A new load detection method was presented based on its running status of powersystem. The loads are sorted according to their index of capacitive, inductive, and none-linear. The static character of each load was got...
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A new load detection method was presented based on its running status of powersystem. The loads are sorted according to their index of capacitive, inductive, and none-linear. The static character of each load was got according to the time-distribution. The concept of load detection is completed. The data-sample and wave recording equipment is designed and assembled based on the DSP for power loads status detecting. The superior software was designed for data management and analyzing. The recognizing status data was analyzed in both time-domain and frequency-domain; the identifying method for electric power loads status is deduced based on the correlation coefficient; the mathematical model for the status identifying is built; the trueness and validity of the methods is verified based on the testing and analyzing
monitoring the partial discharge (PD) on site in cables accessories is now a more effective method of cable tests. Meaningful PD measurement can obtain reliable information on the condition of sealing ends and joints ...
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monitoring the partial discharge (PD) on site in cables accessories is now a more effective method of cable tests. Meaningful PD measurement can obtain reliable information on the condition of sealing ends and joints after installation or several years of operation which can contribute to considerable overall reduction of error risk. The UHF (ultra high frequency) method is an effective PD detection method. It shows out the superiority in measurement sensitivity and suppressing interference. It has been confirmed that the frequency of the PD pulse generated in cables can reach up to GHz, while the frequency of background noise usually lies below 400 MHz. Experiments show that the UHF PD pulse can radiate from the disconnection between the shields in the sealing ends or the joints, and it can also radiate out along the ground wire or the cross-linked wire. Moreover, the detection by UHF sensor towards four different types of PD models have been done in laboratory, such as sliding discharge model, floating discharge model, protrusion discharge model and cavity discharge model. Mass of statistic results of these PD pulses indicate the distinct characteristics. It can help to do the pattern recognition research, even to do further research on fault diagnosis for XLPE cables.
power quality becomes an emphasis of related researches. Based on the detailed study on QCC (quality control center) of the FRIENDS first advanced by Japanese scholars, the functions of QCC are expanded and its basic ...
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power quality becomes an emphasis of related researches. Based on the detailed study on QCC (quality control center) of the FRIENDS first advanced by Japanese scholars, the functions of QCC are expanded and its basic types and structures are defined. Meanwhile, by detailed study, this paper introduces the multiple adjusting functions of UPQC (unified power quality conditioner) which is the chief part of QCC and presents its typical topological circuit. Moreover, H infin control technology is used to realize the synthesis tracking compensation of voltage and current for UPQC. Finally its validity has been testified successfully
This paper presents a theoretically analytical technique for determining the spectral components of high-power multilevel voltage source converters. The technique uses double Fourier series to analyze the output wavef...
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This paper presents a theoretically analytical technique for determining the spectral components of high-power multilevel voltage source converters. The technique uses double Fourier series to analyze the output waveform of multilevel asynchronous asymmetrical regular sampling SVPWM converter. The 3-D spectrum representation of the SVPWM based on the extension geometrical-wall-model is given in this article. According to the analytical method of two-level SVPWM and the phase-shifted carrier PWM, the new DFS of multilevel SVPWM of single phase is obtained. In order to validate the theoretically analytical method, a six modules cascaded H-bridge converter model using PSCAD is built. By comparing the spectrum and waveform calculated with the simulation, the correctness of the analytical formulas has been proved. And the technique can act as the method of selection PWM. Moreover, the technique can be used to analyze the output waveform of the high-voltage and high-power FACTS equipments, such as SVG, SSSC, UPQC
A new ultra high-speed protection scheme is proposed in this paper. Using wavelet transform with multiresolution analysis, the current signals is decomposed into a series of detailed wavelet components. The spectral e...
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ISBN:
(纸本)9810557027
A new ultra high-speed protection scheme is proposed in this paper. Using wavelet transform with multiresolution analysis, the current signals is decomposed into a series of detailed wavelet components. The spectral energies of the wavelet components are calculated and then employed to detect the faults. Characteristics of the proposed ultra high-speed protection algorithm are analyzed and results of simulation studies are given. The results show that the proposed algorithm is promising and easy to implement for computer relaying application
A new non-unit voltage protection algorithm for extra high voltage (EHV) transmission lines is presented in this paper. The singularity of fault transient voltage signals in one terminal is utilized to discriminate cl...
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ISBN:
(纸本)9810557027
A new non-unit voltage protection algorithm for extra high voltage (EHV) transmission lines is presented in this paper. The singularity of fault transient voltage signals in one terminal is utilized to discriminate clearly between internal and external faults. Lipschitz exponent (LE) is obtained from wavelet modulus maximum to detect singularity of signals. A typical 500 kV EHV transmission system has been simulated by ATP to evaluate the scheme. The simulation results show that this scheme is capable of providing correct responses under various system configurations and fault conditions
作者:
F.F. SongT.S. BiQ.X. YangSi Fang Research Institute
Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Beijing China
In this paper, the state of the arts of powersystems in China and some applications in transient stability control based on wide area measurement system (WAMS) are introduced briefly. With the development of power gr...
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In this paper, the state of the arts of powersystems in China and some applications in transient stability control based on wide area measurement system (WAMS) are introduced briefly. With the development of power grid interconnection and transmission utility deregulation, the operation of electric powersystem become more and more complex, which challenges the security and transient stability control of powersystems. The advent of WAMS opens a new path to the system trajectory prediction and real time closed-loop stability control to prevent powersystem outage. The defects of current transient stability controlsystem are analyzed, then a possible scheme of transient stability control based on WAMS is proposed, and the corresponding future work is put forward as well. Finally, a new way of solving cascading events is discussed
The paper studies a practical project of 2 MVA dynamic voltage restorer on the basis of transformer-less cascade multilevel topology, it discusses each part working principle of DVR, but also provides a practical volt...
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The paper studies a practical project of 2 MVA dynamic voltage restorer on the basis of transformer-less cascade multilevel topology, it discusses each part working principle of DVR, but also provides a practical voltage sag problem solving scheme for a 6 kV feed line based on proposed cascade structure. EMTDC/PSCAD based simulation results verify the validity of proposed scheme
This paper presents an integrated framework for the optimal management of electricity purchase allocation and risk for load service entities (LSEs). To the practice of China power Markets, we propose the framework of ...
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This paper presents an integrated framework for the optimal management of electricity purchase allocation and risk for load service entities (LSEs). To the practice of China power Markets, we propose the framework of power portfolio of combined physical forward contract and spot market. The framework suggests that the forward contracts should have different prices on-peak and off-peak in accord with sale prices distinguish on-peak and off-peak. The optimal purchase problem is described by the utility maximum integrated the rate of return and risk tolerance level, and risk is evaluated by Value at Risk (VaR). The analytical solution is also conducted. The numerical results are reasonable with higher rate of return and better risk hedging compared with the corresponding results from the existing portfolio selection approach. The presented framework gives one possible and effective method for the optimal power portfolio and risk management in incomplete power markets.
Based on mathematical morphology and grille fractal, a novel approach on power quality disturbance detection and location is presented in this paper. At first a parallel composite morphological filter with multiple-st...
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Based on mathematical morphology and grille fractal, a novel approach on power quality disturbance detection and location is presented in this paper. At first a parallel composite morphological filter with multiple-structure elements is designed to filter the random noise and impulse noise in power quality disturbance signals. Then to the filtered curves, an easy implementation criterion for singularity detection based on the change regularity of grille fractal is proposed to locate the start and end time that disturbance occurs. The voltage sag, swell, harmonic and their combined disturbances are used to verify the validity of the proposed filter-location approach. Numerical results show that the proposed approach is valid and effective
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