Phase-locked system for three-phase alternating current power grid and phase-locked method

Abstract

The invention provides a phase-locked system for three-phase alternating current power grid and a phase-locked method. The phase-locked method comprises the following steps: receiving three-phase voltage of alternating current power grid and converting the three-phase voltage into two-phase voltage signals, and each phase of voltage signal comprises a positive sequence component and a negative sequence component; deducting the negative sequence component from each phase voltage signal, obtaining a pure positive sequence component through the coordinate conversion of Alpha Beta / dq and low pass filtering, and conducting phase locking of the pure positive sequence component; and deducting disturbance variable which is dominated by the negative sequence component from each phase voltage signal, further deducting the positive sequence component to obtain error signals, and obtaining signals which are dominated by the negative sequence component are gained through the coordinate conversion of Alpha Beta / dq and the low pass filtering of the error signals. By means of the phase-locked system for the three-phase alternating current power grid and the phase-locked method, the positive sequence component and the negative sequence component of the voltage of the power grid can be accurately obtained. Besides, due to the facts that a closed-loop compensation mode is adopted by the separation procedure of the negative sequence component and the phase lock of the separation procedure and the phase lock of the positive sequence component are strengthened by each other, the whole phase-locked procedure is enabled to be rapidly converged, pure positive sequence components can be rapidly obtained, and the precision of the phase lock is improved.

Description

technical field [0001] The invention relates to a phase-locking technology, in particular to a phase-locking system and a phase-locking method of a three-phase AC power grid. Background technique [0002] At present, with the development of science and technology and the great enrichment of people's material life, the accompanying energy and environmental problems are becoming more and more serious. Therefore, the development and utilization of renewable energy has become a popular research and development direction to solve the above problems. For example, wind power generation is well-deserved as one of many types of renewable energy due to its clean and environmentally friendly characteristics. [0003] The existing wind power system mainly adopts the Doubly Fed Induction Generator (DFIG), which uses a back-to-back dual pulse width modulation voltage source inverter as the main control system, and the inverter includes a grid-side converter And a rotor-side converter (or...

AI Technical Summary

Problems solved by technology

When the three-phase power grid is unbalanced due to a fault, the grid voltage includes positive sequence components and negative sequence components. In order to accurately obtain the phase information of the grid voltage, it is necessary to separate the negative sequence components to obtain pure positive sequence components. The phase-locking is carried out based on the positive-sequence component, but the existing phase-locking circuit design cannot completely separate the above-mentioned negative-sequence component, and the necessary separation measures are not taken for the interference contained in the grid voltage when the grid is unbalanced

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