Voltage sag treatment control method and system for frequency converter

The invention belongs to the technical field of power systems, and particularly relates to a voltage sag governance control method and system for a frequency converter, and the method comprises the steps: obtaining the voltage and current of an AC side of the frequency converter; calculating the voltage and the positive sequence impedance of the power grid side according to the obtained voltage and current; judging whether voltage sag occurs on the power grid side according to the obtained power grid side voltage; when the voltage sag occurs at the power grid side, judging the occurrence position of the voltage sag according to the obtained change of the positive sequence impedance at the power grid side; when the obtained positive sequence impedance at the power grid side changes, the voltage sag occurs at the power grid side, and voltage sag treatment is started; and when the obtained positive sequence impedance at the power grid side is not changed, the voltage sag occurs at the load side, and the voltage