Short-window power frequency component extraction algorithm used in transient saturation calculation of current transformer

Abstract

The invention provides a short-window power frequency component extraction algorithm used in transient saturation calculation of a current transformer. The algorithm comprises the following steps that 1. an effective order number is determined, and a sampling rate is calculated: a control system estimates an order number upper limit value Lmax according to an experience formula in the time sequence analysis, in addition, a sample matrix R is constructed according to the Lmax, the sample matrix R is subjected to SVD (singular value decomposition) to obtain a singular value Sigma i, the log koc of the singular value Sigma i is taken, and the control system judges the effective order number value p and selects the sampling rate used for calculation; 2. the fault current power frequency component is calculated: the control system forms each element of an augmented sample matrix according to a new sampling sequence xD after the frequency division, in addition, an augmented sample matrix equation and a feature equation are constructed, and the control system calculates the vibration amplitude Ai, the phase theta i, the attenuation factor alpha I and the frequency fi of each component. The algorithm provided by the invention has the advantages that non-saturation section data after transient saturation of the current transformer can be utilized in a shorter data window for fast extracting the amplitude value and the phase of the power frequency component in the fault current.

Description

technical field [0001] The invention belongs to the technical field of transient saturation calculation of a current transformer (TA), and in particular relates to a short-window power frequency component extraction algorithm used in the transient saturation calculation of a current transformer. Background technique [0002] The current transformer is an important component of the relay protection system, and its accurate transmission and transformation of the primary current is the first prerequisite for the correct operation of the relay protection. The P-level TA widely used in the power grid is only selected according to the maximum steady-state short-circuit current during configuration, and the transient saturation problem is not considered. The previous grid structure was simple, the short-circuit current was small, and the problem of TA transient saturation was not prominent. With the rapid growth of the grid scale, the short-circuit current increases sharply, and t...

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Problems solved by technology

The compensation method uses the excitation current to compensate the distorted secondary current to obtain the primary current. It is difficult to accurately measure the initial magnetic flux and saturation magnetic flux, which will affect the calculation results.

The neural network has good nonlinear fitting ability and can be used to restore the primary current. It uses more samples and has poor stability.

The least squares method uses the data of the unsaturated section of the secondary current to approximate the fault current in the form of a first-order Taylor series. large amount

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