Harmonic control method and system for inverter of photovoltaic power station

Abstract

The invention discloses a photovoltaic power station inverter harmonic control method and system, and relates to the technical field of photovoltaic power generation. Comprising the steps of performing harmonic analysis on output of a power grid and an inverter, and establishing harmonic models of the output of the power grid and the inverter; determining harmonic information according to the harmonic model; correcting the harmonic frequency obtained in the harmonic model; setting target control parameters of a filter based on the harmonic information, and filtering; meanwhile, defining a filtering effect, and setting an adjusting period for monitoring a filtering process; and adjusting the target control parameter of the next adjustment period according to the filtering effect of the previous adjustment period. According to the method, harmonic analysis is carried out on the output of the power grid and the inverter, and the harmonic model of the output of the power grid and the inverter is established, so that accurate analysis and modeling of harmonic characteristics are realized, and a reliable data basis is provided for subsequent harmonic control; meanwhile, multiple factors such as power grid fluctuation, inverter characteristics and load influence are considered, and the adaptability of the system is enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic power generation, and in particular to a method and system for controlling harmonics of a photovoltaic power station inverter. Background Art

[0002] Harmonic control of photovoltaic power station inverters is an important technical measure taken in photovoltaic power stations to reduce the adverse effects of harmonics on power grids and equipment. Harmonics refer to different frequency components that exist in the power grid at integer multiples of the fundamental frequency (usually 50Hz or 60Hz). These harmonic components are mainly generated by nonlinear loads (such as inverters, rectifiers, etc.). Harmonics can cause grid voltage distortion, equipment overheating, communication interference, and affect other users' electrical equipment. Therefore, harmonic control is an important issue in the operation of photovoltaic power stations and access to the power grid.

[0003] In the existing technology, the accuracy of harmonic control is poor and cannot adapt to the complex changes of photovoltaic power generation and power grid. If the harmonics are too high, the distortion of the power grid is high and the power quality is poor. If the harmonics are too low, the cost increases sharply and cannot adapt to the complexity of the system.

[0004] Therefore, how to improve the accuracy and adaptability of harmonic control is a technical problem that needs to be solved. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention is proposed.

[0006] Therefore, the problem to be solved by the present invention is how to solve the technical problems of low harmonic control accuracy and poor adaptability in the prior art.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] In a first aspect, an embodiment of the present invention provides a method for controlling harmonics of a photovoltaic power station inverter, which includes performing harmonic analysis on the output of a power grid and an inverter, and establishing a harmonic model of the output of the power grid and the inverter;

[0009] determining harmonic information according to a harmonic model;

[0010] Correct the harmonic frequency obtained in the harmonic model;

[0011] The target control parameters of the filter are set based on the harmonic information, and filtering is performed;

[0012] At the same time, define the filtering effect and set the adjustment cycle for monitoring the filtering process;

[0013] The target control parameters of the next regulation cycle are adjusted according to the filtering effect of the previous regulation cycle.

[0014] As a preferred solution of the photovoltaic power station inverter harmonic control method of the present invention, wherein: and establish a harmonic model of the power grid and the inverter output, including:

[0015] Collect voltage and current waveform data output by the power grid and inverter;

[0016] Perform data filtering, noise removal and spurious processing on voltage and current waveform data;

[0017] Perform fast Fourier transform on the voltage and current waveform data to convert the time domain data into frequency domain data;

[0018] Perform spectrum analysis on the frequency domain data to obtain the spectrum diagram of voltage and current, so as to establish the harmonic model of the power grid and inverter output.

[0019] As a preferred solution of the photovoltaic power station inverter harmonic control method of the present invention, the specific steps of correcting the harmonic frequency obtained in the harmonic model include:

[0020] Define the fluctuation level of the power grid frequency, which is determined based on the power grid frequency monitoring data;

[0021] Determine the first influencing factor according to the design of the inverter and the control strategy, and the first influencing factor is used to characterize the influence of the inverter's own characteristics on the harmonics;

[0022] The second influencing factor is determined according to the load type and capacity output by the inverter, and the second influencing factor is used to characterize the influence of the load on the harmonics;

[0023] The harmonic frequency is corrected based on the fluctuation level, the first impact factor and the second impact factor.

[0024] As a preferred solution of the photovoltaic power station inverter harmonic control method of the present invention, wherein: setting the target control parameters of the filter based on the harmonic information includes:

[0025] Harmonic information includes harmonic frequency and content, and target control parameters include filter cutoff frequency, filter order and impedance;

[0026] Determine the filter cutoff frequency according to the range of harmonic frequencies;

[0027] Determine the filter order based on the content and harmonic components;

[0028] The impedance is determined based on the inverter output impedance and the grid impedance.

[0029] As a preferred solution of the photovoltaic power station inverter harmonic control method of the present invention, wherein: adjusting the target control parameters of the next regulation cycle according to the filtering effect of the previous regulation cycle includes:

[0030] If the filtering effect of the previous adjustment cycle is lower than the filtering effect threshold corresponding to this cycle, a correction coefficient is determined according to the difference between the filtering effect of the previous adjustment cycle and the filtering effect threshold to adjust the target control parameter of the next adjustment cycle;

[0031] Otherwise, the target control parameter of the next regulation cycle is not adjusted.

[0032] As a preferred solution of the photovoltaic power station inverter harmonic control method of the present invention, the determination of harmonic information includes:

[0033] Collect voltage and current waveform data of the power grid and inverter output through harmonic monitoring equipment;

[0034] Performing fast Fourier transform on the collected data to obtain frequency domain data;

[0035] Perform spectrum analysis on frequency domain data to determine the harmonic frequency range and content.

[0036] As a preferred solution of the photovoltaic power station inverter harmonic control method of the present invention, the definition of filtering effect includes:

[0037] Reduce harmonic content and grid distortion;

[0038] Comply with grid standard indicators, improve power quality indicators, and equipment protection effect indicators.

[0039] In a second aspect, an embodiment of the present invention provides a photovoltaic power station inverter harmonic control system, which includes a harmonic analysis module, a harmonic information module, a harmonic correction module, a filtering control module, an effect definition module and a parameter adjustment module;

[0040] The harmonic analysis module is used to perform harmonic analysis on the output of the power grid and the inverter, and to establish harmonic models of the output of the power grid and the inverter;

[0041] The harmonic information module is used to determine the harmonic information according to the harmonic model;

[0042] The harmonic correction module is used to correct the harmonic frequency obtained in the harmonic model;

[0043] The filter control module is used to set the target control parameters of the filter based on the harmonic information and perform filtering;

[0044] The effect definition module is used to define the filtering effect and set the adjustment cycle of the monitoring filtering process;

[0045] The parameter adjustment module is used to adjust the target control parameters of the next adjustment cycle according to the filtering effect of the previous adjustment cycle.

[0046] In a third aspect, an embodiment of the present invention provides a computer device, including a memory and a processor, wherein the memory stores a computer program, wherein: when the computer program instructions are executed by the processor, the steps of the photovoltaic power station inverter harmonic control method as in the first aspect of the present invention are implemented.

[0047] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein: when the computer program instructions are executed by a processor, the steps of the photovoltaic power station inverter harmonic control method of the first aspect of the present invention are implemented.

[0048] The beneficial effects of the present invention are as follows: the photovoltaic power station inverter harmonic control method provided by the present invention performs harmonic analysis on the output of the power grid and the inverter, and establishes a harmonic model of the power grid and the inverter output, thereby realizing accurate analysis and modeling of harmonic characteristics, and providing a reliable data basis for subsequent harmonic control; by determining harmonic information according to the harmonic model, and correcting the harmonic frequency obtained in the harmonic model, the accuracy of harmonic frequency determination is improved, and multiple factors such as power grid fluctuations, inverter characteristics and load influence are considered at the same time, thereby enhancing the adaptability of the system; by setting the target control parameters of the filter based on the harmonic information and filtering, accurate control of harmonics is achieved, the adverse effects of harmonics on the power grid are reduced, the power quality is improved, and the system loss is reduced; by defining the filtering effect and setting the adjustment cycle for monitoring the filtering process, and adjusting the target control parameters of the next adjustment cycle according to the filtering effect of the previous adjustment cycle, the system has an adaptive adjustment capability, and the continuous optimization of harmonic control and the stable operation of the system are guaranteed. The present invention has achieved better effects in terms of harmonic control accuracy, system adaptability and operation stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0050] Figure 1 It is a flow chart of the harmonic control method of the photovoltaic power station inverter;

[0051] Figure 2 This is a schematic diagram of the structure of the harmonic control system of the photovoltaic power station inverter; DETAILED DESCRIPTION

[0052] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0053] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0054] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0055] Example 1

[0056] Reference Figure 1 , which is the first embodiment of the present invention, and provides a method for controlling harmonics of a photovoltaic power station inverter, comprising:

[0057] S1, perform harmonic analysis on the output of the power grid and the inverter, and establish a harmonic model of the output of the power grid and the inverter;

[0058] In the embodiment of the present application, a harmonic model of the power grid and the inverter output is established, including:

[0059] Collect voltage and current waveform data output by the power grid and inverter;

[0060] Perform data filtering, noise removal and spurious processing on voltage and current waveform data;

[0061] Perform fast Fourier transform on the voltage and current waveform data to convert the time domain data into frequency domain data;

[0062] Perform spectrum analysis on the frequency domain data to obtain the spectrum diagram of voltage and current, so as to establish the harmonic model of the power grid and inverter output.

[0063] It should be noted that converting time domain data into frequency domain data through spectrum analysis methods such as fast Fourier transform (FFT) is a commonly used harmonic analysis technology, but there may be some problems in practical applications, including:

[0064] Resolution problem: The resolution of FFT depends on the sampling rate and the duration of the signal. A lower sampling rate or a shorter signal duration may result in insufficient spectrum resolution, causing low-amplitude harmonic components to be ignored or unable to be accurately measured.

[0065] Window function impact: When FFT performs spectrum analysis on time domain data, the data needs to be truncated, which may introduce spectrum leakage. In order to reduce the impact of leakage, a window function is usually applied, but choosing an inappropriate window function may also lead to inaccurate spectrum analysis results.

[0066] Window length: The accuracy and spectral resolution of FFT are also related to the window length. A shorter window length may result in reduced spectral resolution, while a longer window length may result in reduced time resolution.

[0067] Spectrum fluctuation: FFT is a spectrum analysis method based on a finite time window. The accuracy of the spectrum is affected by factors such as noise and window length, which may cause spectrum fluctuations.

[0068] Spectral leakage: When the frequencies of a signal are not exact multiples of the FFT analysis, it can cause spectral leakage, where harmonic energy is spread to other frequencies.

[0069] Phase information is lost: FFT only provides frequency amplitude information, but loses the phase information of the original signal. In some applications, phase information may be very important.

[0070] To overcome these problems, the following measures can be taken:

[0071] Increase the sampling rate to ensure sufficient spectral resolution.

[0072] Use appropriate window functions to reduce spectrum leakage and fluctuations.

[0073] Consider various spectrum analysis methods, such as beamforming.

[0074] For the need of phase information, other harmonic analysis methods can be considered, such as wavelet transform (WaveletTransform) and so on.

[0075] S2, determining harmonic information according to the harmonic model;

[0076] In the embodiment of the present application, the determination of harmonic information includes:

[0077] Collect voltage and current waveform data of the power grid and inverter output through harmonic monitoring equipment;

[0078] Performing fast Fourier transform on the collected data to obtain frequency domain data;

[0079] Perform spectrum analysis on frequency domain data to determine the harmonic frequency range and content.

[0080] It should be noted that the following are the general steps for determining the harmonic frequency range:

[0081] Harmonic monitoring: First, you need to install harmonic monitoring equipment to monitor the grid side and inverter output side of the photovoltaic power station. These devices will record the voltage and current waveforms of the grid and inverter output and convert them into frequency domain data.

[0082] Data acquisition and processing: The voltage and current waveform data collected by the harmonic monitoring equipment needs to be processed, usually by converting the time domain data into frequency domain data through spectrum analysis methods such as fast Fourier transform (FFT).

[0083] Spectrum analysis: Performing spectrum analysis on the data after FFT processing can obtain the spectrum diagram of voltage and current. The spectrum diagram shows the various frequency components contained in the voltage and current, including harmonic components.

[0084] Determine harmonic frequency: Determine the frequency range of harmonics based on the spectrum. Harmonics are usually integer multiples of the fundamental frequency (the standard frequency of the power grid). For example, in a 50Hz power grid, the frequency of the second harmonic is 100Hz, the frequency of the third harmonic is 150Hz, and so on.

[0085] Harmonic content assessment: For a certain harmonic frequency range, the level of harmonic content is assessed. Indicators such as total harmonic current distortion (THDi) and total harmonic voltage distortion (THDv) can be calculated to assess the impact of harmonics on the power grid.

[0086] Set filter cutoff frequency: Set the filter cutoff frequency according to the harmonic frequency range and actual situation. The filter cutoff frequency should be reasonably selected to filter out the harmonic components while avoiding filtering out the normal fundamental frequency.

[0087] S3, correcting the harmonic frequency obtained in the harmonic model;

[0088] In the embodiment of the present application, the specific steps of correcting the harmonic frequency obtained in the harmonic model include:

[0089] Define the fluctuation level of the power grid frequency, which is determined based on the power grid frequency monitoring data;

[0090] Determine the first influencing factor according to the design of the inverter and the control strategy, and the first influencing factor is used to characterize the influence of the inverter's own characteristics on the harmonics;

[0091] The second influencing factor is determined according to the load type and capacity output by the inverter, and the second influencing factor is used to characterize the influence of the load on the harmonics;

[0092] The harmonic frequency is corrected based on the fluctuation level, the first impact factor and the second impact factor.

[0093] It should be noted that the fluctuation level, the first influencing factor and the second influencing factor all correspond to a correction coefficient, which is the correction process. In the process of determining the harmonic frequency range, there are some influencing factors that may cause errors. These factors include:

[0094] Grid frequency: Grid frequency is the basis of harmonic frequency. In a 50Hz grid, the harmonic frequency is usually an integer multiple of the fundamental frequency (50Hz). If the grid frequency fluctuates or is unstable, it may cause a certain error in the calculation of the harmonic frequency.

[0095] Inverter design: Inverters of different types and brands may have different harmonic characteristics. The output waveform of the inverter may be affected by its design and control strategy, which may cause the actual harmonic frequency to differ from the theoretical frequency.

[0096] Inverter load: The inverter output load type and capacity may also have an impact on the harmonic frequency. Different types of loads (such as linear loads and non-linear loads) may introduce different harmonic components.

[0097] S4, setting target control parameters of the filter based on the harmonic information and performing filtering;

[0098] In an embodiment of the present application, the target control parameters of the filter are set based on the harmonic information, including:

[0099] Harmonic information includes harmonic frequency and content, and target control parameters include filter cutoff frequency, filter order and impedance;

[0100] Determine the filter cutoff frequency according to the range of harmonic frequencies;

[0101] Determine the filter order based on the content and harmonic components;

[0102] The impedance is determined based on the inverter output impedance and the grid impedance.

[0103] It should be noted that adjusting filter parameters is a common method for harmonic control in photovoltaic power station inverters. The filter is used to filter out the harmonic components in the inverter output, making the output waveform closer to the ideal sine wave. Adjusting the filter parameters involves the following main parameters and will have different effects on harmonics:

[0104] Cutoff frequency: The filter's cutoff frequency determines the frequency range of harmonics it can filter out. A lower cutoff frequency can filter out low-frequency harmonics, while a higher cutoff frequency can filter out high-frequency harmonics. Adjusting the cutoff frequency affects the effect and filtering ability of the harmonic filter.

[0105] Types of harmonic filters: There are different types of harmonic filters, including harmonic neutralization inverter (HNI), harmonic filter, etc. Different types of filters have different performance and application range in filtering harmonics.

[0106] Harmonic filter order: The order of the filter indicates the complexity of its filtering effect. A higher order filter can filter out more harmonic components, but it will also increase the complexity and cost of the filter.

[0107] Impedance: The impedance of the harmonic filter affects the filtering effect. The impedance of the filter needs to match the characteristics of the inverter output and the grid to obtain the best filtering effect.

[0108] Adjustments to filter parameters that affect harmonics may include the following:

[0109] Filtering effect: Adjusting the filter parameters can enhance or weaken the filter's ability to filter harmonics. Appropriate adjustment can achieve the expected effect of harmonic control.

[0110] Inverter efficiency: Higher order harmonic filters may result in lower inverter efficiency because the filter absorbs some of the power.

[0111] System stability: The filtering characteristics of the filter may affect the dynamic response between the inverter and the grid, and the stability and reliability of the system need to be ensured.

[0112] Cost: High-order or complex types of harmonic filters are usually more expensive. It is necessary to consider the filter cost and performance comprehensively while meeting the harmonic control requirements.

[0113] S5, at the same time, define the filtering effect and set the adjustment cycle of monitoring the filtering process;

[0114] In the embodiment of the present application, the definition of filtering effect includes:

[0115] Reduce harmonic content and grid distortion;

[0116] Comply with grid standard indicators, improve power quality indicators, and equipment protection effect indicators.

[0117] It should be noted that the objectives of harmonic control of photovoltaic power station inverters include:

[0118] Reduce harmonics: Through appropriate control strategies and filter design, the harmonic content in the inverter output can be reduced so that the harmonic components of current and voltage are reduced to a lower level.

[0119] Reduce grid distortion: Reducing harmonics in the inverter output can reduce the distortion of the grid voltage waveform and ensure the stability and reliability of the grid.

[0120] Compliance with grid standards: The harmonic content of the inverter output needs to comply with grid standards and specifications. These standards usually specify limits on the harmonic content in the inverter output to protect the normal operation of the grid and other user equipment.

[0121] Improve power quality: Control the inverter output waveform to be close to the ideal sine wave, which can improve the quality of power, reduce the power factor, and reduce the power loss caused by harmonics.

[0122] Protect other equipment: Reducing harmonics can reduce the impact of harmonics on other equipment, such as reducing the risk of harmonics damaging transformers, capacitors, inductors and other equipment.

[0123] The filtering effect of the filter is comprehensively defined from the above aspects.

[0124] It should also be noted that setting the adjustment period of the monitoring filtering process involves a balance between filter performance and system response. The adjustment period refers to the response time of the control system to input changes, which can also be understood as the time interval of sampling in the control system. In filter control, a suitable adjustment period can ensure that the filter effectively filters out harmonics in a real-time environment while minimizing unnecessary delays and computational complexity.

[0125] S6, adjusting the target control parameters of the next adjustment cycle according to the filtering effect of the previous adjustment cycle;

[0126] In an embodiment of the present application, adjusting the target control parameter of the next adjustment cycle according to the filtering effect of the previous adjustment cycle includes:

[0127] If the filtering effect of the previous adjustment cycle is lower than the filtering effect threshold corresponding to this cycle, a correction coefficient is determined according to the difference between the filtering effect of the previous adjustment cycle and the filtering effect threshold to adjust the target control parameter of the next adjustment cycle;

[0128] Otherwise, the target control parameter of the next regulation cycle is not adjusted.

[0129] It should be noted that, by applying the above technical solution, harmonic analysis is performed on the output of the power grid and the inverter, and a harmonic model of the power grid and the inverter output is established; harmonic information is determined according to the harmonic model; the target control parameters of the filter are set based on the harmonic information, and filtering is performed; at the same time, the filtering effect is defined, and the adjustment cycle for monitoring the filtering process is set; the target control parameters of the next adjustment cycle are adjusted according to the filtering effect of the previous adjustment cycle. The accuracy and adaptability of harmonic control are improved.

[0130] This embodiment also provides a computer device, which is applicable to the case of the photovoltaic power station inverter harmonic control method, including a memory and a processor; the memory is used to store computer executable instructions, and the processor is used to execute the computer executable instructions to implement the photovoltaic power station inverter harmonic control method proposed in the above embodiment.

[0131] The computer device may be a terminal, and the computer device includes a processor, a memory, a communication interface, a display screen and an input device connected via a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The communication interface of the computer device is used to communicate with an external terminal in a wired or wireless manner, and the wireless manner can be achieved through WIFI, an operator network, NFC (near field communication) or other technologies. The display screen of the computer device may be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device may be a touch layer covering the display screen, or a key, trackball or touchpad provided on the housing of the computer device, or an external keyboard, touchpad or mouse, etc.

[0132] This embodiment further provides a storage medium on which a computer program is stored. When the program is executed by a processor, the method for controlling harmonics of a photovoltaic power station inverter proposed in the above embodiment is implemented.

[0133] In summary, the photovoltaic power station inverter harmonic control method provided by the present invention performs harmonic analysis on the output of the power grid and the inverter, and establishes a harmonic model of the power grid and the inverter output, thereby realizing accurate analysis and modeling of harmonic characteristics, and providing a reliable data basis for subsequent harmonic control; by determining harmonic information according to the harmonic model, and correcting the harmonic frequency obtained in the harmonic model, the accuracy of harmonic frequency determination is improved, and multiple factors such as power grid fluctuations, inverter characteristics and load influence are taken into account at the same time, thereby enhancing the adaptability of the system; by setting the target control parameters of the filter based on the harmonic information and filtering, accurate control of harmonics is achieved, the adverse effects of harmonics on the power grid are reduced, the power quality is improved, and the system loss is reduced; by defining the filtering effect and setting the adjustment cycle for monitoring the filtering process, and adjusting the target control parameters of the next adjustment cycle according to the filtering effect of the previous adjustment cycle, the system has adaptive adjustment capability, which ensures the continuous optimization of harmonic control and the stable operation of the system. The present invention has achieved better results in terms of harmonic control accuracy, system adaptability and operation stability.

[0134] Example 2

[0135] This is the second embodiment of the present invention. This embodiment provides a method for controlling harmonics of a photovoltaic power station inverter. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0136] This embodiment is tested in a 10MW photovoltaic power station. The power station uses 20 500kW three-phase grid-connected inverters, and the nominal frequency of the grid is 50Hz. The experiment is carried out under standard conditions (25℃, 1000W / m 2 ) and changing working conditions (cloud occlusion causes light intensity fluctuations).

[0137] First, the PR2100 high-precision power quality analyzer is used to monitor the power grid and inverter output. The sampling frequency is set to 25.6kHz to ensure that harmonic components below 2kHz can be captured. The collected waveform data is preprocessed using a Butterworth low-pass filter with a cutoff frequency of 5kHz to filter out high-frequency noise. The preprocessed data is then windowed using the Hanning window function with a window length of 1024 points and an overlap rate of 50% to reduce spectrum leakage.

[0138] The processed data was subjected to fast Fourier transform (FFT) to obtain the spectrum diagram. Through spectrum analysis, it was found that the main harmonic components were concentrated on the 3rd, 5th, 7th, and 11th harmonics of the fundamental frequency. According to the measured grid frequency fluctuation, the fluctuation level was divided into three levels: Class A (±0.1Hz), Class B (±0.2Hz), and Class C (±0.3Hz). Combined with the inverter SPWM control strategy and switching frequency (4kHz), the first influencing factor K1=0.95 was determined. According to the actual load conditions (80% is inductive load and 20% is resistive load), the second influencing factor K2=0.92 was determined.

[0139] Based on the above three parameters, the harmonic frequency is corrected. The corrected filter parameters are as follows: the cutoff frequency is 350Hz (taking into account the main harmonic components), the filter adopts the 5th order Butterworth type, and the input impedance matching is 50Ω. The adjustment cycle is set to 5 minutes, and the filter effect threshold is 95%.

[0140] During the 24-hour continuous test, the performance data of the traditional fixed parameter filtering method (Scheme A), the simple adaptive method (Scheme B) and the method of the present invention (Scheme C) were recorded respectively, and the results are as follows:

[0141]

[0142] Through the analysis of the above experimental data, the method of the present invention (Scheme C) has significant advantages over the traditional method (Scheme A) and the simple adaptive method (Scheme B):

[0143] In terms of total harmonic distortion (THD): the THD of Scheme C under standard working conditions is only 2.1%, which is 44.7% lower than 3.8% of Scheme A and 34.4% lower than 3.2% of Scheme B; the advantage under variable working conditions is more obvious, with THD of 2.8%, which is 46.2% lower and 37.8% lower than 5.2% of Scheme A and 4.5% of Scheme B, respectively. This shows that the harmonic control effect of the present invention is better and can effectively suppress each harmonic.

[0144] In terms of response time: the response time of Solution C is significantly shortened, and it only takes 85ms to complete the adjustment under standard conditions, which is 95ms faster than Solution A (52.8% improvement) and 65ms faster than Solution B (43.3% improvement). This fast response feature is particularly important when the light intensity changes rapidly, and can better adapt to the fluctuating characteristics of photovoltaic power generation.

[0145] In terms of control accuracy: Scheme C achieves a high control accuracy of 97.8% (standard working condition) and 95.6% (variable working condition), which is 5.3 and 5.8 percentage points higher than Scheme A, and 3.7 and 4.4 percentage points higher than Scheme B. This shows that the present invention achieves more accurate harmonic control by considering the grid fluctuation level, inverter characteristics and load influence.

[0146] In terms of system stability and energy efficiency: Solution C has reached the industry's leading level in both indicators. The system stability reaches 98.2% (standard working conditions) and 96.8% (variable working conditions), and the energy efficiency reaches 97.9% (standard working conditions) and 97.2% (variable working conditions), which are better than existing technical solutions. High stability means that the system can operate reliably for a long time, and high energy efficiency means less energy loss.

[0147] It is particularly noteworthy that under variable working conditions, the attenuation of various indicators of Scheme C relative to standard working conditions is significantly smaller than that of the other two schemes. For example, the increase in THD is only 0.7 percentage points, while Schemes A and B increase by 1.4 and 1.3 percentage points respectively. This fully proves that the present invention has a stronger adaptability in dealing with the volatility unique to photovoltaic power generation.

[0148] Experimental results show that the present invention has achieved significant improvements in key indicators such as harmonic suppression effect, system response speed, and control accuracy through innovative methods such as establishing an accurate harmonic model, real-time correction of harmonic frequency, and dynamic adjustment of control parameters, providing better technical support for the grid-connected operation of photovoltaic power stations.

[0149] Example 3

[0150] Reference Figure 2, which is the third embodiment of the present invention, and which provides a photovoltaic power station inverter harmonic control system, comprising:

[0151] Harmonic analysis module 201, harmonic information module 202, harmonic correction module 203, filter control module 204, effect definition module 205 and parameter adjustment module 206;

[0152] The harmonic analysis module 201 is used to perform harmonic analysis on the output of the power grid and the inverter, and to establish a harmonic model of the output of the power grid and the inverter;

[0153] The harmonic information module 202 is used to determine the harmonic information according to the harmonic model;

[0154] The harmonic correction module 203 is used to correct the harmonic frequency obtained in the harmonic model;

[0155] The filter control module 204 is used to set the target control parameters of the filter based on the harmonic information and perform filtering;

[0156] The effect definition module 205 is used to define the filtering effect and set the adjustment cycle of the monitoring filtering process;

[0157] The parameter adjustment module 206 is used to adjust the target control parameters of the next adjustment cycle according to the filtering effect of the previous adjustment cycle.

[0158] Furthermore, the harmonic analysis module 201 is used to:

[0159] Collect voltage and current waveform data output by the power grid and inverter;

[0160] Perform data filtering, noise removal and spurious processing on voltage and current waveform data;

[0161] Perform fast Fourier transform on the voltage and current waveform data to convert the time domain data into frequency domain data;

[0162] Perform spectrum analysis on the frequency domain data to obtain the spectrum diagram of voltage and current, so as to establish the harmonic model of the power grid and inverter output.

[0163] Furthermore, the harmonic correction module 203 is used to:

[0164] Define the fluctuation level of the power grid frequency;

[0165] Determine the first influencing factor according to the design of the inverter and the control strategy;

[0166] Determine the second influencing factor according to the load type and capacity output by the inverter;

[0167] The harmonic frequency is corrected based on the fluctuation level, the first impact factor and the second impact factor.

[0168] Furthermore, the filtering control module 204 is used to:

[0169] Harmonic information includes harmonic frequency and content, and target control parameters include filter cutoff frequency, filter order and impedance;

[0170] Determine the filter cutoff frequency according to the range of harmonic frequencies;

[0171] Determine the filter order based on the content and harmonic components;

[0172] The impedance is determined based on the inverter output impedance and the grid impedance.

[0173] Furthermore, the parameter adjustment module 206 is used to:

[0174] If the filtering effect of the previous adjustment cycle is lower than the filtering effect threshold corresponding to this cycle, a correction coefficient is determined according to the difference between the filtering effect of the previous adjustment cycle and the filtering effect threshold to adjust the target control parameter of the next adjustment cycle;

[0175] Otherwise, the target control parameter of the next regulation cycle is not adjusted.

[0176] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for controlling harmonics of a photovoltaic power station inverter, characterized in that: include, Conduct harmonic analysis on the output of the power grid and inverter, and establish harmonic models of the power grid and inverter output; determining harmonic information according to a harmonic model; Correcting the harmonic frequency obtained in the harmonic model; The target control parameters of the filter are set based on the harmonic information, and filtering is performed; At the same time, define the filtering effect and set the adjustment cycle for monitoring the filtering process; The target control parameters of the next regulation cycle are adjusted according to the filtering effect of the previous regulation cycle.

2. The photovoltaic power station inverter harmonic control method according to claim 1, characterized in that: The harmonic model of the power grid and the inverter output is established, including: Collect voltage and current waveform data output by the power grid and inverter; Perform data filtering, noise removal and spurious processing on voltage and current waveform data; Perform fast Fourier transform on the voltage and current waveform data to convert the time domain data into frequency domain data; Perform spectrum analysis on the frequency domain data to obtain the spectrum diagram of voltage and current, so as to establish the harmonic model of the power grid and inverter output.

3. The photovoltaic power station inverter harmonic control method according to claim 2, characterized in that: The specific steps of correcting the harmonic frequency obtained in the harmonic model include: defining a fluctuation level of the power grid frequency, wherein the fluctuation level is determined according to power grid frequency monitoring data; Determine a first influencing factor according to the design of the inverter and the control strategy, wherein the first influencing factor is used to characterize the influence of the inverter's own characteristics on the harmonics; Determining a second impact factor according to the load type and capacity output by the inverter, wherein the second impact factor is used to characterize the impact of the load on the harmonics; The harmonic frequency is corrected based on the fluctuation level, the first impact factor and the second impact factor.

4. The photovoltaic power station inverter harmonic control method according to claim 3, characterized in that: The step of setting the target control parameters of the filter based on the harmonic information includes: Harmonic information includes harmonic frequency and content, and target control parameters include filter cutoff frequency, filter order and impedance; Determine the filter cutoff frequency according to the range of harmonic frequencies; Determine the filter order based on the content and harmonic components; The impedance is determined based on the inverter output impedance and the grid impedance.

5. The photovoltaic power station inverter harmonic control method according to claim 4, characterized in that: The step of adjusting the target control parameter of the next adjustment cycle according to the filtering effect of the previous adjustment cycle includes: If the filtering effect of the previous adjustment cycle is lower than the filtering effect threshold corresponding to this cycle, a correction coefficient is determined according to the difference between the filtering effect of the previous adjustment cycle and the filtering effect threshold to adjust the target control parameter of the next adjustment cycle; Otherwise, the target control parameter of the next regulation cycle is not adjusted.

6. The photovoltaic power station inverter harmonic control method according to claim 5, characterized in that: The determination of the harmonic information includes: Collect voltage and current waveform data of the power grid and inverter output through harmonic monitoring equipment; Performing fast Fourier transform on the collected data to obtain frequency domain data; Perform spectrum analysis on frequency domain data to determine the harmonic frequency range and content.

7. The photovoltaic power station inverter harmonic control method according to claim 6, characterized in that: The definition of the filtering effect includes: Reduce harmonic content and grid distortion; Comply with grid standard indicators, improve power quality indicators, and equipment protection effect indicators.

8. A photovoltaic power station inverter harmonic control system, based on the photovoltaic power station inverter harmonic control method according to any one of claims 1 to 7, characterized in that: It also includes a harmonic analysis module, a harmonic information module, a harmonic correction module, a filtering control module, an effect definition module and a parameter adjustment module; The harmonic analysis module is used to perform harmonic analysis on the output of the power grid and the inverter, and to establish a harmonic model of the output of the power grid and the inverter; The harmonic information module is used to determine the harmonic information according to the harmonic model; The harmonic correction module is used to correct the harmonic frequency obtained in the harmonic model; The filtering control module is used to set the target control parameters of the filter based on the harmonic information and perform filtering; The effect definition module is used to define the filtering effect and set the adjustment cycle of the monitoring filtering process; The parameter adjustment module is used to adjust the target control parameters of the next adjustment cycle according to the filtering effect of the previous adjustment cycle.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the photovoltaic power station inverter harmonic control method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the photovoltaic power station inverter harmonic control method according to any one of claims 1 to 7 are implemented.

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