A modeling method for analyzing the interaction effect of harmonics between photovoltaic power stations and distribution networks

Abstract

The invention discloses a modeling method for analyzing harmonic interaction between a photovoltaic power station and a distribution network, and relates to the technical field of harmonic interaction. The method first provides a multi-faceted data basis for subsequent analysis by collecting data information of relevant equipment, relevant signal data information, and relevant harmonic data information of power transformers in photovoltaic power stations and distribution networks in various aspects; at the same time, Fourier transform technology is used to convert time domain signals into frequency domain signals; then, harmonic analysis technology is used to extract relevant harmonic data information and features of power transformers in photovoltaic power stations and distribution networks, and a set of analysis models is established to further evaluate the degree and influencing factors of harmonic interaction between photovoltaic power stations and distribution networks; by calculating and analyzing the resonant frequency Xppl of the power transformer, it is possible to timely discover whether the power transformer will be affected by resonance, and provide early warning notifications through grade early warning reports, so as to effectively prevent potential harm caused by harmonic interaction to the stable operation of the power system.

Description

Technical Field

[0001] The present invention relates to the technical field of harmonic interaction, and in particular to a modeling method for analyzing harmonic interaction effects between a photovoltaic power station and a distribution network. Background Art

[0002] In the modern energy field, photovoltaic power stations are an important part of clean energy generation, and the interaction between them and the distribution network has become a key issue in power system optimization. In particular, when photovoltaic power stations interact with the distribution network and the superposition effect of harmonics occurs, it has an unignorable impact on the stability and reliability of the power system.

[0003] In the interaction between traditional photovoltaic power stations and distribution networks, lower frequency harmonics are generated, which will not have a significant impact on the resonant frequency of the power transformer. Therefore, in the design and operation of the power system, the harmonic frequency impact of the power transformer is usually negligible. However, the harmonics generated by photovoltaic power stations have the characteristics of high frequency and wide frequency domain. The harmonic frequency range is wide and contains relatively high frequency components. These high-frequency and wide-frequency harmonic signals are prone to resonate with the resonant frequency of the power transformer, causing the occurrence of resonance effect, increasing the magnetization and iron loss of the power transformer, resulting in a decrease in its working efficiency and even possible damage. Summary of the invention

[0004] 1. Technical issues to be solved

[0005] In view of the deficiencies in the prior art, the present invention provides a modeling method for analyzing the harmonic interaction between a photovoltaic power station and a power distribution network, which solves the problems in the above-mentioned background technology.

[0006] (II) Technical solution

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions: A modeling method for analyzing the interaction effect of harmonics between a photovoltaic power station and a distribution network, comprising the following steps:

[0008] Step 1: When the PV power station interacts with the distribution network and the superposition effect of harmonics occurs, collect and record the data information of relevant equipment in the PV power station and the distribution network, relevant signal data information, and relevant harmonic data information of the power transformer, and transmit them to the operation status data center;

[0009] Step 2: Using Fourier transform technology to convert the relevant signal data information into a time domain signal, and obtain the phase information of each frequency component; and pre-process the relevant data information in the running status data set, including data cleaning and data standardization;

[0010] Step 3: Use harmonic analysis technology to extract the features of relevant harmonic data information and relevant signal data information of power transformers in photovoltaic power stations and distribution networks, obtain rated power Edgl, grounding resistance Jddz, voltage value Dyz and harmonic phase difference Xwcz, and establish a harmonic interaction impact analysis model between photovoltaic power stations and distribution networks, and transmit the relevant data information extracted from the features to the harmonic interaction impact analysis model between photovoltaic power stations and distribution networks;

[0011] Step 4: Generate a device damage factor Ssyz according to the relevant equipment parameter status when the photovoltaic power station interacts with the distribution network, and in combination with relevant equipment data information; associate the device damage factor Ssyz with the voltage value Dyz to obtain the grid stability factor Wdxs, associate the grid stability factor Wdxs with the harmonic phase difference Xwcz, and obtain the harmonic hazard index Wxzs after dimensionless processing. The harmonic hazard index Wxzs is obtained by the following formula:

[0012]

[0013] Wherein, Xppl represents the resonant frequency of the power transformer, Wdxs represents the grid stability factor, Xwcz represents the harmonic phase difference, F1 represents the proportional coefficient of the resonant frequency Xppl of the power transformer, F2 represents the proportional coefficient of the grid stability factor Wdxs, and F3 represents the proportional coefficient of the harmonic phase difference Xwcz, wherein 0.20≤F1≤0.50, 0.33≤F2≤0.62, 0.15≤F3≤0.46, and 0.80≤F1+F2+F3≤1.35, and R represents the constant correction factor;

[0014] Step 5: Use a harmonic analyzer to monitor the range of output harmonic frequencies in the photovoltaic power station, and record it as the output harmonic frequency range threshold Q, and compare and analyze the power transformer resonant frequency Xppl with the output harmonic frequency range threshold Q to evaluate whether the power transformer will be affected by resonance; and compare and analyze the harmonic risk index Wxzs with the pre-set assessment risk threshold K to obtain the corresponding level warning report.

[0015] Preferably, a data recorder, a harmonic analyzer and a signal collector are used to collect and record the relevant equipment data information, relevant signal data information and relevant harmonic data information of the power transformer in the photovoltaic power station and the distribution network respectively; wherein: the relevant equipment data information includes the operation time, load condition, voltage value, current value, power, maintenance times of the equipment, dust coverage degree and rated power value related data information of the relevant equipment in the photovoltaic power station and the distribution network;

[0016] The harmonic data information related to the power transformer includes the frequency, amplitude, harmonic distortion of each order of harmonics of the power transformer, and the magnetization and iron loss of the power transformer under the influence of harmonics;

[0017] The relevant signal data information includes the waveform, frequency, amplitude, phase of the voltage fundamental wave and the current fundamental wave in the harmonic signal and the fundamental wave signal, and the waveform, frequency, amplitude and phase relevant data information of the harmonic voltage and the harmonic current.

[0018] Preferably, the fundamental wave signal and the harmonic wave signal are phase analyzed respectively, and the time domain signal is converted into a frequency domain signal by using Fourier transform technology, from which the harmonic signal phase Xhxw1 and the fundamental wave signal phase Xhxw2 are obtained;

[0019] And preprocess the relevant data information in the operating status data set: identify and eliminate errors, outliers or noise in the data after form conversion, normalize and standardize the data, and extract useful feature data from it to reduce the dimension and complexity of the data.

[0020] Preferably, a harmonic interaction analysis model between the photovoltaic power station and the distribution network is established in advance, and the harmonic analysis technology is used to extract the characteristic information of the operating status data set in the photovoltaic power station and the distribution network to obtain: rated power Edgl, grounding resistance Jddz, temperature difference wdcz, voltage value Dyz, working time Gzsc, dust coverage Fglz and maintenance times Wxcs.

[0021] Preferably, after dimensionless processing, the power transformer resonant frequency Xppl is obtained by the following formula:

[0022]

[0023] In the formula, a1 is expressed as the proportional coefficient of the rated power Edgl, a2 is expressed as the proportional coefficient of the temperature difference wdcz, and a3 is expressed as the proportional coefficient of the grounding resistance Jddz. Among them, 0.30≤a1≤0.63, 0.15≤a2≤0.35, 0.35≤a3≤0.55, and 1.0≤a1+a2+a3≤1.30, and C is expressed as the constant correction coefficient.

[0024] Preferably, the power transformer resonant frequency Xppl is compared and analyzed with the output harmonic frequency range threshold Q to evaluate whether the power transformer will be affected by the resonance;

[0025] If the power transformer resonant frequency XPpl is greater than or equal to the output harmonic frequency range threshold Q, that is, XPpl ≥ Q, it means that the output harmonic frequency range in the current photovoltaic power station will not affect the working state of the transformer;

[0026] If the power transformer resonant frequency XPpl is less than the output harmonic frequency range threshold Q, that is, XPpl<Q, it means that the output harmonic frequency range in the current photovoltaic power station has affected the working state of the transformer, indirectly increasing the risk of magnetization loss and iron loss of the transformer.

[0027] Preferably, after dimensionless processing, the equipment damage factor Ssyz is obtained by the following formula:

[0028]

[0029] In the formula, b1 is expressed as the proportional coefficient of the working time Gzsc, b2 is expressed as the proportional coefficient of the dust coverage rate Fglz, and b3 is expressed as the proportional coefficient of the maintenance times Wxcs, among which, 0.10≤b1≤0.35, 0.25≤b2≤0.42, 0.15≤b3≤0.50, and 0.60≤b1+b2+b3≤1.0, and G is expressed as a constant correction coefficient.

[0030] Preferably, after dimensionless processing, the grid stability factor Wdxs is obtained by the following formula:

[0031]

[0032] In the formula, Fzz represents the load value, Dyz represents the voltage value, h1 represents the proportional coefficient of the load value Fzz, h2 represents the proportional coefficient of the voltage value Dyz, and h3 represents the proportional coefficient of the equipment damage factor Ssyz, wherein 0.20≤h1≤0.40, 0.22≤h2≤0.35, 0.30≤h3≤0.65, and 0.80≤h1+h2+h3≤1.20, and J represents the constant correction coefficient.

[0033] Preferably, after dimensionless processing, the harmonic phase difference Xwcz is obtained by the following formula:

[0034] Xwcz=|Xhxw1-Xhxw2|;

[0035] Wherein, Xhxw1 represents the phase of harmonic signal, and Xhxw2 represents the phase of fundamental signal.

[0036] Preferably, an evaluation danger threshold K is preset, and the evaluation danger threshold K is compared and analyzed with the harmonic danger index Wxzs to obtain a level warning report;

[0037] If the harmonic risk index Wxzs is greater than the assessment risk threshold K, that is, Wxzs>K, the first warning notification is obtained and a red alarm is sent, indicating that the current harmonic risk level exceeds 45%. At this time, it is necessary to check the harmonic source in the distribution network in time;

[0038] If the harmonic risk index Wxzs is equal to the assessment risk threshold K, that is, Wxzs=K, a second warning notification is obtained and a yellow alarm is sent, indicating that the current harmonic risk level has reached the critical point of the assessment, and it is necessary to pay close attention to the development trend of the harmonic problem, strengthen real-time monitoring, adjust the operation mode of the photovoltaic power station, or strengthen the management and control of the harmonic source of the distribution network;

[0039] If the harmonic hazard index Wxzs is less than the assessment hazard threshold K, that is, Wxzs<K, a third warning notification is obtained and a green alarm is sent, indicating that the current harmonic hazard level does not exceed 45% and the power system is in a relatively safe state; monitoring and maintenance will continue at this time.

[0040] (III) Beneficial effects

[0041] The present invention provides a modeling method for analyzing the harmonic interaction between a photovoltaic power station and a distribution network, which has the following beneficial effects:

[0042] (1) The method first collects data information of relevant equipment, relevant signal data information and relevant harmonic data information of power transformers in photovoltaic power stations and distribution networks in many aspects to provide a multi-faceted data basis for subsequent analysis; at the same time, the Fourier transform technology is used to convert the time domain signal into a frequency domain signal, and the relevant data is preprocessed, which is conducive to the accuracy and effectiveness of subsequent feature extraction and analysis; then the harmonic analysis technology is used to extract the relevant harmonic data information and features of power transformers in photovoltaic power stations and distribution networks, and a set of analysis models is established to further evaluate the degree and influencing factors of harmonic interaction between photovoltaic power stations and distribution networks; through the calculation and analysis of the resonant frequency Xppl of the power transformer, it is possible to timely find out whether the power transformer will be affected by resonance, and provide early warning notifications through the level early warning report, effectively preventing the potential harm caused by harmonic interaction to the stable operation of the power system. In short, the modeling method of the harmonic interaction analysis model of photovoltaic power stations and distribution networks provided by the present invention can timely predict whether the power transformers distributed in photovoltaic power stations and distribution networks will have resonance effects, and further reduce the possibility of magnetization and iron loss of power transformers.

[0043] (2) Compare and analyze the harmonic hazard index Wxzs and the assessment hazard threshold K, and obtain the corresponding early warning notice: and collect corresponding solutions for different early warning notices, which helps to ensure the long-term safe operation of the power system and provides staff with sufficient time to carry out subsequent preventive measures and maintenance work. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The present invention is a schematic diagram of a flowchart of a method for modeling a harmonic interaction analysis model between a photovoltaic power station and a distribution network. DETAILED DESCRIPTION

[0045] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] In the modern energy field, photovoltaic power stations are an important part of clean energy generation, and the interaction between them and the distribution network has become a key issue in power system optimization. In particular, when photovoltaic power stations interact with the distribution network and the superposition effect of harmonics occurs, it has an unignorable impact on the stability and reliability of the power system.

[0047] In the interaction between traditional photovoltaic power stations and distribution networks, lower frequency harmonics are generated, which will not have a significant impact on the resonant frequency of the power transformer. Therefore, in the design and operation of the power system, the harmonic frequency impact of the power transformer is usually negligible. However, the harmonics generated by photovoltaic power stations have the characteristics of high frequency and wide frequency domain. The harmonic frequency range is wide and contains relatively high frequency components. These high-frequency and wide-frequency harmonic signals are prone to resonate with the resonant frequency of the power transformer, causing the occurrence of resonance effect, increasing the magnetization and iron loss of the power transformer, resulting in a decrease in its working efficiency and even possible damage.

[0048] Example 1

[0049] See also Figure 1 The present invention provides a method for modeling a photovoltaic power station and a power distribution network harmonic interaction analysis model, comprising the following steps:

[0050] Step 1: When the PV power station interacts with the distribution network and the superposition effect of harmonics occurs, collect and record the data information of relevant equipment in the PV power station and the distribution network, relevant signal data information, and relevant harmonic data information of the power transformer, and transmit them to the operation status data center;

[0051] Step 2: Using Fourier transform technology to convert the relevant signal data information into a time domain signal, and obtain the phase information of each frequency component; and pre-process the relevant data information in the running status data set, including data cleaning and data standardization;

[0052] Step 3: Use harmonic analysis technology to extract the features of relevant harmonic data information and relevant signal data information of power transformers in photovoltaic power stations and distribution networks, obtain rated power Edgl, grounding resistance Jddz, voltage value Dyz and harmonic phase difference Xwcz, and establish a harmonic interaction impact analysis model between photovoltaic power stations and distribution networks, and transmit the relevant data information extracted from the features to the harmonic interaction impact analysis model between photovoltaic power stations and distribution networks;

[0053] Step 4: Generate a device damage factor Ssyz according to the relevant equipment parameter status when the photovoltaic power station interacts with the distribution network, and in combination with relevant equipment data information; associate the device damage factor Ssyz with the voltage value Dyz to obtain the grid stability factor Wdxs, associate the grid stability factor Wdxs with the harmonic phase difference Xwcz, and obtain the harmonic hazard index Wxzs after dimensionless processing. The harmonic hazard index Wxzs is obtained by the following formula:

[0054]

[0055] Wherein, Xppl represents the resonant frequency of the power transformer, Wdxs represents the grid stability factor, Xwcz represents the harmonic phase difference, F1 represents the proportional coefficient of the resonant frequency Xppl of the power transformer, F2 represents the proportional coefficient of the grid stability factor Wdxs, and F3 represents the proportional coefficient of the harmonic phase difference Xwcz, wherein 0.20≤F1≤0.50, 0.33≤F2≤0.62, 0.15≤F3≤0.46, and 0.80≤F1+F2+F3≤1.35, and R represents the constant correction factor;

[0056] Step 5: Use a harmonic analyzer to monitor the range of output harmonic frequencies in the photovoltaic power station, and record it as the output harmonic frequency range threshold Q, and compare and analyze the power transformer resonant frequency Xppl with the output harmonic frequency range threshold Q to evaluate whether the power transformer will be affected by resonance; and compare and analyze the harmonic risk index Wxzs with the pre-set assessment risk threshold K to obtain the corresponding level warning report.

[0057] In this embodiment, through step one, relevant equipment data information, relevant signal data information and power transformer related harmonic data information in photovoltaic power stations and distribution networks can be collected in many aspects, providing a multi-faceted data basis for subsequent analysis; at the same time, the time domain signal is converted into a frequency domain signal by Fourier transform technology, and the relevant data is pre-processed, including cleaning and standardization; through step three, the harmonic analysis technology is used to extract the relevant harmonic data information and characteristics of power transformers in photovoltaic power stations and distribution networks, and a set of analysis models is established; through steps four and five, the equipment damage factor Ssyz, the power grid stability factor Wdxs and the power transformer resonant frequency Xppl are further accurately evaluated, and it is timely discovered whether the power transformer will be affected by resonance, and a warning notification is provided through a level warning report to effectively prevent the potential harm of harmonic interaction to the stable operation of the power system.

[0058] Example 2

[0059] Please refer to Figure 1 Specifically: using data recorders, harmonic analyzers and signal collectors to collect and record relevant equipment data information, relevant signal data information and power transformer-related harmonic data information in photovoltaic power stations and distribution networks; wherein: relevant equipment data information includes the operation time, load conditions, voltage value, current value, power, equipment maintenance times, dust coverage and rated power value related data information of relevant equipment in photovoltaic power stations and distribution networks;

[0060] The harmonic data information related to the power transformer includes the frequency, amplitude, harmonic distortion of each order of harmonics of the power transformer, and the magnetization and iron loss of the power transformer under the influence of harmonics;

[0061] The relevant signal data information includes the waveform, frequency, amplitude, phase of the voltage fundamental wave and the current fundamental wave in the harmonic signal and the fundamental wave signal, and the waveform, frequency, amplitude and phase relevant data information of the harmonic voltage and the harmonic current.

[0062] Among them, the above-mentioned fundamental wave signal in photovoltaic power stations and distribution stations usually refers to the voltage or current signal in the power supply network, representing the basic working state of the power system. In the photovoltaic power station, the fundamental wave signal refers to the basic frequency signal after the solar panel converts solar energy into DC power and then converts it into AC power through the inverter. In the distribution network, the fundamental wave signal refers to the basic frequency signal in the power system transmitted from the power plant to the end user.

[0063] Perform phase analysis on the fundamental wave signal and the harmonic wave signal respectively, and use Fourier transform technology to convert the time domain signal into the frequency domain signal, from which the harmonic signal phase Xhxw1 and the fundamental wave signal phase Xhxw2 are obtained;

[0064] And preprocess the relevant data information in the operating status data set: identify and eliminate errors, outliers or noise in the data after form conversion, normalize and standardize the data, and extract useful feature data from it to reduce the dimension and complexity of the data.

[0065] In this embodiment, the data recorder, harmonic analyzer and signal collector involved in this method can respectively collect key data in the photovoltaic power station and the distribution network, including equipment operating conditions, voltage and current parameters, harmonic distortion conditions and equipment maintenance history data, providing a multi-faceted and accurate data basis for subsequent analysis; in addition, through the normalization and standardization of the data, it helps to reduce the data dimension and complexity, and extract key data related to harmonic feature analysis.

[0066] Example 3

[0067] Please refer to Figure 1 Specifically: a harmonic interaction impact analysis model between photovoltaic power stations and distribution networks is established in advance, and harmonic analysis technology is used to extract the characteristic information of the operating status data set in photovoltaic power stations and distribution networks to obtain: rated power Edgl, grounding resistance Jddz, temperature difference wdcz, voltage value Dyz, working time Gzsc, dust coverage rate Fglz and maintenance times Wxcs.

[0068] After dimensionless processing, the power transformer resonant frequency Xppl is obtained by the following formula:

[0069]

[0070] In the formula, a1 is expressed as the proportional coefficient of the rated power Edgl, a2 is expressed as the proportional coefficient of the temperature difference wdcz, and a3 is expressed as the proportional coefficient of the grounding resistance Jddz. Among them, 0.30≤a1≤0.63, 0.15≤a2≤0.35, 0.35≤a3≤0.55, and 1.0≤a1+a2+a3≤1.30, and C is expressed as the constant correction coefficient.

[0071] The above rated power Edgl is usually obtained from the transformer identification plate or technical parameter manual;

[0072] The grounding resistance Jddz is usually measured by a grounding resistance tester, which applies a specific current or voltage between the grounding electrode and the grounding body and measures the resulting resistance value to evaluate the grounding resistance.

[0073] The temperature difference wdcz is collected and obtained through a temperature sensor.

[0074] Compare and analyze the power transformer resonant frequency Xppl with the output harmonic frequency range threshold Q to evaluate whether the power transformer will be affected by resonance;

[0075] If the power transformer resonant frequency XPpl is greater than or equal to the output harmonic frequency range threshold Q, that is, XPpl ≥ Q, it means that the output harmonic frequency range in the current photovoltaic power station will not affect the working state of the transformer, and it is not easy for resonance to cause damage to the transformer;

[0076] If the power transformer resonant frequency XPpl is less than the output harmonic frequency range threshold Q, that is, XPpl<Q, it means that the output harmonic frequency range in the current photovoltaic power station has affected the working state of the transformer, indirectly increasing the risk of magnetization loss and iron loss of the transformer.

[0077] In this embodiment, by comparing and analyzing the calculated power transformer resonant frequency XPpl with the output harmonic frequency range threshold Q, potential resonance risks can be identified in a timely manner to avoid increasing the magnetization and iron loss of the power transformer due to the resonance phenomenon, resulting in a decrease in its working efficiency or even possible damage.

[0078] Example 4

[0079] Please refer to Figure 1 Specifically: After dimensionless processing, the equipment damage factor Ssyz is obtained by the following formula:

[0080]

[0081] In the formula, b1 is expressed as the proportional coefficient of the working time Gzsc, b2 is expressed as the proportional coefficient of the dust coverage rate Fglz, and b3 is expressed as the proportional coefficient of the maintenance times Wxcs, among which, 0.10≤b1≤0.35, 0.25≤b2≤0.42, 0.15≤b3≤0.50, and 0.60≤b1+b2+b3≤1.0, and G is expressed as a constant correction coefficient.

[0082] The above working time Gzsc refers to the working time of the relevant equipment in the photovoltaic power station and the distribution network, and is monitored and obtained in real time through the running time sensor;

[0083] The dust coverage rate Fglz refers to the dust area covered on the surface of related equipment in the photovoltaic power station and distribution network, and is monitored and obtained through dust sensors or infrared cameras;

[0084] The number of maintenance times Wxcs refers to the number of maintenance times of related equipment in the PV power station and distribution network, and is tracked and collected through maintenance records or maintenance logs.

[0085] After dimensionless processing, the grid stability factor Wdxs is obtained by the following formula:

[0086]

[0087] In the formula, Fzz represents the load value, Dyz represents the voltage value, h1 represents the proportional coefficient of the load value Fzz, h2 represents the proportional coefficient of the voltage value Dyz, and h3 represents the proportional coefficient of the equipment damage factor Ssyz, wherein 0.20≤h1≤0.40, 0.22≤h2≤0.35, 0.30≤h3≤0.65, and 0.80≤h1+h2+h3≤1.20, and J represents the constant correction coefficient.

[0088] After dimensionless processing, the harmonic phase difference Xwcz is obtained by the following formula:

[0089] Xwcz=|Xhxw1-Xhxw2|;

[0090] Wherein, Xhxw1 represents the phase of harmonic signal, and Xhxw2 represents the phase of fundamental signal.

[0091] In this embodiment, based on the collected working time Gzsc, dust coverage Fglz, maintenance times Wxcs and other related information, and by using appropriate sensors and equipment to monitor and record these parameters in real time, the equipment damage factor Ssyz is analyzed and calculated, which helps to evaluate the current loss status of the equipment and further evaluate the grid stability factor Wdxs. By combining the load value Fzz and the voltage value Dyz with the equipment damage factor Ssyz for comprehensive analysis, the grid stability factor Wdxs is obtained to evaluate the stability of the grid. In addition, the calculation of the harmonic phase difference Xwcz can help further understand the harmonic situation in the system and provide key data for analyzing the interaction of harmonics. By comprehensively utilizing these data and parameters, the interaction of harmonics between photovoltaic power stations and distribution networks can be effectively evaluated, and an important reference basis for maintenance work can be provided.

[0092] Example 5

[0093] Please refer to Figure 1 Specifically: pre-set the evaluation hazard threshold K, and compare and analyze the evaluation hazard threshold K with the harmonic hazard index Wxzs to obtain a level warning report;

[0094] If the harmonic hazard index Wxzs is greater than the assessment hazard threshold K, that is, Wxzs>K, the first warning notification is obtained and a red alarm is sent, indicating that the current harmonic hazard level exceeds 45%. The harmonic source in the distribution network is checked and on-site detection and positioning are performed to identify the specific location and characteristics of the harmonic source; real-time monitoring is performed on the harmonic source to record the harmonic characteristics and spectrum distribution it generates.

[0095] If the harmonic risk index Wxzs is equal to the assessment risk threshold K, that is, Wxzs=K, a second warning notification is obtained and a yellow alarm is sent, indicating that the current harmonic risk level has reached the critical point of the assessment, and it is necessary to pay close attention to the development trend of the harmonic problem; measures may include strengthening real-time monitoring, adjusting the operation mode of the photovoltaic power station, and strengthening the management and control of the harmonic source of the distribution network;

[0096] If the harmonic hazard index Wxzs is less than the assessment hazard threshold K, that is, Wxzs<K, a third warning notification is obtained and a green alarm is sent, indicating that the current harmonic hazard level does not exceed 45% and the power system is in a relatively safe state; monitoring and maintenance will continue at this time.

[0097] In this embodiment, a comparative analysis is performed based on the set assessment danger threshold K and the actual harmonic danger index Wxzs, and a corresponding early warning notification can be obtained: the sending of the first early warning notification helps to identify in real time the situation where the harmonic danger level exceeds 45%, and guide the staff to take emergency measures, such as by checking the harmonic source in the distribution network and conducting on-site detection and positioning, quickly identifying and locating the problem source, and taking targeted measures to reduce the impact of harmonics on the power system; the sending of the second early warning notification can attract the staff's attention to the development trend of the harmonic problem, prompting them to strengthen real-time monitoring and control to ensure that the harmonic problem will not deteriorate further; the sending of the third early warning notification indicates that the power system is in a relatively safe state, but it still needs to be continuously monitored and maintained.

[0098] Example:

[0099] Data collection: rated power Edgl is 12; temperature difference wdcz is 8; grounding resistance Jddz is 15; a1 is 0.52; a2 is 0.20; a3 is 0.36; C is 2; working time Gzsc is 8.9; dust coverage Fglz is 68%; maintenance times Wxcs is 3; b1 is 0.15; b2 is 0.30; b3 is 0.33; G is 3; load value Fzz is 53; voltage value Dyz is 40; h1 is 0.22; h2 is 0.32; h3 is 0.39; J is 2; harmonic signal phase Xhxw1 is 35; fundamental signal phase Xhxw2 is 22; F1 is 0.22; F2 is 0.35; F3 is 0.30; R is 3;

[0100] With the above data, the following calculations can be performed:

[0101]

[0102] Harmonic phase difference Xwcz = |35-22| = 13;

[0103]

[0104] If the preset assessment danger threshold K is 25, the harmonic danger index Wxzs is greater than the assessment danger threshold K, that is, Wxzs>K, and the first warning notification is obtained, and a red alarm is sent, indicating that the current harmonic danger level exceeds 45%. Check the harmonic source in the distribution network and conduct on-site detection and positioning to identify the specific location and characteristics of the harmonic source; conduct real-time monitoring of the harmonic source and record the harmonic characteristics and spectrum distribution it generates.

[0105] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A modeling method for analyzing the interaction effect of harmonics between a photovoltaic power station and a distribution network, characterized by: The following steps are included: Step 1: When the photovoltaic power station interacts with the distribution network and the superposition effect of harmonics occurs, collect and record the data information of relevant equipment in the photovoltaic power station and the distribution network, relevant signal data information, and relevant harmonic data information of the power transformer, and transmit them to the operation status data center; The data recorder, harmonic analyzer and signal collector are used to collect and record the relevant equipment data information, relevant signal data information and relevant harmonic data information of the power transformer in the photovoltaic power station and the distribution network respectively; wherein: the relevant equipment data information includes the operation time, load condition, voltage value, current value, power, equipment maintenance times, dust coverage degree and rated power value related data information of the relevant equipment in the photovoltaic power station and the distribution network; The harmonic data information related to the power transformer includes the frequency, amplitude, harmonic distortion of each order of harmonics of the power transformer, and the magnetization and iron loss of the power transformer under the influence of harmonics; The relevant signal data information includes the waveform, frequency, amplitude, phase of the voltage fundamental wave and the current fundamental wave, and the waveform, frequency, amplitude and phase related data information of the harmonic voltage and the harmonic current in the harmonic signal and the fundamental wave signal; Perform phase analysis on the fundamental wave signal and the harmonic wave signal respectively, and use Fourier transform technology to convert the time domain signal into the frequency domain signal, from which the harmonic signal phase Xhxw1 and the fundamental wave signal phase Xhxw2 are obtained; And preprocess the relevant data information in the running status data set: identify and eliminate errors, outliers or noise in the converted data, normalize and standardize the data, and extract useful feature data from it to reduce the dimension and complexity of the data; Step 2: Using Fourier transform technology to convert the relevant signal data information into a time domain signal, and obtain the phase information of each frequency component; and pre-process the relevant data information in the running status data set, including data cleaning and data standardization; Step 3: Use harmonic analysis technology to extract the features of relevant harmonic data information and relevant signal data information of power transformers in photovoltaic power stations and distribution networks, obtain rated power Edgl, grounding resistance Jddz, voltage value Dyz and harmonic phase difference Xwcz, and establish a harmonic interaction impact analysis model between photovoltaic power stations and distribution networks, and transmit the relevant data information extracted from the features to the harmonic interaction impact analysis model between photovoltaic power stations and distribution networks; Step 4: Generate a device damage factor Ssyz according to the relevant equipment parameter status when the photovoltaic power station interacts with the distribution network, and in combination with relevant equipment data information; associate the device damage factor Ssyz with the voltage value Dyz to obtain the grid stability factor Wdxs, associate the grid stability factor Wdxs with the harmonic phase difference Xwcz, and obtain the harmonic hazard index Wxzs after dimensionless processing. The harmonic hazard index Wxzs is obtained by the following formula: Wherein, Xppl represents the resonant frequency of the power transformer, Wdxs represents the grid stability factor, Xwcz represents the harmonic phase difference, F1 represents the proportional coefficient of the resonant frequency Xppl of the power transformer, F2 represents the proportional coefficient of the grid stability factor Wdxs, and F3 represents the proportional coefficient of the harmonic phase difference Xwcz, wherein 0.20≤F1≤0.50, 0.33≤F2≤0.62, 0.15≤F3≤0.46, and 0.80≤F1+F2+F3≤1.35, and R represents the constant correction factor; After dimensionless processing, the power transformer resonant frequency Xppl is obtained by the following formula: Wherein, a1 represents the proportional coefficient of rated power Edgl, a2 represents the proportional coefficient of temperature difference wdcz, a3 represents the proportional coefficient of grounding resistance Jddz, wherein 0.30≤a1≤0.63, 0.15≤a2≤0.35, 0.35≤a3≤0.55, and 1.0≤a1+a2+a3≤1.30, and C represents the constant correction coefficient; After dimensionless processing, the equipment damage factor Ssyz is obtained by the following formula: Wherein, b1 is the proportional coefficient of the working time Gzsc, b2 is the proportional coefficient of the dust coverage rate Fglz, b3 is the proportional coefficient of the maintenance times Wxcs, where 0.10≤b1≤0.35, 0.25≤b2≤0.42, 0.15≤b3≤0.50, and 0.60≤b1+b2+b3≤1.0, and G is the constant correction coefficient; After dimensionless processing, the grid stability factor Wdxs is obtained by the following formula: Wherein, Fzz represents the load value, Dyz represents the voltage value, h1 represents the proportional coefficient of the load value Fzz, h2 represents the proportional coefficient of the voltage value Dyz, h3 represents the proportional coefficient of the equipment damage factor Ssyz, wherein 0.20≤h1≤0.40, 0.22≤h2≤0.35, 0.30≤h3≤0.65, and 0.80≤h1+h2+h3≤1.20, and J represents the constant correction coefficient; After dimensionless processing, the harmonic phase difference Xwcz is obtained by the following formula: Xwcz=|Xhxw1-Xhxw2|; In the formula, Xhxw1 represents the phase of the harmonic signal, and Xhxw2 represents the phase of the fundamental signal; Step 5: Use a harmonic analyzer to monitor the range of output harmonic frequencies in the photovoltaic power station, and record it as the output harmonic frequency range threshold Q, and compare and analyze the power transformer resonant frequency Xppl with the output harmonic frequency range threshold Q to evaluate whether the power transformer will be affected by resonance; and compare and analyze the harmonic risk index Wxzs with the preset assessment risk threshold K to obtain the corresponding level warning report; Compare and analyze the power transformer resonant frequency Xppl with the output harmonic frequency range threshold Q to evaluate whether the power transformer will be affected by resonance; If the power transformer resonant frequency XPpl is greater than or equal to the output harmonic frequency range threshold Q, that is, XPpl ≥ Q, it means that the output harmonic frequency range in the current photovoltaic power station will not affect the working state of the transformer; If the power transformer resonant frequency XPpl is less than the output harmonic frequency range threshold Q, that is, XPpl<Q, it means that the output harmonic frequency range in the current photovoltaic power station has affected the working state of the transformer, indirectly increasing the risk of magnetization loss and iron loss of the transformer.

2. A photovoltaic power station and distribution network harmonic interaction analysis model modeling method according to claim 1, characterized in that: A harmonic interaction analysis model between photovoltaic power stations and distribution networks is established in advance, and harmonic analysis technology is used to extract the characteristic information of the operating status data set in photovoltaic power stations and distribution networks to obtain: rated power Edgl, grounding resistance Jddz, temperature difference wdcz, voltage value Dyz, working time Gzsc, dust coverage rate Fglz and maintenance number Wxcs.

3. The method for modeling a photovoltaic power station and a power distribution network harmonic interaction analysis model according to claim 1, characterized in that: Pre-set the evaluation hazard threshold K, and compare and analyze the evaluation hazard threshold K with the harmonic hazard index Wxzs to obtain a level warning report; If the harmonic risk index Wxzs is greater than the assessment risk threshold K, that is, Wxzs>K, the first warning notification is obtained and a red alarm is sent, indicating that the current harmonic risk level exceeds 45%. At this time, it is necessary to check the harmonic source in the distribution network in time; If the harmonic risk index Wxzs is equal to the assessment risk threshold K, that is, Wxzs=K, a second warning notification is obtained and a yellow alarm is sent, indicating that the current harmonic risk level has reached the critical point of the assessment, and it is necessary to pay close attention to the development trend of the harmonic problem, strengthen real-time monitoring, adjust the operation mode of the photovoltaic power station, or strengthen the management and control of the harmonic source of the distribution network; If the harmonic hazard index Wxzs is less than the assessment hazard threshold K, that is, Wxzs<K, a third warning notification is obtained and a green alarm is sent, indicating that the current harmonic hazard level does not exceed 45% and the power system is in a relatively safe state; monitoring and maintenance will continue at this time.

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