Phase locking method for three-phase power system

Abstract

The invention discloses a phase locking method for a three-phase power system. The phase locking method includes the steps of subjecting a sampled three-phase voltage signal to lowpass filtering to acquire direct-current component in the three-phase voltage signal, subjecting the sampled three-phase voltage signal to fast Fourier transform to acquire amplitude of fundamental component in the three-phase voltage signal, subjecting the three-phase voltage signal to normalization calculation to acquire a three-phase voltage value with amplitude being 1 and not containing the direct-current component, performing DQ coordinate transformation on the three-phase voltage value and a phase position value theta outputted by a phase-locked loop to acquire component Uq of a q-axis under a rotating coordinate system, subjecting the Uq to loop filtering to acquire an angular frequency value, summing the angular frequency value and an initial angular frequency to acquire angular frequency, and performing integral operation on the angular frequency to acquire the phase position value outputted by the phase-locked loop. By the phase locking method, the phase-A fundamental wave phase position of imbalanced three-phase voltage or three-phase voltage with direct-current bias can be detected accurately and rapidly; the phase locking method is applicable to application occasions such as rectification with distorted input three-phase voltage.

Description

technical field [0001] The invention relates to the technical field of power signal synchronization, in particular to a phase-locking method for a three-phase power system, which can be applied to occasions such as three-phase PWM rectification and phase-controlled rectification that need to track three-phase voltage phases. Background technique [0002] In the rectification system, the real-time phase information is the benchmark to realize the accurate control of the output voltage, and it is also the guarantee of the reliability of the rectification system. Power quality disturbances in the power system such as the existence of harmonics, notches caused by rectifiers using grid commutation, disturbances caused by instantaneous switching of capacitors, phase jumps and frequency fluctuations caused by grid voltage sags, and three-phase voltage imbalances in the grid And other factors will affect the accuracy of fundamental signal frequency and phase measurement. Therefore,...

AI Technical Summary

Problems solved by technology

[0012] When the power grid drops, flickers, etc., it will cause three-phase unbalance; in the process of measurement and signal conversion, DC bias may be introduced

These faults will cause the traditional three-phase phase-locked loop to introduce harmonic components, affecting the accuracy of the output phase

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