Precise phase locking method based on cross decoupling self-adaptive complex filter

Abstract

The invention relates to a precise phase locking method based on a cross decoupling self-adaptive complex filter, which comprises the following steps: firstly carrying out the Clarke coordinate transformation on three-phase voltage input signals of Ua, Ub and Uc and obtaining voltage signals of Ualpha and Ubeta under an alpha-beta coordinate system; then leading the voltage signals to pass through the cross decoupling self-adaptive complex filter and extracting positive sequence voltage components Ualpha<+> and Ubeta<+> under the alpha-beta coordinate system; further carrying out the Clarke inverse transformation on the Ualpha<+> and the Ubeta<+> and obtaining three-phase voltage positive sequence components of Ua<+>, Ub<+> and Uc<+> under an a-b-c coordinate system; carrying out the Park transformation on the Ualpha<+> and the Ubeta<+> and obtaining a d-axis component Ud<+> and a q-axis component Uq<+> under a d-q coordinate system, wherein, the q-axis component Uq<+> reflects the positive sequence amplitude; leading the d-axis component Ud<+> to pass through a PI regulator and obtaining the frequency estimated value omega 0; feeding the omega 0 back to the cross decoupling self-adaptive complex filter and realizing the frequency self-adaption; and carrying out integration on the omega 0 for 1 / s for obtaining the positive sequence phase theta<+>. The precise phase locking method is characterized by simpleness, easy realization, high phase-locking precision and fast speed, thereby being particularly applicable to the precise phase locking of grid-connected converters under the extreme industrial field situations of power grid voltage distortion, three-phase voltage imbalance, large fluctuation range of voltage frequency and the like.

Description

technical field [0001] The invention belongs to a phase-locking method, in particular to an accurate phase-locking method based on a cross-decoupling adaptive complex filter. Background technique [0002] In the application field of grid-connected converters, grid voltage distortion, sag, unbalance and frequency fluctuations may occur in industrial power grids, which will affect the operation status of grid-connected converters. In order to achieve stable operation control of grid-connected converters, it is necessary Extract the positive sequence component of grid voltage and its amplitude and phase information. [0003] Traditional phase-locking methods mainly include: zero-crossing phase-locking method, synchronous rotating coordinate system phase-locking method, and positive and negative sequence rotating coordinate system phase-locking method. [0004] ① Zero-crossing phase-locking method: This method first establishes a phase reference table offline according to the g...

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Problems solved by technology

[0007] The purpose of the present invention is to solve the problems of large phase-locking errors and complex implementations in the above-mentioned prior art, and propose a precise phase-locking method based on cross-decoupling adaptive complex filters. Extract the positive sequence component of the grid voltage and its information under extremely harsh industrial site conditions such as unbalanced three-phase voltage and large-scale fluctuations in voltage and frequency, so that the grid-connected converter can achieve fast and accurate phase-locking under the above-mentioned harsh conditions

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