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21 results on '"Liu, Cuicui"'

3. Fault Diagnosis of Commutation Failure Using Wavelet Transform and Wavelet Neural Network in HVDC Transmission System.

Author

Liu, Cuicui, Zhuo, Fang, and Wang, Feng

Subjects
*WAVELET transforms, *FAULT diagnosis, *VALUE engineering, *ROOT-mean-squares, *HIGH voltages, *DIAGNOSIS methods
Abstract

Commutation failure is the most common fault on the inverter side of the high voltage direct current (HVDC) transmission system. In the actual engineering operation, there are many reasons for the commutation failure. In order to diagnose the causes in real-time and effectively, this article proposes a new method for the fault diagnosis of the commutation failure based on the combination of the wavelet transform and wavelet neural network (WNN). First, by analyzing the changes in electrical characteristics caused by the failure of commutation, the voltage signal of the inverter side commutation bus is finally selected as the feature signal for diagnosis. Then, the wavelet transform is used as a tool for extracting fault feature quantities, and the root mean square (rms) value of the wavelet detail coefficients, wavelet energy skewness, and wavelet energy spectrum information entropy of the inverter side commutation bus voltage signal after wavelet decomposition are used as three feature parameters. At the same time, wavelet packet decomposition is performed on the inverter side commutation bus voltage signal, and the wavelet packet subband energy, energy entropy, and energy skewness are extracted as the other three feature vectors. Finally, the simulation test data shows that the proposed fault diagnosis method can accurately identify the specific fault causes and has high reference value and specific engineering guiding significance for improving the reliability of the HVDC transmission system. Compared with the traditional BP neural network method for fault diagnosis of commutation failure, the proposed diagnosis method considers the fault type more comprehensively, the diagnosis speed is faster, and the recognition accuracy rate is higher in the case of a small number of samples. [ABSTRACT FROM AUTHOR]

Published
2021
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4. Design of MHz Level Planar Transformer and Analysis of Leakage and Loss

Author

Liu Cuicui, Zhao Xiaokang, Zhang Jie, and Yun Zhao

Subjects
Leakage inductance, Switched-mode power supply, Computer science, business.industry, Flyback converter, Electrical engineering, law.invention, Inductance, Planar, Magnetic core, Electromagnetic coil, law, business, Transformer
Abstract

Planar transformer is an important factor to achieve high power density and high efficiency of switching power supply. In this paper, a MHz level planar transformer is designed based on flyback converter. First of all, according to the smallest structural constant of PCB core, the magnetic core is selected. The working flux density is selected preliminarily based on the relationship between magnetic core loss and temperature rise, and the number of primary side turns and line width is further calculated. The design of planar transformer structure is further accomplished in the magnetic element design software Ansoft Pexprt, and the leakage inductance and loss of planar transformer is simulated in the finite element analysis software Maxwell 2D. According to the simulation design, the layout of the printed circuit board of transformer is made, and the leakage loss is tested and calculated. The correctness of the design of planar transformer is verified.

Published
2018

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