Direct-drive permanent magnet fan harmonic wave suppression optimizing method in asymmetric fault of power grid voltage

Abstract

The invention discloses direct-drive permanent magnet fan harmonic wave suppression optimizing method in an asymmetric fault of power grid voltage. The method comprises the steps of acquiring abc three-phase static voltage according to abc three-phase current at the motor side; extracting harmonic current by 5-7 times according to the abc three-phase current at the motor side, performing harmonic current suppression, and acquiring abc three-phase compensation voltage; adding the abc three-phase static voltage and the abc three-phase compensation voltage for obtaining a control signal; performing SVPWM modulation on the control signal for obtaining a PWM wave, and controlling an inverter switch of the direct-driven permanent magnet fan through the PWM wave, thereby driving a permanent magnet synchronous generator (PMSG) of the drive-drive permanent magnet fan. According to the method of the invention, through acquiring the abc three-phase compensation voltage after extracting the harmonic current by 5-7 times and performing harmonic current suppression, the abc three-phase static voltage is compensated for generating a control signal, and a harmonic wave component in the motor current on the condition of asymmetric fault can be compensated, thereby greatly reducing influence of DC bus voltage to a motor-side current transformer, improving waveform of the motor current and performing a relatively high harmonic wave suppression effect.

Description

technical field [0001] The invention relates to the direct-drive permanent-magnet fan technology for wind power generation, in particular to a harmonic suppression optimization method for the direct-drive permanent-magnet fan under a grid voltage asymmetry fault. Background technique [0002] With the increase of the capacity of the direct-drive permanent magnet fan, the impact of high-order harmonics generated by asymmetrical faults on the power grid and other factors on the power grid is becoming more and more serious, and a small unbalanced voltage will cause a high degree of grid-side current. The balance and distortion will lead to the oscillation of the bus voltage on the DC side, which will indirectly affect the control of the machine-side converter, causing the electromagnetic torque of the permanent magnet synchronous motor to pulsate, which will cause the output power of the entire generator set to oscillate. [0003] The disadvantages of the existing direct drive ...

AI Technical Summary

Problems solved by technology

[0002] With the increase of the capacity of the direct-drive permanent magnet fan, the impact of high-order harmonics generated by asymmetrical faults on the power grid and other factors on the power grid is becoming more and more serious, and a small unbalanced voltage will cause a high degree of grid-side current. balance and distortion, which in turn leads to the oscillation of the bus voltage on the DC side, which indirectly affects the control of the machine-side converter, causing the electromagnetic torque of the permanent magnet synchronous motor to pulsate, thus causing the output power of the entire generator set to oscillate.

[0003] The disadvantages of the existing direct drive permanent magnet wind turbine harmonic suppression control strategy under asymmetrical faults are as follows: (1) When an asymmetrical fault occurs, the grid current is decomposed into positive and negative sequences, and the two synchronous The current control in the coordinate system can eliminate the DC bus voltage fluctuation under asymmetrical faults, but due to the decomposition of the positive and negative sequences, it will cause delay and error in the current loop, reduce the system response speed, complex structure, and online calculation Big

(2) When an asymmetric fault occurs, the direct-drive wind power system will generate a large number of harmonics. These harmonics will affect the power generation efficiency and heat generation of the motor in the slightest, and cause damage to the motor in severe cases. There are many factors that generate harmonics, and the harmonics The content varies with the working point of the motor. The traditional single compensation method based on harmonic generation factors is more complicated, and the effect of harmonic current suppression is not ideal.

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