Documents disponibles écrits par cet auteur

Operation of grid-connected DFIG under unbalanced grid voltage condition / Yi Zhou in IEEE transactions on energy conversion, Vol. 24 N°1 (Mars 2009) 

Public ISBD [article]  in IEEE transactions on energy conversion > Vol. 24 N°1 (Mars 2009) . - pp. 240 - 246 Titre : Operation of grid-connected DFIG under unbalanced grid voltage condition Type de document : texte imprimé Auteurs : Yi Zhou, Auteur ; Bauer, P., Auteur ; Ferreira, J. A., Auteur Année de publication : 2009 Article en page(s) : pp. 240 - 246 Note générale : energy conversion Langues : Anglais (eng) Mots-clés : Asynchronous  generators;  machine  control;  machine  protection;  machine  theory;  wind  power Résumé : Doubly fed induction generator (DFIG) still shares a large part in today's wind power market. It provides the benefits of variable speed operation cost-effectively, and can control its active and reactive power independently. Crowbar protection is often adopted to protect the rotor-side voltage source converter (VSC) from transient overcurrent during grid voltage dip. But under unbalanced grid voltage condition, the severe problems are not the transient overcurrent, but the electric torque pulsation and dc voltage ripple in the back-to-back VSCs. This paper develops dynamic models in MATLAB/Simulink, validates it through experiments, investigates the behavior of DFIG during unbalanced grid voltage condition, and proposes new controllers in separated positive and negative sequence. Methods to separate positive and negative sequence components in real time are also developed, and their responses to unsymmetrical voltage dip are compared. Simulation results prove that the separated positive and negative sequence controllers limit the torque pulsation and dc voltage ripple effectively. En ligne : http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=4770180&sortType%3Das [...] [article] Operation of grid-connected DFIG under unbalanced grid voltage condition [texte imprimé] / Yi Zhou, Auteur ; Bauer, P., Auteur ; Ferreira, J. A., Auteur . - 2009 . - pp. 240 - 246. energy conversion Langues : Anglais (eng) in IEEE transactions on energy conversion > Vol. 24 N°1 (Mars 2009) . - pp. 240 - 246 Mots-clés : Asynchronous  generators;  machine  control;  machine  protection;  machine  theory;  wind  power Résumé : Doubly fed induction generator (DFIG) still shares a large part in today's wind power market. It provides the benefits of variable speed operation cost-effectively, and can control its active and reactive power independently. Crowbar protection is often adopted to protect the rotor-side voltage source converter (VSC) from transient overcurrent during grid voltage dip. But under unbalanced grid voltage condition, the severe problems are not the transient overcurrent, but the electric torque pulsation and dc voltage ripple in the back-to-back VSCs. This paper develops dynamic models in MATLAB/Simulink, validates it through experiments, investigates the behavior of DFIG during unbalanced grid voltage condition, and proposes new controllers in separated positive and negative sequence. Methods to separate positive and negative sequence components in real time are also developed, and their responses to unsymmetrical voltage dip are compared. Simulation results prove that the separated positive and negative sequence controllers limit the torque pulsation and dc voltage ripple effectively. En ligne : http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=4770180&sortType%3Das [...]

Tribological characteristics of three novel imidazoline-type thiadiazole derivatives in colza oil and synthetic diester / Lin Shui in Transactions of the ASME . Journal of tribology, Vol. 134 N° 3 (Juillet 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 134 N° 3 (Juillet 2012) . - 08 p. Titre : Tribological characteristics of three novel imidazoline-type thiadiazole derivatives in colza oil and synthetic diester Type de document : texte imprimé Auteurs : Lin Shui, Auteur ; Yi Zhou, Auteur ; Guoru Zhang, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : tribology Langues : Anglais (eng) Mots-clés : lubricant  additives;  colza  oil;  synthetic  diester;  additive-deposited  films;  XANES Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Owing to the requests of exploring environment-friendly and multifunctional lubricant additives, three novel imidazoline-type thiadiazole derivatives are prepared and used as lubricant additives in two biodegradable base stocks, colza oil and synthetic diester, respectively, and their tribological performance is tested using the four-ball tester. For further understanding of their tribological behaviors, x-ray absorption near edge structure (XANES) spectroscopy is adopted to analyze the thermal films and tribofilms generated from these additives in two base stocks. Tribological tests show that all these thiadiazole derivatives are effective in reducing wear in synthetic diester, and derivative SIB (stearic acid-imidazoline-type thiadiazole derivative) is better than derivative OIB (oleic acid-imidazoline-type thiadiazole derivative) and derivative DIB (lauric acid-imidazoline-type thiadiazole derivative) in reducing friction at high additive concentrations. But these derivatives almost fail in improving the tribological characteristic of colza oil. According to XANES spectra, thermal films formed in two base stocks are mainly composed of ferrous sulfate and adsorbed organic sulfide. These derivatives are also easily oxidized into high-valent sulfate in colza oil during the rubbing process, and ferrous sulfate is the main component of these tribofilms. But in synthetic diester, tribofilms are mainly composed of ferrous sulfide, and it is notable that the tribofilm generated by derivative SIB at 1.0 wt. % is composed of ferrous sulfide and ferrous disulfide. Under extreme-pressure conditions, these derivatives easily react with the metallic surface to generate ferrous sulfide in colza oil. But in synthetic diester, adsorbed organic sulfide is the main component of those films. The base stock has a great impact on the compositions of these reaction films, so the tribological behaviors of these derivatives are different in two base stocks. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE9000134000003 [...] [article] Tribological characteristics of three novel imidazoline-type thiadiazole derivatives in colza oil and synthetic diester [texte imprimé] / Lin Shui, Auteur ; Yi Zhou, Auteur ; Guoru Zhang, Auteur . - 2012 . - 08 p. tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 134 N° 3 (Juillet 2012) . - 08 p. Mots-clés : lubricant  additives;  colza  oil;  synthetic  diester;  additive-deposited  films;  XANES Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Owing to the requests of exploring environment-friendly and multifunctional lubricant additives, three novel imidazoline-type thiadiazole derivatives are prepared and used as lubricant additives in two biodegradable base stocks, colza oil and synthetic diester, respectively, and their tribological performance is tested using the four-ball tester. For further understanding of their tribological behaviors, x-ray absorption near edge structure (XANES) spectroscopy is adopted to analyze the thermal films and tribofilms generated from these additives in two base stocks. Tribological tests show that all these thiadiazole derivatives are effective in reducing wear in synthetic diester, and derivative SIB (stearic acid-imidazoline-type thiadiazole derivative) is better than derivative OIB (oleic acid-imidazoline-type thiadiazole derivative) and derivative DIB (lauric acid-imidazoline-type thiadiazole derivative) in reducing friction at high additive concentrations. But these derivatives almost fail in improving the tribological characteristic of colza oil. According to XANES spectra, thermal films formed in two base stocks are mainly composed of ferrous sulfate and adsorbed organic sulfide. These derivatives are also easily oxidized into high-valent sulfate in colza oil during the rubbing process, and ferrous sulfate is the main component of these tribofilms. But in synthetic diester, tribofilms are mainly composed of ferrous sulfide, and it is notable that the tribofilm generated by derivative SIB at 1.0 wt. % is composed of ferrous sulfide and ferrous disulfide. Under extreme-pressure conditions, these derivatives easily react with the metallic surface to generate ferrous sulfide in colza oil. But in synthetic diester, adsorbed organic sulfide is the main component of those films. The base stock has a great impact on the compositions of these reaction films, so the tribological behaviors of these derivatives are different in two base stocks. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE9000134000003 [...]