Transformer area distributed photovoltaic maximum accessible capacity analysis method considering voltage drop and load

Abstract

The invention discloses a transformer area distributed photovoltaic maximum accessible capacity analysis method considering voltage drop and load, and the method comprises the steps: firstly, carrying out the data collection of a source end; secondly, data cleaning is carried out, and correction of missing and abnormal data is achieved; thirdly, constructing a photovoltaic user equivalent model, simulating installation of the maximum accessible photovoltaic capacity, and carrying out load flow calculation; and finally, conducting wire current-carrying capacity analysis, user voltage difference analysis, reverse supply power analysis and photovoltaic power generation wire load rate analysis in sequence, eliminating related photovoltaic users, and completing calculation of the maximum photovoltaic access capacity of distribution room network frame optimization. According to the method, a simulation analysis model is automatically established based on the real condition of the transformer area, the transformer area is formed to generate reasonable return power under the condition that the access capacity of the transformer area is maximum by setting constraint conditions such as reverse power and wire load, meanwhile, the management work in the two aspects of line loss and voltage is met, and a specific photovoltaic access scheme is output; the method is used for guiding access of distributed light.

Description

Technical Field

[0001] The present invention relates to the field of power grids, and in particular to an analysis method for the maximum accessible capacity of distributed photovoltaic in a substation area considering voltage drop and load. Background Technique

[0002] Each power company actively promotes the construction of a new power system and increases the investment in renewable energy. Among them, distributed photovoltaic, as the main form of renewable energy, has seen a significant increase in the grid connection scale in recent years. However, the access of distributed photovoltaic has also had a greater impact on the planning, reliability, relay protection, and power quality of the distribution network. Therefore, how to reasonably connect distributed photovoltaic while ensuring the safe and stable operation of the power grid is the key and difficult point of current research.

[0003] At present, the analysis and measurement method for the maximum accessible capacity of distributed photovoltaic in a substation area relies on manual experience and roughly estimates the maximum accessible capacity with the goal of local consumption. Analyzing the current analysis and measurement method for the maximum accessible capacity of distributed photovoltaic in a substation area, the following main deficiencies exist:

[0004] First, the current evaluation strategy emphasizes consumption and neglects reverse power supply, resulting in a relatively small calculated value of the maximum accessible capacity, which does not meet the goal of vigorously developing clean energy. The local consumption of distributed photovoltaic in a substation area can reduce the losses in the substation area to a certain extent and lower the operating costs of power grid enterprises. However, aiming at local consumption often leads to a relatively small accessible photovoltaic capacity in the substation area, which is contrary to the goal of the country's vigorous development of clean energy.

[0005] Second, a complete measurement and evaluation system has not been formed, making it difficult to accurately calculate the maximum accessible capacity of distributed photovoltaic in a substation area. The current measurement method mainly relies on manual experience and can only make rough estimates, unable to comprehensively evaluate important parameters affecting photovoltaic installation such as the on-site environment of the substation area and the current operating status of the substation area, and the accuracy of the output results is not high. For this reason, we propose an analysis method for the maximum accessible capacity of distributed photovoltaic in a substation area considering voltage drop and load. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the existing defects, provide an analysis method for the maximum accessible capacity of distributed photovoltaic in a substation area considering voltage drop and load, respond to the goal of the country's vigorous development of clean energy while ensuring the safe and stable operation of the power grid, and provide scientific guidance for the reasonable access of distributed photovoltaic, which can effectively solve the problems in the background technique.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] An analysis method for the maximum accessible capacity of distributed photovoltaic in a substation area considering voltage drop and load, comprising the following steps:

[0009] Step S1: Conduct data collection at the source end, collecting multi-dimensional on-site data, including but not limited to substation topology, archives, operation data, and the installable PV access area of users.

[0010] Step S2: Perform data cleaning to correct missing and abnormal data.

[0011] Step S3: Build an equivalent model for PV users, simulate the installation of the maximum accessible PV capacity, and conduct power flow calculations.

[0012] Step S4: Conduct wire current-carrying capacity analysis, user voltage difference analysis, reverse power supply analysis, and PV power generation wire load rate analysis in sequence, eliminate relevant PV users, and complete the calculation of the maximum PV access capacity for substation network optimization.

[0013] Furthermore, a method for analyzing the maximum accessible capacity of distributed PV in a substation considering voltage drop and load specifically includes the following steps:

[0014] Step 1: Conduct data collection at the source end. The data includes but is not limited to the topology graph of the substation, basic parameters of substation equipment, power curves of typical PV users, roof areas of accessible PV users, area of a single PV panel, and capacity of a single PV panel.

[0015] Step 2: Perform data cleaning to determine whether the key data involved in the calculation is empty or abnormal.

[0016] Step 3: Conduct precondition judgment, perform power flow calculations on the initial substation and typical daily operation data, and exclude substations with voltage differences exceeding 4% or reverse loads exceeding 100% in the initial state.

[0017] Step 4: Calculate the PV power generation. Based on the roof areas of users with installable PV collected, calculate the number and capacity of PV panels that can be installed for each household, and combine with the typical PV load curves of the region collected to calculate the power generation data of PV users when PV is installed.

[0018] Step 5: Modify the data preparation for calculating the theoretical line loss of the substation. Based on the current situation of the substation topology graph, combine with the roof areas of users with installable PV, virtualize the electrical components of PV users, and simulate and build the substation topology graph after PV access.

[0019] First, add PV components in full quantity. Combine with the power curves of PV users deduced in Step 3 to conduct power flow calculations. Determine whether the power flow converges. If the power flow calculation converges, skip Step 6 and execute Step 7. If the power flow calculation does not converge, execute Step 6.

[0020] Step 6: Treatment of wire load rate. In the case of full-scale photovoltaic power, if the power flow calculation of the distribution area does not converge, judge whether the load rate of all terminal wires exceeds the wire current-carrying capacity after connecting photovoltaic power. If it exceeds the wire current-carrying capacity, judge the magnitude of the current generated by the photovoltaic users connected under this section of wire through simple measurement, and eliminate the photovoltaic users whose generated magnitude is close to the part of the current exceeding the wire current-carrying capacity. Then perform the power flow calculation of the distribution area again until it converges;

[0021] Step 7: Judgment of user voltage difference. According to the above power flow calculation results, judge whether the voltage difference between the head end and all users exceeds ±4%. For ABC-phase users, select the phase with the largest voltage over-limit as the voltage over-limit value. If it exceeds, sort according to the deviation between the user voltage and the head-end voltage, and delete the generator CI ME components associated with the photovoltaic user with the largest deviation until the user voltage difference is within 4%. Judge whether the number of photovoltaic users is greater than 0. If so, execute Step 8; otherwise, interrupt the calculation;

[0022] Step 8: Judgment of reverse power supply. Based on the above power flow calculation results, judge whether there is a negative value in the high-frequency power value of the head-end balanced node. The negative value is the reverse power supply. Judge the magnitude of the negative value of the reverse power and the power under the configured maximum allowable reverse load rate, record the excess part, screen out the photovoltaic users with similar power generation at this point among the photovoltaic power generation users, delete this photovoltaic power generation user, and perform the power flow calculation again until the reverse power supply is within the allowable range. Judge whether the number of photovoltaic users is greater than 0. If so, execute Step 9; otherwise, interrupt the calculation;

[0023] Step 9: Judgment of wire load rate. Based on the above power flow calculation results, traverse all wires starting from the terminal wires, and finally optimize the main trunk line. Judge whether there is a moment when the active power is less than 0 and the absolute value of the wire load rate is greater than 100% in the calculation results. If so, eliminate the current of the CI ME generator equipment associated with the photovoltaic users under this wire and the generator equipment with the smallest absolute value of over-limit, and perform the power flow calculation again until the reverse load rate of the wire is within 100%;

[0024] Step 10: Output the maximum capacity and access scheme. According to the above process, output the maximum accessible capacity of the distribution area that meets the conditions of a voltage difference not exceeding 4%, a reverse load of the distribution transformer not exceeding 80%, and a wire segment load not exceeding 100%, and form a user access scheme.

[0025] Further, in Step 3, it specifically includes the following steps:

[0026] Step (1) Power flow calculation: Based on the topological graph, combined with the node types required for power flow calculation, perform topological equivalence. The head end of the distribution area (i.e., the outlet side of the distribution transformer) is equivalent to a VD node, the loads and photovoltaic users are equivalent to PQ nodes, and judge whether their operation data is positive or negative and equivalent to loads or generators; use the Newton-Raphson algorithm to automatically list the correction equations of the power network for the constraints of node injection power, the constraints of node voltage magnitude, and the constraints of relative phase angles, and perform iterative calculations;

[0027] Step (2) Pre-judgment: Based on the power flow calculation results, judge whether there is a pressure difference exceeding 4% and a reverse load exceeding 100% in the original state of the distribution area.

[0028] Furthermore, the process of pressure difference judgment is as follows:

[0029] Assume that Ua,i, Ub,i, and Uc,i represent the a, b, and c phases of the i-th user respectively, and Ua,0, Ub,0, and Uc,0 represent the a, b, and c phases of the head end. For each phase of each user, calculate the difference from the head end phase and process it:

[0030]

[0031] According to the calculated phase voltages of each user, compare and judge the maximum value of the three-phase pressure difference with the reference value of 4%:

[0032]

[0033] In the above formula, Ucz = 1 indicates that there is a user pressure difference exceeding 4%, terminate the calculation, and Ucz = 0 indicates that the user pressure difference is normal in the initial state and the execution can continue.

[0034] Furthermore, the process of reverse power supply judgment is as follows:

[0035] Based on the power flow calculation results, judge whether there is an over-limit of reverse power supply in the initial state of the distribution area, and take the negative value data of the power at the head end balance node of the power flow calculation;

[0036] Assume that the three-phase reverse powers at the head end are Pa, Pb, and Pc respectively, and the transformer capacity is S0. Judge whether the values of the three-phase reverse load rates are over-limit, and calculate the three-phase load rates at the head end:

[0037]

[0038] According to the calculated three-phase load rates at the head end, compare and judge with the reference value of -100%:

[0039]

[0040] In the above formula, P fxfzlIndicates the head-end reverse load rate, P fxfzl = 1 indicates that the head-end reverse load rate is less than 100%, and the calculation can continue, P fxfzl = 0 indicates that the head-end reverse load rate exceeds 100%, and the calculation is terminated.

[0041] Furthermore, in step four, the calculation method of the power generation power of photovoltaic users is as follows:

[0042] It is assumed that all photovoltaic users are installed with three-phase grid-connected photovoltaic panels, and the roof area of each household is S i , according to the unit capacity P of the standard photovoltaic panel s , combined with the regional photovoltaic curve P t , the maximum power generation power of each photovoltaic user can be calculated, and the calculation formula is as follows:

[0043] S i = P s * P t .

[0044] Furthermore, in step six, based on the power flow calculation results, it is judged whether the reverse load rate of the wire segment in the substation area exceeds 100%. The specific process is as follows:

[0045] Assume that the reverse currents of a certain section of wire are Ia, Ib, and Ic respectively, and the wire carrying capacity is I0. Judge whether the values of the three-phase reverse load rates of the wire are out of limit, and calculate the three-phase load rates of the wire:

[0046]

[0047] According to the calculated three-phase load rates of the wire, compare and judge with the reference value of -100%:

[0048]

[0049] In the above formula, I fxfzl represents the reverse load rate of the wire, I fxfzl = 1 indicates that the head-end reverse load rate is less than 100%, and the calculation can continue, I fxfzl = 0 indicates that the head-end reverse load rate exceeds 100%, and photovoltaic users are excluded.

[0050] Furthermore, in step seven, the calculation formula of the user pressure difference refers to the pressure difference calculation formula in step three.

[0051] Furthermore, in step eight, the calculation formula of the reverse power supply refers to the reverse power supply calculation formula in step three.

[0052] Compared with the prior art, the method for analyzing the maximum accessible capacity of distributed photovoltaics in a substation area considering voltage drop and load has the following technical effects:

[0053] 1. The present invention proposes to conduct simulation analysis based on the on-site environment and operation status of the substation area, perform power flow calculation in the substation area, combine with the actual installable roof area of users, automatically simulate and form a topological graph after connecting to the photovoltaic system, and carry out the calculation of the maximum photovoltaic capacity that can be connected to the substation area. This calculation method is closer to the actual application situation of the substation area, and the calculation results are more accurate and practical.

[0054] 2. Based on the power flow calculation in the substation area, comprehensively considering the constraints that the pressure difference does not exceed 4% and the reverse load of the distribution transformer does not exceed 80%, and the load of the wire segment does not exceed 100%, to ensure that the maximum photovoltaic capacity and connection plan output in the substation area will not affect the line loss and power supply voltage quality in the substation area.

[0055] 3. Taking the maximum connection as the premise, rather than local consumption, based on the actual situation of the substation area, automatically establish a simulation analysis model. By setting constraints such as reverse power and wire load, when the connection capacity in the substation area is the largest, a reasonable reverse power supply is generated in the substation area while meeting the management work in terms of both line loss and voltage, and a specific photovoltaic connection plan is output to guide the connection of distributed photovoltaics.

[0056] 4. Processed in a procedural manner. After preparing the data required for the calculation, the calculation is performed through full-automatic repeated iteration, and finally an effective calculation result is output. Description of the Drawings

[0057] Figure 1 is a flowchart of an analysis method for the maximum accessible capacity of distributed photovoltaics in a substation area considering voltage drop and load according to the present invention. Detailed Embodiments

[0058] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated in the drawings here can be arranged and designed in various different configurations.

[0059] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the present invention claimed, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0060] It should be noted that similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0061] Example 1

[0062] As Figure 1 shown, a method for analyzing the maximum accessible capacity of distributed photovoltaic power in a substation area considering voltage drop and load includes the following steps:

[0063] Step 1: Collect source - end data. The data includes but is not limited to the topological graph of the substation area, basic parameters of substation area equipment, power curves of typical photovoltaic users, roof areas of accessible photovoltaic users, area of a single photovoltaic panel, and capacity of a single photovoltaic panel;

[0064] Step 2: Clean the data and judge whether the key data participating in the calculation is empty or abnormal;

[0065] Step 3: Judge pre - conditions. Conduct power flow calculations on the initial substation area and typical daily operation data, and exclude the substation areas where the voltage difference exceeds 4% and the reverse load exceeds 100% under the initial state. Specifically, it includes the following steps:

[0066] Step (1) Power flow calculation: Based on the topological graph, combined with the node types required for power flow calculation, perform topological equivalence. The head end of the substation area (i.e., the outlet side of the distribution transformer) is equivalent to a VD node, the load and photovoltaic users are equivalent to PQ nodes, and judge whether the positive and negative of their operation data are equivalent to load or generator; Use the Newton - Raphson algorithm to automatically list the correction equations of the power network for the constraints on the injected power of nodes, the constraints on the magnitude of node voltages, and the constraints on the relative phase angles, and perform iterative calculations;

[0067] Step (2) Pre - judgment: Based on the power flow calculation results, judge whether there is a pressure difference exceeding 4% and a reverse load exceeding 100% in the original state of the substation area;

[0068] The process of pressure difference judgment is as follows:

[0069] Assume that Ua,i, Ub,i, and Uc,i represent the a, b, and c phases of the i - th user respectively, and Ua,0, Ub,0, and Uc,0 represent the a, b, and c phases of the head end. For each phase of each user, calculate the difference from the head - end phase and process it:

[0070]

[0071] According to the calculated phase voltages of each user, compare the maximum value of the three - phase pressure difference with the reference value of 4% for judgment:

[0072]

[0073] In the above formula, Ucz = 1 indicates that there is a user pressure difference exceeding 4%, terminate the calculation; Ucz = 0 indicates that the user pressure difference is normal under the initial state, and the execution can continue;

[0074] The process of judging the reverse power supply is as follows:

[0075] Based on the power flow calculation results, judge whether there is an over-limit of reverse power supply in the initial state of the substation area, and take the data with negative power at the first balancing node of the power flow calculation as the initial value;

[0076] Assume that the three-phase reverse power at the first end is Pa, Pb, and Pc respectively, and the transformer capacity is S0. Judge whether the values of the three-phase reverse load rates are over-limit, and calculate the three-phase load rates at the first end:

[0077]

[0078] According to the calculated three-phase load rates at the first end, compare and judge with the reference value of -100%:

[0079]

[0080] In the above formula, P fxfzl represents the reverse load rate at the first end, P fxfzl =1 indicates that the reverse load rate at the first end is less than 100%, and the calculation can continue. P fxfzl =0 indicates that the reverse load rate at the first end exceeds 100%, and the calculation is terminated;

[0081] Step 4: Deduce the photovoltaic power generation. According to the roof areas of the users who can install photovoltaic power generation collected, calculate the number and capacity of the photovoltaic panels that can be installed for each household, and combine with the typical photovoltaic load curve of the collected area to deduce the power generation data of the photovoltaic users in the case of installing photovoltaic power generation;

[0082] Step 5: Modify the preparation data for calculating the theoretical line loss of the substation area. Based on the current situation of the substation area topology graph, combine with the roof areas of the users who can install photovoltaic power generation, virtualize the electrical components of the photovoltaic users, and simulate and construct the substation area topology graph after connecting the photovoltaic power generation;

[0083] First, add photovoltaic components in full quantity. Combine with the power curve of the photovoltaic users deduced in Step 3 to carry out power flow calculation, and judge whether the power flow converges. If the power flow calculation converges, skip Step 6 and execute Step 7. If the power flow calculation does not converge, execute Step 6;

[0084] Step 6: Conduct wire load rate processing. In the case of full quantity of photovoltaic power generation, if the power flow calculation of the substation area does not converge, judge whether the load rates of all the end wires exceed the wire current-carrying capacity after connecting the photovoltaic power generation. If it exceeds the wire current-carrying capacity, judge the magnitude of the current generated by the photovoltaic users connected under this section of wire through simple measurement, and remove the photovoltaic users whose generated current magnitude is close to the part exceeding the wire current-carrying capacity, and then conduct the power flow calculation of the substation area again until it converges;

[0085] Step 7: User voltage difference judgment. According to the above power flow calculation results, judge whether the voltage difference between the head end and all users exceeds ±4%. For users with ABC phases, select the phase with the largest voltage over - standard as the voltage over - standard value. If it exceeds, sort according to the deviation between the user voltage and the head - end voltage, and delete the generator CIME components associated with the photovoltaic user with the largest deviation until the user voltage differences are all within 4%. Then judge whether the number of photovoltaic users is greater than 0. If so, execute Step 8; otherwise, interrupt the calculation. The calculation formula for the user voltage difference refers to the voltage difference calculation formula in Step 3;

[0086] Step 8: Reverse power supply power judgment. Based on the above power flow calculation results, judge whether the high - frequency power value of the head - end balanced node is negative. The negative value is the reverse power supply power. Judge the magnitude relationship between the negative value of the reverse power and the power under the configured maximum allowable reverse load rate, record the excess part, screen out the photovoltaic users with similar power generation at this point among the photovoltaic power generation users, delete the photovoltaic power generation users, and perform the power flow calculation again until the reverse power supply power is within the allowable range. Then judge whether the number of photovoltaic users is greater than 0. If so, execute Step 9; otherwise, interrupt the calculation. The calculation formula for the reverse power supply power refers to the reverse power supply power calculation formula in Step 3;

[0087] Step 9: Conductor load rate judgment. Based on the above power flow calculation results, traverse all conductors starting from the end - of - line conductors, and finally optimize the main trunk line. Judge whether there is a moment when the active power is less than 0 and the absolute value of the conductor load rate is greater than 100% in the calculation results. If so, eliminate the current of the CI ME generator equipment associated with the photovoltaic users under the conductor and the generator equipment with the smallest absolute value of the over - limit, and perform the power flow calculation again until the reverse conductor load rates are all within 100%;

[0088] Step 10: Output the maximum capacity and access plan. According to the above process, output the maximum accessible capacity of the distribution area that meets the conditions of the voltage difference not exceeding 4%, the reverse load of the distribution transformer not exceeding 80%, and the load of the conductor segment not exceeding 100%, and form a user access plan.

[0089] Embodiment 2

[0090] As Figure 1 shown, a method for analyzing the maximum accessible capacity of distributed photovoltaic power in a distribution area considering voltage drop and load includes the following steps:

[0091] Step 1: Conduct source - end data collection. The data includes but is not limited to the topological graph of the distribution area, the basic parameters of the distribution area equipment, the power curves of typical photovoltaic users, the roof area of accessible photovoltaic users, the area of a single photovoltaic panel, and the capacity of a single photovoltaic panel;

[0092] Step 2: Perform data cleaning. Judge whether the key data participating in the calculation is empty or abnormal;

[0093] Step 3: Prerequisite judgment. Perform power flow calculations on the initial substation area and the operating data of typical days, and exclude the substations where the voltage difference exceeds 4% and the reverse load exceeds 100% under the initial state;

[0094] Step 4: Calculate the photovoltaic power generation. Based on the roof areas of the users where photovoltaic can be installed collected, calculate the number and capacity of photovoltaic panels that can be installed for each household. Combining with the typical photovoltaic load curve of the collected area, calculate the power generation data of photovoltaic users in the case of installing photovoltaic; The calculation method of the power generation of photovoltaic users is as follows:

[0095] By default, all photovoltaic users install three-phase grid-connected photovoltaic panels. Assume that the roof area of each household is S i , according to the unit capacity P of the standard photovoltaic panel s , combined with the regional photovoltaic curve P t , the maximum power generation of each photovoltaic user can be calculated. The calculation formula is as follows:

[0096] S i = P s * P t (5);

[0097] Step 5: Modify the preparation data for calculating the theoretical line loss of the substation area. Based on the current situation of the substation area topology graph, combined with the roof areas of the users where photovoltaic can be installed, virtualize the electrical components of photovoltaic users, and simulate and construct the substation area topology graph after connecting photovoltaic;

[0098] First, add photovoltaic components in full quantity. Combining with the power curve of photovoltaic users deduced in Step 3, perform power flow calculations to determine whether the power flow converges. If the power flow calculation converges, skip Step 6 and execute Step 7. If the power flow calculation does not converge, execute Step 6;

[0099] Step 6: Conduct wire load rate processing. In the case of full-scale photovoltaic, if the power flow calculation of the substation area does not converge, determine whether the load rate of all end wires exceeds the wire current-carrying capacity after connecting photovoltaic. If it exceeds the wire current-carrying capacity, simply measure and determine the magnitude of the current generated by the photovoltaic users connected to this section of the wire, and remove the photovoltaic users whose generated current is close to the part of the current exceeding the wire current-carrying capacity, and perform the power flow calculation of the substation area again until convergence;

[0100] Based on the power flow calculation results, determine whether there is a reverse load rate exceeding 100% in the wire segments of the substation area. The specific process is as follows:

[0101] Assume that the reverse currents of a certain section of wire are Ia, Ib, and Ic respectively, and the wire current-carrying capacity is I0. Determine whether the values of the three-phase reverse load rates of the wire are out of limit, and calculate the three-phase load rate of the wire:

[0102]

[0103] Based on the calculated three-phase load rates of the conductors, compare with the reference value of -100% for judgment:

[0104]

[0105] In the above formula, I fxfzl represents the reverse load rate of the conductor. I fxfzl =1 indicates that the reverse load rate at the head end is less than 100%, and the calculation can continue. I fxfzl =0 indicates that the reverse load rate at the head end exceeds 100%, and photovoltaic users are to be excluded;

[0106] Step 7: User voltage difference judgment. According to the above power flow calculation results, judge whether the voltage difference between the head end and all users exceeds ±4%. For ABC-phase users, select the phase with the largest voltage over - standard as the voltage over - standard value. If it exceeds, sort according to the deviation between the user voltage and the head end voltage, and delete the generator CIME components associated with the photovoltaic user with the largest deviation until the user voltage differences are all within 4%. Judge whether the number of photovoltaic users is greater than 0. If so, execute Step 8; otherwise, interrupt the calculation;

[0107] Step 8: Reverse power supply power judgment. Based on the above power flow calculation results, judge whether there is a negative value in the high - frequency power value of the head - end balanced node. The negative value is the reverse power supply power. Judge the magnitude of the negative value of the reverse power and the power under the configured maximum allowable reverse load rate, record the excess part, screen the photovoltaic users with similar power generation at this point, delete the photovoltaic users, and perform power flow calculation again until the reverse power supply power is within the allowable range. Judge whether the number of photovoltaic users is greater than 0. If so, execute Step 9; otherwise, interrupt the calculation;

[0108] Step 9: Conductor load rate judgment. Based on the above power flow calculation results, traverse all conductors starting from the end - point conductors, and finally optimize the main line. Judge whether there is a moment when the active power is less than 0 and the absolute value of the conductor load rate is greater than 100%. If so, exclude the CI ME generator equipment current of the photovoltaic users connected to the conductor and the generator equipment with the smallest absolute value of over - limit, and perform power flow calculation again until the reverse load rates of all conductors are within 100%;

[0109] Step 10: Output the maximum capacity and connection plan. According to the above process, output the maximum connectable capacity of the sub - station area that meets the conditions of voltage difference not exceeding 4%, reverse load of the distribution transformer not exceeding 80%, and conductor - segment load not exceeding 100%, and form a user connection plan.

[0110] The method for analyzing the maximum accessible capacity of distributed photovoltaic power in a substation area considering voltage drop and load provided by the present invention proposes to conduct simulation analysis based on the on-site environment and operation status of the substation area and the power flow calculation in the substation area. Combining with the actual installable roof area of users, it automatically simulates and forms a topological graph after connecting photovoltaic power, and carries out the calculation of the maximum photovoltaic capacity accessible to the substation area. This calculation measure is closer to the actual application situation of the substation area, and the calculation result is more accurate and practical. Based on the power flow calculation in the substation area, this method comprehensively considers the constraint conditions that the pressure difference does not exceed 4%, the reverse load of the distribution transformer does not exceed 80%, and the load of the wire segment does not exceed 100%, so as to ensure that the maximum photovoltaic capacity accessible to the substation area and the access scheme output will not affect the line loss and power supply voltage quality of the substation area.

[0111] The above are only the embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. A method for analyzing the maximum accessible capacity of distributed photovoltaic power generation in a metropolitan area considering voltage drop and load, characterized in that: The following steps are involved: Step S1: Carry out source data collection and collect multi-dimensional field data, including but not limited to substation topology, archives, operation data and user-installable photovoltaic access area; Step S2: Perform data cleaning to correct missing and abnormal data; Step S3: construct a photovoltaic user equivalent model, simulate the installation of the maximum accessible photovoltaic capacity and perform power flow calculation; Step S4: Conduct conductor current carrying capacity analysis, user pressure difference analysis, reverse supply power analysis, and photovoltaic power generation conductor load rate analysis in sequence, eliminate relevant photovoltaic users, and complete the calculation of the maximum photovoltaic access capacity for the area grid optimization.

2. According to claim 1, a method for analyzing the maximum accessible capacity of distributed photovoltaic power generation in a substation considering voltage drop and load, characterized in that: The specific steps include: Step 1: Collect data from the source end, including but not limited to the topological diagram of the substation area, basic parameters of substation equipment, power curves of typical photovoltaic users, roof area of ​​photovoltaic users that can be connected, area of ​​a single photovoltaic panel, and capacity of a single photovoltaic panel; Step 2: Perform data cleaning to determine whether the key data involved in the calculation is empty or whether the data is abnormal; Step 3: Precondition judgment, carry out power flow calculation on the initial substation and typical daily operation data, and exclude substations with voltage difference exceeding 4% and reverse load exceeding 100% in the initial state; Step 4: Estimate the photovoltaic power generation. According to the collected roof areas of users who can install photovoltaics, calculate the number and capacity of photovoltaic panels that can be installed for each household. Combined with the collected typical photovoltaic load curves in the region, estimate the power generation data of photovoltaic users when photovoltaics are installed. Step 5: Modify the theoretical line loss calculation preparation data of the substation, based on the current status of the substation topology, combined with the user roof area where photovoltaics can be installed, virtualize the electrical components of photovoltaic users, and simulate and construct the substation topology after photovoltaic access; First, add all photovoltaic components, and combine the photovoltaic user power curve calculated in step 3 to perform power flow calculation to determine whether the power flow converges. If the power flow calculation converges, skip step 6 and execute step 7. If the power flow calculation does not converge, execute step 6. Step 6: Conductor load rate processing. In the case of full photovoltaic, if the power flow calculation of the substation does not converge, determine whether the load rate of all terminal conductors after connecting to photovoltaic exceeds the conductor current carrying capacity. If it exceeds the conductor current carrying capacity, determine the current size generated by the photovoltaic users connected to this section of the conductor through simple measurement, eliminate photovoltaic users whose current size is close to the current exceeding the conductor current carrying capacity, and perform the substation power flow calculation again until convergence; Step 7: Determine the voltage difference between users. According to the above power flow calculation results, determine whether the voltage difference between the head end and all users exceeds ±4%. For users in ABC phases, select the phase with the largest voltage excess as the voltage excess value. If exceeded, sort according to the deviation between the user voltage and the head end voltage, and delete the generator CIME element associated with the photovoltaic user with the largest deviation until the user voltage difference is within 4%. Determine whether the number of photovoltaic users is greater than 0. If so, execute step 8, otherwise interrupt the calculation. Step 8: Determine the reverse power supply power. Based on the above power flow calculation results, determine whether the high-frequency power value of the head-end balancing node is negative. The negative value is the reverse power supply power. Determine the magnitude of the negative value of the reverse power and the power under the configured maximum allowable reverse load rate. Record the excess part, select photovoltaic power generation users with a power generation power close to that point, delete the photovoltaic power generation user, and perform power flow calculation again until the reverse power supply power is within the allowable range. Determine whether the number of photovoltaic users is greater than 0. If so, execute step 9, otherwise interrupt the calculation. Step 9: Determine the conductor load rate. Based on the above power flow calculation results, traverse all conductors starting from the end conductor, and finally optimize the main line to determine whether there is a moment in the calculation result where the active power is less than 0 and the absolute value of the conductor load rate is greater than 100%. If so, remove the CIME generator equipment associated with the photovoltaic user under the conductor with the smallest current and the generator equipment with the smallest absolute value of over-limit, and perform power flow calculation again until the reverse load rate of the conductor is within 100%; Step 10: Output maximum capacity and access plan. According to the above process, the output substation can access the maximum accessible capacity that meets the conditions of voltage difference not exceeding 4%, distribution transformer reverse load not exceeding 80%, and conductor segment load not exceeding 100%, and form a user access plan.

3. According to claim 2, a method for analyzing the maximum accessible capacity of distributed photovoltaic power generation in a substation considering voltage drop and load, characterized in that: Step three specifically includes the following steps: Step (a) flow calculation: Based on the topological graph and the node types required for flow calculation, perform topological equivalence, the head end of the substation is equivalent to the VD node, the load and photovoltaic user are equivalent to the PQ node, and the positive and negative equivalent of their operating data are determined to be load or generator; the Newton-Raphson algorithm is used to automatically list the correction equations of the power network for the constraints on the node injection power, the constraints on the node voltage size, and the constraints on the relative phase angle, and perform iterative calculations; Step (ii) pre-judgment: based on the results of the power flow calculation, determine whether there is a pressure difference exceeding 4% and a reverse load exceeding 100% in the original state of the substation.

4. According to claim 3, a method for analyzing the maximum accessible capacity of distributed photovoltaic power generation in a substation considering voltage drop and load, characterized in that: The pressure difference judgment process is as follows: Assume that Ua,i, Ub,i and Uc,i represent the a, b, c phases of the i-th user, respectively, and Ua,0, Ub,0 and Uc,0 represent the a, b, c phases of the head end. For each phase of each user, calculate the difference with the head end phase and perform processing: According to the calculated voltage of each phase of each user, the maximum value of the three-phase voltage difference is compared with the reference value of 4% to determine: In the above formula, Ucz=1 means that the user pressure difference exceeds 4%, and the calculation is terminated; Ucz=0 means that the user pressure difference is normal in the initial state and the calculation can continue.

5. According to claim 3, a method for analyzing the maximum accessible capacity of distributed photovoltaic power generation in a substation considering voltage drop and load, characterized in that: The reverse power supply power determination process is as follows: Based on the power flow calculation results, determine whether there is a reverse power supply limit in the initial state of the substation, and take the power of the first-end balancing node at the first end of the power flow calculation as a negative value data; Assuming that the three-phase reverse power at the head end is Pa, Pb and Pc respectively, and the transformer capacity is S0, determine whether the value of the three-phase reverse load rate exceeds the limit, and calculate the three-phase load rate at the head end: According to the calculated three-phase load rate at the head end, compare it with the reference value -100% to make the following judgment: In the above formula, P fxfzl Indicates the reverse load rate at the first end, P fxfzl =1 means the reverse load rate at the head end is less than 100%, and the calculation can continue. fxfzl =0 means that the reverse load rate of the first end exceeds 100%, and the calculation is terminated.

6. The method for analyzing the maximum accessible capacity of distributed photovoltaic power generation in a substation considering voltage drop and load according to claim 2, characterized in that: In step 4, the calculation method for the power generation of photovoltaic users is as follows: It is assumed that all photovoltaic users install three-phase grid-connected photovoltaic panels. Assume that the roof area of ​​each household is S i , according to the unit capacity P of the standard photovoltaic panel s , combined with the regional photovoltaic curve P t , the maximum power generation of each photovoltaic user can be calculated, and the calculation formula is as follows: S i =P s *P t 。 7. A method for analyzing the maximum accessible capacity of distributed photovoltaic power generation in a substation considering voltage drop and load according to claim 2, characterized in that: In step 6, based on the power flow calculation results, it is determined whether there is a reverse load rate exceeding 100% in the conductor segment in the substation area. The specific process is as follows: Assuming that the reverse currents of a certain section of wire are Ia, Ib and Ic respectively, and the current carrying capacity of the wire is I0, determine whether the value of the three-phase reverse load rate of the wire exceeds the limit, and calculate the three-phase load rate of the wire: According to the calculated three-phase load rate of the conductor, it is compared with the reference value -100% to determine: In the above formula, I fxfzl Indicates the reverse load rate of the wire, I fxfzl =1 means the reverse load rate at the head end is less than 100%, and the calculation can be continued. fxfzl =0 means that the reverse load rate of the first end exceeds 100%, and the photovoltaic user is eliminated.

8. The method for analyzing the maximum accessible capacity of distributed photovoltaic power generation in a substation considering voltage drop and load according to claim 2, characterized in that: In step 7, the user pressure difference calculation formula refers to the pressure difference calculation formula in step 3.

9. The method for analyzing the maximum accessible capacity of distributed photovoltaic power generation in a substation considering voltage drop and load according to claim 2, characterized in that: In step eight, the reverse power supply power calculation formula refers to the reverse power supply power calculation formula in step three.

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