Investment evaluation method for distribution network planning and construction considering substation on-off grid demand

Abstract

This invention relates to the field of distribution network investment technology and discloses a method for evaluating the planning and construction investment of distribution networks considering the grid connection and disconnection needs of substations. The method includes the following steps: First, collecting historical operating data of substations and judging their status; Second, predicting the future load development of substations in the grid-connected state based on historical operating data; Third, predicting the future load development of substations in the grid-connected state based on historical operating data and the capacity ratio of distributed photovoltaic power generation; Fourth, analyzing whether the predicted substation load development results meet the distribution network operation requirements for the target year; Fifth, evaluating and analyzing the investment effect of the distribution network based on the analysis results and the substation renovation and expansion situation. This invention has the advantages of realizing dynamic prediction of future distribution network investment benefits, facilitating reasonable rolling adjustments to distribution network construction investment plans, and improving distribution network investment efficiency.

Description

Technical Field

[0001] This invention relates to a method for evaluating the investment in the planning and construction of distribution networks that takes into account the uplink and downlink requirements of substations, and belongs to the technical field of distribution network investment. Background Technology

[0002] Investment is a crucial means of developing power distribution networks, and the quality of these developments is closely related to the quality of investment. High-quality development requires high-quality industries and a high-quality environment, which in turn require high-quality investment. Researching high-quality investment is an effective strategy for adapting to the new normal of the economy, a key lever for achieving technological innovation, promoting industrial upgrading, and cultivating new growth drivers, and a major measure for addressing development shortcomings and resolving imbalances and inadequacies in development. Therefore, how to formulate power grid performance, analyze the collaborative performance measurement and improvement paths of the internal and external value chains of the power grid, and realize the economic, environmental, social, and safety benefits brought about by power grid investment are currently key tasks for power grid companies.

[0003] Currently, traditional methods for evaluating the benefits of power grid investment often rely solely on historical evaluation indicators to calculate the benefits of historical power grid investments. For example, Chinese patent application publication number CN111178676A discloses a method and system for evaluating the investment of distribution network projects. This invention patent application calculates the benefits of historical power grid investments using historical indicators, which presents the problem of difficulty in dynamically predicting future power grid investment benefit indicators. Summary of the Invention

[0004] To address the aforementioned problems in existing technologies, this invention provides a method for evaluating investment in distribution network planning and construction that considers the uplink and downlink requirements of substations.

[0005] The technical solution of the present invention is as follows:

[0006] A method for evaluating the investment in distribution network planning and construction that considers the uplink and downlink requirements of substations includes the following steps:

[0007] Step 1: Collect historical operating data of the substation and assess its status;

[0008] The specific method is as follows: calculate the substation power using the following formula:

[0009] (1)

[0010] In the formula, Indicates the substation power. Indicates the load in the substation's power supply area. This indicates the power of new energy sources within the substation's power supply area. Indicates the energy storage capacity within the substation's power supply area;

[0011] when When, it indicates that the substation energy storage is in a discharging state; when When this time is reached, it indicates that the substation's energy storage is in a charging state. When, it indicates that the substation is in a grid-connected state; when When the time is specified, it indicates that the substation is in the offline state.

[0012] Step 2: Predict future load development of substations in the offline state based on historical substation operation data;

[0013] The specific method is as follows:

[0014] Calculate the load factor of the substation in the distribution network As shown in the following formula:

[0015] (2)

[0016] In the formula, This indicates the substation's grid load rate. This indicates the maximum load that the substation can supply to the grid. Indicates the number within the substation i The rated capacity of the transformer Indicates the number of transformers in the substation;

[0017] When the largest capacity main transformer in the substation experiences an N-1 fault, the substation's load factor is [missing information - likely a percentage], without considering load transfer. As shown in the following formula.

[0018] (3)

[0019] In the formula, This represents the substation load rate after the maximum capacity main transformer experiences an N-1 fault. This represents the total capacity of a substation with N transformers. This indicates the maximum capacity of the main transformer within the substation.

[0020] In the actual process of analyzing and diagnosing power grid problems, it is generally believed that the downstream substations are considered to be Even after adjusting the operating mode, the substation will still experience overload. Therefore, the only solution to the substation overload problem is to renovate or expand the substation.

[0021] Peak load typically occurs at night, when renewable energy output is lower, and energy storage alleviates the power supply pressure on the substation's main transformer by discharging. Based on historical data from the past 5 years, the load growth of the substation over those 5 years was calculated using the following formula:

[0022] (5)

[0023] (6)

[0024] In the formula, This indicates the growth rate of the load over the past 5 years. This indicates the maximum load status of the substation. This indicates that the substation has been the first in the past 5 years. j The maximum load of the year j =0,1,2,3,4,5;

[0025] For the substation j Maximum annual load growth rate The calculation is performed using the following formula:

[0026] (7)

[0027] (8)

[0028] (9)

[0029] In the formula, This indicates the maximum load growth rate of the substation. Indicates the substation number j Maximum annual load growth rate j =0,1,2,3,4,5 This indicates that the substation has been the first in the past 5 years. j The maximum load of the year j =0,1,2,3,4,5 This represents the average growth rate of the substation's maximum load over the past 5 years.

[0030] Assume the maximum capacity main transformer in the substation generates In the event of a fault, what impact will this have on the future of the substation? m The annual load factor is calculated using the following formula:

[0031] (10)

[0032] (11)

[0033] In the formula, Indicates the first m Load rate of the substation's maximum capacity main transformer N-1 after the New Year. This indicates the maximum load that the substation can supply to the grid. This indicates the power of new energy sources within the substation's power supply area. Indicates the energy storage capacity within the substation's power supply area. This indicates the maximum load growth rate of the substation. This represents the total capacity of a substation with N transformers. This indicates the maximum capacity of the main transformer within the substation. This indicates the growth rate of the load over the past 5 years. This represents the average growth rate of the substation's maximum load over the past 5 years.

[0034] Step 3: Based on the historical operation data of the substation and the capacity ratio of distributed photovoltaic, predict the future load development of the substation in grid-connected status;

[0035] The specific method is as follows:

[0036] With the development of distributed photovoltaic power, some substations will experience grid connection during the midday period, i.e. At this time, the substation's on-grid load rate is... As shown in the following formula.

[0037] (12)

[0038] Under normal operating conditions, when a substation experiences an overload of its grid connection, i.e. At that time, it is necessary to upgrade and expand the capacity of the main transformer of the substation.

[0039] The peak power generation period for photovoltaic (PV) systems is typically between 10:00 AM and 3:00 PM daily. The development of distributed PV will change its capacity-to-distribution ratio, meaning the ratio of DC-side PV module capacity to inverter rated capacity will be greater than 1, as shown in the following formula.

[0040] (13)

[0041] In the formula, Indicates the capacity ratio of distributed photovoltaic power generation. Indicates the capacity of the DC-side photovoltaic modules in a distributed photovoltaic system. This indicates the rated capacity of the inverter.

[0042] Because renewable energy output is characterized by randomness, fluctuation, and intermittency, the simultaneous output rate of renewable energy will change after considering the photovoltaic capacity ratio. Therefore, the calculation formula (12) for the substation grid load rate becomes:

[0043] (14)

[0044] In the formula, This represents the simultaneous output rate coefficient of distributed photovoltaic power.

[0045] Similarly, by analyzing the average load characteristics and growth rate of the substation during the period from 10:00 AM to 3:00 PM over the past five years, the load curve for each future year is predicted. During this period, energy storage is in a charging state. Simultaneously, the distributed photovoltaic (PV) installed capacity for each future year is analyzed. Considering the capacity ratio, the existing distributed PV output characteristics are superimposed to obtain the output characteristic curve of distributed PV during the period from 10:00 AM to 3:00 PM in the target future year. The simultaneous output rate of distributed PV within the substation's power supply area in the target future year is shown in the following formula.

[0046] (15)

[0047] In the formula, Indicates the first m Annual distributed photovoltaic power output simultaneous rate coefficient Indicates the first m The constant output value of distributed photovoltaic power during the annual distributed photovoltaic power output period.

[0048] To ensure that the output of distributed photovoltaic power can be maintained at a constant value during the period from 10:00 AM to 3:00 PM, the following formula is used.

[0049] (16)

[0050] In the formula, This indicates the first [unit / item] within the time period from 10:00 AM to 3:00 PM, considering the capacity ratio of distributed photovoltaic systems. k Data points were collected at 15-minute intervals.

[0051] Based on the analysis of equations (15) and (16), equation (14) can be transformed into equation (17). Meanwhile, considering that the distributed photovoltaic output remains constant during the period from 10:00 AM to 3:00 PM, the transformer will not be overloaded when an N-1 fault occurs, as shown in equation (18).

[0052] (17)

[0053] (18)

[0054] In the formula, This indicates the target annual on-grid load rate of the substation. This represents the load growth rate of the substation during the period from 10:00 AM to 3:00 PM. The solution method is the same as that of equations (5) to (9) and equation (11), as follows: The calculation formula is:

[0055]

[0056]

[0057]

[0058]

[0059]

[0060]

[0061]

[0062] In the formula, This indicates the load growth rate of the substation during the period when distributed photovoltaic power is being generated. Indicates the substation number j Annual load growth rate j =0,1,2,3,4,5 This indicates that the substation has been the first in the past 5 years. j Annual load of substations during distributed photovoltaic power generation periods j =0,1,2,3,4,5 This indicates the load growth rate of the substation during the period of distributed photovoltaic power generation;

[0063] Indicates the load in the substation's power supply area. Indicates the energy storage capacity within the substation's power supply area. Indicates the first m Maximum simultaneous rate coefficient of annual distributed photovoltaic power output Indicates the first m Annual distributed photovoltaic power output simultaneous rate coefficient Indicates the first m Annual rated capacity of distributed photovoltaic inverters This represents the total capacity of a substation with N transformers. This indicates the maximum capacity of the main transformer within the substation.

[0064] Step 4: Analyze whether the predicted substation load development results meet the distribution network operation requirements for the target year; that is, set... At that time, the substation in the offline state could not meet the requirements of the first m The annual operation requirements of the power distribution network necessitate renovation and expansion.

[0065] set up At that time, the substation in the online state could not meet the requirements of the first... m The annual operation requirements of the power distribution network necessitate renovation and expansion.

[0066] Step 5: Based on the analysis results and the substation renovation and expansion situation, evaluate and analyze the investment effect of the distribution network.

[0067] Based on equations (10) and (17), the time when the target year cannot meet the substation's grid connection demand can be obtained. The future number of substations can be obtained by solving equation (10). The current substation cannot meet the substation grid connection requirements; by solving equations (17) and (18), the future number of substations can be obtained. The substation cannot meet the grid connection requirements of the substation.

[0068] Let the investment value for substation renovation and expansion be F. Calculate the annual distribution network investment value to meet the needs of substations in both offline and grid-connected states. The calculation formula is as follows:

[0069] (19)

[0070] (20)

[0071] In the formula, This represents the annual grid investment value required to meet the needs of substations in the off-grid status. Indicates the first The old substations could not meet the requirements of the distribution network operation. This represents the annual investment value required to meet the grid connection requirements of substations. Indicates the first Substations that are not in service with the grid for the year cannot meet the requirements of the distribution network operation;

[0072] Propose and calculate the investment evaluation indicators for power distribution networks. The calculation formula is:

[0073] (twenty one)

[0074] In the formula, This indicates that the substation was in the planning stage at the [number]th [year]. The initial investment value for the renovation and expansion in [year], Indicates the future planning stage of the substation The renovation and expansion were carried out in 2008. This represents the annual grid investment value required to meet the needs of substations in the off-grid status. This represents the annual investment value required to meet the grid connection requirements of substations.

[0075] This indicator can be used to assess the overall investment effectiveness of power grid substation construction in terms of grid connection and grid disconnection needs. The larger the value, the better the investment return and the higher the efficiency of the integrated power grid construction.

[0076] The present invention has the following beneficial effects:

[0077] This invention predicts the future load development of substations in the offline state based on historical operating data. It also calculates the output simultaneity coefficient change of distributed photovoltaic (PV) systems, while meeting the output demand of PV, based on historical operating data. This predicts the future load development of substations in the grid-connected state. Finally, it analyzes whether substations in both states meet the grid operation requirements of the target year and evaluates the grid investment effect based on substation renovation and expansion. This effectively reflects the investment benefits of the distribution network. Compared with existing technologies, it achieves dynamic prediction of future distribution network investment benefits, which is conducive to the reasonable rolling adjustment of distribution network construction investment plans and can improve the investment efficiency of the distribution network. Attached Figure Description

[0078] Figure 1 This is a schematic diagram of the process of the present invention;

[0079] Figure 2 The example shows the load curve for the substation on the day of maximum load.

[0080] Figure 3 The example shows the daily load curve of the maximum load area of ​​the substation.

[0081] Figure 4 This example shows the output of new energy sources on the day of maximum load in the substation's power supply area.

[0082] Figure 5 The output curve of the distributed photovoltaic system and the load curve of the power supply area are shown in the example for the fifth year in the future. Detailed Implementation

[0083] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0084] Example:

[0085] Taking a substation in a provincial power grid as an example, this substation has two 120MVA main transformers. Currently, the distributed photovoltaic capacity ratio in the substation's power supply area is 1, with a distributed photovoltaic module capacity of approximately 200MW and a wind power installed capacity of approximately 200MW. The maximum load in 2022 was 161.23MW. The load curve of this substation on the day of the maximum load is shown below. Figure 1 As shown, the load curve of the substation's power supply area is as follows: Figure 2 As shown.

[0086] The output of renewable energy at the substation on the day of maximum load is as follows: Figure 3As shown in the figure, when the substation experiences its maximum load, the photovoltaic output is 0, and the renewable energy output mainly comes from wind power. Between 10:00 AM and 3:00 PM, wind power output is low, and renewable energy output mainly comes from distributed photovoltaic systems, with a simultaneous rate of 0.4 under the condition that the requirements are met.

[0087] Considering the substation's grid connection, the load factor of the main transformer N-1 is 134.36%. Based on historical data analysis over the past 5 years, the load growth rate of this substation is [value missing]. Therefore, according to the formula:

[0088]

[0089] It can be calculated that the requirements for meeting the offline network requirements can be met. .

[0090] According to the formula:

[0091]

[0092] Considering the future distributed photovoltaic capacity ratio in this region The annual increase in distributed generation capacity is 143MW. Considering the load growth in the substation's service area, the load and renewable energy output are analyzed year by year. Analysis and calculation show that the capacity to meet grid connection demand is [not specified]. .at this time The load curve of the power supply area and the output curve of distributed photovoltaic power are as follows: Figure 4 As shown.

[0093] Assuming the investment value for substation renovation and expansion meets the requirements The substation was renovated and expanded in the third year of the initial planning, therefore the investment evaluation indicators for the distribution network... for:

[0094]

[0095] As can be seen from the above formula, when the substation is renovated and expanded according to the grid connection demand, its comprehensive investment benefit is 0.6, which means that the worst comprehensive benefit index of the substation renovation and expansion can be considered to be 0.6.

[0096] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for evaluating the investment in distribution network planning and construction, considering the uplink and downlink requirements of substations, characterized in that: Includes the following steps: Step A1: Collect historical operating data of the substation and determine the substation status; The judgment methods include: The power of the substation is calculated using the following formula: In the formula, Indicates the substation power. Indicates the load in the substation's power supply area. This indicates the power of new energy sources within the substation's power supply area. Indicates the energy storage capacity within the substation's power supply area; when When, it indicates that the substation energy storage is in a discharging state; when When, it indicates that the substation energy storage is in a charging state; when When, it indicates that the substation is in a grid-connected state; when When this time, it indicates that the substation is in the offline state. Step A2: Predict the future load development of substations in the offline state based on historical substation operation data; Prediction methods include: Based on the historical data of the substation over the past 5 years, the load growth of the substation over the past 5 years was calculated using the following formula: In the formula, This indicates the growth rate of the load over the past 5 years. This indicates the maximum load status of the substation. This indicates that the substation has been the first in the past 5 years. j The maximum load of the year j =0,1,2,3,4,5; For the substation j Maximum annual load growth rate The calculation is performed using the following formula: In the formula, This indicates the maximum load growth rate of the substation. Indicates the substation number j Maximum annual load growth rate j =0,1,2,3,4,5 This indicates that the substation has been the first in the past 5 years. j The maximum load of the year j =0,1,2,3,4,5 This represents the average growth rate of the substation's maximum load over the past 5 years. Assume the maximum capacity main transformer in the substation generates In the event of a fault, what impact will this have on the future of the substation? m The annual load factor is calculated using the following formula: In the formula, Indicates the first m Load rate of the substation's maximum capacity main transformer N-1 after the New Year. This indicates the maximum load that the substation can supply to the grid. This indicates the power of new energy sources within the substation's power supply area. Indicates the energy storage capacity within the substation's power supply area. This indicates the maximum load growth rate of the substation. This represents the total capacity of a substation with N transformers. This indicates the maximum capacity of the main transformer within the substation. This indicates the growth rate of the load over the past 5 years. This represents the average growth rate of the substation's maximum load over the past 5 years. Step A3: Based on the historical operating data of the substation and the capacity ratio of distributed photovoltaic power, predict the future load development of the substation in grid-connected status; Prediction methods include: The capacity ratio of distributed photovoltaic systems is calculated using the following formula: In the formula, Indicates the capacity ratio of distributed photovoltaic power generation. Indicates the capacity of the DC-side photovoltaic modules in a distributed photovoltaic system. Indicates the rated capacity of the inverter; Based on the substation's historical data from the past 5 years, we will analyze the substation's future... m The annual distributed photovoltaic power output simultaneity rate is calculated using the following formula: In the formula, Indicates the first m Annual distributed photovoltaic power output simultaneous rate coefficient Indicates the first m The constant output value of distributed photovoltaic power generation during the annual distributed photovoltaic power generation period; The calculation formula is: In the formula, Indicates the first m The constant output value of distributed photovoltaic power generation during the annual distributed photovoltaic power generation period. This indicates that the download of the first distributed photovoltaic (PV) output period takes into account the capacity ratio of distributed PV systems. k Data points were collected at 15-minute intervals. Indicates the rated capacity of the inverter; Step A4: Analyze whether the predicted substation load development results meet the distribution network operation requirements for the future target year; Step A5: Evaluate and analyze the investment effect of the distribution network based on the analysis results and the substation renovation and expansion situation.

2. The method for evaluating the investment in distribution network planning and construction considering the uplink and downlink requirements of substations, as described in claim 1, is characterized in that: The prediction method in step A3 includes: Based on the actual peak photovoltaic power generation period, the distributed photovoltaic power output period is set from 10:00 AM to 3:00 PM.

3. The method for evaluating the investment in distribution network planning and construction considering the uplink and downlink requirements of substations, as described in claim 1, is characterized in that: The prediction method in step A3 includes: Assume the maximum capacity main transformer in the substation generates In the event of a fault, the substation's grid load rate is calculated using the following formula: In the formula, Indicates the first m The grid load rate of the substation after the New Year This indicates the load growth rate of the substation during the period when distributed photovoltaic power is being generated. Indicates the load in the substation's power supply area. Indicates the energy storage capacity within the substation's power supply area. This represents the total capacity of a substation with N transformers. Indicates the first m Annual distributed photovoltaic power output simultaneous rate coefficient Indicates the first m Annual rated capacity of distributed photovoltaic inverters This indicates the maximum capacity of the main transformer within the substation; The calculation formula is: In the formula, This indicates the load growth rate of the substation during the period when distributed photovoltaic power is being generated. Indicates the substation number j Annual load growth rate j =0,1,2,3,4,5 This indicates that the substation has been the first in the past 5 years. j Annual load of substations during distributed photovoltaic power generation periods j =0,1,2,3,4,5 This indicates the load growth rate of the substation during the period when distributed photovoltaic power is being generated.

4. The method for evaluating the investment in distribution network planning and construction considering the uplink and downlink requirements of substations, as described in claim 3, is characterized in that: The analysis method in step A4 includes: set up At that time, the substation in the offline state could not meet the requirements of the first m The annual operation requirements of the power distribution network necessitate renovation and expansion. set up At that time, the substation in the online state could not meet the requirements of the first... m The annual operation requirements of the power distribution network necessitate renovation and expansion.

5. The method for evaluating the investment in distribution network planning and construction considering the uplink and downlink requirements of substations, as described in claim 4, is characterized in that: The analysis method in step A5 includes: Let the investment value for substation renovation and expansion be F. Calculate the annual distribution network investment value to meet the needs of substations in both offline and grid-connected states. The calculation formula is as follows: In the formula, This represents the annual grid investment value required to meet the needs of substations in the off-grid status. Indicates the first The old substations could not meet the requirements of the distribution network operation. This represents the annual investment value required to meet the grid connection requirements of substations. Indicates the first Substations that are not in service with the grid for the year cannot meet the requirements of the distribution network operation; Propose and calculate the investment evaluation indicators for power distribution networks. The calculation formula is: In the formula, This indicates that the substation was in the planning stage at the [number]th [year]. The initial investment value for the renovation and expansion in [year], Indicates the future planning stage of the substation The renovation and expansion were carried out in 2008. This represents the annual grid investment value required to meet the needs of substations in the off-grid status. This represents the annual investment value required to meet the grid connection requirements of substations.

6. The method for evaluating the investment in distribution network planning and construction considering the uplink and downlink requirements of substations, as described in claim 5, is characterized in that: The analytical method in step A5 further includes: The larger the value, the better the investment effect and efficiency of the power distribution network.

Images