A regional grid-connected protection control method for distributed photovoltaic power stations

Abstract

The present invention relates to the technical field of grid-connected control, and specifically discloses a method for regional grid-connected protection control of distributed photovoltaic power stations, comprising the following steps: S1: determining a collection period according to the time of receiving a grid-connected request, obtaining the amount of electricity transmitted to the grid by the grid-connected photovoltaic power station within the collection period, and calculating the transmission power; calculating the total power that can be connected to the grid; S2: determining a curve of the grid-connected electric power changing with time according to a curve of the power generation of the photovoltaic power station to be connected to the grid changing with time and a curve of the electric power consumption of the target user changing with time; S3: judging whether the grid-connected request of the photovoltaic power station to be connected to the grid is passed according to the total power to be connected to the grid, the curve of the grid-connected electric power changing with time and the minimum adjustable active power. The present invention improves the accuracy of judging whether the grid-connected request is passed and reduces the waste of electric power resources by considering the usage of users after the photovoltaic power station generates electricity.

Description

Technical Field

[0001] The present invention relates to the technical field of grid-connected protection, and in particular to a regional grid-connected protection control method for distributed photovoltaic power stations. Background Art

[0002] A distributed photovoltaic power station refers to a solar power generation system installed near the user, usually on the roof of a building or on an open space, for generating electricity and meeting the user's electricity needs. Compared with large-scale centralized photovoltaic power stations, distributed photovoltaic power stations are smaller in scale, generally ranging from a few kilowatts to several hundred kilowatts, and most of the electricity will be directly supplied to the user. The surplus electricity can be transmitted to the public power grid through grid connection, thus realizing the two-way flow of energy.

[0003] In a Chinese patent with the patent announcement number CN107017660B, a distributed photovoltaic power station regional grid-connected protection system and a grid-connected control method are disclosed. The scheme mainly includes receiving the grid-connected request of the photovoltaic power station to be grid-connected, and recording the minimum adjustable active power and current power generation collected by its photovoltaic collection / controller, and comparing and judging according to different conditions based on the minimum adjustable active power, current power generation and the current residual power of the transformer, and determining the grid-connected requirements of the photovoltaic power station requested to be grid-connected. However, in actual situations, the power generation of the photovoltaic power station to be grid-connected must first be supplied to users, and the remaining power will be transmitted to the public power grid through grid connection. The direct use of real-time power generation in the scheme ignores this problem, which may result in the rejection of the grid-connected request of the photovoltaic power station that can actually be grid-connected, resulting in a waste of power resources. Summary of the invention

[0004] The purpose of the present invention is to provide a regional grid-connected protection control method for distributed photovoltaic power stations to solve the above technical problems.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for controlling regional grid-connected protection of distributed photovoltaic power stations, comprising the following steps:

[0007] S1: Determine the time tcur when the central control device receives the grid connection request, and set the collection period [tcur-Δt, tcur], Δt is a preset time interval, obtain the amount of electricity Qtra transmitted to the grid by the grid-connected photovoltaic power station within the collection period, and calculate the transmission power Ptra=Qtra / Δt;

[0008] Calculate the total grid-connectable power , P' is the preset transformer power deviation value, Ptra j represents the transmission power of the jth grid-connected photovoltaic power station;

[0009] S2: periodically acquiring the power generation of the photovoltaic power station to be connected to the grid within the acquisition period, and drawing a curve f(t) showing the power generation of the photovoltaic power station to be connected to the grid changing with time;

[0010] The user who is powered by the proposed grid-connected photovoltaic power station is taken as the target user, the power consumption of the target user is periodically obtained within the acquisition period, and a curve f'(t)+Pret of the power consumption of the target user over time is drawn, where Pret represents a preset power consumption deviation value;

[0011] Obtain the curve of grid-connectable electric power changing with time g(t)=f(t)-f'(t)-Pret;

[0012] S3: judging whether the grid connection request of the photovoltaic power station to be connected to the grid is approved according to the total grid-connectable power, the curve of the grid-connectable electric power changing with time and the minimum adjustable active power.

[0013] As a further solution of the present invention: the step S2 further includes the following steps:

[0014] Draw a straight line passing through (0, min_Pi) and parallel to the x-axis, and use it as a reference line, and use the intersection of the reference line and the curve of the grid-connectable electric power changing with time as a reference point, and obtain the time interval between two adjacent reference points;

[0015] Between two adjacent reference points, when the curve of the grid-connectable electric power changing with time is above the reference line, the corresponding time interval is marked as a grid-connectable period;

[0016] Between two adjacent reference points, when the curve of the grid-connectable electric power changing with time is below the reference line, the corresponding time interval is marked as a non-grid-connectable period;

[0017] When the curve of the grid-connectable electric power changing with time overlaps with the reference line, the time period corresponding to the overlapping part is taken as the grid-connectable time period;

[0018] when When the grid connection request of the photovoltaic power station to be connected to the grid is rejected, Tfor represents the duration of the ath grid-connectable time period, and n represents the total number of grid-connectable time periods.

[0019] As a further solution of the present invention: in the step S3, it is determined whether the grid connection request of the proposed grid-connected photovoltaic power station is passed according to the total grid-connectable power, the curve of the grid-connectable electric power changing with time and the minimum adjustable active power:

[0020] When ΔP<min_Pi, the subsequent steps are not executed and the grid connection request of the photovoltaic power station to be grid-connected is rejected;

[0021] When ΔP ≥ min_Pi, perform the following steps:

[0022] when When the grid connection request of the photovoltaic power station to be connected to the grid is sent, the photovoltaic power station to be connected to the grid is allowed to connect to the grid. A command to connect to the grid as grid-connected power;

[0023] when When the grid connection request of the photovoltaic power station to be connected to the grid is received, a command is sent to allow the photovoltaic power station to be connected to the grid with ΔP as the grid connection power;

[0024] when When the grid connection request of the proposed grid-connected photovoltaic power station is rejected.

[0025] As a further solution of the present invention: in the step S1, when the number of grid connection requests received by the central control device during the collection period is not 1, the following steps are performed:

[0026] The proposed grid-connected PV power station whose grid-connection request is approved is taken as the target power station, and the total grid-connected power of the target power station is calculated. , g A (t) represents the curve of the grid-connectable power of the Ath target power station changing with time, and A' represents the total number of target power stations;

[0027] When the total grid-connected power PZH≤ΔP, a signal is sent to the Ath target power station to allow it to A command to connect to the grid as grid-connected power;

[0028] When the total grid-connected electric power PZH>ΔP, the grid-connected power of the target power station is calculated according to the fluctuation of the curve of the grid-connectable electric power changing with time.

[0029] As a further solution of the present invention: the process of determining the fluctuation of the curve of the grid-connectable electric power changing with time specifically includes:

[0030] The peak points and valley points on the curve of the grid-connectable electric power changing with time are taken as reference points, and the starting point and end point of the curve of the grid-connectable electric power changing with time are taken as reference points, and the difference of the grid-connectable electric power between two adjacent reference points is calculated, and it is taken as the fluctuation difference, and the total fluctuation difference ΔD;

[0031] Calculating Stability Score ;

[0032] ΔT represents the average time interval between two adjacent reference points, C represents the total number of reference points, δ represents a preset correction coefficient, and K' represents a preset fractional value;

[0033] The stability score is used as a standard to measure the fluctuation of the curve of the grid-connectable electric power changing with time.

[0034] As a further solution of the present invention, the process of calculating the grid-connected power of the target power station according to the fluctuation of the curve of the grid-connected electric power changing with time specifically includes:

[0035] Step 1: Calculate the grid-connected power of the Gth target power station , KG represents the fluctuation score corresponding to the Gth target power station;

[0036] Step 2: Sort the target power stations according to the corresponding grid-connected power. The larger the grid-connected power, the higher the ranking.

[0037] For the target power plant H that is ranked first in the ranking, when , perform the following steps:

[0038] According to the method in step 1, Allocate to the remaining target power plants in the ranking;

[0039] Send a signal to the target power station H to allow it to A command to connect to the grid as grid-connected power;

[0040] when When , a command is sent to the target power station H to allow it to connect to the grid using PHsyn as the grid-connected power;

[0041] Step 3: Remove the target power station H at the first place in the ranking, and repeat the step 2 until all the target power stations in the ranking have executed the step 2.

[0042] As a further solution of the present invention: in the step 1, when PGsyn<Gmin_Pi, the grid connection request of the Gth target power station is rejected, and the grid connection power of the remaining target power stations is recalculated, and Gmin_Pi represents the minimum adjustable active power of the Gth target power station.

[0043] As a further solution of the present invention: in the step S1, when the transmission power of the grid-connected photovoltaic power station Y is greater than the average transmission power, the duration TCX>TCX' during which the transmission power of the grid-connected photovoltaic power station Y is greater than the average transmission power is recorded, and the grid-connected power of each grid-connected photovoltaic power station is re-determined.

[0044] Beneficial effects of the present invention: In the present invention, after receiving a grid-connected request, a collection cycle is set and subsequent processing is performed. When the length of the collection cycle is short, the power generation power of the photovoltaic power station and the power consumption of the user will not fluctuate too much during the collection cycle. Therefore, it can be used to represent the power generation and power consumption in the next cycle. Δt can be determined by experience to calculate the transmission power of the photovoltaic power station that has been connected to the grid and determine the total power that can be connected to the grid. It can be understood that the power generation power of the photovoltaic power station needs to be supplied to the user first, and then the excess power is connected to the power grid. Therefore, the transmission power is directly calculated to determine the actual power transmission situation of the photovoltaic power station that has been connected to the grid, and the total power that can be connected to the grid is determined according to the actual power transmission situation, so as to prevent the power generation from being directly used. The grid connection requests of the remaining photovoltaic power stations that can actually be connected to the grid are rejected due to the rate, resulting in a waste of resources. P' can be set by experience to avoid grid overload caused by transmission power fluctuations, which may cause safety problems. Then, the curve of the grid-connectable electric power changing with time is determined, that is, the difference between the generated power and the consumed power. It is also used to avoid the grid connection requests of the accessible photovoltaic power stations being rejected due to excessive power (directly using the generated power). The role of Pret is to avoid the decrease of the grid-connectable power caused by the sudden increase in user power demand, which affects the overall stability of the power grid. Finally, it is determined whether the grid connection request of the photovoltaic power station to be connected to the grid is passed according to the total grid-connectable power, the curve of the grid-connectable electric power changing with time and the minimum adjustable active power. The present invention improves the accuracy of judging whether the grid connection request is passed and reduces the waste of electric power resources by considering the user's usage after the photovoltaic power station generates electricity. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The present invention will be further described below in conjunction with the accompanying drawings.

[0046] Figure 1 It is a flow chart of a method for regional grid-connected protection control of a distributed photovoltaic power station according to the present invention. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] See also Figure 1 As shown, the present invention is a method for regional grid-connected protection control of distributed photovoltaic power stations, comprising the following steps:

[0049] S1: Determine the time tcur when the central control device receives the grid connection request, and set the collection period [tcur-Δt, tcur], Δt is a preset time interval, obtain the amount of electricity Qtra transmitted to the grid by the grid-connected photovoltaic power station within the collection period, and calculate the transmission power Ptra=Qtra / Δt;

[0050] Calculate the total grid-connectable power , P' is the preset transformer power deviation value, Ptra j represents the transmission power of the jth grid-connected photovoltaic power station;

[0051] S2: periodically acquiring the power generation of the photovoltaic power station to be connected to the grid within the acquisition period, and drawing a curve f(t) showing the power generation of the photovoltaic power station to be connected to the grid changing with time;

[0052] The user who is powered by the proposed grid-connected photovoltaic power station is taken as the target user, the power consumption of the target user is periodically obtained within the acquisition period, and a curve f'(t)+Pret of the power consumption of the target user over time is drawn, where Pret represents a preset power consumption deviation value;

[0053] Obtain the curve of grid-connectable electric power changing with time g(t)=f(t)-f'(t)-Pret;

[0054] S3: judging whether the grid connection request of the photovoltaic power station to be connected to the grid is approved according to the total grid-connectable power, the curve of the grid-connectable electric power changing with time and the minimum adjustable active power.

[0055] It should be noted that after receiving the grid connection request, the collection cycle is set and subsequent processing is performed. When the collection cycle is short, the power generation power of the photovoltaic power station and the power consumption of the user will not fluctuate too much during the collection cycle. Therefore, it can be used to represent the power generation and power consumption in the next cycle. Δt can be determined by experience to calculate the transmission power of the photovoltaic power station that has been connected to the grid and determine the total power that can be connected to the grid. It can be understood that the power generation power of the photovoltaic power station must first be supplied to the user, and then the excess power will be connected to the power grid. Therefore, the transmission power is directly calculated to determine the actual power transmission situation of the photovoltaic power station that has been connected to the grid, and the total power that can be connected to the grid is determined according to the actual power transmission situation, so as to prevent the direct use of the power generation power to cause In fact, the grid-connected requests of the remaining photovoltaic power stations that can be connected to the grid are rejected, resulting in a waste of resources. P' can be set by experience to avoid grid overload caused by transmission power fluctuations, which may cause safety problems. Then, the curve of the grid-connected electric power changing with time is determined, that is, the difference between the generated power and the consumed power. This is also used to avoid the grid-connected requests of the accessible photovoltaic power stations being rejected due to excessive power (direct use of the generated power). The role of Pret is to avoid a decrease in the grid-connected power caused by a sudden increase in user electricity demand, which affects the overall stability of the grid. Finally, it is determined whether the grid-connected request of the proposed photovoltaic power station is approved based on the total grid-connected power, the curve of the grid-connected electric power changing with time, and the minimum adjustable active power.

[0056] In another preferred implementation of the present invention, the step S2 further includes the following steps:

[0057] Draw a straight line passing through (0, min_Pi) and parallel to the x-axis, and use it as a reference line, and use the intersection of the reference line and the curve of the grid-connectable electric power changing with time as a reference point, and obtain the time interval between two adjacent reference points;

[0058] Between two adjacent reference points, when the curve of the grid-connectable electric power changing with time is above the reference line, the corresponding time interval is marked as a grid-connectable period;

[0059] Between two adjacent reference points, when the curve of the grid-connectable electric power changing with time is below the reference line, the corresponding time interval is marked as a non-grid-connectable period;

[0060] When the curve of the grid-connectable electric power changing with time overlaps with the reference line, the time period corresponding to the overlapping part is taken as the grid-connectable time period;

[0061] when When the grid connection request of the photovoltaic power station to be connected to the grid is rejected, Tfor represents the duration of the ath grid-connectable time period, and n represents the total number of grid-connectable time periods.

[0062] It is worth noting that the grid-connected operation of a photovoltaic power station not only involves the power generation capacity of the power station itself, but also needs to consider the stability and security of the power grid. If the proportion of the time period that can be connected to the grid (that is, the time period when the grid-connected power is greater than the minimum adjustable active power) is less than 0.9, it means that the grid-connected power is less than the minimum adjustable active power in some time periods. If the grid is connected, it may cause grid instability.

[0063] In another preferred implementation of the present invention, in step S3, it is determined whether the grid connection request of the proposed grid-connected photovoltaic power station is passed according to the total grid-connectable power, the curve of the grid-connectable electric power changing with time and the minimum adjustable active power:

[0064] When ΔP<min_Pi, the subsequent steps are not executed and the grid connection request of the photovoltaic power station to be grid-connected is rejected;

[0065] When ΔP ≥ min_Pi, perform the following steps:

[0066] when When the grid connection request of the photovoltaic power station to be connected to the grid is sent, the photovoltaic power station to be connected to the grid is allowed to connect to the grid. A command to connect to the grid as grid-connected power;

[0067] when When the grid connection request of the photovoltaic power station to be connected to the grid is received, a command is sent to allow the photovoltaic power station to be connected to the grid with ΔP as the grid connection power;

[0068] when When the grid connection request of the proposed grid-connected photovoltaic power station is rejected.

[0069] In another preferred implementation of the present invention, in step S1, when the number of grid connection requests received by the central control device during the collection period is not 1, the following steps are performed:

[0070] The proposed grid-connected PV power station whose grid-connection request is approved is taken as the target power station, and the total grid-connected power of the target power station is calculated. , g A (t) represents the curve of the grid-connectable power of the Ath target power station changing with time, and A' represents the total number of target power stations;

[0071] When the total grid-connected power PZH≤ΔP, a signal is sent to the Ath target power station to allow it to A command to connect to the grid as grid-connected power;

[0072] When the total grid-connected electric power PZH>ΔP, the grid-connected power of the target power station is calculated according to the fluctuation of the curve of the grid-connectable electric power changing with time.

[0073] It should be noted that different processing strategies are determined by comparing PZH and ΔP. If PZH≤ΔP, all target power stations can be connected to the grid with the grid-connectable power within the acquisition period, and will not exceed the load limit of the transformer. If PZH>ΔP, the grid-connected power of the photovoltaic power station needs to be controlled to avoid exceeding the load limit of the transformer and causing safety problems.

[0074] Specifically, in the process of photovoltaic power station grid connection, the safety and stability of the power grid is crucial. As one of the key equipment of the power grid, the transformer's load limit determines the maximum allowable power of the grid-connected power station, which is used to avoid grid overload and optimize the utilization efficiency of power resources, thereby achieving safe operation of the power grid. If the total grid-connected power ΔP is less than or equal to the transformer's load limit PZH, it means that the power grid has sufficient capacity to accommodate the current photovoltaic power generation. At this time, all photovoltaic power stations can be connected to the grid normally and will not exceed the transformer's load limit, ensuring the safety and stability of the power grid.

[0075] When the calculated total grid-connected power ΔP is greater than the transformer load upper limit PZH, it means that the grid cannot accommodate all the generated power of the photovoltaic power station. The excess may cause the transformer to overload and cause safety problems. Therefore, the grid-connected power of the photovoltaic power station needs to be controlled to avoid unnecessary power abandonment and improve the safety and stability of the power grid.

[0076] In another preferred implementation of the present invention, the process of determining the fluctuation of the curve of the grid-connectable electric power changing with time specifically includes:

[0077] The peak points and valley points on the curve of the grid-connectable electric power changing with time are taken as reference points, and the starting point and end point of the curve of the grid-connectable electric power changing with time are taken as reference points, and the difference of the grid-connectable electric power between two adjacent reference points is calculated, and it is taken as the fluctuation difference, and the total fluctuation difference ΔD;

[0078] Calculating Stability Score ;

[0079] ΔT represents the average time interval between two adjacent reference points, C represents the total number of reference points, δ represents a preset correction coefficient, and K' represents a preset fractional value;

[0080] The stability score is used as a standard to measure the fluctuation of the curve of the grid-connectable electric power changing with time.

[0081] In another preferred implementation of the present invention, the process of calculating the grid-connected power of the target power station according to the fluctuation of the curve of the grid-connectable electric power changing with time specifically includes:

[0082] Step 1: Calculate the grid-connected power of the Gth target power station , KG represents the fluctuation score corresponding to the Gth target power station;

[0083] Step 2: Sort the target power stations according to the corresponding grid-connected power. The larger the grid-connected power, the higher the ranking.

[0084] For the target power plant H that is ranked first in the ranking, when , perform the following steps:

[0085] According to the method in step 1, Allocate to the remaining target power plants in the ranking;

[0086] Send a signal to the target power station H to allow it to A command to connect to the grid as grid-connected power;

[0087] when When , a command is sent to the target power station H to allow it to connect to the grid using PHsyn as the grid-connected power;

[0088] Step 3: Remove the target power station H at the first place in the ranking, and repeat the step 2 until all the target power stations in the ranking have executed the step 2.

[0089] It is understandable that the stability score is used to measure the fluctuation of the grid-connected power of a photovoltaic power station within a certain period of time. A photovoltaic power station with a high stability score has a more uniform power generation and will not experience large fluctuations, which is very beneficial for grid-connected operation. Therefore, it can be given a higher grid-connected power without worrying about the adverse effects of power fluctuations on the grid. At the same time, according to and By making comparisons and performing different operations based on the comparison results, you can avoid grid overload and reduce power abandonment, thereby reducing resource waste.

[0090] In another preferred implementation of the present invention, in step 1, when PGsyn<Gmin_Pi, the grid connection request of the Gth target power station is rejected, and the grid connection power of the remaining target power stations is recalculated, and Gmin_Pi represents the minimum adjustable active power of the Gth target power station.

[0091] In another preferred implementation of the present invention, in the step S1, when the transmission power of the grid-connected photovoltaic power station Y is greater than the average transmission power, the duration TCX>TCX' during which the transmission power of the grid-connected photovoltaic power station Y is greater than the average transmission power is recorded, and the grid-connected power of each grid-connected photovoltaic power station is re-determined.

[0092] The above is a detailed description of an embodiment of the present invention, but the content is only a preferred embodiment of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A method for regional grid-connected protection control of distributed photovoltaic power stations, characterized in that: The following steps are involved: S1: Determine the time tcur when the central control device receives the grid connection request, and set the collection period [tcur-Δt, tcur], Δt is a preset time interval, obtain the amount of electricity Qtra transmitted to the grid by the grid-connected photovoltaic power station within the collection period, and calculate the transmission power Ptra=Qtra / Δt; Calculate the total grid-connectable power P' is the preset transformer power deviation value, and Ptraj represents the transmission power of the jth grid-connected photovoltaic power station; S2: periodically acquiring the power generation of the photovoltaic power station to be connected to the grid within the acquisition period, and drawing a curve f(t) showing the power generation of the photovoltaic power station to be connected to the grid changing with time; The power consumption of the intended grid-connected user is periodically acquired during the acquisition period, and a curve f'(t)+Pret showing the power consumption of the intended grid-connected user changing with time is drawn, where Pret represents a preset power consumption deviation value; Obtain a curve of the grid-connectable electric power changing with time g(t)=f(t)-f'(t)-Pret; S3: judging whether the grid connection request of the proposed grid-connected photovoltaic power station is approved according to the total grid-connectable power, the curve of the grid-connectable electric power changing with time and the minimum adjustable active power; Determine whether the grid connection request of the proposed grid-connected photovoltaic power station is passed according to the total grid-connectable power, the curve of the grid-connectable electric power changing with time and the minimum adjustable active power: When ΔP<min_Pi, the subsequent steps are not executed and the grid connection request of the photovoltaic power station to be grid-connected is rejected; When ΔP ≥ min_Pi, perform the following steps: when When the grid connection request of the photovoltaic power station to be connected to the grid is sent, the photovoltaic power station to be connected to the grid is allowed to connect to the grid. A command to connect to the grid as grid-connected power; when When the grid connection request of the photovoltaic power station to be connected to the grid is received, a command is sent to allow the photovoltaic power station to be connected to the grid with ΔP as the grid connection power; when When the grid connection request of the proposed grid-connected photovoltaic power station is rejected.

2. A method for regional grid-connected protection control of distributed photovoltaic power stations according to claim 1, characterized in that: The step S2 further includes the following steps: Draw a straight line passing through (0, min_Pi) and parallel to the x-axis, and use it as a reference line, and use the intersection of the reference line and the curve of the grid-connectable electric power changing with time as a reference point, and obtain the time interval between two adjacent reference points; Between two adjacent reference points, when the curve of the grid-connectable electric power changing with time is above the reference line, the corresponding time interval is marked as a grid-connectable period; Between two adjacent reference points, when the curve of the grid-connectable electric power changing with time is below the reference line, the corresponding time interval is marked as a non-grid-connectable period; When the curve of the grid-connectable electric power changing with time overlaps with the reference line, the time period corresponding to the overlapping part is taken as the grid-connectable time period; when When the grid connection request of the proposed grid-connected photovoltaic power station is rejected, Tfora represents the duration of the ath grid-connectable time period, and n represents the total number of grid-connectable time periods.

3. A method for regional grid-connected protection control of distributed photovoltaic power stations according to claim 1, characterized in that: In the step S1, when the number of grid connection requests received by the central control device during the collection period is not 1, the following steps are performed: The proposed grid-connected PV power station whose grid-connection request is approved is taken as the target power station, and the total grid-connected power of the target power station is calculated. g A (t) represents the curve of the grid-connectable electric power of the Ath target power station changing with time, and A' represents the total number of target power stations; When the total grid-connected power PZH≤ΔP, a signal is sent to the Ath target power station to allow it to A command to connect to the grid as grid-connected power; When the total grid-connected electric power PZH>ΔP, the grid-connected power of the target power station is calculated according to the fluctuation of the curve of the grid-connectable electric power changing with time.

4. A method for regional grid-connected protection control of distributed photovoltaic power stations according to claim 3, characterized in that: The process of determining the fluctuation of the curve of the grid-connectable electric power changing with time specifically includes: The peak points and valley points on the curve of the grid-connectable electric power changing with time are taken as reference points, and the starting point and end point of the curve of the grid-connectable electric power changing with time are taken as reference points, and the difference of the grid-connectable electric power between two adjacent reference points is calculated, and it is taken as the fluctuation difference, and the total fluctuation difference ΔD; Calculating Stability Score ΔT represents the average time interval between two adjacent reference points, C represents the total number of reference points, δ represents a preset correction coefficient, and K' represents a preset fractional value; The stability score is used as a standard to measure the fluctuation of the curve of the grid-connectable electric power changing with time.

5. A method for regional grid-connected protection control of distributed photovoltaic power stations according to claim 4, characterized in that: The process of calculating the grid-connected power of the target power station according to the fluctuation of the curve of the grid-connected electric power changing with time specifically includes: Step 1: Calculate the grid-connected power of the Gth target power station KG represents the fluctuation score corresponding to the Gth target power station; Step 2: Sort the target power stations according to the corresponding grid-connected power. The larger the grid-connected power, the higher the ranking. For the target power plant H that is ranked first in the ranking, when , perform the following steps: According to the method in step 1, Allocate to the remaining target power plants in the ranking; Send a signal to the target power station H to allow it to A command to connect to the grid as grid-connected power; when When , a command is sent to the target power station H to allow it to connect to the grid using PHsyn as the grid-connected power; Step 3: Remove the target power station H at the first place in the ranking, and repeat the step 2 until all the target power stations in the ranking have executed the step 2.

6. A method for regional grid-connected protection control of distributed photovoltaic power stations according to claim 5, characterized in that: In the step 1, when PGsyn<Gmin_Pi, the grid connection request of the Gth target power station is rejected, and the grid connection power of the remaining target power stations is recalculated, and Gmin_Pi represents the minimum adjustable active power of the Gth target power station.

7. A method for regional grid-connected protection control of distributed photovoltaic power stations according to claim 6, characterized in that: In the step S1, when the transmission power of the grid-connected photovoltaic power station Y is greater than the average transmission power, the duration TCX during which the transmission power of the grid-connected photovoltaic power station Y is greater than the average transmission power is recorded, and when TCX>TCX', the grid-connected power of each grid-connected photovoltaic power station is re-determined, and TCX' represents a preset duration threshold.

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