Frequency deviations of power systems caused by grid-connected wind power fluctuations is one of the key factors which restrains the increase of wind penetration level. This paper examines a combined ...wind and hybrid energy storage system (HESS, supercapacitor, and battery) to smooth wind power fluctuations. A fuzzy-based wind-HESS system (FWHS) controller is proposed to suppress the wind power fluctuations. The proposed controller takes full advantage of the complimentary characteristics of the supercapacitor and battery with the supercapacitor and battery in charge of high and middle frequency components of wind fluctuations, respectively. A differential evolution (DE)-based optimal sizing method for HESS systems is introduced to evaluate the minimum capacity of HESS as being limited by grid frequency deviation. The efficiency of the proposed scheme in the paper for wind-HESS system is evaluated by a real Chinese power system.
A frequency-based approach is proposed in this paper to size a battery-supercapacitor energy storage system for maintaining power balance of an isolated system with high penetration of wind ...generation, thus to maintain the grid frequency stability with the stochastic wind power fluctuations being considered. The sizing method proposed makes full use of the combined technical merits of two types of energy storage systems, battery and supercapacitor, as their specific power/energy densities and the corresponding expected life cycle cost/year are different. The power imbalance between hourly dispatched wind power and the corresponding actual real-time wind power output is decomposed into different time-varying periodic components by use of the Fourier transformation. Then two different types of energy storage systems are applied to balance the low-frequency and intermediate-frequency component respectively. A computational procedure is developed in the paper for choosing the optimal cut-off frequencies in determining the range of low and intermediate frequency for sizing the hybrid energy storage system. Comparative studies of a real isolated system in China are presented in the paper to demonstrate the effectiveness of the proposed method.
Grid connection of a DFIG for power generation changes the power system load flow and introduces dynamic interactions with the synchronous generators (SGs). A method is proposed in this paper for the ...separate examination of the impact of those two affecting factors, the change of load flow and dynamic interaction brought about by the DFIG, on the electromechanical oscillation modes of a power system. The method is developed on the establishment of a "closed-loop control system" type of state space model of the power system where the DFIG is treated as the feedback controller. The established model unambiguously indicates that the impact of the DFIG can be examined separately: (1) With the DFIG being modelled as a constant power injection into the system, the impact of the load flow change brought about by the DFIG on the oscillation modes is determined; (2) The impact of the dynamic interactions introduced by the DFIG is estimated by calculating the contribution of the damping torque from the DFIG with its full dynamics being considered. Thus a more detailed examination on and deeper insight into the impact of grid connection of the DFIGs on power system small-signal angular stability is obtained by using the proposed method.
This paper derives the index of dynamic interactions (IDI), which is the sensitivity of a power system electromechanical oscillation mode (EOM) of concern to the dynamic interactions introduced by a ...grid-connected double-fed induction generator (DFIG). Based on the IDI, analysis is carried out with the following generally-applicable conclusions obtained: 1) Impact of dynamic interactions introduced by the DFIG increases when wind power penetration increases; 2) as long as the frequency response of an equivalent single DFIG model approximately matches the frequency response of a wind farm around the frequency of electromechanical oscillations of concern, this equivalent dynamic model of single DFIG can be used to represent the wind farm to examine the impact of wind farm on EOMs. Furthermore, an indicator of DFIG control (IDC) is derived for comparing the impact of terminal voltage control and reactive power control implemented by the DFIG. Main merit of the IDC is the computational simplicity without need to know dynamic model of the DFIG to indicate that either the terminal voltage control or the reactive power control is more beneficial to power system stability. An example multi-machine power system with grid-connected DFIGs is presented to demonstrate and validate the analysis and conclusions made in the paper.
Frequency deviation of power systems caused by grid-connected wind power fluctuations is one of the key factors limiting the level of wind penetration. Applying an energy storage system (ESS) to ...overcome the constraint of frequency deviation can increase the level of permitted wind penetration. This paper proposes a method to evaluate the wind penetration as limited by grid frequency deviation and to size the ESS to increase the permitted wind penetration to an expected level. The proposed method treats wind power fluctuations as a stochastic process rather than deterministic signal and takes the frequency response characteristics of power grid into full consideration. Application of the proposed method is based on theoretical derivations and does not require conducting dynamic simulation. It can catch the stochastic characteristic of wind power fluctuations.
The calf stage is a critical period for the development of heifers. Newborn calves have low gastrointestinal barrier function and immunity before weaning, making them highly susceptible to infection ...by various intestinal pathogens. Diarrhea in calves poses a significant threat to the health of young ruminants and may cause serious economic losses to livestock farms. Antibiotics are commonly used to treat diarrhea and promote calf growth, leading to bacterial resistance and increasing antibiotic residues in meat. Therefore, finding new technologies to improve the diarrhea of newborn calves is a challenge for livestock production and public health. The operation of the gut microbiota in the early stages after birth is crucial for optimizing immune function and body growth. Microbiota colonization of newborn animals is crucial for healthy development. Early intervention of the calf gastrointestinal microbiota, such as oral probiotics, fecal microbiota transplantation and rumen microbiota transplantation can effectively relieve calf diarrhea. This review focuses on the role and mechanisms of oral probiotics such as
,
and
in relieving calf diarrhea. The aim is to develop appropriate antibiotic alternatives to improve calf health in a sustainable and responsible manner, while addressing public health issues related to the use of antibiotics in livestock.
Biochanin A (BCA), an isoflavone phytoestrogen, is a secondary metabolite produced mainly in leguminous plants. The objective of this study was to evaluate the effect of BCA on lactation performance, ...nitrogen metabolism, and the health of dairy goat. Thirty mid-lactation Saanen dairy goats were divided into three groups randomly: control, 2 g/d BCA group, and 6 g/d BCA group. After 36 days of feeding, 30 dairy goats were transferred to individual metabolic cages. Subsequently, milk yield, feed intake, total feces, and urine excretion were recorded and samples were collected continuously for 3 days. Blood and ruminal fluid samples were collected over the subsequent 4 days. Milk yield, milk protein, fat content, and the feed conversion ratio of dairy goat were significantly increased by the BCA treatment. The levels of serum 17β-estradiol, growth hormone, insulin-like growth factor 1, glutathione peroxidase activity, and total antioxidant capacity were also increased significantly by BCA, indicating that BCA enhanced the antioxidant capacity of dairy goat. Amino acid degradation was significantly inhibited, while the ammonia nitrogen content was reduced significantly by BCA. Total volatile fatty acids was significantly increased by BCA supplementation. In addition, the relative abundance of
was decreased significantly. However, the growth of nitrogen metabolism and cellulolytic bacteria was significantly increased under BCA treatment, including
.,
,
, and
. In conclusion, supplementation with BCA improved the milk production performance, nitrogen metabolism, rumen fermentation and antioxidant capacity, and regulated the rumen microbiome of dairy goat.
Cathelicidins (CATHs) are host defense peptides (HDPs) that play an important role in the innate immune response against infections. Although multiple functions of cathelicidins have been described, ...including direct antimicrobial activity and several immunomodulatory effects on the host, relatively little is known about their antiviral activity. Therefore,
antiviral activity of chicken cathelicidins and the underlying mechanism was investigated in this study against different influenza A virus (IAV) strains. Our results show that chicken CATH-B1 has broad anti-IAV activity compared to other cathelicidins (CATH-1, -2, -3, LL-37, PMAP-23, and K9CATH) with an inhibition of viral infection up to 80% against three tested IAV strains (H1N1, H3N1, and H5N1). In agreement herewith, CATH-B1 affected virus-induced inflammatory cytokines expression (IFN-β, IL-1β, IL-6, and IL-8). Incubation of cells with CATH-B1 prior to or after their inoculation with virus did not reduce viral infection indicating that direct interaction of virus with the peptide was required for CATH-B1's antiviral activity. Experiments using combined size exclusion and affinity-based separation of virus and peptide also indicated that CATH-B1 bound to viral particles. In addition, using electron microscopy, no morphological change of the virus itself was seen upon incubation with CATH-B1 but large aggregates of CATH-B1 and viral particles were observed, indicating that aggregation might be the mechanism of action reducing IAV infectivity. Neuraminidase (NA) activity assays using monovalent or multivalent substrates, indicated that CATH-B1 did not affect NA activity
, but negatively affected the ability of virus particles to interact with multivalent receptors, presumably by interfering with hemagglutinin activity. In conclusion, our results show CATH-B1 has good antiviral activity against IAV by binding to the viral particle and thereby blocking viral entry.
This paper proposes an analytic method based on finite-element method (FEM) for the rolling gaits of tensegrity robots. By analyzing forces during the rolling motions, the following problems can be ...solved. First, the relation between the actuator combinations (AC) and the rolling directions is discovered for controlling the rolling motions. Second, the influence of the driving parameters on the deformations is found out for obtaining the optimized control strategy. Third, the influence of the material parameters on the rolling motions is achieved as guidance to design physical robots. Tensegrity robots were proposed as novel mobile robots based on tensegrity structures that consist of discrete rigid struts and continuous elastic cables. The tensegrity structures process the shock resistance ability and high deformation capacity, and can be used to build lightweight mobile robots. The tensegrity robots can generate multiple gaits and multiple deformations. Rolling gaits are more stable than jumping and more efficient than crawling. Aiming at rolling gaits, to solve the three problems mentioned earlier, force analysis is required. The internal forces of the tensegrity structures always keep balance to maintain the shape of the structures, however, as the structures are highly coupled, the variation of one force will change the rest of the forces and generates feedback effects to this force. As the number of the forces increase with the growing number of struts, the force analysis becomes more and more complicated. The existing exhaustive experimental method can obtain the relation between the AC and the rolling directions through massive experiments, but this method cannot tell the influence of the driving parameters on the deformations and the experiment results based on certain robots are not suitable for other robots without analyzing the influence of the material parameters. In this paper, an analytic method based on FEM is introduced. A six-strut tensegrity model is used as an example to test the feasibility of the method. Experiments on a physical robot are performed to verify the reliability of the computation results.
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