Distribution network constant value setting method and system for large-scale distributed photovoltaic grid connection

Abstract

The invention discloses a distribution network constant value setting method and system for large-scale distributed photovoltaic grid connection, and relates to the technical field of power system relay protection, and the method comprises the steps: carrying out the protection region division of a power distribution network according to the network topology parameters of the power distribution network, and obtaining a plurality of protection regions; fault characteristic parameters in the protection areas are calculated respectively, and the distributed power supplies in the protection areas are classified and modeled based on the fault characteristic parameters to obtain an equivalent model; and calculating a protection setting value parameter based on the equivalent model, and generating a protection setting value setting result. According to the method, the dynamic response characteristics of the distributed power supply group can be accurately reflected, the problem of large errors of the protection range and sensitivity calculation in a traditional method is effectively solved, and reliable technical support is provided for protection configuration of a large-scale distributed photovoltaic grid-connected power distribution network.

Description

Technical Field

[0001] The present invention relates to the technical field of relay protection for electric power systems, and in particular to a distribution network setting value setting method and system for large-scale distributed photovoltaic grid-connected power systems. Background Art

[0002] In recent years, the distribution network has been facing the rapid development of growing and diverse loads and inverter-type distributed power sources, which has had a significant impact on the short-circuit current of the distribution network. Especially in terms of distributed power sources, countries around the world are pursuing clean energy production and gradually replacing clean energy with traditional petrochemical energy. In my country, renewable energy is accelerating its development, and the power supply is changing from "centralized" to "centralized and distributed". The increasing access to distributed power sources will have an important impact on the safe and stable operation of the distribution network: the distribution network has changed from a single power network to a multi-power network, which will change the normal and abnormal operation of the distribution network, affect the power flow distribution, and need to fully consider the impact of the short-circuit current injected by the distributed power source.

[0003] At present, in the planning and operation of distribution networks, the short-circuit current contributed by distributed renewable energy is not considered enough, resulting in the short-circuit current assessment of distribution networks often being lower than the actual level. From the perspective of calculating and designing short-circuit current, it can no longer meet the development needs of modern distribution networks, and the design of short-circuit current tends to be too conservative. Once a short-circuit fault occurs, due to the insufficient interruption capacity of the circuit breaker, the scope of the accident will expand and cause power outages to users. The main significance of relay protection is to maintain the normal operation of the power system and ensure the safety and stability of the power system during operation. Accurately setting the protection setting also ensures the correct operation of the relay protection device. With the development of computer technology, the setting setting system using computers has begun to appear and become popular. However, due to the diversity and complexity of distribution network relay protection, various existing setting systems lack corresponding pertinence, and the verification and approval of the setting sheet still need to be submitted manually.

[0004] The existing distribution network protection setting method is mainly based on static network parameters and simplified fault calculation models. This method has obvious shortcomings when dealing with the impact of large-scale distributed photovoltaic grid connection. First, the traditional short-circuit current calculation method fails to fully consider the dynamic characteristics of distributed power sources, resulting in a large deviation between the calculation results and the actual situation; second, the existing protection configuration scheme often simply equates the distributed power source to a static power source model, ignoring its dynamic response characteristics during the fault process, affecting the accuracy of the protection setting; finally, the traditional setting method lacks consideration of the clustering effect of the distributed power source group, and cannot achieve adaptive optimization of the protection setting. Summary of the invention

[0005] In view of the above-mentioned problems, the present invention is proposed.

[0006] Therefore, the present invention provides a distribution network constant value setting method and system for large-scale distributed photovoltaic grid-connected power generation, which can solve the problems mentioned in the background technology.

[0007] To solve the above technical problems, the present invention provides the following technical solutions: a distribution network constant value setting method for large-scale distributed photovoltaic grid-connected, comprising: dividing the distribution network into protection areas according to the network topology parameters of the distribution network to obtain multiple protection areas; respectively calculating the fault characteristic parameters in each of the protection areas, and classifying and modeling the distributed power sources in the protection areas based on the fault characteristic parameters to obtain an equivalent model; calculating the protection constant value parameters based on the equivalent model to generate the protection constant value setting result.

[0008] As a preferred solution of the distribution network constant value setting method for large-scale distributed photovoltaic grid-connected power generation described in the present invention, wherein: the distribution network is divided into protection areas according to the network topology parameters of the distribution network to obtain multiple protection areas, including the following steps: obtaining the main transformer impedance, system impedance, line impedance parameters and load parameters of each node of the distribution network, wherein if the load parameter is less than a first preset threshold, the load parameter is set to zero; calculating the impedance distance ratio between each node in the distribution network, wherein if the impedance distance ratio is greater than a second preset threshold, the corresponding node is recorded as a boundary node; and dividing the distribution network into multiple protection areas according to the boundary node.

[0009] As a preferred solution of the distribution network setting method for large-scale distributed photovoltaic grid connection described in the present invention, wherein: after the step of obtaining the main transformer impedance, system impedance, line impedance parameters and load parameters of each node of the distribution network, it also includes: obtaining the capacity parameters and access location information of the distributed power source in the distribution network; calculating the equivalent access location parameters according to the capacity parameters and access location information of the distributed power source; wherein the equivalent access location parameters are calculated according to the following formula:

[0010]

[0011] Among them, L 2～2n is the equivalent distributed generation access location parameter at the n-2th equivalent time, S DGn is the capacity parameter of the nth distributed generation, L is the total line length parameter of the system, and n is the number of distributed generation.

[0012] The equal-value access position parameters are used as access positions of a single equal-value distributed power source model.

[0013] As a preferred embodiment of the distribution network setting value determination method for large-scale distributed photovoltaic grid connection according to the present invention, the method includes: calculating the fault characteristic parameters in each protection area respectively, classifying and modeling the distributed power sources in the protection area based on the fault characteristic parameters to obtain an equivalent model, which includes the following steps: calculating the voltage values at the access points of each distributed power source when a three-phase short circuit occurs at the end of the line in each protection area, and if the voltage value is lower than the third preset threshold, recording the disconnection time of the corresponding distributed power source; classifying the distributed power sources with the same disconnection time in the protection area into a cluster, and calculating the total capacity of the distributed power sources in the cluster; according to the total capacity of the cluster and the access positions of each distributed power source, using the capacity weighting method to calculate the equivalent access position of the cluster, and establishing a single equivalent distributed power source model, that is, the equivalent model.

[0014] As a preferred embodiment of the distribution network setting value determination method for large-scale distributed photovoltaic grid connection according to the present invention, the method of classifying the distributed power sources with the same disconnection time in the protection area into a cluster includes the following steps: obtaining the fault response characteristic parameters of each distributed power source in the protection area, where the fault response characteristic parameters include a fault ride-through ability index, a voltage recovery characteristic, and a power output characteristic; the fault ride-through ability index is calculated by the following formula:

[0015]

[0016] where, FRT i is the fault ride-through ability index, P a and P b are the output powers after and before the fault respectively, T r is the fault ride-through time, and T f is the fault duration.

[0017] Construct a dynamic response correlation matrix of the distributed power sources, and perform cluster division based on the following criteria: if the correlation coefficient between the voltage recovery characteristic curve of distributed power source A and the voltage recovery characteristic curve of distributed power source B is greater than the arithmetic mean of their fault ride-through ability indexes, then A and B are classified into the same cluster; if the slope signs of the power output characteristic curves of the distributed power sources are the same, and the time difference at the inflection point is less than the minimum value of the corresponding power recovery time, then these distributed power sources are classified into the same cluster.

[0018] Calculate the characteristic parameters of each cluster:

[0019]

[0020] α i = γ i ·β i ·λ i ;

[0021] Among them, γ i is the contribution degree of fault ride-through, β i is the voltage support coefficient, and λ i is the power regulation coefficient.

[0022]

[0023]

[0024] Among them, ΔV i and ΔV m are the voltage change amount and the maximum voltage change amount respectively, Q i is the reactive power output, S i is the rated capacity, V l and V r are the local voltage and the rated voltage respectively, ΔP i is the power regulation amount, Δf is the frequency deviation, T r and T s are the response time and the standard time respectively.

[0025] Cluster optimization is carried out based on the dynamic coupling relationship between clusters. When the ratio of the fault ride-through ability indexes of two clusters is within the derivative range of the ratio of their voltage recovery rates, these two clusters are merged; when there is complementarity in the power regulation response between clusters, that is, the power rising section of one cluster overlaps with the power falling section of another cluster in time, and the overlap degree exceeds the harmonic mean of their respective regulation times, the clusters are kept independent.

[0026] As a preferred scheme of the distribution network setting value determination method for large-scale distributed photovoltaic grid connection described in the present invention, wherein: based on the equivalent model, protection setting value parameters are calculated to generate a protection setting value determination result, including the following steps: calculating the instantaneous overcurrent protection setting value and the overcurrent protection setting value based on the fault characteristic parameters and the equivalent model; wherein, the instantaneous overcurrent protection setting value is calculated according to the following formula:

[0027] I sd = K rel ·I k，max ;

[0028] Among them, I sd is the instantaneous overcurrent protection setting value, K rel is the reliability coefficient, and I k，max is the maximum short-circuit current.

[0029] The overcurrent protection setting value is calculated according to the following formula:

[0030]

[0031] Among them, Ioc is the over - current protection setting value, K st is the self - starting coefficient, K ret is the return coefficient, I L，max is the maximum load current of the branch.

[0032] Calculate the dynamic verification coefficient of the protection setting value. In the minimum operating mode of the distribution network, the two - phase short - circuit protection range is calculated according to the following formula:

[0033]

[0034] where, L pro is the protection range, Z 1s is the positive - sequence component of the branch, Z 1f is the positive - sequence short - circuit impedance under the maximum operating mode, I base is the reference current.

[0035] And for the faults at the end of the branch, the protection setting value needs to be set according to the sensitivity coefficient. The calculation formula of the sensitivity coefficient is:

[0036]

[0037] where, I k，min is the two - phase short - circuit current of the distribution network in the minimum operating mode.

[0038] If the sensitivity coefficient is greater than the product of the fault characteristic parameter and the fault crossing contribution degree, generate a setting value list including the instantaneous - current protection setting value and the over - current protection setting value; otherwise, take the fault crossing contribution degree as the correction coefficient, adjust the reliability coefficient, and then re - execute the above steps.

[0039] As a preferred scheme of the distribution network setting value setting method for large - scale distributed photovoltaic grid connection in the present invention, among them: calculating the dynamic verification coefficient of the protection setting value further includes constructing a protection dynamic characteristic matrix based on the fault crossing contribution degree, and the elements of the protection dynamic characteristic matrix are calculated according to the following formula:

[0040]

[0041] where, γ i and β j are the fault crossing contribution degree and voltage support coefficient of the i - th and j - th distributed power sources respectively, I k，i and I k，j are the corresponding short - circuit current contributions respectively.

[0042] When the eigenvalue of the protection dynamic characteristic matrix is greater than the power regulation coefficient of the distributed power generation cluster, the eigenvalue is used as the weighting factor of the dynamic verification coefficient; otherwise, the power regulation coefficient is used as the weighting factor of the dynamic verification coefficient.

[0043] To further solve the above technical problems, the present invention provides the following technical solution: A distribution network setting value calibration system for large-scale distributed photovoltaic grid connection, including:

[0044] A computer device, including a memory and a processor, the memory stores a computer program, characterized in that when the processor executes the computer program, the steps of the distribution network setting value calibration method for large-scale distributed photovoltaic grid connection as described above are implemented.

[0045] A computer-readable storage medium, on which a computer program is stored, characterized in that when the computer program is executed by a processor, the steps of the distribution network setting value calibration method for large-scale distributed photovoltaic grid connection as described above are implemented.

[0046] The beneficial effects of the present invention: By establishing a protection area division mechanism driven by network topology parameters and combining the dynamic characteristic analysis and cluster modeling method of distributed power generation, the present invention realizes the accurate calibration and adaptive optimization of protection setting values. Specifically, the distributed power generation classification method based on the dynamic response characteristic matrix effectively solves the problem of insufficient accuracy of traditional equivalent modeling; by introducing the fault ride-through ability index and voltage support coefficient, the accuracy of short-circuit current calculation is improved; the dynamic verification mechanism and adaptive adjustment strategy are adopted to significantly improve the reliability of protection setting values. Especially in the scenario with a high penetration rate of distributed power generation, the method proposed by the present invention can accurately reflect the dynamic response characteristics of the distributed power generation cluster, effectively overcome the problem of large calculation errors in protection range and sensitivity in traditional methods, and provide reliable technical support for the protection configuration of large-scale distributed photovoltaic grid-connected distribution networks. Description of the Drawings

[0047] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for description in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0048] Figure 1 It is a schematic diagram of the overall process of a distribution network setting value calibration method for large-scale distributed photovoltaic grid connection proposed by the present invention;

[0049] Figure 2 It is a diagram of a computer device in a distribution network setting value calibration method for large-scale distributed photovoltaic grid connection proposed by the present invention. Detailed implementation manners

[0050] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following will describe the detailed implementation manners of the present invention in conjunction with the accompanying drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0051] In the following description, many specific details are set forth to facilitate a thorough understanding of the present invention. However, the present invention may be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0052] Example 1, referring to Figure 1 , which is an embodiment of the present invention, and provides a method for setting distribution network fixed values for large-scale distributed photovoltaic grid connection.

[0053] S1: Divide the protection areas of the distribution network according to the network topology parameters of the distribution network to obtain multiple protection areas.

[0054] S1.1: Obtain the main transformer impedance, system impedance, line impedance parameters, and load parameters of each node of the distribution network.

[0055] Among them, if the load parameter is less than the first preset threshold, the load parameter is set to zero.

[0056] Furthermore, obtain the capacity parameters and access location information of the distributed power sources in the distribution network.

[0057] Calculate the equivalent access location parameter according to the capacity parameter and access location information of the distributed power source. Among them, the equivalent access location parameter is calculated according to the following formula:

[0058]

[0059] Among them, L 2～2n is the equivalent distributed power source access location parameter at the (n - 2)-th equivalent, S DGn is the capacity parameter of the n-th distributed power source, L is the total line length parameter of the system, and n is the number of distributed power sources.

[0060] Take the equivalent access location parameter as the access location of a single equivalent distributed power source model.

[0061] S1.2: Calculate the impedance distance ratio between each node in the distribution network.

[0062] Among them, if the impedance-distance ratio is greater than the second preset threshold, record the corresponding node as the boundary node.

[0063] Exemplarily, based on the actual operation data of the distribution network, set the determination threshold of the impedance-distance ratio. Taking a 10 kV distribution line as an example, the measured data is shown in Table 1:

[0064] Table 1 Measured data table of impedance distance

[0065] Node number Impedance value (Ω) Distance (km) Impedance - distance ratio N1 0.25 0.5 0.5 N2 0.45 0.8 0.56 N3 0.65 1.2 0.54 N4 0.85 1.5 0.57

[0066] S1.3: Divide the distribution network into multiple protection areas according to the boundary nodes.

[0067] Preferably, step S1 of the present invention solves the technical problem of the division of the protection area of the distribution network under the condition of large-scale distributed photovoltaic grid connection. Specifically: 1. The traditional method for dividing the protection area of the distribution network does not consider the dynamic characteristics of distributed power sources, resulting in unreasonable protection configuration; 2. In the prior art, the acquisition of distribution network parameters often ignores the influence of the capacity and location of distributed power sources, resulting in errors in short-circuit current calculation; 3. The traditional equivalent modeling method is computationally complex and fails to fully consider the clustering characteristics of distributed power source groups.

[0068] Through the technical solution of the present invention, by introducing a calculation method for equivalent access position parameters, the following beneficial effects are achieved: 1. By calculating the equivalent access position through capacity weighting, the modeling complexity is reduced and the calculation efficiency is improved; 2. Determining the boundary node based on the impedance-distance ratio makes the division of the protection area more accurate and reasonable; 3. Considering the influence of distributed power sources on network parameters improves the accuracy of short-circuit current calculation.

[0069] S2: Calculate the fault characteristic parameters in each protection area respectively, and classify and model the distributed power sources in the protection area based on the fault characteristic parameters to obtain an equivalent model.

[0070] S2.1: Calculate the voltage values at the access points of each distributed power source when a three-phase short circuit occurs at the end of the line in each protection area. If the voltage value is lower than the third preset threshold, record the disconnection time of the corresponding distributed power source.

[0071] Among them, the short-circuit current is linearly calculated according to the following formula:

[0072]

[0073] Among them, I k3φ represents the three-phase short-circuit current value, V n represents the rated voltage value, and Z 1∑ represents the positive-sequence equivalent impedance from the fault point to the power source.

[0074] S2.2: Classify the distributed power sources with the same off-grid time within the protection area into one cluster, and calculate the total capacity of the distributed power sources within the cluster:

[0075]

[0076] Among them, S total represents the total capacity of the cluster, S DGi represents the capacity of the i-th distributed power source, and n represents the number of distributed power sources within the cluster.

[0077] S2.2.1: Obtain the fault response characteristic parameters of each distributed power source within the protection area. The fault response characteristic parameters include the fault ride-through ability index, voltage recovery characteristic, and power output characteristic; among them:

[0078]

[0079] Among them, FRT i is the fault ride-through ability index, P a and P b are the output powers after and before the fault respectively, T r is the fault ride-through time, and T f is the fault duration.

[0080] It should be noted that the voltage recovery characteristic refers to the voltage response process characteristic of the distributed power source during and after the fault, mainly including the voltage recovery time, voltage recovery amplitude, and voltage recovery trajectory. This characteristic stems from the voltage support ability and transient response characteristic of the distributed power source, and is used in the present invention to evaluate the dynamic response similarity of different distributed power sources. The voltage recovery characteristic is quantified by measuring the rate of change of voltage (dV / dt) after the fault occurs, the minimum residual voltage value, and the time required to recover to 90% of the rated voltage. These parameters directly affect the grid connection stability of the distributed power source. In the cluster division, the distributed power sources with similar voltage recovery characteristics often exhibit similar fault adaptation abilities, so it is of great significance to use it as the classification basis. The power output characteristic describes the active power dynamic regulation ability of the distributed power source under system disturbances, including the power regulation rate, power recovery curve, and steady-state output level. This characteristic reflects the response ability of the distributed power source to system frequency fluctuations and the primary frequency modulation characteristic, and is an important index for evaluating its grid connection performance. In the present invention, this characteristic is quantified by analyzing the rate of change of the power output curve (dP / dt), the power recovery time, and the steady-state deviation. The similarity of the power output characteristic is directly related to the frequency modulation ability of the distributed power source group and system stability, and is another important basis for cluster division.

[0081] S2.2.2: Construct the dynamic response correlation matrix of distributed power sources, and perform cluster division based on the following criteria: If the correlation coefficient between the voltage recovery characteristic curve of distributed power source A and that of distributed power source B is greater than the arithmetic mean of their fault ride-through ability indicators, then A and B are divided into the same cluster; If the slope signs of the power output characteristic curves of distributed power sources are the same, and the time difference at the inflection point is less than the minimum value of the corresponding power recovery time, then these distributed power sources are divided into the same cluster.

[0082] It should be noted that the dynamic response correlation matrix is a mathematical model describing the dynamic characteristic correlation of distributed power source groups, and its matrix elements reflect the similarity degree of fault response characteristics between different distributed power sources. This matrix is constructed by calculating the correlation coefficient of the voltage recovery characteristic curve and the synchronization index of the power output characteristic. The calculation method of matrix elements is as follows: First, extract the characteristic point sequences of the voltage and power response curves, then calculate the Pearson correlation coefficient between these sequences, and finally perform weighting in combination with the fault ride-through ability indicator. In the present invention, this matrix is used to quantitatively evaluate the dynamic coupling relationship between distributed power sources, providing a mathematical basis for cluster division and avoiding the limitations of traditional methods that only rely on static parameters.

[0083] S2.2.3: Calculate the characteristic parameters of each cluster, where:

[0084]

[0085] α i =γ i ·β i ·λ i ;

[0086] Among them, γ i is the contribution degree of fault ride-through, β i is the voltage support coefficient, λ i is the power regulation coefficient. These three are determined by the following relationships respectively:

[0087]

[0088] Among them, ΔV i and ΔV m are the voltage change amount and the maximum voltage change amount respectively, Q i is the reactive power output, S i is the rated capacity, V l and V r are the local voltage and the rated voltage respectively, ΔP i is the power regulation amount, Δf is the frequency deviation, T r and T s are the response time and the standard time respectively.

[0089] S2.2.4: Cluster optimization is performed based on the dynamic coupling relationship between clusters. When the ratio of the fault ride-through capability indicators of two clusters is within the derivative range of their voltage recovery rate ratio, the two clusters are merged. When the power regulation responses between clusters are complementary, that is, the power increase segment of one cluster overlaps with the power decrease segment of another cluster in time, and the overlap exceeds the harmonic mean of their respective regulation times, the clusters are kept independent.

[0090] S2.3: Based on the total capacity of the cluster and the access location of each distributed power source, the equivalent access location of the cluster is calculated using the capacity weighted method, and a single equivalent distributed power source model is established.

[0091] In a specific embodiment, the technical solution of the present invention is used to handle the equivalent modeling problem of 15 distributed photovoltaic power sources connected to a 10kV distribution line. First, the fault ride-through capability index of each photovoltaic power source is calculated, and the results show that the distribution is between 0.65 and 0.92. Through dynamic response correlation matrix analysis, these photovoltaic power sources are preliminarily divided into 3 clusters. Further analysis shows that the voltage recovery characteristic correlation coefficient of the first cluster (including 6 photovoltaic power sources) reaches 0.89, the slope of the power output characteristic curve is positive, and the inflection point time difference is less than 0.2s; the γ of the second cluster (including 5 photovoltaic power sources) is 0.89, and the slope of the power output characteristic curve is positive, and the inflection point time difference is less than 0.2s. i The average value is 0.78, β i The average value is 0.85; the third cluster (including 4 photovoltaic power sources) shows obvious complementary regulation characteristics. Through experimental verification, the voltage response error of the equivalent model established by the present invention under a three-phase short-circuit fault does not exceed 3%, and the power output error is controlled within 5%, which reduces the errors by 45% and 38% respectively compared with the traditional static clustering method, and reduces the modeling calculation time from the original 72 minutes to 18 minutes.

[0092] The distributed power classification modeling method based on dynamic characteristics proposed in the present invention significantly improves the accuracy of the equivalent model by introducing fault ride-through capability indicators, dynamic response association matrices and multi-dimensional weight coefficients. This method not only takes into account the static parameters of the distributed power supply, but also pays more attention to its dynamic response characteristics under fault conditions, so that the model can better reflect the dynamic behavior of the actual system. Experimental results show that while ensuring the accuracy of modeling, the present invention greatly improves the calculation efficiency and provides a reliable theoretical basis for the protection configuration of large-scale distributed photovoltaic grid-connected systems. Compared with the prior art, the present invention effectively solves the problems of insufficient accuracy and large amount of calculation in traditional equivalent modeling through dynamic characteristic analysis and cluster optimization, especially in the dynamic response simulation under fault conditions. It shows obvious advantages.

[0093] S3: Calculate the protection setting parameters based on the equivalent model and generate the protection setting setting results.

[0094] S3.1: Calculate the instantaneous overcurrent protection setting value and the overcurrent protection setting value based on the fault characteristic parameters and the equivalent model, where:

[0095] The instantaneous overcurrent protection setting value is calculated according to the following formula:

[0096] I sd = K rel ·I k，max ;

[0097] Where, I sd is the instantaneous overcurrent protection setting value, K rel is the reliability coefficient, and I k，max is the maximum short-circuit current.

[0098] The overcurrent protection setting value is calculated according to the following formula:

[0099]

[0100] Where, I oc is the overcurrent protection setting value, K st is the self-starting coefficient, K ret is the return coefficient, and I L，max is the maximum load current of the branch.

[0101] S3.2: Calculate the dynamic verification coefficient of the protection setting value. In the minimum operating mode of the distribution network (this mode refers to a running state when the capacity of the power supply put into operation reaches the minimum value and the equivalent impedance of the system reaches the maximum value. In this operating mode, if a short-circuit fault occurs, the short-circuit current passing through the short-circuit point will be the smallest), the two-phase short-circuit protection range is calculated according to the following formula:

[0102]

[0103] Where, L pro is the protection range, Z 1s is the positive sequence component of the branch, Z 1f is the positive sequence short-circuit impedance in the maximum operating mode, and I base is the reference current.

[0104] If a fault occurs at the end of the branch in the minimum operating mode of the distribution network, the protection setting value needs to be set according to the sensitivity coefficient. The calculation formula of the sensitivity coefficient is:

[0105] The sensitivity coefficient is calculated according to the following formula:

[0106]

[0107] Where, I k，min is the two-phase short-circuit current of the distribution network in the minimum operating mode.

[0108] The dynamic verification coefficient for calculating the protection setting value further includes constructing a protection dynamic characteristic matrix based on the fault ride-through contribution degree, where the elements of the protection dynamic characteristic matrix are calculated according to the following formula:

[0109]

[0110] where γ i and β j are the fault ride-through contribution degree and voltage support coefficient of the i-th and j-th distributed power sources respectively, and I k，i and I k，j are the corresponding short-circuit current contributions respectively.

[0111] When the eigenvalue of the protection dynamic characteristic matrix is greater than the power regulation coefficient of the distributed power source cluster, the eigenvalue is used as the weighting factor of the dynamic verification coefficient; otherwise, the power regulation coefficient is used as the weighting factor of the dynamic verification coefficient.

[0112] S3.3: If the sensitivity coefficient is greater than the product of the fault characteristic parameter and the fault ride-through contribution degree, generate a setting value list including the instantaneous overcurrent protection setting value and the overcurrent protection setting value; otherwise, use the fault ride-through contribution degree as the correction coefficient, adjust the reliability coefficient, and then return to execute S3.1.

[0113] Preferably, in this embodiment, for the protection setting problem of a certain 10 kV distribution line, the technical solution of the present invention is applied for processing. First, calculate the instantaneous overcurrent protection setting value and the overcurrent protection setting value based on the equivalent model established in the previous steps, where a protection dynamic characteristic matrix is introduced to characterize the dynamic response characteristics of the distributed power source. By calculating the matrix eigenvalue in real time, a dynamic verification mechanism for the setting value is established. The experimental results show that the setting scheme after introducing the dynamic characteristic matrix can accurately reflect the fault response characteristics of the distributed power source, and significantly improves the accuracy of the protection setting value. Compared with the traditional static setting method, the calculation error of the protection range in this scheme is reduced by nearly half, and the calculation accuracy of the sensitivity coefficient is improved by about one-third. Especially in the scenario with a high penetration rate of distributed power sources, the traditional method often has problems such as an overly large protection range or insufficient sensitivity, while this scheme effectively solves this problem through the adaptive adjustment of the dynamic verification coefficient.

[0114] The protection setting value determination method based on dynamic characteristics proposed by the present invention realizes the accurate quantification of the fault response characteristics of distributed power sources by establishing a protection dynamic characteristic matrix. The core innovation of this method lies in the organic combination of the fault ride-through ability, voltage support ability, and power regulation characteristics of distributed power sources, and constructs a complete dynamic verification system for setting values. Experimental verification shows that while ensuring the reliability of the setting results, this method significantly improves the calculation efficiency. Especially under the condition of large system disturbances, this solution can timely adjust the protection setting values through the eigenvalue analysis of the dynamic characteristic matrix to ensure the correct operation of the protection device. Compared with the existing technologies, this solution not only solves the problem of insufficient setting value accuracy in traditional setting methods, but also realizes the adaptive optimization of protection setting values, providing effective technical support for the protection configuration of distribution networks with large-scale distributed power sources.

[0115] In summary, the present invention realizes the accurate setting and adaptive optimization of protection setting values by establishing a protection area division mechanism driven by network topology parameters, combining the dynamic characteristic analysis of distributed power sources and the cluster modeling method. Specifically, the distributed power source classification method based on the dynamic response characteristic matrix effectively solves the problem of insufficient accuracy in traditional equivalent modeling; by introducing the fault ride-through ability index and voltage support coefficient, the accuracy of short-circuit current calculation is improved; the dynamic verification mechanism and adaptive adjustment strategy are adopted to significantly improve the reliability of protection setting values. Especially in the scenario with a high penetration rate of distributed power sources, the method proposed by the present invention can accurately reflect the dynamic response characteristics of distributed power source groups, effectively overcoming the problems of large calculation errors in protection range and sensitivity in traditional methods, and providing reliable technical support for the protection configuration of large-scale distributed photovoltaic grid-connected distribution networks.

[0116] Embodiment 2 is an embodiment of the present invention, which provides a distribution network setting value determination system for large-scale distributed photovoltaic grid connection, including:

[0117] An area division module, configured to divide the protection areas of the distribution network according to the network topology parameters of the distribution network to obtain multiple protection areas;

[0118] A model construction module, configured to calculate the fault characteristic parameters in each protection area respectively, and classify and model the distributed power sources in the protection area based on the fault characteristic parameters to obtain an equivalent model;

[0119] A result generation module, configured to calculate the protection setting value parameters based on the equivalent model and generate a protection setting value determination result.

[0120] Embodiment 3, refer to Figure 2, which is an embodiment of the present invention and is different from the previous embodiment in that: when the function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art or a part of this technical solution can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of the present invention. The aforementioned storage medium includes: USB flash drives, mobile hard disks, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), magnetic disks, or optical discs, etc., which can store program codes of various kinds.

[0121] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a definite sequence list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by an instruction execution system, apparatus, or device (such as a computer-based system, a system including a processor, or other systems that can fetch instructions from the instruction execution system, apparatus, or device and execute the instructions), or in combination with these instruction execution systems, apparatuses, or devices. For the purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport a program for use by or in combination with an instruction execution system, apparatus, or device.

[0122] More specific examples (nonexhaustive list) of computer-readable media include the following: electrical connection parts with one or more wirings (electronic devices), portable computer disk cartridges (magnetic devices), random access memories (RAM), read-only memories (ROM), erasable programmable read-only memories (EPROM or flash memories), optical fiber devices, and portable compact disc read-only memories (CDROM). Additionally, the computer-readable medium can even be paper or other suitable media on which the program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other media, then editing, interpreting, or otherwise processing it as necessary, and then storing it in a computer memory.

[0123] It should be understood that each part of the present invention can be implemented by hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, any one or a combination of the following techniques well known in the art can be used: discrete logic circuits having logic gate circuits for implementing logic functions on data signals, application specific integrated circuits having appropriate combinational logic gate circuits, programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), etc.

[0124] Embodiment 4, an embodiment of the present invention, provides a method for setting distribution network fixed values for large-scale distributed photovoltaic grid connection. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0125] Based on the IEEE 33-node distribution network standard test system, 15 distributed photovoltaic power access points are set, and the total installed capacity is 45% of the reference capacity. The protection fixed value calculations are carried out by using the traditional static setting method and the solution of the present invention respectively in the experiment. To comprehensively evaluate the performance of the solution, different operating conditions are designed in the experiment: normal operating mode, heavy load mode, and light load mode. For each mode, single-phase grounding, two-phase short circuit, and three-phase short circuit faults are simulated respectively. A detailed system model is constructed through the PSCAD / EMTDC simulation platform, with a simulation step size of 0.01 s, and the fault duration is set to 0.5 s.

[0126] To verify the advantages of the present invention in terms of the dynamic response characteristics of distributed power sources, the experiment focuses on the voltage recovery process and power output characteristics during the fault. Through dynamic characteristic matrix analysis, the 15 distributed photovoltaic power sources are divided into 3 characteristic clusters, which represent fast response type, voltage support type, and power regulation type respectively. Based on this classification, the protection fixed value setting method of the present invention is adopted and compared with the traditional method. The experimental data collection includes key indicators such as fault detection time, protection action time, voltage recovery rate, and power output fluctuation.

[0127] Table 2 Comparison of protection performance under different fault types

[0128]

[0129] Table 3 Comparison of fixed value setting performance under different operating conditions

[0130]

[0131] Data analysis of Table 1 shows that the present invention is significantly superior to traditional methods in terms of fault detection time, protection action accuracy and selectivity. Especially in the case of single-phase grounding fault, the fault detection time of the present invention is shortened by about 38% compared with traditional methods, the protection action accuracy is increased by 5.5 percentage points, and the coordination success rate is increased by 7.1 percentage points. This fully demonstrates that the dynamic characteristic analysis method proposed by the present invention can effectively improve the performance of the protection system. The experimental data in Table 2 show that the present invention exhibits significant advantages under different operating conditions. In the most challenging heavy-load mode, the current setting error of the present invention is only 37.6% of that of traditional methods, the protection range error is reduced by 61%, and the calculation time is reduced by 67.6%. It is particularly worth noting that the present invention has the most significant improvement in the deviation of the sensitivity coefficient, indicating that the proposed scheme can more accurately adapt to the dynamic characteristics of distributed power sources.

[0132] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A distribution network setting method for large-scale distributed photovoltaic grid-connected, characterized in that: include: Dividing the distribution network into protection areas according to the network topology parameters of the distribution network to obtain a plurality of protection areas; Calculating fault characteristic parameters in each of the protection areas respectively, and classifying and modeling the distributed power sources in the protection areas based on the fault characteristic parameters to obtain an equivalent model; The protection setting parameters are calculated based on the equivalent model to generate the protection setting setting results.

2. The method for setting the distribution network constant value for large-scale distributed photovoltaic grid connection according to claim 1, characterized in that: The distribution network is divided into protection areas according to the network topology parameters of the distribution network to obtain a plurality of protection areas, including the following steps: Obtaining the main transformer impedance, system impedance, line impedance parameters and load parameters of each node of the distribution network, wherein if the load parameter is less than a first preset threshold, the load parameter is set to zero; Calculating the impedance distance ratio between nodes in the distribution network, wherein if the impedance distance ratio is greater than a second preset threshold, recording the corresponding node as a boundary node; The power distribution network is divided into a plurality of protection areas according to the boundary nodes.

3. The method for setting the distribution network constant value for large-scale distributed photovoltaic grid connection according to claim 2, characterized in that: After the step of obtaining the main transformer impedance, system impedance, line impedance parameters and load parameters of each node of the distribution network, the following steps are further included: Acquire capacity parameters and access location information of distributed power sources in the distribution network; The equivalent access location parameter is calculated according to the capacity parameter of the distributed power source and the access location information; wherein the equivalent access location parameter is calculated according to the following formula: Among them, L 2～2n is the equivalent distributed generation access location parameter at the n-2th equivalent time, S DGn is the capacity parameter of the nth distributed generation, L is the total line length parameter of the system, and n is the number of distributed generation; The equal-value access position parameters are used as access positions of a single equal-value distributed power source model.

4. The method for setting the value of the distribution network for large-scale distributed photovoltaic grid connection according to claim 3, characterized in that: The fault characteristic parameters in each protection area are calculated respectively, and the distributed power sources in the protection area are classified and modeled based on the fault characteristic parameters to obtain an equivalent model, including the following steps: Calculating the voltage value of each distributed power source access point when a three-phase short circuit occurs at the end of each protection area line, and if the voltage value is lower than a third preset threshold, recording the off-grid time of the corresponding distributed power source; The distributed power sources with the same off-grid time in the protection area are grouped into a cluster, and the total capacity of the distributed power sources in the cluster is calculated; According to the total capacity of the cluster and the access position of each distributed power source, the equivalent access position of the cluster is calculated using a capacity weighted method, and a single equivalent distributed power source model, namely, the equivalent model, is established.

5. The method for setting the distribution network constant value for large-scale distributed photovoltaic grid connection according to claim 4, characterized in that: The distributed power sources with the same off-grid time in the protection area are grouped into a cluster, including the following steps: Obtain fault response characteristic parameters of each distributed power source in the protection area, wherein the fault response characteristic parameters include a fault ride-through capability index, a voltage recovery characteristic, and a power output characteristic; the fault ride-through capability index is calculated by the following formula: Among them, FRT i is the fault ride-through capability index, P a and P b are the output power before and after the fault, T r is the fault ride-through time, T f is the fault duration; The dynamic response correlation matrix of distributed power sources is constructed, and cluster division is performed based on the following criteria: if the correlation coefficient between the voltage recovery characteristic curve of distributed power source A and the voltage recovery characteristic curve of distributed power source B is greater than the arithmetic mean of the fault ride-through capability indicators of the two, then A and B are divided into the same cluster; if the slope signs of the power output characteristic curves of the distributed power sources are the same, and the time difference of the inflection point is less than the minimum value of the corresponding power recovery time, then these distributed power sources are divided into the same cluster; Calculate the characteristic parameters of each cluster: a i =c i ·b i ·l i ; Among them, γ i is the fault crossing contribution, β i is the voltage support coefficient, λ i is the power regulation factor; Where, ΔV i and ΔV m are the voltage change and the maximum voltage change, Q i is reactive power output, S i is the rated capacity, V l and V r are local voltage and rated voltage, ΔP i is the power regulation amount, Δf is the frequency deviation, T r and T s Respectively, response time and standard time; Cluster optimization is performed based on the dynamic coupling relationship between clusters. When the ratio of the fault ride-through capability indicators of two clusters is within the derivative range of their voltage recovery rate ratio, the two clusters are merged. When the power regulation responses between clusters are complementary, that is, the power increase segment of one cluster overlaps with the power decrease segment of another cluster in time, and the overlap exceeds the harmonic mean of their respective regulation times, the clusters are kept independent.

6. The method for setting the distribution network constant value for large-scale distributed photovoltaic grid connection according to claim 5, characterized in that: Calculating the protection setting parameters based on the equivalent model and generating the protection setting setting result include the following steps: The current quick-break protection setting value and the overcurrent protection setting value are calculated based on the fault characteristic parameters and the equivalent model; wherein the current quick-break protection setting value is calculated according to the following formula: I sd =K rel ·I k，max ; Among them, I sd K is the current quick-break protection setting value, rel is the reliability coefficient, I k，max is the maximum short-circuit current; The overcurrent protection setting is calculated according to the following formula: Among them, I oc is the overcurrent protection setting, K st is the self-starting coefficient, K ret is the return coefficient, I L，max is the maximum load current of the branch; Calculate the dynamic verification coefficient of the protection setting value. When the distribution network is in the minimum operation mode, the two-phase short-circuit protection range is calculated according to the following formula: Among them, L pro Z is the protection range. 1s It is composed of positive sequence of branches, Z 1f is the positive sequence short-circuit impedance under the maximum operation mode, I base is the reference current; And the protection setting value of the branch end fault needs to be adjusted according to the sensitivity coefficient. The calculation formula of the sensitivity coefficient is: Among them, I k，min It is the two-phase short-circuit current of the distribution network in the minimum operation mode; If the sensitivity coefficient is greater than the product of the fault characteristic parameter and the fault ride-through contribution, a setting value list including the current quick-break protection setting and the overcurrent protection setting is generated; otherwise, the fault ride-through contribution is used as a correction coefficient, and the reliability coefficient is adjusted and the above steps are re-executed.

7. The method for setting the distribution network constant value for large-scale distributed photovoltaic grid connection according to claim 6, characterized in that: The calculation of the dynamic verification coefficient of the protection setting value also includes constructing a protection dynamic characteristic matrix based on the fault ride-through contribution, wherein the elements of the protection dynamic characteristic matrix are calculated according to the following formula: Among them, γ i and β j are the fault ride-through contribution and voltage support coefficient of the i-th and j-th distributed generation, respectively. k，i and I k，j are the corresponding short-circuit current contributions respectively; When the eigenvalue of the protection dynamic characteristic matrix is ​​greater than the power regulation coefficient of the distributed power supply cluster, the eigenvalue is used as the weighting factor of the dynamic verification coefficient; otherwise, the power regulation coefficient is used as the weighting factor of the dynamic verification coefficient.

8. A distribution network setting value setting system for large-scale distributed photovoltaic grid-connected, based on the distribution network setting value setting method for large-scale distributed photovoltaic grid-connected according to any one of claims 1 to 7, characterized in that: include, A region division module, used to divide the distribution network into protection regions according to the network topology parameters of the distribution network to obtain multiple protection regions; A model building module, used to calculate the fault characteristic parameters in each of the protection areas respectively, and classify and model the distributed power sources in the protection areas based on the fault characteristic parameters to obtain an equivalent model; The result generation module is used to calculate the protection setting parameters based on the equivalent model and generate the protection setting setting results.

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 distribution network constant value setting method for large-scale distributed photovoltaic grid-connected are implemented as described in any one of claims 1 to 7.

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 distribution network constant value setting method for large-scale distributed photovoltaic grid-connected power generation according to any one of claims 1 to 7 are implemented.

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