A three-phase software phase-locking method based on sliding dft filter principle

Abstract

The invention discloses a three-phase software phase-locked system and a phase-locked method based on the principle of sliding DFT filtering, and belongs to the technical field of phase-locked loops in electrical engineering. The phase-locking process of the present invention is: 1. Three-phase grid voltage U A , U B , U C The fundamental wave is firstly extracted through the sliding DFT algorithm; second, the obtained fundamental wave is then extracted by the method of extracting the positive sequence component of the fundamental wave based on the delay signal cancellation; the positive sequence signal of the three-phase grid voltage fundamental wave Fast and precise phase lock is achieved by SRF‑PLL. The invention can be used for very accurate extraction of the phase information of the positive sequence component of the fundamental wave of the grid voltage by the grid-connected power electronic device under the condition of severe distortion and unbalance of the grid voltage.

Description

Technical field [0001] In the field of phase-locked loop technology in electrical engineering, the present invention is more specifically, relating to locking ring technologies in the case of severe distortion of grid voltages. Background technique [0002] PLL-PHASE LOCKED LOOP is a combination of automatic phase control and automatic frequency control technology. The earliest has begun to study the phase locked loop since the 1930s, and the mathematical theory of locking rings has appeared in the early 1930s. In 1930, the scientists have established the basis of synchronous control theory. French engineers Bellescize issued a synchronous detection and mathematical description of the phase-locked loop in 1932, which is the first public publication of the math descriptors described in the phase locked loop. [0003] The phase locked loop has always been a linear circuit. The first phase locked loop is implemented with a discrete component, which is approximately an integrated cir...

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Problems solved by technology

[0011] The purpose of the present invention is to overcome the problem that the traditional software phase-locked loop cannot achieve phase-locking when the grid voltage is unbalanced and contains high-order harmonics, low-order harmonics and DC components at the same time, and provides a filtering principle based on sliding DFT The three-phase software phase-locking system and its phase-locking method, the invention innovatively combines the sliding DFT algorithm, the fundamental wave positive sequence component extraction method based on the delay signal cancellation and the traditional SRF-PLL, in the whole phase-locking process It can eliminate all kinds of interference contained in the three-phase grid voltage to achieve precise phase locking

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