Adaptive three-phase grid-connected converter phase-locked loop and phase-locking control method thereof

Abstract

The invention relates to the technical field of electrical engineering, and provides an adaptive three-phase grid-connected converter phase-locked loop and a phase-locking control method thereof. Thephase-locked loop of the invention comprises a coordinate transformation unit, a delay signal offset module, a second-order generalized integrator, and a PI regulator. A grid voltage signal is input into the coordinate transformation unit. The output component of the coordinate transformation unit is input into the delay signal offset module. The output component of the delay signal offset moduleis connected in series with the second-order generalized integrator. A q-axis voltage component obtained by acquiring the difference between the output component of the delay signal offset module andthe output component of the second-order generalized integrator is connected in series to the PI regulator. The sum of the frequency difference output by the PI regulator and the rated angular frequency of the grid voltage is subjected to an integration link such that the phase angle of the grid voltage signal is obtained. The phase angle of the grid voltage signal is fed back to the coordinate transformation unit. The method can dynamically detect the grid voltage phase at high accuracy in the event of complex conditions, especially asymmetric grid faults and introduced harmonic components.

Description

technical field [0001] The invention relates to the technical field of electrical engineering, in particular to an adaptive three-phase grid-connected converter phase-locked loop and a phase-locked control method thereof. Background technique [0002] New energy (photovoltaic, wind energy) grid-connected power generation control requires synchronous detection of grid phase information. At the same time, the grid-connected inverter is also required to have a certain low-voltage ride-through capability during grid faults, that is, the inverter must emit corresponding reactive power to support the recovery of the grid voltage according to the depth of the grid voltage drop. It is necessary to accurately extract the grid phase, amplitude and frequency under normal grid-connected operation and fault conditions. At present, a variety of phase-locked loops are applied to grid voltage phase detection. [0003] Among the existing phase-locked loops, the most common one is the hardw...

AI Technical Summary

Problems solved by technology

The hardware phase-locked loop locks the phase information of the power grid through hardware devices. During the phase detection process, there are multiple zero-crossings, which will cause phase-locking failure.

In addition, the software phase-locked loop based on the synchronous coordinate system uses coordinate transformation to transform the abc three-phase voltage into the two-phase dq coordinate system, and controls the voltage of the d-axis or q-axis to be zero to achieve phase-locking, while the software phase-locked loop based on the synchronous coordinate system The phase-locked loop cannot lock the phase accurately when the grid voltage is asymmetrical and the harmonic components are mixed

Although the phase-locked loop based on the digital notch filter can eliminate the influence of harmonics, the parameter setting of the notch filter is relatively complicated, and the calculation amount of the system is too large, and the response speed is slow

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