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EN
The Static Synchronous Compensator (STATCOM a.k.a. SVG) is widely used to regulate dynamic reactive power and to solve dynamic voltage stability problems. Modeling shows that a cascaded STATCOM, which is composed of several cascaded H-bridges, not only has strong coupling characteristics when an LCL filter is added but it is also a non-linear, multivariable system. Therefore, its practical design and application are dicult to implement. In this paper an internal decoupling control algorithm is introduced to provide independent control of the active and reactive currents. Decoupling control algorithms are proposed, and models and simulation of the decoupling are provided. We describe the setting up of a simulation and experiments with a cascaded STATCOM based on combined circuit topology with a multi-field programmable gate array (FPGA), and double-loop control algorithms with a current inner loop, and a capacitor voltage outer loop. To provide control of the current inner loop, proportional-integral (PI) and resonant controllers are used, having the control ability to cancel harmonics while compensating for the reactive power. This paper presents new current-tracing control models that compensate for the fundamental current and eliminate selective harmonics by adopting a d-q synchronous reference frame, and a discrete Fourier transform (DFT). Voltage balance is realized by introducing modulation wave distribution strategies. Furthermore, both simulation and experiments are employed to verify the feasibility and eectiveness of the control strategy.
2
Content available remote A Nonnegative Subspace Approach for Packet Loss Concealment
EN
This paper presents a nonnegative subspace approach for packet loss concealment problem. The magnitude spectrogram of speech signal is projected onto nonnegative subspace using nonnegative matrix factorization algorithm. Consequently, packet loss concealment problem is transformed to linear interpolation of the projective coefficients in nonnegative subspace. Simulation examples, objective tests show that packet loss concealment in the nonnegative subspace results in improved perceptual quality of speech compared to popular packet loss concealment algorithms.
PL
Zaprezentowano metodę subprzestrzeni dla rozwiązania problemu straty pakietu. Spektrogram amplitudowy sygnału mowy .jest poddawany projekcji do nieujemnej podprzestrzeni przy wykorzystaniu macierzy faktoryzacji. W rezultacie problem staje się możliwy do liniowej interpolacji. Osiągnięto dostrzegalną poprawę jakości przetwarzania sygnału mowy.
EN
This paper is concerned with the problem of stochastic stability and generalized H2 control for discrete-time fuzzy largescale stochastic systems with time-varying and infinite-distributed delays. Large-scale interconnected systems consist of a number of discrete-time interconnected Takagi-Sugeno (T-S) subsystems. First, a novel Delay-Dependent Piecewise Lyapunov-Krasovskii Functional (DDPLKF0 is proposed, in which both the upper and the lower bound of delays are considered. Then, two improved delay-dependent stability conditions are established based on this DDPLKF in terms of Linear Matrix Inequalities (LMIs). The merit of the proposed conditions lies in its reduced conservatism, which is achieved by circumventing the utilization of some bounding inequalities for cross products of two vectors and by considering the interactions among the fuzzy subsystems in each subregion. A decentralized generalized H2 state feedback fuzzy controller is designed for each subsystem. It is shown that the mean-square stability for discrete T-S fuzzy large-scale stochastic systems can be established if a DDPLKF can be constructed and a decentralized controller can be obtained by solving a set of LMIs. Finally, an illustrative example is provided to demonstrate the effectiveness of the proposed method.
4
Content available remote Scale Effect on Jute/Cotton Fibres and their Blended Yarns
EN
The tenacities of jute and cotton fibres as well as their blended yarns at different gauge lengths were investigated in this paper. Based on Weibull distribution, the tenacity of the fibres and their blended yarns at a testing gauge length from 5 mm to 500 mm was studied. The tenacity of jute and cotton fibres is more dependent on the gauge length than that of their blended yarns. The blended yarn tenacity with a high jute content is more sensitive to the gauge length than that of a yarn with a low jute content.
PL
Badano wytrzymałość włókien bawełnianych i jutowych oraz przędz wykonanych z mieszanek tych włókien przy różnych długościach zrywanych próbek zmieniając je od 5 mm do0 500mm. Wytrzymałość włókien i przędz analizowano na podstawie rozkładu Weibulla. Stwierdzono, że wytrzymałość włókien jest bardziej zależna od długości zrywanej próbki niż przędz mieszankowych, jak również , że zwiększenie zawartości juty w przędzy bardziej uzależnia wytrzymałość od długości próbki.
5
Content available remote Two projection-type algorithms for pseudo-monotone variational inequalities
EN
Two projection-type algorithms, different from the ones presented by Solodov & Tseng (1996) and He (1997) in the computation of stepsize, for solving pseudo-monotone variational inequality problems are presented. It is shown that the algorithms are globally convergent and, in addition, they are convergent R-linearly or Q-linearly under some mild conditions.
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