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Wyświetlanie 1-7 z 7
Tytuł:
Analysis of disturbing effect of 3 kV DC supplied traction vehicles equipped with two-level and three-level VSI on railway signalling track circuits
Autorzy:
Steczek, M.
Szeląg, A.
Chatterjee, D.
Powiązania:
https://bibliotekanauki.pl/articles/201149.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
voltage source inverters
traction vehicle
compatibility
harmonics
harmonics elimination
źródła napięcia
pojazd trakcyjny
zgodność
harmonia
Opis:
Electric traction vehicles cooperating with a 3kV DC traction system and equipped with drive systems based on voltage source inverters are the most significant sources of disturbances for a railway signalling system. Every traction vehicle to be authorised for operation on railway lines must fulfil the limits imposed on current harmonics magnitudes and those provided by railway operators. The solution introduced for prototypes of most modern traction drives is to replace the two-level inverters with three-level topology. Therefore, it is essential to establish the influence of the new solution on the railway signalling system. This paper presents a comparative analysis between simulation results delivered for two and three-level traction drive system regarding generation of disturbing current harmonics. Two types of VSI modulation techniques were taken under consideration: sinusoidal PWM (SPWM) and a new one, proposed by the authors, based on selective harmonic elimination (SHE). Furthermore, the authors presented application of one of the SHE based optimization techniques for shaping the EMU’s (electric multiple unit) DC side input current harmonics spectrum in order to meet the required limits. The described technique is based on off-line generation of a set of solutions for each of the VSI operating points and selection of the best solution for the assumed criteria. The applied simulation models and the concept of SHE control were verified in a laboratory by means of a low-power drive stand. Using the three-level inverter in traction drives system results in less current harmonics than using two-level topology without modification of the modulation technique. Thus, it does not guarantee fulfilling all limits assumed in this paper. The proposed modulation technique allows for fulfilling the limits, and the technical implementation of the proposed technique in a traction drive system will be considered in future studies.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2017, 65, 5; 663-674
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Usage of connor inlets to eliminate shrinkage
Autorzy:
Fecko, D.
Vasková, I.
Eperješi, L'.
Závodný, M.
Powiązania:
https://bibliotekanauki.pl/articles/380256.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
żeliwo szare
eliminacja skurczu
oprogramowanie symulacyjne
grey cast iron
connor inlet
shrinkage elimination
simulation software
Opis:
The demand for castings of high quality and sound work is nowadays very high. The production of sound castings without foundry errors is the big issue in modern foundries. Foundry simulation software can do a lot to help improve the disposition of castings, gating system and feeder system, and assure good filling and solidification conditions, and also produce sound casting without the need of the old method of 'try and error'. One can easily change a lot of parameters for filling and solidification, and create the best proposal for production. Connor inlets have two functions. One is that it serves as an ingate, through which molten metal passes and comes into the mould cavity. The second function is that it serves as a feeder and substitutes the metal contracted during solidification and cooling of the castings. It can also save quite a lot of metal in comparison to classic feeders.
Źródło:
Archives of Foundry Engineering; 2012, 12, 3; 25-28
1897-3310
2299-2944
Pojawia się w:
Archives of Foundry Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Elimination of viruses from the hop and propagation of virus-free plant material in the West Poland
Autorzy:
Cajza, M
Zielinska, L.
Lubik, M.
Powiązania:
https://bibliotekanauki.pl/articles/65709.pdf
Data publikacji:
1997
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
Humulus lupulus
heat therapy
virus
Polska
virus-free plant
meristem
hop
propagation
elimination
plant material
Opis:
The hop (Humulus lupulus L.) is one of the most infected plants by viruses. Preparation of apical meristems in combination with heat therapy was successfuly used for obtaining of virus-free hop plants in various countries in the world. In our experiments we prepared the meristems both before and after the heat therapy. Hop plants regenerated from such meristems were free not only from the thermolabile ILAR-viruses, but in the great number also from the thermostable CARLA - viruses. The method of virus elimination and micropropagation of virus-free plants in vitro, described in this paper, enables to obtain a large number of virus-free plantlets in a short time.
Chmiel (Humulus lupulus L.) należy do roślin uprawnych w największym stopniu porażonych przez wirusy. Wirusy występujące w chmielu mogą powodować znaczne obniżenie masy plonu ( 4-38%) i zawartości alfa-kwasów w szyszkach (18-30%). Stosowane do tej pory metody uwalniania chmielu od wirusów, polegające na regeneracji roślin z merystemów wierzchołkowych albo na regeneracji roślin z merystemów w połączeniu z terapią wysokotemperaturową, pozwalały na skuteczne wyeliminowanie z chmielu wirusów termolabilnych zwłaszcza z grupy ILAR, natomiast wirusy termostabilne z grupy CARLA najczęściej pozostawały w zainfekowanych roślinach. Zmodyfikowana metoda uwalniania chmielu od wirusów różni się od dawniej stosowanych tym, że możliwie najmniejsze merystemy (0,2-0,3 mm) wypreparowywano zarówno przed terapią termiczną, jak również po terapii wysokotemperaturowej. Cięcie oddzielające merystem od reszty regenerującej rośliny przeprowadzano w strefie elongacyjnej (powstającej w trakcie wzrostu w wysokiej temperaturze), która hamuje replikację wirusów i najczęściej jest od tych patogenów wolna. Zastosowana metoda charakteryzowała się dużą śmiertelnością merystemów podczas terapii termicznej (około 70%) i regeneracji roślin, ale była skuteczna w eliminowaniu również termostabilnych wirusów z grupy CARLA w około 80-90%. Opracowane zostały także pożywki do hodowli chmielu in vitro dla różnych etapów hodowli tej rośliny. Skład pożywek został maksymalnie uproszczony (całkowicie usunięto składniki termolabilne z pożywek do masowego klonowania roślin) w celu przyspieszenia i ułatwienia prac związanych z ich przygotowaniem. W wyniku przeprowadzonych prac uwolniono od wirusów następujące odmiany chmielu: Lubelska, Lomik, Izabella, Marynka i Northern Brewer. W roku 1995 na terenie Wielkopolski założone zostały pierwsze plantacje produkcyjne z wyprodukowanych sadzonek chmielu, wolnych od wirusów.
Źródło:
Journal of Plant Protection Research; 1997, 37, 1-2
1427-4345
Pojawia się w:
Journal of Plant Protection Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A note on the Miller-Tucker-Zemlin model for the asymmetric traveling salesman problem
Autorzy:
Sawik, T.
Powiązania:
https://bibliotekanauki.pl/articles/202082.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
asymmetric traveling salesman problem
Miller-Tucker-Zemlin constraints
subtour elimination constraints
problem komiwojażera
SEC
metoda MTZ
Opis:
An enhancement of the Miller-Tucker-Zemlin (MTZ) model for the asymmetric traveling salesman problem is presented by introducing additional constraints to the initial formulation. The constraints account for ordering of boundary nodes as well as all successive nodes in the salesman tour. The enhanced MTZ subtour elimination constraints are computationally compared with the basic MTZ constraints and the version of MTZ lifted by Desrochers and Laporte. The proposed enhancement shows improved performance on a number of asymmetric TSPLIB instances.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2016, 64, 3; 517-520
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
WTHD minimisation in hybrid multilevel inverter using biogeographical based optimisation
Autorzy:
Kavitha, R.
Thottungal, R.
Powiązania:
https://bibliotekanauki.pl/articles/141212.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
biogeographical based optimisation
BBO
genetic algorithm
GA
bacterial foraging algorithm
BFA
weighted total harmonics distortion
WTHD
optimal minimisation of total harmonic
OMTHD
selective harmonic elimination
SHE
Opis:
Harmonic minimisation in hybrid cascaded multilevel inverter involves complex nonlinear transcendental equation with multiple solutions. Hybrid cascaded multilevel can be implemented using reduced switch count when compared to traditional cascaded multilevel inverter topology. In this paper Biogeographical Based Optimisation (BBO) technique is applied to Hybrid multilevel inverter to determine the optimum switching angles with weighted total harmonic distortion (WTHD) as the objective function. Optimisation based on WTHD combines the advantage of both OMTHD (Optimal Minimisation of Total Harmonic Distortion) and SHE (Selective Harmonic Elimination) PWM. WTHD optimisation has the benefit of eliminating the specific lower order harmonics as in SHEPWM and minimisation of THD as in OMTHD. The simulation and experimental results for a 7 level multilevel inverter were presented. The results indicate that WTHD optimization provides both elimination of lower order harmonics and minimisation of Total Harmonic Distortion when compared to conventional OMTHD and SHE PWM. Experimental prototype of a seven level hybrid cascaded multilevel inverter is implemented to verify the simulation results.
Źródło:
Archives of Electrical Engineering; 2014, 63, 2; 187-196
1427-4221
2300-2506
Pojawia się w:
Archives of Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Low Complexity Multiplier-less Modified FRM Filter Bank using MPGBP Algorithm
Autorzy:
Parvathi, A. K.
Sakthivel, V.
Powiązania:
https://bibliotekanauki.pl/articles/2200702.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
Frequency response masking (FRM)
Modified FRM filter bank (ModFRM-FB)
Multiplier-less filter
Matching pursuits with generalized bit planes (MPGBP)
Sum-of-power-of two (SOPOT)
Common sub-expression elimination (CSE)
Opis:
The design of a low complexity multiplier-less narrow transition band filter bank for the channelizer of multistandard software-defined radio (SDR) is investigated in this paper. To accomplish this, the modal filter and complementary filter in the upper and lower branches of the conventional Frequency Response Masking (FRM) architecture are replaced with two power-complementary and linear phase filter banks. Secondly, a new masking strategy is proposed to fully exploit the potential of the numerous spectra replicas produced by the interpolation of the modal filter, which was previously ignored in the existing FRM design. In this scheme, the two masking filters are appropriately modulated and alternately masked over the spectra replicas from 0 to 2π, to generate even and odd channels. This Alternate Masking Scheme (AMS) increases the potency of the Modified FRM (ModFRM) architecture for the design of computationally efficient narrow transition band uniform filter bank (termed as ModFRM-FB). Finally, by combining the adjoining ModFRM-FB channels, Non-Uniform ModFRMFB (NUModFRM-FB) for extracting different communication standards in the SDR channelizer is created. To reduce the total power consumption of the architecture, the coefficients of the proposed system are made multiplier-less using Matching Pursuits Generalized Bit-Planes (MPGBP) algorithm. In this method, filter coefficients are successively approximated using a dictionary of vectors to give a sum-of-power-of-two (SOPOT) representation. In comparison to all other general optimization techniques, such as genetic algorithms, the suggested design method stands out for its ease of implementation, requiring no sophisticated optimization or exhaustive search schemes. Another notable feature of the suggested approach is that, in comparison to existing methods, the design time for approximation has been greatly reduced. To further bring down the complexity, adders are reused in recurrent SOPOT terms using the Common Subexpression Elimination (CSE) technique without compromising the filter performance.
Źródło:
International Journal of Electronics and Telecommunications; 2022, 68, 4; 831--840
2300-1933
Pojawia się w:
International Journal of Electronics and Telecommunications
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An approach to suppress high-frequency resonance using model predictive and selective harmonic elimination combined strategy
Autorzy:
Chen, Sitong
Chen, Xiaoqiang
Wang, Ying
Xiong, Ye
Powiązania:
https://bibliotekanauki.pl/articles/1841300.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
CRH5 EMUs and traction power supply coupled system
high-frequency oscillation
high speed railway
model predictive control (MPC)
selective harmonic elimination pulse-width modulation (SHEPWM)
CRH5 EMU i system sprzężony z zasilaniem trakcyjnym
oscylacja wysokiej częstotliwości
kolej dużych prędkości
kontrola predykcyjna modelu (MPC)
selektywna eliminacja harmoniczna modulacja szerokości impulsu (SHEPWM)
Opis:
High-frequency resonance is a prominent phenomenon which affects the normal operation of the high-speed railway in China. Aiming at this problem, the resonance mechanism is analyzed first. Then, model predictive control and selective harmonic elimination pulse-width modulation (MPC-SHEPWM) combined control strategy is proposed, where the harmonics which cause the resonance can be eliminated at the harmonic source. Besides, the MPC is combined to make the current track the reference in transients. The proposed control has the ability to suppress the resonance while has a faster dynamic performance comparing with SHEPWM. Finally, the proposed MPC-SHEPWM is tested in a simulation model of CRH5 (Chinese Railway High-speed), EMUs (electric multiple units) and a traction power supply coupled system, which shows that the proposed MPC-SHEPWM approach can achieve the resonance suppression and shows a better dynamic performance.
Źródło:
Archives of Electrical Engineering; 2021, 70, 2; 415-430
1427-4221
2300-2506
Pojawia się w:
Archives of Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-7 z 7

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