A Digital Phase-Locking Method Applied to Active Power Filter
A power filter, digital phase locking technology, applied in the direction of electrical components, automatic power control, etc., can solve the problems of zero point detection error, phase offset, can not meet the dynamic adjustment of APF, etc., to achieve convenient calculation, small amount of calculation Effect
Active Publication Date: 2017-09-05
CENTURAY TECH CO LTD
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Problems solved by technology
But there are problems: 1. In a grid voltage fundamental wave cycle, only two zero-crossing detections can be performed on the single-phase grid voltage signal, that is, the phase signal is only adjusted twice in one cycle. The simultaneous detection of three phases can only be adjusted 6 times; 2. The detection of the zero point generally has a large error, and there is a large delay in high-frequency applications
The phase detection technology based on the static coordinate system, the detection results will be affected by the voltage imbalance of the three-phase power grid, and a certain phase offset will be introduced while filtering certain harmonic effects, which also cannot meet the requirements of dynamic adjustment of APF
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[0023] Refer to attached figure 1 The embodiment of the digital phase-locking method applied to the active power filter of the present invention will be further described in detail.
[0024] The three-phase symmetric system has the characteristics of 120° rotational symmetry in time, and its composite quantity forms a rotation vector with constant size and time-varying in space, its rotation speed is the system angular velocity ω=2πf, and the initial phase angle is A phase initial angle. Therefore, the phase of the three-phase system can be determined by locking the phase angle of phase A.
[0025] Utilizing the same characteristics of the rotation curve of the three-phase system in space and the phase A, the triangular value of the current phase of the system can be calculated in real time by applying the triangular transformation relationship of mathematics. The derivation process is as follows:
[0026] Let A-phase system voltage U m cos(ωt+θ), U m is the phase voltage...
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The invention discloses a digital phase locking method applied to an active power filter. The characteristic that the spatial rotation curve of a three-phase system is the same as that of a phase A is used, and trigonometric values of the current phase of the system can be worked out in real time by applying the mathematic trigonometric conversion relationships. Meanwhile, the digital phase locking method applied to the active power filter has the advantages that calculation is convenient and the calculation amount is small.
Description
technical field [0001] The invention relates to a control method of an active power filter, more specifically, it relates to a digital phase-locking method applied to an active power filter. Background technique [0002] Phase-locked loop (phase-locked loop) is a method to stabilize the frequency in radio transmission. It mainly includes VCO (voltage-controlled oscillator) and PLL IC (phase-locked loop integrated circuit). The voltage-controlled oscillator gives a signal , one part is used as the output, and the other part is compared with the local oscillator signal generated by the PLL IC through frequency division. In order to keep the frequency constant, the phase difference is required not to change. If there is a change in the phase difference, the voltage output of the PLL IC The voltage at the terminal changes to control the VCO until the phase difference is restored to achieve the purpose of frequency locking. A closed-loop electronic circuit that maintains a deter...
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IPC IPC(8): H03L7/08
Inventor 林道飞金良赞林婷婷
Owner CENTURAY TECH CO LTD