Stability analysis method for grid-connected inverter system under coexistence condition of multiple frequency coupling factors

Abstract

The invention discloses a stability analysis method for a grid-connected inverter system under the coexistence condition of multiple frequency coupling factors. The method is applied to a grid-connected inverter system, wherein the situation that multiple frequency coupling factors coexist is considered. A frequency coupling characteristic analysis model of a grid-connected inverter is establishedin a phase sequence coordinate system, and a power grid impedance matrix is obtained through calculation under the condition that the frequency coupling is considered. The method is realized based onthe generalized Nyquist stability criterion, and the stability of the grid-connected inverter system is judged by utilizing the generalized impedance ratio matrix of the grid impedance matrix and thefrequency coupling characteristic matrix of the grid-connected inverter. Therefore, the method can be used for analyzing the system stability under the complex condition of the coexistence of multi-frequency coupling factors. Compared with an existing stability analysis method based on the impedance of the grid-connected inverter, the method is more complete. Therefore, analysis errors caused byignoring frequency coupling are avoided. The stability of the grid-connected inverter system under the complex condition can be analyzed more accurately.

Description

technical field [0001] The invention belongs to the technical field of grid-connected inverters, and in particular relates to a method for analyzing the stability of a grid-connected inverter system under the coexistence of multi-frequency coupling factors. Background technique [0002] With the large-scale access of new energy in the grid, grid-connected inverters are widely used as the energy transmission interface between new energy and the grid, such as new energy grid-connected, HVDC transmission system, flexible AC transmission system, etc. The large-scale integration of power electronic devices such as grid-connected inverters in the grid has caused new stability problems in the interconnected system, such as the subsynchronous oscillation problem that occurs between the control system of power electronic devices and the series compensation device of transmission lines. [0003] The stability analysis method based on the impedance model obtains the port impedance char...

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Problems solved by technology

[0006] However, none of the above researches on the frequency coupling characteristics of grid-connected inverters has obtained a unified grid-connected inverter that can accurately describe the coexistence of multiple frequency coupling reasons such as phase-locked loops, current controller asymmetry, and DC bus influence. The analytical model of transformer impedance cannot analyze the stability of the grid-connected inverter system under the coexistence of multi-frequency coupling factors; therefore, a more complete stability analysis method for the grid-connected inverter system is urgently needed

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