Segmentation control method for low-voltage ride-through of doubly-fed motor during symmetric drop of network voltage

Abstract

The invention discloses a segmentation control method for low-voltage ride-through of a doubly-fed motor during symmetric drop of network voltage. The method comprises the following steps: respectively detecting the current of a rotor and the voltage of a DC bus; comparing the instantaneous values of real-timely detected current of the rotor and voltage of the DC bus with the respective upper limit values, determining the logic control signal of a crowbar circuit according to the comparison result, outputting the logic control signal as high level if either the current of the rotor or the voltage of the DC bus exceeds the limit value, and starting up the first-stage control; and after starting crowbar protection, continuing to detect the current of the rotor and the voltage of the DC bus, comparing the values with the respective lower limit values, outputting the logic control signal as low level if the current of the rotor and the voltage of the DC bus are smaller than the respective lower limit values, stopping operation of the crowbar circuit, recovering excitation control, and conducting the second-stage control. The segmentation control method can effectively realize fault ride-through of the doubly-fed motor, and simultaneously injects demagnetization current and reactive current into a power grid to shorten the crowbar protection time.

Description

technical field [0001] The invention relates to a method for suppressing the rotor voltage and current of a doubly-fed motor wind power generation system when the grid voltage drops symmetrically, and belongs to the low-voltage ride-through technology of doubly-fed wind power generation. Background technique [0002] In recent years, doubly-fed generators have become the main model for large-scale wind farms. Their converters are 25-35% of the rated capacity and can realize four-quadrant power operation. Compared with full-power systems, the converters of doubly-fed generators are smaller in size and Light weight, less loss and low cost. However, doubly-fed motors are very sensitive to grid voltage fluctuations. If the grid voltage suddenly drops, it will lead to overvoltage and overcurrent of the rotor winding, increased operating slip, reduced electromagnetic torque, and saturation of the motor core. damage to the converter. If the doubly-fed wind turbines do not have lo...

AI Technical Summary

Problems solved by technology

If the crowbar protection time is too long, DFIG will absorb a large amount of reactive power from the system, which is not conducive to the recovery of the power grid. Therefore, the crowbar must be withdrawn in time

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