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1

A high acid mesoporous USY zeolite prepared by alumination

Ma J., Kang Y., Ma N., Hao W., Wang Y.

Materials Science Poland

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2013

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Vol. 31, No. 1

19-24

EN

A high-acidity HUSY zeolite with mesoporous structure was prepared by alumination with a dilute aqueous NaAlO2 solution and characterized by XRD, N2 adsorption, IR framework vibration and 29Si MAS NMR methods. The results indicated the extra-framework aluminum was reinserted into the tetrahedral framework through isomorphic substitution of framework Si (0Al) sites by Al ions, whereas the crystal and micropore structure were unaltered. FTIR spectra of hydroxyl vibrations and pyridine adsorbed on realuminated zeolites showed that the number of Brfinsted acid sites and strong Lewis acid sites increased whereas weak Lewis acid sites decreased twice. The mesoporous structure composed of inter-and intra-crystalline pores in the aluminated HUSY increased the external surface area of the zeolite, improving accessibility of molecules to the active sites and enhancing its catalytic ability. The realuminated HUSY zeolite supported with Ru catalyst exhibited a higher catalytic activity for benzene hydrogenation than the parent HUSY zeolite; the reaction rate in comparison to the mesozeolite increased by 5.5 times.

2

An Improved Method for Voltage Sag Detection Based on Weighted Least-Squares Estimation with Harmonic Models

Lei H, Lin X., Kang Y., Duan Y., Qiu J.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 10a

238-241

EN

A rapid voltage sag detection method based on weighted least-squares estimation (WLSE) with harmonic models is proposed to satisfy the requirement of the dynamic voltage restorer. The covariance resetting technique is adopted to detect the voltage sag accurately and rapidly, even in condition the voltage contains considerable amount of harmonic components. The threshold of covariance resetting is larger than the steady state error between the sample and estimation of the voltage for the purpose of favorable covariance resetting only if the voltage sag occurs. The threshold of covariance resetting can be small because the steady state error will contain little harmonic components by the proposed WLSE method which have a positive impact on the detecting speed even if the depth of voltage sag is low. The algorithm has been tested under different conditions so as to verify its performance on voltage sag detection.

PL

Zaproponowano metodę szybkiej detekcji zapadu napięcia bazująca na określaniu średniej ważonej najmniejszych kwadratów. Do detekcji zapadu wykorzystuje się technikę kowariancji co umożliwia szybką detekcję nawet przy znacznej zawartości harmonicznych. (Ulepszona metoda detekcji zapadów napięcia bazująca na określaniu wartości ważonej najmniejszych kwadratów z uwzględnieniem harmonicznych)

3

A Dual Loop Control Strategy for Parallel Interleaved Three-Phase Four-Leg PWM Boost-Type Rectifier in UPS

Lei H., Xiao E., Lin X., Kang Y.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 10a

242-246

EN

This paper presents a dual-loop control strategy for parallel interleaved three-phase four-leg PWM boost-type rectifier in double conversion UPS. The interleaving method is adopted for its main benefit of harmonic cancellation. The current in the fourth leg is treated as a perturbation because the fourth leg is shared by rectifier and inverter, and the controller can be designed in a-b-c coordinate conveniently. The DCbus voltage feedback in outer control loop can be delayed by quarter-cycle to filter out the oscillating component when the load of UPS is unbalanced. The performance of proposed control scheme is verified by experimental results.

PL

W artykule zaprezentowano strategię dwóch pętli sterowania trójfazowym czterogałęziowym prostownikiem PWM typu boost w układzie UPS. Wykorzystano metodę z przeplotem w celu eliminacji wpływu harmonicznych. (Dwuobwodowa strategia sterowania trójfazowym prostownikiem PWM w układach UPS)

4

Voltage/current control mode for combined three-phase inverter

Wang H., Yue X., Pei X., Kang Y.

Przegląd Elektrotechniczny

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2010

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R. 86, nr 11a

358-362

EN

For parallel inverters system, controlling the output voltage in normal operation constantly is named the voltage control mode (VCM), and controlling the output current constantly in abnormal operation conditions (such as short circuit) is named the current control mode (CCM). The combined three-phase inverter topology is presented, the equivalent inverter topology with a LCL filter is obtained and mathematical models are built in VCM and CCM. A hybrid control strategy is proposed. The PID control and the repetitive control are used in VCM to obtain the fast dynamic responses and low harmonic distortions. On the other hand, the state feedback control is used in CCM. Pole assignment has been employed in designing parameter of the PID controller and state feedback, and the repetitive control design process is given. Experimental results validate the proposed control using two 400KVA parallel inverters.

PL

Dla równoległego systemu przekształtników zazwyczaj stosuje się system kontroli napięcia VCM i system kontroli prądu CCM (w warunkach specjalnych - np. zwarcia). Zaprezentowano topologie przekształtnika trójfazowego. Odpowiednia topologia przekształtnika z filtrem LCL została przedstawiona. Zaproponowano hybrydową strategię sterowania. System PID sterowania użyty w VCM zapewnia szybką odpowiedź dynamiczną i małe zniekształcenia. W układzie CCM użyto stałego sprzężenia zwrotnego. Sprawdzono położenie biegunów. Wyniki eksperymentu z dwoma 400kVA równoległymi przekształtnikami potwierdziły założenia.