Fast and accurate frequency detection method based on SOGI

Abstract

The invention discloses a fast and accurate frequency detection method based on SOGI, and the method comprises the steps: carrying out the sampling and normalization of a single-phase voltage signal,and carrying out the IIR low-pass filtering of obtained normalized floating point data, so as to eliminate the impact caused by harmonic waves and inter-harmonic waves; and separating in-phase and quadrature components of a filtered signal by using an SOGI module, obtaining active and reactive components according to dq conversion, wherein the reactive component is known to be 0 according to physical significance, correction is carried out according to the physical significance, accurate phase and frequency information is obtained, the obtained frequency is a fluctuation quantity, a stable frequency detection result can be obtained by using a mean filtering algorithm, the filter adopts a lower order, and the coefficient of the filter is obtained by a computer and stored in Flash for calling; and three-stage series connection can be adopted for mean filtering, so that the frequency detection range is expanded.

Description

technical field [0001] The invention belongs to the field of power system power quality of the present invention, and mainly aims at accurately detecting the frequency of the power grid, especially considering the situation of high harmonic components in the voltage of the power grid. Background technique [0002] With the rapid development of power electronics and information technology, the wide application of various nonlinear devices, the expansion of the grid scale and the increase of complexity, harmonic currents will inevitably be generated in the grid. Harmonic voltage is generated by harmonic current and grid impedance, so harmonic voltage is inevitable, and the harmonic voltage generated under weak grid is especially serious. [0003] Grid voltage zero-crossing detection is a frequency locking method adopted by many products. It has the advantages of being fast and simple. However, when the harmonic content of the power grid is high, the superposition of harmonics ...

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Problems solved by technology

However, the SOGI phase-locking algorithm also has its disadvantages. When the grid harmonics are high, multiple SOGI modules need to be combined to form the m-SOGI algorithm, which not only increases the amount of calculation, but also causes a long time delay, especially for the harmonic content of the grid voltage. When it is more complex, even when the grid voltage contains inter-harmonics, the computational complexity is greatly increased

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