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Nitrogen (N) bioavailability affects phytoplankton growth and primary production in the aquatic environment. N bioavailability is partly determined by biological N cycling processes that either transform N species or remove fixed N. Reliable estimates of their kinetic parameters can help understand the distribution of N cycling processes. However, available estimates of kinetic parameters are often derived from microbial isolates and may not be representative of the natural environment. Observations are particularly lacking in estuarine and coastal waters. We conducted isotope tracer addition incubations to evaluate substrate affinities of nitrification, denitrification and anammox in the Chesapeake Bay water column. The half‐saturation constant for ammonia oxidation ranged from 0.38 to 0.75 μM ammonium, substantially higher than observed in the open oceans. Half‐saturation constants for denitrification—0.92–1.86 μM nitrite or 1.15 μM nitrate—were within the lower end or less than those reported for other aquatic environments and for denitrifier isolates. Interestingly, water column denitrification potential was comparable to that of sedimentary denitrification, highlighting the contribution of the water column to N removal during anoxia. Mostly undetectable anammox rates prevented us from deriving the half‐saturation constants, suggesting a low affinity of anammox. Using these substrate kinetics, we were able to predict in situ N cycling rates and explain the vertical distribution of N nutrient concentrations. Our newly derived substrate kinetics parameters can be useful for improving model representation of N nutrient dynamics in estuarine and coastal waters, which is critical for assessing the ecosystem productivity and function. [ABSTRACT FROM AUTHOR]

As a key biogeochemical pathway in the marine nitrogen cycle, nitrification (ammonia oxidation and nitrite oxidation) converts the most reduced form of nitrogen – ammonium–ammonia (NH 4+ –NH 3) – into the oxidized species nitrite (NO 2-) and nitrate (NO 3-). In the ocean, these processes are mainly performed by ammonia-oxidizing archaea (AOA) and bacteria (AOB) and nitrite-oxidizing bacteria (NOB). By transforming nitrogen speciation and providing substrates for nitrogen removal, nitrification affects microbial community structure; marine productivity (including chemoautotrophic carbon fixation); and the production of a powerful greenhouse gas, nitrous oxide (N 2 O). Nitrification is hypothesized to be regulated by temperature, oxygen, light, substrate concentration, substrate flux, pH and other environmental factors. Although the number of field observations from various oceanic regions has increased considerably over the last few decades, a global synthesis is lacking, and understanding how environmental factors control nitrification remains elusive. Therefore, we have compiled a database of nitrification rates and nitrifier abundance in the global ocean from published literature and unpublished datasets. This database includes 2393 and 1006 measurements of ammonia oxidation and nitrite oxidation rates and 2242 and 631 quantifications of ammonia oxidizers and nitrite oxidizers, respectively. This community effort confirms and enhances our understanding of the spatial distribution of nitrification and nitrifiers and their corresponding drivers such as the important role of substrate concentration in controlling nitrification rates and nitrifier abundance. Some conundrums are also revealed, including the inconsistent observations of light limitation and high rates of nitrite oxidation reported from anoxic waters. This database can be used to constrain the distribution of marine nitrification, to evaluate and improve biogeochemical models of nitrification, and to quantify the impact of nitrification on ecosystem functions like marine productivity and N 2 O production. This database additionally sets a baseline for comparison with future observations and guides future exploration (e.g., measurements in the poorly sampled regions such as the Indian Ocean and method comparison and/or standardization). The database is publicly available at the Zenodo repository: 10.5281/zenodo.8355912 (Tang et al., 2023). [ABSTRACT FROM AUTHOR]

Estuaries emit a large but highly uncertain amount of Nitrous oxide (N2O) into the atmosphere. To better understand N2O cycling processes in estuaries, we provide the first direct observations of N2O consumption in the seasonally anoxic Chesapeake Bay, the largest estuary in the United States. N2O consumption rates in anoxic waters reached up to 3.3 nmol L−1 d−1 but were generally undetectable in oxygenated waters. However, N2O consumption rates were substantially enhanced when the oxygen concentration was experimentally decreased in initially oxygenated samples, indicating the potential of N2O consumption in oxygenated environments, for example, surface waters. These potential N2O consumption rates followed Michaelis‐Menten kinetics as a function of increasing N2O substrate concentration. N2O‐consuming microbes that predominantly contained the clade II nitrous oxide reductase gene were detected throughout the water column. These new observations of environmental controls on N2O consumption will benefit the modeling of N2O cycling and help to constrain the estuarine N2O flux. Plain Language Summary: Nitrous oxide (N2O) gas affects Earth's climate system as a powerful greenhouse gas and ozone‐depleting agent. A large amount of N2O is released from estuarine environments into the atmosphere but the estimate of the total flux remains highly uncertain. To better estimate estuarine N2O flux, an improved understanding of the distribution and environmental controls on N2O production and consumption would be very useful. Previous studies have mainly focused on N2O production processes. Here we used isotope tracers to directly measure the N2O consumption rate and used molecular techniques to characterize N2O‐consuming microbes in the water column of the largest estuary in the United States—the Chesapeake Bay. We found a strong dependence of N2O consumption rate on oxygen and N2O substrate concentration: the N2O consumption rate decreases as oxygen rises and increases with higher N2O substrate concentration. N2O‐consuming microbes were detected across the water column in both fall and summer. Overall, these new observations will help to constrain estimates of net N2O emission from estuaries and guide mitigation efforts to reduce N2O emissions from anthropogenic perturbations. Key Points: Nitrous oxide (N2O) consumption rates were measured in the oxygenated and anoxic waters of the Chesapeake Bay, revealing large N2O consumption potentialN2O consumption rates showed a strong dependence on oxygen and N2O substrate concentrationClade II nitrous oxide reductase genes were more abundant than clade I nitrous oxide reductase genes in the Chesapeake Bay [ABSTRACT FROM AUTHOR]

Estuaries at the global scale are significant but highly uncertain sources of atmospheric nitrous oxide (N2O), which is an intense greenhouse gas and ozone depletion agent. As the largest estuary in the United States, the Chesapeake Bay is suggested to be a spatially and temporally variable source and sink of N2O. However, limited observations of N2O cycling preclude us from estimating and predicting its net N2O flux. To improve our mechanistic understanding of the processes that control the N2O flux at the point of production, we applied multiple 15N tracers (NH4+15, 15N‐urea, NO2−15, and NO3−15) to separately track N2O production from nitrification and denitrification under in situ and manipulated O2 concentrations in the Chesapeake Bay. Nitrification was the major N2O production pathway in oxic waters (up to 7.5 nmol N2O L−1 d−1). In contrast, denitrification dominated N2O production from hypoxic/anoxic waters (up to 20 nmol N2O L−1 d−1). N2O production from urea was observed for the first time in estuarine waters. The contribution from urea was small, but interestingly, showed a depth pattern distinct from other N2O precursors. Experimentally lowering the O2 concentration substantially enhanced N2O production. Therefore, the expansion of hypoxic and anoxic zones in the Chesapeake Bay under climate change as suggested by some climate models may favor the production of N2O, potentially providing positive feedback on warming. Overall, our study provides mechanistic constraints on N2O dynamics that could benefit modeling studies to better estimate the N2O flux in the Chesapeake Bay and other coastal environments. [ABSTRACT FROM AUTHOR]

Variation in the microbial cycling of nutrients and carbon in the ocean is an emergent property of complex planktonic communities. While recent findings have considerably expanded our understanding of the diversity and distribution of nitrogen (N2) fixing marine diazotrophs, knowledge gaps remain regarding ecological interactions between diazotrophs and other community members. Using quantitative 16S and 18S V4 rDNA amplicon sequencing, we surveyed eukaryotic and prokaryotic microbial communities from samples collected in August 2016 and 2017 across the Western North Atlantic. Leveraging and significantly expanding an earlier published 2015 molecular dataset, we examined microbial community structure and ecological co-occurrence relationships associated with intense hotspots of N2 fixation previously reported at sites off the Southern New England Shelf and Mid-Atlantic Bight. Overall, we observed a negative relationship between eukaryotic diversity and both N2 fixation and net community production (NCP). Maximum N2 fixation rates occurred at sites with high abundances of mixotrophic stramenopiles, notably Chrysophyceae. Network analysis revealed such stramenopiles to be keystone taxa alongside the haptophyte diazotroph host Braarudosphaera bigelowii and chlorophytes. Our findings highlight an intriguing relationship between marine stramenopiles and high N2 fixation coastal sites. [ABSTRACT FROM AUTHOR]

Diazotrophs play a critical role in the biogeochemical cycling of nitrogen, carbon, and other elements in the global ocean. Despite their well‐recognized role, the diversity, abundance, and distribution of diazotrophs in the world's ocean remain poorly characterized largely due to limited observations. Here we update the database of diazotroph nifH gene abundances and assess how environmental factors may regulate diazotrophs at the global scale. Our meta‐analysis more than doubles the number of observations in the previous database. Using linear and nonlinear regressions, we find that the abundances of Trichodesmium, UCYN‐A, UCYN‐B, and Richelia relate differently to temperature, light, and nutrients. We further apply a random forest algorithm to estimate the global distributions of these diazotrophic groups, identifying undersampled potential hot spots of diazotrophy in the South Atlantic and southern Indian Ocean, and in coastal waters. The distinct ecophysiologies of diazotrophs highlighted here argue for separate parameterizations of different diazotrophs in model simulations. Plain Language Summary: Microbial communities drive the cycling of critical elements like carbon and nitrogen in the ocean. By converting N2 into more bioavailable nitrogen, diazotrophs alleviate nitrogen limitation and support primary production. Despite their importance, their distributions are poorly characterized in great part due to limited observations. Here we compile from the literature observations to update the global database of marine diazotrophs. We also assess how the abundance and distribution of different types of diazotrophs at the global scale relate to environmental factors, including temperature, depth, and nutrients. Finally, we use a random forest machine learning method to predict the distribution of different types of diazotrophs in the world's ocean. Our results highlight the need for observations over broader oceanic regimes and a more granular representation of diazotrophy in models. Key Points: Based on a literature review, the database of marine diazotrophs is updated, more than doubling the number of observationsThe distributions of four major diazotrophic groups distinctly relate to temperature, light and nutrients at the global scaleA machine learning method is applied to derive global maps of these diazotrophic groups in the global ocean [ABSTRACT FROM AUTHOR]

Abstract Lineage analysis plays a central role in exploring the developmental potential of stem and progenitor cell populations. In higher vertebrates, a variety of techniques have been used to label individual cells or cell populations, including interspecies grafting, intracellular microinjection, and Cre-mediated recombination. However, these approaches often suffer from difficulties in progenitor cell targeting, low cellular resolution and/or ectopic labeling. To circumvent these issues, here we utilize replication incompetent avian (RIA) retroviruses to deliver combinations of fluorescent proteins into distinct cellular compartments in chick embryos. In particular, RIA-mediated lineage tracing is optimal for long term mapping of dispersing cell populations like the neural crest. Using this tool, we confirm that trunk neural crest cells are multipotent. Furthermore, our RIA vector is engineered to be fully adaptable for other purposes such as cell fate analysis, gene perturbation studies and time-lapse imaging. Taken together, we present a novel approach of multiplex lineage analysis that can be applied to normal and perturbed development of diverse cell populations in avian embryos. Highlights • Replication incompetent avian retroviruses facilitate multiplexed clonal analysis of migratory cells. • Trunk neural crest cells are multipotent. • Retroviral lineage tracing can be combined with other cell morphogenetic studies. [ABSTRACT FROM AUTHOR]

In order to realize sensorless control for brushless doubly fed induction machine (BDFIM), this paper presents a model reference adaptive system (MRAS) observer, designed based on the error of the control winding current. Furthermore, a phase-locked loop is employed to estimate the current winding position and rotor speed. Consequently, a detailed theoretical derivation proves that the MRAS observer is stable and the dynamic performance is good. Thus, it does not cause any estimated speed error in steady state. Moreover, the estimated position error is bounded and trivial, thus its effects on the sensorless control of the BDFIM are neglected. The correctness, feasibility, and robustness of the proposed sensorless control method are verified by means of experimental validation on a 30 kW test rig. [ABSTRACT FROM AUTHOR]

Abstract: A series of coating materials were prepared from two classes of hyperbranched polymers containing short fluorocarbon chains (HPEFs/HPUFs). The obtained hyperbranched polymers were characterized by FT-IR, 1H NMR, 13C NMR, 19F NMR, GPC and TG analyses. HPEFs/HPUFs exhibited very low surface free energies (13.67–24.49mJ/m2) which almost are independent of their internal backbone but dependent on the terminal fluorocarbon chains. Highly hydrophobic and/or oleophobic surfaces of cotton woven fabric can be achieved from these polymers by solution-immersion coating method. The static and dynamic wettabilities of the HPEFs/HPUFs treated fabrics have been investigated. The static contact angles reached to 146°, 122° and 102° for water, hexadecane and decane, respectively. The lowest contact angle hysteresis reached to 5.9°. [Copyright &y& Elsevier]

Presents an algorithm for combining symbol timing and carrier phase for continuous-phase modulation (CPM). Problems in the implementation of CPM; Implementation of the model using Walsh signal space receiver.

Presents information on a study which introduced a simple receiver structure for any continuous phase modulation (CPM) scheme. Discussion on CPM; Structure of receiver; Minimum projection distance and simulation results.

The realization of a controllable transparent conducting system with selective light transparency is crucial for exploring many of the most intriguing effects in top‐illuminated optoelectronic devices. However, the performance is limited by insufficient electrical conductivity, low work function, and vulnerable interface of traditional transparent conducting materials, such as tin‐doped indium oxide. Here, it is reported that two‐dimensional (2D) titanium carbide (Ti3C2Tx) MXene film acts as an efficient transparent conducting electrode for the lead sulfide (PbS) colloidal quantum dots (CQDs) photodiode with controllable near infrared transmittance. The solution‐processed interface engineering of MXene and PbS layers remarkably reduces the interface defects of MXene/PbS CQDs and the carrier concentration in the PbS layer. The stable Ti3C2Tx/PbS CQDs photodiodes give rise to a high specific detectivity of 5.51 × 1012 cm W−1 Hz1/2, a large dynamic response range of 140 dB, and a large bandwidth of 0.76 MHz at 940 nm in the self‐powered state, ranking among the most exceptional in terms of comprehensive performance among reported PbS CQDs photodiodes. In contrast with the traditional photodiode technologies, this efficient and stable approach opens a new horizon to construct widely used infrared photodiodes with CQDs and MXenes. [ABSTRACT FROM AUTHOR]

Znf703 is an RAR- and Wnt-inducible transcription factor that exhibits a complex expression pattern in the developing embryo: Znf703 mRNA is found in the early circumblastoporal ring, then later throughout the neural plate and its border, and subsequently in the mid/hindbrain and somites. We show that Znf703 has a different and separable function in early mesoderm versus neural crest and placode development. Independent of its early knockdown phenotype on Gdf3 and Wnt8, Znf703 disrupts patterning of distinct neural crest migratory streams normally delineated by Sox10, Twist, and Foxd3 and inhibits otocyst formation and otic expression of Sox10 and Eya1. Furthermore, Znf703 promotes massive overgrowth of SOX2+ cells, disrupting the SoxB1 balance at the neural plate border. Despite prominent expression in other neural plate border-derived cranial and sensory domains, Znf703 is selectively absent from the otocyst, suggesting that Znf703 must be specifically cleared or down-regulated for proper otic development. We show that mutation of the putative Groucho-repression domain does not ameliorate Znf703 effects on mesoderm, neural crest, and placodes. We instead provide evidence that Znf703 requires the Buttonhead domain for transcriptional repression. [ABSTRACT FROM AUTHOR]

The mammalian target of rapamycin (mTOR) is an evolutionarily conserved Ser/Thr protein kinase with essential cellular function via processing various extracellular and intracellular inputs. Two distinct multi-protein mTOR complexes (mTORC), mTORC1 and mTORC2, have been identified and well characterized in eukaryotic cells from yeast to human. Sin1, which stands for S ty1/Spc1- in teracting p rotein1, also known as mitogen-activated protein kinase (MAPK) a ssociated p rotein (MAPKAP)1, is an evolutionarily conserved adaptor protein. Mammalian Sin1 interacts with many cellular proteins, but it has been widely studied as an essential component of mTORC2, and it is crucial not only for the assembly of mTORC2 but also for the regulation of its substrate specificity. In this review, we summarize our current knowledge of the structure and functions of Sin1, focusing specifically on its protein interaction network and its roles in the mTOR pathway that could account for various cellular functions of mTOR in growth, metabolism, immunity and cancer. [ABSTRACT FROM AUTHOR]

This paper proposes a systematic method that precisely estimates the capacity factor (CF) of the variable-speed wind turbine (WT) by considering the coupled influence of the turbine operation constraints and the air density. To do so, the WT's operation is defined by introducing the QN-curve (denoting the generator torque versus rotor speed), and the influence of different QN-curves on the power production is analysed while considering the influence of the air density. Then, a practical power-curve model considering the constraint of the QN-curve is derived for the WT. Following that, the formulation and the procedure of CF estimation are presented. Lastly, the presented CF estimation approach is applied into an industrial WT while considering the wind sites with four different altitudes. Finally, the application results show the capabilities of the proposed approach in evaluating the CF under the coupled influence of the QN-curve constraint and the air density. Meanwhile, comparing the proposed approach to four empirical approaches demonstrates that the CF estimation based on empirical models has considerable deviations to the results of the presented model under different site altitudes. Furthermore, among the four empirical models, the CF estimations from the quadratic and the linear models present the least deviations to those by the proposed model at the sites with low altitude and high altitude, respectively. • A precise approach to estimate the CF of the variable-speed WT is proposed. • Coupled influence of the turbine operation and air density on the CF is included. • Proposed approach is applied to an industrial WT under different air density. • Considerable deviations are found between the empirical and proposed estimations. • CF is reduced following the decreasing air density. [ABSTRACT FROM AUTHOR]

The low coupling coefficient between the transmitter and receiver is the major constraint of a wireless power transfer (WPT) system. Although some approaches, such as increasing the quality factor and achieving precise impedance matching, can reduce the adverse impacts of the low coupling coefficient and improve the system performance, high leakage magnetic flux between the transmitter and receiver remains a problem. With the increase in transfer distance and the misalignment between the transmitter and receiver, the increasing leakage magnetic flux of nondirectional fields degrades the WPT system performance. This paper proposes an active field orientation method to shape the magnetic flux so as to minimize the leakage flux. The amplitude and phase angle of the magnetizing current are controlled, and a coil structure for minimizing the coupling among the transmitters and generating a three-dimensional magnetic field is proposed. This method realizes three-dimension full-range field orientation with adjustable magnitude and direction of B-field at an arbitrary point, and as a result the B-field is concentrated with reduced leakage magnetic flux. The proposed field orientation shaping technique is verified by theoretical analysis, simulation, and experimental results. [ABSTRACT FROM PUBLISHER]

The brushless doubly fed induction machine (BDFM) has great potential in the wind energy generation system because it offers the advantages of higher reliability and maintenance-free operation. In this paper, a mathematical model in the power windings stator flux orientation frame is discussed by taking the rotor flux as the disturbance. Consequently, the control of the BDFM system is implemented by generating suitable control winding currents. Moreover, in order to eliminate the speed error and compensate the system uncertainties caused by the rotor flux and parameter perturbations, an integral sliding mode variable structure controller for the rotor speed is developed, and the reactive power is adjusted by a proportional-integral (PI) controller in the outer-loop. Furthermore, the control winding currents are regulated by the PI control scheme in the inner-loop. The proposed control frame achieves a good static and satisfactory dynamic control performance. Finally, simulation and experimental results are used to verify the correctness and feasibility of the proposed method. [ABSTRACT FROM PUBLISHER]

The RXR agonist (triphenyltin, TPT) and the RXR antagonist (UVI3003) both show teratogenicity and, unexpectedly, induce similar malformations in Xenopus tropicalis embryos. In the present study, we exposed X. tropicalis embryos to UVI3003 in seven specific developmental windows and identified changes in gene expression. We further measured the ability of UVI3003 to activate Xenopus RXRα (xRXRα) and PPARγ (xPPARγ) in vitro and in vivo . We found that UVI3003 activated xPPARγ either in Cos7 cells ( in vitro ) or Xenopus embryos ( in vivo ). UVI3003 did not significantly activate human or mouse PPARγ in vitro ; therefore, the activation of Xenopus PPARγ by UVI3003 is novel. The ability of UVI3003 to activate xPPARγ explains why UVI3003 and TPT yield similar phenotypes in Xenopus embryos. Our results indicate that activating PPARγ leads to teratogenic effects in Xenopus embryos. More generally, we infer that chemicals known to specifically modulate mammalian nuclear hormone receptors cannot be assumed to have the same activity in non-mammalian species, such as Xenopus . Rather they must be tested for activity and specificity on receptors of the species in question to avoid making inappropriate conclusions. [ABSTRACT FROM AUTHOR]

BACKGROUND: In ToxCast™ Phase I, the U.S. EPA commissioned screening of 320 pesticides, herbicides, fungicides, and other chemicals in a series of high-throughput assays. The agency also developed a toxicological prioritization tool, ToxPi, to facilitate using ToxCast™ assays to predict biological function. OBJECTIVES: We asked whether top-scoring PPARγ activators identified in ToxCast™ Phase I were genuine PPARγ activators and inducers of adipogenesis. Next, we identified ToxCast™ assays that should predict adipogenesis, developed an adipogenesis ToxPi, and asked how well the ToxPi predicted adipogenic activity. METHODS: We used transient transfection to test the ability of ToxCast™ chemicals to modulate PPARγ and RXRα, and differentiation assays employing 3T3-L1 preadipocytes and mouse bone marrow-derived mesenchymal stem cells (mBMSCs) to evaluate the adipogenic capacity of ToxCast™ chemicals. RESULTS: Only 5/21 of the top scoring ToxCast™ PPARγ activators were activators in our assays, 3 were PPARγ antagonists, the remainder were inactive. The bona fide PPARγ activators we identified induced adipogenesis in 3T3-L1 cells and mBMSCs. Only 7 of the 17 chemicals predicted to be active by the ToxPi promoted adipogenesis, 1 inhibited adipogenesis, and 2 of the 7 predicted negatives were also adipogenic. Of these 9 adipogenic chemicals, 3 activated PPARγ, and 1 activated RXRα. CONCLUSIONS: ToxCast™ PPARγ and RXRα assays do not correlate well with laboratory measurements of PPARγ and RXRα activity. The adipogenesis ToxPi performed poorly, perhaps due to the performance of ToxCast™ assays. We observed a modest predictive value of ToxCast™ for PPARγ and RXRα activation and adipogenesis and it is likely that many obesogenic chemicals remain to be identified. [ABSTRACT FROM AUTHOR]

• Maximum wind energy extraction formulated. • Potential solution of generator torque sequence set predefined. • Efficient search algorithm to set out the optimization problem. • Validation on two wind turbine models with different scales. • More than 1% of increased energy extraction efficiency. Maximum wind energy extraction remains a challenge for the large-scale wind turbines due to their increasing moment of inertia. In this study, a novel nonlinear predictive control method using previewed wind speeds is proposed to address the issue of maximum wind energy extraction for variable-speed wind turbines. Different from the conventional structure, the proposed nonlinear predictive control is based on the discrete prediction model established by a large time step. By doing so, the number of time discrete points is significantly reduced and the quantity of the solution set becomes numerable. As a result, the implementation complexity and computational burden are able to be relieved, and the real-time implementation becomes practical and easy to carry out. The proposed method is demonstrated on two models of wind turbines with different scales, and its performance is compared with the industrial controller. Comparison results show that the increased energy extraction efficiency gained by the proposed method is more than 1% on the two turbine models under different wind conditions, and thus the superior capability in extracting wind energy promises potential industrial applications. Meanwhile, the expense is the considerable increment of torque variation, which can be relieved by revising the control parameters. The presented method provides new insights into the design of the control methods for wind turbines equipped with advanced measurement devices. [ABSTRACT FROM AUTHOR]

As onshore wind energy has depleted, the utilization of offshore wind energy has gradually played an important role in globally meeting growing green energy demands. However, the cost of energy (COE) for offshore wind energy is very high compared to the onshore one. To minimize the COE, implementing optimal design of offshore turbines is an effective way, but the relevant studies are lacking. This study proposes a method to minimize the COE of offshore wind turbines, in which two design parameters, including the rated wind speed and rotor radius are optimally designed. Through this study, the relation among the COE and the two design parameters is explored. To this end, based on the power-coefficient power curve model, the annual energy production (AEP) model is designed as a function of the rated wind speed and the Weibull distribution parameters. On the other hand, the detailed cost model of offshore turbines developed by the National Renewable Energy Laboratory is formulated as a function of the rated wind speed and the rotor radius. Then, the COE is formulated as the ratio of the total cost and the AEP. Following that, an iterative method is proposed to search the minimal COE which corresponds to the optimal rated wind speed and rotor radius. Finally, the proposed method has been applied to the wind classes of USA, and some useful findings have been obtained. [ABSTRACT FROM AUTHOR]

In the wind energy generation system, the brushless doubly-fed induction machine (BDFIM) has shown significant application potential, since it eliminates the electric brush and slip ring. However, the complicated rotor structure increases the control difficulty, especially resulting in complicated coupled terms in the current sub-system, which deteriorates the dynamic performance and reduces the system robustness. In order to address the problems caused by complex coupled terms, an internal model current control strategy is presented for the BDFIM, and an active damping term is designed for suppressing the disturbance caused by the total resistance. The proposed method simplifies the controller parameters design, and it achieves the fast-dynamic response and the good tracking performance, as well as good robustness. On the other hand, the feedforward term composed by the grid voltage is added to the internal model controller in order to suppress the disturbance when the symmetrical grid voltage sag happens. Finally, the simulation and experimental results verify the feasibility and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]