Double-mode control method for grid-connected inverter based on short-circuit ratio under weak power grid

Abstract

The invention discloses a double-mode control method for a grid-connected inverter based on a short-circuit ratio under a weak power grid. A grid-connected inverter control parameter or a grid-connected mode is adjusted by adopting a power grid impedance identification mode aiming at a multi-inverter system of a full-current source mode under a weak power grid, but due to the fact that the weak power grid characteristics tend to be directly related to the short-circuit ratio, the invention provides the double-mode control method for the grid-connected inverter based on the short-circuit ratiounder the weak power grid, so that the problem that the state of the weak power grid is not visual and clear due to the fact that the power grid impedance is adopted to represent the state of the power grid in a traditional scheme in the prior art is solved; the system equivalent short-circuit ratio detection mode adopted in the invention can accurately and intuitively reflect the state of the weak power grid, so that the basis is provided for the grid-connected inverter current source and voltage source grid-connected dual-mode switching, the stable operation of the grid-connected inverter isguaranteed, and the grid connection quality of the grid-connected inverter is greatly improved.

Description

technical field [0001] The invention relates to a control method for grid-connected multi-inverter systems, in particular to a dual-mode control method for grid-connected inverters based on the short-circuit ratio in a weak grid. Background technique [0002] With the rapid development of distributed power generation systems, grid-connected inverters are widely used. Due to the existence of long-distance transmission lines and a large number of transformer devices in remote distributed power generation systems, the grid presents a non-negligible equivalent impedance, which makes the grid present a weak grid characteristic. At this time, the multi-inverter system composed of multiple grid-connected inverters will form a dynamic interconnection system with the grid during grid-connected operation. The impedance of the grid will lead to a decrease in the grid-connected stability of the multi-inverter system, causing resonance in the output current of the grid-connected inverte...

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Problems solved by technology

[0021] In order to overcome the limitations of the above-mentioned various technical solutions, the present invention usually adopts the grid impedance identification method to adjust the grid-connected inverter control parameters or the grid-connected mode for the multi-inverter system of the full current source mode under the weak grid, but due to The characteristics of a weak grid are often directly related to the short-circuit ratio. Therefore, the present invention proposes a dual-mode control method for grid-connected inverters based on the short-circuit ratio under a weak grid to solve the problem of using grid impedance to characterize the state of a weak grid in the traditional scheme existing in the prior art. The problem of not being intuitive and clear enough, the system equivalent short-circuit ratio detection method adopted by the present invention can accurately and intuitively reflect the state of the weak power grid, and provide a basis for the current source and voltage source grid-connected dual-mode switching of the grid-connected inverter, ensuring It ensures the stable operation of the grid-connected inverter and greatly improves the grid-connected quality of the grid-connected inverter

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