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Method for frequency estimation of non-equilibrium power system

A frequency estimation and power system technology, applied in frequency measurement devices, frequency-to-amplitude conversion, etc., can solve problems such as the inability to obtain the frequency of the power system accurately and quickly, and achieve high steady-state convergence accuracy and robust anti-noise performance. Good, low computational complexity

Active Publication Date: 2017-05-17
SOUTHEAST UNIV
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Problems solved by technology

None of the existing frequency estimation methods for unbalanced power systems can accurately and quickly obtain the frequency of the power system

Method used

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  • Method for frequency estimation of non-equilibrium power system
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  • Method for frequency estimation of non-equilibrium power system

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Embodiment Construction

[0027] The present invention will be further explained below in conjunction with the accompanying drawings.

[0028] The voltage of a power system in a noise-free environment can be expressed in discrete time as:

[0029] v a (k)=V a (k)cos(wkΔT+φ)

[0030]

[0031]

[0032] Among them, V a (k), V b (k) and V c (k) respectively represent the peak value of the fundamental wave voltage component of the a, b, c three-phase voltage of the power system at time k, ΔT is the sampling interval, φ is the phase of the fundamental wave component, w=2πf is the angular frequency of the voltage signal, f is the system frequency. The time-dependent three-phase voltage can be transformed into a zero sequence and direct axis and orthogonal axis components v through the orthogonal αβ transformation matrix α and v β , as the Clarke transform

[0033]

[0034] factor It is used to ensure that the system power does not change under this change. When V a (k), V b (k) and V c...

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Abstract

The invention discloses a method for frequency estimation of a non-equilibrium three-phase power system. The method comprises the steps that the frequency of the non-equilibrium three-phase power system is estimated mainly on the basis of a widely-linear total least square self-adaption algorithm model, wherein the widely-linear model sufficiently utilizes three-phase voltage complete two-order information, and the frequency estimation robustness is enhanced. Compared with traditional linear self-adaptation estimation, the method is more applicable to the non-equilibrium system, and unbiased frequency estimation is given. Meanwhile, the model is not sensitive to changes of the three-phase voltage amplitude along with time passage and higher harmonic. The method is more stable and low in computation complexity, and the convergence performance, robust anti-noise performance and stable convergence precision are obviously improved.

Description

technical field [0001] The invention belongs to the field of power systems, in particular to a method for estimating the frequency of an unbalanced power system. Background technique [0002] In power systems, large dynamic frequency oscillations can trigger the failure of standard phasor-based frequency estimation techniques. Fast and accurate frequency estimation in the presence of harmonics, noise and unbalanced voltages has attracted much attention since variations from nominal values ​​can indicate unexpected abnormal system conditions and disturbances. [0003] Standard single-phase techniques are limited, especially when the selected phase is subject to voltage dips or transients. When considering line-to-line voltages, it is also difficult to select the most representative single-phase signal to fully describe the system frequency since there are six different single-phase voltages in a three-phase system. Therefore, the optimal solution is to design a framework th...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R23/06
CPCG01R23/06
Inventor 夏亦犁裴文江乔露露王开
Owner SOUTHEAST UNIV
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