Optimal control method considering loss characteristics of key equipment of flexible interconnected distribution network

Abstract

The application discloses an optimization regulation method considering loss characteristics of key equipment of a flexible interconnected distribution network, which comprises the following steps: firstly, analyzing loss characteristics of SOP and transformers in the flexible interconnected distribution network; secondly, constructing a node loss sensitivity calculation model considering transformer loss based on branch loss and transformer loss; thirdly, calculating loss sensitivity of each node in the flexible interconnected distribution network by using the node loss sensitivity calculation model, and selecting a node with high sensitivity to access the SOP; fourthly, constructing a SOP capacity determination double-layer optimization model comprising an upper-layer optimization objective function and a lower-layer optimization objective function; fifthly, iteratively solving the SOP installation capacity value of the system in the case that the single-day comprehensive loss and the annual comprehensive cost are minimum by using a particle swarm algorithm; and finally, determining the initial conditions of the lower-layer optimization objective function in the SOP capacity determination double-layer optimization model based on the SOP site selection and capacity determination result, solving the lower-layer optimization objective function by using a Cplex commercial solver, and obtaining the output power of the SOP, so as to realize accurate regulation of power flow of the distribution network.

Description

Technical Field

[0001] This invention relates to the field of power grid technology, and in particular to an optimized control method that takes into account the loss characteristics of key equipment in flexible interconnected distribution networks. Background Technology

[0002] With the high proportion of distributed generation connected to the grid, power flow control in distribution networks has become more complex. Currently, distribution networks mainly change network topology by adjusting switch states to achieve load transfer and network loss optimization. However, traditional distribution network interconnection measures based on mechanical switches cannot maximize system economy and reliability due to limited response speed and control accuracy. Soft open points (SOPs), as fully controlled power electronic devices, can replace traditional mechanical switches to further improve the ability to optimize distribution network losses and achieve economic operation, thanks to their continuous power controllability and flexible control methods. However, the installation location and capacity selection of SOPs are closely related to their investment economic benefits, and the design of their control strategies directly affects the operational performance of flexible interconnected distribution networks. Therefore, realizing SOP planning and configuration and formulating reasonable optimization control strategies are crucial for reducing distribution network losses and achieving economic operation.

[0003] Regarding SOP planning and configuration, the method of connecting SOPs at the original tie switch location is prone to overlooking the optimal connection position, and the method of establishing a site selection model with the SOP connection position as the decision variable is relatively cumbersome in calculation. SOP capacity determination mainly involves its cost, so most studies use cost as the measurement standard to establish a comprehensive system cost optimization model, and link it with the system operation optimization model to form a two-level optimization model for SOP capacity determination. However, the lower-level operation optimization model rarely considers the loss characteristics of key equipment in the system, and the capacity determination results need to be further refined.

[0004] Regarding SOP (Standard Operating Procedure) optimization and control strategies, research on the economic operation of flexible interconnected distribution networks has not systematically considered the loss characteristics of key equipment such as transformers and interconnection devices, resulting in poor application effects of existing research. However, in reality, transformer and SOP losses account for a large proportion (50-80%) of the entire flexible interconnected distribution network. Considering their loss optimization and maintaining economic operation is crucial for improving the overall economic efficiency of the flexible interconnected distribution network. Therefore, existing optimization and control strategies for flexible interconnected distribution networks urgently need further improvement in enhancing system economics. Summary of the Invention

[0005] To address the problem that traditional optimization and control strategies for flexible interconnected distribution networks lack consideration for the loss characteristics of key equipment, resulting in poor operational optimization effects, this invention provides an optimization and control method that takes into account the loss characteristics of key equipment in flexible interconnected distribution networks.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical method: an optimized control method considering the loss characteristics of key equipment in flexible interconnected distribution networks, comprising:

[0007] Step S1: Collect multiple sets of parameters during normal operation of the flexible interconnected distribution network. Based on the parameters, analyze the loss characteristics of SOP and transformer in the flexible interconnected distribution network, and fit the characteristic functions of SOP transmission power and power transmission efficiency as well as the characteristic function of transformer operating efficiency.

[0008] Step S2: Construct a node loss sensitivity calculation model that takes into account transformer losses based on branch losses and transformer losses;

[0009] Step S3: Calculate the loss sensitivity of each node in the flexible interconnected distribution network using the node loss sensitivity calculation model constructed in step S2, select nodes with high sensitivity to connect to the SOP, and obtain the SOP location result.

[0010] Step S4: Construct a two-layer optimization model for SOP (System-on-Place) with fixed capacity, including an upper-layer optimization objective function and a lower-layer optimization objective function. The upper-layer optimization objective function uses the SOP installation capacity as the decision variable and aims to minimize the system's annual comprehensive cost, which includes the system's annual comprehensive loss cost. The lower-layer optimization objective function uses the SOP transmission power as the decision variable and aims to reduce the system's daily comprehensive loss. The output power of the SOP is not greater than the SOP installation capacity.

[0011] Step S5: Input the initialized SOP installation capacity and output power into the SOP calibrated dual-layer optimization model, and use the particle swarm algorithm to iteratively solve the SOP installation capacity value under the condition of minimizing the daily comprehensive loss and annual comprehensive cost, and obtain the SOP calibrated result.

[0012] Step S6: Based on the SOP location results from step S3 and the SOP capacity determination results from step S5, determine the initial conditions of the lower-level optimization objective function in the SOP capacity determination two-level optimization model. Use the Cplex commercial solver to solve the lower-level optimization objective function to obtain the output power of the SOP, thereby achieving precise control of the power flow of the distribution network.

[0013] Furthermore, in step S1, the characteristic functions of SOP transmission power and power transmission efficiency, as well as the characteristic function of transformer operating efficiency, are obtained by fitting as follows:

[0014] η s =1.966S 5 -6.616S 4 +8.633S 3 -5.439S 2 +1.546S+99.19 (1)

[0015] In the formula, η s SOP power transmission efficiency, where S is the per-unit value of SOP transmission power;

[0016]

[0017] In the formula, η b β is the transformer power transmission efficiency, β is the transformer load factor, and S r For transformer capacity, For the transformer power factor, ΔP 0Z For transformer no-load loss, ΔP KZ U represents the rated load power loss of the transformer. * This is the per-unit value of the transformer's operating voltage.

[0018] Furthermore, step S2, when constructing a nodal loss sensitivity calculation model that takes into account transformer losses based on branch losses and transformer losses, includes the following steps:

[0019] S201, determine the branch loss sensitivity calculation formula from node i to j as shown in equation (3), and take the partial derivatives of the branch loss with respect to the active power and reactive power of the line as shown in equation (4):

[0020]

[0021]

[0022] In the formula, P ij_loss,t For branch losses, P ij,t Q ij,t V i,t Let r be the network active power, reactive power, and voltage of upstream node i after the node power changes, respectively. ij Let ΔP be the branch resistance. ij_loss,t ΔP represents the change in line loss under different load conditions. j ΔQ j These represent the changes in active power and reactive power at node j, respectively.

[0023] S202, determine the formula for calculating transformer loss sensitivity as follows (5), and take the partial derivatives of transformer loss with respect to transformer active power and reactive power as follows (6):

[0024]

[0025]

[0026] In the formula, P b_loss,t For transformer losses, P oz For transformer no-load loss, Pkz P represents the rated load power loss of the transformer. b,t Q b,t These represent the active and reactive power of the transformer after the power change at the root node, S. r For the transformer output power, ΔP b_loss,t V represents the change in transformer losses under different load conditions. n,t Let ΔP be the root node voltage. n ΔQ n These are the changes in active power and reactive power at the root node n, respectively.

[0027] S203, compare equation (4) with equation (6) to determine the equivalent resistance of the transformer as shown in equation (7). Considering the influence of load conditions at different times on the loss sensitivity calculation, assume that load data for a total of T time periods are taken, and uniformly consider the node loss sensitivity calculation model of transformer loss as shown in equation (8).

[0028]

[0029]

[0030] Furthermore, in step S4, the upper-level optimization objective function of the SOP fixed-capacity two-layer optimization model is established with the SOP installation capacity as the decision variable and the minimum annual comprehensive system cost as the optimization objective, as follows:

[0031] min C=(C1+C2+C3) (9)

[0032]

[0033] In the formula, C represents the annual comprehensive cost of the system, C1, C2, and C3 represent the annual fixed investment cost of the SOP, the annual operation and maintenance cost of the SOP, and the annual loss cost of the power distribution system, respectively, d is the discount rate, y is the economic useful life of the SOP, and c sop SOP unit capacity investment cost, S sop Where SOP is the installation capacity, ε is the annual operation and maintenance cost coefficient, and c is the standard operating procedure (SOP) capacity. g F represents the grid electricity price, and F represents the system's daily comprehensive loss.

[0034] Furthermore, in step S4, using SOP transmission power as the decision variable and reducing the system's daily comprehensive loss as the optimization objective, the lower-level optimization objective function of the SOP fixed-capacity two-level optimization model is established as follows:

[0035] min F=(F1+F2+F3) (11)

[0036]

[0037] In the formula, F represents the system's daily comprehensive loss, F1 represents the SOP power transmission loss, F2 represents the transformer loss, F3 represents the network line loss, and S... sy η represents the transmission power of the y-th port of the SOP. sy P represents the power transfer efficiency of port y at this time. bz_loss I represents the loss of the z-th transformer. ij r represents the line current from node i to j. ij This represents the resistance of branch ij.

[0038] Preferably, in step S4, when establishing the lower-level optimization objective function of the SOP-based two-layer optimization model, the constraints of the lower-level optimization objective function are also set as follows:

[0039] 1) SOP constraints, including SOP port power balance constraints and SOP capacity constraints;

[0040]

[0041] In the formula, P s1 P s2 P s3 These represent the active power of ports 1, 2, and 3 of the SOP, respectively;

[0042] 2) Transformer constraints, including the optimal economic operating range constraint and the transformer capacity constraint;

[0043]

[0044] In the formula, β z Let S be the load factor of the z-th transformer. bz Let P be the output power of the z-th transformer. bz Let Q be the active power of the z-th transformer. bz Let S be the reactive power of the z-th transformer. rz Let be the capacity of the z-th transformer;

[0045] 3) Distribution network constraints, including network operation security constraints and network power flow constraints.

[0046] Among them, the network operation security constraints are:

[0047]

[0048] In the formula, N is the number of nodes, and V i Let V be the voltage at node i. j Let V be the voltage at node j. i_min V is the lower limit of the voltage at node i. i_max s is the upper limit of the voltage at node i. i Let s be the injected power at node i.i_min s is the lower limit of node transmission power. i_max I is the lower limit of node transmission power. ij Let I be the line current from node i to j. ij_max This represents the upper limit of the line current.

[0049] Furthermore, since the network power flow constraint is non-convex, a two-step relaxation is performed to improve the solution rate, allowing... The final network flow constraint is:

[0050]

[0051] In the formula, p j The injected active power q for node j j For the injected reactive power at node j, P jk P represents the active power of the line from node j to k. ij Let Q be the active power of the line from node i to j. jk Let Q be the reactive power of the line from node j to k. ij Let x be the reactive power of the line from node i to j. ij For the ij branch reactance.

[0052] Further, in step S5, the SOP installation capacity and output power are first initialized, and the initialization data and system-related parameters are input into the SOP fixed capacity dual-layer optimization model. Then, the particle swarm algorithm is used to iteratively solve equations (9)-(16) of the SOP fixed capacity dual-layer optimization model to obtain the SOP installation capacity value under the condition of minimizing the daily comprehensive loss and annual comprehensive cost, which is the SOP fixed capacity result.

[0053] Preferably, in step S6, based on the SOP location result in step S3 and the SOP capacity determination result in step S5, the initial conditions of the lower-level optimization objective function in the SOP capacity determination two-layer optimization model are determined. Then, the Cplex commercial solver is used to solve equations (11)-(16) of the lower-level optimization objective function to obtain the output power of the SOP, and then the active power and reactive power transmitted by the SOP are obtained, thereby realizing the precise control of the power flow of the distribution network.

[0054] The present invention provides an optimized control method for key equipment loss characteristics in flexible interconnected distribution networks. Taking into account the loss characteristics of the System Operation Point (SOP), it accurately calculates the SOP loss. Simultaneously, based on the transformer loss characteristics, it optimizes the transformer loss, which accounts for the largest proportion, significantly reducing the overall system loss and thus enabling precise control of network power flow. This method not only effectively solves the problem of light and heavy loads in interconnected systems but also greatly improves the reliability and economy of interconnected system operation, which is of great significance to the optimized development of flexible interconnected distribution networks. Attached Figure Description

[0055] Figure 1 This is a flowchart of the optimized control method for the loss characteristics of key equipment in flexible interconnected distribution networks involved in this invention;

[0056] Figure 2 This is a schematic diagram of a flexible interconnected distribution network based on a three-port SOP in this embodiment;

[0057] Figure 3 This is a graph showing the SOP transmission power versus power transmission efficiency in this embodiment.

[0058] Figure 4 This is a graph showing the relationship between transformer load rate and power transmission efficiency in this embodiment.

[0059] Figure 5 This is a schematic diagram of the distribution network loss sensitivity analysis in this embodiment;

[0060] Figure 6 This is a schematic diagram of the distribution network line loss calculation and analysis in this embodiment;

[0061] Figure 7 This is a schematic diagram of the interconnection between the IEEE 15 system and the IEEE 22 system in this embodiment;

[0062] Figure 8 This is a comparison chart of the overall system loss at different access locations of the SOP in this embodiment;

[0063] Figure 9 This is a comparison chart of the overall system losses under different scenarios in this embodiment;

[0064] Figure 10 This is a comparison chart of transformer load rates under different scenarios in this embodiment. Detailed Implementation

[0065] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments and accompanying drawings. The content mentioned in the embodiments is not intended to limit the present invention.

[0066] An optimized control method considering the loss characteristics of key equipment in a flexible interconnected distribution network includes the following steps.

[0067] Step S1: Loss Characteristics Analysis of Key Equipment in Flexible Interconnected Distribution Networks

[0068] This invention takes a flexible interconnected distribution network based on a three-port standard operating procedure (SOP) as an example to analyze the loss characteristics of the SOP and the transformer, such as... Figure 2 As shown in the diagram. In the diagram: DN1 and DN2 represent medium-voltage distribution networks in different areas; T1 and T2 are distribution transformers; P bz Q bz(z = 1, 2) represent the active power and reactive power output by the transformer, respectively; P sy Q sy (y = 1, 2, 3) represent the active and reactive power transmitted by SOP, respectively.

[0069] S101, SOP Loss Characteristic Analysis. Multiple sets of parameters were collected during normal operation of the flexible interconnected distribution network. Based on parameter fitting, the characteristic functions of SOP transmission power and power transmission efficiency were obtained.

[0070] η s =1.966S 5 -6.616S 4 +8.633S 3 -5.439S 2 +1.546S+99.19 (1)

[0071] In the formula, η s Let S be the SOP power transmission efficiency, and S be the per-unit value of the SOP transmission power; according to equation (1), the relationship between SOP transmission power and power transmission efficiency is as follows: Figure 3 As shown in the figure, the SOP power transmission efficiency varies with the amount of power transmitted through the port.

[0072] S102, Transformer Loss Characteristic Analysis. Based on the previously collected multiple sets of parameters, a characteristic function for the transformer's operating efficiency is fitted.

[0073]

[0074] In the formula, η b β is the transformer power transmission efficiency, β is the transformer load factor, and S r For transformer capacity, For the transformer power factor, ΔP 0Z For transformer no-load loss, ΔP KZ U represents the rated load power loss of the transformer. * Let be the per-unit value of the transformer operating voltage. According to equation (2), the relationship between transformer load factor and power transmission efficiency is as follows: Figure 4 As shown in the figure, the transformer power transmission efficiency curve is a convex function. Both excessively high and low load rates will lead to low transformer power transmission efficiency.

[0075] Step S2: Construct a node loss sensitivity calculation model that takes into account transformer losses based on branch losses and transformer losses.

[0076] S201, such as Figure 5 As shown in the figure, this embodiment constructs a schematic diagram of distribution network loss sensitivity analysis. Taking branch ij in the figure as an example, the branch loss sensitivity calculation formula is as follows (3):

[0077]

[0078] Based on equation (3) above, the branch losses are partially derived with respect to the active power and reactive power of the line, as shown in equation (4) below:

[0079]

[0080] In the formula, P ij_loss,t For branch losses, P ij,t Q ij,t V i,t Let r be the network active power, reactive power, and voltage of upstream node i after the node power changes, respectively. ij Let ΔP be the branch resistance. ij_loss,t ΔP represents the change in line loss under different load conditions. j ΔQ j Let be the changes in active power and reactive power at node j, respectively. Equation (4) represents the power change ΔP at node j. j ΔQ j The loss sensitivity of node j at that time.

[0081] S202, Based on the transformer loss, the formula for calculating the root node loss sensitivity is determined as shown in equation (5) below:

[0082]

[0083] Based on equation (5) above, the partial derivatives of the transformer losses with respect to the transformer's active power and reactive power are shown in equation (6) below:

[0084]

[0085] In the formula, P b_loss,t For transformer losses, P oz For transformer no-load loss, P kz P represents the rated load power loss of the transformer. b,t Q b,t These represent the active and reactive power of the transformer after the power change at the root node, S. r For the transformer output power, ΔP b_loss,t V represents the change in transformer losses under different load conditions. n,t Let ΔP be the root node voltage. n ΔQ n These represent the changes in active power and reactive power at the root node n, respectively. Equation (6) represents the power change ΔP at the root node. n ΔQ n The loss sensitivity of the root node at that time.

[0086] S203, derive the equivalent resistance of the transformer and unify the sensitivity calculation model. Comparing equation (4) and equation (6), the equivalent resistance of the transformer can be expressed as:

[0087]

[0088] Considering the impact of load conditions at different times on loss sensitivity calculation, assuming that load data for a total of T time periods are taken, a nodal loss sensitivity calculation model that uniformly considers transformer losses is used, as shown in equation (8).

[0089]

[0090] Step S3: Determine the SOP location results. Using the node loss sensitivity calculation model constructed in step S2, calculate the loss sensitivity of each node in the flexible interconnected distribution network, and select nodes with high sensitivity, i.e., nodes with strong SOP power flow control capabilities, for connection.

[0091] Step S4: Construct a two-layer optimization model for SOP sizing, which includes an upper-layer optimization objective function and a lower-layer optimization objective function.

[0092] S401, this invention establishes the upper-level optimization objective function of a two-layer optimization model for SOP fixed-capacity, using SOP installation capacity as the decision variable and minimizing the system's annual comprehensive cost as the optimization objective, as follows:

[0093] min C=(C1+C2+C3) (9)

[0094] In the formula, C represents the system's annual comprehensive cost, and C1, C2, and C3 represent the annual fixed investment cost of SOP, the annual operation and maintenance cost of SOP, and the annual loss cost of the power distribution system, respectively. The calculation formulas for C1, C2, and C3 are as follows:

[0095]

[0096] In the formula, d is the discount rate, y is the economic useful life of the SOP, and c sop SOP unit capacity investment cost, S sop Where SOP is the installation capacity, ε is the annual operation and maintenance cost coefficient, and c is the standard operating procedure (SOP) capacity. g F represents the grid electricity price, and F represents the system's daily comprehensive loss.

[0097] S402, this invention establishes the lower-level optimization objective function of the SOP fixed-capacity two-layer optimization model with SOP transmission power as the decision variable and reducing the system's daily comprehensive loss as the optimization objective, as follows:

[0098] min F=(F1+F2+F3) (11)

[0099] In the formula, F represents the system's daily comprehensive loss, F1 represents the SOP power transmission loss, F2 represents the transformer loss, and F3 represents the network line loss. The calculation formulas for F1, F2, and F3 are as follows:

[0100]

[0101] In the formula, F represents the system's daily comprehensive loss, F1 represents the SOP power transmission loss, F2 represents the transformer loss, F3 represents the network line loss, and S... sy η represents the transmission power of the y-th port of the SOP. sy P represents the power transfer efficiency of port y at this time. bz_loss I represents the loss of the z-th transformer. ij r represents the line current from node i to j. ij This represents the resistance of branch ij. The schematic diagram for calculating and analyzing line losses in the distribution network is shown below. Figure 6 As shown.

[0102] S403 sets the constraints for the lower-level optimization objective function as follows.

[0103] 1) SOP constraints, including SOP port power balance constraints and SOP capacity constraints.

[0104]

[0105] In the formula, P s1 P s2 P s3 These represent the active power of ports 1, 2, and 3 of the SOP, respectively.

[0106] 2) Transformer constraints, including the optimal economic operating range constraint and the transformer capacity constraint.

[0107]

[0108] In the formula, β z Let S be the load factor of the z-th transformer. bz Let P be the output power of the z-th transformer. bz Let Q be the active power of the z-th transformer. bz Let S be the reactive power of the z-th transformer. rz Let be the capacity of the z-th transformer.

[0109] 3) Distribution network constraints, including network operation security constraints and network power flow constraints.

[0110] Among them, the network operation security constraints are:

[0111]

[0112] In the formula, N is the number of nodes, and V i Let V be the voltage at node i. j Let V be the voltage at node j. i_min V is the lower limit of the voltage at node i. i_max s is the upper limit of the voltage at node i. i Let s be the injected power at node i. i_min s is the lower limit of node transmission power. i_max I is the lower limit of node transmission power. ij Let I be the line current from node i to j. ij_max This represents the upper limit of the line current.

[0113] Furthermore, since the network power flow constraint is non-convex, a two-step relaxation is performed to improve the solution rate, allowing... The final network flow constraint is:

[0114]

[0115] In the formula, p j The injected active power q for node j j For the injected reactive power at node j, P jk P represents the active power of the line from node j to k. ij Let Q be the active power of the line from node i to j. jk Let Q be the reactive power of the line from node j to k. ij Let x be the reactive power of the line from node i to j. ij For the ij branch reactance.

[0116] Step S5: Determine the SOP capacity determination result. Initialize the SOP installation capacity and output power, input the initial data and relevant system parameters into the SOP capacity determination bilayer optimization model, and use the particle swarm optimization algorithm to iteratively solve equations (9)-(16) of the SOP capacity determination bilayer optimization model to obtain the SOP installation capacity value under the condition of minimizing the daily comprehensive loss and annual comprehensive cost, i.e., the SOP capacity determination result.

[0117] Step S6: Determine the optimization and control strategy for the flexible interconnected distribution network. Based on the SOP location results in Step S3 and the SOP capacity determination results in Step S5, determine the initial conditions of the lower-level optimization objective function in the SOP capacity determination two-layer optimization model. Use the Cplex commercial solver to solve equations (11)-(16) of the lower-level optimization objective function to obtain the output power of the SOP, and then obtain the active power and reactive power transmitted by the SOP, thereby realizing precise control of the power flow of the distribution network.

[0118] To verify the effectiveness and superiority of the method involved in this invention, such as... Figure 7As shown, this embodiment takes the IEEE 15 and IEEE 22 flexible interconnected distribution network system as an example. Based on the method described in this invention, SOP location and capacity determination, as well as precise power flow control of the distribution network, are performed. The system parameters of the flexible interconnected distribution network example are shown in Table 1 below:

[0119] Table 1. Parameter Settings for the Case Study

[0120]

[0121]

[0122] 1. Verification of SOP planning and configuration results

[0123] (1) Verification of SOP location results

[0124] To verify the effectiveness of SOP location selection based on loss sensitivity in this paper, three schemes were set up for comparison. The scheme allocation is shown in Table 2. The connection diagram of the embodiment of this invention is shown in the figure. Figure 7 As shown, both verification schemes 1 and 2 involve selecting the node with the second highest loss sensitivity for access.

[0125] Table 2. Sensitivity Location Model Verification Scheme

[0126]

[0127] The results of the loss comparison of the three schemes are as follows: Figure 8 As shown, by Figure 8 It can be seen that when the SOP access location is matched with the lowest loss sensitivity values ​​in the two subsystems (Verification Scheme 2), the overall loss of the system is the highest within 24 hours. Secondly, although there were instances where Verification Scheme 1 was lower than the scheme of this invention within the 0-8 hour time period, the total loss calculation within 24 hours shows that the loss of the scheme of this invention is 2.3% lower than that of Verification Scheme 1. The loss comparison results of the three schemes show that the scheme of this invention has the best loss reduction effect, verifying the correctness of the node loss sensitivity calculation model of this invention and the effectiveness of selecting the SOP access location accordingly.

[0128] (2) Verification of SOP volume determination results

[0129] This implementation presents two scenarios for comparison to verify the effectiveness of the SOP (Single-Plank) capacity-fixed dual-layer optimization model of this invention. Scenario 1: Without considering transformer loss optimization, the SOP power transmission efficiency is fixed; Scenario 2: Considering transformer loss optimization, a time-varying SOP power transmission efficiency curve is used, which is the capacity-fixed scheme of this invention. The capacity-fixed results for the two scenarios are obtained by iteratively solving using the particle swarm optimization algorithm. The corresponding annual comprehensive system cost and annual comprehensive system loss are shown in Table 3.

[0130] Table 3 Comparison of Volume Fixation Results

[0131] Scene Volumetric Result / MW Annual comprehensive cost / 10,000 yuan Daily comprehensive loss / kW 1 0.22，0.25，0.60 23.96 656.9 2 0.32，0.23，0.29 21.22 647.6

[0132] According to the comparison results in Table 3, the annual comprehensive cost of the proposed solution is 11.4% lower than that of Scenario 1, and the daily comprehensive system loss is 1.4% lower. Therefore, in the SOP constant capacity two-layer optimization model involved in this invention, the comprehensive system loss optimization part considers transformer loss optimization and adopts time-varying SOP power transmission efficiency curves, which can effectively reduce system losses and reduce the comprehensive system cost.

[0133] 2. Analysis of Optimization Results

[0134] This implementation method sets up three scenarios for comparative analysis. The scenarios are as follows:

[0135] Scenario 1: The IEEE22 and IEEE15 subsystems are not interconnected by SOP. In this case, only the power flow of the two systems needs to be calculated separately to obtain the system's daily comprehensive loss over 24 hours, which serves as a blank control group.

[0136] Scenario 2: The IEEE22 and IEEE15 subsystems are interconnected via SOP, but the optimization model does not consider the optimal economic operating range of the transformer and the SOP power transmission efficiency curve, which is the traditional control strategy.

[0137] Scenario 3: The IEEE22 and IEEE15 systems are interconnected via SOP, and the optimization model takes into account the loss characteristics of the transformer and SOP, which is the optimization control strategy of this invention.

[0138] Figure 9 The comparison results of the system's daily comprehensive loss under three scenarios are shown. It can be seen that the traditional control strategy is not significantly effective in reducing system loss, with the largest reduction occurring within the first 13 hours, at only 9.03%. In contrast, the control strategy of this invention effectively reduces system loss, with an average reduction of 25.79% over 24 hours, and the largest reduction occurring within the first 13 hours, reaching 28.82%. This demonstrates that, compared to traditional control strategies, the proposed control strategy can significantly reduce the system's comprehensive loss.

[0139] Figure 10 The diagram illustrates the variation of the load rate of two transformers in a transformer interconnection system over time under different scenarios. Figure 10 (a) shows the change in the load factor of transformer T1 over time under residential load with large load fluctuations. Figure 10(b) shows the change of the load rate of transformer T2 over time under a relatively stable industrial load. Comparing the two figures, it can be seen that whether it is a residential load with large load fluctuations or an industrial load with relatively stable load, the control strategy of the present invention can effectively maintain the transformer operating within the optimal economic operating range, avoid the transformer operating under light or heavy loads, reduce the overall system loss, and improve the system operation stability.

[0140] The above embodiments are preferred implementations of the present invention. In addition, the present invention can be implemented in other ways. Any obvious substitutions without departing from the concept of the present technical solution are within the protection scope of the present invention.

[0141] To facilitate understanding by those skilled in the art of the improvements of this invention over the prior art, some of the accompanying drawings and descriptions have been simplified, and for clarity, some other elements have been omitted from this application. Those skilled in the art should realize that these omitted elements may also constitute the content of this invention.

Claims

1. An optimized control method considering the loss characteristics of key equipment in flexible interconnected distribution networks, characterized in that, include: Step S1: Collect multiple sets of parameters during normal operation of the flexible interconnected distribution network. Based on the parameters, analyze the loss characteristics of SOP and transformer in the flexible interconnected distribution network, and fit the characteristic functions of SOP transmission power and power transmission efficiency as well as the characteristic function of transformer operating efficiency. Step S2: Construct a node loss sensitivity calculation model that takes into account transformer losses based on branch losses and transformer losses; S201, Determine the node arrive The formula for calculating the branch loss sensitivity is as follows (3). Taking the partial derivatives of the branch loss with respect to the active power and reactive power of the line, respectively, is as follows (4): (3) (4) In the formula, For branch losses, These represent the network active power, reactive power, and upstream node power corresponding to the changes in node power. voltage, For branch resistance, This represents the change in line loss under different load conditions; They are nodes The changes in active power and reactive power; S202, determine the formula for calculating transformer loss sensitivity as follows (5), and take the partial derivatives of transformer loss with respect to transformer active power and reactive power as follows (6): (5) (6) In the formula, For transformer losses, For transformer no-load loss, This refers to the rated load power loss of the transformer. These represent the active and reactive power of the transformer after the power change at the root node, respectively. For the capacity of the transformer, This represents the variation in transformer losses under different load conditions. The root node voltage, These are the changes in active power and reactive power at the root node n, respectively. S203, compare equation (4) with equation (6) to determine the equivalent resistance of the transformer as shown in equation (7). Consider the influence of load conditions at different times on the loss sensitivity calculation. Assume that the load data of T time periods are taken together, and a node loss sensitivity calculation model that takes into account the transformer loss is used as shown in equation (8). (7) (8) Step S3: Calculate the loss sensitivity of each node in the flexible interconnected distribution network using the node loss sensitivity calculation model constructed in step S2, select nodes with high sensitivity to connect to the SOP, and obtain the SOP location result. Step S4: Construct a two-layer optimization model for SOP sizing, which includes an upper-layer optimization objective function and a lower-layer optimization objective function; The upper-level optimization objective function uses the SOP installation capacity as the decision variable and aims to minimize the system's annual comprehensive cost, which includes the system's annual comprehensive loss cost. The lower-level optimization objective function uses the SOP transmission power as the decision variable and aims to reduce the system's daily comprehensive loss. The output power of the SOP is not greater than the SOP installation capacity. Step S5: Input the initialized SOP installation capacity and output power into the SOP calibrated dual-layer optimization model, and use the particle swarm algorithm to iteratively solve the SOP installation capacity value under the condition of minimizing the daily comprehensive loss and annual comprehensive cost, and obtain the SOP calibrated result. Step S6: Based on the SOP location results from step S3 and the SOP capacity determination results from step S5, determine the initial conditions of the lower-level optimization objective function in the SOP capacity determination two-level optimization model. Use the Cplex commercial solver to solve the lower-level optimization objective function to obtain the output power of the SOP, thereby achieving precise control of the power flow of the distribution network.

2. The optimized control method for considering the loss characteristics of key equipment in flexible interconnected distribution networks according to claim 1, characterized in that: In step S1, the characteristic functions of SOP transmission power and power transmission efficiency, as well as the characteristic function of transformer operating efficiency, are obtained by fitting as follows: (1) In the formula, For SOP power transfer efficiency, S This refers to the per-unit power output of the Standard Opening (SOP). (2) In the formula, For transformer power transmission efficiency, For transformer load rate, For transformer capacity, For transformer power factor, For transformer no-load loss, This refers to the rated load power loss of the transformer. This is the per-unit value of the transformer's operating voltage.

3. The optimized control method for considering the loss characteristics of key equipment in flexible interconnected distribution networks according to claim 2, characterized in that: In step S4, the upper-level optimization objective function of the SOP fixed-capacity two-layer optimization model is established with the SOP installation capacity as the decision variable and the minimum annual comprehensive system cost as the optimization objective, as follows: (9) (10) In the formula, C The total annual cost of the system, C 1. C 2. C 3 represents the annual fixed investment cost of SOP, the annual operation and maintenance cost of SOP, and the annual loss cost of the power distribution system, respectively. d For the discount rate, y The economic service life of SOP. c sop The unit capacity investment cost of SOP, S sop For SOP installation capacity, ε This is the annual operation and maintenance cost coefficient. c g For grid electricity price, F This represents the system's total daily loss.

4. The optimized control method for considering the loss characteristics of key equipment in flexible interconnected distribution networks according to claim 3, characterized in that: In step S4, the lower-level optimization objective function of the SOP fixed-capacity two-layer optimization model is established with SOP transmission power as the decision variable and reducing the system's daily comprehensive loss as the optimization objective, as follows: (11) (12) In the formula, F The total daily loss of the system, F 1 indicates SOP power transmission loss. F 2 indicates transformer loss. F 3 indicates network line loss. S sy Indicates the SOP number y The transmission power of each port, Indicates at this time y Port power transfer efficiency, P bz_loss This represents the loss of the z-th transformer. Represents a node arrive The line current, express Branch resistance.

5. The optimized control method for considering the loss characteristics of key equipment in flexible interconnected distribution networks according to claim 4, characterized in that: In step S4, when establishing the lower-level optimization objective function of the SOP-based two-layer optimization model, the constraints of the lower-level optimization objective function are also set as follows: 1) SOP constraints, including SOP port power balance constraints and SOP capacity constraints; (13) In the formula, P s1 , P s2 , P s3 These represent the active power of ports 1, 2, and 3 of the SOP, respectively; 2) Transformer constraints, including the optimal economic operating range constraint and the transformer capacity constraint; (14) In the formula, Let z be the load factor of the z-th transformer. S bz Let z be the output power of the z-th transformer. P bz Let z be the active power of the z-th transformer. Q bz Let z be the reactive power of the z-th transformer. S rz Let be the capacity of the z-th transformer; 3) Distribution network constraints, including network operation security constraints and network power flow constraints; Among them, the network operation security constraints are: (15) In the formula, N For the number of nodes, For nodes voltage, For nodes voltage, For nodes The lower limit of voltage, For nodes The upper limit of voltage, For nodes Injection power, This is the lower limit of node transmission power. This is the lower limit of node transmission power. For nodes arrive The line current, This is the upper limit of the line current. Furthermore, the network flow constraint is a non-convex constraint, which makes Then the network flow constraint is: (16) In the formula, p j For nodes j The injected active power, q j For nodes j Injected reactive power, P jk For nodes j arrive k The active power of the line, For nodes arrive The active power of the line, Q jk For nodes j arrive k The reactive power of the line, For nodes arrive The reactive power of the line, for Branch circuit reactor.

6. The optimized control method for considering the loss characteristics of key equipment in flexible interconnected distribution networks according to claim 5, characterized in that: In step S5, the SOP installation capacity and output power are first initialized. The initialization data and system-related parameters are input into the SOP fixed capacity dual-layer optimization model. Then, the particle swarm algorithm is used to iteratively solve equations (9)-(16) of the SOP fixed capacity dual-layer optimization model to obtain the SOP installation capacity value under the condition of minimizing the daily comprehensive loss and annual comprehensive cost, which is the SOP fixed capacity result.

7. The optimized control method for considering the loss characteristics of key equipment in flexible interconnected distribution networks according to claim 6, characterized in that: In step S6, based on the SOP location result in step S3 and the SOP capacity determination result in step S5, the initial conditions of the lower-level optimization objective function in the SOP capacity determination double-layer optimization model are determined. Then, the Cplex commercial solver is used to solve equations (11)-(16) of the lower-level optimization objective function to obtain the output power of the SOP, and then the active power and reactive power transmitted by the SOP are obtained, thereby realizing the precise control of the power flow of the distribution network.

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