Advanced Angle Research Articles

7상 BLDC 전동기의 고속운전 영역 확장을 위하여 안티 와인드업 출력 전압과 전압 방정식을 이용한 자동 진상각 제어 알고리즘

7상 BLDC 전동기의 고속운전 영역 확장을 위하여 안티 와인드업 출력 전압과 전압 방정식을 이용한 자동 진상각 제어 알고리즘

Comparative Study of Different Pitch Angle Control Strategies for DFIG Based on Wind Energy Conversion System

Abstract- This paper presents an advanced pitch angle control for large scale Wind Energy Conversion System (WECS) based on a Doubly-Fed Induction Generator (DFIG). Blade Pitch angle control is the extremely popular techniques for regulating the aerodynamic power of the wind turbine and minimize aerodynamic fatigue when the wind speed is higher than its rated value. The traditional control technique is based on the proper system modeling and analytical analysis of the transfer function which are not always available and the non-linearity of the control system. To overcome the problems in the traditional control, the adaptive fuzzy-PID control is proposed in this work. The process of the blade pitch control using adaptive fuzzy-PID control strategy is featured with nonlinearity, multi-variable, time variation and time delay. The simulation results are enclosed which prove the effectiveness of the auto-tuning adaptive fuzzy-PID (AF-PID) controller in improving the dynamic performance of the wind turbine (WT). This article emulated comparative analysis of 1.5 MW Doubly-fed induction generator wind turbine control strategies based on computer modeling in MATLAB/Simulink software.

Intraocular pressure reduction in a spectrum of angle closure disease following cataract extraction.

Purpose:The purpose is to study the effect of cataract extraction on intraocular pressure (IOP) in patients with angle closure disease (ACD).Methods:In this retrospective study, patients with ACD including medically uncontrolled and advanced primary angle closure glaucoma (PACG) who underwent only cataract surgery were included. The IOP trend was analyzed at postoperative day 1, day 7, 1 month, 3 months, 6 months, 1 year, and final follow-up along with requirement of antiglaucoma medication (AGM)/surgery.Results:A total of 110 eyes of 79 patients [primary angle closure suspect (PACS): 21, PAC: 34, PACG: 55 eyes] were analyzed. Of these patients, 31 eyes had advanced PACG and 20 eyes had medically uncontrolled glaucoma. Best-corrected visual acuity >6/12 was seen in 51 eyes at baseline and 87 eyes at final follow-up. After cataract surgery alone, there was significant reduction (median) in IOP [19.1 ± 18.00% (18.8) in PACS (P < 0.01), 8.55 ± 17.9% (10) in PAC (P = 0.04), 22.82 ± 15.45%(14.3) in PACG (P < 0.01), 18.27 ± 15.99% (14.5) in advanced PACG (P = 0.01) and 36.56 ± 14.58% (28.57) in medically uncontrolled glaucoma (P < 0.01)] and AGM [51.85% (1) in PAC, 32.35% (2) in PACG, 17.71% (2) in advanced PACG, and 40.74% (1.5) in medically uncontrolled PACD] at median follow-up of 1, 2.5, 1, 1.3, and 1 year. Eleven PACG patients, who were on systemic medication preoperatively, were off systemic therapy at final follow-up, while six other PACG eyes (10.9%) required glaucoma surgery.Conclusion:Cataract surgery leads to significant drop in IOP across the spectrum of ACD with visually significant cataract. Cataract surgery may be considered initially for IOP control even in advanced or medically uncontrolled PACG followed by glaucoma surgery later if required.

Investigation of a Fault-Tolerant Control Method for a Multiport Dual-Stator Doubly Salient Electromagnetic Machine Drive

A novel fault-tolerant inverter topology of the multiport dual-stator doubly salient electromagnetic machine (MDDSEM) drive is proposed in this paper for high reliability applications such as automotive and aerospace industries. The proposed topology adopts four diverter switches to reconnect the floating phase windings under the fault conditions and reconfigures the dual inverter to be a five-leg inverter; the output performance could be maintained after a single-phase open-circuit or short-circuit fault of the dual inverter. Compared with the traditional fault-tolerant method of the dual inverter for the MDDSEM, the lower cost and smaller volume of the proposed fault-tolerant system can be achieved. The operation principle and the optimized commutation method of the five-leg inverter for the MDDSEM are analyzed to eliminate the unexpected phase current drop so that the torque performance in the fault-tolerant mode could be improved. The effectiveness and feasibility of the proposed fault-tolerant topology and control strategies are verified by the simulation and experimental results of a 24/16-pole MDDSEM that includes both steady-state and dynamic processes with the standard angle control method and the advanced angle control method.

Improper Technique of Eye Drop Instillation Leading to Corneal Ulcer in a Visually Impaired Glaucoma Patient

We report a case of visually impaired glaucoma patient with long term use of topical glaucoma medications presented with a corneal ulcer due to the improper technique of eye drop instillation. A 70-year-old gentleman with advanced primary open angle glaucoma (POAG) on his right eye and absolute glaucoma on his left eye, presented with painful redness and purulent discharge of the right eye for two weeks. He was using four types of topical glaucoma medication on his right eye since failed trabeculectomy two years ago. His right eye vision was 6/24 and painless blindness of the left eye before the presentation. He was administering all the medications himself despite his current vision status. Right eye examination showed visual acuity of 3/60 with clinical features of corneal ulcer. During the observation of his eye drop instillation technique, he consistently touched the tip of the bottle to his right cornea. The corneal contact area corresponded to the corneal ulcer area and size. In addition to this, the culture result obtained from both corneal ulcer and the bottles’ tips yielded similar microorganism which was Staphylococcus aureus. After an intensive course of topical antibiotics treatment, the corneal ulcer healed with a scar and the vision improved to 6/24 from 3/60. Although this incident is rare, it is crucial for the treating physicians to address the issue properly and co-manage these patients with pharmacists and nursing staffs as well as to seek support from the caretakers to prevent this blinding complication. KEYWORDS: corneal ulcer, glaucoma medication, eye drop instillation technique

Evaluation of episcleral venous fluid wave during gonioscopy assisted transluminal trabeculotomy in patients with advanced glaucoma.

To evaluate episcleral venous fluid wave (EVFW) during GATT surgery in patients with advanced stage open angle glaucoma and to investigate its relationship with the severity of glaucoma. In all, 34 eyes of 28 open angle glaucoma patients who underwent GATT surgery were included into study. The extent of EVFW was evaluated using surgical records of patients and it was defined as number of clock hours. Correlations between the extent of EVFW and GAAT surgical outcomes as determined by intraocular pressures (IOP) and postoperative antiglaucoma medication needs were investigated. The impact of preoperative maximum IOP on EVFW was also evaluated. There was a significant correlation between IOPs and the extent of the EVFW at 1st, 3rd, 6th and 12th months follow-up visits. 10 of (%29.4) 34 eyes required antiglaucoma medications after the surgery. Mean extents of EVFW in patients who needed and did not need medications during follow-ups were 2.6 ± 1.0 (1-4) and 5.9 ± 1.5 (3-8) clock hours and the difference was statistically significant. Cutoff value of <4.5 clock hours for the EVFW (sensitivity 79.2%, specifity 100%) was found to be associated with the need for additional antiglaucoma medication. The extent of EVFW might be a valuable prognostic indicator for the surgical success of GATT since trabeculotomy is circumferential in this surgical technique making all collector channels accessible.

Review on the techno‐commercial aspects of wind energy conversion system

This study provides an overview of the different techno-commercial aspects of a wind energy conversion system. The review includes the grid codes provided by the transmission system operator of different countries supplemented by various communication protocols, explanation of different types of conventional and advanced wind generators, discussions on different maximum power point algorithms along with various conventional and advanced pitch angle control systems. The study also describes a variable speed system using different types of power electronic converters at the generator and the grid side to maintain power quality, grid synchronisation and unity power factor operation along with various cooling techniques utilised. In a subsequent part, a clear overview of different control topologies such as field-oriented control, direct torque control, voltage-oriented control and direct power control has been provided along with the recent advancement of each and every topology. The study also provides the challenges of the prevailing technology along with the already available and possible ways of minimising these technological gaps. Finally, a techno-commercial comparison of different commercially available wind systems by different companies has been presented along with their market share based on the current scenario.

Accuracy of peripapillary versus macular vessel density in diagnosis of early to advanced primary open angle glaucoma

To evaluate macular and peripapillary vessel density (mVD, pVD) using optical coherence tomography angiography (OCT-A) in healthy subjects, patients with ocular hypertension (OHT) and primary open-angle glaucoma (POAG) patients. In this prospective observational study, OCT-A images were obtained from 60 eyes of 36 healthy, ocular hypertension (OHT), preperimetric glaucoma (PPG), early glaucoma (EG) and moderate and advanced POAG subjects. Superficial mVD was acquired over a 6×6-mm cube centered on the foveal avascular zone and pVD over a 4.5×4.5-mm cube centered on the optic disc. Peripapillary retinal nerve fiber layer (pRNFL) and ganglion cell complex (GCC) thickness was calculated using spectral-domain OCT. Correlations between vascular, structural and Humphrey VF indices were evaluated (Spearman's rank correlation coefficient). Median pVD and mVD in the PPG eyes were lower than in healthy eyes (51.87% and 47.23% versus 55.70% and 53.61%, respectively; P<0.001 and P=0.003), but higher than in mild glaucoma eyes (46.21% and 41.98%, P<0.001 compared to normal eyes) and moderate to advanced glaucoma eyes (37.45% and 39.89%, P<0.0001 compared to normal eyes). The highest correlations were found between structural parameters and pVD (r=0.87 and 0.86 for pRNFL and GCC, P<0.0001), followed by mVD (r=0.69 for both pRNFL and GCC, P<0.0001). Correlations with mean VF sensitivity were similar for pVD and mVD (r=0.61 and 0.56) and for GCC and pRNFL (r=0.60 and 0.52, P<0.0001 for all). VD measured with OCT-A shows reduction in POAG. Detection of this damage differentiates PPG from normal and perimetric POAG eyes with a high correlation with structural parameters. Peripapillary VD accuracy is higher than mVD in detecting the disease. These results suggest that OCT-A could improve POAG diagnosis and understanding of the pathophysiologic mechanisms behind glaucoma.

High precision (Advanced) angle metrology: pushing the limits for nanoradian uncertainty demands

Precise angle measuring devices – such as angle encoders, angle interferometers, small angle generators and autocollimators – are extensively used in various applications where high precision is demanded. Recently, an angle metrology project supported under European Metrology Research Programme (EMRP) has been completed. This project has made a significant contribution to traceable angle metrology targeting at nanoradian uncertainty (less than 50 nrad) for stringent demands and achieved milestones. It has provided novel methods, tools, instruments, guides and knowledge that will help to ensure use of precise angle metrology equipment for the demands which have not been answered before. Some of the new devices are already commercially available and have been started to be used for critical needs. This paper gives highlights of the project’s outputs and inform the community about recent developments in high precision advanced angle metrology.

Impaired Photic Entrainment of Spontaneous Locomotor Activity in Mice Overexpressing Human Mutant α-Synuclein.

Parkinson’s disease (PD) is characterized by distinct motor and non-motor symptoms. Sleep disorders are the most frequent and challenging non-motor symptoms in PD patients, and there is growing evidence that they are a consequence of disruptions within the circadian system. PD is characterized by a progressive degeneration of the dorsal vagal nucleus and midbrain dopaminergic neurons together with an imbalance of many other neurotransmitters. Mutations in α-synuclein (SNCA), a protein modulating SNARE complex-dependent neurotransmission, trigger dominantly inherited PD variants and sporadic cases of PD. The A53T SNCA missense mutation is associated with an autosomal dominant early-onset familial PD. To test whether this missense mutation affects the circadian system, we analyzed the spontaneous locomotor behavior of non-transgenic wildtype mice and transgenic mice overexpressing mutant human A53T α-synuclein (A53T). The mice were subjected to entrained- and free-running conditions as well as to experimental jet lag. Furthermore, the vesicular glutamate transporter 2 (VGLUT2) in the suprachiasmatic nucleus (SCN) was analyzed by immunohistochemistry. Free-running circadian rhythm and, thus, circadian rhythm generation, were not affected in A53T mice. A53T mice entrained to the light–dark cycle, however, with an advanced phase angle of 2.65 ± 0.5 h before lights off. Moreover, re-entrainment after experimental jet lag was impaired in A53T mice. Finally, VGLUT2 immunoreaction was reduced in the SCN of A53T mice. These data suggest an impaired light entrainment of the circadian system in A53T mice.

Investigations of interpolation errors of angle encoders for high precision angle metrology

Interpolation errors at small angular scales are caused by the subdivision of the angular interval between adjacent grating lines into smaller intervals when radial gratings are used in angle encoders. They are often a major error source in precision angle metrology and better approaches for determining them at low levels of uncertainty are needed. Extensive investigations of interpolation errors of different angle encoders with various interpolators and interpolation schemes were carried out by adapting the shearing method to the calibration of autocollimators with angle encoders. The results of the laboratories with advanced angle metrology capabilities are presented which were acquired by the use of four different high precision angle encoders/interpolators/rotary tables. State of the art uncertainties down to 1 milliarcsec (5 nrad) were achieved for the determination of the interpolation errors using the shearing method which provides simultaneous access to the angle deviations of the autocollimator and of the angle encoder. Compared to the calibration and measurement capabilities (CMC) of the participants for autocollimators, the use of the shearing technique represents a substantial improvement in the uncertainty by a factor of up to 5 in addition to the precise determination of interpolation errors or their residuals (when compensated). A discussion of the results is carried out in conjunction with the equipment used.

GPS Synchronization of Smart Distributed Converters for Microgrid Applications

In this paper, a smart distributed DC/DC converter synchronization advanced technique and phase angle optimization algorithm are proposed using to reduce the DC bus overall ripple. A global positioning system-based scheme is used to synchronize the carrier among the distributed converters. The carrier phase angle optimization among the different converters is inspired by Carrier-Sense Multiple Access protocol. The proposed system is simulated and analyzed using Matlab/Simulink program. As a proof of concept of the proposed technique, two case studies have been investigated under equal and unequal load sharing among the distributed generators. The proposed algorithm shows a significant reduction in the DC bus voltage ripple. To prove the concept, a laboratory test-bed has been built and the proposed algorithm has been implemented to validate the theoretical and simulation results. The close agreement between the experimental and simulation results demonstrates the effectiveness and validity of the proposed algorithm.

A Two-Zone Combustion Model for Knocking Prediction of Marine Natural Gas SI Engines

The further thermal efficiency improvement of marine natural gas engine is constrained by a knocking phenomenon that commonly occurs in gas-fueled spark-ignited engines. It plays an important role to investigate how the knocking occurs and how to predict it based on the engine simulation model. In this paper, a two-zone model is developed to provide the prediction of knocking performance and NO emission, which is verified by engine test bed data from a transformed marine natural gas spark ignition (SI) engine. Cylindrical division theory is used to describe the shape of the two zones to decrease the computational cost, as well as a basic mechanism for NO concentration calculation. In order to solve the volume balance, three boundary parameters are introduced to determine the initial condition and mass flow between the two zones. Furthermore, boundary parameters’ variation and knocking factor (compression ratio and advanced ignition angle) will be discussed under different working conditions. Result shows that the two-zone model has sufficient accuracy in predicting engine performance, NO emission and knocking performance. Both the increasing compression ratio and advanced ignition angle have a promoting effect on knocking probability, knocking timing and knocking intensity. The knocking phenomenon can be avoided in the targeted natural gas SI engine by constraining the compression ratio smaller than 14 and advanced ignition angle later than 30° before top dead center (BTDC).

Novel Detection Method for Consecutive DC Commutation Failure Based on Daubechies Wavelet with 2nd-Order Vanishing Moments

Accurate detection and effective control strategy of commutation failure (CF) of high voltage direct current (HVDC) are of great significance for keeping the safe and stable operations of the hybrid power grid. At first, a novel detection method for consecutive CF is proposed. Concretely, the 2nd and higher orders’ derivative values of direct current are summarized as the core to judge CF by analyzing the physical characteristics of the direct current waveform of the converter station in CF. Then, the Daubechies wavelet coefficient that can represent the 2nd and higher order derivative values of direct current is derived. Once the wavelet coefficients of the sampling points are detected to exceed the threshold, the occurrence of CF is confirmed. Furthermore, by instantly increasing advanced firing angle β in the inverter side, an additional emergency control strategy to prevent subsequent CF is proposed. Eventually, with simulations of the benchmark model, the effectiveness and superiorities of the proposed detection method and additional control strategy in accuracy and rapidity are verified.

Composite material characterisation using an advanced small angle x-ray (SAXS) technique

Materials development in the field of composite material spurs the use of advanced characterization technique. As the fillers become in the nanoscale range in size, the effect of agglomeration become apparent and cannot be avoided. The use of Small Angle X-Ray (SAXS) Scattering technique revealed the information on agglomeration based on the value of specific surface (m2/g). Thermoplastic natural rubber composite was found isotropic based on 2D saxs scattering pattern. As the amount of fillers increased from 2-10% wt., the value of specific surface dropped accordingly. This indicated the higher the amount of filler used, the higher the degree of agglomeration. The SAXS system was also tested by Alumina (BAM) powder and yield result which was in good agreement with BET technique.

Optimal capacity of energy storage for dynamic voltage restorer under electrical faults scenarios using SOS optimization algorithm: Case of south Algerian’s electrical autonomous grid application

In the last decade, one of the Algeria’s preoccupations is the power quality through its national electrical network such as voltage sags and swells, harmonic currents and voltages. The customers connected to the power distribution network suffer from these perturbations, to solve this problem custom power device is used which is called dynamic voltage restorer. This paper describes DVR principle and voltage restoration which will be connected to the 15KV real autonomous networks in small village of south Algeria. Moreover, optimal energy capacity for the proposed devices based on Meta heuristic methods is presented. The dynamic voltage restorer (DVR) has newly established to protect the industrial facilities from voltage sags and other voltage disturbances. The compensation ability of DVR depends primarily on the maximum voltage injection aptitude and the amount of stored available within the restorer. A detailed procedure to design the optimal system is presented by using SOS algorithm based Advancement compensation (PAC) policy in order to improve the voltage property of the device. The planed approach employs Symbiotic Organism Search technique to search for optimal value of phase advancement angle equivalent to minimum power injection from the energy storage element such as a capacitor or battery and its results have been compared to the conventional DVR techniques. According to the achieved results and detailed analysis, The corresponding values of optimized energy are 13,278W-h, 20.847W-h and optimums phase advanced angles found 131.762°, 115.536° for 17% and 40% voltage sag happened through electrical distribution network. Finally, the proposed method has been compared with other methods available in the literature and is found effective and encouraging.

Online Advanced Angle Adjustment Method for Sinusoidal BLDC Motors with Misaligned Hall Sensors

This letter presents an improved approach for high performance operation of brushless dc (BLDC) motors with hall sensors. The hall sensors in BLDC motors are ideally placed 120 electrical degrees apart. However, hall sensor placement may be significantly incorrect, particularly in high-pole and small-sized motors. These misaligned hall sensors can cause serious torque ripple, and it can be difficult to apply advanced angle control. Therefore, a position error compensator is needed before an advanced angle control method is applied. In this letter, on the basis of the position error compensator, an online advanced angle adjustment method using input voltage and input current is proposed. Using the proposed method, balanced hall sensor signals can be obtained and the high-performance operation can be achieved. The effectiveness of the proposed approach is verified through experimental results.

Circadian Alterations in a Murine Model of Hypothalamic Glioma.

The mammalian circadian system is controlled by a central oscillator located in the suprachiasmatic nuclei (SCN) of the hypothalamus, in which glia appears to play a prominent role. Gliomas originate from glial cells and are the primary brain tumors with the highest incidence and mortality. Optic pathway/hypothalamic gliomas account for 4–7% of all pediatric intracranial tumors. Given the anatomical location, which compromises both the circadian pacemaker and its photic input pathway, we decided to study whether the presence of gliomas in the hypothalamic region could alter circadian behavioral outputs. Athymic nude mice implanted with LN229 human glioma cells showed an increase in the endogenous period of the circadian clock, which was also less robust in terms of sustaining the free running period throughout 2 weeks of screening. We also found that implanted mice showed a slower resynchronization rate after an abrupt 6 h advance of the light-dark (LD) cycle, advanced phase angle, and a decreased direct effect of light in general activity (masking), indicating that hypothalamic tumors could also affect photic sensitivity of the circadian clock. Our work suggests that hypothalamic gliomas have a clear impact both on the endogenous pacemaking of the circadian system, as well as on the photic synchronization of the clock. These findings strongly suggest that the observation of altered circadian parameters in patients might be of relevance for glioma diagnosis.

Monitor local structure variation of Ce3+ activator in YAG:Ce nanophosphor with calcination temperature by nuclear magnetic resonance spectroscopy

Understanding the intrinsic relationship between photoluminescence (PL) properties and fine crystal structure is essential for developing excellent cerium doped Y3Al5O12 (YAG:Ce) nanophosphors. Herein, we studied the crystal structure evolution of YAG:Ce nanophosphors with calcination temperature via multiple characterization techniques, and focused on clarifying the local structure of Ce3+ activator by advanced quantitative 27Al magic angle spinning nuclear magnetic resonance (27Al MAS NMR) spectroscopy. The results showed that the crystallinity of the YAG:Ce nanophosphors was improved and the lattice constant monotonously decreased with rising calcination temperature. Especially, as the calcination temperature increased from 830 to 1030 °C, more Ce3+ ions entered the first sphere of AlO6 groups and the symmetry of AlO4 species gradually increased in YAG:Ce nanophosphors, which caused the decrease of geometrical distortion surrounding Ce3+ activators. Due to the variations of fine structure, the PL intensity obviously increased with calcination temperature while its position remained constant. When the calcination temperature further increased to 1080 °C, CeO2 impurity formed in the nanophosphor, resulting in the increase of the quenching centers.

Research on control strategies for doubly salient electromagnetic machine

The doubly salient electromagnetic machine (DSEM) is a kind of variable reluctance machine, which is different from the conventional AC electric machines. The standard angle control and the three-state angle-advanced control are traditional control strategies for DSEM, with dead zone existing. Six-SAA (SSAA) control is a newly proposed control strategy with no dead zone. Compared to traditional control strategies, it can increase output torque, and reduce the torque ripple. However, it is hard to select proper advanced angles in SSAA control. In this study, a 12/8-pole DSEM has been studied. Then, several control strategies for DSEM are presented, and the operating principles are analysed in detail. After that, a new control strategy is proposed, and its characteristic during commutation stage is analysed. Besides, the optimal advanced angles are deduced, with its variation characteristics, and the comparison of these control strategies are conducted by finite element simulation. With the proposed control strategy, a higher-output torque can be acquired in a wide-speed range, and meanwhile, the selection of advanced angles is simplified. Finally, the theoretical analysis is verified by simulations and experimental results.