Method and system for evaluating adaptive boundary of distributed photovoltaic access protection

Abstract

The invention discloses a distributed photovoltaic access protection adaptability boundary evaluation method and system, and belongs to the technical field of power distribution network protection. The method comprises the following steps: determining the main influence of distributed photovoltaic access on staged overcurrent protection, and determining an access adaptability boundary analysis principle of distributed photovoltaic; based on the access adaptability boundary analysis principle, determining a distributed photovoltaic access capacity boundary under the main influence; and taking an intersection of the distributed photovoltaic access capacity boundaries under the main influence as a distributed photovoltaic access protection adaptability boundary. According to the method, the distributed photovoltaic access boundary under the constraint of the existing protection configuration can be clarified, and when the protection constant value needs to be adjusted or the protection principle needs to be optimized in the existing protection configuration is clarified.

Description

Technical Field

[0001] The present invention relates to the technical field of distribution network protection, and more specifically, to a method and system for evaluating adaptive boundaries of distributed photovoltaic access protection. Background Art

[0002] The current power grid is in an accelerated transformation period of new power system construction. Distributed new energy, energy storage, electric vehicles and other nonlinear power electronic equipment are continuously and rapidly connected, and the one-way step-by-step transmission mode of the power grid is changing to two-way multi-level transmission. Distributed photovoltaic is the main form of new energy access to the distribution network. The effects of distributed photovoltaic boost, extraction and reverse overcurrent have a significant impact on the current protection performance of the distribution network. The selectivity and sensitivity of traditional distribution network protection are seriously affected, and the risks of protection refusal and false operation are greatly increased.

[0003] The current distribution network usually adopts the principle of staged overcurrent protection. The quick-break section (Section I) is designed to quickly cut off the fault without delay (<0.1s), especially in rural distribution lines with more distributed photovoltaic access. Due to the long lines and many branches, except for the line outlet switch protection (outgoing line protection), all levels of protection need to exit Section I to avoid over-tripping. Sections II and III of the protection are coordinated step by step by setting delays. The boosting effect of the photovoltaic system may cause the current flowing through the protection device after the fault to increase, thereby expanding the protection range, which will increase the probability of over-tripping and the scope of power outage. On the contrary, the draw-out effect of photovoltaics may reduce the current flowing through the protection after the fault, causing the protection device to refuse to operate, resulting in the system running with a fault for a long time, so that the fault cannot be removed for a long time. In addition, the reverse overcurrent effect of photovoltaics may cause the reverse fault current to exceed the protection setting value, thereby causing the protection to malfunction.

[0004] When designing the capacity and scale of new energy access in the distribution network, it is necessary to consider its impact on the performance of protection action, and consider the maximum access capacity under the constraints of the existing protection configuration (that is, when the access capacity of distributed power sources reaches a certain limit, it will cause protection misoperation or refusal to operate. When this limit is exceeded, it is necessary to adjust the protection setting or optimize the protection principle to solve the problem). Otherwise, it is impossible to clearly know when the protection configuration needs to be adjusted. However, the current research on the protection adaptability of distributed power access mainly uses simulation methods and considers typical penetration rates to conduct qualitative analysis of protection action performance. The research mainly focuses on the improvement of protection methods and strategies after distributed power sources are connected to the distribution network, but lacks a quantitative evaluation method for the protection adaptability boundary, and does not clearly define under what circumstances new protection principles and configuration strategies need to be adopted for protection, which cannot guide the disposal of massive stock protection in actual projects. Summary of the invention

[0005] In view of the above problems, the present invention proposes a method for evaluating the adaptive boundary of distributed photovoltaic access protection, comprising:

[0006] Determine the main impact of the distributed photovoltaic access on the staged overcurrent protection, and determine the adaptive boundary analysis principle of the distributed photovoltaic access;

[0007] Based on the access adaptability boundary analysis principle, determine the distributed photovoltaic access capacity boundary under the main influence;

[0008] The intersection of the distributed photovoltaic access capacity boundaries under the main influences is taken as the distributed photovoltaic access protection adaptability boundary.

[0009] Optional, main effects include: photovoltaic boosting effect, photovoltaic extraction effect and reverse overcurrent effect.

[0010] Optionally, the distributed photovoltaic access adaptability boundary analysis principle includes: the photovoltaic short-circuit current takes the scenario with the greatest impact, the photovoltaic access location takes the scenario with the greatest impact, and the protection setting takes the boundary value within the allowable range.

[0011] Optionally, based on the access adaptability boundary analysis principle, the distributed photovoltaic access capacity boundary under the main influence of photovoltaic boosting is determined, including:

[0012] For the photovoltaic boosting effect, the I section of the overcurrent protection of each outlet, which has a substantial impact on the protection selectivity, is set as the boundary analysis constraint condition under the photovoltaic boosting effect. When a three-phase short-circuit fault occurs at the farthest position allowed by the I section protection range, the maximum short-circuit current provided by the main grid power supply and distributed photovoltaic power generation does not exceed the I section protection setting value, which is used as the boundary analysis constraint condition under the photovoltaic boosting effect.

[0013] Under the boundary analysis constraint conditions under the photovoltaic boost effect, the distributed photovoltaic access capacity boundary under the main influence of photovoltaic boost effect is determined, and the calculation formula is as follows:

[0014]

[0015] in, and The calculation formula is as follows:

[0016]

[0017] Among them, S DG is the total capacity of distributed power sources connected to other lines on the bus, S T is the capacity of the system main transformer, Z T is the transformer impedance, |Z T | is the transformer impedance amplitude, is the per unit value of transformer impedance, is the magnitude of the transformer impedance per unit value, Z L is the line unit impedance, It is the sum of the transformer impedance and the line impedance within the protection range of the I-stage protection setting target. is the sum of the transformer impedance and the line impedance within the farthest protection range allowed by section I, θ1 and θ2 are Z T and Z L The impedance angle, c is the voltage coefficient;

[0018] The value range of c is 1.0-1.1, the value of θ1 is 90°, and the value of θ2 is 0°-90°.

[0019] Optionally, according to the approximate relationship between the distribution network conductor parameters and the current carrying capacity and system capacity, θ2 and S T ,θ2 and S T The calculation formula is as follows:

[0020]

[0021] Optionally, based on the access adaptability boundary analysis principle, determining the distributed photovoltaic access capacity boundary under the main influence of photovoltaic extraction includes:

[0022] When a two-phase short-circuit fault occurs at the end of the protection range, under the combined influence of the main grid power supply and all distributed photovoltaics connected within the protection range, the short-circuit current flowing through the protection is not less than the protection setting value, which is used as the boundary analysis constraint condition under the photovoltaic extraction effect;

[0023] Under the boundary analysis constraint conditions under the photovoltaic draw-out effect, the distributed photovoltaic access capacity boundary under the main influence of photovoltaic draw-out is determined, and the calculation formula is as follows:

[0024]

[0025] Among them, S DG is the total capacity of distributed power sources connected to other lines on the bus, U n is the amplitude of the system rated phase voltage, K sen is the sensitivity coefficient, Z BtoDG is the impedance from the bus to the centralized access point of the distributed generation, Z DGtof is the impedance from the centralized access point of the distributed generation to the fault point, Z T is the transformer impedance and c is the voltage coefficient.

[0026] Optionally, based on the access adaptability boundary analysis principle, determining the distributed photovoltaic access capacity boundary under the main influence of reverse overcurrent includes:

[0027] When the upstream line fails, the maximum short-circuit current provided by the distributed photovoltaic power generation shall not exceed the fixed value of section III as the boundary analysis constraint condition under the reverse overcurrent action;

[0028] Under the boundary analysis constraint conditions under the reverse overcurrent effect, the distributed photovoltaic access capacity boundary under the main influence of reverse overcurrent is determined, and the calculation formula is as follows:

[0029]

[0030] Among them, S DG is the total capacity of distributed power sources connected to other lines on the bus, U n is the amplitude of the system rated phase voltage, K sen is the sensitivity coefficient, c is the voltage coefficient, Z tot It is the sum of the loop impedances from the main power supply to the fault point after a fault occurs at the end of the protection range concerned during fixed value setting.

[0031] In another aspect, the present invention further proposes a system for distributed photovoltaic access protection adaptability boundary assessment, comprising:

[0032] An initial unit, used to determine the main impact of the distributed photovoltaic access on the staged overcurrent protection, and determine the adaptive boundary analysis principle of the distributed photovoltaic access;

[0033] A calculation unit, used to determine the distributed photovoltaic access capacity boundary under the main influence based on the access adaptability boundary analysis principle;

[0034] The evaluation unit is used to take the intersection of the distributed photovoltaic access capacity boundaries under the main influence as the distributed photovoltaic access protection adaptability boundary.

[0035] Optional, main effects include: photovoltaic boosting effect, photovoltaic extraction effect and reverse overcurrent effect.

[0036] Optionally, the distributed photovoltaic access adaptability boundary analysis principle includes: the photovoltaic short-circuit current takes the scenario with the greatest impact, the photovoltaic access location takes the scenario with the greatest impact, and the protection setting takes the boundary value within the allowable range.

[0037] Optionally, the calculation unit determines the distributed photovoltaic access capacity boundary under the main influence of photovoltaic auxiliary effect based on the access adaptability boundary analysis principle, including:

[0038] For the photovoltaic boosting effect, the I section of the overcurrent protection of each outlet, which has a substantial impact on the protection selectivity, is set as the boundary analysis constraint condition under the photovoltaic boosting effect. When a three-phase short-circuit fault occurs at the farthest position allowed by the I section protection range, the maximum short-circuit current provided by the main grid power supply and distributed photovoltaic power generation does not exceed the I section protection setting value, which is used as the boundary analysis constraint condition under the photovoltaic boosting effect.

[0039] Under the boundary analysis constraint conditions under the photovoltaic boost effect, the distributed photovoltaic access capacity boundary under the main influence of photovoltaic boost effect is determined, and the calculation formula is as follows:

[0040]

[0041] in, and The calculation formula is as follows:

[0042]

[0043] Among them, S DG is the total capacity of distributed power sources connected to other lines on the bus, S T is the capacity of the system main transformer, Z T is the transformer impedance, |Z T | is the transformer impedance amplitude, is the per unit value of the transformer impedance, is the magnitude of the transformer impedance per unit value, Z L is the line unit impedance, It is the sum of the transformer impedance and the line impedance within the protection range of the I-stage protection setting target. is the sum of the transformer impedance and the line impedance within the farthest protection range allowed by section I, θ1 and θ2 are Z T and Z L The impedance angle, c is the voltage coefficient;

[0044] The value range of c is 1.0-1.1, the value of θ1 is 90°, and the value of θ2 is 0°-90°.

[0045] Optionally, the calculation unit obtains θ2 and S according to the approximate correlation between the distribution network conductor parameters and the current carrying capacity and system capacity. T ,θ2 and S T The calculation formula is as follows:

[0046]

[0047] Optionally, the calculation unit determines the distributed photovoltaic access capacity boundary under the main influence of photovoltaic extraction based on the access adaptability boundary analysis principle, including:

[0048] When a two-phase short-circuit fault occurs at the end of the protection range, under the combined influence of the main grid power supply and all distributed photovoltaics connected within the protection range, the short-circuit current flowing through the protection is not less than the protection setting value, which is used as the boundary analysis constraint condition under the photovoltaic extraction effect;

[0049] Under the boundary analysis constraint conditions under the photovoltaic draw-out effect, the distributed photovoltaic access capacity boundary under the main influence of photovoltaic draw-out is determined, and the calculation formula is as follows:

[0050]

[0051] Among them, S DG is the total capacity of distributed power sources connected to other lines on the bus, U n is the amplitude of the system rated phase voltage, K sen is the sensitivity coefficient, Z BtoDG is the impedance from the bus to the centralized access point of the distributed generation, Z DGtof is the impedance from the centralized access point of the distributed generation to the fault point, Z T is the transformer impedance and c is the voltage coefficient.

[0052] Optionally, based on the access adaptability boundary analysis principle, determining the distributed photovoltaic access capacity boundary under the main influence of reverse overcurrent includes:

[0053] When the upstream line fails, the maximum short-circuit current provided by the distributed photovoltaic power generation shall not exceed the fixed value of section III as the boundary analysis constraint condition under the reverse overcurrent action;

[0054] Under the boundary analysis constraint conditions under the reverse overcurrent effect, the distributed photovoltaic access capacity boundary under the main influence of reverse overcurrent is determined, and the calculation formula is as follows:

[0055]

[0056] Among them, S DG is the total capacity of distributed power sources connected to other lines on the bus, U n is the amplitude of the system rated phase voltage, K sen is the sensitivity coefficient, c is the voltage coefficient, Z tot It is the sum of the loop impedances from the main power supply to the fault point after a fault occurs at the end of the protection range concerned during fixed value setting.

[0057] In yet another aspect, the present invention further provides a computing device, comprising: one or more processors;

[0058] a processor for executing one or more programs;

[0059] When the one or more programs are executed by the one or more processors, the above-described method is implemented.

[0060] In yet another aspect, the present invention further provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed, the method described above is implemented.

[0061] Compared with the prior art, the present invention has the following beneficial effects:

[0062] The present invention provides a method for evaluating the adaptive boundary of distributed photovoltaic access protection, including: determining the main impact of the distributed photovoltaic access on the staged overcurrent protection, and determining the adaptive boundary analysis principle of the distributed photovoltaic access; based on the adaptive boundary analysis principle, determining the distributed photovoltaic access capacity boundary under the main impact; taking the intersection of the distributed photovoltaic access capacity boundary under the main impact as the adaptive boundary of the distributed photovoltaic access protection. The present invention can clarify the distributed photovoltaic access boundary under the constraints of the existing protection configuration, and clarify when the existing protection configuration needs to adjust the protection setting or optimize the protection principle. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 is a flow chart of the method of the present invention;

[0064] Figure 2 A schematic diagram of the comprehensive impact of photovoltaic access capacity constraints in an embodiment of the method of the present invention;

[0065] Figure 3 A relationship diagram between the maximum access capacity of all other branch distributed power sources of the bus and the main transformer and line parameters under the boosting effect of the method embodiment of the present invention;

[0066] Figure 4 A distributed power access capacity boundary diagram required when the main feeder protection of the method embodiment of the present invention refuses to operate due to being not affected by the draw-out;

[0067] Figure 5 A distributed power access capacity boundary diagram required when the protection of the method embodiment of the present invention is not affected by reverse overcurrent and malfunctions;

[0068] 6(a)-(c) are schematic diagrams showing the influence of different effects on distributed power sources in an embodiment of the method of the present invention;

[0069] 7(a)-(c) are comparison diagrams of the theoretical boundary of protection adaptability and simulation results under different effects of the embodiment of the method of the present invention;

[0070] Figure 8 It is a structural diagram of the system of the present invention. DETAILED DESCRIPTION

[0071] Now, exemplary embodiments of the present invention are described with reference to the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to disclose the present invention in detail and completely and to fully convey the scope of the present invention to those skilled in the art. The terms used in the exemplary embodiments shown in the accompanying drawings are not intended to limit the present invention. In the accompanying drawings, the same units / elements are marked with the same reference numerals.

[0072] Unless otherwise specified, the terms (including technical terms) used herein have the commonly understood meanings to those skilled in the art. In addition, it is understood that the terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

[0073] Embodiment 1:

[0074] The present invention proposes a method for evaluating the adaptive boundary of distributed photovoltaic access protection, such as Figure 1 As shown, including:

[0075] Step 1: determine the main impact of the distributed photovoltaic access on the staged overcurrent protection, and determine the adaptive boundary analysis principle of the distributed photovoltaic access;

[0076] Step 2: Based on the access adaptability boundary analysis principle, determine the distributed photovoltaic access capacity boundary under the main influence;

[0077] Step 3: Take the intersection of the distributed photovoltaic access capacity boundaries under the main influence as the distributed photovoltaic access protection adaptability boundary.

[0078] Among them, the main influences include: photovoltaic boosting effect, photovoltaic extraction effect and reverse overcurrent effect.

[0079] Among them, the access adaptability boundary analysis principles of distributed photovoltaics include: taking the photovoltaic short-circuit current as the scenario with the greatest impact, taking the photovoltaic access location as the scenario with the greatest impact, and taking the protection setting value as the boundary value within the allowable range.

[0080] Among them, based on the access adaptability boundary analysis principle, the distributed photovoltaic access capacity boundary under the main influence of photovoltaic boosting is determined, including:

[0081] In view of the photovoltaic boosting effect, the I-stage of the overcurrent protection of each outgoing line outlet, which has a substantial impact on the protection selectivity, is set to the I-stage fixed value, so that when a three-phase short-circuit fault occurs at a distance of l1 from the busbar, the maximum short-circuit current provided by the main power supply and distributed photovoltaic power generation does not exceed the I-stage protection fixed value, which is used as the boundary analysis constraint condition under the photovoltaic boosting effect;

[0082] Among them, based on the access adaptability boundary analysis principle, the distributed photovoltaic access capacity boundary under the main influence of photovoltaic boosting is determined, including:

[0083] For the photovoltaic boosting effect, the I section of the overcurrent protection of each outlet, which has a substantial impact on the protection selectivity, is set as the boundary analysis constraint condition under the photovoltaic boosting effect. When a three-phase short-circuit fault occurs at the farthest position allowed by the I section protection range, the maximum short-circuit current provided by the main grid power supply and distributed photovoltaic power generation does not exceed the I section protection setting value, which is used as the boundary analysis constraint condition under the photovoltaic boosting effect.

[0084] Under the boundary analysis constraint conditions under the photovoltaic boost effect, the distributed photovoltaic access capacity boundary under the main influence of photovoltaic boost effect is determined, and the calculation formula is as follows:

[0085]

[0086] in, and The calculation formula is as follows:

[0087]

[0088] Among them, S DG is the total capacity of distributed power sources connected to other lines on the bus, S T is the capacity of the system main transformer, Z T is the transformer impedance, |Z T | is the transformer impedance amplitude, is the per unit value of transformer impedance, is the magnitude of the transformer impedance per unit value, Z L is the line unit impedance, It is the sum of the transformer impedance and the line impedance within the protection range of the I-stage protection setting target. is the sum of the transformer impedance and the line impedance within the farthest protection range allowed by section I, θ1 and θ2 are Z T and Z L The impedance angle, c is the voltage coefficient;

[0089] The value range of c is 1.0-1.1, the value of θ1 is 90°, and the value of θ2 is 0°-90°.

[0090] According to the approximate relationship between the distribution network conductor parameters, current carrying capacity and system capacity, θ2 and S are obtained. T ,θ2 and S T The calculation formula is as follows:

[0091]

[0092] Based on the access adaptability boundary analysis principle, the distributed photovoltaic access capacity boundary under the main influence of photovoltaic extraction is determined, including:

[0093] When a two-phase short-circuit fault occurs at the end of the protection range, under the combined influence of the main grid power supply and all distributed photovoltaics connected within the protection range, the short-circuit current flowing through the protection is not less than the protection setting value, which is used as the boundary analysis constraint condition under the photovoltaic extraction effect;

[0094] Under the boundary analysis constraint conditions under the photovoltaic draw-out effect, the distributed photovoltaic access capacity boundary under the main influence of photovoltaic draw-out is determined, and the calculation formula is as follows:

[0095]

[0096] Among them, S DG is the total capacity of distributed power sources connected to other lines on the bus, U n is the amplitude of the system rated phase voltage, K sen is the sensitivity coefficient, Z BtoDG is the impedance from the bus to the centralized access point of the distributed generation, Z DGtof is the impedance from the centralized access point of the distributed generation to the fault point, Z T is the transformer impedance and c is the voltage coefficient.

[0097] Among them, based on the access adaptability boundary analysis principle, the distributed photovoltaic access capacity boundary under the main influence of reverse overcurrent is determined, including:

[0098] When the upstream line fails, the maximum short-circuit current provided by the distributed photovoltaic power generation shall not exceed the fixed value of section III as the boundary analysis constraint condition under the reverse overcurrent action;

[0099] Under the boundary analysis constraint conditions under the reverse overcurrent effect, the distributed photovoltaic access capacity boundary under the main influence of reverse overcurrent is determined, and the calculation formula is as follows:

[0100]

[0101] Among them, S DG is the total capacity of distributed power sources connected to other lines on the bus, U n is the amplitude of the system rated phase voltage, K sen is the sensitivity coefficient, c is the voltage coefficient, Z tot It is the sum of the loop impedances from the main grid power supply to the fault point after a fault occurs at the end of the protection range concerned during fixed value setting.

[0102] The present invention is further described below in conjunction with specific implementation cases:

[0103] Considering the operational stability and safety of the distribution network, the existing distribution network has an upper limit on the load of distributed photovoltaic access. Factors affecting this upper limit include protection adaptability, voltage stability, transformer capacity, power quality, etc. This invention only evaluates the adaptability boundary of protection for distributed photovoltaic access from the perspective of protection expertise, that is, the maximum photovoltaic access capacity that does not cause protection erroneous operation, providing a reference for protection optimization and new energy access.

[0104] The impact of distributed photovoltaic access on staged overcurrent protection is mainly manifested in three aspects: boost, drain and reverse overcurrent. Figure 2 The figure shows a schematic diagram of the comprehensive impact of the photovoltaic access capacity constraint range. Based on this, the present invention introduces the adaptive boundary engineering calculation method of the protection affected by the above three aspects obtained by the present invention based on the above analysis principles:

[0105] (A) Principles for adaptive boundary analysis of protection for PV access:

[0106] The topology of the distribution network is changeable, the distributed photovoltaic access is flexible, and the protection configuration setting varies greatly. Therefore, the conclusions of the protection adaptability analysis carried out in a specific scenario are limited. In actual application, due to the differences in scenarios, modeling simplification, calculation deviation and other issues, there will be a risk of boundary breakthrough. In order to obtain the real boundary of the distributed photovoltaic access capacity with a known protection configuration under a reasonable margin, this paper proposes several principles that should be followed in the protection adaptability boundary analysis:

[0107] ① The photovoltaic short-circuit current takes the scenario with the greatest impact. Specifically, there are three aspects: First, the photovoltaic short-circuit current only considers the two situations of "reaching the current limit value" and "zero output", and takes the combined scenario with the greatest impact when multiple photovoltaics upstream and downstream produce superimposed effects; second, the phase relationship between the main grid power supply short-circuit current and the photovoltaic overall output short-circuit current only considers the two situations of "same phase" or "opposite phase"; third, it is assumed that the load does not consume the power generated by the photovoltaic after the fault.

[0108] ② The photovoltaic access location is selected in the scenario with the greatest impact. Due to the shunting effect, only part of the photovoltaic output current after the fault affects the original current flowing through the protection. Therefore, when the photovoltaics are concentratedly connected to a certain place, so that the current shunted to the protection is the largest, it is the access location scenario with the greatest impact under the same photovoltaic access capacity.

[0109] ③ The protection setting value is taken to the boundary value within the allowable range. The three-stage setting value of overcurrent protection has room for adjustment according to the actual situation, but the relevant standards and protection setting procedures have minimum requirements for the protection range and setting sensitivity. This is used as the boundary of the protection setting value to analyze the adaptability to distributed photovoltaic access.

[0110] (B) Evaluation of distributed photovoltaic access capacity boundary considering photovoltaic boosting effect:

[0111] B1) Since the upper and lower level II and III protections are coordinated through the action delay level difference, the boosting effect will not cause the upper level protection to trip. Therefore, the distributed photovoltaic boosting has a substantial impact on the protection selectivity of the I stage of the overcurrent protection of each outlet.

[0112] In the existing setting regulations, there are two methods for setting the setting value of the outgoing line protection stage I:

[0113] ① "Set according to the maximum three-phase short-circuit current at the end of the protection range of this level, and the reliability coefficient shall not be less than 1.3."

[0114] ② "The I section protection zone should be shortened as much as possible to ensure that the three-phase short-circuit sensitivity of the switch outlet is not less than 1.0 under normal operating conditions."

[0115] When setting according to the standard in ①, sometimes the bus outlet fault sensitivity cannot be guaranteed due to the short line. At the same time, in order to avoid the I section protection range extending too far and causing overstep tripping when the branch line within the range fails, the actual project outgoing line I section is usually set according to ②, and the protection range is the bus outlet l set In order to accurately reflect the actual system operating conditions and protection requirements, the boundary analysis constraint condition is "when a three-phase short-circuit fault occurs at a distance of l1 from the busbar, the maximum short-circuit current provided by the main grid power supply and distributed photovoltaic power generation does not exceed the I-stage protection setting value".

[0116] B2) The access capacity boundary evaluation formula considering the photovoltaic boosting effect proposed in the present invention is as follows:

[0117]

[0118] In the formula, S DG The total capacity of distributed power sources connected to other lines on the bus; S T is the main transformer capacity of the system; |Z T | is the transformer impedance amplitude; is the per unit value of the transformer impedance, is its amplitude. c is the voltage coefficient, which is generally 1.0 to 1.1.

[0119] And in formula (1):

[0120]

[0121] Where: z L is the line unit impedance; θ1 and θ2 are Z T and z L The impedance angle is generally θ1=90°, 0°<θ2<90°.

[0122] Table 1 (parameters of 10kV overhead lines of different specifications (JKLGYJ) and their corresponding relationship with the capacity of the main transformer) The corresponding relationship between the unit impedance and the impedance angle reflected by the lines of different specifications, as well as the approximate matching level of the current carrying capacity corresponding to the unit resistance and the capacity of the main transformer, are organized to establish the fitting function θ2=f(|z L |)(unit: °) and S T =g(|r L |)=g(|z L |·cos(θ2))(unit: MVA). Through mathematical fitting, we get:

[0123]

[0124] It can be seen that when |z L |After knowing, θ2 and S T It is known that further Knowing can get |Z T |, so all the parameters on the right side of the inequality sign in equation (1) are known, that is, S DG The maximum boundary of can be solved.

[0125] Table 1

[0126]

[0127] B3) Figure 3 The fixed value protection range of section I is l set When the protection line exit is set at 4 km and the protection range is required to be expanded to a maximum of 5 km and 4.5 km under the influence of auxiliary increase, S DG.max / S T It can be seen that the obtained distributed generation access capacity boundary changes with the line unit impedance |z L | increases, the distance between the protection and the busbar increases, and is basically not affected by the transformer impedance per unit value. The specific boundary value conclusions are as follows: when l1 does not exceed 5km and 4.5km, the maximum access capacity of distributed power sources of any n-1 outgoing lines (n represents the total number of outgoing lines of the substation busbar) cannot exceed 87.8% and 43.9% of the main transformer capacity respectively, and Take the maximum value of a |z L |Get the boundary value.

[0128] (C) Distributed PV access capacity boundary assessment considering PV extraction:

[0129] C1) When there is photovoltaic access between any level of protection and the fault point, its operating performance may be affected by the mutual cancellation of photovoltaic output current and main grid short-circuit current at the protection position. The closer the protection is to the end of the line, the smaller the action setting is, and the more susceptible it is to the pull-out effect. Assuming that only the outgoing line protection is put into section I, and the other feeder switch protections are all out of service, the pull-out effect mainly affects sections II and III of each level of protection. In general, the protection is more affected by the pull-out effect during asymmetric faults, so the distributed power access capacity boundary obtained from the asymmetric fault analysis should be used as the standard. Systems with a high proportion of distributed power access are generally not in core urban areas, and the neutral point grounding method is a small current grounding method, so only two-phase phase-to-phase faults need to be considered.

[0130] In order to accurately reflect the actual system operating conditions and protection requirements, the present invention takes "when a two-phase short-circuit fault occurs at the end of the protection range, under the joint influence of the main grid power supply and all distributed photovoltaics connected within the protection range, the short-circuit current flowing through the protection is not lower than the protection set value" as the boundary analysis constraint condition.

[0131] C2) The access capacity boundary evaluation formula considering the photovoltaic extraction effect proposed in the present invention is as follows:

[0132]

[0133] In the formula, is the system rated phase voltage, and its amplitude is expressed as U n ; K sen is the sensitivity coefficient; Z BtoDG is the impedance from the bus to the centralized access point of the distributed generation; Z DGtof It is the impedance from the centralized access point of the distributed generation to the fault point.

[0134] According to different setting principles, fault locations and distributed photovoltaic access, min{K sen}、Z DGtof and Z BtoDG The actual parameters can be substituted into the distributed generation capacity boundary to solve it.

[0135] C3) Figure 4 The distributed generation access capacity boundary required when the main feeder protection is not affected by the extraction and refuses to operate, and the adaptability boundary of the protection to the distributed photovoltaic access capacity is obtained as the line unit impedance |z L | increases, the distance between the protection and the busbar increases, and is basically not affected by the transformer impedance per unit value. For the protection at 0km, 5km, 10km and 15km from the bus outlet, if the sensitivity coefficient is set to not less than 1.5 when the minimum short-circuit current at the end of the line is faulty, the total capacity of distributed photovoltaic power generation that can be connected to the line is 5.9-45.9MW (values ​​vary with |z L | decreases and increases, the same below), 4.0~31.5MW, 3.0~24MW and 2.4~19.4MW ( Figure 4 a); To ensure the remote backup function of the protection, "the sensitivity coefficient is set to no less than 1.2 when the minimum short-circuit current at the end of the lower line is faulty", the total distributed photovoltaic capacity that can be connected to the protection line at 0km, 5km, 10km and 15km from the bus outlet is 1.5~5.8MW, 1.2~5.2MW, 1.0~4.7MW and 0.9~4.3MW respectively ( Figure 4 b).

[0136] (D) Distributed photovoltaic access capacity boundary assessment considering photovoltaic reverse overcurrent effect:

[0137] D1) When a certain level of protection fails upstream, if the downstream photovoltaic capacity is large, the amplitude of the reverse fault current may exceed the protection setting, causing the protection to malfunction. The closer the protection is to the end and the smaller the current setting is, the greater the possibility of malfunction, which generally occurs in branch or boundary overcurrent protection. In order to accurately reflect the actual system operating conditions and protection requirements, "the maximum short-circuit current provided by distributed photovoltaics when the upstream protection line fails does not exceed the setting of section III" is used as the boundary analysis constraint.

[0138] D2) The access capacity boundary evaluation formula considering the photovoltaic reverse overcurrent effect proposed in the present invention is as follows:

[0139]

[0140] Where: Z tot It is the sum of the loop impedance from the main power supply to the fault point after a fault occurs at the end of the protection range concerned during the setting (considering the III section setting principle, the protection range is the lower line), that is, Z tot =Z T +Z Btof .

[0141] D3) Figure 5 In order to protect the distributed power access capacity boundary required by the faulty operation caused by reverse overcurrent, the setting principle of the remote backup function of the current segment III to protect the lower-level line is used as the basis for setting the fixed value. The distributed photovoltaic access capacity boundary obtained increases with the line unit impedance |z L | increases, the distance between the protection and the busbar increases, and is basically not affected by the transformer impedance per unit value. Taking the protection of 0km, 5km, 10km and 15km from the bus outlet as an example, the distributed photovoltaic capacity of all downstream lines that can be adapted is 7.4~28.4MW (the value varies with |z L |decreases and increases, the same below), 5.0~23.2MW, 3.8~19.6MW and 3.1~17.0MW.

[0142] (E) In general, the accessible capacity of distributed photovoltaics under the resulting protection constraints is achieved when all the above boundary conditions are met simultaneously, including but not limited to: maximum photovoltaic output, centralized access to distributed photovoltaics, currents flowing into the fault point from both sides of the fault point in phase, and all photovoltaic output currents flowing into the fault point without loss.

[0143] Therefore, in actual scenarios, the distributed photovoltaic access capacity proposed by the present invention has a certain reasonable margin. In practical applications, as long as the total distributed photovoltaic access capacity does not exceed the calculated boundary value, it will not cause protection malfunction or refusal to operate under any circumstances.

[0144] A 10kV distribution system was built in PSCAD, and distributed photovoltaics were connected at different locations and faults were set at different locations. The output phase of the distributed photovoltaic short-circuit current was adjusted, and the maximum impact caused by the access of distributed photovoltaics was simulated as much as possible in the simulation. Among them, the per-unit value of the main transformer impedance amplitude was 0.2, and the photovoltaic adopted the PQ control strategy and had the voltage ride-through control function.

[0145] For the adaptive boundary case analysis of protection under the effect of boosting, a distribution network as shown in Figure 6(a) is constructed in PSCAD, and the line unit impedance |z is adjusted. L |, according to the mathematical fitting formula (3), the corresponding line unit resistance and reactance and transformer capacity can be calculated and set in PSCAD. The target protection range of the outgoing line protection is set to 1km, and the protection setting value of stage I can be obtained by simulation when the distributed photovoltaic is not connected. Set the protection range of protection K1 to be expanded to 1.5km. After the distributed photovoltaic is connected and a three-phase metallic short circuit occurs 1.5km away from the bus, the current flowing from the distributed photovoltaic to the fault point increases the current measured by the protection K1, thereby expanding the protection range of the outgoing line protection K1, increasing the access capacity of the distributed photovoltaic so that the current flowing through the outgoing line protection reaches the protection setting value. At this time, the access capacity of the distributed photovoltaic is the access capacity boundary under the auxiliary effect in the current scenario. Change the active and reactive output ratio of the distributed photovoltaic to adjust the output current phase and repeat the above simulation. The simulation boundary results under each scenario are shown in Figure 7(a).

[0146] For the adaptive boundary case analysis of protection under the action of extraction, the distribution network shown in Figure 6(b) is built in PSCAD. The system parameters are the same as the adaptive boundary case analysis under the action of boosting, and the set value of section III is set according to the 1.2 times sensitivity of the fault at the end of the lower line. The set value of section III of the outgoing line protection K1 can be obtained through simulation. When distributed photovoltaic is connected and a two-phase short circuit fault occurs at the end f3 of the lower line of protection K1, the current flowing from distributed photovoltaic to the main grid will cause the current measured by protection K1 to decrease, thereby reducing the protection range. Increasing the access capacity of distributed photovoltaic makes the current measured by protection K1 decrease to a fixed value. At this time, the distributed photovoltaic capacity is the adaptive boundary of the protection under the action of extraction in the current scenario. Similarly, the phase of the distributed photovoltaic output current is adjusted and the above simulation is repeated. The simulation boundary results under each scenario are shown in Figure 7(b).

[0147] For the adaptive boundary case analysis of protection under reverse overcurrent, a distribution network as shown in Figure 6(c) is built in PSCAD. The system parameters are the same as the adaptive boundary case analysis under the auxiliary effect, and the III section constant is set according to the 1.2 times sensitivity of the downstream line end fault. When distributed photovoltaic access and a fault occurs upstream of the segment protection K2, the distributed photovoltaic access capacity is increased to make the protection K2 reverse action. At this time, the distributed photovoltaic capacity is the access capacity boundary under reverse overcurrent in the current scenario as shown in Figure 7(c).

[0148] In the actual simulation process, the phase relationship between the short-circuit current output by distributed photovoltaics and the main grid is affected by many factors such as control strategy, load connection, line parameters, fault location, etc. The short-circuit current phase change caused by the above factors is simulated by changing the proportional control of the active and reactive power of distributed photovoltaics. From the comparison of simulation results, it can be seen that all simulation boundary capacities are above the theoretical boundary and close to the theoretical boundary value, which proves the effectiveness of the adaptive boundary analysis method of the protection of the present invention. In practical applications, as long as the total capacity of distributed photovoltaic access does not exceed the theoretical calculated boundary value, it will not cause the distribution network current protection to malfunction or refuse to operate.

[0149] Embodiment 2:

[0150] The present invention also proposes a system 200 for evaluating the adaptive boundary of distributed photovoltaic access protection, such as Figure 8 As shown, including:

[0151] Initial unit 201, used to determine the main impact of the distributed photovoltaic access on the staged overcurrent protection, and determine the adaptive boundary analysis principle of the distributed photovoltaic access;

[0152] A calculation unit 202 is used to determine the distributed photovoltaic access capacity boundary under the main influence based on the access adaptability boundary analysis principle;

[0153] The evaluation unit 203 is used to obtain the intersection of the distributed photovoltaic access capacity boundaries under the main influence as the distributed photovoltaic access protection adaptability boundary.

[0154] Among them, the main influences include: photovoltaic boosting effect, photovoltaic extraction effect and reverse overcurrent effect.

[0155] Among them, the access adaptability boundary analysis principles of distributed photovoltaics include: taking the photovoltaic short-circuit current as the scenario with the greatest impact, taking the photovoltaic access location as the scenario with the greatest impact, and taking the protection setting value as the boundary value within the allowable range.

[0156] The calculation unit 201 determines the distributed photovoltaic access capacity boundary under the main influence of photovoltaic boosting based on the access adaptability boundary analysis principle, including:

[0157] For the photovoltaic boosting effect, the I section of the overcurrent protection of each outlet, which has a substantial impact on the protection selectivity, is set as the boundary analysis constraint condition under the photovoltaic boosting effect. When a three-phase short-circuit fault occurs at the farthest position allowed by the I section protection range, the maximum short-circuit current provided by the main grid power supply and distributed photovoltaic power generation does not exceed the I section protection setting value, which is used as the boundary analysis constraint condition under the photovoltaic boosting effect.

[0158] Under the boundary analysis constraint conditions under the photovoltaic boost effect, the distributed photovoltaic access capacity boundary under the main influence of photovoltaic boost effect is determined, and the calculation formula is as follows:

[0159]

[0160] in, and The calculation formula is as follows:

[0161]

[0162] Among them, S DG is the total capacity of distributed power sources connected to other lines on the bus, S T is the capacity of the system main transformer, Z T is the transformer impedance, |Z T | is the transformer impedance amplitude, is the per unit value of transformer impedance, is the magnitude of the transformer impedance per unit value, Z L is the line unit impedance, It is the sum of the transformer impedance and the line impedance within the protection range of the I-stage protection setting target. is the sum of the transformer impedance and the line impedance within the farthest protection range allowed by section I, θ1 and θ2 are Z T and Z L The impedance angle, c is the voltage coefficient;

[0163] The value range of c is 1.0-1.1, the value of θ1 is 90°, and the value of θ2 is 0°-90°.

[0164] The calculation unit 202 obtains θ2 and S according to the approximate correlation between the distribution network conductor parameters and the current carrying capacity and system capacity. T ,θ2 and S T The calculation formula is as follows:

[0165]

[0166] The calculation unit 202 determines the distributed photovoltaic access capacity boundary under the main influence of photovoltaic extraction based on the access adaptability boundary analysis principle, including:

[0167] When a two-phase short-circuit fault occurs at the end of the protection range, under the combined influence of the main grid power supply and all distributed photovoltaics connected within the protection range, the short-circuit current flowing through the protection is not less than the protection setting value, which is used as the boundary analysis constraint condition under the photovoltaic extraction effect;

[0168] Under the boundary analysis constraint conditions under the photovoltaic draw-out effect, the distributed photovoltaic access capacity boundary under the main influence of photovoltaic draw-out is determined, and the calculation formula is as follows:

[0169]

[0170] Among them, S DG is the total capacity of distributed power sources connected to other lines on the bus, U n is the amplitude of the system rated phase voltage, K sen is the sensitivity coefficient, Z BtoDG is the impedance from the bus to the centralized access point of the distributed generation, Z DGtof is the impedance from the centralized access point of the distributed generation to the fault point, Z T is the transformer impedance and c is the voltage coefficient.

[0171] Among them, based on the access adaptability boundary analysis principle, the distributed photovoltaic access capacity boundary under the main influence of reverse overcurrent is determined, including:

[0172] When the upstream line fails, the maximum short-circuit current provided by the distributed photovoltaic power generation shall not exceed the fixed value of section III as the boundary analysis constraint condition under the reverse overcurrent action;

[0173] Under the boundary analysis constraint conditions under the reverse overcurrent effect, the distributed photovoltaic access capacity boundary under the main influence of reverse overcurrent is determined, and the calculation formula is as follows:

[0174]

[0175] Among them, S DG is the total capacity of distributed power sources connected to other lines on the bus, U n is the amplitude of the system rated phase voltage, K sen is the sensitivity coefficient, c is the voltage coefficient, Z tot It is the sum of the loop impedances from the main power supply to the fault point after a fault occurs at the end of the protection range concerned during fixed value setting.

[0176] The present invention can clarify the distributed photovoltaic access boundary under the constraints of the existing protection configuration, and make it clear when the existing protection configuration needs to adjust the protection setting value or optimize the protection principle.

[0177] Embodiment 3:

[0178] Based on the same inventive concept, the present invention also provides a computer device, which includes a processor and a memory, wherein the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, and is specifically suitable for loading and executing one or more instructions in the computer storage medium to implement the corresponding method flow or corresponding functions, so as to implement the steps of the method in the above embodiment.

[0179] Embodiment 4:

[0180] Based on the same inventive concept, the present invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device for storing programs and data. It is understandable that the computer-readable storage medium here can include both a built-in storage medium in a computer device and an extended storage medium supported by the computer device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by a processor are also stored in the storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of the method in the above embodiment.

[0181] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes. The schemes in the embodiments of the present invention may be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0182] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0183] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0184] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0185] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0186] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for evaluating the adaptive boundary of distributed photovoltaic access protection, characterized in that: include: Determine the main impact of the distributed photovoltaic access on the staged overcurrent protection, and determine the adaptive boundary analysis principle of the distributed photovoltaic access; Based on the access adaptability boundary analysis principle, determine the distributed photovoltaic access capacity boundary under the main influence; The intersection of the distributed photovoltaic access capacity boundaries under the main influences is taken as the distributed photovoltaic access protection adaptability boundary.

2. The method according to claim 1, characterized in that The main effects include: photovoltaic boosting effect, photovoltaic extraction effect and reverse overcurrent effect.

3. The method according to claim 1, characterized in that The distributed photovoltaic access adaptability boundary analysis principle includes: the photovoltaic short-circuit current takes the scenario with the greatest impact, the photovoltaic access location takes the scenario with the greatest impact, and the protection setting value takes the boundary value within the allowable range.

4. The method according to claim 1, characterized in that Based on the access adaptability boundary analysis principle, the distributed photovoltaic access capacity boundary under the main influence of photovoltaic boosting is determined, including: For the photovoltaic boosting effect, the I section of the overcurrent protection of each outlet, which has a substantial impact on the protection selectivity, is set as the boundary analysis constraint condition under the photovoltaic boosting effect. When a three-phase short-circuit fault occurs at the farthest position allowed by the I section protection range, the maximum short-circuit current provided by the main grid power supply and distributed photovoltaic power generation does not exceed the I section protection setting value, which is used as the boundary analysis constraint condition under the photovoltaic boosting effect. Under the boundary analysis constraint conditions under the photovoltaic boost effect, the distributed photovoltaic access capacity boundary under the main influence of photovoltaic boost effect is determined, and the calculation formula is as follows: in, and The calculation formula is as follows: Among them, S DG is the total capacity of distributed power sources connected to other lines on the bus, S T is the capacity of the system main transformer, Z T is the transformer impedance, |Z T | is the transformer impedance amplitude, is the per unit value of transformer impedance, is the magnitude of the transformer impedance per unit value, Z L is the line unit impedance, It is the sum of the transformer impedance and the line impedance within the protection range of the I-stage protection setting target. is the sum of the transformer impedance and the line impedance within the farthest protection range allowed by section I, θ1 and θ2 are Z T and Z L The impedance angle, c is the voltage coefficient; The value range of c is 1.0-1.1, the value of θ1 is 90°, and the value of θ2 is 0°-90°.

5. The method according to claim 4, characterized in that According to the approximate relationship between the distribution network conductor parameters, current carrying capacity and system capacity, θ2 and S are obtained. T ,θ2 and S T The calculation formula is as follows:

6. The method according to claim 1, characterized in that Based on the access adaptability boundary analysis principle, the distributed photovoltaic access capacity boundary under the main influence of photovoltaic extraction is determined, including: When a two-phase short-circuit fault occurs at the end of the protection range, under the combined influence of the main grid power supply and all distributed photovoltaics connected within the protection range, the short-circuit current flowing through the protection is not less than the protection setting value, which is used as the boundary analysis constraint condition under the photovoltaic extraction effect; Under the boundary analysis constraint conditions under the photovoltaic draw-out effect, the distributed photovoltaic access capacity boundary under the main influence of photovoltaic draw-out is determined, and the calculation formula is as follows: Among them, S DG is the total capacity of distributed power sources connected to other lines on the bus, U n is the amplitude of the system rated phase voltage, K sen is the sensitivity coefficient, Z BtoDG is the impedance from the bus to the centralized access point of the distributed generation, Z DGtof is the impedance from the centralized access point of the distributed generation to the fault point, Z T is the transformer impedance and c is the voltage coefficient.

7. The method according to claim 1, characterized in that Based on the access adaptability boundary analysis principle, the distributed photovoltaic access capacity boundary under the main influence of reverse overcurrent is determined, including: When the upstream line fails, the maximum short-circuit current provided by the distributed photovoltaic power generation shall not exceed the fixed value of section III as the boundary analysis constraint condition under the reverse overcurrent action; Under the boundary analysis constraint conditions under the reverse overcurrent effect, the distributed photovoltaic access capacity boundary under the main influence of reverse overcurrent is determined, and the calculation formula is as follows: Among them, S DG is the total capacity of distributed power sources connected to other lines on the bus, U n is the amplitude of the system rated phase voltage, K sen is the sensitivity coefficient, c is the voltage coefficient, Z tot It is the sum of the loop impedances from the main grid power supply to the fault point after a fault occurs at the end of the protection range concerned during fixed value setting.

8. A system for distributed photovoltaic access protection adaptability boundary assessment, characterized in that: include: An initial unit, used to determine the main impact of the distributed photovoltaic access on the staged overcurrent protection, and determine the adaptive boundary analysis principle of the distributed photovoltaic access; A calculation unit, used to determine the distributed photovoltaic access capacity boundary under the main influence based on the access adaptability boundary analysis principle; The evaluation unit is used to take the intersection of the distributed photovoltaic access capacity boundaries under the main influence as the distributed photovoltaic access protection adaptability boundary.

9. The system according to claim 8, characterized in that The main effects include: photovoltaic boosting effect, photovoltaic extraction effect and reverse overcurrent effect.

10. The system according to claim 8, characterized in that The distributed photovoltaic access adaptability boundary analysis principle includes: the photovoltaic short-circuit current takes the scenario with the greatest impact, the photovoltaic access location takes the scenario with the greatest impact, and the protection setting value takes the boundary value within the allowable range.

11. The system according to claim 8, characterized in that The calculation unit determines the distributed photovoltaic access capacity boundary under the main influence of photovoltaic auxiliary effect based on the access adaptability boundary analysis principle, including: For the photovoltaic boosting effect, the I section of the overcurrent protection of each outlet, which has a substantial impact on the protection selectivity, is set as the boundary analysis constraint condition under the photovoltaic boosting effect. When a three-phase short-circuit fault occurs at the farthest position allowed by the I section protection range, the maximum short-circuit current provided by the main grid power supply and distributed photovoltaic power generation does not exceed the I section protection setting value, which is used as the boundary analysis constraint condition under the photovoltaic boosting effect. Under the boundary analysis constraint conditions under the photovoltaic boost effect, the distributed photovoltaic access capacity boundary under the main influence of photovoltaic boost effect is determined, and the calculation formula is as follows: Among them, Z lset and The calculation formula is as follows: Among them, S DG is the total capacity of distributed power sources connected to other lines on the bus, S T is the capacity of the system main transformer, Z T is the transformer impedance, |Z T | is the transformer impedance amplitude, is the per unit value of transformer impedance, is the magnitude of the transformer impedance per unit value, Z L is the line unit impedance, It is the sum of the transformer impedance and the line impedance within the protection range of the I-stage protection setting target. is the sum of the transformer impedance and the line impedance within the farthest protection range allowed by section I, θ1 and θ2 are Z T and Z L The impedance angle, c is the voltage coefficient; The value range of c is 1.0-1.1, the value of θ1 is 90°, and the value of θ2 is 0°-90°.

12. The system according to claim 11, characterized in that The calculation unit obtains θ2 and S according to the approximate correlation between the distribution network conductor parameters and the current carrying capacity and system capacity. T ,θ2 and S T The calculation formula is as follows:

13. The system according to claim 8, characterized in that The calculation unit determines the distributed photovoltaic access capacity boundary under the main influence of photovoltaic extraction based on the access adaptability boundary analysis principle, including: When a two-phase short-circuit fault occurs at the end of the protection range, under the combined influence of the main grid power supply and all distributed photovoltaics connected within the protection range, the short-circuit current flowing through the protection is not less than the protection setting value, which is used as the boundary analysis constraint condition under the photovoltaic extraction effect; Under the boundary analysis constraint conditions under the photovoltaic draw-out effect, the distributed photovoltaic access capacity boundary under the main influence of photovoltaic draw-out is determined, and the calculation formula is as follows: Among them, S DG is the total capacity of distributed power sources connected to other lines on the bus, U n is the amplitude of the system rated phase voltage, K sen is the sensitivity coefficient, Z BtoDG is the impedance from the bus to the centralized access point of the distributed generation, Z DGtof is the impedance from the centralized access point of the distributed generation to the fault point, Z T is the transformer impedance and c is the voltage coefficient.

14. The system according to claim 8, characterized in that Based on the access adaptability boundary analysis principle, the distributed photovoltaic access capacity boundary under the main influence of reverse overcurrent is determined, including: When the upstream line fails, the maximum short-circuit current provided by the distributed photovoltaic power generation shall not exceed the fixed value of section III as the boundary analysis constraint condition under the reverse overcurrent action; Under the boundary analysis constraint conditions under the reverse overcurrent effect, the distributed photovoltaic access capacity boundary under the main influence of reverse overcurrent is determined, and the calculation formula is as follows: Among them, S DG is the total capacity of distributed power sources connected to other lines on the bus, U n is the amplitude of the system rated phase voltage, K sen is the sensitivity coefficient, c is the voltage coefficient, Z tot It is the sum of the loop impedances from the main grid power supply to the fault point after a fault occurs at the end of the protection range concerned during fixed value setting.

15. A computer device, characterized in that: include: one or more processors; a processor for executing one or more programs; When the one or more programs are executed by the one or more processors, the method according to any one of claims 1 to 7 is implemented.

16. A computer-readable storage medium, characterized in that: A computer program is stored thereon, and when the computer program is executed, the method according to any one of claims 1 to 7 is implemented.

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