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The stability of HVDC system is under the influence of the strength of AC system, which is reflected as the AC and DC short-circuit ratio(SCR) on the converter stations. In this paper, a simulation study is carried out on the sending end of a certain HVDC system that has been put into operation under different SCR, using PSCAD/EMTDC. The simulation indicates that with the reduction of SCR, the recovery...
The component long-term failure and severity indices used in existing methods can not present time-varying characteristics when we assess the catastrophic event occurring in the power grid. A new method is presented in this paper based on uncertain measure. The credibility measure and global fuzzy security index are used to represent the possibility and severity of cascading failures. The N-l contingency...
This paper proposed a new method to estimate voltage flicker using the discrete Fourier transform (DFT). Based on the specified signal processing recommendations by IEC61000-4-7, the proposed method obtains the amplitude, frequency and phase angle of each harmonic/interharmonic using the odd points interpolation correction method. According to the electric power distortion component symbiosis mechanism,...
Measurement of harmonics/inter-harmonics based on the technique of enhanced phase-locked loop is unpractical dues to its slowly transient response speed. A new method which improves the technique of enhanced phase-locked loop by bringing in the theory of relaxation iteration is proposed: Taking the theory of relaxation iteration for the solution of nonlinear equation into account in the premise of...
Currently there are various data processing methods in power quality monitoring system, and this paper put forward a new data processing method based on data preprocessing, reason able choice of time interval for analysis and generating daily statistical file. According to IEC international standard, it is effective to get clear and explicit graphs and quickly generate different statistical reports...
This paper introduces DCT (discrete cosine transform) into short time disturbances detection. DCT coefficients of sampled signal about short time power quality disturbances (voltage sag, voltage swell and voltage interruption) in serious noises can be extracted through DCT transform, and a difference sequence can be extracted through DCT coefficients, then disturbance characteristics can be detected...
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