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Schaller, Martin, Matthias Bein, Hans C. Korting, Stefan Baur, Gerald Hamm, Michel Monod, Sabine Beinhauer i Bernhard Hube. "The Secreted Aspartyl Proteinases Sap1 and Sap2 Cause Tissue Damage in an In Vitro Model of Vaginal Candidiasis Based on Reconstituted Human Vaginal Epithelium". Infection and Immunity 71, nr 6 (czerwiec 2003): 3227–34. http://dx.doi.org/10.1128/iai.71.6.3227-3234.2003.
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ABSTRACT Secreted aspartyl proteinases (Saps) contribute to the ability of Candida albicans to cause mucosal and disseminated infections. A model of vaginal candidiasis based on reconstituted human vaginal epithelium (RHVE) was used to study the expression and role of these C. albicans proteinases during infection and tissue damage of vaginal epithelium. Colonization of the RHVE by C. albicans SC5314 did not cause any visible epithelial damage 6 h after inoculation, although expression of SAP2, SAP9, and SAP10 was detected by reverse transcriptase PCR. However, significant epithelial damage was observed after 12 h, concomitant with the additional expression of SAP1, SAP4, and SAP5. Additional transcripts of SAP6 and SAP7 were detected at a later stage of the artificial infection (24 h). Similar SAP expression profiles were observed in three samples isolated from human patients with vaginal candidiasis. In experimental infection, secretion of antigens Sap1 to Sap6 by C. albicans was confirmed at the ultrastructural level by using polyclonal antisera raised against Sap1 to Sap6. Addition of the aspartyl proteinase inhibitors pepstatin A and the human immunodeficiency virus proteinase inhibitors ritonavir and amprenavir strongly reduced the tissue damage of the vaginal epithelia by C. albicans cells. Furthermore, SAP null mutants lacking either SAP1 or SAP2 had a drastically reduced potential to cause tissue damage even though SAP3, SAP4, and SAP7 were up-regulated in these mutants. In contrast the vaginopathic potential of mutants lacking SAP3 or SAP4 to SAP6 was not reduced compared to wild-type cells. These data provide further evidence for a crucial role of Sap1 and Sap2 in C. albicans vaginal infections.
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Felk, Angelika, Marianne Kretschmar, Antje Albrecht, Martin Schaller, Sabine Beinhauer, Thomas Nichterlein, Dominique Sanglard, Hans C. Korting, Wilhelm Schäfer i Bernhard Hube. "Candida albicans Hyphal Formation and the Expression of the Efg1-Regulated Proteinases Sap4 to Sap6 Are Required for the Invasion of Parenchymal Organs". Infection and Immunity 70, nr 7 (lipiec 2002): 3689–700. http://dx.doi.org/10.1128/iai.70.7.3689-3700.2002.
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ABSTRACT The ability to change between yeast and hyphal cells (dimorphism) is known to be a virulence property of the human pathogen Candida albicans. The pathogenesis of disseminated candidosis involves adhesion and penetration of hyphal cells from a colonized mucosal site to internal organs. Parenchymal organs, such as the liver and pancreas, are invaded by C. albicans wild-type hyphal cells between 4 and 24 h after intraperitoneal (i.p.) infection of mice. In contrast, a hypha-deficient mutant lacking the transcription factor Efg1 was not able to invade or damage these organs. To investigate whether this was due to the inability to undergo the dimorphic transition or due to the lack of hypha-associated factors, we investigated the role of secreted aspartic proteinases during tissue invasion and their association with the different morphologies of C. albicans. Wild-type cells expressed a distinct pattern of SAP genes during i.p. infections. Within the first 72 h after infection, SAP1, SAP2, SAP4, SAP5, SAP6, and SAP9 were the most commonly expressed proteinase genes. Sap1 to Sap3 antigens were found on yeast and hyphal cells, while Sap4 to Sap6 antigens were predominantly found on hyphal cells in close contact with host cells, in particular, eosinophilic leukocytes. Mutants lacking EFG1 had either noticeably reduced or higher expressed levels of SAP4 to SAP6 transcripts in vitro depending on the culture conditions. During infection, efg1 mutants had a strongly reduced ability to produce hyphae, which was associated with reduced levels of SAP4 to SAP6 transcripts. Mutants lacking SAP1 to SAP3 had invasive properties indistinguishable from those of wild-type cells. In contrast, a triple mutant lacking SAP4 to SAP6 showed strongly reduced invasiveness but still produced hyphal cells. When the tissue damage of liver and pancreas caused by single sap4, sap5, and sap6 and double sap4 and -6, sap5 and -6, and sap4 and -5 double mutants was compared to the damage caused by wild-type cells, all mutants which lacked functional SAP6 showed significantly reduced tissue damage. These data demonstrate that strains which produce hyphal cells but lack hypha-associated proteinases, particularly that encoded by SAP6, are less invasive. In addition, it can be concluded that the reduced virulence of hypha-deficient mutants is not only due to the inability to form hyphae but also due to modified expression of the SAP genes normally associated with the hyphal morphology.
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Thompson, Stuart A., Omer L. Shedd, Kevin C. Ray, Michael H. Beins, Jesse P. Jorgensen i Martin J. Blaser. "Campylobacter fetus Surface Layer Proteins Are Transported by a Type I Secretion System". Journal of Bacteriology 180, nr 24 (15.12.1998): 6450–58. http://dx.doi.org/10.1128/jb.180.24.6450-6458.1998.
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ABSTRACT The virulence of Campylobacter fetus, a bacterial pathogen of ungulates and humans, is mediated in part by the presence of a paracrystalline surface layer (S-layer) that confers serum resistance. The subunits of the S-layer are S-layer proteins (SLPs) that are secreted in the absence of an N-terminal signal sequence and attach to either type A or B C. fetus lipopolysaccharide in a serospecific manner. Antigenic variation of multiple SLPs (encoded bysapA homologs) of type A strain 23D occurs by inversion of a promoter-containing DNA element flanked by two sapAhomologs. Cloning and sequencing of the entire 6.2-kb invertible region from C. fetus 23D revealed a probable 5.6-kb operon of four overlapping genes (sapCDEF, with sizes of 1,035, 1,752, 1,284, and 1,302 bp, respectively) transcribed in the opposite direction from sapA. The four genes also were present in the invertible region of type B strain 84-107 and were virtually identical to their counterparts in the type A strain. Although SapC had no database homologies, SapD, SapE, and SapF had predicted amino acid homologies with type I protein secretion systems (typified byEscherichia coli HlyBD/TolC or Erwinia chrysanthemi PrtDEF) that utilize C-terminal secretion signals to mediate the secretion of hemolysins, leukotoxins, or proteases from other bacterial species. Analysis of the C termini of four C. fetus SLPs revealed conserved structures that are potential secretion signals. A C. fetus sapD mutant neither produced nor secreted SLPs. E. coli expressing C. fetus sapA and sapCDEF secreted SapA, indicating that thesapCDEF genes are sufficient for SLP secretion. C. fetus SLPs therefore are transported to the cell surface by a type I secretion system.
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G, Venkata Anjani Kumar, i M. Damodar Reddy. "Fuzzy and PSO tuned PI controller based SAPF for Harmonic Mitigation". International Journal of Electrical and Electronics Research 11, nr 1 (30.03.2023): 119–25. http://dx.doi.org/10.37391/ijeer.110116.
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The development of a reliable power filter is essential for meeting the need for high-quality power. Current and voltage harmonics are a major contributor to poor power quality and must be eliminated. Shunt active power filters (SAPFs) can be installed to reduce the negative effects of harmonics. Fuzzy logic and proportional integral (PI) controllers excel at regulating DC link voltage in shunt active power filters (SAPFs). This research assessed how well Particle Swarm Optimization controls the DC link voltage in a Shunt Active Power Filter (SAPF), thereby mitigating harmonics. The appropriate PI control parameters are first determined using the Particle Swarm Optimization technique. The PSO-tuned PI parameters are combined with a fuzzy logic controller for the SAPF simulation. It has been demonstrated in simulations that a Shunt Active Power Filter (SAPF) with reference currents are generated in accordance with the instantaneous real and reactive power (p-q) theory, employing fuzzy and PSO -PI controller for diode rectifier type non-linear load. It is extremely effective for harmonic correction in distribution networks. The simulation work is carried out using MATLAB-SIMULINK.
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Singh, Harnek, Maneet Kour, Dip Vinod Thanki i Prakash Kumar. "A Review on Shunt Active Power Filter Control Strategies". International Journal of Engineering & Technology 7, nr 4.5 (22.09.2018): 121. http://dx.doi.org/10.14419/ijet.v7i4.5.20026.
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Shunt active power filter (SAPF) has now become a well-known sophisticated technology to overcome current harmonics and reactive power compensation issues. In this paper a technical review of various control strategies for operation of SAPF has been presented. Control strategies such as reference current generation by time domain, frequency domain and soft computing approaches; voltage control for dc link voltage regulation and current control for generating switching patterns for voltage source inverter has been discussed. This paper aims to provide a broad understanding on SAPFs for various research and engineering applications.
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Naglik, Julian R., George Newport, Theodore C. White, Lynette L. Fernandes-Naglik, John S. Greenspan, Deborah Greenspan, Simon P. Sweet, Stephen J. Challacombe i Nina Agabian. "In Vivo Analysis of Secreted Aspartyl Proteinase Expression in Human Oral Candidiasis". Infection and Immunity 67, nr 5 (1.05.1999): 2482–90. http://dx.doi.org/10.1128/iai.67.5.2482-2490.1999.
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ABSTRACT Secreted aspartyl proteinases are putative virulence factors inCandida infections. Candida albicans possesses at least nine members of a SAP gene family, all of which have been sequenced. Although the expression of the SAPgenes has been extensively characterized under laboratory growth conditions, no studies have analyzed in detail the in vivo expression of these proteinases in human oral colonization and infection. We have developed a reliable and sensitive procedure to detect C. albicans mRNA from whole saliva of patients with oral C. albicans infection and those with asymptomaticCandida carriage. The reverse transcription-PCR protocol was used to determine which of the SAP1 to SAP7genes are expressed by C. albicans during colonization and infection of the oral cavity. SAP2 and the SAP4to SAP6 subfamily were the predominant proteinase genes expressed in the oral cavities of both Candida carriers and patients with oral candidiasis; SAP4, SAP5, orSAP6 mRNA was detected in all subjects. SAP1and SAP3 transcripts were observed only in patients with oral candidiasis. SAP7 mRNA expression, which has never been demonstrated under laboratory conditions, was detected in several of the patient samples. All seven SAP genes were simultaneously expressed in some patients with oral candidiasis. This is the first detailed study showing that the SAP gene family is expressed by C. albicans during colonization and infection in humans and that C. albicans infection is associated with the differential expression of individualSAP genes which may be involved in the pathogenesis of oral candidiasis.
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Kale, Ishaan R., i Anand J. Kulkarni. "Cohort intelligence with self-adaptive penalty function approach hybridized with colliding bodies optimization algorithm for discrete and mixed variable constrained problems". Complex & Intelligent Systems 7, nr 3 (18.02.2021): 1565–96. http://dx.doi.org/10.1007/s40747-021-00283-3.
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AbstractRecently, several socio-/bio-inspired algorithms have been proposed for solving a variety of problems. Generally, they perform well when applied for solving unconstrained problems; however, their performance degenerates when applied for solving constrained problems. Several types of penalty function approaches have been proposed so far for handling linear and non-linear constraints. Even though the approach is quite easy to understand, the precise choice of penalty parameter is very much important. It may further necessitate significant number of preliminary trials. To overcome this limitation, a new self-adaptive penalty function (SAPF) approach is proposed and incorporated into socio-inspired Cohort Intelligence (CI) algorithm. This approach is referred to as CI–SAPF. Furthermore, CI–SAPF approach is hybridized with Colliding Bodies Optimization (CBO) algorithm referred to as CI–SAPF–CBO algorithm. The performance of the CI–SAPF and CI–SAPF–CBO algorithms is validated by solving discrete and mixed variable problems from truss structure domain, design engineering domain, and several problems of linear and nonlinear in nature. Furthermore, the applicability of the proposed techniques is validated by solving two real-world applications from manufacturing engineering domain. The results obtained from CI–SAPF and CI–SAPF–CBO are promising and computationally efficient when compared with other nature inspired optimization algorithms. A non-parametric Wilcoxon’s rank sum test is performed on the obtained statistical solutions to examine the significance of CI–SAPF–CBO. In addition, the effect of the penalty parameter on pseudo-objective function, penalty function and constrained violations is analyzed and discussed along with the advantages over other algorithms.
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Saleh, Kamel, i Ameen Madi. "A fault-tolerant photovoltaic integrated shunt active power filter with a 27-level inverter". International Journal of Electrical and Computer Engineering (IJECE) 11, nr 2 (1.04.2021): 1166. http://dx.doi.org/10.11591/ijece.v11i2.pp1166-1177.
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This paper introduces a fault-tolerant shunt active power filter (SAPF). The novility in of this work is that it poposes a solutions to increase the reliability of shunt active power filter to maintain its operation under a single-phase open-circuit fault in the SAPF. This will increase the reliability of the whole power system. The SAPF is composed of a 4-leg 27-level inverter based on asymmetric cascaded H-bridge topology. If an open-circuit fault is introduced to the operation of the SAPF, a special control technique will be implemented and the redundant leg of the SAPF will be activated. The fault-tolerant SAPF can do many tasks under healthy operating conditions and post and open circuit fault depending on the state of charge (SOC) of the batteries. It can mitigate harmonics in the power system, improve power factor in the system by injecting reactive power, and inject real power to the system. The proposed SAPF is tested and simulated in MATLAB/Simulink and the results have shown a significant improvement in total harmonics distortion (THD) of the source current from 13.9% to 3.9% under the normal operating condition and from 42% to 8.4% post and open circuit fault.
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Sao, Jitendra Kumar, Ramasamy Thaiyal Naayagi, Gayadhar Panda, Ram Dayal Patidar i Sushree Diptimayee Swain. "SAPF Parameter Optimization with the Application of Taguchi SNR Method". Electronics 11, nr 3 (24.01.2022): 348. http://dx.doi.org/10.3390/electronics11030348.
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Non-linear devices draw non-sinusoidal currents from the source; hence, they cause harmonic distortions in power systems. The shunt active power filter (SAPF) is a well-known method for alleviating current harmonics, compensating the reactive power and improving the power factor; however, the effective design of an SAPF is quite challenging and a thrust area of research. The current controlling technique, switching pulse generation technique and parameter selection are cumbersome tasks in SAPF design. SAPF performance depends on the proper selection of many parameters, such as filter interfacing impedance, DC-link capacitor and PI-controller gains. The effect of these parameters on the performance of SAPF has been studied and optimum values have been obtained by using the Taguchi method. This paper also indicates the benefits of using the Taguchi method compared with existing genetic algorithm (GA) for optimizing the parameters of the SAPF. An instantaneous reactive power theory (IRPT)-based SAPF has been modeled and simulated in MATLAB/Simulink. The SAPF’s parameters have been optimized by using the both proposed Taguchi SNR and the existing GA method. With optimized values of parameters results have been obtained, analyzed and the superiority of the proposed Taguchi method over the existing GA method is discussed. The simulation results were also validated with experimental results.
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Chen, Lan, Chen i Chen. "Adaptive Frequency-Based Reference Compensation Current Control Strategy of Shunt Active Power Filter for Unbalanced Nonlinear Loads". Energies 12, nr 16 (9.08.2019): 3080. http://dx.doi.org/10.3390/en12163080.
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The shunt active power filter (SAPF) is an effective means for the modification of power quality. However, the compensation performance of SAPF would be deteriorated when the unbalanced nonlinear loads are present in the power system. To enhance the compensation performance of SAPF, the adaptive frequency-based reference compensation current control strategy is proposed in this paper. The proposed solution procedure can be divided into three stages including adaptive frequency detection, phase synchronization, and adaptive compensation. With the tracking of power system frequency, the phase synchronization for the SAPF compensation can be effectively modified under the power variation of unbalanced nonlinear loads. Based on the correct synchronization phase angle, the reference compensation current of SAPF can be accurately obtained with the adaptive linear neural network (ALNN) in the stage of adaptive compensation. In addition, the direct current (DC)-link voltage of SAPF can also be effectively regulated to maintain the compensation performance. To verify the effectiveness of the proposed adaptive frequency-based reference compensation current control strategy, the comprehensive case studies implemented with the hardware-in-the-loop (HIL) mechanism are performed to examine the compliance with the specification limits of IEEE Standard 519-2014. The experimental results reveal that the performance of proposed SAPF control strategy is superior to that of the traditional instantaneous reactive power compensation control technique (p-q method) and sliding discrete Fourier transform (DFT).
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Hou, Rui, Pengfei Wang, Jian Wu i Dianguo Xu. "Research on Oscillation Suppression Methods in Shunt Active Power Filter System". Energies 15, nr 9 (25.04.2022): 3125. http://dx.doi.org/10.3390/en15093125.
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The shunt active power filter (SAPF) system oscillation is a massive threat to the security and stability of the power grid. This study classifies SAPF oscillation into two categories according to the difference in mechanisms. The SAPF oscillation in one category is caused by the resonant characteristics of a switching noise filter and is called external loop amplification. The SAPF oscillation in the other category is induced by the presence of a capacitor in the load current for SAPF and is called self-excited oscillation. Unlike previous studies, this study tried to reveal the internal relationship between the two kinds of SAPF oscillation, present a general shunt virtual-damping-based SAPF oscillation suppression strategy covering the previous resonant damping method, and provide the discrete domain stability criterion of the control system. The sampling frequency was at least six times the resonant frequency. The stability region was enlarged with an increase in the sampling frequency and narrowed with a rise in the resonant frequency. As to the harmful self-excited oscillation problem, this study proposes a composite control strategy combining selective harmonic compensation and grid-side current feedback. Moreover, this study considers the more general resistance–inductance–capacitance load situations and analyzes the stability of the SAPF–Thyristor Switched Capacitor (TSC) hybrid compensation system. Simulations and experiments demonstrated that the proposed compound control method can reduce the primary harmonics of the system by more than 90% and has a better oscillation suppression performance than previous suppression methods. In particular, if we selected the TSC series reactance rate following more than 6%, self-excited oscillation could usually be avoided.
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Hou, Rui, Pengfei Wang, Jian Wu i Dianguo Xu. "Research on Oscillation Suppression Methods in Shunt Active Power Filter System". Energies 15, nr 9 (25.04.2022): 3125. http://dx.doi.org/10.3390/en15093125.
Pełny tekst źródłaStreszczenie:
The shunt active power filter (SAPF) system oscillation is a massive threat to the security and stability of the power grid. This study classifies SAPF oscillation into two categories according to the difference in mechanisms. The SAPF oscillation in one category is caused by the resonant characteristics of a switching noise filter and is called external loop amplification. The SAPF oscillation in the other category is induced by the presence of a capacitor in the load current for SAPF and is called self-excited oscillation. Unlike previous studies, this study tried to reveal the internal relationship between the two kinds of SAPF oscillation, present a general shunt virtual-damping-based SAPF oscillation suppression strategy covering the previous resonant damping method, and provide the discrete domain stability criterion of the control system. The sampling frequency was at least six times the resonant frequency. The stability region was enlarged with an increase in the sampling frequency and narrowed with a rise in the resonant frequency. As to the harmful self-excited oscillation problem, this study proposes a composite control strategy combining selective harmonic compensation and grid-side current feedback. Moreover, this study considers the more general resistance–inductance–capacitance load situations and analyzes the stability of the SAPF–Thyristor Switched Capacitor (TSC) hybrid compensation system. Simulations and experiments demonstrated that the proposed compound control method can reduce the primary harmonics of the system by more than 90% and has a better oscillation suppression performance than previous suppression methods. In particular, if we selected the TSC series reactance rate following more than 6%, self-excited oscillation could usually be avoided.
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Ranga Rao, Chegudi, Ramadoss Balamurugan i RamaKoteswaraRao Alla. "Synchronization control techniques for shunt active power filter: an overview". Bulletin of Electrical Engineering and Informatics 12, nr 1 (1.02.2023): 1–9. http://dx.doi.org/10.11591/eei.v12i1.4300.
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The phase synchronization control technique of shunt active power filter (SAPF) is discussed in this article. Due to the harmful effects of harmonic currents on power systems, the issue of decreasing their effects has generated a lot of research. A SAPF is acknowledged as the most dependable instrument in this area. The SAPF will detects the current harmonics present in the power system and also generates and injects the corrective current mitigation in the power system to reduce the current harmonics. This implies that, aside from the capacity to create compensating current, it is more essential to ensure that the SAPF can work in phase with the operational power system so that the compensating current will properly injected. As a result, while constructing SAPF control algorithms, correct synchronisation techniques must be incorporated. In this article, the different types of phase synchronization approach have been discussed such as phase-locked loop (PLL), adaptive linear neuron (Adaline), and unit vector. The results of the study may be used as a guideline and source of information for determining the best method for synchronising SAPF with the associated power system.
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Soomro, Dur Muhammad, Sager K. Alswed, Mohd Noor Abdullah, Nur Hanis Mohammad Radzi i Mazhar Hussain Baloch. "Optimal design of a single-phase APF based on PQ theory". International Journal of Power Electronics and Drive Systems (IJPEDS) 11, nr 3 (1.09.2020): 1360. http://dx.doi.org/10.11591/ijpeds.v11.i3.pp1360-1367.
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The instantaneous active and reactive power (PQ) theory is one of the most widely used control theory for shunt active power filter (SAPF), which can be implemented in single-phase and three-phase systems. However, the SAPF with PQ theory still had ability to improve to become more efficient. This paper presents the optimal design of a single-phase SAPF in terms of reducing the current harmonic distortion and power loss in voltage source inverter (VSI) controlled with the semiconductor switching devices IGBT, MOSFET and Hybrid (combination of IGBT and MOSFET). In order to reduce the switching frequency and power loss of VSI, instead of using single-band hysteresis current controller (HCC), double-band HCC (DHCC) and triple-band HCC (THCC) is used in the SAPF. The designed SAPF is tested with different non-linear loads to verify the results by using MATLAB Simulink.
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Saleh, Kamel, i Omar Mahmoud. "Asymmetrical four-wire cascaded h-bridge multi-level inverter based shunt active power filter supplied by a photovoltaic source". International Journal of Power Electronics and Drive Systems (IJPEDS) 12, nr 3 (1.09.2021): 1673. http://dx.doi.org/10.11591/ijpeds.v12.i3.pp1673-1686.
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<span>This paper presents a novel shunt active power filter (SAPF). The power converter that is used in this SAPF is constructed from a four-leg asymmetric multi-level cascaded H-bridge (CHB) inverter that is fed from a photovoltaic source. A three-dimensional space vector modulation (3D-SVPWM) technique is adopted in this work. The multi-level inverter can generate 27-level output with harmonic content is almost zero. In addition to the capability to inject reactive power and mitigating the harmonics, the proposed SAPF has also, the ability to inject real power as it is fed from a PV source. Moreover, it has a fault-tolerant capability that makes the SAPF maintaining its operation under a loss of one leg of the multi-level inverter due to an open-circuit fault without any degradation in the performance. The proposed SAPF is designed and simulated in MATLAB SIMULINK using a single nonlinear load and the results have shown a significant reduction in total harmonics distortion (THD) of the source current under the normal operating condition and post a failure in one phase of the SAPF. Also, similar results are obtained when IEEE 15 bus network is used.</span>
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Giosa, Justine L., Paul Holyoke i Paul Stolee. "Let’s Get Real about Person- and Family-Centred Geriatric Home Care: A Realist Synthesis". Canadian Journal on Aging / La Revue canadienne du vieillissement 38, nr 4 (27.06.2019): 449–67. http://dx.doi.org/10.1017/s0714980819000023.
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RÉSUMÉCette étude a examiné les mécanismes complexes intervenant lors de la prestation de soins axés sur la personne et la famille (SAPF) par des équipes de soins gériatriques à domicile. Une approche par synthèse réaliste a été utilisée pour élaborer un cadre d’évaluation qui a inclus 159 références provenant de la littérature scientifique, des consultations d’experts canadiens en SAPF, des recherches ciblées dans les bases PubMed/MEDLINE® et CINAHL, et des recensions de la littérature grise canadienne. Les références ont été sélectionnées par deux personnes, selon une approche consensuelle avec évaluation de la qualité. Les données ont été extraites et synthétisées en tenant compte du contexte, des mécanismes et des configurations des résultats dans un cadre théorique de SAPF d’équipe pour les soins gériatriques à domicile. Le cadre présente les contributions spécifiques prédominantes des infirmières, des ergothérapeutes et des physiothérapeutes, leurs apports collectifs impliquant des communications pour des équipes virtuelles, ainsi que le soutien du système nécessité pour la prestation de SAPF d’équipe complets. Les résultats de cette étude pourraient contribuer à l’amélioration de l’éducation sur les SAPF et des lignes directrices sur les pratiques exemplaires, en vue d’assurer une prestation plus intégrée des SAPF dans les soins gériatriques offerts à domicile ou dans d’autres milieux comportant des équipes de soins.
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Mahmoud, Muhammad Ossama, Wael Mamdouh i Hamdy Khalil. "Source current harmonic mitigation of distorted voltage source by using shunt active power filter". International Journal of Electrical and Computer Engineering (IJECE) 10, nr 4 (1.08.2020): 3967. http://dx.doi.org/10.11591/ijece.v10i4.pp3967-3977.
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In this paper, three-phase, four-wire shunt active power filter (SAPF) is utilized to mitigate system harmonics of distorted voltage source for unbalanced and nonlinear loads. Basically, the source voltage should be pure sinusoidal waveform to get a good mitigation of source current harmonics. In this under study system, the source voltage is assumed to be harmonic distortion non-sinusoidal voltage source. The phase locked loop (PLL) control circuit is wielded for extracting the fundamental component of the distorted source voltage to use it as an input signal to the SAPF control. Another input signal to the SAPF is the distorted load current. The SAPF control system uses (p-q) theory to calculate the optimum instantaneous current to be injected by the SAPF to mitigate the source current harmonics even the source voltage is harmonic distorted. MATLAB/SIMULINK software package is utilized to simulate the system under study. The effect of SAPF is tested when it’s used with and without the PLL control circuit. The simulation results show that, the THD of source current when using the PLL control circuit is improved to comply with the harmonic limits given in the IEEE 519-1992 and IEC 61000-4-7 standards.
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Chen, Guofeng, Baoqiang Liu, Jiajun Chen, Hongyu Liu, Beiping Tan, Xiaohui Dong, Qihui Yang, Shuyan Chi, Shuang Zhang i Min Yao. "Supplementing Sulfate-Based Alginate Polysaccharide Improves Pacific White Shrimp (Litopenaeus vannamei) Fed Fishmeal Replacement with Cottonseed Protein Concentrate: Effects on Growth, Intestinal Health, and Disease Resistance". Aquaculture Nutrition 2022 (8.02.2022): 1–21. http://dx.doi.org/10.1155/2022/7132362.
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Sulfate-based alginate polysaccharide (SAP) is a novelty marine prebiotic. To investigate the beneficial effects of SAP in Pacific white shrimp (Litopenaeus vannamei) fed low-fishmeal diets, six diets (whole fishmeal group: FM; fishmeal replacement with cottonseed protein concentrate and SAP supplementary groups: SAP0, SAP1, SAP2, SAP3, and SAP4) were formulated and fed shrimp for 56 days. The results showed that SAP2 and SAP3 groups reached the best weight gain and specific growth rate ( P < 0.05 ). In serum, the activities of lysozyme and acid phosphatase showed the trend of firstly increased and then decreased ( P < 0.05 ). In the gut, the highest activities of trypsin, lipase, and amylase were found in SAP2 and SAP3 groups ( P < 0.05 ); the histological indexes gradually improved with SAP levels increased ( P < 0.05 ); sequencing of microbiota revealed that the composition and structure of microbiota have been improved, especially in the decreasing abundance of Vibrio, Pseudoalteromonas, and Candidatus Bacilloplasma at genus level. Besides, transcriptomics revealed a degree of similarity in differential gene expression patterns in shrimp; the comparison of RNA-Seq and qRT-PCR verified that SAP improved antioxidant and immunity in shrimp. The challenge revealed that SAP strengthened the resistance against Vibrio parahaemolyticus. Totally, the supplementary SAP to low-fishmeal diets improved growth, intestinal health, and disease resistance in shrimp. Based on the polynomial curve analysis of specific growth rate among SAPs groups, the optimum SAP supplementary level was 1.91%.
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Albasri, Fadhel Abbas, Sayed Ali Al-Mawsawi i Mahmood Al-Mahari. "A pot line rectiformer scheme with hybrid-shunt active power filter". International Journal of Power Electronics and Drive Systems (IJPEDS) 13, nr 1 (1.03.2022): 1. http://dx.doi.org/10.11591/ijpeds.v13.i1.pp1-10.
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Passive harmonic filters (PHF) are commonly used in conventional potline rectifier transformers (Rectiformer) schemes of aluminum smelters to improve the power quality and reduce harmonic distortions to an acceptable level. However, changes in operating conditions and system configuration affect the performance capability of PHF in attenuating harmonics. In this paper, a Rectiformer scheme with hybrid-shunt active power filter (SAPF) is used instead of PHF and compared with the other commonly applied schemes in aluminum smelter in terms of harmonic attenuation capability. The SAPF potline Rectiformer scheme and other schemes are modeled and simulated using MATLAB/Simulink. A control strategy suitable for potline load behavior is furnished in this paper for SAPF. The simulation results reveal the performance superiority of the proposed SAPF as compared to the conventional and ALBA pot line (PL) 6 schemes.
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Hoon, Yap, Mohd Amran Mohd Radzi, Muhammad Ammirrul Atiqi Mohd Zainuri i Mohamad Adzhar Md Zawawi. "Shunt Active Power Filter: A Review on Phase Synchronization Control Techniques". Electronics 8, nr 7 (15.07.2019): 791. http://dx.doi.org/10.3390/electronics8070791.
Pełny tekst źródłaStreszczenie:
Owing to the destructive impacts of harmonic currents, the topic of reducing their impacts on power system has attracted tremendous research interests. In this regard, a shunt active power filter (SAPF) is recognized to be the most reliable instrument. It performs by first detecting the harmonic currents that are present in a harmonic-contaminated power system, and subsequently generates and injects corrective mitigation current back into the power system to cancel out all the detected harmonic currents. This means that other than the ability to generate corrective mitigation current itself, it is actually more important to make sure that the SAPF is able to operate in phase with the operating power system, so that the mitigation current can correctly be injected. Hence, proper synchronization technique needs to be integrated when designing the control algorithms of SAPF. This paper critically discusses and analyzes various types of existing phase synchronization techniques which have been applied to manage operation of SAPF; in terms of features, working principle, implementation and performance. The analysis provided can potentially serve as a guideline and provision of information on selecting the most suitable technique for synchronizing SAPF with the connected power system.
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M, Sujith, Vijayakumar G, Pardeshi D. B, Madhubalan S i Arulanantham D. "ANN-SOGI-based Shunt Active Power Filter for Harmonic Mitigation". International Journal of Electrical and Electronics Research 11, nr 1 (30.03.2023): 97–102. http://dx.doi.org/10.37391/ijeer.110113.
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In this paper introduces a PV based generation system interlinked with shunt active power filter (SAPF) to provide the effective reactive power compensation and mitigation of harmonics. The SAPF is comprised of a photovoltaic generation system, DC link capacitor and voltage source inverter (VSI). The current harmonics caused by nonlinear loads can be greatly reduced with the help of active power filter. To generate the reference current and the regulation of SAPF, the artificial neural network is proposed. The Second Order Generalized Integrator (SOGI) with Artificial Neural Network (ANN) controller is engaged to calculate the reference source current for SAPF. ANN additionally boasts great compatibility for digital implementation, control performance, and lightning-fast dynamic reaction. To demonstrate the effectiveness and superior concert of the proposed methodology, the designed controller is validated with the help of MATLAB simulations.
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Gao, Yunguang, Xiaofan Li, Wenjie Zhang, Dianchao Hou i Lijun Zheng. "A Sliding Mode Control Strategy with Repetitive Sliding Surface for Shunt Active Power Filter with an LCLCL Filter". Energies 13, nr 7 (5.04.2020): 1740. http://dx.doi.org/10.3390/en13071740.
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This paper proposes a novel sliding mode control (SMC) scheme with a repetitive sliding surface for shunt active power filters (SAPF) to enhance the system robustness and eliminate harmonic current tracking errors. Traditional control schemes, such as PI control, repetitive control (RC), proportional resonance control (PR), improve the stability of the SAPF in the stable grid to a certain extent. However, the robustness of the SAPF control system has not been improved. In this paper, the SMC is applied to SAPF, and a sliding mode controller is constructed by using a linear sliding mode surface composed of the system state variables and a fast exponential power-reaching law, which can effectively enhance the system robustness. When the grid parameters change or external disturbances exist, sliding surface drift and sliding mode chattering will occur. Although fast-tracking of the harmonic current can still be achieved, it is difficult to accurately compensate AC harmonic current. Moreover, this may cause the harmonic current compensation error to be amplified. RC can achieve infinite gain at multiples of the fundamental frequency and can track inputs without static errors. In order to fully eliminate the harmonic current tracking error and effectively suppress the total harmonic distortion (THD) of the grid, the sliding mode surface was modified. An RC term of harmonic current error is introduced to the sliding mode surface, and a novel plugin-repetitive sliding mode control strategy (RCSMC) for SAPF is proposed. Finally, simulation and experiment results on the LCLCL-filter based SAPF show the effectiveness of the proposed control strategy.
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Soliman, Ahmed Mohammed Attiya, Salah Kamal El-Sayed i M. A. Mehanna. "Effect of Utility Voltage Distortion on the Performance of Different Control Strategies for Shunt Active Power Filter". European Journal of Engineering Research and Science 2, nr 8 (31.08.2017): 27. http://dx.doi.org/10.24018/ejers.2017.2.8.445.
Pełny tekst źródłaStreszczenie:
The widespread use of power electronics in industrial, commercial and even residential electrical equipment like non-linear loads causes deterioration of the quality of the electric power supply with distortion of the supply voltage and in order to mitigate this quality the shunt active power filter (SAPF) is the suitable and effective solution for harmonic elimination and reactive power compensation and lead to power quality (PQ) improvement, therefor an effective and accurate current control technique is needed in order for a SAPF where control algorithm is the heart for SAPF to perform this function and its dynamic performance is mainly depends on these control strategy. This paper proposes three different current control strategies (CCS) based on instantaneous power theory and generalized fryze theory which used for the generation or extraction of the accurate reference current signals which comparing with the actual signals through hysteresis current technique (HCT) to produce suitable gating signals for SAPF and discusses the performance for these controllers when the supply bus voltage is distorted with scope on the efficient control algorithm. Matlab / Simulink simulation results are presented to validate the control strategy and demonstrate the effectiveness of SAPF to provide mitigation of power quality problems for non-linear load to reach an acceptable value comply with recommended standards.
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Soliman, Ahmed Mohammed Attiya, Salah Kamal El-Sayed i M. A. Mehanna. "Effect of Utility Voltage Distortion on the Performance of Different Control Strategies for Shunt Active Power Filter". European Journal of Engineering and Technology Research 2, nr 8 (31.08.2017): 27–34. http://dx.doi.org/10.24018/ejeng.2017.2.8.445.
Pełny tekst źródłaStreszczenie:
The widespread use of power electronics in industrial, commercial and even residential electrical equipment like non-linear loads causes deterioration of the quality of the electric power supply with distortion of the supply voltage and in order to mitigate this quality the shunt active power filter (SAPF) is the suitable and effective solution for harmonic elimination and reactive power compensation and lead to power quality (PQ) improvement, therefor an effective and accurate current control technique is needed in order for a SAPF where control algorithm is the heart for SAPF to perform this function and its dynamic performance is mainly depends on these control strategy. This paper proposes three different current control strategies (CCS) based on instantaneous power theory and generalized fryze theory which used for the generation or extraction of the accurate reference current signals which comparing with the actual signals through hysteresis current technique (HCT) to produce suitable gating signals for SAPF and discusses the performance for these controllers when the supply bus voltage is distorted with scope on the efficient control algorithm. Matlab / Simulink simulation results are presented to validate the control strategy and demonstrate the effectiveness of SAPF to provide mitigation of power quality problems for non-linear load to reach an acceptable value comply with recommended standards.
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Manimekalai, P., R. Harikumar i S. Raghavan. "SOGI Algorithm-Based Shunt Active Power Filter for Grid Integration of Photovoltaic Systems". Journal of Circuits, Systems and Computers 25, nr 05 (25.02.2016): 1650046. http://dx.doi.org/10.1142/s0218126616500468.
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In this paper, photovoltaic (PV) system interfaced single-phase shunt active power filter (SAPF) is proposed to supply uninterrupted and clean power to small-scale industries and domestic customers. The second-order generalized integrator (SOGI) is employed to extract the reference current of PV-SAPF. The proposed topology does not need voltage measurement and sensors on both the AC and DC side, just two current sensors are accustomed to measure converter and load currents. To be able to acquire an accurate reference source current, the distorted load is only processed through the SOGI control algorithm which does not need voltage-related information. The PV interfaced SAPF mainly is used for sustainable compensation of current disturbances and voltage interruption of the single-phase distribution system. The proposed topology utilizes the PV energy with an energy storage unit to meet the active power requirement of the utility grid. Besides, it exports the power generated in the PV system to the load during unavailability of grid supply. The PV-SAPF system subject to different types of loads can assess the performance of the system under steady-state and dynamic conditions. To validate the effectiveness of the proposed controller for PV interfaced SAPF, the simulation and experimental results are presented.
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Ripeau, Jean-Sébastien, Francine Aumont, Pierre Belhumeur, Luis Ostrosky-Zeichner, John H. Rex i Louis de Repentigny. "Effect of the Echinocandin Caspofungin on Expression of Candida albicans Secretory Aspartyl Proteinases and Phospholipase In Vitro". Antimicrobial Agents and Chemotherapy 46, nr 9 (wrzesień 2002): 3096–100. http://dx.doi.org/10.1128/aac.46.9.3096-3100.2002.
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ABSTRACT Although the echinocandin caspofungin primarily inhibits the synthesis of cell wall 1,3-β-d-glucan, its fungicidal activity could also potentially perturb the expression of virulence factors involved in the ability of Candida albicans to cause infection. Expression of the C. albicans secretory aspartyl proteinase (SAP) and phospholipase B (PLB) virulence genes was determined by reverse transcription-PCR after the addition of caspofungin to cells grown for 15 h in Sabouraud dextrose broth. In cells that remained viable, expression of SAP1 to SAP3, SAP7 to SAP9, and PLB1 was unaltered after exposure to fungicidal concentrations (4 to 16 μg/ml) of caspofungin over a period of 7 h. However, expression of SAP5 increased steadily beginning 1 h after exposure to caspofungin. These results indicate that caspofungin is rapidly fungicidal against C. albicans, before any suppression of SAP or PLB1 gene expression can occur.
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Chen, Cheng-I., Yeong-Chin Chen i Chung-Hsien Chen. "Recurrent Wavelet Fuzzy Neural Network-Based Reference Compensation Current Control Strategy for Shunt Active Power Filter". Energies 15, nr 22 (19.11.2022): 8687. http://dx.doi.org/10.3390/en15228687.
Pełny tekst źródłaStreszczenie:
The usage of a shunt active power filter (SAPF) is one of the helpful means to mitigate the reactive power and harmonic current of a power grid. The compensation performance of the SAPF is related to the accuracy of the reference voltage extraction from the utility grid, the control stability of the DC-link voltage regulation, and the synchronization between the source voltage and the reference compensation current. To modify the performance of the SAPF for the harmonic compensation, the control strategy of the SAPF reference compensation current based on the recurrent wavelet fuzzy neural network (RWFNN) is proposed in this paper. There are three sections in the proposed control strategy, including the regulated fundamental positive-sequence extraction (section A), DC-link voltage regulation (section B), and calculation of reference compensation current (section C). By regulating the analysis mechanism with the variation of fundamental frequency in the section A, the accurate reference voltage would be obtained. The control stability for the regulation of the DC-link voltage can be accomplished by applying the RWFNN-based controller in the section B. With the synchronized reference voltage in the section A and the estimated control current in the section B, the reference compensation current can be correctly obtained in the section C. From the case studies with the real-time simulator produced by OPAL-RT Technologies Inc., the effectiveness of proposed control strategy for the SAPF reference compensation current can be verified.
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Wu, Ke, Yunhao Jiang i Ruoxuan Li. "Active Power Filter LCL Filter Novel Interface Control Scheme Analysis". Journal of Physics: Conference Series 2310, nr 1 (1.10.2022): 012067. http://dx.doi.org/10.1088/1742-6596/2310/1/012067.
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Abstract Shunt active power filter (SAPF) has been widely used in active distribution network system. Improving the compensation performance of SAPF has become the focus of many scholars. The traditional filter interface usually adopts series resistance. In order to reduce the loss of damping resistance and ensure the compensation performance of SAPF, a new type of passive interface is adopted, and the double-loop control scheme of PI control combined with repeated control is adopted. By comparing the difference of the selected points of different feedback currents, when the feedback current is taken from the inverter, only a small damping resistance is needed to achieve good steady-state accuracy. Simulation results verify the correctness and effectiveness of the proposed scheme and the system feedback current selection method.
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Zhou, Xue Song, Wei Liu i You Jie Ma. "Construction and Detection Algorithm of SAPF". Applied Mechanics and Materials 641-642 (wrzesień 2014): 1260–63. http://dx.doi.org/10.4028/www.scientific.net/amm.641-642.1260.
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Harmonics of power system seriously affected the quality of electric power. Shunt Active Power Filter (SAPF) [1] which overcomes the shortcomings of passive filter (PF) has become main technology to suppress harmonic. In this paper, structure, mathematic model, detection method and control of SAPF are mainly analyzed and reviewed. With development of key technology of APF, it will have a better application prospect.
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Mumtaz, Fahmi Naufala, Indhana Sudiharto i Ony Asrarul Qudsi. "Shunt Active Power Filter Untuk Peredaman Harmonisa Pada Inverter V/F Konstan Pengatur Kecepatan Motor Induksi Tiga Fasa". JTT (Jurnal Teknologi Terpadu) 9, nr 2 (8.11.2021): 131–41. http://dx.doi.org/10.32487/jtt.v9i2.1176.
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Pengemudian elektrik untuk motor induksi tiga fasa mampu menghemat biaya operasional di industri. Metode V/F konstan adalah pengaturan yang hanya mengatur besaran tegangan dan frekuensi pada motor induksi tiga fasa. Pada saat yang sama, inverter V/F konstan dapat menyebabkan harmonisa pada saat melakukan pengemudian elektrik dan harmonisa ini akan mengurangi faktor daya dengan meningkatkan total harmonic distortion (THD). Kehadiran harmonisa dalam sistem dapat berdampak negatif pada sistem tenaga dan dapat berpotensi merusak peralatan. Dalam artikel ini diusulkan suatu filter aktif yang mampu mengurangi harmonisa pada inverter V/F pengatur kecepatan motor. Filter aktif yang digunakan adalah jenis shunt active power filter (SAPF) dengan pengontrol injeksi arus berupa PWM Hysteresis Current Control dan pengontrol DC-link Voltage menggunakan Fuzzy Logic Controller (FLC). Hasil simulasi menunjukkan bahwa sebelum pemasangan SAPF, nilai THDi yang dihasilkan oleh inverter V/F masih belum memenuhi standar yang ditoleransi oleh IEEE 519 yaitu kurang dari 5%. Ketika menggunakan PI-SAPF, THDi yang dihasilkan bisa kurang dari 2,75% baik pada motor 370 W, 4000 W, maupun 7500 W. Sedangkan FLC-SAPF dapat meredam harmonisa lebih baik lagi, THDi yang dihasilkan kurang dari 0,6% baik pada motor 370 W, 4000 W, maupun 7500 W.
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Othman, Sana, Mohamad Alaaeddin Alali, Lassaad Sbita, Jean-Pierre Barbot i Malek Ghanes. "Modeling and Control Design Based on Petri Nets Tool for a Serial Three-Phase Five-Level Multicellular Inverter Used as a Shunt Active Power Filter". Energies 14, nr 17 (27.08.2021): 5335. http://dx.doi.org/10.3390/en14175335.
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In this work, we represent a shunt active power filter (SAPF) based on a serial three-phase flying capacitor multilevel inverter (FCMI) controlled by a Petri Nets representation (PNs). This structure is chosen for its significant performances. In fact, the use of the FCMI within the SAPF makes it possible to increase the apparent switching frequency of the structure in order to reduce the value then the volume and weight of the inductance of the output filter. Besides, the FCMI allows the synthesis of a high-voltage signal using low-voltage semiconductor components. Therefore, improving the reliability of this structure leads to the improvement of the dynamics of the SAPF. This paper deals with a new control methodology based on PNs to regulate the flying capacitor voltages and the reference currents issued by the instantaneous active and reactive power theory. Compared to a conventional SAPF composed by a classical two-level inverter and controlled by a simple PWM control, simulation results demonstrate that our proposed control enhances the dynamic system and the power quality by reducing the total harmonic distortion (THD) satisfying the limits of IEEE standards.
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Akintade, S. A., Y. Jibril i A. S. Abubakar. "Development of Shunt Active Power Filter for Harmonic Reduction using Synchronous Reference Frame with Space Vector Pulse Width Modulation". Nigerian Journal of Technological Development 17, nr 2 (22.07.2020): 104–12. http://dx.doi.org/10.4314/njtd.v17i2.5.
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The work aims at development of Shunt Active Power Filter (SAPF) for harmonic reduction. The current harmonics are being caused by nonlinear characteristic of power electronics based equipments which increase power losses and in turn reduce power quality. Synchronous Reference Frame (SRF) was used as a control strategy and for reference harmonic current generation and Space Vector Pulse Width Modulation (SVPWM) was adopted as switching signal generation. With RL load under balanced input voltage condition, the developed SAPF-SVPWM achieved a reduction of THD of 0.91% as compared to 25.60 before compensation. In addition, the developed SAPF- SVPWM model was compared with SAPF without compensation using RL load under unbalanced voltage and the result shows that the developed SVPWM achieved reduction in THD of 1.74 % as compared to 26.68% after and before compensation. The developed SVPWM model was also compared with SPWM balanced and unbalanced voltage condition. The results show that SVPWM performed better than SPWM. All the results obtained are within IEEE 519 harmonics standard (i.e. THD less than 5%) with nonlinear load under balanced and unbalanced voltage.
Keywords: Shunt active filter, input voltage, harmonics, space vector pulse width modulation, nonlinear load.
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Hoon, Yap, i Mohd Mohd Radzi. "PLL-Less Three-Phase Four-Wire SAPF with STF-dq0 Technique for Harmonics Mitigation under Distorted Supply Voltage and Unbalanced Load Conditions". Energies 11, nr 8 (17.08.2018): 2143. http://dx.doi.org/10.3390/en11082143.
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This paper presents a non-iterative technique that generates reference current to manage operation of a three-phase four-wire shunt active power filter which employs a three-leg split capacitor voltage source inverter (VSI) topology. The proposed technique integrates together a self-tuning-filter (STF) and direct-quadrature-zero (dq0) principle (referred here as STF-dq0), allowing the controlled shunt active power filter (SAPF) to perform effectively under distorted source voltages and unbalanced load conditions. Unlike the previous technique developed based on the standard dq0 principle, the proposed technique does not require any service from a phase-locked loop (PLL) where two STFs are applied to separate harmonic and fundamental elements for the purpose of generating synchronization phases and reference current, respectively. Simulation work which includes connection of the SAPF circuits, design of control techniques and all the necessary assessments are conducted in MATLAB-Simulink platform. Performance achieved by the SAPF while utilizing the proposed technique is thoroughly investigated and benchmarked with that demonstrated by the SAPF while using the standard dq0 technique, to evaluate the inherent advantages. Exhaustive simulation results are provided and thoroughly discussed to support design concept, effectiveness, and benefits of the proposed technique.
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Tounsi, Mahmoud Mostefa, Ahmed Allali, Houari Merabet Boulouiha i Mouloud Denaï. "ANFIS control of a shunt active filter based with a five-level NPC inverter to improve power quality". International Journal of Electrical and Computer Engineering (IJECE) 11, nr 3 (1.06.2021): 1886. http://dx.doi.org/10.11591/ijece.v11i3.pp1886-1893.
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This paper addresses the problem of power quality, and the degradation of the current waveform in the distribution network which results directly from the proliferation of the nonlinear loads. We propose to use a five-level neutral point clamped (NPC) inverter topology for the implementation of the shunt active filter (SAPF). The aim of the SAPF is to inject harmonic currents in phase opposition at the connection point. The identification of harmonics is based on the pq method. A neuro-fuzzy controller based on ANFIS (adaptive neuro fuzzy inference system) is designed for the SAPF. The simulation study is carried out using MATLAB/Simulink and the results show a significant improvement in the quality of energy and a reduction in total harmonic distortion (THD) in accordance with IEC standard, IEEE-519, IEC 61000, EN 50160.
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Ye, Sen, Youbing Zhang, Luyao Xie i Haiqiang Lu. "Shunt Active Power Filter Based on Proportional Integral and Multi Vector Resonant Controllers for Compensating Nonlinear Loads". Journal of Electrical and Computer Engineering 2018 (3.09.2018): 1–11. http://dx.doi.org/10.1155/2018/1312064.
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The current tracking control strategy determines the compensation performance of shunt active power filter (SAPF). Due to inadequate compensation of the main harmonic by traditional proportional integral (PI) control, a control algorithm based on PI and multi vector resonant (VR) controllers is proposed to control SAPF. The mathematical model of SAPF is built, and basic principle of VR controller is introduced. Under the synchronous reference frame, the proposed control method based on pole zero cancellation is designed, which narrows the order of the control system and improves the system dynamic response and the control accuracy. Then the feasibility of the method is demonstrated by analyzing the closed loop frequency characteristics of the system. Finally, the simulation and experimental results are carried out to verify the performance of the proposed method.
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Hoon, Yap, Mohd Amran Mohd Radzi, Mohd Khair Hassan i Nashiren Farzilah Mailah. "Enhanced Instantaneous Power Theory with Average Algorithm for Indirect Current Controlled Three-Level Inverter-Based Shunt Active Power Filter under Dynamic State Conditions". Mathematical Problems in Engineering 2016 (2016): 1–12. http://dx.doi.org/10.1155/2016/9682512.
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An enhanced harmonics extraction algorithm based on Instantaneous Power (PQ) Theory is proposed for indirect current controlled (ICC) three-level neutral point diode clamped (NPC) inverter-based shunt active power filter (SAPF). SAPF is famous in current harmonics mitigation for its flexibility in dealing with dynamic state conditions. As for its controller, PQ Theory has served the major role in harmonics extraction algorithm due to its simple implementation features. However, it suffers from serious time delay due to its dependency on sluggish numerical filters. Furthermore, the algorithm is mostly designed to suit the operation of direct current controlled (DCC) SAPF which requires the knowledge of actual SAPF current (injection current). This leads to inaccurate mitigation as the injection current does not possess the exact information on actual source current which suffers from switching ripples problems. Therefore, two major modifications are introduced involving the development of mathematical average algorithm to replace numerical filter for fundamental real power computation and the formation of mathematical current relationship to change DCC to ICC based operation. The proposed algorithm is developed and evaluated in MATLAB/Simulink. From the simulation results, significant improvement in terms of Total Harmonic Distortion (THD) and response time is presented in comparison to conventional algorithm.
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Benhamadouche, Abdelouahab Djoubair, Abdeslem Sahli, Haddi Bakhti, Adel Ballouti i Mahmoud Drif. "Enhanced FPGA-Based Controller for Three Phase Shunt Active Power Filter". Power Electronics and Drives 8, nr 1 (1.01.2023): 128–41. http://dx.doi.org/10.2478/pead-2023-0010.
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Abstract In this paper, a three-phase shunt active power filter (SAPF) controller with a fully digital implementation is presented. The main goal of this contribution is to implement a digital direct power control (DDPC) algorithm without phase-locked-loop (PLL) for SAPF. This algorithm is intended for power quality improvement and current harmonic elimination. The controller introduced in this paper is cost-effective, has a fast-dynamic response, and has a simple hardware implementation. In order to comply with the above specifications, a dedicated controller has been conceived and fully implemented within a field-programmable gate array (FPGA) device. This FPGA-based controller integrates the whole signal-processing functions needed to drive the SAPF, as well as an original method for sector identification. The intended controller provides the desired power references to select the optimal switching sequences. The switching orders follow the grid reference to drive the voltage source inverter (VSI), so the SAPF achieves good performances while ensuring balanced overall supply currents, unity power factor, and reduced harmonic load currents. The proposed digital implementation achieves a valuable compromise between fast dynamic response, minimum execution time, and reduced FPGA resources, through a simple hardware design implementation. The entire system is developed and simulated using VHDL and VHDL-AMS languages.
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Nikkhah Kashani, Hoda, Reza Rouhi Ardeshiri, Meysam Gheisarnejad i Mohammad-Hassan Khooban. "Optimal Cascade Non-Integer Controller for Shunt Active Power Filter: Real-Time Implementation". Designs 6, nr 2 (1.04.2022): 32. http://dx.doi.org/10.3390/designs6020032.
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Active power filters (APFs) are used to mitigate the harmonics generated by nonlinear loads in distribution networks. Therefore, due to the increase of nonlinear loads in power systems, it is necessary to reduce current harmonics. One typical method is utilizing Shunt Active Power Filters (SAPFs). This paper proposes an outstanding controller to improve the performance of the three-phase 25-kVA SAPF. This controller can reduce the current total harmonic distortion (THD), and is called fractional order PI-fractional order PD (FOPI-FOPD) cascade controller. In this study, another qualified controller was applied, called multistage fractional order PID controller, to show the superiority of the FOPI-FOPD cascade controller to the multistage FOPID controller. Both controllers were designed based on a non-dominated sorting genetic algorithm (NSGA-II). The obtained results demonstrate that the steady-state response and transient characteristics achieved by the FO (PI + PD) cascade controller are superior to the ones obtained by the multistage FOPID controller. The proposed controller was able to significantly reduce the source current THD to less than 2%, which is about a 52% reduction compared to the previous work in the introduction. Finally, the studied SAPF system with the proposed cascade controller was developed in the hardware-In-the Loop (HiL) simulation for real-time examinations.
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Djendaoui, Dahmane, Amar Benaissa, Boualaga Rabhi i Laid Zellouma. "Self tunning filter for three levels four legs shunt active power filter with fuzzy logic controller". Acta Polytechnica 61, nr 3 (30.06.2021): 415–27. http://dx.doi.org/10.14311/ap.2021.61.0415.
Pełny tekst źródłaStreszczenie:
The low harmonic distortion and reduced switching losses are the advantages of using the multilevel inverter. For this purpose, the three-level inverter is used in this paper as a three-phase four-leg shunt active power filter (SAPF). The SAPF is used to eliminate the harmonic current to compensate the reactive power current, and to balance the load currents under an unbalanced non-linear load. A fuzzy logic controller and self-tuning filters (STF) are used to control the active power filter (APF) and generate the reference current. To demonstrate the validity of the proposed control strategy, we compared it with a conventional p − q theory, under distortion voltage conditions and unbalanced non-linear load. The Matlab-Simulink toolbox is used to implement the algorithm of Fuzzy logic control. The performance of the SAPF controller is found very effective and adequate as compared with the p − q theory.
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Tandekar, Jitendra, Amit Ojha i Shailendra Jain. "Five-Level Cascaded H-Bridge MLC-Based Shunt Active Power Filter for Active Harmonics Mitigation in Distributed Network". Journal of Circuits, Systems and Computers 28, nr 02 (12.11.2018): 1950035. http://dx.doi.org/10.1142/s021812661950035x.
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This paper presents an investigation on mitigation of current harmonics, using Cascaded H-bridge Multilevel Converter (CHB-MLC)-based Shunt Active Power Filter (SAPF). Development and analysis of SAPF for harmonic compensation in distribution network for power quality improvement has been discussed. In the proposed work, transformer-less CHB MLC is used which reduces weight and cost of the system. Moreover, a novel controller based on average power method is adopted for generation of compensation active filter current. In order to generate switching signals, multi-carrier Alternate Phase Opposition Disposition (APOD) — Pulse Width Modulation (PWM) schemes are used. The proposed CHB-MLC SAPF reduces the source current THD below 5%. The results are simulated in MATLAB/Simulink and demonstrate the effective mitigation of current harmonics with APOD-PWM schemes. Opal-RT OP4500 real-time digital simulator is used to validate the proposed scheme under different steady state and transient conditions.
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Al-Ogaili, Ali Saadon, Agileswari Ramasamy, Yap Hoon, Renuga Verayiah, Marayati Marsadek, Tengku Juhana i Nur Azzammudin Rahmat. "Time-domain harmonic extraction algorithms for three-level inverter-based shunt active power filter under steady-state and dynamic-state conditions-an evaluation study". International Journal of Electrical and Computer Engineering (IJECE) 10, nr 6 (1.12.2020): 5609. http://dx.doi.org/10.11591/ijece.v10i6.pp5609-5620.
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Power quality is a major consideration in all office equipment, manufacturies and residential home appliances. Harmonic distortion is one of the crucial power quality issues. In order to mitigate the harmonic distortion, the performance of shunt active power filter (SAPF) is judged in terms of the accuracy and response time of its designed controller. In this context, the controller consists of three parts: harmonic extraction, switching control, and DC-link capacitor. The harmonic extraction technique serves the major role of deriving the required reference current to ensure successful mitigation of current harmonics by SAPF. Among the existing techniques, harmonic extraction algorithms based on time-domain approaches are most widely applied as they offer simple implementation features with increased speed and reduced computational burden. This paper presents detailed investigation and analysis regarding the performance of two famous time-domain harmonic extraction techniques namely, synchronous reference frame (SRF) and instantaneous power (PQ) theory. Extensive simulation work is conducted in MATLAB-Simulink platform under two conditions, which are, steady-state conditions and dynamic-state conditions, considering various highly nonlinear loads. For evaluation purposes, each control algorithm is incorporated into the controller of a three-phase SAPF, developed using a three-level neutral-point-clamped (NPC) inverter. Comprehensive results are provided to confirm mitigation performance of the SAPF utilizing each harmonic extraction algorithm.
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Arrich, Jasmin, i Frank M. Brunkhorst. "SAPF – eine seltene, aber schwere Komplikation". intensiv 27, nr 03 (maj 2019): 153–55. http://dx.doi.org/10.1055/a-0873-0348.
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ZusammenfassungVon der Sepsis-assoziierten Purpura fulminans sind überwiegend Kinder zwischen einem und drei Jahren und Jugendliche zwischen 16 und 18 Jahren betroffen. Eine frühe Diagnose ist auch deswegen so wichtig, damit die Wahrscheinlichkeit einer Amputation so gering wie möglich gehalten wird.
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Ali, Hazem Hassan, Nashwa Ahmad Kamal i Ghada Saeed Elbasuony. "Two-Level Grid-Side Converter-Based STATCOM and Shunt Active Power Filter of Variable-Speed DFIG Wind Turbine-Based WECS Using SVM for Terminal Voltage". International Journal of Service Science, Management, Engineering, and Technology 12, nr 2 (marzec 2021): 169–202. http://dx.doi.org/10.4018/ijssmet.2021030110.
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Regulation of the terminal voltage of doubly fed induction generator (DFIG)-based wind energy conversion system (WECS) by modifying the control scheme of the grid side converter (GSC) is necessary compared to connecting alone flexible AC transmission systems (FACTS) and active power filter devices from economic point of view. An assessment study of GSC control strategy based both of static synchronous compensator (STATCOM) and shunt active power filter (SAPF) is introduced in this paper. STATCOM based AC voltage magnitude regulator and SAPF-based load calculations are controlled using space vector modulation (SVM) technique to maintain the terminal voltage of DFIG wind turbine constant when a grid disturbance happened. The system under study is modeled in MATLAB/Simulink environment. The simulation results under wind speed variation demonstrated that GSC-based STATCOM gives better results in regulation of the terminal voltage of DFIG compared to GSC-based SAPF and enhancement of the stability of this system.
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Gherouat, Oussama, Abdelouahab Hassam, Oualid Aissa i Badreddine Babes. "Experimental Evaluation of Single-Phase Shunt Active Power Filter Based on Optimized Synergetic Control Strategy for Power Quality Enhancement". Journal Européen des Systèmes Automatisés 54, nr 4 (31.08.2021): 649–59. http://dx.doi.org/10.18280/jesa.540415.
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In this paper, a synergetic approach based on particle swarm optimization (SC-PSO) technique is proposed for Single-Phase Shunt Active Power Filter (SP-SAPF). Two-loop cascade controller for SP-SAPF has been designed. In the first loop, a PI controller is used to effectively regulate the DC link voltage. In the second one, a synergetic controller is performed in the current compensation control loop. The various adjustable parameters of the studied synergetic controller are tuned by a PSO algorithm. The objective of this adjustment is to get the optimal control parameters for satisfying requirements of power quality and high dynamic responses for SP-SAPF. The effectiveness of the suggested SC-PSO approach has been proved by simulation and experimental tests using MATLAB/Simulink environment and dSPACE 1104 card for several operating conditions. The experimental results demonstrate that the developed SC-PSO approach is very satisfactory and offers a high performance for both transient and steady states.
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Patel, Pritam, Sarita Samal, Chitralekha Jena i Prasanta Kumar Barik. "Harmonic Mitigation in a Hybrid Power System Integrated Shunt Active Power Filter Employing FLC and an Adaptive Current Control Technique". ECTI Transactions on Electrical Engineering, Electronics, and Communications 21, nr 1 (28.02.2023): 248667. http://dx.doi.org/10.37936/ecti-eec.2023211.248667.
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The main objective of this study is to mitigate current harmonic issues in hybrid renewable energy systems based on solar photovoltaic (SPV) and wind energy distribution. This is achieved with the help of a suitable controller-based shunt active power filter (SAPF). The SAPF is designed using a modified synchronous reference frame (MSRF) to reference current generation, an adaptive hysteresis current controller (AHCC) for switching pulse generation, and a fuzzy logic controller (FLC) for DC-link voltage regulation. The results of the proposed SAPF model developed in MATLAB/Simulink, show that the filter performs remarkably well in suppressing harmonics under different loading conditions. It is capable of fast corrective action under dynamic conditions and outperforms previous methods in terms of harmonic mitigation and dc-link voltage stabilization. The control techniques are compared on the basis of parameters such as harmonic compensation and dc-link voltage ripple reduction capability under changing load conditions. The results obtained through simulation represent the validity of the filter performance.
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Taylor, Brad N., Peter Staib, Ayfer Binder, Antje Biesemeier, Miriam Sehnal, Martin Röllinghoff, Joachim Morschhäuser i Klaus Schröppel. "Profile of Candida albicans-Secreted Aspartic Proteinase Elicited during Vaginal Infection". Infection and Immunity 73, nr 3 (marzec 2005): 1828–35. http://dx.doi.org/10.1128/iai.73.3.1828-1835.2005.
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ABSTRACT Vaginal infections caused by the opportunistic yeast Candida albicans are a significant problem in women of child-bearing age. Several factors are recognized as playing a crucial role in the pathogenesis of superficial candidiasis; these factors include hyphal formation, phenotypic switching, and the expression of virulence factors, including a 10-member family of secreted aspartic proteinases. In the present investigation, we analyzed the secreted aspartic proteinase gene (SAP) expression profile of C. albicans that is elicited in the course of vaginal infection in mice and how this in vivo expression profile is associated with hyphal formation. We utilized two different genetic reporter systems that allowed us to observe SAP expression on a single-cell basis, a recombination-based in vivo expression technology and green fluorescent protein-expressing Candida reporter strains. Of the six SAP genes that were analyzed (SAP1 to SAP6), only SAP4 and SAP5 were detectably induced during infection in this model. Expression of both of these genes was associated with hyphal growth, although not all hyphal cells detectably expressed SAP4 and SAP5. SAP5 expression was induced soon after infection, whereas SAP4 was expressed at later times and in fewer cells compared with SAP5. These findings point to a link between morphogenetic development and expression of virulence genes during Candida vaginitis in mice, where host signals induce both hyphal formation and expression of SAP4 and SAP5, but temporal gene expression patterns are ultimately controlled by other factors.
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Pietrella, Donatella, Anna Rachini, Neelam Pandey, Lydia Schild, Mihai Netea, Francesco Bistoni, Bernhard Hube i Anna Vecchiarelli. "The Inflammatory Response Induced by Aspartic Proteases of Candida albicans Is Independent of Proteolytic Activity". Infection and Immunity 78, nr 11 (16.08.2010): 4754–62. http://dx.doi.org/10.1128/iai.00789-10.
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ABSTRACT The secretion of aspartic proteases (Saps) has long been recognized as a virulence-associated trait of the pathogenic yeast Candida albicans. In this study, we report that different recombinant Saps, including Sap1, Sap2, Sap3, and Sap6, have differing abilities to induce secretion of proinflammatory cytokines by human monocytes. In particular Sap1, Sap2, and Sap6 significantly induced interleukin-1β (IL-1β), tumor necrosis factor alpha (TNF-α), and IL-6 production. Sap3 was able to stimulate the secretion of IL-1β and TNF-α. All Saps tested were able to induce Ca2+ influx in monocytes. Treatment of these Saps with pepstatin A did not have any effect on cytokine secretion, indicating that their stimulatory potential was independent from their proteolytic activity. The capacity of Saps to induce inflammatory cytokine production was also independent from protease-activated receptor (PAR) activation and from the optimal pH for individual Sap activity. The interaction of Saps with monocytes induced Akt activation and phosphorylation of IκBα, which mediates translocation of NF-κB into the nucleus. Overall, these results suggest that individual Sap proteins can induce an inflammatory response and that this phenomenon is independent from the pH of a specific host niche and from Sap enzymatic activity. The inflammatory response is partially dependent on Sap denaturation and is triggered by the Akt/NF-κB activation pathway. Our data suggest a novel, activity-independent aspect of Saps during interactions of C. albicans with the host.
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Abdelkhalek, Othmane, Mohammed Amine Soumeur, Oussama Hafsi i Abdeselem Chakar. "Simulation and experimental validation of single-phase series active power filter using PI and backstepping nonlinear controllers". International Journal of Applied Power Engineering (IJAPE) 9, nr 1 (1.04.2020): 78. http://dx.doi.org/10.11591/ijape.v9.i1.pp78-88.
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<p>Nowadays, power distribution networks are focus mainly on power quality issues. Among the power disturbances, sag, swell and voltage harmonics are studied and deliberated in this research paper. These problems have negative impacts especially on the sensitive load, which have to be protected and secured against these problems. Therefore, to solve such disturbances, the series active power filter (SAPF) can be an efficient solution, which is used to compensate the voltage difference and to reduce the problem’s effects on the power system. In this paper, the SAPF is simulated and experimentally validated, where two control methods are used to control the applied disturbances; which are classical proportional integral PI and nonlinear backstepping controllers. The control structure of the SAPF aims to reduce the error of the injection voltage closed loop, in addition to reduce the total harmonic distortion (THD) values below 5% and within the specified ranges of the international IEEE-519 standard. From simulation results, the backstepping nonlinear controller has reacted more robustly and efficiently than the conventional PI controller.</p>
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Sulehri, Abdul Mutal. "Power quality improvement in an AC network using artificial neural network and hysteresis band current controller". Ingeniería e Investigación 38, nr 3 (1.09.2018): 42–49. http://dx.doi.org/10.15446/ing.investig.v38n3.67885.
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This paper demonstrates a study to improve the total harmonic distortion (THD) originated due to excessive use of power electronic (PE) equipment and non-linear loads. Shunt active power filter (SAPF) is used to mitigate the harmonics from the system because it has the capability of minimizing the harmonic problems initiated by non-linear loads. The instantaneous reactive power (IRP) p-q theory is used for the generation of reference signal and for the extraction of compensating components of the current. The proportional integral (PI) controller and artificial neural network (ANN) have been employed in the DC-link controller and for current errors adjustments. In this paper, both conventional hysteresis and adaptive hysteresis band current controller (HBCC) have been used for the generation of gate pulses for the SAPF, which reduces THD in the source current to a value within IEEE specified standards, without any phase error over the extensive range of adaptive HBCC strategy. Simulation results confirm that the SAPF with HBCC and ANN performs the harmonic mitigation efficiently and maintains power factor (PF) close to unity.
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Wang, Guifeng, Xujie Gao i Chunjie Li. "An FCS-MPC Strategy for Series APF Based on Deadbeat Direct Compensation". Energies 16, nr 5 (6.03.2023): 2507. http://dx.doi.org/10.3390/en16052507.
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Aiming at the delay caused by the phase-locked loop (PLL) and harmonic detection in the traditional control of a series active power filter (SAPF), a deadbeat direct control (DBDC)-based finite control set model predictive control (FCS-MPC) strategy for the SAPF is proposed in this work. Firstly, a reference voltage generation mechanism based on direct control is established, which avoids the delay in harmonic detection, thus improving the dynamic response performance of the system. Secondly, the reference current generation mechanism suitable for the SAPF is derived and established using the deadbeat control (DBC) in the αβ coordinate system, based on which the FCS-MPC system is constructed. It eliminates the complex coordinate transformation and PLL and effectively compensates for the full-frequency harmonic voltage. Finally, the proposed control strategy is verified by a simulation and an experiment. The results suggest that the proposed control strategy can effectively compensate for the load voltage and suppress harmonic distortion for the temporary swell and sag of the grid voltage, sudden load changes, and harmonic distortion conditions.