Distributed photovoltaic access protection adaptability boundary evaluation method and system considering increase assisting effect

Abstract

The invention discloses a distributed photovoltaic access protection adaptability boundary evaluation method and system considering an increase assisting effect, and belongs to the technical field of power distribution network protection. The method comprises the following steps: determining a distributed photovoltaic access adaptability boundary analysis principle; based on the access adaptive boundary analysis principle, determining a boundary analysis constraint condition of an access adaptive boundary under the photovoltaic boosting effect; and based on the boundary analysis constraint condition, determining a distributed photovoltaic access capacity boundary under the photovoltaic increase assisting effect. 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 for evaluating the adaptive boundary of distributed photovoltaic access protection under the consideration of boosting effect. 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 under the effect of auxiliary enhancement, including:

[0006] Determine the access adaptability boundary analysis principles for distributed photovoltaics;

[0007] Based on the access adaptability boundary analysis principle, determining the boundary analysis constraint conditions of the access adaptability boundary under the photovoltaic boosting effect;

[0008] Based on the boundary analysis constraints, the distributed photovoltaic access capacity boundary under the photovoltaic enhancement effect is determined.

[0009] 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.

[0010] Optionally, for the photovoltaic boosting effect, section I of the overcurrent protection of each outlet that has a substantial impact on the protection selectivity can be used as a boundary analysis constraint condition under the photovoltaic boosting effect, with the maximum short-circuit current provided by the main grid power supply and distributed photovoltaics not exceeding the section I protection setting when a three-phase short-circuit fault occurs at the farthest location allowed by the section I protection range.

[0011] Optionally, based on the boundary analysis constraint condition, a calculation formula for determining the distributed photovoltaic access capacity boundary under the photovoltaic boosting effect is as follows:

[0012]

[0013] in, and The calculation formula is as follows:

[0014]

[0015] 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;

[0016] The value range of c is 1.0-1.1, the value of θ1 is 90°, and the value of θ2 is 0°-90°.

[0017] 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:

[0018]

[0019] On the other hand, the present invention also proposes a system for evaluating the adaptive boundary of distributed photovoltaic access protection under the consideration of boosting effect, comprising:

[0020] Initial unit, used to determine the access adaptability boundary analysis principle of distributed photovoltaics;

[0021] A calculation unit, for determining a boundary analysis constraint condition of an access adaptability boundary under photovoltaic boosting based on the access adaptability boundary analysis principle;

[0022] An evaluation unit is used to determine the distributed photovoltaic access capacity boundary under the photovoltaic boosting effect based on the boundary analysis constraint condition.

[0023] 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.

[0024] Optionally, the calculation unit uses the I section of the overcurrent protection of each outgoing line outlet that has a substantial impact on the protection selectivity for the photovoltaic boosting effect, with the maximum short-circuit current provided by the main power supply and distributed photovoltaics not exceeding the I section protection setting when a three-phase short-circuit fault occurs at the farthest location allowed by the I section protection range, as a boundary analysis constraint condition under the photovoltaic boosting effect.

[0025] Optionally, based on the boundary analysis constraint condition, a calculation formula for determining the distributed photovoltaic access capacity boundary under the photovoltaic boosting effect is as follows:

[0026]

[0027] in, and The calculation formula is as follows:

[0028]

[0029] Among them, S DG is the total capacity of distributed power sources connected to other lines on the bus, ST 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;

[0030] The value range of c is 1.0-1.1, the value of θ1 is 90°, and the value of θ2 is 0°-90°.

[0031] 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:

[0032]

[0033] In yet another aspect, the present invention further provides a computing device, comprising: one or more processors;

[0034] a processor for executing one or more programs;

[0035] When the one or more programs are executed by the one or more processors, the above-described method is implemented.

[0036] 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.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The present invention provides a method for evaluating the adaptive boundary of distributed photovoltaic access protection under the effect of photovoltaic boosting, including: determining the adaptive boundary analysis principle of distributed photovoltaic access; based on the adaptive boundary analysis principle, determining the boundary analysis constraint of the adaptive boundary of access under the effect of photovoltaic boosting; based on the boundary analysis constraint, determining the distributed photovoltaic access capacity boundary under the effect of photovoltaic boosting. 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

[0039] Figure 1 is a flow chart of the method of the present invention;

[0040] Figure 2 A schematic diagram of the comprehensive impact of photovoltaic access capacity constraints in an embodiment of the method of the present invention;

[0041] 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;

[0042] Figure 4 A schematic diagram of the impact of distributed power supply in an embodiment of the method of the present invention;

[0043] Figure 5 A comparison diagram of the protection adaptability theoretical boundary and simulation results under the influence of the embodiment of the method of the present invention;

[0044] Figure 6 It is a structural diagram of the system of the present invention. DETAILED DESCRIPTION

[0045] 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.

[0046] 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.

[0047] Embodiment 1:

[0048] The present invention proposes a method for evaluating the adaptive boundary of distributed photovoltaic access protection under the consideration of auxiliary enhancement, such as Figure 1 As shown, including:

[0049] Step 1: Determine the access adaptability boundary analysis principle of distributed photovoltaics;

[0050] Step 2: Based on the access adaptability boundary analysis principle, determine the boundary analysis constraint conditions of the access adaptability boundary under the photovoltaic boosting effect;

[0051] Step 3: Based on the boundary analysis constraint conditions, determine the distributed photovoltaic access capacity boundary under the photovoltaic boosting effect.

[0052] 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.

[0053] Optionally, for the photovoltaic boosting effect, section I of the overcurrent protection of each outlet that has a substantial impact on the protection selectivity can be used as a boundary analysis constraint condition under the photovoltaic boosting effect, with the maximum short-circuit current provided by the main grid power supply and distributed photovoltaics not exceeding the section I protection setting when a three-phase short-circuit fault occurs at the farthest location allowed by the section I protection range.

[0054] Optionally, based on the boundary analysis constraint condition, a calculation formula for determining the distributed photovoltaic access capacity boundary under the photovoltaic boosting effect is as follows:

[0055]

[0056] in, and The calculation formula is as follows:

[0057]

[0058] 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;

[0059] The value range of c is 1.0-1.1, the value of θ1 is 90°, and the value of θ2 is 0°-90°.

[0060] 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:

[0061]

[0062] The present invention is further described below in conjunction with specific implementation cases:

[0063] 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.

[0064] 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:

[0065] (A) Principles for adaptive boundary analysis of protection for PV access:

[0066] 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:

[0067] 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.

[0068] 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.

[0069] 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.

[0070] (B) Evaluation of distributed photovoltaic access capacity boundary considering photovoltaic boosting effect:

[0071] 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.

[0072] In the existing setting regulations, there are two methods for setting the setting value of the outgoing line protection stage I:

[0073] 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."

[0074] 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."

[0075] 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".

[0076] B2) The access capacity boundary evaluation formula considering the photovoltaic boosting effect proposed in the present invention is as follows:

[0077]

[0078] 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.

[0079] And in formula (1):

[0080]

[0081] 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°.

[0082] 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:

[0083]

[0084] 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.

[0085] Table 1

[0086]

[0087] 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.

[0088] (C) In general, the accessible capacity of distributed photovoltaics under the resulting protection constraints is obtained when the above boundary conditions are met. Other conditions include but are 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.

[0089] 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.

[0090] 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.

[0091] For the case analysis of the adaptive boundary of protection under the effect of augmentation, the following Figure 4 The distribution network shown in the figure adjusts the line unit impedance |z L |, according to the mathematical fitting formula 5, the corresponding line unit resistance and reactance and transformer capacity can be calculated and set in PSCAD. Set the target protection range of the outgoing line protection to 1km, and the protection setting value of Section I can be obtained by simulation when the distributed photovoltaic is not connected. Set the protection range of protection K1 to be allowed to expand 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 to obtain the simulation boundary results under each scenario as shown below Figure 5 .

[0092] 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.

[0093] Embodiment 2:

[0094] The present invention also proposes a system 200 for evaluating the adaptive boundary of distributed photovoltaic access protection under the effect of boosting, such as Figure 6 As shown, including:

[0095] Initial unit 201, used to determine the access adaptability boundary analysis principle of distributed photovoltaics;

[0096] A calculation unit 202, for determining a boundary analysis constraint condition of an access adaptability boundary under the photovoltaic boosting effect based on the access adaptability boundary analysis principle;

[0097] The evaluation unit 203 is used to determine the distributed photovoltaic access capacity boundary under the photovoltaic boosting effect based on the boundary analysis constraint condition.

[0098] 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.

[0099] Among them, the calculation unit 202 uses the I section of the overcurrent protection of each outlet of each outgoing line that has a substantial impact on the protection selectivity for 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 power supply and distributed photovoltaics does not exceed the I section protection setting value, which serves as the boundary analysis constraint condition under the photovoltaic boosting effect.

[0100] Among them, based on the boundary analysis constraints, the calculation formula for determining the distributed photovoltaic access capacity boundary under the photovoltaic boost effect is as follows:

[0101]

[0102] in, and The calculation formula is as follows:

[0103]

[0104] 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;

[0105] The value range of c is 1.0-1.1, the value of θ1 is 90°, and the value of θ2 is 0°-90°.

[0106] 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:

[0107]

[0108] 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.

[0109] Embodiment 3:

[0110] 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.

[0111] Embodiment 4:

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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 in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0117] 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.

[0118] 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 under the effect of boosting, characterized in that: include: Determine the access adaptability boundary analysis principles for distributed photovoltaics; Based on the access adaptability boundary analysis principle, determining the boundary analysis constraint conditions of the access adaptability boundary under the photovoltaic boosting effect; Based on the boundary analysis constraints, the distributed photovoltaic access capacity boundary under the photovoltaic enhancement effect is determined.

2. 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.

3. The method according to claim 1, characterized in that In view of the photovoltaic boosting effect, the I section of the overcurrent protection of each outgoing line 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 power supply and distributed photovoltaics does not exceed the I section protection setting, which is used as the boundary analysis constraint condition under the photovoltaic boosting effect.

4. The method according to claim 1, characterized in that: Based on the boundary analysis constraint condition, the calculation formula for determining the distributed photovoltaic access capacity boundary under the photovoltaic boost effect 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 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; 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. A system for evaluating the adaptive boundary of distributed photovoltaic access protection under the effect of boosting, characterized in that: include: Initial unit, used to determine the access adaptability boundary analysis principle of distributed photovoltaics; A calculation unit, for determining a boundary analysis constraint condition of an access adaptability boundary under photovoltaic boosting based on the access adaptability boundary analysis principle; An evaluation unit is used to determine the distributed photovoltaic access capacity boundary under the photovoltaic boosting effect based on the boundary analysis constraint condition.

7. The system according to claim 6, 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.

8. The system according to claim 6, characterized in that The calculation unit takes the photovoltaic boosting effect as the boundary analysis constraint condition under the photovoltaic boosting effect, and takes the I section of the overcurrent protection of each outlet of the outgoing line which has a substantial impact on the protection selectivity as the boundary analysis constraint condition under the photovoltaic boosting effect, and takes the I section protection range as the maximum short-circuit current provided by the main grid power supply and the distributed photovoltaic power supply not exceeding the I section protection set value when a three-phase short-circuit fault occurs at the farthest position.

9. The system according to claim 6, characterized in that Based on the boundary analysis constraint condition, the calculation formula for determining the distributed photovoltaic access capacity boundary under the photovoltaic boost effect 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°.

10. The system according to claim 9, 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:

11. 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 5 is implemented.

12. 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 5 is implemented.

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