Baoding, China
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Huang L.,Nanjing Southeast University | Yu H.,Nanjing Southeast University | Hu M.,Nanjing Southeast University | Zhao J.,Nanjing Southeast University | Cheng Z.,Baoding Tianwei Group Co.
IEEE Transactions on Magnetics | Year: 2011

In this paper, a novel flux-switching permanent-magnet linear generator (FSPMLG) is proposed for wave-energy extraction. The 2-D finite-element method (FEM), combined with the equivalent circuit, is implemented to investigate the electromagnetic characteristics of the FSPMLG. The optimal structure of the linear generator has advantages of better voltage waveform and minimal cogging effect. The numerical analysis is validated by experiments. The results indicate that these kinds of linear generators are suitable for the application of wave energy conversion. © 2011 IEEE.


Li H.,North China Electrical Power University | Cui X.,North China Electrical Power University | Liu D.,Baoding Tianwei Group Co. | Lu T.,North China Electrical Power University | Cheng Z.,Baoding Tianwei Group Co.
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2010

In order to look into the influence on the operation performance of a power transformer caused by the direct current (DC) bias, an improved electric and magnetic circuit coupled model is used. The eddy current effects of the core material are taken into consideration. The characteristics of exciting currents, leakage magnetic flux, secondary-side induced voltage, and the level of DC flux in limb are investigated for transformers with different core types and coil connections. The definition of transformer DC bias ratio is presented in the paper, with the aim of assessing the DC bias endurance in an unifed condition. The results indicate that the increasement of the DC bias ratio lead to distortion of the exciting currents waveform, increased harmonic currents and leakage magnetic flux from the coil. Meanwhile, the secondary-side induced voltage remains the same as in normal condition. In all transformer products, the three-phase three-limb transformer has the lowest level of sensitivity to the DC bias, but the single-phase three-limb tranformer bank with YN, yn connected coils has the highest level. The existence of the delta-connected coil has a positive meaning on improving the transformer endurance to the DC bias.


Zhao X.-J.,North China Electrical Power University | Li L.,North China Electrical Power University | Cheng Z.-G.,Baoding Tianwei Group Co. | Lu J.-W.,Griffith University | Jiao C.-P.,Baoding Tianwei Group Co.
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2010

In this paper the harmonic-balanced finite element method (HBFEM) was applied to study the DC bias phenomenon in power transformers. Variables in electric circuits and magnetic field were represented in harmonic forms duo to the periodic characteristic of electromagnetic field under steady-state excitation. The harmonic-balanced finite element equation was set up by means of the harmonic decomposition of magnetic reluctivity, considering the coupling of electric circuit and magnetic field. The harmonic solutions of exciting current and magnetic vector potentials were calculated directly to analyze the relationship between DC bias and DC flux. The local vortex characteristic of flux distribution in each harmonic was also presented. An Epstein frame-like core model was applied to carry out the DC bias experiment. A good agreement between calculated results and experimental data proves the effectiveness of HBFEM in the investigation of DC bias phenomenon. © 2010 Chin. Soc. for Elec. Eng.


Zheng W.,CAS Academy of Mathematics and Systems Science | Cheng Z.,Baoding Tianwei Group Co.
IEEE Transactions on Magnetics | Year: 2012

Grain-oriented (GO) silicon steel laminations are widely used in iron cores and shielding structures of power equipments. When the leakage magnetic flux is very strong and enters the lamination plane perpendicularly, the eddy current loss induced there must be taken into account in electromagnetic design. It is preferable to accurately compute three-dimensional (3-D) eddy currents at least in a few outer sheets of the lamination stack. Since the coating film applied to each sheet is only 2-5 μm thick, finite element modeling of 3-D eddy currents is very difficult in GO silicon steel laminations of large electromagnetic devices. This paper proposes an inner-constrained separation technique (ICST) to compute the 3-D eddy currents. Instead of the coating film, the ICST introduces an inner constraint into the A-formulation to separate the laminations from each other. By the ICST, the 3-D eddy currents can be computed accurately without meshing the coating film. Numerical experiments are carried out on the TEAM (Testing Electromagnetic Analysis Methods) benchmark model P21 cM1 and the numerical results show good agreement with the measured data. © 2012 IEEE.


Xie Q.,Baoding Tianwei Group Co. | Liao F.,North China Electrical Power University | Hu W.T.,Hebei Electrical Power Maintenance Company
Applied Mechanics and Materials | Year: 2014

A new high-precision method to orient the ultrasonic linear array signals was proposed in this paper. First, the Fast ICA algorithm was used to de-noise the ultrasonic linear array signals; then the TCT algorithm is used to focus the ultrasonic linear array signals to greatest extent to cumulate the position information of broadband signals, the Fast DOA is used to estimate the direction-of-arrival (DOA) of focused narrowband signals to speed up the calculation after focusing; Then, the application of partial discharge detection using this method was studied, the estimated accuracy of the method was simulated with different SNR(Signal to Noise Ratio) at first, the results show that the errors of DOA were about 2°; At last, the results from some experiments show that the errors were about 3. 5°, which indicates that this estimation method is with a good accuracy. © (2014) Trans Tech Publications, Switzerland.


Zhao X.,North China Electrical Power University | Lu J.,North China Electrical Power University | Li L.,Griffith University | Cheng Z.,Baoding Tianwei Group Co. | Lu T.,North China Electrical Power University
IEEE Transactions on Power Delivery | Year: 2011

An Epstein frame-like core model is set up to study the dc-biased problem of the power transformer. The harmonic phenomenon of the model under the dc bias condition is investigated by using the harmonic-balance finite-element method (HBFEM). The harmonic-balance finite element equation is coupled with the external electric circuit. Each harmonic component of the magnetizing current and magnetic field can be calculated directly in the harmonic frequency domains. Comparing the calculated results with the experimental data shows consistency. The dc bias effects on the magnetizing current and the magnetic induction are analyzed through the harmonic solutions. © 2010 IEEE.


Li H.,North China Electrical Power University | Li Q.,North China Electrical Power University | Xu X.-B.,Clemson University | Lu T.,North China Electrical Power University | And 2 more authors.
IEEE Transactions on Magnetics | Year: 2011

A modified method, which combines chaos optimization method and simulated annealing algorithm, is proposed to calculate the Jiles-Atherton (J-A) model parameters. The new method is validated by comparing its computation results with measurement data. Then, the validated J-A model is used in numerical modeling of Epstein frame, and the numerical results are found to be in good agreement with measurement data. © 2011 IEEE.


Wang Y.,North China Electrical Power University | Zhao S.-T.,North China Electrical Power University | He P.,Baoding Tianwei Group Co.
Gaoya Dianqi/High Voltage Apparatus | Year: 2011

The existing main wavelet denoising methods include threshold method, spatial correlation method, and modulus maximum method, however they all have some limitations. Combining the features and application ranges of the threshold method and modulus maximum methods, a new wavelet denoising algorithm was proposed and programmed in this paper. Moreover, the transformer's partial discharge signals were analyzed by the program. The experimental results demonstrate that the algorithm can eliminate white noise, and suppress strong electrical pulse interference to a certain extent, which suggests the algorithm can be applied in engineering to process transformer's partial discharge signals.


Xie Q.,Baoding Tianwei Group Co. | Cheng S.,North China Electrical Power University | Lu F.,North China Electrical Power University | Hou S.,North China Electrical Power University | Wang C.,North China Electrical Power University
Gaodianya Jishu/High Voltage Engineering | Year: 2013

The method of using ultrasonic array to locate partial discharge (PD) is one of the latest achievements in the modern array sensor technology and array signal processing technology. Thus, we practically adopted an improved circular ultrasonic array sensor to locate PD sources. Firstly, we developed an improved circular ultrasonic array sensor, thereby, we built a PD locating experimental platform in oil. Secondly, the phase mode excitation and the multiple signal classification (MUSIC) algorithms, combining with the multi-platform locating principle, were used to find direction of PD array signals and to locate the PD sources. Finally, the fast independent component analysis (FastICA) algorithm was used to de-noise the measured signals and to confirm their direction and locations. Results show that the locating accuracy of the improved circular array is better than that of traditional circular and the square array; by de-noising the array signals, the locating error is reduced to 4.9 cm which is less than 11.3 cm, the error in the case of no de-noising. Moreover, the validation of presented method is proved by a few experiments.


Song L.,Hebei University | Xiu-Ying L.,Baoding Tianwei Group Co. | Wen-Xu W.,Hebei University
Proceedings - 4th International Conference on Intelligent Computation Technology and Automation, ICICTA 2011 | Year: 2011

In order to improve the correct rate of transformer fault diagnosis based on three-ratio method of traditional dissolved gas analysis (DGA), a novel intelligent transformer fault diagnosis method based on both DGA and probabilistic neural network (PNN) was proposed. In this fault diagnosis method, it takes three characteristic values of the improved three-ratio method as its inputs and five transformer fault types as its outputs. And it selects the radial basis function, applies the one-against-one multiclass algorithm, and fully uses the superiority of PNN in processing finite samples. The efficiency of the proposed diagnosis method was tested by simulation of transformer fault diagnosis. The simulation results have shown that the better convergent speed, better generalization ability and higher accuracy are expressed in this proposed diagnosis method if a small data set is available. © 2011 IEEE.

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