Transformer area bus loss assessment method and system based on electric energy quality

Abstract

The invention relates to the technical field of power grid power transmission, in particular to a transformer area bus loss assessment method and system based on electric energy quality, and the method mainly comprises the steps: defining a transformer area electric energy quality bus loss power factor, constructing a transformer area bus loss objective function based on the bus loss power factor, and solving the objective function according to a constraint condition. And outputting the result of the current objective function. According to the method, the definition of the transformer area electric energy quality bus loss power factor is provided, the similarities and differences between the transformer area bus loss power factor and the branch bus loss power factor are analyzed, and the underdetermined equation of the transformer area bus loss power factor is solved by utilizing topological constraints in consideration of the difficulty in acquisition of data of each branch of an actual transformer area. And finally, by establishing a statistical line loss model and determining constraint conditions, bypassing line resistance, length and parameter requirements, estimating the total power quality line loss of the transformer area only by using total active line loss data and branch power quality line loss power factors counted by the existing electric meters, and reducing errors.

Description

Technical Field

[0001] The present invention relates to the field of power grid transmission technology, and in particular to a method and system for evaluating bus loss in a substation area based on power quality. Background Art

[0002] Transmission and distribution losses account for approximately 6.6% of my country's total power generation losses. The highest proportion of power losses occurs primarily in the 10kV and 0.4kV distribution networks, accounting for approximately 70% of the total losses. Currently, power grid companies primarily manage line losses to reduce losses, but these methods fail to address the root causes of power quality issues. Only by managing and addressing line losses at the technical level can energy conservation and loss reduction be fundamentally achieved.

[0003] Power quality problems arise from a variety of factors, including voltage fluctuations, flicker, frequency deviation, supply voltage deviation, transient overvoltages, high-frequency interference, voltage sags, spikes, short interruptions, reactive power, harmonics, and three-phase imbalance. Reactive power, harmonics, and three-phase imbalance significantly impact grid line losses and are key factors contributing to a significant increase in line losses. The unbalanced integration of large amounts of distributed photovoltaic power generation and high-power single-phase loads can cause three-phase imbalance, leading to increased line losses. Statistics show that three-phase imbalance is particularly severe in rural areas. In some low-income rural areas, single-phase loads account for a significant proportion, accounting for approximately 50% of the total load capacity. In middle-income rural areas, single-phase loads account for at least 70%, while in high-income, affluent areas, the proportion reaches 90%. Furthermore, with the increase in new electrical equipment and nonlinear loads in the power system, harmonic problems are becoming increasingly severe, further increasing distribution network line losses.

[0004] To address power quality issues related to line losses, the first step is to accurately measure and evaluate line losses caused by reactive power, harmonics, and three-phase imbalance. However, in low-voltage systems, the meters widely installed on the customer side only measure fundamental power and are unable to measure and analyze energy beyond the fundamental. Furthermore, without energy metering equipment installed at each node in the substation, it's impossible to obtain line loss values for each branch line, making accurate line parameters difficult to determine.

[0005] Existing statistical line loss estimation methods all require an accurate line resistance value. For example, the FLUKE 435 Power Quality and Energy Analyzer, which can decouple power quality line losses, requires inputting the line resistance value when using its energy analysis function to calculate the decoupled line loss values for each component. However, due to the influence of skin effect and proximity effect under harmonic conditions, accurately determining harmonic resistance values is difficult. This operation can introduce significant errors and lacks practical application guidance. Furthermore, accurately measuring line length is often challenging under actual operating conditions in low-voltage distribution networks. Therefore, line resistance calculated based on line length may contain a certain degree of error. Summary of the Invention

[0006] The purpose of the present invention is to provide a method and system for evaluating bus loss in an area based on power quality to solve the above-mentioned problems in the prior art.

[0007] The present invention is achieved through the following technical solutions:

[0008] In a first aspect, the present invention provides a method for evaluating total bus loss in a substation based on power quality, comprising:

[0009] Define the total line loss power factor of the power quality of the substation area, where the total line loss power factor includes the active line loss power factor, the total reactive line loss power factor, the total unbalanced line loss power factor, and the total harmonic line loss power factor;

[0010] Constructing a bus loss objective function for the substation area based on the bus loss power factor and setting constraints, wherein the constraints include bus loss constraint, line length constraint, and resistivity constraint;

[0011] Solve the objective function according to the constraints and output the result of the current objective function.

[0012] Preferably, the bus loss power factor includes:

[0013]

[0014] Where PF eP_all is the total active line loss power factor, PF eQ_all is the total reactive line loss power factor, PF eU_all is the total unbalanced line loss power factor, PF eH_all is the total harmonic line loss power factor, ΔP eLoss_all Indicates the bus loss in the substation area, ΔP eP_all Indicates the total fundamental positive sequence active power line loss in the substation area, ΔP eQ_all Indicates the total fundamental positive sequence reactive power additional line loss in the substation area, ΔP eU_all Indicates the total unbalanced additional line loss in the substation area; ΔP eU_all Additional line loss for harmonics.

[0015] Preferably, the bus loss in the substation area includes:

[0016]

[0017] Where, P begin Indicates the active power of the transformer outlet at the head end of the substation (W), P end_x It represents the active power of the electric energy meter of the end user x of the branch, Indicates the line loss value on branch bx; I A_bx , I B_bx , I C_bx and I n_bx Respectively represent the phase current on branch bx, R bx It represents the equivalent resistance of the line after considering the skin effect and proximity effect on branch bx, r represents the resistivity after considering the skin effect and proximity effect, L bx Indicates the length of branch bx.

[0018] Preferably, the total fundamental positive sequence active line loss in the substation area, the total fundamental positive sequence reactive additional line loss in the substation area, the total unbalanced additional line loss in the substation area and the harmonic additional line loss include:

[0019]

[0020] Where, Indicates the fundamental positive sequence active power line loss of branch bx, PF eP_bx Indicates the fundamental positive sequence active line loss power factor of branch bx, Indicates the reactive additional line loss of branch bx, PF eQ_bx Indicates the reactive line loss power factor of branch bx; Indicates the unbalanced additional line loss (W) of branch bx, ΔP eU_bx Indicates the unbalanced line loss power factor of branch bx, Indicates the additional harmonic line loss of branch bx, PF eH_bx Indicates the harmonic line loss power factor of branch bx.

[0021] Preferably, the objective function includes

[0022]

[0023] Where, F eP To solve the total active line loss power factor PF eP_all Function of eQ Used to solve the total reactive line loss power factor PF eQ_all Function, F eU To solve the total unbalanced line loss power factor PF eU_all Function, FeH To solve the total harmonic line loss power factor PF eH_all function.

[0024] Preferably, the bus loss constraint includes:

[0025]

[0026] Where m is the number of branches.

[0027] Preferably, the line length constraint includes:

[0028]

[0029] Where, L all is the total length of the area line, L bx_min is the minimum length range of branch bx, L bx_max The maximum length range of branch bx.

[0030] Preferably, the resistivity constraint includes:

[0031] r min ≤r≤r max

[0032] Where r min is the minimum value of resistivity, r max is the maximum value of resistivity.

[0033] Preferably, solving the objective function according to the constraint conditions includes:

[0034] Establishing the relationship between all inequality constraints and all equality constraints, and using Lagrangian functions to establish KKT conditions for the relationship;

[0035] The direct step method of the form (x, s) is used to define the direct step (Δx, Δs) by solving the KKT condition of the approximation problem of the linear approximation solution;

[0036] By solving the linearized Lagrangian function, the result of minimizing the objective function is obtained.

[0037] In a second aspect, the present invention provides a system for evaluating total bus loss in a substation based on power quality, comprising:

[0038] A definition module is configured to define a total line loss power factor of the power quality of the substation area, wherein the total line loss power factor includes an active line loss power factor, a total reactive line loss power factor, a total unbalanced line loss power factor, and a total harmonic line loss power factor;

[0039] An objective function module is configured to construct a bus loss objective function for a substation based on a bus loss power factor and set constraints, wherein the constraints include a bus loss constraint, a line length constraint, and a resistivity constraint;

[0040] The solving module is configured to solve the objective function according to the constraint conditions and output the result of the current objective function.

[0041] The technical solution of the present invention has at least the following advantages and beneficial effects:

[0042] The method provided by the present invention mainly includes defining the bus loss power factor of the power quality of the substation, constructing the bus loss objective function of the substation based on the bus loss power factor, solving the objective function according to the constraint conditions, and outputting the result of the current objective function. The above method proposes the definition of the bus loss power factor of the power quality of the substation, and analyzes the similarities and differences between the bus loss power factor of the substation and the branch bus loss power factor. Taking into account the difficulty of collecting data of each branch in the actual substation, the underdetermined equation of the bus loss power factor of the substation is solved using topological constraints. Finally, by establishing a statistical line loss model and determining the constraint conditions, bypassing the line resistance, length and parameter requirements, only the total active line loss data and branch power quality line loss power factor statistically used in the existing electric meter are used to estimate the total power quality line loss of the substation, thereby reducing the error. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0044] Figure 1 This is a schematic diagram of the branch power line loss analysis in the substation area of the present invention;

[0045] Figure 2 The actual topological diagram of a certain cell of the present invention;

[0046] Figure 3 A cell topology user identification diagram of the present invention;

[0047] Figure 4 It is the simulated load setting of the station area of the present invention;

[0048] Figure 5 This is the station area line simulation data 1 of the present invention;

[0049] Figure 6 This is the second simulation data of the station line of the present invention;

[0050] Figure 7It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of 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. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0052] The division of modules in this application is a logical division. In actual application, there may be other division methods. For example, multiple modules can be combined or integrated into another system, or some features can be ignored or not executed.

[0053] Independently described modules or submodules may or may not be physically separate; they may be implemented in software or hardware. Some modules or submodules may be implemented in software, with the processor invoking the software to implement the functionality of these modules or submodules, while other modules or submodules may be implemented in hardware, such as hardware circuits. Furthermore, some or all of the modules may be selected based on actual needs to achieve the objectives of the present application.

[0054] Please refer to Figure 7 The present invention provides a method for evaluating total bus loss in a substation based on power quality, comprising:

[0055] S101: defining a total line loss power factor of power quality in the substation area, wherein the total line loss power factor includes active line loss power factor, total reactive line loss power factor, total unbalanced line loss power factor, and total harmonic line loss power factor;

[0056] For a substation with m branches, the power factor of the power quality line loss on each branch can represent the severity of the power quality line loss of the branch. At the same time, if you want to decouple the power quality line loss values of each part of the branch, you need to substitute the branch line loss of m branches. The schematic diagram of the decoupled branch power quality line loss analysis is as follows: Figure 1 shown.

[0057] However, in real-world substations, due to the lack of metering equipment between adjacent nodes, obtaining statistical line loss values for each branch is difficult, and it is also impossible to quantify the power quality line loss of decoupled branches. Relative to the entire substation, the branch line loss power factor only indicates the severity of the power quality line loss in that branch and the extent to which that branch is overwhelmed by non-active components. Even if a branch has severe power quality issues, if the branch current is low and the length is short, the total line loss will be relatively low.

[0058] In order to evaluate the total power quality line loss in the substation and quantify the additional line loss caused by the total reactive power, imbalance and harmonics in the substation, four substation power quality total loss power factors are defined from the perspective of line loss, namely: total active line loss power factor, total reactive line loss power factor, total unbalanced line loss power factor and total harmonic line loss power factor.

[0059] The total active line loss power factor for these four types of substation power quality measures range from 0 to 1. When there are no power quality issues on any of the substation's branches, the total active line loss power factor for all four types of substations is 1. The total active line loss power factor represents the extent to which the rated capacity of the power supply equipment is squeezed due to an increase in the non-active power component of the substation's end users.

[0060] S102: constructing a bus loss objective function for the substation area based on the bus loss power factor, and setting constraints, wherein the constraints include bus loss constraint, line length constraint, and resistivity constraint;

[0061] S103: Solve the objective function according to the constraint conditions and output the result of the current objective function.

[0062] The method provided by the present invention mainly includes defining the bus loss power factor of the power quality of the substation, constructing the bus loss objective function of the substation based on the bus loss power factor, solving the objective function according to the constraint conditions, and outputting the result of the current objective function. The above method proposes the definition of the bus loss power factor of the power quality of the substation, and analyzes the similarities and differences between the bus loss power factor of the substation and the branch bus loss power factor. Taking into account the difficulty of collecting data of each branch in the actual substation, the underdetermined equation of the bus loss power factor of the substation is solved using topological constraints. Finally, by establishing a statistical line loss model and determining the constraint conditions, bypassing the line resistance, length and parameter requirements, only the total active line loss data and branch power quality line loss power factor statistically used in the existing electric meter are used to estimate the total power quality line loss of the substation, thereby reducing the error.

[0063] In an exemplary embodiment of the present invention, the bus loss power factor includes:

[0064]

[0065] Where PF eP_all is the total active line loss power factor, PF eQ_all is the total reactive line loss power factor, PF eU_all is the total unbalanced line loss power factor, PF eH_all is the total harmonic line loss power factor, ΔP eLoss_all Indicates the bus loss in the substation area, ΔP eP_all Indicates the total fundamental positive sequence active power line loss in the substation area, ΔP eQ_all Indicates the total fundamental positive sequence reactive power additional line loss in the substation area, ΔPeU_all Indicates the total unbalanced additional line loss in the substation area; ΔP eH_all Additional line loss for harmonics.

[0066] The total line loss power factor (BLP) of a substation is defined based on the total line loss of the substation. It not only indicates the severity of the substation's power quality, but also the magnitude of each line loss and the degree of crowding out of power supply equipment within the substation, providing an indicator for determining whether to address the substation's power quality issues. Therefore, when deciding whether to address substation power quality issues, both the total line loss power factor and the branch line loss power factor should be considered as line loss assessment indicators to achieve the best treatment results and achieve energy savings and loss reduction.

[0067] For a substation with m branches and n users, the total line loss ΔPeLoss_all can be expressed as the sum of the line losses on the m branches, or as the active power metered at the transformer outlet at the substation headend minus the total active power metered at the user side. The total line loss in the substation includes:

[0068]

[0069] Where, P begin Indicates the active power of the transformer outlet at the head end of the substation (W), P end_x It represents the active power of the electric energy meter of the end user x of the branch, Indicates the line loss value on branch bx; I A_bx , I B_bx , I C_bx and I n_bx Respectively represent the phase current on branch bx, R bx It represents the equivalent resistance of the line after considering the skin effect and proximity effect on branch bx, r represents the resistivity after considering the skin effect and proximity effect, L bx Indicates the length of branch bx.

[0070] Based on the calculation function of the total bus loss power factor, it can be seen that in order to calculate the total bus loss power factor of the substation, it is necessary to obtain the total bus loss of the substation and the decoupled power quality line loss values of each part. However, in the actual monitoring data of the power grid company, only the total bus loss of the substation, that is, the line loss data of the first and last meters are known; but there is no electricity metering equipment installed at each node in the substation, so the line loss value on each branch is unknown. Since the solution conditions are less than the number of unknowns, it is impossible to solve the underdetermined equations (the calculation function of the line loss power factor and the calculation function of the total bus loss of the substation) by directly substituting the value of the total power quality line loss of the substation. Considering that the power quality line loss power factor on each branch can be solved, the total power quality line loss of each part of the substation decoupled in the calculation function of the line loss power factor is expressed as follows:

[0071] The total fundamental positive sequence active line loss, the total fundamental positive sequence reactive additional line loss, the total unbalanced additional line loss and the harmonic additional line loss in the substation area include:

[0072]

[0073] Where, Indicates the fundamental positive sequence active power line loss of branch bx, PF eP_bx Indicates the fundamental positive sequence active line loss power factor of branch bx, Indicates the reactive additional line loss of branch bx, PF eQ_bx Indicates the reactive line loss power factor of branch bx; Indicates the unbalanced additional line loss of branch bx (W), PF eU_bx Indicates the unbalanced line loss power factor of branch bx, Indicates the additional harmonic line loss of branch bx, PF eH_bx Indicates the harmonic line loss power factor of branch bx.

[0074] Specifically, the objective function includes

[0075]

[0076] Where, F eP To solve the total active line loss power factor PF eP_all Function of eQ Used to solve the total reactive line loss power factor PF eO_all Function, F eU To solve the total unbalanced line loss power factor PF eU_all Function, F eH To solve the total harmonic line loss power factor PF eH_all function.

[0077] Based on the actual topology of the distribution network substation, the installation of existing electricity metering equipment, and actual data from the power grid company, the substation bus loss power factor solution model sets the following bus loss constraints, line length constraints, and resistivity constraints. The substation has m branches.

[0078] Considering that electric energy metering equipment is installed on both the transformer outlet side and the user side of the substation, and the statistical line loss of the substation is known, the total line loss constraint is set:

[0079]

[0080] Where m is the number of branches.

[0081] Considering that the total length of the substation line is known and the range of each branch line length is known, set the line length constraint:

[0082]

[0083] Where, L all is the total length of the area line, L bx_min is the minimum length range of branch bx, L bx_max The maximum length range of branch bx.

[0084] Considering the skin effect and proximity effect, which make it difficult to accurately obtain the line resistivity, the line resistivity constraint is set based on existing research:

[0085] r min ≤r≤r max

[0086] Where r min is the minimum value of resistivity, r max is the maximum value of resistivity.

[0087] By using the above formula as a constraint condition and solving the extreme value of the function constructed in the resistivity constraint, the range of the total power loss power factor of the substation power quality system can be calculated, thereby evaluating the total power loss of the substation power quality system.

[0088] In an exemplary embodiment of the present invention, solving the objective function according to the constraint conditions includes:

[0089] S201: establishing a relationship between all inequality constraints and all equality constraints, and using Lagrangian functions to establish KKT conditions for the relationship;

[0090]

[0091] Where g(x) represents all inequality constraints, h(x) represents all equality constraints, and f(x) is the objective function.

[0092] First-order optimality for constrained problems is more complex than for unconstrained problems. The theoretical definition of optimality for constrained problems is based on the Karush-Kuhn-Tucker (KKT) conditions. The KKT conditions use an auxiliary Lagrangian function.

[0093] L(x,λ)=f(x)+ ∑ λ g,i g i (x)+ ∑ λ h,i h i (x)

[0094] Where λ is the Lagrange multiplier vector, λ g,i is the multiplier of the inequality constraint, λ h,i is the multiplier for the equality constraint.

[0095] KKT conditions include:

[0096]

[0097] Where i is the index of all constraints.

[0098] When the barrier parameter μ>0, the approximation problem is as follows:

[0099]

[0100] subject to s≥0,h(x)=0and g(x)+s=0

[0101] Where, f μ (x, s) is the corrected objective function, s i is the i-th slack variable, s is the vector of all slack variables, and μ is the barrier parameter.

[0102] The number of inequality constraints g is the same as the number of slack variables si. At the same time, in order to always run the iteration within the feasible region, S i Restricted to positive numbers. Function f μ The minimum value of μ approaches the minimum value of function f when μ decreases to 0.

[0103] S202: using a direct step method of the form (x, s) to define the direct step (Δx, Δs) by using the KKT condition of the approximation problem of the linear approximation solution;

[0104]

[0105] Where H represents the function f μ The Hessian matrix of the Lagrangian function, J h and J g are the Jacobian matrices of the constraint functions g and h, respectively. y is the Lagrange multiplier vector associated with constraint h. e represents a vector of 1s of the same size as constraint g.

[0106] By solving the linearized Lagrangian function, the result of minimizing the objective function is obtained.

[0107] In this embodiment, a practical example is given to explain the above content.

[0108] This section uses a real area simulation example to verify the proposed method. The actual area topology is shown in the figure below. Figure 2 As shown, the cell topology user identification diagram is as follows Figure 3In the simulation of this substation, the user settings are shown in Table 1. The resistivity r considering the skin effect and proximity effect is set to 0.320Ω / km. The length of each branch is set to the same as the simulation data as shown in Table 1. Figure 4 、 5 , as shown in 6.

[0109] The actual value of the total line loss ΔPeLoss_all is 13016.43W; the range of the resistivity r considering the skin effect and proximity effect is set to 0.264-0.348Ω / km [20,31]; the length Lbx of the branch bx is within the range of ±50m of the actual line length, and the total length is 4825m. Using the extreme value of the total line loss function constructed in the above constraint solution, the results are Figure 7 shown.

[0110] pass Figure 7 It can be seen that compared with the actual value, the total reactive line loss power factor PF calculated by the method in this chapter is eQ_all , total unbalanced line loss power factor PF eU_all , total harmonic line loss power factor PF eH_all and total active line loss power factor PF eP_all The above analysis shows that the method of solving the underdetermined equation of the power factor of the power quality bus loss in the substation based on topology constraints, calculating the power factor of the substation bus loss, and evaluating the substation bus loss is feasible.

[0111] In a second aspect, the present invention provides a system for evaluating total bus loss in a substation based on power quality, comprising:

[0112] A definition module is configured to define a total line loss power factor of the power quality of the substation area, wherein the total line loss power factor includes an active line loss power factor, a total reactive line loss power factor, a total unbalanced line loss power factor, and a total harmonic line loss power factor;

[0113] An objective function module is configured to construct a bus loss objective function for a substation based on a bus loss power factor and set constraints, wherein the constraints include a bus loss constraint, a line length constraint, and a resistivity constraint;

[0114] The solving module is configured to solve the objective function according to the constraint conditions and output the result of the current objective function.

[0115] In addition, the functional units in the various embodiments of the present invention may be integrated into a single processing unit, each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0116] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. The computer software product is stored in a storage medium and includes a number of instructions for causing a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the various embodiments of the present invention. The aforementioned storage medium includes: USB flash drives, mobile hard drives, read-only memories (ROMs), random access memories (RAMs), magnetic disks, optical disks, and other media that can store program code.

[0117] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for evaluating total bus loss in a substation based on power quality, characterized in that: include: Define the total line loss power factor of the power quality of the substation area, where the total line loss power factor includes the active line loss power factor, the total reactive line loss power factor, the total unbalanced line loss power factor, and the total harmonic line loss power factor; Constructing a bus loss objective function for the substation area based on the bus loss power factor and setting constraints, wherein the constraints include bus loss constraint, line length constraint, and resistivity constraint; Solve the objective function according to the constraints and output the result of the current objective function.

2. The method for evaluating total bus loss in a substation based on power quality according to claim 1, characterized in that: The bus loss power factor includes: Where PF eP_all is the total active line loss power factor, PF eQ_all is the total reactive line loss power factor, PF eU_all is the total unbalanced line loss power factor, PF eH_all is the total harmonic line loss power factor, ΔP eLoss_all Indicates the bus loss in the substation area, ΔP eP_all Indicates the total fundamental positive sequence active power line loss in the substation area, ΔP eQ_all Indicates the total fundamental positive sequence reactive power additional line loss in the substation area, ΔP eU_all Indicates the total unbalanced additional line loss in the substation area; ΔP eH_all Additional line loss for harmonics.

3. The method for evaluating total bus loss in a substation based on power quality according to claim 2, wherein: The bus loss in the substation area includes: Where, P begin Indicates the active power of the transformer outlet at the head end of the substation (W), P end_x It represents the active power of the electric energy meter of the end user x of the branch, Indicates the line loss value on branch bx; I A_bx , I B_bx , I C_bx and I n_bx Respectively represent the phase current on branch bx, R bx It represents the equivalent resistance of the line after considering the skin effect and proximity effect on branch bx, r represents the resistivity after considering the skin effect and proximity effect, L bx Indicates the length of branch bx.

4. The method for evaluating total bus loss in a substation based on power quality according to claim 3, characterized in that: The total fundamental positive sequence active line loss, the total fundamental positive sequence reactive additional line loss, the total unbalanced additional line loss and the harmonic additional line loss in the substation area include: Where, Indicates the fundamental positive sequence active power line loss of branch bx, PF eP_bx Indicates the fundamental positive sequence active line loss power factor of branch bx, Indicates the reactive additional line loss of branch bx, PF eQ_bx Indicates the reactive line loss power factor of branch bx; Indicates the unbalanced additional line loss of branch bx (W), PF eU_br Indicates the unbalanced line loss power factor of branch bx, Indicates the additional harmonic line loss of branch bx, PF eH_bx Indicates the harmonic line loss power factor of branch bx.

5. The method for evaluating total bus loss in a substation based on power quality according to claim 4, characterized in that: The objective function includes Where, F eP To solve the total active line loss power factor PF eP_all Function of eQ Used to solve the total reactive line loss power factor PF eQ_all Function, F eU To solve the total unbalanced line loss power factor PF eU_all Function, F eH To solve the total harmonic line loss power factor PF eH_all function.

6. The method for evaluating total bus loss in a substation based on power quality according to claim 5, characterized in that: The bus loss constraint includes: Where m is the number of branches.

7. The method for evaluating total bus loss in a substation area based on power quality according to claim 6, characterized in that: The line length constraints include: Where, L all is the total length of the area line, L bx_min is the minimum length range of branch bx, L bx_max The maximum length range of branch bx.

8. The method for evaluating total bus loss in a substation area based on power quality according to claim 7, characterized in that: The resistivity constraints include: r min ≤r≤r max Where r min is the minimum value of resistivity, r max is the maximum value of resistivity.

9. The method for evaluating total bus loss in a substation area based on power quality according to claim 7, characterized in that: Solving the objective function according to the constraint conditions includes: Establishing the relationship between all inequality constraints and all equality constraints, and using Lagrangian functions to establish KKT conditions for the relationship; The direct step method of the form (x, s) is used to define the direct step (Δx, Δs) by solving the KKT condition of the approximation problem of the linear approximation solution; By solving the linearized Lagrangian function, the result of minimizing the objective function is obtained.

10. A system for evaluating total bus loss in a substation based on power quality, characterized in that: include: A definition module is configured to define a total line loss power factor of the power quality of the substation area, wherein the total line loss power factor includes an active line loss power factor, a total reactive line loss power factor, a total unbalanced line loss power factor, and a total harmonic line loss power factor; An objective function module is configured to construct a bus loss objective function for a substation based on a bus loss power factor and set constraints, wherein the constraints include a bus loss constraint, a line length constraint, and a resistivity constraint; The solving module is configured to solve the objective function according to the constraint conditions and output the result of the current objective function.

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