Wiring loss reduction method and system containing distributed photovoltaic access

Abstract

The invention discloses a distribution loss reduction method and system containing distributed photovoltaic access. The wiring loss reduction method comprises the following steps: carrying out line loss theoretical calculation on a power distribution network operation scene after distributed photovoltaic access by adopting a power flow algorithm; the operation mode of a power grid is changed by adjusting the states of a section switch and an interconnection switch in a power distribution network, different operation modes are simulated, and the operation mode with the minimum line loss is selected as the optimal scheme; the problem of insufficient equipment capacity possibly caused by distributed photovoltaic access is evaluated, and a transformation scheme is provided for the situation that the line diameter of a feeder line section is insufficient; checking the condition that the power factor of the power distribution network transformer is low, improving the power factor of the power distribution network transformer by adopting a reactive compensation mode, and further reducing the active loss of the power distribution network; the three-phase unbalance condition in the power distribution network is analyzed, loads are reasonably distributed, and three-phase equipment with problems is necessarily adjusted or replaced so as to improve the three-phase balance degree.

Description

Technical Field

[0001] The present invention belongs to the technical field of power system wiring loss reduction, and specifically relates to a wiring loss reduction method and system including distributed photovoltaic access. Background Art

[0002] With the widespread application of distributed photovoltaics in distribution networks, their access has had a significant impact on the operation and loss of distribution networks. Traditional distribution network loss reduction methods have certain limitations when facing the situation of distributed photovoltaic access, and cannot effectively deal with the volatility and intermittency of photovoltaic power output and the resulting network flow changes and equipment operation problems.

[0003] Therefore, a wiring loss reduction technology for distributed photovoltaic access is needed to improve the operating efficiency and economy of the distribution network and improve the power supply quality. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the defects of the above-mentioned prior art and provide a distribution line loss reduction method and system including distributed photovoltaic access, aiming to solve the limitations of traditional distribution network loss reduction methods when dealing with distributed photovoltaic access, and to effectively reduce the line loss of the distribution network and improve the operation efficiency and power supply quality of the power grid by reasonably planning the access location and capacity of distributed photovoltaics.

[0005] To this end, the present invention adopts the following technical solution.

[0006] In a first aspect, the present invention provides a method for reducing wiring losses including distributed photovoltaic access, comprising:

[0007] Line loss theoretical calculation: The power flow algorithm is used to perform line loss theoretical calculation on the distribution network operation scenario after the distributed photovoltaic access;

[0008] Operation mode loss reduction: By adjusting the status of the section switches and tie switches in the distribution network, the operation mode of the power grid is changed, different operation modes are simulated, and the operation mode with the minimum line loss is selected as the optimal solution;

[0009] Equipment loss reduction: Evaluate the problem of insufficient equipment capacity that may be caused by distributed photovoltaic access, and propose transformation plans for the situation where the feeder line diameter is insufficient;

[0010] Reactive power compensation: Check if the power factor of the distribution network transformer is low, and use reactive power compensation to improve the power factor of the distribution network transformer, further reducing the active power loss of the distribution network;

[0011] Three-phase imbalance adjustment: Analyze the three-phase imbalance in the distribution network, distribute the load reasonably, and make necessary adjustments or replacements to the problematic three-phase equipment to improve the three-phase balance.

[0012] Furthermore, the specific steps of the line loss theoretical calculation include:

[0013] Establish the topological structure model of the distribution network, including the connection relationship of each node and line parameters;

[0014] Input the access location and capacity of distributed photovoltaic power sources;

[0015] Use software to perform power flow calculations to obtain the voltage, current, active power, and reactive power of each node;

[0016] Determine the specific value of line loss based on the power flow calculation results.

[0017] Furthermore, the software is used to perform power flow calculation to obtain the voltage, current, active power and reactive power of each node, specifically including:

[0018] Use the Newton-Raphson algorithm model; import the topology model, including the connection relationship and line parameters of each node; import the access location and capacity of the distributed photovoltaic power source; perform calculations based on the algorithm model; obtain the calculation results to obtain the voltage, current, active power and reactive power of each node.

[0019] Furthermore, the specific steps of reducing losses in the operation mode include:

[0020] Through the switching operation of the section switch and the tie switch, N different operation modes of the distribution network are obtained;

[0021] Carry out power flow calculation for line loss in each operation mode;

[0022] Select the operation mode with the minimum line loss as the optimal solution;

[0023] By adjusting the status of section switches and tie switches, the optimal operation mode can be achieved, thereby reducing grid losses.

[0024] Furthermore, the steps of power flow calculation include:

[0025] The voltage of each node and the branch flow are obtained through flow calculation;

[0026] Calculate the active power loss and reactive power loss of each line;

[0027] Calculate the copper and iron losses of each transformer;

[0028] Line loss = line loss + transformer loss;

[0029] Repeat the above steps to calculate the line losses of N different operating modes.

[0030] Furthermore, the specific steps of reducing the loss of the equipment include:

[0031] Check whether the access of distributed photovoltaics will lead to insufficient capacity of existing equipment;

[0032] Reconstruct the feeder line segment if the wire diameter is insufficient;

[0033] Calculate the line loss changes before and after the transformation to determine the necessity and economic feasibility of the transformation;

[0034] Propose specific transformation plans, including changing the conductor model and increasing the conductor cross-section.

[0035] Furthermore, the specific steps of the reactive power compensation include:

[0036] Measure and record the power factor of distribution network transformers;

[0037] If the power factor is lower than 0.95, a reactive power compensation device is used for compensation;

[0038] Through reactive power compensation, the power factor is improved, the transmission of reactive power is reduced, and thus the active power loss is reduced;

[0039] Regularly inspect and maintain the reactive power compensation device to ensure its normal operation.

[0040] Furthermore, the specific contents of the three-phase unbalance adjustment include:

[0041] Conduct detailed analysis of the load in the distribution network to understand the load characteristics of different regions and users, including power factor, power consumption period and load size; determine which regions or users have the greatest impact on the three-phase imbalance through the collection and analysis of load data;

[0042] Carry out a comprehensive inspection of the three-phase equipment in the distribution network to check whether the three-phase windings of the equipment are balanced and whether the operating parameters of the equipment are within the normal range; for equipment that is detected to have three-phase imbalance problems that cannot be solved by simple repairs, consider replacing it.

[0043] Furthermore, in the three-phase imbalance adjustment, for some users with flexible electricity usage time, the three-phase load is balanced by adjusting their electricity usage time; according to the topological structure and load distribution of the distribution network, part of the load is transferred from the phase with excessive current to other phases.

[0044] In a second aspect, the present invention provides a wiring loss reduction system including distributed photovoltaic access, which is used to implement the above wiring loss reduction method, and comprises:

[0045] Line loss theoretical calculation unit: uses power flow algorithm to perform line loss theoretical calculation on the distribution network operation scenario after distributed photovoltaic access;

[0046] Operation mode loss reduction unit: By adjusting the status of the section switches and tie switches in the distribution network, the operation mode of the power grid is changed, different operation modes are simulated, and the operation mode with the minimum line loss is selected as the optimal solution;

[0047] Equipment loss reduction unit: evaluates the problem of insufficient equipment capacity that may be caused by distributed photovoltaic access, and proposes transformation plans for the situation where the feeder line diameter is insufficient;

[0048] Reactive power compensation unit: Check if the power factor of the distribution network transformer is low, use reactive power compensation to improve the power factor of the distribution network transformer, and further reduce the active power loss of the distribution network;

[0049] Three-phase unbalance adjustment unit: Analyze the three-phase unbalance condition in the distribution network, distribute the load reasonably, and make necessary adjustments or replacements to the problematic three-phase equipment to improve the three-phase balance.

[0050] The beneficial effects of the present invention are as follows: the present invention can effectively reduce the line loss of the distribution network, improve the grid operation efficiency and power supply quality, and promote energy conservation and emission reduction by reasonably planning the distributed photovoltaic access location and the proportion of online power, combining power flow algorithm calculation, optimized operation mode, equipment transformation and reactive power compensation and other measures. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a flow chart of a wiring loss reduction method including distributed photovoltaic access according to the present invention;

[0052] Figure 2 It is a simplified model diagram of a distribution network not connected to a distributed power source in a specific implementation manner of the present invention;

[0053] Figure 3 It is a simplified model diagram of the distribution network connected to the distributed power source in a specific implementation manner of the present invention;

[0054] Figure 4 This is a structural diagram of a wiring loss reduction system with distributed photovoltaic access according to the present invention. DETAILED DESCRIPTION

[0055] 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.

[0056] This embodiment provides a wiring loss reduction method including distributed photovoltaic access, such as Figure 1 As shown, its content is as follows:

[0057] 1. Theoretical calculation of line loss: The power flow algorithm is used to perform theoretical calculation of line loss in typical operation scenarios of the distribution network after distributed photovoltaic access.

[0058] 1. Simplified model of distributed generation not connected to the grid

[0059] like Figure 2 The simplified model shown in the figure, L is the distance from the distributed generation to the load; P L is the active power consumed by the load in the system; Q L is the reactive power consumed by the load in the system; I L is the single-phase current passing through the load.

[0060] According to the above simplified model, the system load is: S L =P L +jQ L , the single-phase current flowing into the load is: U is the phase voltage on the line. The loss of the distribution network without access to distributed power sources is:

[0061]

[0062] r is the single-phase resistivity.

[0063] 2. Simplified model of distributed generation access to the grid

[0064] like Figure 3 The simplified model shown in the figure, L is the distance from the power source to the load; P L is the active power consumed by the load in the system; Q L is the reactive power consumed by the load in the system; I L is the single-phase current passing through the load; G is the distance between the distributed power source and the substation; I S is the single-phase output current of the substation; I G is the single-phase output current of the distributed power supply.

[0065] As can be seen from the above figure, The loss after the distribution network is connected to the distributed power source is divided into two parts. The first part is only powered by the substation, and the second part includes the power supply of both the substation and the distributed power source. The loss of the first part is:

[0066]

[0067] The second part of the loss is:

[0068]

[0069] The total system loss after connecting to the distributed power supply is:

[0070]

[0071] By comparing the network losses of model 1 (i.e., the simplified model of the distribution network without access to distributed power sources) and model 2 (i.e., the simplified model of the distribution network with access to distributed power sources), it can be concluded that the change in network loss after access to distributed power sources is:

[0072]

[0073] It can be seen from this that under a certain load, P ΔLoss The size of P is related to the location and capacity of the connected distributed power source. ΔLoss >0, the loss of the distribution network decreases; when P ΔLoss When <0, the loss of the distribution network increases.

[0074] The above theoretical analysis of the access of distributed power sources is based on the simplified distribution network model. However, the actual power grid is much more complicated than the simplified model. One distribution line is connected to multiple distributed power sources, and there are differences in the online time of each distributed power source. This leads to certain difficulties in calculating the network loss after the distributed power sources are connected to the power grid. The current flow algorithm can accurately calculate the network loss after the distributed power sources are connected to the power grid.

[0075] Through power flow calculation, the line loss changes before and after the distributed power supply is connected can be accurately evaluated, providing a theoretical basis for subsequent loss reduction measures. The specific steps include:

[0076] 11) Establish the topological structure model of the distribution network, including the connection relationship of each node and line parameters;

[0077] 12) Input the access location and capacity of distributed photovoltaic power sources;

[0078] 13) Use software to perform power flow calculations to obtain the voltage, current, active power and reactive power of each node; specifically, use the Newton-Raphson algorithm model; import the topology model, including the connection relationship and line parameters of each node; import the access location and capacity of the distributed photovoltaic power source; perform calculations according to the algorithm model; obtain the calculation results to obtain the voltage, current, active power and reactive power of each node;

[0079] 14) Determine the specific value of line loss based on the power flow calculation results.

[0080] 2. Reduce losses by operating mode: By adjusting the status of the section switches and tie switches in the distribution network, changing the operating mode of the power grid, simulating different operating modes, and selecting the operating mode with the smallest line loss as the optimal solution.

[0081] Specifically, the specific steps of reducing losses in the operation mode include:

[0082] Through the switching operation of the section switch and the tie switch, N different operation modes of the distribution network are obtained;

[0083] Carry out power flow calculation for line loss in each operation mode;

[0084] Select the operation mode with the minimum line loss as the optimal solution;

[0085] By adjusting the status of section switches and tie switches, the optimal operation mode can be achieved, thereby reducing grid losses.

[0086] More specifically, the steps of power flow calculation include:

[0087] The voltage of each node and the branch flow are obtained through flow calculation;

[0088] Calculate the active power loss and reactive power loss of each line;

[0089] Calculate the copper and iron losses of each transformer;

[0090] Line loss = line loss + transformer loss;

[0091] Repeat the above steps to calculate the line losses of N different operating modes.

[0092] 3. Equipment loss reduction: Evaluate the problem of insufficient equipment capacity that may be caused by distributed photovoltaic access, and propose transformation plans for the situation where the feeder line diameter is insufficient. For example, replace the wire model or increase the wire cross-sectional area to adapt to higher current requirements, thereby reducing line losses.

[0093] Specifically, the specific steps of reducing the loss of the equipment include:

[0094] Check whether the access of distributed photovoltaic power generation will lead to insufficient capacity of existing equipment, such as transformers and lines;

[0095] Reconstruct the feeder line segment if the wire diameter is insufficient;

[0096] Calculate the line loss changes before and after the transformation to determine the necessity and economic feasibility of the transformation;

[0097] Propose specific transformation plans, including changing the conductor model and increasing the conductor cross-section.

[0098] 4. Reactive power compensation: Check if the power factor of the distribution network transformer is low, and adopt reactive power compensation measures (such as installing capacitor banks) to improve the power factor of the distribution network transformer and further reduce the active power loss of the distribution network.

[0099] Assuming that the current flowing through the line is I, the voltage is U, the active power is P, the resistance is R, the power factor is cosφ, and the active loss is ΔP, the line loss is:

[0100]

[0101] Compensate the distribution network. Assume that after compensation, its power factor is increased from cosφ1 to cosφ2, and the line losses before and after compensation are ΔP1 and ΔP2 respectively. Then:

[0102]

[0103] To sum up, the active power loss ΔP of the line is inversely proportional to the square of cosφ. The higher cosφ is, the smaller ΔP is. In addition, since cosφ1 < cosφ2, then ΔP1 - ΔP2 < 0, and the loss of the distribution network decreases after reactive power compensation. After raising cosφ to the specified limit, calculate the active power loss of the line and analyze the loss reduction potential.

[0104] Specifically, the specific steps of the reactive power compensation include:

[0105] 41). Measure and record the power factor of the distribution network transformer.

[0106] 42). If the power factor is lower than 0.95, use a reactive power compensation device (such as a capacitor bank) for compensation.

[0107] 43). Through reactive power compensation, improve the power factor, reduce the transmission of reactive power, and thus reduce the active power loss.

[0108] 44). Regularly check and maintain the reactive power compensation device to ensure its normal operation.

[0109] V. Three-phase imbalance adjustment: Analyze the three-phase imbalance condition in the distribution network, reasonably distribute the load, and make necessary adjustments or replacements to the three-phase equipment with problems to improve the three-phase balance degree.

[0110] The specific content of the three-phase imbalance adjustment includes:

[0111] Conduct a detailed analysis of the load in the distribution network to understand the load characteristics of different regions and different users, including power factor, power consumption period, and load magnitude; through the collection and analysis of load data, determine which regions or users have a large impact on the three-phase imbalance degree; in the three-phase imbalance adjustment, for some users with flexible power consumption time, balance the three-phase load by adjusting their power consumption time; according to the topological structure and load distribution of the distribution network, transfer part of the load from the phase with excessive current to other phases;

[0112] Conduct a comprehensive inspection of the three-phase equipment in the distribution network to check whether the three-phase windings of the equipment are balanced and whether the operating parameters of the equipment are within the normal range; for the equipment detected with three-phase imbalance problems that cannot be solved by simple repair, consider replacement.

[0113] This embodiment also provides a wiring loss reduction system including distributed photovoltaic access, such as Figure 4 As shown, the method for implementing the above wiring loss reduction method includes:

[0114] Line loss theoretical calculation unit: uses power flow algorithm to perform line loss theoretical calculation on the distribution network operation scenario after distributed photovoltaic access;

[0115] Operation mode loss reduction unit: By adjusting the status of the section switches and tie switches in the distribution network, the operation mode of the power grid is changed, different operation modes are simulated, and the operation mode with the minimum line loss is selected as the optimal solution;

[0116] Equipment loss reduction unit: evaluates the problem of insufficient equipment capacity that may be caused by distributed photovoltaic access, and proposes transformation plans for the situation where the feeder line diameter is insufficient;

[0117] Reactive power compensation unit: Check if the power factor of the distribution network transformer is low, use reactive power compensation to improve the power factor of the distribution network transformer, and further reduce the active power loss of the distribution network;

[0118] Three-phase unbalance adjustment unit: Analyze the three-phase unbalance condition in the distribution network, distribute the load reasonably, and make necessary adjustments or replacements to the problematic three-phase equipment to improve the three-phase balance.

[0119] It should be noted that each unit in the above-mentioned wiring loss reduction system with distributed photovoltaic access can be fully or partially implemented by software, hardware and their combination. The above-mentioned units can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory of the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above-mentioned units. For the specific definition of a wiring loss reduction system with distributed photovoltaic access, please refer to the definition of a wiring loss reduction method with distributed photovoltaic access above. The two have the same functions and effects, which will not be repeated here.

[0120] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A wiring loss reduction method for distributed photovoltaic access, characterized in that: include: Line loss theoretical calculation: The power flow algorithm is used to perform line loss theoretical calculation on the distribution network operation scenario after distributed photovoltaic access; Operation mode loss reduction: By adjusting the status of the section switches and tie switches in the distribution network, the operation mode of the power grid is changed, different operation modes are simulated, and the operation mode with the minimum line loss is selected as the optimal solution; Equipment loss reduction: Evaluate the problem of insufficient equipment capacity that may be caused by distributed photovoltaic access, and propose transformation plans for the situation where the feeder line diameter is insufficient; Reactive power compensation: Check if the power factor of the distribution network transformer is low, and use reactive power compensation measures to improve the power factor of the distribution network transformer, and further reduce the active power loss of the distribution network; Three-phase imbalance adjustment: Analyze the three-phase imbalance in the distribution network, distribute the load reasonably, and make necessary adjustments or replacements to the problematic three-phase equipment to improve the three-phase balance.

2. A wiring loss reduction method for distributed photovoltaic access according to claim 1, characterized in that: The specific steps of the line loss theoretical calculation include: Establish the topological structure model of the distribution network, including the connection relationship of each node and line parameters; Input the access location and capacity of distributed photovoltaic power sources; Use software to perform power flow calculations to obtain the voltage, current, active power, and reactive power of each node; Determine the specific value of line loss based on the power flow calculation results.

3. A wiring loss reduction method for distributed photovoltaic access according to claim 2, characterized in that: The software is used to perform power flow calculation to obtain the voltage, current, active power and reactive power of each node, specifically including: Use the Newton-Raphson algorithm model; import the topology model, including the connection relationship and line parameters of each node; import the access location and capacity of the distributed photovoltaic power source; perform calculations based on the algorithm model; obtain the calculation results to obtain the voltage, current, active power and reactive power of each node.

4. A wiring loss reduction method for distributed photovoltaic access according to claim 1, characterized in that: The specific steps of reducing losses in the operation mode include: Through the switching operation of the section switch and the tie switch, N different operation modes of the distribution network are obtained; Carry out power flow calculation for line loss in each operation mode; Select the operation mode with the minimum line loss as the optimal solution; By adjusting the status of section switches and tie switches, the optimal operation mode can be achieved, thereby reducing grid losses.

5. A wiring loss reduction method for distributed photovoltaic access according to claim 4, characterized in that: The steps of power flow calculation include: The voltage of each node and the branch flow are obtained through flow calculation; Calculate the active power loss and reactive power loss of each line; Calculate the copper and iron losses of each transformer; Line loss = line loss + transformer loss; Repeat the above steps to calculate the line losses of N different operating modes.

6. A wiring loss reduction method for distributed photovoltaic access according to claim 1, characterized in that: The specific steps of reducing the loss of the equipment include: Check whether the access of distributed photovoltaics will lead to insufficient capacity of existing equipment; Reconstruct the feeder line segment if the wire diameter is insufficient; Calculate the line loss changes before and after the transformation to determine the necessity and economic feasibility of the transformation; Propose specific transformation plans, including changing the conductor model and increasing the conductor cross-section.

7. A wiring loss reduction method for distributed photovoltaic access according to claim 1, characterized in that: The specific steps of reactive power compensation include: Measure and record the power factor of distribution network transformers; If the power factor is lower than 0.95, a reactive power compensation device is used for compensation; Through reactive power compensation, the power factor is improved, the transmission of reactive power is reduced, and thus the active power loss is reduced; Regularly inspect and maintain the reactive power compensation device to ensure its normal operation.

8. A wiring loss reduction method for distributed photovoltaic access according to claim 1, characterized in that: The specific contents of the three-phase unbalance adjustment include: Conduct detailed analysis of the load in the distribution network to understand the load characteristics of different regions and users, including power factor, power consumption period and load size; determine which regions or users have the greatest impact on the three-phase imbalance through the collection and analysis of load data; Carry out a comprehensive inspection of the three-phase equipment in the distribution network to check whether the three-phase windings of the equipment are balanced and whether the operating parameters of the equipment are within the normal range; for equipment that is detected to have three-phase imbalance problems that cannot be solved by simple repairs, consider replacing it.

9. A wiring loss reduction method for distributed photovoltaic access according to claim 8, characterized in that: In the three-phase unbalanced adjustment, for some users with flexible electricity usage time, the three-phase load is balanced by adjusting their electricity usage time; according to the topological structure and load distribution of the distribution network, part of the load is transferred from the phase with excessive current to other phases.

10. A wiring loss reduction system with distributed photovoltaic access, used to implement the wiring loss reduction method according to any one of claims 1 to 9, characterized in that: include: Line loss theoretical calculation unit: uses power flow algorithm to perform line loss theoretical calculation on the distribution network operation scenario after distributed photovoltaic access; Operation mode loss reduction unit: By adjusting the status of the section switches and tie switches in the distribution network, the operation mode of the power grid is changed, different operation modes are simulated, and the operation mode with the minimum line loss is selected as the optimal solution; Equipment loss reduction unit: evaluates the problem of insufficient equipment capacity that may be caused by distributed photovoltaic access, and proposes transformation plans for the situation where the feeder line diameter is insufficient; Reactive power compensation unit: Check if the power factor of the distribution network transformer is low, use reactive power compensation to improve the power factor of the distribution network transformer, and further reduce the active power loss of the distribution network; Three-phase unbalance adjustment unit: Analyze the three-phase unbalance condition in the distribution network, distribute the load reasonably, and make necessary adjustments or replacements to the problematic three-phase equipment to improve the three-phase balance.

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