Phase angle tracking method for power grid

Abstract

The invention discloses a phase angle tracking method for a power grid. The phase angle tracking method includes steps of 1), acquiring three-phase voltage of the power grid to obtain three-phase voltage instantaneous values; 2), obtaining components U alpha and U beta of the voltage of the power grid in a two-phase static coordinate system according to 3/2 conversion; 3), calculating instantaneous phase angles of the power grid by the aid of arc tangent transformation; 4), calculating an instantaneous step value according to an equation of delta theta=theta i-theta i-1; 5), calculating phase step within a working frequency period when an absolute delta theta is larger than 4Xpi /3 according to an equation of theta s=T/K; 6), determining upper and lower envelope curves according to equation of LH(i)=theta sXi+theta s/3 and LL(i)=theta sXi-theta s/3; and 7), setting theta(i) as a true value if LH (i) is larger than or equal to theta (i) and theta (i) is larger than or equal to LL (i), setting LH (i) as a true value if theta (i) is larger than LH (i), and setting LL (i) as a true value if theta (i) is smaller than LL (i). By the aid of the phase angle tracking method, phase angles and frequencies of the power grid can be precisely calculated.

Description

technical field [0001] The invention relates to electric power supply technology, in particular to a method for tracking the phase angle of a grid. Background technique [0002] At present, the phase sequence and phase angle detection of the power grid mostly adopts the method of hardware phase-locked loop and software phase-locked loop. The hardware phase-locked loop generally uses the zero-crossing point of the grid voltage to track the grid frequency, and then uses the frequency multiplier phase-locked circuit to calculate the phase angle of the grid. The software phase-locked loop is also based on capturing the zero-crossing pulse in the hardware phase-locking, and then performs a series of phase-locking calculations. However, the grid voltage is near the zero-crossing point, which is easily disturbed, and repeated zero-crossing occurs. Although the hysteresis comparison circuit is used Repeated zero-crossing is avoided, but the problem of inaccurate zero-crossing detect...

AI Technical Summary

Problems solved by technology

Because the frequency of the power grid changes slightly, and the three-phase voltage is not an ideal sine wave, especially in the industrial environment, under the influence of a large number of capacitive and inductive loads and

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