CN-121984002-A - Harmonic suppression method and system under high background harmonic condition

CN121984002ACN 121984002 ACN121984002 ACN 121984002ACN-121984002-A

Abstract

The invention discloses a harmonic suppression method and a system under a high background harmonic condition, wherein the method comprises the steps of carrying out wavelet transformation on an input power grid voltage signal, extracting amplitude information of each subharmonic in real time, dynamically determining a target harmonic set to be suppressed currently through a preset threshold judgment mechanism according to the extracted amplitude information of each subharmonic, synchronously executing harmonic suppression and phase compensation operation on each subharmonic in the target harmonic set, and sending a signal subjected to harmonic suppression and phase compensation to a phase-locked loop to obtain a power grid synchronous phase.

Inventors

WANG JIANGJIAN
DING LI
LI SHUCHUN
CHEN JUNMEI
WANG PAN
LIU MIN
WANG BIN
ZHANG HUIPING
HE LEZHANG
JIANG TAO
CHEN HUANRONG
GONG JIAN
LI YU
ZHANG CHI

Assignees

鹰潭欣欣电力实业有限公司

Dates

Publication Date: 20260505
Application Date: 20260127

Claims (10)

1. The harmonic suppression method under the high background harmonic condition is characterized by comprising the following steps of: s1, carrying out wavelet transformation on an input power grid voltage signal, and extracting amplitude information of each subharmonic in real time; s2, dynamically determining a target harmonic set to be suppressed currently through a preset threshold judging mechanism according to the extracted amplitude information of each subharmonic; S3, synchronously implementing harmonic suppression and phase compensation operation for each harmonic wave contained in the determined target harmonic wave set; and S4, sending the signal subjected to harmonic suppression and phase compensation operation into a phase-locked loop to acquire grid synchronous phase information.
2. The method for suppressing harmonics under high background harmonic conditions according to claim 1, wherein the step S1 specifically includes performing multi-scale decomposition and reconstruction on a power grid voltage signal by using a discrete wavelet transform, and the expression of the discrete wavelet transform is: , , In the formula, As a result of the discrete wavelet coefficients, As the original signal is meant to be a signal, As a result of the discrete wavelet coefficients, In order to decompose the number of layers, In order to be able to carry out the parameters of the translation, Is a small fundamental coefficient.
3. The method for suppressing harmonics under the condition of high background harmonics according to claim 1, wherein the specific operation process of S2 is that a time-frequency matrix is constructed by using a time-frequency joint analysis method to analyze the time domain mutation and the frequency domain distribution of the harmonics, and the expression of the time-frequency matrix is as follows: , In the formula, In the form of a time-frequency matrix, As the original signal is meant to be a signal, Controlling the expansion and contraction of the wavelet function for the scale factors, inversely proportional to the frequency, As a time-shift factor, As a parent wavelet function.
4. The method for harmonic suppression under high background harmonic conditions according to claim 1, wherein the harmonic suppression in S3 uses a preconfigured proportional resonant controller to generate a corresponding harmonic suppression signal; The phase compensation adopts a phase lead compensator to compensate phase lag introduced by the proportional resonance controller and the signal processing link in the whole control link.
5. The method of harmonic suppression under high background harmonic conditions according to claim 4, wherein the proportional resonant controller is a quasi-proportional resonant controller for angular frequencies Is the first of (2) The transfer function of the subharmonic is expressed as: , In the formula, For a quasi-proportional resonant controller transfer function for the h-th harmonic, Is a gain factor of a proportion of the gain, For the resonant gain coefficient, s is the complex frequency domain variable, For the bandwidth of the resonance band, The angular frequency of the nth harmonic is H, and the harmonic frequency is set to be suppressed.
6. The method for harmonic suppression under high background harmonic conditions according to claim 4, the phase lead compensator is a fractional delay compensator.
7. The method for harmonic suppression under high background harmonic conditions according to claim 1, wherein in S4, the phase-locked loop is a synchronous reference frame phase-locked loop, a proportional-integral controller is adopted for a loop filter of the synchronous reference frame phase-locked loop, and an open loop transfer function of the phase-locked loop has an expression as follows: , , , In the formula, As a function of the transfer of the phase-locked loop, Is a gain factor of a proportion of the gain, As a result of the resonant gain factor, As a variable in the complex frequency domain, In order to achieve a damping ratio, Is a natural frequency.
8. A method for harmonic suppression under high background harmonic conditions according to claim 3, wherein the time-frequency joint analysis method specifically comprises the following steps: S31, identifying harmonic time-varying characteristics in energy concentration according to the mode maximum value obtained by the time-frequency matrix and the distribution of the mode maximum value on a time-frequency plane; s32, dynamically determining a target harmonic set to be suppressed currently by adopting a positive feedback self-adaptive double-threshold adjustment mechanism according to the identified harmonic time-varying characteristics; S33, the positive feedback self-adaptive double-threshold adjustment mechanism is that a first threshold a t and a second threshold b t are preset, and the second threshold b t is larger than the first threshold a t ; S34, when the amplitude of a certain harmonic is smaller than a first threshold a t , not incorporating the certain harmonic into a target harmonic set; And S35, when the amplitude of a certain harmonic is not less than a t , continuously judging whether the amplitude of the certain harmonic is less than a second threshold b t , and when the amplitude of the certain harmonic is greater than or equal to a second threshold b t , judging that the certain harmonic is a 'significant disturbance source', and if the amplitude of the certain harmonic is not less than the second threshold b t , incorporating the certain harmonic into a target harmonic set, otherwise, not incorporating the certain harmonic into the target harmonic set.
9. A harmonic suppression system under high background harmonic conditions, comprising: the extraction module is configured to perform wavelet transformation on an input power grid voltage signal and extract amplitude information of each subharmonic in real time; The determining module is configured to dynamically determine a target harmonic set to be suppressed currently according to the amplitude information of each subharmonic through a preset threshold judging mechanism; a compensation module configured to synchronously perform harmonic suppression and phase compensation operations for each harmonic in the target harmonic set, the compensation module being configured to input a proportional resonance controller configured for each harmonic to generate a suppression signal, and to compensate for phase lag generated by the proportional resonance controller and a signal processing link using a phase lead compensator; and the suppression module is configured to send the signals subjected to harmonic suppression and phase compensation into a phase-locked loop so as to acquire the grid synchronous phase.
10. The method according to claim 9, wherein the extraction module performs discrete wavelet transformation on the grid voltage signal in each fundamental wave period, and calculates the characteristic amplitude of the harmonic component in real time by reconstructing wavelet coefficients of corresponding frequency bands of each subharmonic, and wherein a sliding data buffer is provided in the extraction module, the length of which is configured to cover at least 4 consecutive fundamental wave periods, and the amplitude update operation is triggered once each sampling data point is received.

Description

Harmonic suppression method and system under high background harmonic condition Technical Field The invention belongs to the technical field of harmonic suppression, and particularly relates to a harmonic suppression method and system under a high background harmonic condition. Background Along with large-scale access of new energy sources such as distributed photovoltaic, wind power and the like and operation of a large number of nonlinear loads, harmonic problems are long-term important factors affecting system stability, equipment safe operation and energy utilization efficiency in the fields of power systems and electric energy quality management. With the widespread use of nonlinear loads (such as frequency converters, rectifying devices, switching power supplies, etc.), the harmonic content in the power grid increases significantly, and particularly in industrial intensive areas or high-density electric field scenes, the typical characteristics of "high background harmonics" are presented. The high background harmonic wave refers to a harmonic component with higher amplitude and complex components existing in the bus voltage or current before the power grid is connected to a specific load or a compensation device, and usually, lower harmonics such as 5 th order, 7 th order, 11 th order, 13 th order and the like are mainly used, and inter-harmonic waves and higher harmonics may also be included. The traditional synchronous reference frame phase-locked loop (SRF-PLL) has good performance under ideal power grid conditions, but the phase-locked precision of the traditional synchronous reference frame phase-locked loop is obviously reduced under harmonic environment, and the dynamic response is slowed down, so that grid-connected current distortion is caused, and even system oscillation is caused. In order to suppress the interference of specific subharmonics to the phase-locked loop, a scheme of parallel connection of multi-proportion resonant controllers is often adopted in the prior art. However, such a solution has the following significant drawbacks: Firstly, a mode of fixedly inputting all resonant controllers is generally adopted, when the harmonic amplitude is low or the subharmonic is not generated, the controller resource waste is caused, and unnecessary phase lag is possibly introduced to influence the dynamic performance; Secondly, the traditional method lacks fine perception of harmonic time-varying characteristics, and cannot dynamically adjust a suppression strategy according to real-time change of harmonic energy, so that response is slow or excessively adjusted when harmonic is suddenly increased or suddenly changed; Thirdly, the resonance controller and the signal detection link itself may introduce phase lag, and if compensation is not applied, the suppression effect at the target frequency may be affected. Therefore, a high-performance harmonic suppression method capable of sensing the harmonic state of the power grid in real time, intelligently deciding the suppression target and accurately compensating the phase of the control loop is needed, so that the adaptability and the operation quality of the grid-connected equipment in a complex power grid environment are improved. Disclosure of Invention The invention provides a harmonic suppression method and a harmonic suppression system under a high background harmonic condition, which solve the problems of the prior art that the phase locking precision is reduced, the controller is frequently switched and the suppression effect is poor. In order to solve the technical problems, the invention provides a harmonic suppression method under a high background harmonic condition, which comprises the following steps: s1, carrying out wavelet transformation on an input power grid voltage signal, and extracting amplitude information of each subharmonic in real time; s2, dynamically determining a target harmonic set to be suppressed currently through a preset threshold judging mechanism according to the extracted amplitude information of each subharmonic; S3, synchronously implementing harmonic suppression and phase compensation operation for each harmonic wave contained in the determined target harmonic wave set; and S4, sending the signal subjected to harmonic suppression and phase compensation operation into a phase-locked loop to acquire grid synchronous phase information. Preferably, the S1 specifically comprises the steps of carrying out multi-scale decomposition and reconstruction on a power grid voltage signal by adopting discrete wavelet transformation, wherein the expression of the discrete wavelet transformation is as follows: , , In the formula, As a result of the discrete wavelet coefficients,As the original signal is meant to be a signal,For discrete wavelet coefficients, J is the number of decomposition layers, k is the translation parameter,Is a small fundamental coefficient. Preferably, the specific operation process of S2 is that a