Dual-mode control method of grid-connected inverter based on short-circuit ratio in weak grid

Abstract

The invention discloses a dual-mode control method of a grid-connected inverter based on a short-circuit ratio under a weak grid. The present invention is aimed at multi-inverter systems with full current source mode under weak grids, and usually uses grid impedance identification to adjust grid-connected inverter control parameters or grid-connected modes. However, since weak grid characteristics are often directly related to short-circuit ratios, therefore The present invention proposes a dual-mode control method for grid-connected inverters based on short-circuit ratio under weak power grids, in order to solve the problem that using grid impedance to represent the state of weak grids is not intuitive and clear enough in the traditional schemes existing in the prior art. The system equivalent short-circuit ratio detection method can accurately and intuitively reflect the state of the weak grid, and provide a basis for the current source and voltage source grid-connected dual-mode switching of the grid-connected inverter, ensuring the stable operation of the grid-connected inverter, greatly Improved the grid-connected quality of the grid-connected inverter.

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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