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EMD (Empirical Mode Decomposition) based boundary element method for ultra high voltage DC transmission lines

A technology for UHV DC and transmission lines, which is applied to electrical components, emergency protection circuit devices, etc., and can solve problems such as DC protection device refusal to operate, influence of directional traveling wave change rate, and susceptibility to noise interference, etc.

Active Publication Date: 2013-04-10
KUNMING UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, relevant data show that the currently used DC line traveling wave protection (mainly provided by ABB and SIEMENS) is susceptible to noise interference and misoperation to varying degrees.
Or due to problems such as the change rate of directional traveling wave being affected by the transition resistance, sometimes the existing DC protection device will refuse to operate

Method used

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  • EMD (Empirical Mode Decomposition) based boundary element method for ultra high voltage DC transmission lines
  • EMD (Empirical Mode Decomposition) based boundary element method for ultra high voltage DC transmission lines
  • EMD (Empirical Mode Decomposition) based boundary element method for ultra high voltage DC transmission lines

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Embodiment Construction

[0054] Simulation model such as figure 1 As shown, a positive ground fault occurs at a distance of 150km from the protection installation, the time window length is 1ms, and the sampling frequency is 100kHz.

[0055] (1) After the DC line fails, the starting element starts immediately, according to the formula:

[0056] u 1 =(u + -u - ) (1)

[0057] Find the line-mode voltage u 1 , the line-mode voltage waveform is as Figure 4 as shown in (a);

[0058] (2) EMD decomposes the line-mode voltage to obtain a matrix of c[m, n], where m is the number of IMF components obtained from the decomposition (if there is a residual component r, the decomposed r is also regarded as IMF), n=100, the IMF component is the instantaneous amplitude in time domain space.

[0059] (3) On the one hand, the absolute values ​​of the m IMF components are calculated to obtain m |IMF t (i)|; On the other hand, Hilbert transform is performed on the decomposed IMF components ...

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Abstract

The invention relates to an EMD (Empirical Mode Decomposition) based boundary element method for ultra high voltage DC transmission lines, which comprises the following steps of: when DC lines break down, after a protective element is started, resolving line-mode voltage by using the phase-mode transformation theory according to DC voltages at both poles measured at the installation position of the protective element; performing EMD on discrete line-mode voltage signals with the sequence length of 100 dots to obtain m IMF (Intrinsic Mode Function) components; on one hand, resolving the absolute value of each IMF component, and on the other hand, carrying out Hilbert transformation on each IMF component subjected to EMD to work out an instantaneous frequency; dividing the product of the absolute value of an instantaneous amplitude and the corresponding instantaneous frequency by a sampling frequency to obtain an instantaneous kt value; adding m instantaneous kt values together; and taking the maximum in time-domain space as the ultimate criterion k to distinguish faults in or outside areas. A large number of simulation results show that the method has good effect.

Description

technical field [0001] The invention relates to the technical field of electric power system relay protection, in particular to an EMD decomposition-based boundary element method for UHV DC transmission lines. Background technique [0002] The DC transmission line not only has a large transmission power, but also requires the line protection device to remove the fault as soon as possible after the line fails, otherwise it will cause a great impact on the entire system and pose a threat to the safe and stable operation of the system. However, the general power frequency protection operates slowly and takes a long time, which is difficult to meet the requirements of DC transmission line protection. At present, traveling wave protection is widely used in the world as the main protection of high-voltage DC line protection. Its single-ended protection is based on the sudden change of voltage traveling wave, the rate of change of voltage traveling wave and the gradient of current ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02H7/26
Inventor 束洪春安娜田鑫萃张广斌孙士云刘可真方毅贺婷戴月涛白挺玮王旭邬乾晋
Owner KUNMING UNIV OF SCI & TECH
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