Common mode voltage suppression method for wind power generation system

Abstract

The invention relates to a common-mode voltage suppression method for a wind power generation system. A stator winding of a generator is connected to a grid by a transformer; a rotor winding uses a machine-side converter (MSC) to transform alternating-current power with the changing frequency into direct-current power; and then the direct-current power is converted into alternating-current power with a fixed frequency by a grid-side converter (GSC) and the alternating-current power is connected to the grid by the transformer. The current of a motor rotor is adjusted by controlling a power converter; and the motor is able to output power with the constant frequency on the condition of rotating speed changing of the motor. In MSC and GSC controlling, two PWM modules select voltage space vectors based on a given voltage and generate a power switch signal of a converter; and on the basis of the existing converter PWM module, the voltage space vector modulation of the MSC and GS are considered comprehensively and a zero-voltage vector is selected in a coordinating manner to carry out modulation, so that the common-mode voltage of the system is reduced effectively. The method is simple and effective and is easy to implement and has high economy and practicability.

Description

technical field [0001] The invention relates to a motor control technology, in particular to a method for suppressing common-mode voltage of a wind power generation system. Background technique [0002] Megawatt wind turbines and converter systems, due to the use of voltage pulse width modulation (PWM), the common mode voltage of the system is high, causing excessive shaft current, which is likely to cause electrical corrosion damage to the bearing; if the common mode voltage is too high, it will also Cause damage to the motor winding insulation, affecting the life and failure rate of the motor winding insulation. Excessive common-mode voltage may also cause electrical system electromagnetic interference (EMI) and electromagnetic compatibility (EMC) problems; if a large amount of zero-sequence current flows, it will also cause unnecessary system zero-sequence current loss. Contents of the invention [0003] The present invention aims at the problem that the common mode vo...

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Problems solved by technology

[0003] The present invention aims at the problem that the common mode voltage of the system is high due to the voltage pulse width modulation of the megawatt wind power generator, and proposes a method for suppressing the common mode voltage of the wind power generation system. By changing the control method, the megawatt wind power generator and The common mode voltage of the converter system, thereby greatly reducing the occurrence of electrical corrosion of generator bearings, prolonging the insulation life of motor windings, reducing the harm of electromagnetic interference in the system, and meeting the requirements of electromagnetic compatibility standards

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