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  • Author: Yong Chang x
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HVDC and FACTS devices have been widely applied in power system for their excellent and flexible control ability. Their contributions to the damping of system oscillations are of great importance for achieving satisfactory system performance. However, previous experience has shown that there may be negative interactions among FACTS devices whose supplementary controllers are designed separately. This may deteriorate system performance and even make system unstable. The interactions of HVDC and SVC during system oscillation were analyzed in this paper. The coordinate supplementary damping controller for HVDC and SVC were then designed based on projective control principle. The criterion of synthetic residue is adopted in choosing the proper input wide area signals. Eigenvalue analysis and time domain simulations were performed on a two-area system and the results demonstrated the effectiveness of the proposed controller.

Abstract

In this paper, sufficient conditions are established for the controllability of Sobolev type semilinear functional differential and integrodifferential inclusions with an unbounded delay in Banach spaces. The main results are obtained by using the fixed point theorem for condensing maps due to Martelli.

Abstract

Various lignin model compounds were oxidized with polyoxometalate (POM), K5[SiVW11O40]·12 H2O, in sodium acetate buffer (I=0.2 M, pH 5.0) and the reaction kinetics were investigated. The reactions were found to have second order reaction rates, first order with regards to both lignin model compound and POM. A dramatic increase in reactivity was observed upon addition of methoxyl groups in ortho-positions to the phenolic hydroxyl group. Syringyl units reacted faster than guaiacyl units. Reaction rates of para-substituted guaiacyl and syringyl model compounds showed a strong dependency on the nature of the substituents. The reaction rate of a 5-5′ dimer lignin model compound was extremely fast. The addition of the ortho-phenol substituent not only increased the electron density of the aromatic ring, but also helped stabilize the intermediate phenoxy radical through resonance stabilization and delocalization.

Abstract

C24H29N5O, triclinic, P1̄ (no. 2), a = 10.352(9) Å, b = 10.911(10) Å, c = 12.480(6) Å, α = 97.33(2)°, β = 110.29(2)°, γ = 115.353(15)°, V = 1129.6(15) Å3, Z = 2, R gt(F) = 0.0614, wR ref(F 2) = 0.1855, T = 296(2) K.

The evolution of impedance measurement methods into the current state of the art is reviewed briefly, and recent efforts to develop new instruments to make electrochemical impedance spectroscopy (EIS) measurements faster and more accurate are described. The most recent approach for impedance measurement uses a multichannel detection technique, which is analogous to a spectroscopic measurement such as in Fourier transform infrared spectroscopy. This method, which is capable of making impedance measurements in real time during an electrochemical experiment, allows us to come up with a new integrated equation that makes a full description of an electrochemical system possible.