An Inverter-Based Grid Impedance Online Detection Method

Abstract

The present invention relates to a power grid impedance on-line detection method on the basis of an inverter. The power grid impedance on-line detection method on the basis of the inverter comprises the following steps: (1) the amplitude of an output voltage of a voltage inverter is regulated through adoption of an axle voltage regulation method after the synchronous grid connection of the inverter, an output frequency of the voltage inverter is regulated to accord with the frequency of the power grid, and voltage values, VPCC1 and VPCC2, of a PPC point in two states are acquired; and (2) a power grid impedance value is calculated. Compared with the prior art, the power grid impedance on-line detection method on the basis of an inverter is easy to operate, is high in measurement accuracy, and has small influence on quality of electric energy, etc.

Description

technical field [0001] The invention relates to an online detection method for grid impedance, in particular to an inverter-based online detection method for grid impedance. Background technique [0002] In a distributed power generation system, the performance of the grid-connected inverter is closely related to the grid impedance. When the grid impedance is high, the grid-connected power generation system will become unstable, especially in the case of a weak grid. Moreover, grid impedance changes with time and changes in grid operating status, so accurate grid impedance online measurement is a key technology to achieve high-performance adaptive control of grid-connected inverters in weak grid situations. In addition, the grid impedance Measurement and analysis can also quickly detect faults in the grid. Some feasible methods have been proposed in the existing literature. The current grid impedance measurement methods mainly include active measurement methods and passive ...

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Problems solved by technology

[0004] 2. Grid impedance changes with time and grid operating status;

[0005] 3. Most of the traditional measurement methods are offline measurement or require additional hardware circuits;

[0006] 4. The active measurement methods of grid impedance, such as power disturbance, injection of harmonics, etc., have high measurement accuracy, but need to add disturbance, and the characteristics of large-scale grid connection need further research;

[0007] 5. The passive measurement method of grid impedance will have the problem of large amount of calculation and low measurement accuracy

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