Doubly-fed motor three-phase short-circuit current practical calculation method

Abstract

The present invention discloses a doubly-fed motor three-phase short-circuit current practical calculation method which comprises the steps of establishing a transient equivalent module of a doubly-fed wind generator, and calculating stator side equivalent reactance after short circuit; calculating a stator side flux linkage initial value and a rotor side flux linkage initial value before short circuit; calculating transient stator side flux linkage and transient rotor side flux linkage; calculating stator side current; performing coordinate transformation on the stator side current i-arrow<s>, and obtaining short-circuit current, short-circuit current instantaneous maximum values and periodic component virtual values of the A-phase, B-phase and C-phase; calculating element parameters: Rs, Rr, Ls[sigma], Lr[sigma] and RCB of the equivalent model by utilization of the engineering practical parameter locked-rotor current percent; and obtaining the short-circuit current instantaneous maximum values and the periodic component virtual values of the A-phase, B-phase and C-phase for practical calculation. The short-circuit current is calculated by using the engineering practical parameters, the calculating result is more accurate, and therefore parameters of a Crowbar circuit can be accurately determined, and safety of a doubly-fed motor can be improved.

Description

technical field [0001] The invention relates to a practical calculation method for the three-phase short-circuit current of a doubly-fed motor based on Crowbar protection, and belongs to the technical field of electrical safety analysis of wind farms. Background technique [0002] As the proportion of wind power installed capacity in the power grid increases, the impact of wind farm operation on the stability of the power grid cannot be ignored. The variable speed constant frequency doubly-fed induction wind generator (DFIG) has many superior characteristics, which make it widely used in wind power generation. [0003] DFIG has great defects in the ability to deal with grid faults. When a short-circuit fault occurs in the grid, the stator current of the generator will increase. Due to the strong coupling relationship between the generator rotor and the stator, the rapidly increasing stator current will cause the rotor current to sharply increase. If it rises, it is easy to ...

AI Technical Summary

Problems solved by technology

[0004] According to the short-circuit current, the parameters of the Crowbar circuit are set to protect other equipment in the circuit. In the existing short-circuit current analysis, such as the Chinese invention patent CN201510750713.4 discloses a method for calculating the three-phase short-circuit current of double-fed motors, using pure theory The calculation method to calculate the maximum value and effective value of short-circuit current is not applicable in engineering, and there is a large error between the obtained analytical results and the actual short-circuit fault; in engineering, national standards are usually used to calculate, and short-circuit faults are calculated according to national standards The calculation results are not accurate enough for the maximum value and effective value of the current, and the parameter setting of the Crowbar circuit is not accurate enough accordingly.

Images