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Improved method for low-voltage ride-through phase-locking of grid-connected converter

A low-voltage ride-through and converter technology, applied in the field of power electronics, can solve problems such as slow control loop response, unreasonable proportional and integral parameters, and phase-lock failure.

Inactive Publication Date: 2018-04-10
XIAN XJ POWER ELECTRONICS TECH
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  • Application Information

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Problems solved by technology

[0006] During the period of low voltage ride through, the grid voltage can drop to zero at the lowest, at this time the output Q-axis voltage U q Very low, if not dealt with, the proportional-integral parameters designed according to the normal state are unreasonable, and the response of the control loop is too slow, which may lead to phase-lock failure

Method used

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  • Improved method for low-voltage ride-through phase-locking of grid-connected converter

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Embodiment Construction

[0028] The structure of the three-phase grid voltage phase-locked loop of the conventional grid-connected converter is as follows: figure 1 shown. The output Q-axis voltage U of the three-phase grid voltage after coordinate transformation q Add 2πf adjustment after proportional-integral transformation, and get the phase θ changing between [0,2π] after integral and 2π remainder g .

[0029] In the case of ideal three-phase voltage, the three-phase voltage is set as:

[0030]

[0031] Also set the abc / dq transformation formula as:

[0032]

[0033] Let the output phase angle of the phase-locked loop be Then there are:

[0034]

[0035] It can be seen from the above formula that when the When , that is, the output phase of the phase-locked loop is synchronized with the phase of the A-phase voltage, then there is Therefore, by controlling U q = 0 to get

[0036] The structure of the three-phase grid voltage low-voltage ride-through phase-locked loop is as fo...

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Abstract

The invention discloses an improved method for low-voltage ride-through phase-locking of a grid-connected converter. When the voltage drop of a grid is k times higher than a rated value, double rotation coordinate transformation is performed to obtain a positive-sequence Q-axis voltage Uq for per-unit processing. When the voltage drop of the grid is k times lower than the rated value, the input ofa proportional integral part is disconnected, and the output of a phase-locked loop is maintained through the integral part. According to the invention, the problem of phase-locked failure due to unreasonable proportional-integral parameters because the voltage drop causes a decrease in the Q-axis voltage Uq is avoided through the per-unit processing, and the problem of phase-locked failure due to an over-low grid voltage is avoided by maintaining the output of the phase-locked loop through the integral link.

Description

technical field [0001] The invention belongs to the technical field of power electronics, and in particular relates to an improved method for low-voltage ride-through phase-locking of a grid-connected converter. Background technique [0002] With the depletion of traditional energy and the environmental pollution and greenhouse effect caused by the use of fossil energy, new energy represented by wind energy and solar energy will gradually replace traditional energy and become the dominant force in the future energy structure. [0003] New energy is generally connected to the power system through power electronic equipment. With the continuous expansion of new energy grid-connected capacity, the increase of penetration rate will have a non-negligible impact on the safe operation of the power system. Inject reactive components to facilitate grid recovery, which is the low voltage ride through (LVRT) requirement in grid-connected rules. [0004] The new energy grid-connected ...

Claims

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Application Information

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IPC IPC(8): H02J3/38
CPCH02J3/38
Inventor 黄辉张海龙王林赵建荣肖飞曹建博黎阳凤勇
Owner XIAN XJ POWER ELECTRONICS TECH
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