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A Frequency Estimation Method for Unbalanced Power System Based on ipdft

A technology of frequency estimation and power system, which is applied in the field of power system, can solve the problems that the power system cannot be obtained accurately and quickly, and achieve the effects of reducing complexity, good anti-noise performance, and enhancing robustness

Active Publication Date: 2019-12-06
南京福致通电气自动化有限公司 +1
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  • Application Information

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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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  • A Frequency Estimation Method for Unbalanced Power System Based on ipdft
  • A Frequency Estimation Method for Unbalanced Power System Based on ipdft
  • A Frequency Estimation Method for Unbalanced Power System Based on ipdft

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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] where V a (n), V b (n) and V c (n) represents the peak value of the fundamental voltage component of the three-phase voltages a, b, and c of the power system at time n, respectively, φ is the phase of the fundamental component, ω 0 is the discrete-time system angular frequency. The time-dependent three-phase voltages are transformed into zero sequences v by Clarke's quadrature αβ transformation matrix 0 (n) is the direct axis and the orthogonal axis component v α (n) and v β (n):

[0034]

[0035] factor 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 (n) are the same, v 0 (n)=...

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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, and particularly relates to a frequency estimation method for an unbalanced power system based on IpDFT (Interpolation Discrete Fourier Transform). Background technique [0002] In power systems, large dynamic frequency oscillations can trigger faults in standard phasor-based frequency estimation techniques. Fast and accurate frequency estimation in the presence of harmonics, noise, and unbalanced voltages has attracted a great deal of attention because variations from nominal 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 the line-to-line voltage, it is also difficult to select the most representative single-phase signal to adequately describe the system frequency due to the existence of six different single-phase voltages in a three...

Claims

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Application Information

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Patent Type & Authority Patents(China)
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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