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Ke Wang,Yi Tang,Xiao Zhang,Yang Wang,Chuan-Jin Zhang,Hui Zhang 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.5
A novel open-circuit fault diagnosis method for 3-phase 4-wire 3-level active power filters based on voltage error correlation is proposed in this paper. This method is based on observing the output pole voltage error of the active power filter through two kinds of algorithms. One algorithm is a voltage error analytical algorithm, which derives four output voltage error analytic expressions through the pulse state, current value and dc bus voltage, respectively, assuming that all of the IGBTs of a certain phase come to an OC fault. The other algorithm is a current circuit equation algorithm, which calculates the real-time output voltage error through basic circuit theory. A correlation is introduced to measure the similarity of the output voltage errors between the two algorithms, and OC faults are located by the maximum of the correlations. A FPGA has been chosen to implement the proposed method due to its fast prototyping. Simulation and experimental results are presented to show the performance of the proposed OC fault diagnosis method.
Zhang, Chuan-Jin,Tang, Yi,Han, Dong,Zhang, Hui,Zhang, Xiao,Wang, Ke The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.3
A novel Virtual Space Vector (VSV) modulation strategy for complete control of potential neutral point (NP) issues is proposed in this paper. The neutral point potential balancing problems of multi-level converters, which include elimination of low frequency oscillations and self-balancing for NP dc unbalance, are investigated first. Then a set of improved virtual space vectors with dynamic adjustment factors are introduced and a multi-objective optimization algorithm which aims to optimize these adjustment factors is presented in this paper. The improved virtual space vectors and the multi-objective optimization algorithm constitute the novel Virtual Space Vector modulation. The proposed novel Virtual Space Vector modulation can simultaneously recover NP dc unbalance and eliminate low frequency oscillations of the neutral point. Experiment results show that the proposed strategy has excellent performance, and that both of the neutral point potential issues can be solved.
Chuan-Jin Zhang,Yi Tang,Dong Han,Hui Zhang,Xiao Zhang,Ke Wang 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.3
A novel Virtual Space Vector (VSV) modulation strategy for complete control of potential neutral point (NP) issues is proposed in this paper. The neutral point potential balancing problems of multi-level converters, which include elimination of low frequency oscillations and self-balancing for NP dc unbalance, are investigated first. Then a set of improved virtual space vectors with dynamic adjustment factors are introduced and a multi-objective optimization algorithm which aims to optimize these adjustment factors is presented in this paper. The improved virtual space vectors and the multi-objective optimization algorithm constitute the novel Virtual Space Vector modulation. The proposed novel Virtual Space Vector modulation can simultaneously recover NP dc unbalance and eliminate low frequency oscillations of the neutral point. Experiment results show that the proposed strategy has excellent performance, and that both of the neutral point potential issues can be solved.
Wang, Ke,Tang, Yi,Zhang, Xiao,Wang, Yang,Zhang, Chuan-Jin,Zhang, Hui The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.5
A novel open-circuit fault diagnosis method for 3-phase 4-wire 3-level active power filters based on voltage error correlation is proposed in this paper. This method is based on observing the output pole voltage error of the active power filter through two kinds of algorithms. One algorithm is a voltage error analytical algorithm, which derives four output voltage error analytic expressions through the pulse state, current value and dc bus voltage, respectively, assuming that all of the IGBTs of a certain phase come to an OC fault. The other algorithm is a current circuit equation algorithm, which calculates the real-time output voltage error through basic circuit theory. A correlation is introduced to measure the similarity of the output voltage errors between the two algorithms, and OC faults are located by the maximum of the correlations. A FPGA has been chosen to implement the proposed method due to its fast prototyping. Simulation and experimental results are presented to show the performance of the proposed OC fault diagnosis method.
Chuan-Jin Zhang,Rui-Peng Wei,Yi Tang,Ke Wang 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.5
A novel space vector modulation strategy in the non-orthogonal three-dimensional coordinate system for multi-level three-phase four-wire inverters is proposed in this paper. This new non-orthogonal three-dimensional space vector modulation converts original trigonometric functions in the orthogonal three-dimensional space coordinate into simple algebraic operations, which greatly reduces the algorithm complexity of three-dimensional space vector modulation and preserves the independent control of the zero-sequence component. Experimental results have verified the correctness and effectiveness of the proposed three-dimensional space vector modulation in the new non-orthogonal three-dimensional coordinate system.
Ke Wang,Hong-Lu Zhao,Yi Tang,Xiao Zhang,Chuan-Jin Zhang 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.2
The fact that the reliability of IGBTs has become a more and more significant aspect of power converters has resulted in an increase in the research on the open circuit (OC) fault location of IGBTs. When an OC fault occurs, a zero-current phenomena exists and frequently appears, which can be found in a lot of the existing literature. In fact, fault variables have a very high correlation with the zero-current interval. In some cases, zero-current interval actually decides the most significant fault feature. However, very few of the previous studies really explain or prove the zero-current phenomena of the fault current. In this paper, the zero-current phenomena is explained and verified through mathematical derivation, based on two-level and three-level NPC static var generators (SVGs). Mathematical models of single OC fault are deduced and it is concluded that a zero-current interval with a certain length follows the OC faults for both two-level and NPC three-level SVGs. Both inductive and capacitive reactive power situations are considered. The unbalanced load situation is discussed. In addition, simulation and experimental results are presented to verify the correctness of the theoretical analysis.
Physical properties and chemical composition of the cores in the California molecular cloud
Zhang, Guo-Yin,Xu, Jin-Long,Vasyunin, A. I.,Semenov, D. A.,Wang, Jun-Jie,Dib, Sami,Liu, Tie,Liu, Sheng-Yuan,Zhang, Chuan-Peng,Liu, Xiao-Lan,Wang, Ke,Li, Di,Wu, Zhong-Zu,Yuan, Jing-Hua,Li, Da-Lei,Gao, Springer-Verlag 2018 Astronomy and astrophysics Vol.620 No.-
<P><I>Aims.</I> We aim to reveal the physical properties and chemical composition of the cores in the California molecular cloud (CMC), so as to better understand the initial conditions of star formation.</P><P><I>Methods.</I> We made a high-resolution column density map (18.2′′) with <I>Herschel</I> data, and extracted a complete sample of the cores in the CMC with the fellwalker algorithm. We performed new single-pointing observations of molecular lines near 90 GHz with the IRAM 30m telescope along the main filament of the CMC. In addition, we also performed a numerical modeling of chemical evolution for the cores under the physical conditions.</P><P><I>Results.</I> We extracted 300 cores, of which 33 are protostellar and 267 are starless cores. About 51% (137 of 267) of the starless cores are prestellar cores. Three cores have the potential to evolve into high-mass stars. The prestellar core mass function (CMF) can be well fit by a log-normal form. The high-mass end of the prestellar CMF shows a power-law form with an index <I>α</I> = −0.9 ± 0.1 that is shallower than that of the Galactic field stellar mass function. Combining the mass transformation efficiency (<I>ε</I>) from the prestellar core to the star of 15 ± 1% and the core formation efficiency (CFE) of 5.5%, we suggest an overall star formation efficiency of about 1% in the CMC. In the single-pointing observations with the IRAM 30m telescope, we find that 6 cores show blue-skewed profile, while 4 cores show red-skewed profile. [HCO<SUP>+</SUP>]/[HNC] and [HCO<SUP>+</SUP>]/[N2H<SUP>+</SUP>] in protostellar cores are higher than those in prestellar cores; this can be used as chemical clocks. The best-fit chemical age of the cores with line observations is ~5 × 10<SUP>4</SUP> yr.</P>
Ke Ding,Ke Shang,Zu-Hua Yu,Chuan Yu,Yan-Yan Jia,Lei He,Cheng-Shui Liao,Jing Li,Chun-Jie Zhang,Yin-Ju Li,Ting-Cai Wu,Xiang-chao Cheng 대한수의학회 2018 Journal of Veterinary Science Vol.19 No.2
Newcastle disease virus (NDV) and Salmonella Pullorum have significant damaging effects on the poultry industry, but no previous vaccinecan protect poultry effectively. In this study, a recombinant-attenuated S. Pullorum strain secreting the NDV hemagglutinin-neuraminidase(HN) protein, C79-13ΔcrpΔasd (pYA-HN), was constructed by using the suicide plasmid pREasd-mediated bacteria homologousrecombination method to form a new bivalent vaccine candidate against Newcastle disease (ND) and S. Pullorum disease (PD). The effectof this vaccine candidate was compared with those of the NDV LaSota and C79-13ΔcrpΔasd (pYA) strains. The serum hemagglutinationinhibition antibody titers, serum immunoglobulin G (IgG) antibodies, secretory IgA, and stimulation index in lymphocyte proliferation wereincreased significantly more (p < 0.01) in chickens inoculated with C79-13ΔcrpΔasd (pYA-HN) than with C79-13ΔcrpΔasd (pYA) but werenot significantly increased compared with the chickens immunized with the LaSota live vaccine (p > 0.05). Moreover, the novel strain provides60% and 80% protective efficacy against the NDV virulent strain F48E9 and the S. Pullorum virulent strain C79-13. In summary, in this study,a recombinant-attenuated S. Pullorum strain secreting NDV HN protein was constructed. The generation of the S. Pullorum C79-13ΔcrpΔasd(pYA-HN) strain provides a foundation for the development of an effective living-vector double vaccine against ND and PD.
Zhang, Chuan-Jin,Wei, Rui-Peng,Tang, Yi,Wang, Ke The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.5
A novel space vector modulation strategy in the non-orthogonal three-dimensional coordinate system for multi-level three-phase four-wire inverters is proposed in this paper. This new non-orthogonal three-dimensional space vector modulation converts original trigonometric functions in the orthogonal three-dimensional space coordinate into simple algebraic operations, which greatly reduces the algorithm complexity of three-dimensional space vector modulation and preserves the independent control of the zero-sequence component. Experimental results have verified the correctness and effectiveness of the proposed three-dimensional space vector modulation in the new non-orthogonal three-dimensional coordinate system.
Zhang, Chuan-Peng,Liu, Tie,Yuan, Jinghua,Sanhueza, Patricio,Traficante, Alessio,Li, Guang-Xing,Li, Di,Tatematsu, Ken’ichi,Wang, Ke,Lee, Chang Won,Samal, Manash R.,Eden, David,Marston, Anthony,Liu, Xia American Astronomical Society 2018 The Astrophysical journal Supplement series Vol.236 No.2
<P>In order to understand the initial conditions and early evolution of star formation in a wide range of Galactic environments, we carried out an investigation of 64 Planck Galactic cold clumps (PGCCs) in the second quadrant of the Milky Way. Using the (CO)-C-13 and (CO)-O-18 J = 1-0 lines and 850 mu m continuum observations, we investigated cloud fragmentation and evolution associated with star formation. We extracted 468 clumps and 117 cores from the (CO)-C-13 line and 850 mu m continuum maps, respectively. We made use of the Bayesian distance calculator and derived the distances of all 64 PGCCs. We found that in general, the mass-size plane follows a relation of m similar to r(1.67). At a given scale, the masses of our objects are around 1/10 of that of typical Galactic massive star-forming regions. Analysis of the clump and core masses, virial parameters, densities, and mass-size relation suggests that the PGCCs in our sample have a low core formation efficiency (similar to 3.0%), and most PGCCs are likely low-mass star-forming candidates. Statistical study indicates that the 850 mu m cores are more turbulent, more optically thick, and denser than the (CO)-C-13 clumps for star formation candidates, suggesting that the 850 mu m cores are likely more appropriate future star formation candidates than the (CO)-C-13 clumps.</P>