A Method and System for Evaluating the Developable Capacity of a Distributed Photovoltaic Substation Area

Abstract

The present invention relates to the technical field of power grid distribution, and specifically relates to a method and system for evaluating the developable capacity of a distributed photovoltaic substation area. According to the power consumption of all users in the substation area, the maximum load power of the substation area power grid is obtained; according to the maximum load power of the substation area power grid and the total photovoltaic load power already connected to the power grid, the maximum openable capacity of the substation area power grid is obtained; according to the difference between the power of users and photovoltaic in the preset historical time period of the substation area, the photovoltaic consumption matching degree of the substation area is obtained, and in combination with the frequency instability of the substation area power grid, the power grid capacity adjustment factor of the substation area is obtained; the maximum openable capacity of the substation area power grid is adjusted according to the power grid capacity adjustment factor to obtain the actual photovoltaic capacity that can be connected to the substation area power grid. Using the actual photovoltaic capacity that can be connected to the substation area power grid to operate the photovoltaic connection can improve the safety and stability of the power grid and the economic operation efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of power grid distribution, and particularly to a method and system for evaluating the developable capacity of a distributed photovoltaic substation area. Background Art

[0002] With the transformation of the global energy structure and the rapid development of renewable energy, distributed photovoltaic power generation, as a clean and efficient energy utilization method, is gradually becoming an important part of the power system. However, with the large-scale and disorderly access of distributed photovoltaics, it has brought severe challenges to the access and consumption of the distribution network, and at the same time has caused a series of problems such as overvoltage in some substations and reverse overload of equipment, hindering the healthy and orderly development of distributed photovoltaics and having a significant impact on the safe and economic operation of the distribution network.

[0003] Currently, when evaluating the available capacity of a distributed photovoltaic substation area, distributed photovoltaic power is generally connected based on the difference between the maximum load of the power grid in this substation area and the installed capacity (i.e., the maximum available capacity). However, there may be situations where the power grid stability of the corresponding substation area is not good or the photovoltaic power generation does not match the power grid load demand. Therefore, if the maximum available capacity of the power grid is used as the actual photovoltaic access capacity, it may cause the consequences of short-term overload of the power grid and energy waste, affecting the power grid stability. Summary of the Invention

[0004] In order to solve the technical problem that the existing method of directly using the maximum available capacity of the power grid as the actual photovoltaic access capacity will affect the power grid stability, the purpose of the present invention is to provide a method and system for evaluating the developable capacity of a distributed photovoltaic substation area, and the specific technical solutions adopted are as follows:

[0005] In the first aspect of the present invention, a method for evaluating the developable capacity of a distributed photovoltaic substation area is provided, including:

[0006] Obtain the maximum load power of the substation area power grid according to the power consumption of all users in the substation area;

[0007] Obtain the maximum available capacity of the substation area power grid according to the maximum load power of the substation area power grid and the total photovoltaic load power already connected to the power grid;

[0008] Obtain the photovoltaic accommodation matching degree of the substation area according to the difference between the power of users and photovoltaics in the preset historical time period of the substation area, and combine the frequency instability of the substation area power grid to obtain the power grid capacity adjustment factor of the substation area;

[0009] Adjust the maximum available capacity of the substation area power grid according to the power grid capacity adjustment factor to obtain the actual photovoltaic access capacity of the substation area power grid.

[0010] In an exemplary embodiment, obtaining the maximum load power of the substation area grid according to the power consumption of all users in the substation area includes:

[0011] Obtaining the maximum total daily power consumption of users according to the total daily power consumption of users in the preset historical time period of the substation area;

[0012] Obtaining the total power consumption of users at each sampling moment within the target date corresponding to the maximum total daily power consumption of the users;

[0013] Obtaining the relative load power of the grid at each sampling moment according to the difference between the total power consumption of users at each sampling moment and the total power consumption of users at other sampling moments within the target date;

[0014] Taking the total power consumption of users at the sampling moment corresponding to the maximum relative load power of the grid as the maximum load power of the substation area grid.

[0015] In an exemplary embodiment, obtaining the maximum available capacity of the substation area grid according to the maximum load power of the substation area grid and the total load power of the photovoltaic power already connected to the grid includes:

[0016] Taking the difference between the maximum load power of the substation area grid and the total load power of the photovoltaic power already connected to the grid as the maximum available capacity of the substation area grid.

[0017] In an exemplary embodiment, obtaining the photovoltaic accommodation matching degree of the substation area according to the difference between the power of users and photovoltaic power in the preset historical time period of the substation area includes:

[0018] Obtaining the total power consumption sequence of users and the total power generation sequence of photovoltaic power, where the total power consumption sequence of users includes the total power consumption of users at each sampling moment in the preset historical time period of the substation area, and the total power generation sequence of photovoltaic power includes the total power generation of photovoltaic power at each sampling moment in the preset historical time period of the substation area;

[0019] Obtaining the power difference at each sampling moment between the total power consumption sequence of users and the total power generation sequence of photovoltaic power, and obtaining the similarity between the total power consumption sequence of users and the total power generation sequence of photovoltaic power;

[0020] Obtaining the photovoltaic accommodation matching degree of the substation area according to the power difference and the similarity, where the photovoltaic accommodation matching degree of the substation area is inversely proportional to the power difference and directly proportional to the similarity.

[0021] In an exemplary embodiment, the power difference is the absolute value of the power difference; the calculation formula for the photovoltaic accommodation matching degree of the substation area is:

[0022] ;

[0023] Among them, is the matching degree of photovoltaic power consumption in the substation area, is the sequence of the total power consumption of users, is the sequence of the total photovoltaic power generation, is the total power consumption of users at the th sampling moment, is the total photovoltaic power generation at the th sampling moment, is the similarity between the sequence of the total power consumption of users and the sequence of the total photovoltaic power generation, is the linear normalization function, M is the number of sampling moments in the preset historical time period, is the negative correlation normalization of

[0024] In an exemplary embodiment, the obtaining process of the frequency instability of the substation area power grid includes:

[0025] Obtain the actual frequency of the user-side power grid at each sampling moment within the target date;

[0026] According to the difference between the actual frequency of the user-side power grid and the rated frequency of the substation area power grid at each sampling moment within the target date, obtain the frequency instability of the substation area power grid.

[0027] In an exemplary embodiment, the obtaining process of the substation area power grid capacity adjustment factor includes:

[0028] Normalize the matching degree of photovoltaic power consumption in the substation area and the frequency instability of the substation area power grid respectively;

[0029] Calculate the product of the normalized matching degree of photovoltaic power consumption in the substation area and the normalized frequency instability of the substation area power grid to obtain the substation area power grid capacity adjustment factor.

[0030] In an exemplary embodiment, adjusting the maximum openable capacity of the substation area power grid according to the power grid capacity adjustment factor to obtain the actual photovoltaic capacity that can be accessed by the substation area power grid includes:

[0031] The calculation formula of the actual photovoltaic capacity that can be accessed by the substation area power grid is as follows:

[0032] ;

[0033] Among them, is the actual photovoltaic capacity that can be accessed by the substation area power grid, is the maximum openable capacity of the substation area power grid, is the power grid capacity adjustment factor.

[0034] In an exemplary embodiment, before obtaining the maximum load power of the substation area power grid according to the electricity consumption powers of all users in the substation area, the method for evaluating the developable capacity of the distributed photovoltaic substation area further includes:

[0035] Obtain the total photovoltaic power generation and total power consumption in the preset historical time period of the substation area;

[0036] Obtain the maximum single-day photovoltaic power generation in the preset historical time period, and obtain the actual average voltage of photovoltaic power generation on the date corresponding to the maximum single-day photovoltaic power generation;

[0037] If the total photovoltaic power generation is less than the total power consumption and the actual average voltage of photovoltaic power generation is within the preset stable voltage range of photovoltaic power generation, then the substation area executes the step of obtaining the maximum load power of the substation area power grid according to the electricity consumption powers of all users in the substation area.

[0038] In a second aspect of the present invention, there is provided a system for evaluating the developable capacity of a distributed photovoltaic substation area, including: a memory and a processor; the memory is connected to the processor; the memory is used for storing program instructions; the processor is used for implementing the above-mentioned method for evaluating the developable capacity of the distributed photovoltaic substation area when the program instructions are executed.

[0039] The present invention has the following beneficial effects: When simply taking the maximum openable capacity of the substation area power grid as the actual openable capacity, the problems of not considering the stability of the power grid and the matching degree between photovoltaic power generation and the power grid load demand, which affect the stability of the power grid, are optimized in the present invention. First, the maximum load power of the substation area power grid is obtained according to the electricity consumption powers of all users in the substation area, and then the maximum openable capacity of the substation area power grid is obtained by combining the maximum load power of the substation area power grid and the total photovoltaic load power already connected to the power grid; More importantly, according to the difference between the powers of users and photovoltaic in the preset historical time period of the substation area, the photovoltaic accommodation matching degree of the substation area is obtained, and in combination with the frequency instability of the substation area power grid, a capacity adjustment factor of the substation area power grid is obtained, so as to adjust the maximum openable capacity of the substation area power grid according to the capacity adjustment factor of the power grid, and obtain the actual accessible photovoltaic capacity of the substation area power grid corresponding to the actual situation of the substation area power grid. Operating the photovoltaic access with the actual accessible photovoltaic capacity of the substation area power grid can improve the safety and stability of the power grid and the economic operation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a schematic diagram of photovoltaic access to the power grid provided by an embodiment of the present invention;

[0041] Figure 2 is a flowchart of a method for evaluating the developable capacity of a distributed photovoltaic substation area provided by an embodiment of the present invention;

[0042] Figure 3 It is a flowchart of the steps further included in a method for evaluating the developable capacity of a distributed photovoltaic substation area provided by an embodiment of the present invention;

[0043] Figure 4 It is a flowchart of step 1 provided by an embodiment of the present invention;

[0044] Figure 5 It is a flowchart for obtaining the matching degree of photovoltaic power consumption in the substation area provided by an embodiment of the present invention;

[0045] Figure 6 It is a flowchart for obtaining the frequency instability of the power grid in the substation area provided by an embodiment of the present invention;

[0046] Figure 7 It is a flowchart for obtaining the power grid capacity adjustment factor in the substation area provided by an embodiment of the present invention. Detailed implementation manners

[0047] In order to further elaborate on the technical means and effects adopted by the present invention to achieve the intended invention purpose, the following, in combination with the accompanying drawings and preferred embodiments, details the specific implementation manners, structures, features and their effects of the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs.

[0049] The purpose of a method and system for evaluating the developable capacity of a distributed photovoltaic substation area provided in this embodiment is as follows: When optimizing the actual open capacity with the maximum openable capacity of the substation area, the problem of grid operation risks caused by not considering the stability of the power grid and the matching degree between photovoltaic power generation and grid load demand is solved. By analyzing the grid instability and photovoltaic power consumption matching degree of the substation area suitable for accessing photovoltaic, the capacity adjustment factor is calculated to adjust the maximum photovoltaic expandable capacity of this substation area, improving the practicality and accuracy of the evaluation results.

[0050] The openable capacity of a distributed photovoltaic substation area refers to the maximum power capacity that a distributed photovoltaic system can access and operate normally in a specific power grid. Connecting a distributed photovoltaic to the power grid helps enhance the flexibility and security of power supply. General distributed photovoltaic access is as Figure 1As shown for reference only. Generally, DC electrical energy is generated by photovoltaic modules, and the DC power is converted into AC power by an inverter. Then, through a distribution box or a busbar trunking system, the output currents of multiple photovoltaic modules are aggregated together, and then connected to the power grid through a grid connection cabinet, while providing various protection, control, monitoring, and switching functions required for grid connection. Since the large-scale and disordered access of photovoltaic power generation corresponding to different users (i.e., end nodes) will affect the operating load of the power grid, it is necessary to evaluate the capacity of the power grid that can access photovoltaic power. In order to more accurately evaluate the expandable capacity of the power grid in the substation area, relevant monitoring devices are required to obtain the historical real-time relevant operating data (power consumption, power, frequency, etc.) of the substation area power grid, the power generation data (power generation, power, etc.) of the already connected photovoltaic power, as well as the real-time power consumption and power data of users, etc. Thus, the accurately assess the developable capacity of photovoltaic power in the substation area and ensure the safe and stable operation of the power grid and distributed photovoltaic power.

[0051] A method for evaluating the developable capacity of a distributed photovoltaic substation area provided in this embodiment, as Figure 2 shown, includes the following steps:

[0052] Step 1: Obtain the maximum load power of the substation area power grid according to the power consumption of all users in the substation area.

[0053] In an exemplary embodiment, since each distribution substation area has its maximum bearing capacity, if the existing load in this substation area is close to its capacity, then continuing to connect more distributed photovoltaic power may lead to various dangerous problems. Therefore, before obtaining the maximum load power of the substation area power grid according to the power consumption of all users in the substation area, it is also necessary to evaluate the operating condition of the power grid in this substation area to determine whether more photovoltaic power generation systems should be connected.

[0054] The total power returned to the grid in the substation area refers to the part of the surplus electrical energy that returns to the grid through the power grid after the photovoltaic system generates electricity. The size of the total power returned to the grid can more intuitively and accurately measure the degree to which the power grid in this substation area can accommodate the access of distributed photovoltaic power. If the total power returned to the grid is larger, it means that the power demand in this substation area exceeds the photovoltaic power generation, and it is not recommended to continue connecting the photovoltaic system. Otherwise, it can be continued to be connected.

[0055] At the same time, after the photovoltaic power is connected to the low-voltage substation area, it has a certain boosting effect on the voltage of the substation area. Especially when the photovoltaic power generation is too large and exceeds the standard of the substation area itself, it may cause the voltage of users or the photovoltaic power itself to exceed the limit, which has an adverse impact on the power supply reliability and stability of the distribution network. Therefore, it is possible to evaluate whether distributed photovoltaic power can be continued to be connected according to whether voltage over-limitation occurs in this substation area on the maximum photovoltaic power generation day.

[0056] It should be understood that the data related to photovoltaic power generation, photovoltaic voltage, photovoltaic power generation power, etc. in this embodiment are all data of the photovoltaic system that has been connected to the distribution network of the substation. According to the data of the photovoltaic system that has been connected to the distribution network of the substation, combined with other relevant data of the substation, such as the electricity consumption of users in the substation, the grid frequency, etc., comprehensive analysis is carried out to finally obtain the actual photovoltaic capacity that can be connected to the distribution network of the substation.

[0057] In an exemplary embodiment, as Figure 3 shown, the method for evaluating the developable capacity of the distributed photovoltaic substation also includes the following process:

[0058] Step A: Obtain the total photovoltaic power generation and the total electricity consumption in the preset historical period of the substation.

[0059] Preset a preset historical period, and the duration of the preset historical period and the time interval from the current moment are set according to actual needs. For example, the preset historical period is within one month before the current moment, that is, the preset historical period is the most recent month.

[0060] Obtain the total photovoltaic power generation in the preset historical period of the substation, and the self - electricity consumption in the preset historical period of the substation, that is, the total electricity consumption. Among them, the method for obtaining the total photovoltaic power generation is: obtain the daily photovoltaic power generation of the photovoltaic that has been connected to the substation every day in the preset historical period of the substation, and then calculate the sum value of the daily photovoltaic power generation in the preset historical period of the substation to obtain the total photovoltaic power generation. Similarly, the method for obtaining the total electricity consumption in the preset historical period of the substation is: obtain the daily electricity consumption of the substation every day in the preset historical period of the substation, and then calculate the sum value of the daily electricity consumption of the substation in the preset historical period of the substation to obtain the total electricity consumption.

[0061] Step B: Obtain the maximum daily photovoltaic power generation in the preset historical period, and obtain the actual average photovoltaic voltage on the date corresponding to the maximum daily photovoltaic power generation.

[0062] Since the preset historical period includes multiple days, then obtain the daily photovoltaic power generation every day in the preset historical period. Obtain the maximum value from these daily photovoltaic power generations, and this maximum value is the maximum daily photovoltaic power generation. Set the date corresponding to the maximum daily photovoltaic power generation as the required date.

[0063] The required date includes multiple sampling moments. It should be understood that the time interval between adjacent sampling moments is set according to actual needs.

[0064] Obtain the actual photovoltaic power generation voltage at each sampling moment within the required date, and then calculate the average value of the actual photovoltaic power generation voltage within the required date to obtain the actual average photovoltaic power generation voltage. The method for obtaining the actual photovoltaic power generation voltage at any sampling moment can be: obtain the actual voltages of each photovoltaic module in the transformer substation area at this sampling moment, and calculate the average value of the actual voltages of all photovoltaic modules in the transformer substation area at this sampling moment as the actual photovoltaic power generation voltage at this sampling moment.

[0065] Step C: If the total photovoltaic power generation is less than the total power consumption, and the actual average photovoltaic power generation voltage is within the preset stable photovoltaic power generation voltage range, the transformer substation area executes Step 1.

[0066] Preset a stable photovoltaic power generation voltage range, and the upper limit value and lower limit value of this stable photovoltaic power generation voltage range are set according to actual judgment needs.

[0067] The total photovoltaic power generation being less than the total power consumption indicates that there is no power feedback, so this transformer substation area can continue to connect distributed photovoltaics; the total photovoltaic power generation being greater than or equal to the total power consumption indicates that there is power feedback, so this transformer substation area should not continue to connect distributed photovoltaics. The actual average photovoltaic power generation voltage being within the preset stable photovoltaic power generation voltage range indicates that the photovoltaic power generation voltage is relatively stable and there is no voltage overlimit situation.

[0068] Therefore, if the total photovoltaic power generation is less than the total power consumption, and the actual average photovoltaic power generation voltage is within the preset stable photovoltaic power generation voltage range, the transformer substation area can continue to connect distributed photovoltaics. This transformer substation area is a transformer substation area that can continue to connect distributed photovoltaics, and then the transformer substation area can continue to execute Step 1.

[0069] In an exemplary embodiment, the following calculation formula is used to obtain the total power feedback amount in a preset historical time period:

[0070] ;

[0071] Wherein, is the total power feedback amount in the preset historical time period of the transformer substation area, is the total photovoltaic power generation in the preset historical time period of the transformer substation area, is the total power consumption in the preset historical time period of the transformer substation area.

[0072] Therefore, if it indicates that the total power generation is greater than or equal to the total power consumption, there is total power feedback, so this transformer substation area should not continue to connect distributed photovoltaics. On the contrary, it should continue to connect.

[0073] The following method is used to calculate the voltage overlimit situation of the maximum daily photovoltaic power generation in the transformer substation area. In this embodiment, exceeding 20% of the rated voltage is used as the judgment standard for voltage overlimit:

[0074] ;

[0075] Among them, is the voltage over-limit situation of the substation area at the maximum daily photovoltaic power generation, is the actual average voltage of photovoltaic power generation on the corresponding date of the maximum daily photovoltaic power generation in the substation area, is the rated voltage of photovoltaic power generation, represents the upper limit voltage, represents the lower limit voltage.

[0076] Therefore, if the average voltage of this substation area on the corresponding date of the maximum daily photovoltaic power generation is within the specified range, then the corresponding , and distributed photovoltaics can continue to be connected; if the average voltage is not within this specified range, then , and it should not continue to be connected.

[0077] Then when judging whether this substation area is suitable for continuing to connect distributed photovoltaics, if the total reverse power transmission and the voltage over-limit situation of the substation area at the maximum daily photovoltaic power generation are both satisfied at the same time, then the substation area continues to connect distributed photovoltaics, that is, step 1 is continued to be executed.

[0078] In addition, the criterion of the substation area can also be obtained according to the above process to realize the screening of different substation areas. Specifically: if there are multiple substation areas to choose from, then initially select: the substation areas that simultaneously satisfy the total reverse power transmission and the voltage over-limit situation of the substation area at the maximum daily photovoltaic power generation . This embodiment will not be elaborated here.

[0079] It should be understood that if it has been determined in advance that the substation area can be connected to the power grid, then the above process of steps A - C can be skipped.

[0080] If the substation area is suitable for continued connection of distributed photovoltaics, it indicates that there is idle load in the power grid of the substation area. Then this spare load corresponds to the maximum open capacity of the power grid. However, since the maximum open capacity of the power grid usually represents the ideal capacity without considering real-time power load fluctuations, equipment limitations, and actual operating conditions, it does not mean that the actual connected capacity of the photovoltaics is the maximum open capacity. Therefore, subsequent adaptive adjustment of the maximum open capacity is required based on the grid instability and the photovoltaic accommodation matching degree to determine the actual connectable photovoltaic capacity. To implement the above process, first obtain the maximum load power of the substation area power grid according to the electricity consumption power of all users in the substation area. Generally, the maximum open capacity is obtained by comparing the difference between the maximum load power of the substation area and the output power of the already connected photovoltaics. And the maximum load power of the substation area power grid is generally related to the total electricity consumption power of users. Therefore, the total electricity consumption power of all users in the substation area can be used to determine the maximum load power of the substation area power grid. In an exemplary embodiment, as Figure 4 shown, step 1 specifically includes:

[0081] Step 1-1: Obtain the maximum daily total electricity consumption of users according to the daily total electricity consumption of users in the preset historical time period of the substation area.

[0082] Obtain the daily total electricity consumption of users in the preset historical time period of the substation area. The daily total electricity consumption of users is the sum of the electricity consumption of all users on each day in the preset historical time period of the substation area.

[0083] Compare the daily total electricity consumption of users on each day in the preset historical time period of the substation area, and obtain the maximum value from it. The maximum value is the maximum daily total electricity consumption of users.

[0084] Step 1-2: Obtain the total electricity consumption power of users at each sampling moment on the target date corresponding to the maximum daily total electricity consumption of users.

[0085] Obtain the date corresponding to the maximum daily total electricity consumption of users according to the maximum daily total electricity consumption of users, that is, which day in the preset historical time period the maximum daily total electricity consumption of users corresponds to. Define the date corresponding to the maximum daily total electricity consumption of users as the target date.

[0086] Obtain the total electricity consumption power of users at each sampling moment on the target date. Specifically: Obtain the electricity consumption power of each user at each sampling moment on the target date. For any sampling moment, add up the electricity consumption powers of all users at this sampling moment to obtain the total electricity consumption power at this sampling moment, that is, the total electricity consumption power of users at this sampling moment. Thus, obtain the total electricity consumption power of users at each sampling moment on the target date. The calculation formula is as follows:

[0087] ;

[0088] Wherein, is the total power consumption of users at the th sampling moment within the target date, is the power consumption of the th user at the th sampling moment within the target date, and

[0089] Step 1-3: Based on the difference between the total power consumption of users at each sampling moment and the total power consumption of users at other sampling moments within the target date, obtain the relative grid load power at each sampling moment.

[0090] For any sampling moment, obtain the difference between the total power consumption of users at this sampling moment within the target date and the total power consumption of users at other sampling moments within the target date. This difference is the relative grid load power, which characterizes the power difference between this sampling moment and other sampling moments. The calculation formula is as follows:

[0091] ;

[0092] where, is the relative grid load power at the th sampling moment, is the total power consumption of users at the th sampling moment, is the number of sampling moments within the target date, and m - 1 represents the number of sampling moments within the target date other than the th sampling moment.

[0093] By using the above method, obtain the difference between the total power consumption of users at each sampling moment and the total power consumption of users at other sampling moments within the target date, that is, obtain the relative grid load power at each sampling moment.

[0094] The larger is, the greater the degree of the total power consumption of users at the

[0095] th sampling moment relative to other sampling moments.

[0096] After obtaining the relative grid load power at each sampling moment, obtain the maximum relative grid load power from them, and take the total power consumption of users at the sampling moment corresponding to the maximum relative grid load power as the maximum load power of the district grid.

[0097] Step 2: Based on the maximum load power of the district grid and the total photovoltaic load power already connected to the grid, obtain the maximum available capacity of the district grid.

[0098] The maximum openable capacity of the substation area power grid can be calculated by subtracting the total load power of the photovoltaic power sources already connected to the substation area power grid from the maximum load power of the substation area power grid. Then, the difference between the maximum load power of the substation area power grid and the total load power of the photovoltaic power sources already connected to the power grid is used as the maximum openable capacity of the substation area power grid. The calculation formula is as follows:

[0099] ;

[0100] Wherein, is the maximum openable capacity of the substation area power grid, is the maximum load power of the substation area power grid, is the total load power of the photovoltaic power sources already connected to the substation area power grid. Among them, the process of obtaining the total load power of the photovoltaic power sources already connected to the power grid can be: first obtain the load power of each photovoltaic module already connected to the substation area power grid, and then calculate the sum of the load powers of all the photovoltaic modules already connected to the substation area power grid to obtain the total load power of the photovoltaic power sources already connected to the substation area power grid.

[0101] Step 3: Based on the difference between the power of the users and the photovoltaic power sources within the preset historical time period of the substation area, obtain the photovoltaic accommodation matching degree of the substation area, and combine it with the frequency instability of the substation area power grid to obtain the substation area power grid capacity adjustment factor.

[0102] Step 2 obtains the maximum openable capacity of the substation area power grid. Then, next, based on the frequency instability of the substation area power grid and the photovoltaic accommodation matching degree of the substation area, adaptively adjust the maximum openable capacity of the substation area power grid to determine the actually connectable photovoltaic capacity, so as to connect as many distributed photovoltaic power generation systems as possible while ensuring the stable operation of the power grid.

[0103] Based on the difference between the power of the users and the photovoltaic power sources within the preset historical time period of the substation area, obtain the photovoltaic accommodation matching degree of the substation area. The photovoltaic accommodation matching degree of the substation area can measure the matching degree between the photovoltaic power generation and the power grid load demand in a power system. The larger the photovoltaic accommodation matching degree of the substation area, the closer the power consumption load of the substation area is to the photovoltaic power generation load, which means that the supply and demand of the substation area are more balanced and there is less need to connect additional distributed photovoltaics; the smaller the photovoltaic accommodation matching degree of the substation area, the less the photovoltaic power generation load meets the power consumption load, and more distributed photovoltaics can be connected.

[0104] In an exemplary embodiment, as Figure 5 shown, the process of obtaining the photovoltaic accommodation matching degree of the substation area includes:

[0105] Step 3-1: Obtain the total user power consumption sequence and the total photovoltaic power generation sequence.

[0106] Since the preset historical time period includes multiple sampling moments, obtain the total power consumption of users at each sampling moment within the preset historical time period of the power distribution area (calculated using the calculation method of the total power consumption of users in the above text). The total power consumption of users at each sampling moment within the preset historical time period of the power distribution area constitutes the total power consumption sequence of users. Then, the total power consumption sequence of users includes the total power consumption of users at each sampling moment within the preset historical time period of the power distribution area.

[0107] Obtain the total photovoltaic power generation of the photovoltaic systems connected to the power grid in the power distribution area at each sampling moment within the preset historical time period. The total photovoltaic power generation at each sampling moment within the preset historical time period of the power distribution area constitutes the total photovoltaic power generation sequence. Then, the total photovoltaic power generation sequence includes the total photovoltaic power generation at each sampling moment within the preset historical time period of the power distribution area.

[0108] It should be understood that if the photovoltaic systems connected to the power grid in the power distribution area include multiple photovoltaic modules, then obtain the power generation of each photovoltaic module in the power distribution area at each sampling moment within the preset historical time period, and then calculate the sum of the power generation of all photovoltaic modules in the power distribution area at each sampling moment within the preset historical time period to obtain the total photovoltaic power generation of all photovoltaic modules in the power distribution area at each sampling moment within the preset historical time period.

[0109] It should be noted that since photovoltaic modules only generate electricity effectively during the day, the above-mentioned each sampling moment within the preset historical time period is set as each sampling moment within each day of the preset historical time period.

[0110] Set as the total power consumption sequence of users, , is the total power consumption of users at the th sampling moment, Set as the total photovoltaic power generation sequence, is the total photovoltaic power generation at the th sampling moment.

[0111] Step 3-2: Obtain the power differences at each sampling moment in the total power consumption sequence of users and the total photovoltaic power generation sequence, and obtain the similarity between the total power consumption sequence of users and the total photovoltaic power generation sequence.

[0112] In an exemplary embodiment, the power difference at each sampling moment between the total user power consumption sequence and the total photovoltaic power generation sequence can be the absolute value of the power difference. The similarity between the total user power consumption sequence and the total photovoltaic power generation sequence can be obtained by using existing similarity calculation methods, such as cosine similarity, Pearson correlation coefficient, and so on. In other exemplary embodiments, the DTW distance between the total user power consumption sequence and the total photovoltaic power generation sequence can also be calculated, and then negative correlation processing can be performed to obtain the similarity.

[0113] Step 3-3: Obtain the matching degree of distribution network area photovoltaic power consumption according to the power difference and similarity.

[0114] The smaller the similarity between the total user power consumption sequence and the total photovoltaic power generation sequence, the greater the matching degree between the total user power consumption sequence and the total photovoltaic power generation sequence, that is, the greater the matching degree of distribution network area photovoltaic power consumption. Then, it is less necessary to connect additional distributed photovoltaics.

[0115] The greater the power difference at each sampling moment between the total user power consumption sequence and the total photovoltaic power generation sequence, the smaller the matching degree between the total user power consumption sequence and the total photovoltaic power generation sequence, that is, the smaller the matching degree of distribution network area photovoltaic power consumption. Then, it is more necessary to connect additional distributed photovoltaics. Therefore, the matching degree of distribution network area photovoltaic power consumption is inversely proportional to the power difference and directly proportional to the similarity.

[0116] In an exemplary embodiment, the calculation formula for the matching degree of distribution network area photovoltaic power consumption is:

[0117] ;

[0118] Wherein, is the matching degree of distribution network area photovoltaic power consumption, is the similarity between the total user power consumption sequence and the total photovoltaic power generation sequence, is the linear normalization function. M is the number of sampling moments in the preset historical time period.

[0119] represents the difference between the total user power consumption at the -th sampling moment and the total photovoltaic power generation at the -th sampling moment; represents the sum of the power differences at each sampling moment between the total user power consumption sequence and the total photovoltaic power generation sequence, that is, the overall situation of the power differences at each sampling moment between the total user power consumption sequence and the total photovoltaic power generation sequence.

[0120] is the negative correlation normalization of .

[0121] In this embodiment, normalization can be performed in a linear normalization manner or in the following normalization manner: , where z is the input data, and is the exponential function with the natural constant e as the base. The negative correlation normalization method can be: .

[0122] For the distribution network in a substation area, the frequency stability of the power grid refers to the ability of the power grid to maintain or restore to the normal frequency range and remain stable in the long term after being disturbed (such as load changes or generator failures). Therefore, the frequency stability of the power grid directly reflects the overall stability of the power grid. The higher the power grid stability, the more distributed photovoltaics can be accepted for connection. Conversely, the number of connected photovoltaics should be appropriately reduced. Correspondingly, the frequency instability of the distribution network in the substation area represents the fluctuation situation of the power grid. The higher the frequency instability of the distribution network in the substation area, the less distributed photovoltaics can be accepted for connection.

[0123] In an exemplary embodiment, the process of obtaining the frequency instability of the distribution network in the substation area is as Figure 6 shown and includes:

[0124] Step 3-4: Obtain the actual frequency of the user-side power grid at each sampling moment within the target date.

[0125] Obtain the actual frequency of the user-side power grid at each sampling moment within the target date obtained in Step 1, that is, the actual frequency of the user-side power grid of each user in the substation area at each sampling moment. It should be understood that power grid frequency detection devices are installed at each user in the substation area to detect the actual frequency of the user-side power grid of each user.

[0126] Step 3-5: Obtain the frequency instability of the distribution network in the substation area according to the difference between the actual frequency of the user-side power grid and the rated frequency of the distribution network in the substation area at each sampling moment within the target date.

[0127] Set the rated frequency of the distribution network in the substation area, which is a fixed known value, usually 50 Hz.

[0128] Obtain the difference between the actual frequency of the user-side power grid and the rated frequency of the distribution network in the substation area at each sampling moment within the target date. The greater the difference, the more unstable the frequency of the distribution network in the substation area, that is, the higher the frequency instability of the distribution network in the substation area. In an exemplary embodiment, the calculation formula for the frequency instability of the distribution network in the substation area is as follows:

[0129] ;

[0130] Where is the frequency instability of the distribution network in the substation area, is the kth user within the target date at the The actual frequency of the client grid at a sampling moment is the rated frequency of the substation area grid.

[0131] is the difference between the actual frequency of the client grid of the k-th user at the -th sampling moment within the target date and the rated frequency of the substation area grid.

[0132] Combining the real-time frequency deviations of all users , the larger its value, the higher the frequency instability of the substation area grid and the more unstable the grid frequency.

[0133] For the substation area grid, it is hoped that more distributed photovoltaics can be connected to the grid with higher frequency stability, that is, the corresponding value is smaller, then the actual accessible photovoltaic capacity is larger and closer to the maximum openable capacity. At the same time, combining the photovoltaic accommodation matching degree of the substation area, the smaller the photovoltaic accommodation matching degree of the substation area, it means that the photovoltaic power generation load does not meet the electricity load more, and more distributed photovoltaics need to be connected.

[0134] In an exemplary embodiment, as Figure 7 shown, the process of obtaining the substation area grid capacity adjustment factor includes:

[0135] Step 3-6: Normalize the photovoltaic accommodation matching degree of the substation area and the frequency instability of the substation area grid respectively.

[0136] Step 3-7: Calculate the product of the normalized photovoltaic accommodation matching degree of the substation area and the normalized frequency instability of the substation area grid to obtain the substation area grid capacity adjustment factor. The calculation formula is as follows:

[0137] ;

[0138] where is the substation area grid capacity adjustment factor.

[0139] Step 4: Adjust the maximum openable capacity of the substation area grid according to the grid capacity adjustment factor to obtain the actual accessible photovoltaic capacity of the substation area grid.

[0140] From the relevant logic of the grid capacity adjustment factor in Step 3, it can be seen that the larger the grid capacity adjustment factor, the more necessary it is to lower the maximum openable capacity of the substation area grid. Therefore, in an exemplary embodiment, the calculation formula for the actual accessible photovoltaic capacity of the substation area grid is as follows:

[0141] ;

[0142] where is the actual accessible photovoltaic capacity of the substation area grid, is the maximum openable capacity of the substation area power grid, is the power grid capacity adjustment factor.

[0143] The smaller the power grid capacity adjustment factor , the larger the actual photovoltaic capacity that can be connected to the substation area power grid, and vice versa, thereby improving the accuracy of the actual connectable capacity of the substation area power grid.

[0144] Then, the actual photovoltaic capacity that can be connected to the substation area power grid obtained can be used to connect the corresponding photovoltaic capacity. Moreover, the optimal photovoltaic connection method suitable for this substation area can be selected to provide scientific evaluation guidance for the openable capacity of distributed photovoltaics in the low-voltage substation area, support the grid connection planning of distributed photovoltaics, and ensure the safe and stable operation of the distributed photovoltaic substation area.

[0145] This embodiment also provides a system for evaluating the developable capacity of a distributed photovoltaic substation area, including: a memory and a processor; the memory is connected to the processor, and the memory is used to store program instructions; the processor is used to implement the steps in the embodiment of the method for evaluating the developable capacity of the distributed photovoltaic substation area when the program instructions are executed.

[0146] In an exemplary embodiment, the present invention provides a computer-readable storage medium storing a computer program, which when executed by a processor implements the steps in the embodiment of the method for evaluating the developable capacity of the distributed photovoltaic substation area.

[0147] It should be noted that: the above sequence of the embodiments of the present invention is only for description and does not represent the advantages and disadvantages of the embodiments. The processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0148] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

Claims

1. A method for evaluating the developable capacity of a distributed photovoltaic substation area, characterized in that Including: Obtain the maximum load power of the substation area power grid according to the electricity consumption powers of all users in the substation area; Obtain the maximum openable capacity of the substation area power grid according to the maximum load power of the substation area power grid and the total photovoltaic load power already connected to the power grid; Obtain the photovoltaic accommodation matching degree of the substation area according to the difference between the powers of users and photovoltaic in the preset historical time period of the substation area, and combine the frequency instability of the substation area power grid to obtain the power grid capacity adjustment factor of the substation area; Adjust the maximum openable capacity of the substation area power grid according to the power grid capacity adjustment factor to obtain the actual photovoltaic capacity that can be connected to the substation area power grid; Obtain the photovoltaic accommodation matching degree of the substation area according to the difference between the powers of users and photovoltaic in the preset historical time period of the substation area, including: Obtain the total user electricity consumption power sequence and the total photovoltaic power generation power sequence. The total user electricity consumption power sequence includes the total user electricity consumption power at each sampling moment in the preset historical time period of the substation area, and the total photovoltaic power generation power sequence includes the total photovoltaic power generation power at each sampling moment in the preset historical time period of the substation area; Obtain the power differences at each sampling moment in the total user electricity consumption power sequence and the total photovoltaic power generation power sequence, and obtain the similarity between the total user electricity consumption power sequence and the total photovoltaic power generation power sequence; Obtain the photovoltaic accommodation matching degree of the substation area according to the power difference and the similarity. The photovoltaic accommodation matching degree of the substation area is inversely proportional to the power difference and directly proportional to the similarity; The power difference is the absolute value of the power difference; the calculation formula of the photovoltaic accommodation matching degree of the substation area is: Among them, S is the matching degree of photovoltaic power consumption in the substation area, P u is the sequence of the total electricity consumption power of users, P g is the sequence of the total photovoltaic power generation, is the total electricity consumption power of users at the i-th sampling moment, is the total photovoltaic power generation at the i-th sampling moment, f(P u , P g ) is the similarity between the sequence of the total electricity consumption power of users and the sequence of the total photovoltaic power generation. norm is a linear normalization function, and M is the number of sampling moments in the preset historical time period. is the negative correlation normalization of ; The obtaining process of the power grid capacity adjustment factor of the substation area includes: Normalize the photovoltaic accommodation matching degree of the substation area and the frequency instability of the substation area power grid respectively; Calculate the product of the normalized photovoltaic accommodation matching degree of the substation area and the normalized frequency instability of the substation area power grid to obtain the power grid capacity adjustment factor of the substation area.

2. The method for evaluating the developable capacity of a distributed photovoltaic substation area according to claim 1, characterized in that Obtain the maximum load power of the substation area power grid according to the electricity consumption powers of all users in the substation area, including: Obtain the maximum daily total electricity consumption of users according to the daily total electricity consumption of users in the preset historical time period of the substation area; Obtain the total user electricity consumption power at each sampling moment in the target date corresponding to the maximum daily total electricity consumption of the users; Obtain the relative load power of the power grid at each sampling moment according to the difference between the total user electricity consumption power at each sampling moment and the total user electricity consumption powers at other sampling moments in the target date; Use the total user electricity consumption power at the sampling moment corresponding to the maximum relative load power of the power grid as the maximum load power of the substation area power grid; The calculation formula of the relative load power of the power grid at the i-th sampling moment is as follows: where P i ′ is the grid relative load power at the i-th sampling moment, and P j is the total power consumption of users at the j-th sampling moment. m is the number of sampling moments within the target date, and m - 1 represents the number of sampling moments within the target date except the i-th sampling moment. P i is the total power consumption of users at the i-th sampling moment within the target date, and [[0000059]] is the power consumption of the k-th user at the i-th sampling moment within the target date. n is the number of users in the transformer area.

3. The method for evaluating the developable capacity of a distributed photovoltaic substation area according to claim 1, characterized in that Obtain the maximum openable capacity of the substation area power grid according to the maximum load power of the substation area power grid and the total photovoltaic load power already connected to the power grid, including: Use the difference between the maximum load power of the substation area power grid and the total photovoltaic load power already connected to the power grid as the maximum openable capacity of the substation area power grid.

4. The assess method for developable capacity of a distributed photovoltaic substation area according to claim 2, characterized in that, The obtaining process of the frequency instability of the substation area power grid includes: Obtain the actual frequency of the user-side power grid at each sampling moment in the target date; Obtain the frequency instability of the distribution network in the area according to the difference between the actual frequency of the client-side power grid and the rated frequency of the distribution network in the area at each sampling moment within the target date; The calculation formula for the frequency instability of the distribution network in the area is as follows: where H is the frequency instability of the substation area power grid, is the actual frequency of the user-side power grid of the k-th user at the i-th sampling moment within the target date, and h0 is the rated frequency of the substation area power grid; The method for obtaining the actual voltage of photovoltaic power generation at any sampling moment is: obtain the actual voltage of each photovoltaic module in the area at this sampling moment, and calculate the average value of the actual voltages of all photovoltaic modules in the area at this sampling moment as the actual voltage of photovoltaic power generation at this sampling moment; Obtain the actual voltage of photovoltaic power generation at each sampling moment within the date, and then calculate the average value of the actual voltages of photovoltaic power generation at all sampling moments within the date to obtain the actual average voltage of photovoltaic power generation.

5. The method for evaluating the developable capacity of a distributed photovoltaic substation area according to claim 1, characterized in that Adjust the maximum openable capacity of the distribution network in the area according to the grid capacity adjustment factor to obtain the actual accessible photovoltaic capacity of the distribution network in the area, including: The calculation formula for the actual accessible photovoltaic capacity of the distribution network in the area is as follows: P S = P r × (1 - γ); Among them, P S is the actual accessible PV capacity of the distribution network in the substation area, and P r is the maximum openable capacity of the distribution network in the substation area, and γ is the grid capacity adjustment factor.

6. The method for evaluating the developable capacity of a distributed photovoltaic substation area according to claim 1, characterized in that, Before obtaining the maximum load power of the distribution network in the area according to the electricity consumption power of all users in the area, the method for evaluating the developable capacity of the distributed photovoltaic area in the area further includes: Obtain the total photovoltaic power generation and total electricity consumption in the preset historical time period in the area; Obtain the maximum daily photovoltaic power generation in the preset historical time period, and obtain the actual average voltage of photovoltaic power generation on the date corresponding to the maximum daily photovoltaic power generation; If the total photovoltaic power generation is less than the total electricity consumption and the actual average voltage of photovoltaic power generation is within the preset stable voltage range of photovoltaic power generation, the area executes the step of obtaining the maximum load power of the distribution network in the area according to the electricity consumption power of all users in the area.

7. A developable capacity evaluation system for a distributed photovoltaic substation area, characterized by comprising: A memory and a processor; The memory is connected to the processor; The memory is used to store program instructions; The processor is used to implement the method for evaluating the developable capacity of the distributed photovoltaic area according to any one of claims 1-6 when the program instructions are executed.

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