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IpDFT-based frequency estimation method of non-equilibrium electric power system

A frequency estimation and power system technology, applied in the field of power systems, can solve problems such as inability to obtain power systems accurately and quickly, and achieve the effects of reducing complexity, enhancing robustness, and good anti-noise performance

Active Publication Date: 2018-05-11
南京福致通电气自动化有限公司 +1
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Problems solved by technology

Most of the existing frequency estimation methods for unbalanced power systems cannot accurately and quickly obtain the frequency of the power system

Method used

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  • IpDFT-based frequency estimation method of non-equilibrium electric power system
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  • IpDFT-based frequency estimation method of non-equilibrium electric power system

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Embodiment Construction

[0028] The present invention will be further explained below in conjunction with the accompanying drawings.

[0029] The three-phase voltage of a power system in a noise-free environment can be expressed in discrete time as:

[0030] v a (n)=V a (n)cos(ω 0 n+φ)

[0031]

[0032]

[0033] Among them, V a (n), V b (n) and V c (n) represent the peak values ​​of the fundamental voltage components of the a, b, and c three-phase voltages of the power system at time n, φ is the phase of the fundamental component, and ω 0 is the angular frequency of the discrete-time system. The time-dependent three-phase voltage is transformed into a zero sequence v by Clarke's orthogonal αβ transformation matrix 0 (n) is the direct axis and orthogonal axis component v α (n) and v β (n):

[0034]

[0035] factor It is used to ensure that the system power does not change under this change. In a balanced power system, that is, when V a (n), V b (n) and V c When (n) is the same...

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Abstract

The present invention discloses an IpDFT(Interpolation Discrete Fourier Transform)-based frequency estimation method of a non-equilibrium electric power system. The problem of non-circular signal employed frequency estimation in a non-equilibrium condition is solved based on modeling of complex-valued signals deduced from a three-phase voltage through orthogonal [Alpha][Beta]transformation. The newest progress obtained through enhanced complex-valued second-order statistics is employed, and in a non-equilibrium condition, the complex-valued signals are second-order non-circular signals. In theinvention, interpolation Fourier transform is employed to estimate frequency of the signals, the non-circular signals are converted to sinusoidal signals through simple calculation, positive and negative frequency components are considered, and therefore, the estimation accuracy of the frequency is improved and the calculation is simple. Compared to traditional linear adaptive estimation, the method is more suitable for the non-equilibrium system, gives out unbiased frequency estimation, and is not sensitive to frequency change. The method is more stable and low in calculation complexity, andis improved in robustness anti-noise performance and estimation precision.

Description

technical field [0001] The invention belongs to the field of power systems, in particular to an IpDFT (interpolation discrete Fourier transform)-based frequency estimation method for unbalanced power systems. 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 great attention since variations from nominal values ​​can cause 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...

Claims

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Application Information

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IPC IPC(8): G01R23/16G01R23/02
CPCG01R23/02G01R23/16
Inventor 王开薛峰郭履翔谢庆明
Owner 南京福致通电气自动化有限公司
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