pulsed dielectric barrier discharge (DBD), characterized by a sharp rising phase and slow falling phase but without a plateau phase, which could be realized by using a circuit composed of a device called silicon diode for alternating current (SIDAC). Based on the computational data, the influences of voltage waveform on the plasma density and electric field are carefully discussed. The simulation results show that only one significant discharge event occurs during the voltage rising phase, which produces a large electron density with high electron temperature, but the secondary discharge current cannot be observed due to the slow voltage falling phase. We also qualitatively investigate the effects of discharge parameters on the plasma dynamics, such as the relative permittivity, barrier thickness, and repetitive frequency from simulation data, which agree well with the experimental observation. Based on the simulation results, the optimization of this pulsed discharges to enhance the electron density and improve the electron temperature is discussed, thus promoting the wide applications of the pulsed discharges.

Open-channel flows through emergent rigid vegetation: Effects of bed roughness and shallowness on the flow structure and surface waves

Free-surface flows through a staggered cylinder array were investigated in an open-channel flume. The cylinders simulated rigid emergent vegetation. Specifically, we studied four flow cases with a two-factor design comprising flow rate (7 and 13 l s−1) and bed-surface state (hydraulically rough and smooth). We have primarily assessed the effects of bed roughness and shallowness on the time-averaged flow structure and the transverse fluctuating flow motion in the cylinder wake. Secondarily, the effects of the former on the vortex-shedding-induced surface waves were quantified. To gain further insight into the bed roughness effect on flow structure, we conducted transient flow simulations using a hybrid Reynolds-Averaged Navier–Stokes/Large Eddy Simulation turbulence model. For all cases, downstream of a cylinder, an upward flow occurs and two counterrotating secondary current cells develop. The two cells bring high-momentum fluid from the high-speed region into the cylinder wake, resulting in a near-bed streamwise velocity-bulge. The measured upward flow and velocity-bulge are greater for the rough-bed cases than for the smooth-bed cases. The simulated upward flow and velocity-bulge increase with an increasing roughness height, while secondary currents decay faster in the longitudinal direction. For the rough-bed cases, in the cylinder wake, the transverse fluctuating flow motion is hindered by the rough-bed induced turbulence over the whole water column, irrespective of the shallowness level. Coupled with the fluctuating flow motion, we have observed for three flow cases noticeable surface oscillations (termed “seiche waves”), whose amplitude decreases with decreasing flow depth. Under the combined effects of strong shallowness and a rough bed, seiche waves vanished.

Study on the Influence of Injected Lightning Current on the Space-Time Evolution of Secondary Arc

The timely extinction of secondary arc is of great significance to the single-phase reclosing of transmission lines. However, very little research has been carried on the space-time evolution of secondary arc under lightning strikes. In this article, considering the electromagnetic force, thermal buoyant force, wind load and air resistance in the motion of secondary arc, a chain arc model was established, which was combined with the double exponential function injected lightning current model. The motion of secondary arc and the change of arc extinction time with or without injected lightning current were observed. The results show that lightning could accelerate the motion of secondary arc and shorten the extinction time of secondary arc. Then, by adjusting the different parameters of injected lightning current function, lightning start time, and lightning duration, the impact of various factors on the motion process of secondary arc and extinction time was obtained. Different wind loads and secondary currents were selected to observe the impact of the same injected lightning current with different secondary current and arc movement environment. The results show that a higher injected lightning current level and a lower secondary current could both make the impact of the injected lightning current more obvious. The lightning duration and lightning start time would not have a significant impact on the extinction of secondary arc. Lightning can reduce the difference between secondary arcs under different winds, and further promote the extinction of secondary arcs. The abovementioned research work can provide some reference for the protection of secondary arc in thunderstorm field.

Nonlinear Shear Effects of the Secondary Current in the 2D Flow Analysis in Meandering Channels with Sharp Curvature

In order to analyze the shear effect of secondary currents on the flow structures in a meandering channel, this research developed a two-dimensional shallow water model, which included the dispersion stress term accounting for the shear effect in the vertical velocity profile. A new equation for the vertical velocity profile that included nonlinear shear effects was derived from the equation of motion in the meandering channel with sharp curvature. Using the experiment data obtained from large-scale meandering channels, the ratio of the depth over the radius-of-curvature was incorporated into the shear intensity of the secondary flow in the proposed equation. Comparisons with the experimental results by previous research showed that the computed values of the primary velocity distribution by the proposed model showed better fit with the observed data than the simulations with linear models and models without secondary flow consideration. The simulated results in the large-scale meandering channels demonstrated that simulations with the nonlinear secondary flow effect added into modeling gave higher accuracy, reducing the relative error by 19% in reproducing the skewed distributions of the primary flow in meandering channels, particularly in the regions where the effects from spiral motion were strong, due to sharp meanders.

Optimizing multi-circuit transmission lines for single-phase auto-reclosing

In this paper, novel multi-circuit transmission line (MCTL) designs with low secondary arc current (SAC) values are proposed. The Non-dominated Sorting Genetic Algorithm II (NSGA-II) was used to generate the optimized tower structures. The aim is to select the MCTL configuration that satisfies multiple objectives such as increased capacity, reduced cost, right-of-way (ROW), and tower height, while satisfying several constraints such as SAC limit, ampacity, electric field, etc. The objective function is formulated as a mathematical function of design variables such as sub-conductor position, phase arrangement, etc., and several constraints. Two-port theory is used to calculate the SAC resulting from different faults along the line, which is significantly faster compared with time-domain Electromagnetic Transient (EMT) simulations. Comparisons of MCTLs with and without SAC constraints are presented, clearly showing the importance of taking into account SAC limits during the optimization process. As a result, MCTL structures with SAC reductions of up-to 64% were obtained, indicating that the MCTL are able to successfully handle Single Phase Auto-Reclosing (SPAR).

Графический метод расчёта вторичных токов дуги в линиях сверхвысокого напряжения

The article discusses the issues of calculating secondary arc currents in the implementation of single-phase auto-reclosing for the elimination of unstable single-phase damages in ultra-high voltage lines of 500, 750 kV. The dependences of the extinguishing time of the feeding arc and the dead time of the single-phase auto-reclosing recommended in the literature on the amplitude of the forced component of the secondary arc current are given. A graphical method is proposed for calculating the secondary arc currents in ultra-high voltage lines in the dead time mode of the single-phase auto-reclosing. The adequacy of the simulation of the recharge arc is confirmed by comparing the calculated and experimental data as applied to the 750 kV line with a length of 525 km. Examples of using the graphical method for calculating the secondary currents of the recharge arc in 500 kV lines of various lengths are given. The features of the implementation of single-phase auto-reclosing in the line with a length of 300 and 1000 km and, in particular, the influence of zero-power reactors included in the neutral of shunt reactors are noted. An example of the implementation of single-phase auto-reclosing using automatic phase shunting in a 500 km line is also considered.