CN-122000912-A - Higher harmonic suppression method and system

CN122000912ACN 122000912 ACN122000912 ACN 122000912ACN-122000912-A

Abstract

The invention discloses a higher harmonic suppression method and a higher harmonic suppression system, which are applied to the technical field of direct current transmission and comprise the steps of obtaining three-phase current data of an LCC converter, carrying out error analysis processing on the three-phase current data and a preset current instruction value to obtain three-phase harmonic error current data, carrying out compensation deviation processing on the obtained output current data of the MMC converter based on the three-phase harmonic error current data to obtain three-phase harmonic compensation current data, superposing a repetitive controller by a PI controller after coordinate transformation to obtain harmonic suppressed output, modulating the output to generate a control waveform of the MMC converter, and therefore achieving harmonic suppression of an SLCC circuit. The method provided by the invention realizes unified suppression of the full-higher harmonic under the working conditions of the power grids with different intensities.

Inventors

LI HUI
TIAN HUIDONG
HU YIDAN
YAO KAI
LI HOUJI
SHEN XIAOLIN
ZHAO ZHENG
WU FANGJIE
LIANG CHENGUANG
DU SHANGAN
JI YIMING
WANG YU

Assignees

国网经济技术研究院有限公司

Dates

Publication Date: 20260508
Application Date: 20260120

Claims (10)

1. A method for suppressing higher harmonics, which is applied to an SLCC direct current transmission circuit formed by LCCs and MMCs, the method comprising: Acquiring three-phase current data of an LCC converter; Performing error analysis processing on the three-phase current data and a preset current command value to obtain three-phase harmonic error current data; Based on the three-phase harmonic error current data, compensating deviation processing is carried out on the obtained output current data of the MMC converter, and three-phase harmonic compensation current data are obtained; Coordinate transformation processing is carried out on the three-phase harmonic compensation current data to obtain d-axis orthogonal component data and q-axis orthogonal component data; Based on an RPC (remote procedure control) periodical repetitive control superposition algorithm, processing the d-axis orthogonal component data and the q-axis orthogonal component data to obtain a two-phase orthogonal control output signal; And controlling the MMC to modulate the two-phase quadrature control output signal, and performing higher harmonic suppression on the SLCC direct current transmission circuit based on the obtained harmonic compensation current.
2. The method for suppressing higher harmonics as set forth in claim 1, wherein said error analysis processing said three-phase current data and a preset current command value to obtain three-phase harmonic error current data, comprises: denoising the three-phase current data based on a low-pass filtering algorithm, and performing data alignment processing on the denoising result to obtain the three-phase current data to be analyzed; Performing differential calculation on the three-phase current data to be analyzed and the preset current command value to obtain three-phase instantaneous error current data; And performing secondary noise suppression processing on the three-phase instantaneous error current data to obtain the three-phase harmonic error current data.
3. The method for suppressing higher harmonics according to claim 1, wherein said compensating deviation processing is performed on the obtained output current data of the MMC converter based on the three-phase harmonic error current data to obtain three-phase harmonic compensation current data, comprising: Performing time alignment processing on the three-phase harmonic error current data and the obtained output current data of the MMC converter to obtain aligned current data; performing deviation calculation on the aligned current data to obtain three-phase compensation deviation current data; and performing amplitude limiting treatment on the three-phase compensation deviation current data to obtain the three-phase harmonic compensation current data.
4. The method of claim 1, wherein said performing coordinate transformation on said three-phase harmonic compensation current data to obtain d-axis orthogonal component data and q-axis orthogonal component data comprises: Carrying out amplitude normalization processing on the three-phase harmonic compensation current data to obtain current data to be converted; And performing Clark conversion processing on the current data to be converted to obtain the d-axis orthogonal component data and the q-axis orthogonal component data.
5. The method of claim 1, wherein the processing the d-axis orthogonal component data and the q-axis orthogonal component data based on the RPC periodic repetitive control superposition algorithm to obtain two-phase orthogonal control output signals includes: based on the RPC periodic repetitive control superposition algorithm, proportional integral control is carried out on fundamental wave quantity in the d-axis orthogonal component data, and meanwhile periodic repetitive control is carried out on harmonic wave quantity in the d-axis orthogonal component data, so that d-axis control components are obtained; Based on the RPC periodic repetitive control superposition algorithm, performing the proportional integral control on the fundamental wave quantity in the q-axis orthogonal component data, and simultaneously performing the periodic repetitive control on the harmonic wave quantity in the q-axis orthogonal component data to obtain a q-axis control component; and performing Park transformation processing on the d-axis control component and the q-axis control component to obtain the two-phase orthogonal control output signal.
6. A higher harmonic suppression system for use in an SLCC dc transmission circuit comprising an LCC and an MMC, the system comprising: the data acquisition module is used for acquiring three-phase current data of the LCC converter; The error analysis module is used for carrying out error analysis processing on the three-phase current data and a preset current instruction value to obtain three-phase harmonic error current data; the compensation deviation module is used for carrying out compensation deviation processing on the obtained output current data of the MMC converter based on the three-phase harmonic error current data to obtain three-phase harmonic compensation current data; the coordinate transformation module is used for carrying out coordinate transformation processing on the three-phase harmonic compensation current data to obtain d-axis orthogonal component data and q-axis orthogonal component data; The signal output module is used for processing the d-axis orthogonal component data and the q-axis orthogonal component data based on an RPC (remote procedure control) periodical repeated control superposition algorithm to obtain a two-phase orthogonal control output signal; the modulation processing module is used for controlling the MMC to modulate the two-phase quadrature control output signal and carrying out higher harmonic suppression on the SLCC direct current transmission circuit based on the obtained harmonic compensation current.
7. The higher harmonic suppression system as in claim 6 wherein the error analysis module comprises: the filtering denoising unit is used for denoising the three-phase current data based on a low-pass filtering algorithm, and performing data alignment processing on the denoising result to obtain the three-phase current data to be analyzed; the differential calculation unit is used for carrying out differential calculation on the three-phase current data to be analyzed and the preset current command value to obtain three-phase instantaneous error current data; and the noise suppression unit is used for performing secondary noise suppression processing on the three-phase instantaneous error current data to obtain the three-phase harmonic error current data.
8. The higher harmonic suppression system as in claim 6 wherein the compensation deviation module comprises: the time alignment unit is used for performing time alignment processing on the three-phase harmonic error current data and the obtained output current data of the MMC converter to obtain aligned current data; The deviation calculation unit is used for performing deviation calculation on the aligned current data to obtain three-phase compensation deviation current data; And the amplitude limiting processing unit is used for carrying out amplitude limiting processing on the three-phase compensation deviation current data to obtain the three-phase harmonic compensation current data.
9. The higher harmonic suppression system as in claim 6 wherein the coordinate transformation module comprises: The normalization processing unit is used for carrying out amplitude normalization processing on the three-phase harmonic compensation current data to obtain current data to be converted; And the Clark conversion processing unit is used for performing Clark conversion processing on the current data to be converted to obtain the d-axis orthogonal component data and the q-axis orthogonal component data.
10. The higher harmonic suppression system as in claim 6 wherein the signal output module comprises: the d-axis control component unit is used for performing proportional integral control on fundamental wave quantity in the d-axis orthogonal component data based on the RPC periodic repetitive control superposition algorithm, and performing periodic repetitive control on harmonic wave quantity in the d-axis orthogonal component data to obtain a d-axis control component; A q-axis control component unit configured to perform the proportional integral control on the fundamental wave amount in the q-axis orthogonal component data based on the RPC periodic repetitive control superposition algorithm, and perform the periodic repetitive control on the harmonic wave amount in the q-axis orthogonal component data at the same time, to obtain a q-axis control component; And the Park conversion processing unit is used for carrying out Park conversion processing on the d-axis control component and the q-axis control component to obtain the two-phase orthogonal control output signal.

Description

Higher harmonic suppression method and system Technical Field The invention relates to the technical field of direct current transmission, in particular to a method and a system for restraining higher harmonic waves. Background In a high-voltage direct current transmission system, a power grid commutation converter is widely applied due to the simple structure, low cost and high capacity transmission capability. However, the commutation converter inevitably generates a large amount of higher harmonic current on the ac side in the commutation process, and if the higher harmonic current is not effectively suppressed, the voltage distortion of the whole power grid, overheat of equipment or relay protection misoperation will be caused, the electric energy quality and operation safety of the power system are seriously threatened, so that the higher harmonic wave must be suppressed. In the prior art, a passive higher harmonic suppression method relying on a passive filter is mainly adopted, and the principle is that the characteristic that LC series resonance presents an extremely low impedance path at specific harmonic frequency is utilized, so that harmonic current with specific frequency preferentially flows through the filter to form local circulation, thereby greatly reducing harmonic components injected into an alternating current power grid and achieving the purpose of suppression. Meanwhile, under the condition of weak current network, the equivalent impedance of the power network is large and strong, and the power network and a capacitive element of the filter easily form a high Q value parallel resonant circuit, so that harmonic current is amplified, and the voltage stability and the operation safety of a system are seriously threatened. Disclosure of Invention The invention provides a method and a system for suppressing higher harmonics, which aim to solve the technical problem that the passive harmonic suppression method cannot uniformly suppress the full harmonics, so as to realize the effect of uniformly suppressing the full harmonics. In order to solve the technical problem, an aspect of the present invention provides a method for suppressing higher harmonics, which is applied to an SLCC direct current transmission circuit formed by LCC and MMC, and the method includes: Acquiring three-phase current data of an LCC converter; Performing error analysis processing on the three-phase current data and a preset current command value to obtain three-phase harmonic error current data; Based on the three-phase harmonic error current data, compensating deviation processing is carried out on the obtained output current data of the MMC converter, and three-phase harmonic compensation current data are obtained; Coordinate transformation processing is carried out on the three-phase harmonic compensation current data to obtain d-axis orthogonal component data and q-axis orthogonal component data; Based on an RPC (remote procedure control) periodical repetitive control superposition algorithm, processing the d-axis orthogonal component data and the q-axis orthogonal component data to obtain a two-phase orthogonal control output signal; And controlling the MMC to modulate the two-phase quadrature control output signal, and performing higher harmonic suppression on the SLCC direct current transmission circuit based on the obtained harmonic compensation current. As one preferable solution, the performing error analysis processing on the three-phase current data and a preset current command value to obtain three-phase harmonic error current data includes: denoising the three-phase current data based on a low-pass filtering algorithm, and performing data alignment processing on the denoising result to obtain the three-phase current data to be analyzed; Performing differential calculation on the three-phase current data to be analyzed and the preset current command value to obtain three-phase instantaneous error current data; And performing secondary noise suppression processing on the three-phase instantaneous error current data to obtain the three-phase harmonic error current data. As one preferable solution, the compensating deviation processing is performed on the obtained output current data of the MMC converter based on the three-phase harmonic error current data to obtain three-phase harmonic compensating current data, including: Performing time alignment processing on the three-phase harmonic error current data and the obtained output current data of the MMC converter to obtain aligned current data; performing deviation calculation on the aligned current data to obtain three-phase compensation deviation current data; and performing amplitude limiting treatment on the three-phase compensation deviation current data to obtain the three-phase harmonic compensation current data. As one preferable mode, the coordinate transformation processing is performed on the three-phase harmonic compensation current data to obta