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Harmonic current compensating method based on fast Fourier transform

A technology of Fourier transform and harmonic current, which is applied to harmonic reduction devices and AC networks to reduce harmonics/ripples, etc., and can solve the effects of increased delay, reduced control loop bandwidth, and harmonic current compensation accuracy and other problems, to achieve the effect of fast response, wide application range, and clear control objectives

Active Publication Date: 2014-03-12
CHINA ELECTRIC POWER RES INST +1
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Problems solved by technology

However, adding a notch filter in the current control loop will reduce the bandwidth of the control loop and increase the delay, which will affect the accuracy of harmonic current compensation

Method used

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  • Harmonic current compensating method based on fast Fourier transform
  • Harmonic current compensating method based on fast Fourier transform
  • Harmonic current compensating method based on fast Fourier transform

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Embodiment Construction

[0037] The control method of the present invention will be further described in detail below in conjunction with the accompanying drawings.

[0038] The system voltage, load current, and chain converter output current in the content are all obtained by the measurement link. When the electrical quantity signal is used to achieve the control target, it has been filtered and reduced.

[0039] In order to explain the working principle of the harmonic current compensation algorithm based on the fast Fourier transform of the present invention more clearly, it is now combined with the analysis and description of the cascaded H-bridge type STATCOM control algorithm. The STATCOM structure is as attached figure 1 Shown. Each phase consists of N cascaded single-phase inverters with independent DC capacitors in series, and the three-phase converter chain adopts star connection. Figure u sA , U sB , U sC Is the AC voltage of the system, i fa , I fb , I fc Respectively is the output curre...

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Abstract

The invention provides a harmonic current compensating method based on fast Fourier transform. For an occasion that double-sequence current decoupling control is adopted for chain static synchronous compensator (STATCOM) inner loop circuit control, and harmonic current compensating precision is ensured by correcting a harmonic current instruction under the condition that inner loop control bandwidth is relatively low. The compensating method comprises the following steps of: firstly, respectively performing fast Fourier transform (FFT) analysis on load current and current converter output current; secondly, calculating the errors of a load current amplitude value, a current converter output current amplitude value, a load current phase and a current converter output current phase, and respectively correcting a harmonic current amplitude value and a phase instruction according to the errors; and finally, reconstructing the corrected amplitude values / phases to obtain the harmonic current instruction of a chain current converter. The influence of the bandwidth and delay of a controller on the harmonic current compensating precision is considered to keep the errors of the output current and the load harmonic current within hysteresis width, the harmonic current compensating precision is improved, and the practical engineering value is relatively high.

Description

Technical field [0001] The invention belongs to the technical field of power electronic device control, and specifically relates to a harmonic current compensation method based on Fast Fourier Transform (Fast Fourier Transform). Background technique [0002] Chain converters are widely used in engineering. They are composed of multiple single-phase converter chains, and each single-phase converter chain consists of at least one single-phase chain link (ie figure 1 The cascade modules 1, 2...n) are composed of cascade modules, and the chain links can be connected in series or in parallel. Each chain link includes an H-bridge voltage source converter. [0003] The chain converter has many advantages, which can realize independent phase separation control, which is helpful to solve the problem of system phase balance. The basic unit structure of all links is exactly the same, which can realize modular design, facilitate expansion and maintenance, and avoid the problems caused by the d...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02J3/01
CPCY02E40/40
Inventor 田鑫周飞蔡林海宗波蒋晓春赵国亮荆平
Owner CHINA ELECTRIC POWER RES INST
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