Effective online power system transient stability analysis and critical cutset detection method has important significance for the safe and stable operation of interconnected power system. Aiming at the disadvantages ...
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Effective online power system transient stability analysis and critical cutset detection method has important significance for the safe and stable operation of interconnected power system. Aiming at the disadvantages of the PEBS(potential energy boundary) method based on branch potential energy, a high reliable method named Branch RIDGE method is proposed in this paper for power system transient stability analysis and critical cutset detection. Also, a simple stability index of branch and system and a method to detect the stability status and critical cutsets of power system based on BPR and branch stability index are proposed. This method is established on the dynamic response trajectories of power system network information. In the case of known parameters of network structure, the method only needs real-time data of bus voltage magnitude and phase angle to do online power transient stability analysis and critical cutset detection. Because the method doesn't make assumption of two group instability mode, this method can be used in multi-swing instability and multi-group instability mode. The simulation on New England 10 machines show the validation of the proposed method.
The plasma parameters of planar-type surface-wave plasmas （SWPs） are diagnosed based on the resonant excitation of surface plasmon polaritons （SPPs）. The plasma parameter distributions are obtained by changing the...
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The plasma parameters of planar-type surface-wave plasmas （SWPs） are diagnosed based on the resonant excitation of surface plasmon polaritons （SPPs）. The plasma parameter distributions are obtained by changing the discharge conditions of gas pressure and incident power. The measured experimental results show that the plasma near the heating layer is excited by surface waves of SPPs while the plasma located downstream originates from diffusion Moreover, the influence of high-frequency oscillations plays a significant role in producing the proposed SWPs with bi-Maxwellian electron energy distributions.
As the basic of a deeper investigation on the turbulent transport, the fluctuation property in the boundary of the newly-reconstructed Joint Texas Experimental Tokamak （J- TEXT） is studied experimentally using the r...
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As the basic of a deeper investigation on the turbulent transport, the fluctuation property in the boundary of the newly-reconstructed Joint Texas Experimental Tokamak （J- TEXT） is studied experimentally using the reciprocating Langmuir four-tip probe, which has been built and operated as the primary diagnostic tool in the boundary of J-TEXT tokamak. In this paper, spatial profiles of the plasma-edge parameters are obtained, such as electron temperature, plasma density, plasma potential, poloidal electric field and their fluctuations. The results indicate the existence of a Er ×BT shear layer at the vicinity of last closed flux surface （LCFS）, with the fluctuations suppressed in varying degrees. The turbulence-induced particle and energy fluxes can be calculated by the local plasma parameters above. Convection dominates the cross-field turbulent transport in boundary plasma. Electrostatic fluctuations properties are also studied in detail with the help of numerical analysis. Statistical analysis on density fluctuation shows that, the intermittency can affect the turbulence in the scrape-off layer （SOL）.
In application of Superconducting magnetic energy storage device (SMES), current lead represents a key development component. This paper will focus on parameters and structure design of hybrid high-temperature superco...
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In application of Superconducting magnetic energy storage device (SMES), current lead represents a key development component. This paper will focus on parameters and structure design of hybrid high-temperature superconductor (HTS) current lead in a SMES with 100 kJ/100 kW class. Based on the theoretical analysis, finite element simulation (FEA) has been used. It studies the thermal influence of variable cross-sectional area, HTS material and the connection between current lead and cryocooler. Some improvements have been proposed to reduce heat losses. At the end of this paper, a whole procedure about hybrid current lead design is given.
A stator earth fault protection scheme based on fault current is presented in this paper. It trips out the faulted generator only if the fault current following the breakdown channel exceeds the tolerance capacity of ...
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ISBN:
(纸本)9781479932559
A stator earth fault protection scheme based on fault current is presented in this paper. It trips out the faulted generator only if the fault current following the breakdown channel exceeds the tolerance capacity of the generator. Otherwise, it will just emit alarm signals. This protection scheme can avoid unnecessary trip-out of large generator, which influences the safe operation of power system, while ensuring the generator security. To achieve the scheme, methods of calculating fault current in real time are provided for three common generator neutral earthing methods basing on the zero-sequence equivalent circuits. An implementation scheme is given on the basis of the sub-harmonic injection protection device. The protection algorithm flow and protection criterion are discussed as well. Simulation results show the accuracy of the fault current calculation method and the validity of the protection scheme.
In this paper, first, the fundamental principle of operation of Brushless Doubly-Fed Machine(BDFM) has been introduced, and then the steady-state equivalent circuit of BDFM was utilised to propose the basic idea of de...
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In this paper, first, the fundamental principle of operation of Brushless Doubly-Fed Machine(BDFM) has been introduced, and then the steady-state equivalent circuit of BDFM was utilised to propose the basic idea of design and give the arithmetic flow chart of BDFM as generator. As calculation of parameters for a variety of different machines is required, the approach of calculating leakage inductance due to slot and harmonic presented here for wound rotor is motivated by versatility. At last, the paper takes a 4/8 poles BDFM as generator for instance and utilizes Vc++6.0 to compile an electromagnetic calculation program to calculate correlative performance data. The paper also analyzes and compares the data with the measurement in experiment.
A double-layer grating structure is proposed, which can show nonreciprocal transmission in near-IR frequency range. The structure is composed of metallic grating with magneto-optical substrate. The nonreciprocity depe...
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Traditionally, based on the pseudo rigid body model method, the ideal stiffness of double parallel four-bar mechanism is obtained by virtual work principle while support arm bar is regard as a rigid rod. However, a te...
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ISBN:
(纸本)9781479910267
Traditionally, based on the pseudo rigid body model method, the ideal stiffness of double parallel four-bar mechanism is obtained by virtual work principle while support arm bar is regard as a rigid rod. However, a terrible error between ideal and real stiffness will be caused in practice as a result of the bending deformation of support arm bar. Therefore, it is urgent to analyze the error of stiffness in double parallel four-bar mechanism and to explore the condition in which the support arm bar could be equivalent to rigid rod. In the paper, an accurate expression of stiffness in the double parallel four-bar mechanism is derived by integral method while the support arm bar is studied as a variable cross section beam through force analysis and deformation analysis. The error between stiffness derived from virtual work principle and integral method is obtained, and whose changing trend with the structural parameters of the right-angle flexure hinge and the support arm bar is analyzed. The result demonstrates that the error is less than 1% when the thickness ratio is larger than 6 and the length ratio is between 6 and 25, that is, the support arm bar can be equivalent to rigid rod, and whose bend deformation can be neglected.
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