bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adaptive step size based drift‐free P&O algorithm with power optimiser and load protection for maximum power extraction from PV panels in stand‐alone applications
Authors: Gopahanal Manjunath Madhu , Vyjayanthi Chintamani , Modi Chirag N. 
Published: February 2021

AbstractThis paper presents an adaptive step size based drift‐free perturb and observe algorithm with power optimiser and load protection for maximum power extraction from photovoltaic panels in stand‐alone applications. The proposed algorithm consists of an adaptive step‐size technique, drift mitigation technique and power optimiser and load protection technique for fast maximum power extraction with less steady‐state power loss and protection features. The adaptive step‐size technique continuously monitors the absolute value of change in power () to adjust the perturbation step size () for fast tracking of maximum power point, and the drift mitigation technique mitigates the confusion in selecting the correct perturbation direction that exists in the conventional perturb and observe algorithm for a sudden change in irradiance conditions. Besides, the presented power optimiser and load protection uses a closed‐loop duty cycle (D) value for detecting possible underloading and overloading conditions, wherein, in case of underloading or overloading, it turns off the power optimiser to protect itself and the connected load from any damage or malfunctioning. The overall performance of the proposed algorithm, in terms of its dynamic operations, reduced steady‐state power loss, and protection features are evaluated using MATLAB simulations and verified with an experimental prototype. Comparative analysis of the proposed algorithm with state‐of‐the‐art perturb and observe techniques is carried out for validating its effectiveness and feasibility in real‐time applications.
VSC‐HVDC system‐based on model predictive control integrated with offshore wind farms
Authors: Sultan Yara A. , Kaddah Sahar S. , Eladl Abdelfattah A. 
Published: February 2021

AbstractRecently, the offshore wind farms (OWFs) have excellent potential in global power networks. So, the demand for high power and high‐quality transmission system is becoming more pressing with the fast growth of OWFs. A promising solution is provided by the voltage source converter‐high voltage direct current (VSC‐HVDC) system. This paper proposes a control method for controlling the VSC‐HVDC system to integrate OWFs into power grids based on model predictive control (MPC). To minimise the distortion and filtering of the harmonics injected into the utility grid, the receiving end converter of the VSC‐HVDC system is connected with LCL filter. The proposed control strategy maintains active/reactive power‐sharing with efficient regulation of AC voltage among the different OWFs operation conditions. The detailed system components modelling and simulation are executed in the MATLAB/Simulink environment, which is used to perform both dynamics and transient evaluation of the suggested control strategy. The acquired simulation results emphasize the capability of the proposed control strategy to maintain system stability under different operation conditions compared to the synchronous reference frame‐based current limiting droop control method (SRF‐based CLD).
Design and modelling of self‐excited SRG and FM‐SRG for wind energy generation
Authors: Tefera Kitaba , Tripathy Praveen , Adda Ravindranath 
Published: February 2021

AbstractThe paper discusses the design and analysis of synchronous reluctance generator with a rating of 2.1 kW. These generators with low power ratings may be a suitable candidate for the rural electrification. In synchronous reluctance generator, the design of the rotor is the most challenging part of the design. Here, the thickness of the axial and tangential ribs plays a significant role in its performance. The design procedure presented in the paper includes the effect of stator resistance, as it cannot be neglected in the design of synchronous reluctance generator with low power ratings. The paper discusses the design procedure of synchronous reluctance generator and analyses the self‐excited ferrite‐magnet synchronous reluctance generator. Various parameters of the designed machine are analysed through an analytical model and Ansys Electronics Desktop software. Further, the paper also includes the experimental validation of the synchronous reluctance generator results obtained through finite element analysis. The paper also proposes formulae to approximate the minimum values of the excitation capacitor requirement, for a self‐excitation of synchronous reluctance generator with inductive load.
Modern electric machines and drives for wind power generation: A review of opportunities and challenges
Authors: Chen Hao , Zuo Yuefei , Chau K. T. , Zhao Wenxiang , Lee Christopher H. T. 
Published: February 2021

AbstractWith ever‐increasing concerns on energy crisis and environmental protection, there is a fast‐growing interest in wind power generation systems. As electric machines and drives are core components in wind turbines, it is a pressing need for researchers and engineers to develop advanced electric machines and drives for wind power generation. This paper provides a thorough review of modern electric machines and drives for wind power generation, with emphasis on machine topologies, operation principles, performance characteristics, as well as control strategies. The key features of electric machines and drives including their merits and demerits, e.g. torque/power density, efficiency, and cost, are compared and summarised. Trade‐offs involved in various presented methods and strategies are highlighted. The major challenges and difficulties, which electric machines and drives for wind power generation are facing, are discussed. Moreover, the developing trends and opportunities are revealed, while the latest development is also discussed.
Piezoelectric energy harvester converting wind aerodynamic energy into electrical energy for microelectronic application
Authors: R Sitharthan , S Yuvaraj , Padmanabhan Sanjeevikumar , Holm‐Nielsen Jens Bo , M Sujith , M Rajesh , N Prabaharan , K vengatesan 
Published: February 2021

AbstractPiezoelectric Energy Harvesting Systems play a vital role in energizing microelectronic devices with the low‐frequency operation. Here, a novel piezoelectric energy harvesting device has been developed for low power electronic devices. The developed Piezoelectric Energy Harvesting Systems consists of a cantilever with poles projecting outwards and the cantilevers one end is connected to the wind‐catcher, and another end is connected to the torsional spring. The developed Piezoelectric Energy Harvesting Systems signifies its application in energizing microelectronic devices. The cantilever is placed inwards to the piezoelectric crystal stack. When the wind strikes, a vortex is created in the windcatcher, which oscillates the cantilever and generates stress in the piezoelectric crystal stack to develop electric energy. The output voltage obtained from the Piezoelectric Energy Harvesting Systems does not affect any input frequency of the piezoelectric crystal. The result obtained shows that the developed Piezoelectric Energy Harvesting Systems generates 120–200 eV with 2.9 × 1016–4.84 × 1016 Hz frequency considering an elementary charge unit as 40 for a variable wind flow of 4–9 m/s. This research aims to develop an efficient wind‐based Piezoelectric Energy Harvesting Systems for low powered microelectronic devices.
Deadbeat direct power control for dual three‐phase PMSG used in wind turbines
Authors: Jin Shibo , Zhao Wenxiang , Ji Jinghua , Xu Dezhi 
Published: February 2021

AbstractThe classical switching‐table‐based direct power control usually employs one active voltage vector during the whole sample period, which will bring distinct current harmonics and large power ripple. This paper proposes an improved deadbeat direct power control for a dual three‐phase permanent magnet synchronous generator. The deadbeat control of both active power and reactive power is employed to calculate the duty cycle of the active vector. By this way, the active and reactive power can follow the references as much as possible during each sample period. Then a weight coefficient is introduced and its effects on the steady‐state performances of active and reactive power are analysed. With this proposed method, the current harmonics and power ripple are suppressed considerably. Meanwhile, the simple structure and fast dynamic response are preserved. The experimental results validate the effectiveness of the proposed strategy.
Sensorless MRAS control of emerging doubly‐fed reluctance wind generators
Authors: Agha‐Kashkooli Mohammad‐Reza , Jovanović Milutin 
Published: February 2021

AbstractA new model reference adaptive system based estimation technique for vector control of real and reactive power of a brushless doubly fed reluctance generator without a shaft position sensor is proposed. The rotor speed is being precisely observed in a closed‐loop manner by eliminating the error between the measured and estimated inverter‐fed (secondary) winding current angles in a stationary frame. Contrary to the existing model reference adaptive system observer designs reported in the brushless doubly fed reluctance generator literature, the reference model is entirely parameter‐free and only utilises direct measurements of the secondary currents. Furthermore, the current estimates coming from the adaptive model are obtained using the measured voltages and currents of the grid‐connected (primary) winding, which has provided prospects for much higher accuracy and superior overall performance. The realistic simulations, preliminary experimental results, and the accompanying parameter sensitivity studies have shown the great controller potential for typical operating conditions of variable speed wind turbines with maximum power point tracking.
A new soft‐switching multi‐input quasi‐Z‐source converter for hybrid sources systems
Authors: Torki Harchegani Amir , Asghari Amin , Jazaeri Mostafa 
Published: February 2021

AbstractThis study focuses on a zero voltage transition multi‐input quasi‐Z‐source converter (qZSC). This topology can be used for input sources with different voltages and currents to provide a constant output voltage. In the proposed structure, several qZSCs are combined and the output filter of all stages is eliminated. Therefore, the overall number of circuit elements, cost, volume and weight are reduced in comparison with when they are in a separate operation. In this converter, the soft‐switching conditions are provided for all stages by using only one auxiliary circuit. The employed technique provides zero‐voltage zero‐current switching (ZVZCS) and zero‐voltage switching for main switches at turn‐on and turn‐off instants, respectively. The auxiliary switch turns on under zero‐current switching and turns off under ZVZCS. Furthermore, the reverse recovery losses of diodes are reduced. The theoretical foundation of the proposed converter is presented and its performance is simulated by OrCAD software. The obtained results show 3.5% improvement in the efficiency at nominal loads, compared to its hard‐switching counterpart. A dual‐input prototype of the proposed structure is successfully built to support the validity of the theoretical analysis.
Multiple extended stealth target tracking from image observation based on non‐linear sub‐random matrices approach
Authors: Barbary Mohamed , Abd ElAzeem Mohamed H. 
Published: February 2021

AbstractThe detection and tracking of extended stealth targets (ESTs) is a challenging task in radar technology, especially if from image observations because of the fluctuations of radar cross section. To overcome this challenge, multi‐Bernoulli (MB) filter can be used to extract the extended target (ET) states in efficient and reliable manner. Recently, the MB‐filter‐based random matrices model (RMM) approach has been proposed for ellipsoidal ET tracking with additional state variables. However, RMM‐MB filter is demonstrated with known detection profile, which is unsuitable for EST tracking. Thus, a joint detection and tracking of multiple ESTs based on track‐before‐detect (TBD) approach, which is an efficient way to track low‐observable ESTs, is proposed. In EST‐RMM‐TBD scenarios, although the extension ellipsoid is efficient, it may not be accurate because of some missing useful information, such as size, shape, and orientation. To address this, a EST‐sub‐RMM‐TBD composed of sub‐ellipses is introduced, each representing an RMM. Based on such models, a sub‐RMM‐MB‐TBD filter is used to estimate the kinematic states and extensions of sub‐objects for each EST. Furthermore, a sequential Monte Carlo (SMC) implementation to estimate non‐linear kinematic EST state is applied. The results indicate that the proposed SMC‐sub‐RMM‐MB‐TBD filter has more accurate cardinality estimation and smaller optimal sub‐pattern assignment errors than the recent extended tracking filters.
Incentive‐based feasibility of a hybrid AC/DC microgrid in Saudi Arabia
Authors: Alahmed A. , Alharbi H. , Elamin I. , Al‐Muhaini M. 
Published: February 2021

AbstractThe concept of microgrids (MGs) is revolutionizing the current power system. Most of the contemporary MGs are AC based; however, and due to the growth of DC‐based machines and household appliances, hybrid AC/DC MGs are noticeably gaining more attention. This paper carries a detailed and comprehensive economic analysis on a proposed hybrid AC/DC MG in the Kingdom of Saudi Arabia, a region where MGs are rarely studied. The aim is to find if such configurations are economically feasible in the region, and what incentives are needed to ensure feasibility. Multiple load categories and renewable generation sources are modelled from real and local data to enhance the practicality of the study. Using the designed MG testbed, the incentive‐based economic feasibility study is implemented to analyze the effectivity of the configuration and the proposed testbed in the region. The research concludes that the hybrid framework is not economically feasible due to the subsidized low energy retail prices in the kingdom, which makes customers unwilling to join a MG network that might charge higher rates. A comprehensive financial model is introduced to suggest proper incentives, possibly by the government, to the different customer and income classes to make the AC/DC MG option feasible.
Efficient tracking of spatially correlated signals in wireless sensor fields: A weighted stochastic gradient approach
Authors: Alasti Hadi 
Published: February 2021

AbstractA weighted stochastic gradient algorithm is proposed for cost‐efficient tracking of unknown, correlated spatial signals from randomly distributed sensor observations in localized wireless sensor field. The algorithm is implemented in spatial modelling and spatial tracking phases. In spatial modelling phase, the algorithm finds the model parameters, and in spatial tracking phase, it updates these parameters. The spatial signal is modelled with its M iso‐contour lines at equally spaced levels and the sensors with sensor observations in Δ margin of these contour levels report to the fusion centre (FC) for spatial monitoring purpose. Based on progressive learning and in successive iterations, the algorithm improves its findings of the signal strength's range, and the spatial, temporal and spectral attributes of the signal. To reduce the cost, in each iteration, only a subset of wireless sensors transmits the observations to the FC, in response to its query. In this article, the percentage of the reporting sensors to the FC is defined as the algorithm's cost. With importance sampling perspective, the sample space is reduced to those sensors whose observations are within a Δ margin of atleast one of these M contour levels. The Δ margin is pruned or enhanced using the proposed weighted stochastic gradient algorithm, dynamically in order to reduce the spatial tracking cost. The evaluation results show that after spatial modelling, spatial tracking is drastically of low cost and its performance is better than that of the conventional stochastic gradient method. The modelling error, the cost and the convergence of the proposed algorithm are investigated extensively, in this article. Spatial correlation in signal distribution and the coordinates of the wireless sensors are the only initial assumptions in spatial monitoring of the unknown signal distribution. The main purpose of this algorithm is low‐cost identification of unknown correlated spatial signals from sensor observations, over time. An example for application of the proposed algorithm is environmental monitoring using wireless sensor observations.
Revisiting the analysis of HW Virginis eclipse timing data
Authors: Esmer Ekrem M. , Baştürk Özgür , Hinse Tobias C. , Selam Selim O. , Correia Alexandre C. M. 
Published: February 2021

Context. HW Vir is a short-period binary that presents eclipse timing variations. Circumbinary planets have been proposed as a possible explanation, although the properties of the planets differ in each new study.
Aims. Our aim is to perform robust model selection methods for eclipse timing variations (ETV) and error calculation techniques based on a frequentist approach for the case of the HW Vir system.
Methods. We initially performed simultaneous light and radial velocity curve analysis to derive the masses of the binary. We then analyzed the eclipse timing variation of the system by fitting multiple models. To select the best model, we searched the confidence levels for the best model by creating an χ2 surface grid and bootstrap methods for each pair of parameters. We searched for stable orbital configurations for our adopted ETV model.
Results. The masses of the binary are found as 0.413 ± 0.008 M⊙ and 0.128 ± 0.004 M⊙. Under the assumption of two light time effects superimposed on a secular change, the minimum masses of the circumbinary objects are calculated as 25.0−2.2+3.5 MJup and 13.9−0.45+0.60 MJup. The projected semi-major axes are found to be 7.8−1.0+1.4 and 4.56−0.22+0.27 au in respective order. We find that this configuration is unstable within a 3σ range on the semi-major axis and eccentricity of the outer circumbinary object.
Testing the models of X-ray driven photoevaporation with accreting stars in the Orion Nebula Cluster
Authors: Flaischlen S. , Preibisch T. , Manara C. F. , Ercolano B. 
Published: February 2021

Context. Recent works highlight the importance of stellar X-rays on the evolution of the circumstellar disks of young stellar objects, especially for disk photoevaporation.
Aims. A signature of this process may be seen in the so far tentatively observed dependence of stellar accretion rates on X-ray luminosities. According to models of X-ray driven photoevaporation, stars with higher X-ray luminosities should show lower accretion rates, on average, in a sample with similar masses and ages.
Methods. To this aim, we have analyzed X-ray properties of young stars in the Orion Nebula Cluster determined with Chandra during the COUP observation as well as accretion data obtained from the photometric catalog of the HST Treasury Program. With these data, we have performed a statistical analysis of the relation between X-ray activity and accretion rates using partial linear regression analysis.
Results. The initial anticorrelation found with a sample of 332 young stars is considerably weaker compared to previous studies. However, excluding flaring activity or limiting the X-ray luminosity to the soft band (0.5−2.0 keV) leads to a stronger anticorrelation, which is statistically more significant. Furthermore, we have found a weak positive correlation between the higher component of the plasma temperature gained in the X-ray spectral fitting and the accretion rates, indicating that the hardness of the X-ray spectra may influence the accretion process.
Conclusions. There is evidence for a weak anticorrelation, as predicted by theoretical models, suggesting that X-ray photoevaporation modulates the accretion rate through the inner disk at late stages of disk evolution, leading to a phase of photoevaporation-starved accretion.
Connecting X-ray nuclear winds with galaxy-scale ionised outflows in two z  ∼  1.5 lensed quasars
Authors: Tozzi G. , Cresci G. , Marasco A. , Nardini E. , Marconi A. , Mannucci F. , Chartas G. , Rizzo F. , Amiri A. , Brusa M. , Comastri A. , Dadina M. , Lanzuisi G. , Mainieri V. , Mingozzi M. , Perna M. , Venturi G. , Vignali C. 
Published: February 2021

Aims. Outflows driven by active galactic nuclei (AGN) are expected to have a significant impact on host galaxy evolution, but the matter of how they are accelerated and propagated on galaxy-wide scales is still under debate. This work addresses these questions by studying the link between X-ray, nuclear ultra-fast outflows (UFOs), and extended ionised outflows, for the first time, in two quasars close to the peak of AGN activity (z ∼ 2), where AGN feedback is expected to be more effective.
Methods. Our selected targets, HS 0810+2554 and SDSS J1353+1138, are two multiple-lensed quasars at z ∼ 1.5 with UFO detection that have been observed with the near-IR integral field spectrometer SINFONI at the VLT. We performed a kinematical analysis of the [O III]λ5007 optical emission line to trace the presence of ionised outflows.
Results. We detected spatially resolved ionised outflows in both galaxies, extended more than 8 kpc and moving up to v > 2000 km s−1. We derived mass outflow rates of ∼12 M⊙ yr−1 and ∼2 M⊙ yr−1 for HS 0810+2554 and SDSS J1353+1138.
Conclusions. Compared with the co-hosted UFO energetics, the ionised outflow energetics in HS 0810+2554 is broadly consistent with a momentum-driven regime of wind propagation, whereas in SDSS J1353+1138, it differs by about two orders of magnitude from theoretical predictions, requiring either a massive molecular outflow or a high variability of the AGN activity to account for such a discrepancy. By additionally considering our results together with those from the small sample of well-studied objects (all local but one) having both UFO and extended (ionised, atomic, or molecular) outflow detections, we found that in 10 out of 12 galaxies, the large-scale outflow energetics is consistent with the theoretical predictions of either a momentum- or an energy-driven scenario of wind propagation. This suggests that such models explain the acceleration mechanism of AGN-driven winds on large scales relatively well.
Allometric Scaling of Force-velocity Test Output Among Pre-pubertal Basketball Players
Authors: Martinho Diogo V. , Baptista Rafael , Teixeira Anderson S. , Duarte Joao P. , Valente-dos-Santos Joao , Coelho-e-Silva Manuel J. , Santos Amândio Manuel Cupido , Armstrong Neil 
Published: February 2021

AbstractBasketball is characterized by high-intensity episodes predominantly reliant on anaerobic metabolism. The force-velocity test enables individual determination of an optimal braking force and emerged as appropriate to estimate optimal peak power. It has rarely been used in youth basketball. This study aimed to examine the contribution of body size, composition, and biological maturation to interindividual variation in force-velocity test output among pre-pubertal basketball players. The sample consisted of 64 male participants (8.4–12.3 years). Stature, sitting height, body mass and two skinfolds were measured, and leg length estimated. Fat-free mass and lower limb volume were estimated from anthropometry. Age at peak height velocity was predicted from maturity offset. Optimal peak power was correlated with all body size descriptors (correlation: 0.541–0.700). Simple allometric models explained 30–47% of inter-individual variance, with fat-free mass being the best predictor of performance. Whole-body fat-free mass (as a surrogate for active muscle mass) plus the indicator of maturation emerged as the best proportional allometric model (53% explained variance). Even at pre-pubertal ages, the interpretation of the force-velocity test requires assessing the metabolically active component of body mass.