An Enhanced Droop Control Method for Improving Inverter Transient Stability

Abstract

The invention discloses an enhanced droop control method capable of improving the transient stability of an inverter. A method of introducing a non-directional axis voltage component intro droop control as the feedback quantity is adopted; the virtual power-angle characteristic of the inverter is changed; the inverter reaches balance in a current saturation transient process; voltage orientation can also be achieved when the current is saturated, so that the transient stability of the inverter is ensured; and the inverter is prevented from entering a current source mode to lose the stability. The method prevents the inverter from entering a current source instability mode; the method does not change the power sharing characteristic of droop control; and the control method can be applied to other inverters, such as a virtual synchronous machine, employing double-loop control, can also be further popularized and applied to large disturbance scenes of a multi-machine passive isolated network, high-load switching of the isolated network and the like, and improves the transient stability of a system.

Description

technical field [0001] The invention relates to a control method aimed at improving the transient stability of an inverter, in particular to an enhanced droop control method for improving the transient stability of an inverter. Background technique [0002] As a grid-connected interface between distributed power sources such as wind power and photovoltaics and energy storage equipment, the stability of the inverter is of great significance to the safe and stable operation of the grid. Droop control is widely used because it can realize power sharing between parallel inverters in microgrids, and in weak grids or microgrids, droop control inverters can provide frequency and voltage support for the grid. Research shows that due to the current limiting control inside the inverter, the inverter will fade into a current source due to the current limitation under large disturbances, which makes the transient instability process of the inverter more complicated. [0003] At present...

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Problems solved by technology

[0004] In order to solve the existing technology that contains three-loop control (droop control-voltage outer loop-current inner loop) inverter, the virtual power angle of the inverter is prone to instability and the stability margin will be reduced due to the saturation of the current inner loop. Problem, the present invention proposes an enhanced droop control method to improve the transient stability of the inverter, changing the virtual power angle characteristics of the inverter, so that the inverter has an achievable stability in the transient process of current saturation Balance point to prevent loss of transient stability after the inverter enters current source mode

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