In this paper, a novel variable-speed constant-frequency brushless doubly-fed induction generator (BDFIG) system using back-to-back multilevel converter for high power wind turbine is described. Based on analysis of p...
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In this paper, a novel variable-speed constant-frequency brushless doubly-fed induction generator (BDFIG) system using back-to-back multilevel converter for high power wind turbine is described. Based on analysis of power stator flux oriented vector control theory of BDFIG, an improved maximum power point tracking control strategy is explored. The paper specialty discusses the feasibility and advantage of a novel technique which should soft and fast synchronizing of BDFIG to the grid by using power stator voltage control method and disconnecting from the grid. Simulation results prove the feasibility and validity of the proposed model, theoretical analysis and excellent performance of the proposed control scheme.
The ZrB2/SiC/Zr2Al4C5 multi-phase ceramics were fabricated by spark plasma sintering (SPS) at 1800 °C for 3 min under 20 MPa in an vacuum. Oxidation behavior of multi-phase ceramics were investigated using thermo...
The ZrB2/SiC/Zr2Al4C5 multi-phase ceramics were fabricated by spark plasma sintering (SPS) at 1800 °C for 3 min under 20 MPa in an vacuum. Oxidation behavior of multi-phase ceramics were investigated using thermo gravimetric analysis (TGA) from 20 °C to 1500 °C and muffle furnace in stagnant air at 1200 °C. Samples were analyzed after oxidation by X-ray diffraction (XRD), scanning electron microscopy (SEM) along with energy dispersive spectroscopy (EDS) to determine the reaction products and to observe the microstructure. The results showed that the aluminium borate and mullite crystallize on the surface in the samples oxidized. The effect of Zr2Al4C5 content on the oxidation resistance of the ZrB2 ceramics were discussed respectively, and oxidation mechanism was also analysised.
In this paper, the newly invented brushless dual-mechanical-port electrical machine(BLDMPEM) based on the principle of magnetic field modulation with multi-operational modes and control strategies are presented which ...
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In this paper, the newly invented brushless dual-mechanical-port electrical machine(BLDMPEM) based on the principle of magnetic field modulation with multi-operational modes and control strategies are presented which is suitable for hybrid electrical vehicle application. The prototype structure and principle of operation are described, the mathematic model and equivalent circuit are established, the torque and power reference direction is analyzed,the vector control strategy and power management algorithm of this electrical variable transmission system is discussed. Simulation results prove the feasibility and validity of the proposed prototype, theoretical analysis and excellent performance of the proposed control scheme.
Preceramic polymers to boron nitride (BN) have been synthesized by thermal condensation of different (alkylamino)borazine monomers. Crystalline BN was obtained by pyrolysis of those polymeric precursors in NH3 and the...
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The standard finite element method (FEM) encounters two kinds of errors in the computational acoustic problems: the conventional interpolation error and the dispersion error, the later of which plays an important role...
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The standard finite element method (FEM) encounters two kinds of errors in the computational acoustic problems: the conventional interpolation error and the dispersion error, the later of which plays an important role in the computational acoustics. The dispersion error is rooted at the "overly-stiff" property of the FEM. In order to control the dispersion error, the most effective measure is to make the numerical model reflect the exact model. An edge-based smoothed finite element method (ES-FEM) was adopted for acoustic problems both in frequency domain and time domain. By using only triangular mesh which is very adaptive for any complicated domain and introducing gradient smoothing operation performed over each edge-based smoothed domain, the present method can reduce the stiffness and provide proper "softness" to the model. The results demonstrate that the ES-FEM can provide more accurate solution both in time and frequency domain compared with the linear FEM using the same meshes.
Compared with the conventional short-pitched winding switched reluctance machine, the fully-pitched winding machine produces the effective electromagnetic torque by utilizing the changing mutual inductances among the ...
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ISBN:
(纸本)9781467323277
Compared with the conventional short-pitched winding switched reluctance machine, the fully-pitched winding machine produces the effective electromagnetic torque by utilizing the changing mutual inductances among the phase windings. Previous works show that the fully-pitched winding machine can offer better circuit utilization, higher ratio of torque and current and higher efficiency. This paper compares the static and dynamic performances of these two winding configuration machines at the condition of same outline size, phase voltage and revolving speed. The results show that the advantages of fully-pitched winding machine only appear in the low speed range. According to low speed applications, such as servo drives and torque machine, the torque ripple reduction is necessary. This paper introduces the instantaneous torque closed-loop control to suppress the torque ripple of two machines. By experimental comparison, it is seen that the fully-pitched winding machine is superior to short-pitched winding machine only regarding to low speed applications.
To solve the problem of controlling the stator flux linkage amplitude, a direct torque control (DTC) scheme is proposed for a novel transverse-flux permanent magnet motor (TFPMM) with two-phase conduction mode of brus...
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ISBN:
(纸本)9781467323277
To solve the problem of controlling the stator flux linkage amplitude, a direct torque control (DTC) scheme is proposed for a novel transverse-flux permanent magnet motor (TFPMM) with two-phase conduction mode of brushless DC drive. In this approach, flux linkage hysteresis comparator is removed and the desired voltage space vector is determined by only stator flux position and the output from torque hysteresis comparator, obtaining adaptive stator flux linkage. Further, reasonable phase compensation for the difference of optimal phase advance angle and the angle between stator and rotor flux is adopted to obtain maximum torque per ampere in the constant torque region. The validity and effectiveness of the proposed DTC scheme are verified through simulation results.
The large-scale wind power may influence the stability of the power system when its penetration level exceeds some limit and some disturbance as the short circuit happen. To study and preview this phenomenon before co...
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ISBN:
(纸本)9781457705458
The large-scale wind power may influence the stability of the power system when its penetration level exceeds some limit and some disturbance as the short circuit happen. To study and preview this phenomenon before connect the wind farm into the grid, the use of simulation method has been a good tool. This paper evaluated the stability analysis of the power system in Santiago Island, Cape Verde, considering a 9.25 MW wind farm installed and connected into the 40 MW grid. The simulation results by MATlab/Simulink? show the stable performance of power system under short circuit fault. The effect of STATCOM is also evaluated.
Data collected from mobile phones have potential knowledge to provide with important behavior patterns of individuals. In this paper, we present approaches to discovering personal mobility and characteristics based on...
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