Enhanced current-limiting control method aimed at drop-controlled inverter

Abstract

The invention discloses an enhanced current-limiting control method aimed at a drop-controlled inverter. A current-limiting adding method is adopted, the current limiting in the inverter is enhanced without influencing the stable state performance of the inverter, the output frequency is emergently lowered so as to adjust a virtual power angle, current saturation of the inverter is prevented, and the transient stabilization of the inverter is maintained; in addition, an amplitude limit value is set, when an output current amplitude of the inverter exceeds the amplitude limit value, the frequency of the inverter is lowered, and the virtual power angle is reduced, so that the output current of the inverter is reduced, the operation returns to a non-saturation power angle curve, and the inverter is prevented from entering a current source mode for operation and further losing stability. According to the invention, the inverter is prevented from entering the current source instability mode, the stable state operation characteristics of the system are not changed, the control method can be applied to inverters under dual-loop control such as a virtual synchronous machine, the method can also be further popularized to large interference scenes such as multi-machine passive isolated grids and isolated grid large-load switching, and the transient stabilization of the system is improved.

Description

technical field [0001] The invention relates to a control method for a droop control inverter, in particular to an enhanced current limiting control method for a droop control inverter. Background technique [0002] In recent years, renewable energy sources such as wind power and photovoltaics have developed rapidly, and large-scale wind power and photovoltaic power stations with inverters as interfaces have been established in China. Therefore, the stability of inverters is of great significance to the safe operation of power grids. [0003] Droop control makes the inverter present the characteristics of a voltage source, and is widely used in practice, especially when new energy is connected to a microgrid or a weak grid, droop control can provide voltage and frequency support for the system. Studies have shown 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. T...

AI Technical Summary

Problems solved by technology

[0005] In order to solve the problem that if the current inner loop of the three-loop control (droop control-voltage outer loop-current inner loop) inverter is saturated, the virtual power angle of the inverter is prone to instability and the stability margin will be reduced. Technical problem, the present invention proposes an enhanced current-limiting control method for drooping control inverters, which urgently reduces the inverter output frequency to adjust the virtual power angle when over-current, prevents the inverter current from being saturated, and thus keeps the inverter transient stability of

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