Method for restraining total output reactive power fluctuation of double-fed wind power system under unbalanced and harmonic distortion network voltage

Abstract

The invention discloses a method for restraining total output reactive power fluctuation of a double-fed wind power system through a series-connection network side converter under an unbalanced and harmonic distortion network voltage and relates to the field of control over series connection network side converters, parallel connection network side converters and motor side converters. A voltage controller adopted for the series connection network side converter is used for rapidly restraining stator negative-sequence harmonic voltage components, five-time harmonic voltage components and seven-time harmonic voltage components and safe and stable operation of an electric generator is guaranteed. A reference current order of a parallel connection network side converter comprises fundamental harmonic positive-sequence current components, fundamental harmonic negative-sequence current components, five-time harmonic current components and seven-time harmonic components under a forward-direction synchronous revolution coordinate system. A current controller adopted for the parallel connection network side converter can simultaneously, accurately and rapidly adjust direct components, second harmonic generation alternating components and sixth harmonic generation alternating components. Total output reactive power second harmonic generation fluctuation and sixth harmonic generation fluctuation of the system can be restrained and the quality of electric energy of a power grid connected to the double-fed sensing wind power system is effectively improved under the unbalanced and harmonic distortion network voltage.

Description

technical field [0001] The present invention relates to technical improvement of doubly-fed induction wind power generation system using series grid-side converter, in particular to suppression of total output reactive power fluctuation of doubly-fed induction wind power system using series grid-side converter under unbalanced and harmonically distorted grid voltage The method belongs to the technical field of electric power control. Background technique [0002] With the widespread application of power electronic devices such as grid-connected inverters and static var compensators, the coexistence of grid voltage imbalance and harmonic distortion is more likely to occur in transmission lines and distributed grids. The unbalanced and harmonic distortion of the grid voltage will lead to unbalanced and distorted DFIG stator voltage, which in turn will cause unbalanced and distorted stator and rotor currents and system output current. The fluctuation of generator output power,...

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Problems solved by technology

Due to the limitation of the rotor current control variable, the method cannot simultaneously achieve stator and rotor current balance without distortion or generator output power fluctuations, so the unbalanced heating of the stator and rotor windings and harmonic loss or stator power fluctuations still exist in DFIG

[0006] Document (2) proposes to use the proportional-integral-dual-frequency resonance controller under the forward synchronous rotating shaft system to coordinate the control of the rotor-side converter and the grid-side converter, so as to suppress the fluctuation of the electromagnetic torque and the total output active power of the system , under the control strategy, the stator and rotor currents are unbalanced and harmonically distorted at the same time, so the extra heat of the stator and rotor windings still exists, which will affect the life of the winding insulation materials

[0007] In addition, due to the existence of grid-side converters, the above-mentioned documents cannot guarantee that the total output reactive power of the system will not fluctuate while achieving their respective control objectives.

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