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Your search keyword '"Liu, Kaipei"' showing total 7 results
Start Over Author "Liu, Kaipei" Topic harmonic analysis
7 results on '"Liu, Kaipei"'

3. Stability Assessment of Modular Multilevel Converters Based on Linear Time-Periodic Theory: Time-Domain vs. Frequency-Domain.

Author

Zhu, Shu, Liu, Kaipei, Le, Jian, Ji, Ke, Huai, Qing, Wang, Fangzhou, and Liao, Xiaobing

Subjects
*FLOQUET theory, *ELECTRIC transients, *STATE-space methods, *SYSTEMS theory, *PHASE-locked loops, *TIME-domain analysis
Abstract

The periodic characteristic of modular multilevel converter (MMC), which originates from the multi-harmonic couplings among internal dynamics, results in challenges to develop the linear time-invariant (LTI) model of MMC. The linearization of MMC is inherently around time-periodic equilibrium trajectory. In this paper, two different methods to assess small-signal stability of MMC are compared. Both are based on the linear time-periodic (LTP) systems theory, but one is in the time domain (TD) and the other is in the frequency domain (FD). The LTP model of MMC is derived from the linearized arm averaged model. Then, an LTI model for the LTP system is constructed in the FD through the harmonic state-space method. Small-signal stability analysis based on Floquet theory and generalized Nyquist criterion, that accompany TD and FD, are introduced and compared. It is demonstrated that models developed in both domains can effectively capture the small-signal behavior of MMC. Third and higher-order harmonic components of the states have significant effect on the impedance-based stability analysis of MMC around mid-frequency range. Analytical results are validated by electromagnetic transient simulations based on the MMC aggregated model. [ABSTRACT FROM AUTHOR]

Published
2022
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4. D-Q Frame Impedance Modeling of Modular Multilevel Converter and Its Application in High-Frequency Resonance Analysis.

Author

Zhu, Shu, Liu, Kaipei, Liao, Xiaobing, Qin, Liang, Huai, Qing, Xu, Yi, Li, Yuye, and Wang, Fangzhou

Subjects
*TIME delay systems, *MULTILEVEL models, *TRANSFER matrix, *DYNAMIC models
Abstract

A d-q frame impedance model of modular multilevel converter (MMC), which is suitable for high-frequency resonance (HFR) analysis under the condition that the number of submodules in MMC reaches hundreds level, is presented in this work. A 10th-order dynamic phasor model for the MMC is linearized and combined with a control subsystem model. A modular modeling approach based on transfer matrix is applied to the overall linearized model to derive the impedance model. The validity and accuracy of the model are verified using a 501-level MMC aggregated model in SIMULINK. Results show that the impedance model has satisfactory accuracy in the frequency ranging from 1 to 3000 Hz. Then, the impedance model is used to analyze an HFR accident in a realistic MMC project. Therefore, a high time delay in controller is proved can provide negative resistance in high frequency and cause instability. [ABSTRACT FROM AUTHOR]

Published
2021
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5. The 7-terms Harris window and interpolated FFT harmonic analysis method for electrified railway

Author

Liu Kaipei, Wang Ling, Sheng Chao, Wu Jie, and Wang Li

Subjects
Harmonic analysis, Sampling (signal processing), Computation, Fast Fourier transform, Phase (waves), Harmonic, Electronic engineering, Window (computing), Algorithm, Window function, Mathematics
Abstract

This paper presents the 7-term Harris window and interpolated FFT harmonic analysis method for electrified railway. In addition, the paper discusses the harmonic characteristics of electrified railway and the sidelobe characteristics of the 7-term Harris window. Whenanalysis harmonic signal, good sidelobe characteristics of window function are needed. While the characteristics of the mainlobe do not matter so much. We propose increasing the numbers of terms in the window function to get better sidelobe characteristics at the expense of losing some mainlobe characteristics. The experimental results show that the algorithm in the case of non-synchronous sampling has high harmonic frequency, amplitude, and phase calculation accuracy, that selective harmonic analysis reduces the computation time by 50%.

Published
2014
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6. Harmonic Detection Based on the TLS Estimation Algorithm

Author

Liu Kaipei and Zhang Jun-min

Subjects
Least mean squares filter, Harmonic analysis, Noise, Finite impulse response, Convergence (routing), Harmonic, Signal processing algorithms, Algorithm, FSA-Red Algorithm, Mathematics
Abstract

Based on the Newton learning algorithm, a new algorithm for TLS estimation and its application in harmonic detection is presented in this paper. It is shown that the LMS algorithm and Constrained Anti-Hebbian algorithm are two examples of the proposed algorithm in this paper. To solve the contravention between the detecting precision and speediness, analog detecting architectures are studied. The simulation results show that its noise rejection capability is superior to those of the LMS and Constrained Anti-Hebbian algorithms and the new algorithm gives faster convergence and better precision than another two methods.

Published
2006
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7. An Improved Support Vector Machine Method for Harmonic and Inter-harmonic Detecting

Author

Lei Xiao, Ma Li, and Liu Kaipei

Subjects
Mathematical optimization, Iterative method, Computer science, Topology, Least squares, Discrete Fourier transform, Harmonic analysis, Support vector machine, Discrete Fourier transform (general), Frequency domain, Least squares support vector machine, Harmonic, Algorithm, Mathematics
Abstract

Based on the linear regressive model of support vector machines, iterative re-weighted least squares of the support vector machines for signal spectral analysis is introduced by virtue of abstract expressions of cost functions, and the uniform mathematical analytical expression of support vector machine for solving the problem of signal spectral analysis is obtained. And a new method is presented by changing resolution, namely defining the range of spectrum by taking advantage of wide range with rough resolution at first, and then using narrow range with high resolution. The simulation has showed that this method solves the problem of large calculation and slow calculating speed.

Published
2006
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