Voltage Orientation Research Articles

Fabricating orientated nanofibrous meshes with a bespoke ultra-cost-effective electrospinning machine

Electrospinning's production method has been streamlined and perfected because to advancements in technology and increased demand. While working with electrospun fibers, it is crucial to ensure that they are collected in the correct orientation. Electrospun fibers can be either aligned or random. In contrast to randomly oriented fibers, all aligned ones will point in the same direction. Our results show that a low-cost, tailored electrospinning device can achieve equivalent performance to that of a commercially available system. High voltage (up to 36 kV) and nanofiber orientation adjustments are now being made to the proposed device. A high-voltage direct-current electrical power supply that is custom-built per order and wired by hand. Two specialized collectors, one portable and manufactured from conductive material for random nanofibers, and the other an inexpensive rotational drum collector for aligned nanofibers, have been developed to allow for precise orientation control. By applying Image J software to scanning electron micrographs, we were able to determine the average diameter and orientation of the fibers produced by the electrospinning apparatus, demonstrating its potential to produce nanoscale directed fibers. Because of this research, it's possible that schools will be able to afford an electrospinning system at a price far lower than the current market price.

Flexible and thermally conductive epoxy‐dispersed liquid crystal composites filled with functionalized boron nitride nanosheets

AbstractIn view of the problem of heat accumulation in electronic devices, the development of new composites with high thermal conductivity (TC) is the current research focus. Nowadays, improving TC often lead to inevitable deterioration of the mechanical properties of materials. In this work, the E‐functionalized boron nitride nanosheets (f‐BNNS)/liquid crystal monomer (LCM)/Epoxy‐thiol films with high TC were prepared by using flexible epoxy‐thiol polymer as matrix and LCM and f‐BNNS as thermal fillers via high voltage orientation molding. The epoxy‐thiol polymer possessed high intrinsic TC due to the regular arrangement of molecular chains and the f‐BNNS showed favorable dispersibility because of the modification by isopropyl tri(dioctylpyrophosphate) titanate (ITDPT). The results show that TC of E‐f‐BNNS/LCM/Epoxy‐thiol films with 30 wt% f‐BNNS content achieves 1.65 W/m·K and is 511.11% higher than that of pure epoxy‐thiol polymer (0.27 W/m·K). The tensile strength and elongation at break increase to 24.9 MPa and 47.41%, respectively. The favorable results are attributed to the ordered arrangement of f‐BNNS and molecular chains, resulting from the hydrogen‐bonding interaction between OH group in f‐BNNS, LCM and epoxy‐thiol polymer. This research provides a simple and feasible method for preparing flexible epoxy polymer films with high TC.Highlights The functional BNNS was achieved by isopropyl tri(dioctylpyrophosphate) titanate. Effects of matrix thermal conductivity on films thermal conductivity are probed. High voltage orientation molding are used for preparing epoxy composite films. The films demonstrate excellent thermal conductivity and favorable tensile strength.

Atomic-scale observation and prediction of gallium ion implantation induced amorphization on natural diamond surface

Gallium ion implantation is an important solution to modify the physical properties of diamonds, in which the critical condition of gallium ion implantation-induced amorphization of diamond has a crucial influence on the modification effect. Therefore, this work attempts to establish an analytical prediction model of the critical implantation dose for diamond amorphization considering the acceleration voltage, implantation angle and crystal orientation. The prediction accuracy of the model is validated with the electron backscatter diffraction pattern technology. The results show that the model has a satisfactory prediction accuracy when the acceleration voltage is higher. Moreover, the atomic-scale observation of gallium ion implantation-induced amorphization of natural diamonds is realized on a spherical aberration projection electron microscope. The results presented in this work are significant to modify the natural diamond tool for service life improvement with focused ion beams in the future as well as to guide doping diamonds to manufacture n-type semiconductor diamonds.

Categorization of PBTI Mechanisms on 4H-SiC MOSFETs by the Stress Gate Voltage and Channel Plane Orientation

To analyze the mechanism of the positive bias temperature instability (PBTI) of 4H-SiC MOSFETs based on existing models and predict the practical PBTI lifetime in low stress operation, its possible models were classified by the magnitude of the stress gate voltage <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$(V_{GS\_{}stress})$ </tex-math></inline-formula> under high-temperature gate-bias (HTGB) stress and channel plane orientations: Si-face (0001), C-face (000-1), and a-face (11-20). The test samples were vertical MOSFETs with planar surface channels on the Si- or C-face and trench-sidewall channels on the a-face. The measurement-stress-measurement cycles that alternately repeat the HTGB stress and the conventional drain current - gate voltage <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$(I_{D}-V_{GS})$ </tex-math></inline-formula> sweep derived the gate threshold voltage shifts <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$({\Delta }V_{TH}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$t_{s}, sweep$ </tex-math></inline-formula> )) measured after both the stress time <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$(t_{s})$ </tex-math></inline-formula> and the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{TH}$ </tex-math></inline-formula> -shift-recovery with the sweep process. These were more conspicuous on higher <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{GS\_{}stress}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&gt;$ </tex-math></inline-formula> approximately 35, 25, and 30 V for the Si-, C-, and a-faces, respectively) at stress temperature <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$(T_{stress})\,\,=$ </tex-math></inline-formula> 448 K, identified as components trapped in the gate oxide bulk of the Fowler-Nordheim tunneling electrons. For lower <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{GS\_{}stress}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$=$ </tex-math></inline-formula> 15 V), we measured <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\Delta }V_{TH} (t_{s}, t_{r})$ </tex-math></inline-formula> as a function of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$t_{s}$ </tex-math></inline-formula> followed by the relaxation time <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$(t_{r})$ </tex-math></inline-formula> at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{stress}\,\,=$ </tex-math></inline-formula> 293, 448, and 573 K. <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\Delta }V_{TH} (t_{s}, t_{r})$ </tex-math></inline-formula> was analyzed by the capture/emission time (CET) mapping suitable to evaluate the barrier energy beyond which channel electron carriers are (de-)trapped on the MOS interface states. The CET map successfully illustrated the dependence of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\Delta }V_{TH} (t_{s}, t_{r})$ </tex-math></inline-formula> on <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{stress}$ </tex-math></inline-formula> , demonstrating negative or positive correlation owing to shallower or deeper traps, early in the relaxation phase or after long-term <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$t_{s}$ </tex-math></inline-formula> , respectively. This also enabled to estimate the lifetime for a defined allowable limit of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\Delta }V_{TH} (t_{s}, t_{r})$ </tex-math></inline-formula> . When the lifetime is set to about 30 years, the reaching <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\Delta }V_{TH}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$t_{s}, sweep$ </tex-math></inline-formula> ) was calculated to be approximately 70, 150, 350 mV for the Si-, C-, and a-faces, respectively, after <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$t_{s}\,\,=$ </tex-math></inline-formula> 1E9 s <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$(\approx 30$ </tex-math></inline-formula> years) at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{stress}\,\,=$ </tex-math></inline-formula> 448 K on <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{GS\_{}stress}\,\,=$ </tex-math></inline-formula> 15 V.

Flexible epoxy‐dispersed liquid crystal membranes of intrinsic thermal conductivity with high voltage orientation molding

AbstractFlexible epoxy‐dispersed liquid crystal membranes (EDLC‐v membranes) with high thermal conductivity were successfully prepared by using of high voltage orientation molding. Liquid crystal monomer (LCM) was uniformly dispersed into flexible epoxy polymers cured by trimethylolpropane tris(3‐mercaptopropionate) (TTMP) or pentaerythritol tetra(3‐mercaptopropionate) (PETMP). In‐plane thermal conductivity (TC//) of EDLC‐v membranes reached to 1.47 W m−1 K−1 with LCM content of 30 wt%, which was 5.65 times higher than that of epoxy polymers without LCM (0.26 W m−1 K−1). In addition, the tensile strength and elongation at break of EDLC‐v membranes were up to 27.9 MPa and 92.8%, respectively. The main reasons for high TC// and flexibility of EDLC‐v membranes are molecular chains' ordered arrangement, crosslinking in epoxy polymers, hydrogen bond interaction, and high voltage orientation molding. This work provided a new and feasible way to prepare intrinsic high thermal conductive polymer materials, as well as flexible epoxy polymers.

Simulation Analysis and Optimization Design of the Variable-Speed Constant-Frequency Doubly Fed Wind Power Generation Control System Based on PSCAD

The depletion of nonrenewable energy and climate lead to increasingly bad environment. The efficient development of new energy has become an urgent problem to be solved. As a kind of new energy, how to effectively develop and utilize wind energy has aroused widespread concern all over the world. In this paper, a three-phase static a-b-c coordinate system is used for transformation. Taking the variable-speed constant-frequency doubly fed wind power generation system as the control object, the technology of generator power decoupling control is realized. The rotor side and grid side power converters adopt vector control methods based on stator flux orientation and grid voltage orientation, respectively. In this paper, the motion equation, flux equation, voltage equation, and electromagnetic torque equation of the motor are established. Vector-oriented control technology is used to control the generator. The control model of the VSCF doubly fed wind power generation system is established by using the simulation software PSCAD, and the simulation experiment is carried out. The feasibility of the power decoupling control method based on vector control is verified. The change trend of the active power of the power generation system is consistent with that of the wind speed, which shows that the control system has good stability. Using the field-oriented vector control method, the dual PWM controller can independently control the active power and reactive power. This greatly simplifies the nondecoupling control function equation in the expression. The dual PWM controller is well adjusted to minimize the power loss of the wind power generation system.

Voltage Dependence of Nanopattern Morphology and Size in Electropolished Monocrystalline Aluminum: An Experimental Study

The crystallographic orientation dependence of nanopattern morphology and size of electropolished Al at a fixed voltage (40 V) has been revealed and established. However, systematic experimental studies, with samples’ crystallographic orientation exactly determined, on the effects of voltage on nanopattern morphology and size has been largely lacking. Here, miscut monocrystalline Al samples are electropolished in a common electrolyte at voltages 20–60 V. Various nanopatterns (pits, pits plus stripes, stripes, dots) with distinct morphologies emerge with increasing voltage. The findings that morphologies transform gradually with misorientation angle were explained from the perspective of surface structure sensitivity. Nanopattern sizes remain largely constant with misorientation angles but increase with voltages till about 40 V, level off and decrease at higher voltage. A reported model was reexamined to explain the observed voltage dependence of nanopattern size by considering the overlooked effects of voltage on dissolution and adsorption. These findings reveal the voltage and crystallographic orientation dependence of nanopattern morphology and size, and provide critical data for theoretical investigation into the nanopattern formation mechanism of electropolished Al.

Model predictive direct power control of three-level T-type inverter-fed doubly-fed induction generator for wind energy system

The paper proposes a simplified direct power control strategy of a doubly-fed induction generator fed by a three-level T-type inverter based on finite control set model predictive control. A mathematical model based on grid voltage orientation was employed to determine the predictive values of the stator flux, rotor current, and capacitor voltages for all feasible rotor-side inverter output voltages. The active and reactive powers were calculated by using the grid voltage and the rotor current. A cost function was applied to track the active and reactive powers, maintain the balance of capacitor voltages, and reduce the common-mode voltage. The best switching control input was chosen by minimizing the cost function and implemented to the inverter. Different operating conditions of wind turbine systems were studied with Matlab/Simulink environment. The simulation results validate the improved performance of the proposed method compared with the classical control in terms of transient response and steady-state conditions.

A Deep Dive into VDAC1 Conformational Diversity Using All-Atom Simulations Provides New Insights into the Structural Origin of the Closed States.

The voltage-dependent anion channel 1 (VDAC1) is a crucial mitochondrial transporter that controls the flow of ions and respiratory metabolites entering or exiting mitochondria. As a voltage-gated channel, VDAC1 can switch between a high-conducting “open” state and a low-conducting “closed” state emerging at high transmembrane (TM) potentials. Although cell homeostasis depends on channel gating to regulate the transport of ions and metabolites, structural hallmarks characterizing the closed states remain unknown. Here, we performed microsecond accelerated molecular dynamics to highlight a vast region of VDAC1 conformational landscape accessible at typical voltages known to promote closure. Conformers exhibiting durable subconducting properties inherent to closed states were identified. In all cases, the low conductance was due to the particular positioning of an unfolded part of the N-terminus, which obstructed the channel pore. While the N-terminal tail was found to be sensitive to voltage orientation, our models suggest that stable low-conducting states of VDAC1 predominantly take place from disordered events and do not result from the displacement of a voltage sensor or a significant change in the pore. In addition, our results were consistent with conductance jumps observed experimentally and corroborated a recent study describing entropy as a key factor for VDAC gating.

Novel Voltage-Based Weighted Hybrid Force/Position Control for Redundant Robot Manipulators

Existing hybrid force/position control algorithms mostly explicitly contain a dynamic model. Moreover, force and position controllers will be switched frequently. To solve the above problems, a novel voltage-based weighted hybrid force/position control algorithm is proposed for redundant robot manipulators. Firstly, mapping between voltage and terminal position and orientation is established so that the designed controller can be simplified by adopting the motor current as the feedback to replace the tedious calculation of the dynamic model. Secondly, a voltage-based weighted hybrid force/position control algorithm is proposed to eliminate the selection matrix. Force and position control laws are summed directly through a weighted way to avoid the problems of space decomposition and switching. Thirdly, the stability is proven using Lyapunov stability theory, then the selection method for weighted coefficient is provided. Fourthly, comparative simulations are performed. Results show that the proposed algorithm is suitable for impedance control and hybrid force/position control and can compensate for their deficiencies. Lastly, the transport experiment in the YZ plane is conducted. Results show that position and force accuracies in the Y- and Z-axis directions are 3.489 × 10−4 and 7.313 × 10−4 m and 1.238 × 10−1 and 1.997 × 10−1 N, respectively. Accordingly, it can effectively improve the operation capability and control accuracy.

Lyapunov Function Based Flux and Speed Observer Using Advanced Non-linear Backstepping DVC for PWM-Rectifier Connected Wind-turbine-driven PM Generator

In this paper, modeling, and speed/position sensor-less designed Direct Voltage Control (DVC) approach based on the Lyapunov function are studied for three-phase voltage source Space Vector Pulse Width Modulation (SVPWM) Rectifier Connected to a Permanent Magnet Synchronous Generator (PMSG) Variable Speed Wind Power Generation System (VS-WPGS). This control strategy is based on voltage orientation technique without mechanical speed sensor. Advanced Non-linear Integral Backstepping Control (IBSC) of the Generator Side Converter (GSC) has the ability to have a good regulation of the DC link voltage to meet the requirements necessary to achieve optimal system operation, regardless of the disturbances caused by the characteristics of the drive train or some changes into the DC load. The estimation of the speed is based on Model Reference Adaptive System (MRAS) method. This method consists in developing two models one of reference and the other adjustable for the estimation of the two d-q axis components of the stator flux from the measurement of currents, the speed estimated is obtained by canceling the difference between the reference stator flux and the adjustable one using Lyapunov criterion of hyper-stability. Some results of simulation using Matlab/Simulink® are presented, discussed to prove the efficiency and robustness of the system control policy for WPGS against external and internal perturbations.

STEM-EELS investigation of c-Si/a-AlOx interface for solar cell applications

In this article, STEM-EELS methodology is described to investigate the composition of sensitive crystalline Silicon/amorphous aluminum oxide (c-Si/a-AlOx) interface of an a AlOx/amorphous hydrogenated silicon nitride (a-AlOx/a-SiNx:H) passivation stack of a c-Si solar cell. In this stack, a-AlOx has the distinctive characteristic to provide both chemical and field effect passivation, which need further research to be more controlled in order to improve solar cell efficiency. a-AlOx is known to be unstable under the electron-beam, so we first present a detailed study on the electron-beam radiation damage to c-Si/a-AlOx interface. This interface can indeed undergo several electron-beam irradiation damage like sputtering, knock-on or radiolysis if precautions are not taken. Radiolysis damage has been found to be the dominant radiation damage. Thus, several STEM-EELS acquisition parameters like acceleration voltage, electron dose and scan orientation were taken into account and modified to limit this radiolysis damage. Once the irradiation was limited, STEM-EELS investigation was conduct using DualEELS on the Si and Al L2,3 and OK edge fines structures. The interface was found to be composed of a-SiOx and non-stoichiometric aluminum silicate with a predominance of tetrahedrally coordinated Al in its first layer.

Fluoroscopy X-Ray Organ-Specific Dosimetry System (FLUXOR) for Estimation of Organ Doses and Their Uncertainties in the Canadian Fluoroscopy Cohort Study.

As part of ongoing efforts to assess lifespan disease mortality and incidence in 63,715 patients from the Canadian Fluoroscopy Cohort Study (CFCS) who were treated for tuberculosis between 1930 and 1969, we developed a new FLUoroscopy X-ray ORgan-specific dosimetry system (FLUXOR) to estimate radiation doses to various organs and tissues. Approximately 45% of patients received medical procedures accompanied by fluoroscopy, including artificial pneumothorax (air in pleural cavity to collapse of lungs), pneumoperitoneum (air in peritoneal cavity), aspiration of fluid from pleural cavity and gastrointestinal series. In addition, patients received chest radiographs for purposes of diagnosis and monitoring of disease status. FLUXOR utilizes age-, sex- and body size-dependent dose coefficients for fluoroscopy and radiography exams, estimated using radiation transport simulations in up-to-date computational hybrid anthropomorphic phantoms. The phantoms include an updated heart model, and were adjusted to match the estimated mean height and body mass of tuberculosis patients in Canada during the relevant time period. Patient-specific data (machine settings, exposure duration, patient orientation) used during individual fluoroscopy or radiography exams were not recorded. Doses to patients were based on parameter values inferred from interviews with 91 physicians practicing at the time, historical literature, and estimated number of procedures from patient records. FLUXOR uses probability distributions to represent the uncertainty in the unknown true, average value of each dosimetry parameter. Uncertainties were shared across all patients within specific subgroups of the cohort, defined by age at treatment, sex, type of procedure, time period of exams and region (Nova Scotia or other provinces). Monte Carlo techniques were used to propagate uncertainties, by sampling alternative average values for each parameter. Alternative average doses per exam were estimated for patients in each subgroup, with the total average dose per individual determined by the number of exams received. This process was repeated to produce alternative cohort vectors of average organ doses per patient. This article presents estimates of doses to lungs, female breast, active bone marrow and heart wall. Means and 95% confidence intervals (CI) of average organ doses across all 63,715 patients were 320 (160, 560) mGy to lungs, 250 (120, 450) mGy to female breast, 190 (100, 340) mGy to heart wall and 92 (47, 160) mGy to active bone marrow. Approximately 60% of all patients had average doses to the four studied organs of less than 10 mGy, 10% received between 10 and 100 mGy, 25% between 100 and 1,000 mGy, and 5% above 1,000 mGy. Pneumothorax was the medical procedure that accounted for the largest contribution to cohort average doses. The major contributors to uncertainty in estimated doses per procedure for the four organs of interest are the uncertainties in exposure duration, tube voltage, tube output, and patient orientation relative to the X-ray tube, with the uncertainty in exposure duration being most often the dominant source. Uncertainty in patient orientation was important for doses to female breast, and, to a lesser degree, for doses to heart wall. The uncertainty in number of exams was an important contributor to uncertainty for ∼30% of patients. The estimated organ doses and their uncertainties will be used for analyses of incidence and mortality of cancer and non-cancer diseases. The CFCS cohort is an important addition to existing radio-epidemiological cohorts, given the moderate-to-high doses received fractionated over several years, the type of irradiation (external irradiation only), radiation type (X rays only), a balanced combination of both genders and inclusion of people of all ages.

Asynchronized Synchronous Motor-Based More Electric Ship—Less Power Electronics for More System Reliability

Nowadays, the fully power decoupled shipboard power system (SPS) architecture is popular. However, the volume of fragile power electronic converters is large, and the system overload capability is low. In this paper, an asynchronized synchronous motor (ASM)-based SPS is proposed for more-electric ships to handle these issues. The models of the simplified synchronous generator (SSG), ASM, back-to-back converter, and supercapacitor bank are established. Besides, the transfer function of the SSG excitation system is obtained, with the SSG stability analyzed. Moreover, an ASM control strategy based on the emulated stator voltage orientation (ESVO) without the phase-locked loop is proposed to control the ASM. By using the proposed ESVO scheme, the impacts on electric machines are mitigated by the effective SSG stator power control and ASM torque control. High quality of the three-phase voltage and current waveforms can also be obtained. Furthermore, the simulation study is carried out in MATLAB/Simulink to verify the performance of the proposed ASM-SPS. The proposed ESVO scheme and the conventional stator-flux-oriented control strategy are implemented, and the operation of an induction-motor-based SPS with grid voltage orientation is also illustrated for comparison, with frequent propulsion load variations taken into consideration.

Improved Direct Resonant Control for Suppressing Torque Ripple and Reducing Harmonic Current Losses of DFIG-DC System

The most prominent problem of the doubly fed induction generator-dc (DFIG-dc) system is the highly distorted stator voltage due to the diode bridge on stator side. The highly distorted stator voltage not only influences the stator voltage orientation control but also causes harmonic currents and torque ripples. In this paper, an enhanced stator fundamental voltage orientation method is proposed to deal with the highly distorted stator voltage. Furthermore, the relationship between torque ripples and harmonic currents is investigated. And then an improved direct resonant control strategy is proposed for suppressing the torque ripple and reducing the harmonic currents simultaneously. In this way, the loss of harmonic currents can be reduced while suppressing the torque ripple. Finally, the experimental results are presented to validate the effectiveness of the proposed control strategy.

Fuzzy Logic Based Robust DVC Design of PWM Rectifier Connected to a PMSG WECS under wind/load Disturbance Conditions

Permanent Magnet Generator has been widely used in Variable-Speed Wind Energy Conversion System (VSWECS). Fuzzy Logic Control (FLC) of the generator side converter has the ability to have good regulation of the DC-link voltage to meet the requirements necessary to achieve optimal system operation, regardless of the disturbances caused by the characteristics of the drive train or some changes into the DC-load. The main focus of this paper is to present a model for a three-phase voltage source space vector pulse width modulation (SVPWM) rectifier which is connected to a PMSG in a wind turbine system, where a direct voltage control (DVC) using FLC based on voltage orientation strategy is used to control the mentioned rectifier. The control algorithm employs a fuzzy logic controller to effectively achieve a smooth control of DC-link voltage under wind/load perturbation conditions. Some simulation results, using Matlab/Simulink, are presented to show the effectiveness of the SVPWM rectifier Connected to a PMSG WECS with the proposed control strategy.

Addendum of 2MW Wind Turbine to A Power with Directly-Driven Permanent Magnet Generation System

In recent years, wind turbine has become an acceptable alternative energy generation, because of the environmental and economic benefits. Notwithstanding more research works still need to be done to reduce wind turbine installation complexity, enhance profitability and reliability especially in developing countries like Nigeria. This paper presents the modeling and analysis of a 2MW variable-speed directly-driven permanent magnet synchronous generator (PMSG), Wind energy conversion system (WECS). The objective is to optimize the power captured from the wind, ensure optimum efficiency for power generation and reduce system hardware count. The mathematical model for the permanent magnet synchronous wind turbine and its power control algorithms are modified by removing the speed sensors. Further, enhancement was achieved by utilizing wind speed forecasts as the starting speed. A modified Field Orientation Control FOC and voltage orientation control VOC scheme were developed for the system using matlab Simulink CAD application. The Simulation results of the model for various changes in wind speed utilizing average wind speed data of Mmaku in Awgu local government area of Enugu state Nigeria. The developed system ability to ‘smoothen’ the power, voltage output and operates at the optimum coefficient of performance between the cut in speed of 3m/s and 12m/s without wind sensor is found to be promising, Key words : wind turbine, variable-speed, permanent magnet, synchronous generator, efficiency DOI : 10.7176/JETP/9-3-04 Publication date :March 31 st 2019

The Formation Mechanism of Nondefective Silicon Micropatterns Fabricated by Scratching Assisted Electrochemical Etching

Fabrication of nondefective silicon microstructures at specific region is of great importance but challenging, which is promising to boost the performance of microsensors, micro energy storage devices, and microfluidic devices. A low-cost approach to fabricate nondefective silicon microstructures based on scratching assisted electrochemical etching has been proposed. Shallow patterns together with silicon amorphous and defects layer were scratched by the diamond tip. The scratched area was utilized as sacrificial layer in the electrochemical etching process and removed rapidly. The introduction of electrochemical etching would change the distribution of holes in the groove area and substrate, thus the formation and morphology of the nondefective silicon structures are different. The influences of etching voltage, scratching load, etching duration, resistivity and crystal orientation of substrates on the silicon microstructures were discussed systematically. The depth, width and cross section shape of the silicon microstructures change with etching duration, voltage polarity and resistivity. But the crystal orientation has little effect on the width and depth of silicon microstructures. Nondefective silicon microstructures array with different pitch and height can be fabricated in specific location by the scratch assisted electrochemical etching approach, which can be used in high performance micro devices.

Engineering modelling of wind turbine applied in real‐time simulation with hardware‐in‐loop and optimising control

In order to constantly improve the output characteristics of wind turbines, the HIL (Hardware In the Loop) experimental platform of wind turbines is built to optimize control. According to the product parameters of 1.5 MW direct-drive PMSG (Permanent Magnet Synchronous wind Generator) of Dongfang Electric Corporation (DEC), the simulation model of wind turbine is built in RTDS (Real Time Digital Simulator), and optimised by comparing with the wind speed–power curve of products, the simulation model of wind turbine with engineering accuracy can be obtained. Base on the engineering model and actual controller of products, the HIL experimental platform of wind turbines is built to optimise control. In the case of unbalanced or asymmetrical grid voltage, in order to make the wind turbine output be stable, the DDSOGI-PLL (direct Decoupling Double Second-Order Generalized Integral Phase-Locked Loop) is proposed to improve the performance of PLL, the active/reactive current decoupling algorithm based on positive and negative sequence voltage orientation respectively is proposed to eliminate the negative sequence current to maintain a constant output power. The effectiveness of algorithm is verified by the HIL experimental platform, the active power output of wind turbine remains constant, the grid-connected adaptability of wind turbines is improved significantly.

Status of the R&amp;D activities for the upgrade of the ALICE TPC

After the Long Shutdown 2 (LS2) the LHC will provide lead–lead collisions at interaction rates as high as 50 kHz. In order to cope with such conditions the ALICE Time Projection Chamber (TPC) needs to be upgraded. After the upgrade the TPC will run in a continuous mode, without any degradation of the momentum and dE/dx resolution compared to the performance of the present TPC. Since readout by multi-wire proportional chambers is no longer feasible with these requirements, new technologies have to be employed. In the new readout chambers the electron amplification is provided by a stack of four Gas ElectronMultiplier (GEM) foils. Here foils with a standard hole pitch of 140 μm as well as large pitch foils (280 μm) are used. Their high voltage settings and orientation have been optimised to provide an energy resolution of σE/E ≤ 12% at the photopeak of 55Fe. At the same settings the Ion BackFlow into the drift volume is less than 1% of the effective number of ions produced during gas amplification and the primary ionisations. This is necessary to prevent the accumulation of space charge, which eventually will distort the field in the drift volume. To ensure stable operation at the high loads during LHC run 3 the chambers have to be robust against discharges, too. With the selected configuration in a quadruple GEMstack the discharge probability is kept at the level of 10-12 discharges per incoming hadron. An overview of the ALICE TPC upgrade activities will be given in these proceedings and the optimised settings foreseen for the GEM stacks of the future readout chambers are introduced. Furthermore the outcome of two beam time campaigns at SPS and PS (at CERN) in the end of 2014 is shown. At this campaigns the stability against discharges and the dE/dx performance of a full size readout chamber prototype was tested. In addition it is reported on charging-up studies of 4GEM stacks and on tests of electromagnetic sagging of large GEM foils.