Grid-connected inverter grid impedance identification method considering grid background harmonics

Abstract

The present invention proposes a grid-connected inverter grid impedance identification method considering the background harmonics of the grid. First, the voltage of the grid-connected inverter and the current of the bridge arm side are respectively measured by using a voltage sensor and a current sensor, and the proportional-integral controller Transform the voltage and the bridge arm side current to obtain the modulated voltage signal; then, inject the high-frequency voltage signal into the modulated voltage signal and then input it into the grid-connected inverter through the control system to update the voltage of the grid-connected inverter , and use the current sensor to measure the grid-side current of the grid-connected inverter, and substitute the updated voltage and grid-side current into the voltage extraction module and current extraction module respectively; finally, use the improved complex filter to extract the grid-connected inverter The high-frequency voltage signal and high-frequency current signal of the power grid, and calculate the impedance value of the power grid. The improved complex filter in the invention considers the influence of the 5th and 7th high-frequency background harmonics of the power grid, and improves the identification accuracy of the grid impedance.

Description

technical field [0001] The invention relates to the technical field of power electronics, in particular to a grid-connected inverter grid impedance identification method considering grid background harmonics. Background technique [0002] In recent years, with the rapid expansion of the installation scale of new energy grid-connected inverters, more and more power grids have shown the characteristics of "weak grids", and their impedance is also increasing, which affects the stability of grid-connected inverters. Running has had a huge impact. For the control of grid-connected inverters in weak grids, the use of impedance-based stability criteria is an important method to study the interaction between grid-connected inverters and the grid, and this criterion needs to obtain accurate grid impedance information , therefore, it is of great significance to study the grid impedance identification method. Commonly used grid impedance identification methods mainly include passive ...

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Problems solved by technology

[0005] Aiming at the technical problem that the existing grid impedance identification methods do not consider the background harmonics of the grid, resulting in low identification accuracy of the grid impedance, the present invention proposes a grid-connected inverter grid impedance identification method that considers the grid background harmonics. The improved complex filter is used to extract the high-frequency voltage signal and high-frequency current signal from the voltage extraction module and the current extraction module respectively to obtain the impedance value of the power grid. The complex filter adopted in the present invention adds 5 times and 7 times background of the power grid Harmonic suppression module can improve the accuracy of grid impedance identification, thereby reducing the impact of grid background harmonics on grid impedance identification

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