New energy ratio method and system under harmonic and stability margin constraints

Abstract

This invention belongs to the field of power system technology and provides a method and system for allocating capacity to grid-connected renewable energy sources under harmonic and stability margin constraints. It obtains impedance models of grid-connected and grid-connected converters, calculates the equivalent impedance of renewable energy power plants, estimates the equivalent impedance of transmission lines, and combines the two impedances to obtain a stability margin evaluation index. It also obtains the coupled harmonic admittance matrices of the grid-connected and grid-connected converters, calculates the coupled harmonic admittance matrices, and calculates a harmonic emission level evaluation index based on the harmonic distortion level at the grid connection point. The stability margin evaluation index and the harmonic emission level evaluation index are used as comprehensive evaluation indices. The allocation range of grid-connected converters is constrained, and within this constrained range, the comprehensive evaluation index for each capacity allocation is calculated. The capacity allocation is determined based on the optimal result of the comprehensive evaluation index. This invention achieves overall optimality of power plant stability margin and grid-connected power quality.

Description

Technical Field

[0001] This invention belongs to the field of power system technology, specifically relating to a method and system for allocating renewable energy in a grid-connected system under harmonic and stability margin constraints. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Based on the differences in control structure and grid-connection synchronization methods, the control modes of renewable energy grid-connected converters can be divided into two categories: grid-following (GFL) and grid-forming (GFM). The stability of GFL / GFM converters exhibits a dual characteristic under different grid strengths: under strong grids, GFL converters show better stability, while GFM converters are at risk of instability; conversely, under weak grids, the opposite is true. In the past, when the penetration rate of renewable energy in the power system was low and the grid strength was high, GFL converters were mainly used in renewable energy power plants. However, with the large-scale grid connection of wind turbines and photovoltaics, the proportion of synchronous generators has decreased, and the grid strength has gradually weakened. Therefore, a certain proportion of GFM converters need to be configured in power plants to ensure stable system operation.

[0004] Currently, research on capacity allocation methods for heterogeneous converters in renewable energy power plants mainly focuses on stability. This involves obtaining the equivalent impedance model of the power plant based on small-signal modeling, and then using eigenvalue loci to obtain the capacity allocation boundary that meets the system stability requirements under different grid intensities. The inventors have discovered significant differences in the harmonic emission characteristics of heterogeneous / heterogeneous converters. Compared to GFL converters, GFM converters have lower harmonic emission levels under distorted grid conditions. Therefore, increasing the proportion of GFM converters in renewable energy power plants can improve power quality under distorted grid conditions. However, current research lacks a capacity allocation method that balances stability margin and grid-connected power quality. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a method and system for allocating renewable energy to a grid-connected system under harmonic and stability margin constraints. This invention achieves the overall optimization of power station stability margin and grid-connected power quality.

[0006] According to some embodiments, the present invention adopts the following technical solution:

[0007] A method for allocating renewable energy in a grid-connected system under harmonic and stability margin constraints includes the following steps:

[0008] Impedance models of grid-connected and grid-connected converters are obtained through small-signal modeling and state-space equations. The equivalent impedance of new energy power plants is calculated. The equivalent impedance of transmission lines is estimated by the distance between the new energy power plant and the upper-level power grid. The stability margin assessment index of new energy power plants is obtained by combining the two impedances.

[0009] The coupling harmonic admittance matrix of grid-connected converter and grid-connected converter is obtained by mechanism modeling. The coupling harmonic admittance matrix of new energy power station is calculated. Combined with the harmonic distortion level at the grid connection point, the harmonic emission level evaluation index of new energy power station is calculated.

[0010] The stability margin assessment index and harmonic emission level assessment index of new energy power stations are used as comprehensive assessment indicators.

[0011] Considering the stability margin and the minimum guarantee requirements for harmonic emission levels, the range of grid-connected converter ratios is constrained. Within the constrained range of grid-connected converters, the comprehensive evaluation index for each capacity ratio is calculated, and the capacity ratio is determined based on the optimal result of the comprehensive evaluation index.

[0012] As an alternative implementation, the process of obtaining the impedance models of the grid-type converter and the grid-type converter through small-signal modeling and state-space equations includes: obtaining the state matrix A, input matrix B and output matrix C of the grid-type converter and the grid-type converter respectively through small-signal modeling and state-space equations.

[0013] The output impedance of grid-connected converters and grid-connected converters are calculated separately. Converters of the same type are treated as single-unit equivalents. The equivalent impedance of the new energy power station is obtained by multiplying the number of each type of converter.

[0014] The process of calculating the output impedance of grid-connected converters and network-type converters includes:

[0015] ;

[0016] Z conv This indicates the output impedance of the corresponding converter. s Let A, B, and C represent complex variables, respectively, and let I be the identity matrix of the strain gauge.

[0017] The calculation process for the equivalent impedance of a new energy power station is as follows:

[0018] ;

[0019] In the formula, a This refers to the total number of converters in the new energy power station. a 1 represents the number of grid-connected converters in the power station. Zsta The equivalent impedance for new energy power plants. Z GFL and Z GFM These represent the output impedances of the grid-type converter and the network-type converter, respectively.

[0020] As an alternative implementation method, the process of estimating the equivalent impedance of transmission lines based on the distance between the renewable energy power station and the upstream power grid includes: obtaining the length of the transmission line between the upstream power grid and the renewable energy power station. Then, the equivalent impedance of the transmission line is calculated by combining the transmission line parameters. Z grid for:

[0021] ;

[0022] in, Z grid This is the equivalent impedance of the transmission line. R i and L i These are the equivalent resistance and equivalent inductance per unit length of the transmission line, respectively, and ω is the angular velocity corresponding to the grid frequency.

[0023] As an alternative implementation method, the process of obtaining the stability margin assessment index of a new energy power station by combining two impedances includes: combining the equivalent impedance of the new energy power station and the equivalent impedance of the transmission line, at a frequency of f Phase acquisition of new energy power station stability margin assessment indicators at point 1 γ sta :

[0024] ;

[0025] in, γ sta For new energy field The station's stability margin evaluation indicators f 1 represents the equivalent impedance of the new energy power station. Z sta Equivalent impedance of transmission lines Z grid The frequencies corresponding to equal amplitudes φ f，grid and φ f，sta These represent the equivalent impedances of the transmission lines. Z grid Equivalent impedance of new energy power stations Z sta At frequency f Phase at 1, φ It is a constant, and is selected according to the stability requirements of the actual project.

[0026] As an alternative implementation method, the process of obtaining the coupling harmonic admittance matrix of grid-connected and grid-connected converters through mechanism modeling, calculating the coupling harmonic admittance matrix of the new energy power station, and combining it with the harmonic distortion level at the grid connection point to calculate the harmonic emission level evaluation index of the new energy power station includes:

[0027] First, the coupling harmonic admittance matrices of the grid-type converter and the mesh-type converter are calculated using the harmonic state-space equations:

[0028] ;

[0029] In the formula, Y is the harmonic admittance of the strain gauge, and Δ I and Δ V These represent the changes in current and voltage at different frequencies, with the subscript x indicating the harmonic order and H being the maximum harmonic order being analyzed.

[0030] Calculate the coupled harmonic admittance matrix of the renewable energy power plant by combining the number of grid-connected converters and the number of grid-connected converters: , a This refers to the total number of converters in the new energy power station. a 1 represents the number of grid-connected converters in the power station. Y sta This represents the coupled harmonic admittance matrix of the new energy power station. Y GFL and Y GFM These represent the coupling harmonic admittance matrices of the grid-type converter and the grid-connected converter, respectively.

[0031] Voltage distortion level at the grid connection point of new energy power plants was obtained based on historical sampling data. V h Combining the coupled harmonic admittance matrix of the new energy power station with the voltage distortion level at the grid connection point V h Obtaining harmonic emission level assessment indicators H sta :

[0032] ;

[0033] In the formula, H sta Indicators representing the harmonic emission level assessment of new energy power plants. V h Let |||2| represent the voltage distortion level at the grid connection point of the new energy power station, where |||2| represents the second-order norm, and in this formula, |||2| represents the root mean square value of each element in the column vector.

[0034] As an alternative implementation method, the process of using the stability margin assessment index and harmonic emission level assessment index of new energy power plants as comprehensive assessment indicators includes: normalizing the stability margin assessment index of new energy power plants;

[0035] ;

[0036] γ sta，1 This represents the normalized stability margin assessment index for new energy power plants. a This refers to the number of converters in the power station. γ sta For new energy field The station's stability margin evaluation indicators It is a constant;

[0037] The harmonic emission level index of new energy power plants is normalized by subtracting the rated output current of the power plant from its harmonic emission level index, and then dividing by the rated output current of the power plant.

[0038] ;

[0039] In the formula, H sta,1 This represents the normalized harmonic emission level assessment index for new energy power plants. a This refers to the number of converters in the power station. I N This refers to the rated output current of a single converter. H sta Indicators representing the harmonic emission level assessment of new energy power plants;

[0040] The normalized stability margin assessment index and the harmonic emission level assessment index are multiplied together to obtain the comprehensive assessment index:

[0041] ;

[0042] In the formula, C sta This indicates the comprehensive evaluation indicators for new energy power stations.

[0043] As an alternative implementation method, the process of constraining the grid-connected converter ratio range considering the minimum guarantee requirements for stability margin and harmonic emission level includes: evaluating the given threshold by setting a stability margin assessment index for new energy power plants that is greater than a given threshold and a harmonic emission level evaluation index.

[0044] ;

[0045] In the formula, T γ and TH These represent the stability margin threshold and harmonic emission level threshold set for new energy power plants, respectively. γ sta For new energy field The station's stability margin evaluation indicators H sta Indicators representing the harmonic emission level assessment of new energy power plants;

[0046] The solution yields the following constraint range for grid-connected converter ratio, considering stability margin and grid power quality: ;

[0047] In the formula, The number of grid-connected converters in new energy power plants. and These represent the lower and upper limits of the number of grid-connected converters, respectively, considering stability margin and harmonic emission level constraints.

[0048] As an alternative implementation method, within the constrained range of grid-connected converters, the comprehensive evaluation index for each capacity ratio is calculated. The process of determining the capacity ratio based on the optimal result of the comprehensive evaluation index includes: within the constrained range of capacity ratios, calculating the comprehensive evaluation index value of the new energy power station under different capacity ratios, and selecting the number of grid-connected converters when the comprehensive evaluation index is at its maximum to guide the capacity ratio.

[0049] A grid-type renewable energy allocation system under harmonic and stability margin constraints includes:

[0050] Impedance models of grid-connected and grid-connected converters are obtained through small-signal modeling and state-space equations. The equivalent impedance of new energy power plants is calculated. The equivalent impedance of transmission lines is estimated by the distance between the new energy power plant and the upper-level power grid. The stability margin assessment index of new energy power plants is obtained by combining the two impedances.

[0051] The coupling harmonic admittance matrix of grid-connected converter and grid-connected converter is obtained by mechanism modeling. The coupling harmonic admittance matrix of new energy power station is calculated. Combined with the harmonic distortion level at the grid connection point, the harmonic emission level evaluation index of new energy power station is calculated.

[0052] The stability margin assessment index and harmonic emission level assessment index of new energy power stations are used as comprehensive assessment indicators.

[0053] Considering the stability margin and the minimum guarantee requirements for harmonic emission levels, the range of grid-connected converter ratios is constrained. Within the constrained range of grid-connected converters, the comprehensive evaluation index for each capacity ratio is calculated, and the capacity ratio is determined based on the optimal result of the comprehensive evaluation index.

[0054] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to perform the steps of the method described above.

[0055] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0056] This invention provides a method for matching the capacity of new energy power plants with grid-connected converters, which integrates harmonic emission levels and stability margins. This method achieves a balance between stable operation of new energy power plants and improvement of grid-connected power quality, and has strong adaptability and versatility in new power system scenarios with high proportions of new energy and high proportions of electricity.

[0057] This invention requires no additional passive components or complex parameter tuning. It proposes an evaluation index for the stability margin and grid-connected power quality of new energy power plants. Based on these two indices, the overall characteristics of the new energy power plant are comprehensively evaluated. Then, within the constraints of stability margin and power quality, the optimal ratio is obtained based on the comprehensive evaluation index, so as to achieve a balance between stable system operation and high-quality power supply.

[0058] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0059] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0060] Figure 1 This is a schematic diagram of a method for allocating renewable energy in a grid-type system under harmonic and stability margin constraints in one embodiment.

[0061] Figure 2 This is a schematic diagram illustrating the calculation process of evaluation indicators in one embodiment;

[0062] Figure 3 This is a schematic diagram illustrating the process for determining the proportion of renewable energy in a grid-type embodiment.

[0063] Figure 4 This is a schematic diagram of the structure of a new energy power station in one embodiment. Detailed Implementation

[0064] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0065] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0066] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0067] Where there is no conflict, the embodiments and features described in this application may be combined with each other.

[0068] Example 1

[0069] A method for allocating renewable energy in a grid-connected system under harmonic and stability margin constraints, such as... Figure 1 As shown, it includes the following steps:

[0070] Impedance models of grid-connected and grid-connected converters are obtained through small-signal modeling and state-space equations. The equivalent impedance of new energy power plants is calculated. The equivalent impedance of transmission lines is estimated by the distance between the new energy power plant and the upper-level power grid. The stability margin assessment index of new energy power plants is obtained by combining the two impedances.

[0071] The coupling harmonic admittance matrix of grid-connected converter and grid-connected converter is obtained by mechanism modeling. The coupling harmonic admittance matrix of new energy power station is calculated. Combined with the harmonic distortion level at the grid connection point, the harmonic emission level evaluation index of new energy power station is calculated.

[0072] The stability margin assessment index and harmonic emission level assessment index of new energy power stations are used as comprehensive assessment indicators.

[0073] Considering the stability margin and the minimum guarantee requirements for harmonic emission levels, the range of grid-connected converter ratios is constrained. Within the constrained range of grid-connected converters, the comprehensive evaluation index for each capacity ratio is calculated, and the capacity ratio is determined based on the optimal result of the comprehensive evaluation index.

[0074] The following is a detailed introduction.

[0075] by Figure 4 Taking the new energy power station shown as an example, firstly, we need to construct evaluation indicators, such as... Figure 2 As shown, it consists of two parts.

[0076] The first part involves obtaining impedance models for GFL and GFM converters through mechanistic modeling, and then calculating the equivalent impedance of new energy power plants. Z sta By consulting relevant materials, the equivalent impedance between the new energy power station and the power grid was obtained. Z grid Furthermore, combined with Z sta and Z grid The assessment of the stability margin of new energy power plants is completed, and this step specifically includes:

[0077] (1) Obtain the state matrix A, input matrix B, and output matrix C of the root / grid converter through small-signal modeling and state-space equations, respectively. Then substitute them into equation (1) to calculate the output impedance of the GFL converter and the GFM converter, respectively. Z GFL and Z GFM .

[0078] (1)

[0079] In the formula, Z conv This indicates the output impedance of the converter. s Let A, B, and C represent complex variables. A, B, and C are the state matrix, input matrix, and output matrix of the converter, respectively. I is the identity matrix.

[0080] (2) Treating converters of the same type as single units for equivalent processing, and combining the number of GFL converters in the new energy power station, the equivalent impedance Z of the new energy power station is obtained by multiplication approximation. sta As shown in equation (2).

[0081] (2)

[0082] In the formula, a This refers to the total number of converters in the new energy power station. a 1 represents the number of GFL converters in the station. Z sta The equivalent impedance for new energy power plants. Z GFL and Z GFM These represent the output impedances of the GFL converter and the GFM converter, respectively.

[0083] (3) Obtain the length of the transmission line between the new energy power station and the upstream power grid by consulting relevant materials. l The information on inductance and resistance per unit length is used to calculate the equivalent impedance of the transmission line as shown in equation (3).

[0084] (3)

[0085] In the formula, Z grid This is the equivalent impedance of the transmission line. R i and L i These are the equivalent resistance and equivalent inductance per unit length of the transmission line, respectively, and ω is the angular velocity corresponding to the grid frequency.

[0086] (4) Drawing Z sta and Z grid The amplitude-frequency response curve and phase-frequency response curve, find the amplitude-frequency response curve. Z sta and Z grid Frequency corresponding to equal amplitude f 1. Obtain from the phase frequency response curve Z sta and Z grid At frequency f Phase at 1 φ f1，sta and φ f1，grid Then, substitute it into equation (4) to complete the assessment of the stability margin of the new energy power station.

[0087] (4)

[0088] In the formula, γ sta This serves as a stability margin assessment indicator for new energy power plants. φ It is a constant, selected based on the stability requirements of the actual project.

[0089] The second part involves obtaining the Coupling Harmonic Admittance Matrix (CHAM) of the GFL and GFM converters through mechanism modeling, and then calculating the CHAM of the new energy power plant; and obtaining the harmonic distortion level at the grid connection point based on historical sampling data. V h Furthermore, combining CHAM with new energy power stations V h Complete the assessment of harmonic emission levels at new energy power plants, specifically including:

[0090] (1) By constructing the harmonic state-space equation, the CHAM models of the GFL converter and the GFM converter are obtained by mechanism modeling as shown in the following equation.

[0091] (5)

[0092] In the formula, Y is the harmonic admittance of the converter, and Δ I and Δ V These represent the changes in current and voltage at different frequencies, respectively. The subscript x indicates the harmonic order, and H is the maximum harmonic order being analyzed.

[0093] (2) Treating converters of the same type as single units for equivalent processing, and combining the number of GFL converters in the new energy power station, the equivalent impedance of the new energy power station is obtained by multiplication approximation. Y sta As shown in equation (6).

[0094] (6)

[0095] In the formula, a This refers to the total number of converters in the new energy power station. a 1 represents the number of GFL converters in the station. Y sta CHAM for new energy power stations Y GFL and Y GFM CHAM represents GFL converter and GFM converter respectively.

[0096] (3) Obtain the voltage distortion level at the grid connection point of new energy power plants based on historical sampling data V h Combining CHAM with new energy power stations V h Complete the assessment of harmonic emission levels.

[0097] (7)

[0098] In the formula, H sta Indicators representing the harmonic emission level assessment of new energy power plants. V h Let |||2| represent the voltage distortion level at the grid connection point of the new energy power station, where |||2| represents the second-order norm, and in this formula, |||2| represents the root mean square value of each element in the column vector.

[0099] like Figure 3 As shown above, a comprehensive evaluation of the stability and grid-connected power quality indicators of new energy power plants is completed. While ensuring the necessary stability margin and harmonic emission level, the overall optimal capacity ratio is obtained.

[0100] Includes the following steps:

[0101] Based on the stability margin assessment index and harmonic emission level assessment index of new energy power stations, a quantitative assessment of the overall performance of new energy power stations was completed.

[0102] Based on actual engineering requirements, limits are set for stability and harmonic emission levels to determine the GFL converter configuration constraint range. Within this constraint range, comprehensive evaluation indicators are calculated for each configuration ratio. C sta The results with the optimal indicators are selected for the optimization of the capacity allocation of new energy power stations.

[0103] In some embodiments, the steps for quantitatively evaluating the overall performance of a new energy power station based on the stability margin assessment index and harmonic emission level assessment index include:

[0104] (1) The stability margin assessment index of new energy power stations is normalized as shown in equation (8).

[0105] (8)

[0106] In the formula, γ sta，1 This represents the normalized stability margin assessment index for new energy power plants. a This refers to the number of converters in the power station. This is a constant, selected based on the stability requirements of the actual engineering project. This parameter is a constant used to calculate the stability margin and can be 180, 170, or 160, depending on the engineering requirements. The higher the stability margin requirement of the actual system, the smaller this value should be.

[0107] (2) By subtracting the rated output current of the new energy power station from its harmonic emission level index and then dividing by the rated output current of the new energy power station, the normalization of the harmonic emission level index is completed as shown in equation (9).

[0108] (9)

[0109] In the formula, H sta,1 This represents the normalized harmonic emission level assessment index for new energy power plants. a This refers to the number of converters in the power station. I N This is the rated output current of a single converter.

[0110] (3) Multiply the normalized stability margin assessment index and the harmonic emission level assessment index to obtain the comprehensive assessment index as shown in Equation (10).

[0111] (10)

[0112] In the formula, C sta This indicates the comprehensive evaluation indicators for new energy power stations.

[0113] Based on actual engineering needs, the steps to obtain the GFL converter matching ratio constraint range include setting limits on stability indicators and harmonic emission level indicators:

[0114] (1) Based on the actual engineering requirements, the stability margin threshold and harmonic emission level threshold of the new energy power station are set as shown in Equation (11), and then the GFL converter ratio constraint range considering the stability margin and power grid power quality is obtained as shown in Equation (12).

[0115] (11)

[0116] In the formula, T γ and T H These represent the stability margin threshold and harmonic emission level threshold set for new energy power plants, respectively.

[0117] (12)

[0118] In the formula, a 1 represents the number of GFL converters in the new energy power station. a 1，min and a 1，max These represent the lower and upper limits of the number of GFL converters considering stability margin and harmonic emission level constraints, respectively.

[0119] (2) Within the constrained capacity ratio range, calculate the comprehensive index quantification value of the new energy power station under different capacity ratios using equation (10), and select the number of GFL converters when the comprehensive index value is the largest. a 1. Used to guide capacity ratio.

[0120] Example 2

[0121] A grid-type renewable energy allocation system under harmonic and stability margin constraints includes:

[0122] Impedance models of grid-connected and grid-connected converters are obtained through small-signal modeling and state-space equations. The equivalent impedance of new energy power plants is calculated. The equivalent impedance of transmission lines is estimated by the distance between the new energy power plant and the upper-level power grid. The stability margin assessment index of new energy power plants is obtained by combining the two impedances.

[0123] The coupling harmonic admittance matrix of grid-connected converter and grid-connected converter is obtained by mechanism modeling. The coupling harmonic admittance matrix of new energy power station is calculated. Combined with the harmonic distortion level at the grid connection point, the harmonic emission level evaluation index of new energy power station is calculated.

[0124] The stability margin assessment index and harmonic emission level assessment index of new energy power stations are used as comprehensive assessment indicators.

[0125] Considering the stability margin and the minimum guarantee requirements for harmonic emission levels, the range of grid-connected converter ratios is constrained. Within the constrained range of grid-connected converters, the comprehensive evaluation index for each capacity ratio is calculated, and the capacity ratio is determined based on the optimal result of the comprehensive evaluation index.

[0126] Example 3

[0127] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps of the method provided in Embodiment 1.

[0128] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of one or more computer-usable storage media (including, but not limited to, disk storage, etc.) containing computer-usable program code. CD - ROM It takes the form of a computer program product implemented on (such as optical memory, etc.).

[0129] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0130] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0131] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0132] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art without creative effort within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for allocating renewable energy in a grid-type system under harmonic and stability margin constraints, characterized in that... Includes the following steps: Impedance models of grid-connected and grid-connected converters are obtained through small-signal modeling and state-space equations. The equivalent impedance of new energy power plants is calculated. The equivalent impedance of transmission lines is estimated by the distance between the new energy power plant and the upper-level power grid. The stability margin assessment index of new energy power plants is obtained by combining the two impedances. The coupling harmonic admittance matrix of grid-connected converter and grid-connected converter is obtained by mechanism modeling. The coupling harmonic admittance matrix of new energy power station is calculated. Combined with the harmonic distortion level at the grid connection point, the harmonic emission level evaluation index of new energy power station is calculated. The stability margin assessment index and harmonic emission level assessment index of new energy power stations are used as comprehensive assessment indicators. Considering the stability margin and the minimum guarantee requirements for harmonic emission levels, the range of grid-connected converter ratios is constrained. Within the constrained range of grid-connected converters, the comprehensive evaluation index for each capacity ratio is calculated, and the capacity ratio is determined based on the optimal result of the comprehensive evaluation index. The process of obtaining the stability margin assessment index for new energy power plants by combining two impedances includes: combining the equivalent impedance of the new energy power plant and the equivalent impedance of the transmission line, at a frequency of f Phase acquisition of new energy power station stability margin assessment indicators at point 1 γ sta : ； in, γ sta For new energy field The station's stability margin evaluation indicators f 1 represents the equivalent impedance of the new energy power station. Z sta Equivalent impedance of transmission lines Z grid The frequencies corresponding to equal amplitudes φ f，grid and φ f，sta These represent the equivalent impedances of the transmission lines. Z grid Equivalent impedance of new energy power stations Z sta At frequency f Phase at 1, φ It is a constant, selected based on the stability requirements of the actual engineering project; The process of obtaining the coupling harmonic admittance matrices of grid-connected and grid-connected converters through mechanism modeling, calculating the coupling harmonic admittance matrix of the new energy power station, and combining it with the harmonic distortion level at the grid connection point to calculate the harmonic emission level assessment index of the new energy power station includes: The coupling harmonic admittance matrices of the grid-connected converter and the grid-type converter are calculated using the harmonic state-space equations as follows: In the formula, Y is the harmonic admittance of the strain gauge, and Δ I and Δ V These represent the changes in current and voltage at different frequencies, with the subscript x indicating the harmonic order and H being the maximum harmonic order being analyzed. Calculate the coupled harmonic admittance matrix of the renewable energy power plant by combining the number of grid-connected converters and the number of grid-connected converters: , a This refers to the total number of converters in the new energy power station. a 1 represents the number of grid-connected converters in the power station. Y sta This represents the coupled harmonic admittance matrix of the new energy power station. Y GFL and Y GFM These represent the coupling harmonic admittance matrices of the grid-type converter and the grid-connected converter, respectively. Voltage distortion level at the grid connection point of new energy power plants was obtained based on historical sampling data. V h Combining the coupled harmonic admittance matrix of the new energy power station with the voltage distortion level at the grid connection point V h Obtaining harmonic emission level assessment indicators H sta : ； In the formula, H sta Indicators representing the harmonic emission level assessment of new energy power plants. V h Let |||2| represent the voltage distortion level at the grid connection point of the new energy power station, where |||2| represents the second-order norm, and in this formula, |||2| represents the root mean square value of each element in the column vector.

2. The method for allocating renewable energy in a grid-type system under harmonic and stability margin constraints as described in claim 1, characterized in that, The process of obtaining the impedance models of the grid-type converter and the network-type converter through small-signal modeling and state-space equations includes: obtaining the state matrix A, input matrix B and output matrix C of the grid-type converter and the network-type converter respectively through small-signal modeling and state-space equations; The output impedance of grid-connected converters and grid-connected converters are calculated separately. Converters of the same type are treated as single-unit equivalents. The equivalent impedance of the new energy power station is obtained by multiplying the number of each type of converter. The process of calculating the output impedance of grid-connected converters and network-type converters includes: ； Z conv This indicates the output impedance of the corresponding converter. s Let A, B, and C represent complex variables, respectively, and let I be the identity matrix of the strain gauge. The calculation process for the equivalent impedance of a new energy power station is as follows: ； In the formula, a This refers to the total number of converters in the new energy power station. a 1 represents the number of grid-connected converters in the power station. Z sta The equivalent impedance for new energy power plants. Z GFL and Z GFM These represent the output impedances of the grid-type converter and the network-type converter, respectively.

3. The method for allocating renewable energy in a grid-type system under harmonic and stability margin constraints as described in claim 1, characterized in that, The process of estimating the equivalent impedance of transmission lines based on the distance between renewable energy power plants and the upstream power grid includes: obtaining the length of the transmission line between the upstream power grid and the renewable energy power plant. Then, the equivalent impedance of the transmission line is calculated by combining the transmission line parameters. Z grid for: ； in, Z grid This is the equivalent impedance of the transmission line. R i and L i These are the equivalent resistance and equivalent inductance per unit length of the transmission line, respectively, and ω is the angular velocity corresponding to the grid frequency.

4. The method for allocating renewable energy in a grid-type system under harmonic and stability margin constraints as described in claim 1, characterized in that, The process of using the stability margin assessment index and harmonic emission level assessment index of new energy power plants as comprehensive assessment indicators includes: normalizing the stability margin assessment index of new energy power plants. ； γ sta，1 This represents the normalized stability margin assessment index for new energy power plants. γ sta For new energy field The station's stability margin evaluation indicators It is a constant; The harmonic emission level index of new energy power plants is normalized by subtracting the rated output current of the power plant from its harmonic emission level index, and then dividing by the rated output current of the power plant. ； In the formula, H sta,1 This represents the normalized harmonic emission level assessment index for new energy power plants. a This refers to the number of converters in the power station. I N This refers to the rated output current of a single converter. H sta Indicators representing the harmonic emission level assessment of new energy power plants; The normalized stability margin assessment index and the harmonic emission level assessment index are multiplied together to obtain the comprehensive assessment index: ； In the formula, C sta This indicates the comprehensive evaluation indicators for new energy power stations.

5. The method for allocating renewable energy in a grid-type system under harmonic and stability margin constraints as described in claim 1, characterized in that... The process of constraining the grid-connected converter ratio range considering the minimum guarantee requirements for stability margin and harmonic emission level includes: evaluating the given threshold by setting a stability margin assessment index for new energy power plants that is greater than a given threshold and a harmonic emission level evaluation index. ； In the formula, T γ and T H These represent the stability margin threshold and harmonic emission level threshold set for new energy power plants, respectively. γ sta For new energy field The station's stability margin evaluation indicators H sta Indicators representing the harmonic emission level assessment of new energy power plants; The solution yields the following constraint range for grid-connected converter ratio, considering stability margin and grid power quality: ; In the formula, The number of grid-connected converters in new energy power plants. and These represent the lower and upper limits of the number of grid-connected converters, respectively, considering stability margin and harmonic emission level constraints.

6. The method for allocating renewable energy in a grid-type system under harmonic and stability margin constraints as described in claim 1, characterized in that, Within the constrained range of grid-connected converters, the process of calculating the comprehensive evaluation index for each capacity ratio and determining the capacity ratio based on the optimal comprehensive evaluation index includes: within the constrained range of capacity ratios, calculating the comprehensive evaluation index values ​​for new energy power plants under different capacity ratios, and selecting the number of grid-connected converters with the maximum comprehensive evaluation index to guide the capacity ratio.

7. A grid-type renewable energy allocation system under harmonic and stability margin constraints, employing the method described in claim 1, characterized in that... include: Impedance models of grid-connected and grid-connected converters are obtained through small-signal modeling and state-space equations. The equivalent impedance of new energy power plants is calculated. The equivalent impedance of transmission lines is estimated by the distance between the new energy power plant and the upper-level power grid. The stability margin assessment index of new energy power plants is obtained by combining the two impedances. The coupling harmonic admittance matrix of grid-connected converter and grid-connected converter is obtained by mechanism modeling. The coupling harmonic admittance matrix of new energy power station is calculated. Combined with the harmonic distortion level at the grid connection point, the harmonic emission level evaluation index of new energy power station is calculated. The stability margin assessment index and harmonic emission level assessment index of new energy power stations are used as comprehensive assessment indicators to conduct quantitative assessment of new energy power stations. Considering the stability margin and the minimum guarantee requirements for harmonic emission levels, the range of grid-connected converter ratios is constrained. Within the constrained range of grid-connected converters, the comprehensive evaluation index for each capacity ratio is calculated, and the capacity ratio is determined based on the optimal result of the comprehensive evaluation index.

8. A computer device, characterized in that, It includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the steps in the harmonic and stability margin constraint-based grid-type new energy allocation method as described in any one of claims 1-6.

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