CN110707685A - Optimization method for power quality energy-saving efficiency-increasing scheme of power distribution network - Google Patents

Optimization method for power quality energy-saving efficiency-increasing scheme of power distribution network Download PDF

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CN110707685A
CN110707685A CN201910841452.5A CN201910841452A CN110707685A CN 110707685 A CN110707685 A CN 110707685A CN 201910841452 A CN201910841452 A CN 201910841452A CN 110707685 A CN110707685 A CN 110707685A
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power
distribution network
power distribution
loss
comprehensive treatment
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CN110707685B (en
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黄道姗
张慧瑜
林焱
林芳
杜培
陈伯建
张伟骏
苏清梅
张健
刘智煖
方晓玲
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Electric Power Research Institute of State Grid Fujian Electric Power Co Ltd
State Grid Fujian Electric Power Co Ltd
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Electric Power Research Institute of State Grid Fujian Electric Power Co Ltd
State Grid Fujian Electric Power Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/01—Arrangements for reducing harmonics or ripples
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/26—Arrangements for eliminating or reducing asymmetry in polyphase networks
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/40—Arrangements for reducing harmonics
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/50—Arrangements for eliminating or reducing asymmetry in polyphase networks

Abstract

The invention relates to a power quality energy-saving efficiency-increasing scheme optimization method for a power distribution network, which comprises the steps of firstly, dividing a network into each sub-region by adopting a Kmeans clustering method, then determining the optimal distribution point of a power quality control device through SI (stability index) in each sub-region, and then considering two targets of power quality control: loss reduction amount and economy, and energy-saving potential quantitative calculation after comprehensive quality management of the power distribution network is carried out; and aiming at the problem that objective functions in multi-objective optimization often conflict with each other, multi-objective optimization is carried out, and finally a power quality control optimal scheme is formed. The invention realizes the zoning and the point distribution of the power distribution network in consideration of the electrical distance; the energy-saving and loss-reducing effects of the power distribution network are improved.

Description

Optimization method for power quality energy-saving efficiency-increasing scheme of power distribution network
Technical Field
The invention relates to the technical field of operation of a power distribution network, in particular to an optimal selection method of an energy-saving and efficiency-increasing scheme of the power quality of the power distribution network.
Background
With the continuous development of national economy, electric energy plays an important role in the overall development of social economy. Especially in recent years, unnecessary waste of electric energy has attracted extensive attention of various social circles, how to save energy and reduce loss has become a great challenge for the economic and macroscopic development of China, and is also a research subject for diligent efforts of electric power people.
At present, loss reduction technical methods become the key point of research of domestic and foreign power people, measures for realizing energy conservation and loss reduction of a power distribution network from the technical aspect are mainly divided into two major categories, namely construction measures and operation measures. The construction measures mainly comprise scientific planning of a 10kV or below distribution network, active adoption of energy-saving power transmission equipment in a rural power grid, reasonable configuration and putting of a reactive power compensation device, popularization of reactive power random compensation, popularization and use of energy-saving electric equipment such as a crystal transformer and the like. The operation measures mainly comprise reasonable load and voltage adjustment, determination of an economic operation mode of a power grid, balance of three-phase loads, economic operation of a transformer, improvement of the health level of power supply equipment, development of live-line work and the like.
The existing method does not realize comprehensive treatment, namely respective treatment of three-phase unbalance, voltage, reactive power and harmonic.
Disclosure of Invention
In view of this, the invention aims to provide a preferable method for a power quality energy-saving efficiency-increasing scheme of a power distribution network, which can improve the energy-saving and loss-reducing effects of the power distribution network.
The invention is realized by adopting the following scheme: a power quality energy-saving efficiency-increasing scheme optimization method for a power distribution network comprises the following steps:
step S1: dividing the network into each sub-region by adopting a Kmeans clustering method, and determining the optimal distribution point of the electric energy quality comprehensive treatment device through the stability index (SI index) in each sub-region;
step S2: two goals of comprehensive treatment of power quality are considered: the network loss reduction amount after the power quality comprehensive treatment device is installed, the investment cost and the self running cost of the multi-target power quality comprehensive treatment device are calculated, and the energy-saving potential after the power distribution network quality comprehensive treatment is quantized;
the quantitative calculation formula of the energy-saving potential of the power distribution network is as follows: TES is f1-f2-f3Wherein f is1Representing a network loss reduction value after the implementation of the power quality comprehensive treatment scheme; f. of2Representing the investment cost of the increased electric energy quality comprehensive treatment device; f. of3The operation cost of the multi-target power quality comprehensive treatment device is represented;
step S3: considering a power distribution network planning and transformation scene, namely considering investment costs of line new construction or transformation and transformer new construction or transformation, and carrying out quantitative calculation on the energy-saving potential of a power distribution network in the power distribution network planning and transformation scene;
step S4: establishing a loss reduction target function F1Target function F for charging after implementation of comprehensive control scheme for power quality2And optimizing to obtain the optimal scheme for controlling the power quality.
Further, the step S1 specifically includes the following steps:
step S11: clustering and partitioning a distance matrix constructed by a topological structure and parameters of the power distribution network by using a Kmeans clustering method, and dividing the whole power distribution network into a plurality of sub-regions;
firstly, a node association matrix A is obtained from a network topology structure of the power distribution network, and if the number of nodes of the power distribution network is n, the matrix A is (a)ij)n×nIs a symmetric matrix of order n × n, and each element in the matrix a is defined as follows:
then, an incidence matrix A obtained by combining the network parameters of the power distribution network is provided to calculate an electrical distance matrix D between each node, wherein the matrix D is (D)ij)n×nIs a symmetric matrix of n x n order, the element d in the matrixijRepresents the distance between node i and node j; the values of the elements in the matrix D in a 4-node system are defined as follows:
partitioning the power distribution network by clustering and analyzing the distance matrix D;
step S12: and selecting a load center in each subarea as a mounting point of the comprehensive power quality treatment device to avoid uneven distribution of comprehensive power quality treatment positions and overlapping of treatment ranges.
Further, the step S12 specifically includes the following steps: the stability index numerical values of the nodes in each partition of the power distribution network are calculated, and the node with the maximum stability index numerical value in each partition is the installation position of the comprehensive power quality control device;
the specific process for calculating the stability index value of the power distribution network comprises the following steps:
the current flowing through the distribution network line is:θmand thetanAre respectively a voltage VmAnd VnThe complex power is: s is VI, then
Figure BDA0002193362310000034
According to the two above ImThe expressions of (a) are cross multiplied to obtain:
Figure BDA0002193362310000035
assuming that the real part and the imaginary part are equal,
Figure BDA0002193362310000036
the phase angle of the voltage can be ignored to obtain
VmVn-Vn 2＝PnRm+QnXm
Figure BDA0002193362310000041
Substituting the above two formulas to obtain:
Figure BDA0002193362310000042
to ensure that the root of the above formula is a solid root, it is necessary to satisfy
Figure BDA0002193362310000043
Therefore, the stability index is calculated by the formula:calculating all nodes in different partitions of power distribution networkThe node with the maximum stability index value in the subarea is the candidate node for installing the comprehensive control device for the power quality in the subarea.
Further, in step S2, the specific calculation process of the network loss reduction amount after the power quality comprehensive treatment device is installed is as follows:
after the power quality comprehensive treatment device is installed, namely the network loss reduction value after the power quality comprehensive treatment scheme is implemented is expressed as follows:
f1＝Wtotal＝Ke(ΔPloss-peak×Tpeak+ΔPloss-medium×Tmedium+ΔPloss-light×Tlight)
in the formula, KeIs the cost of the network loss reduction; delta Ploss-peak、TpeakRespectively representing network loss reduction unit kW and duration unit hour of the heavy load level before and after the implementation of the comprehensive control scheme for the power quality at the heavy load level; delta Ploss-light、TlightRespectively representing a unit kW of network loss reduction and a unit hour of duration of the light load level before and after the implementation of the comprehensive control scheme of the power quality at the light load level; delta Ploss-medium、TmediumNetwork loss reduction unit kW and normal load level duration unit hour before and after the implementation of the power quality comprehensive treatment scheme at the normal load level are respectively set; the sum of the duration of different load levels is one year, Tpeak+Tlight+Tmedium＝8760h；
Assuming that the additional loss of the distribution transformer and the distribution line is equal to the sum of the additional loss under the disturbance of three composite power qualities of harmonic wave, three-phase imbalance and voltage deviation, the network loss reduction before and after the implementation of the comprehensive power quality control scheme is represented as follows:
Figure BDA0002193362310000051
ΔPloss＝ΔPloss-peak+ΔPloss-medium+ΔPloss-light
wherein, Δ PTransformAnd Δ PLineLosses of the transformer and the line, respectively; HRIhThe h-th harmonic content; i1 is the root mean square value of the fundamental current; rTThe constant resistance of the transformer winding is the fundamental wave; kTRepresenting the three-phase unbalance coefficient of the transformer; i isavIs the average value of the effective values of three-phase current, i.e. Iav＝(IA+IB+IC)/3，IA、IB、ICIs the effective value of each phase current; u shapeNThe rated voltage of the distribution transformer; poIs the no-load loss of the distribution transformer at rated voltage; delta is the voltage deviation, delta ═ U-UN)/UNX is 100%; γ is a coefficient related to the transformer voltage deviation: when the | delta | is less than 7%, the gamma is 2, when the | delta | is less than or equal to 7% and less than 10%, the gamma is 3.5, and when the | delta | is more than or equal to 10%, the gamma is 4; rLhIs equivalent resistance, K, under the h harmonic wave of the cableLRepresenting the three-phase unbalance coefficient of the line, RLIs the line fundamental wave resistance.
Further, the specific calculation process of the investment cost of the multi-target power quality comprehensive treatment device in the step S2 is as follows:
considering the investment cost of increasing the comprehensive treatment device for the power quality, the investment cost is shown as the following formula:
Figure BDA0002193362310000061
wherein K is a conversion factor; priceMOPQCDThe installation and maintenance cost of the comprehensive treatment device for the electric energy quality; m is the number of installed devices; priceSIs the price per unit capacity of the device, SMOPQCDiCompensation capacity at ith for installation;
because the installation cost of the electric energy quality comprehensive treatment equipment is one-time investment, conversion needs to be carried out according to the service life of the equipment, and the calculation formula of the conversion coefficient K is as follows:
Figure BDA0002193362310000062
in the formula, r is the equipment depreciation rate; n isMOPQCDThe service life of the device.
Further, the specific calculation process of the self operation cost of the multi-target power quality comprehensive treatment device in the step S2 is as follows:
the self running cost of the multi-target electric energy quality comprehensive treatment device is related to power electronic devices and main components used in the device, and the voltage-sharing resistance loss at the direct current side can be ignored;
the operating cost of a three-phase four-wire device is as follows:
f3＝4m(Psw+Pt+PD+Pshunt)
wherein, PswThe switch loss, P, of the IGBT used in the multi-target electric energy quality comprehensive treatment devicesw＝Fpwm*[Eon+Eoff](ii) a Wherein, FpwmIndicating the switching frequency, Eon+EoffRepresents the heat when the IGBT is turned on or off; ptIs the on-state loss, P, of the IGBTt＝Ic*Vce(ii) a Wherein, VceIs the voltage between the collector and emitter of the tube, IcIs the collector current; pDIs the diode loss of the IGBT with a tube voltage drop of 0.7, PD＝0.7*IC。
Further, in step S3, the specific formula for quantitatively calculating the energy saving potential of the power distribution network in the power distribution network planning and transformation scenario is as follows:
wherein priceLineShowing the unit price of a line to be reformed or newly built is planned to be ten thousand yuan/kilometer; pricetypeThe construction cost or the line cost unit generated additionally due to different line types of the line to be replaced or modified is ten thousand yuan/kilometer;
Figure BDA0002193362310000074
the unit of expense generated by the replacement of the distribution transformer is represented by ten thousand yuan; c is the number of transformers to be modified or replaced; length means the unit kilometer of the modified or replaced wire Length.
Further, the step S4 specifically includes the following steps:
the objective function is specifically:
Figure BDA0002193362310000072
constraint conditions are as follows: the equality constraint, i.e., the power flow constraint, is shown as follows:
in the formula, PiRepresenting the injected active power of the node i; qiRepresents the injected reactive power of node i; b isij、GijRespectively representing conductance susceptances between nodes i and j; n represents the total number of nodes;
inequality constraint conditions:
Uimin≤Ui≤Uimax,i∈Nb
Figure BDA0002193362310000081
0≤SMOPQCDi≤SMOPQCDimax,i∈m
THDi≤THDmax
Figure BDA0002193362310000082
wherein N represents the number of nodes of the power distribution network; u shapeimin、UimaxThe upper limit and the lower limit of the node voltage are respectively within the interval of 0.9 and 1.1; simin、SiminRespectively an upper limit and a lower limit of the line power flow; sMOPQCDimaxThe upper limit of the capacity of the electric energy quality comprehensive treatment device is represented, and 10000kVA is used; THDmax5 percent according to the national standard.
Compared with the prior art, the invention has the following beneficial effects:
the invention aims at reducing the system network loss to the maximum extent, provides an optimal distribution method for comprehensive treatment of electric energy quality based on a clustering technology, and realizes distribution network partition and distribution considering the electric distance; the energy-saving and loss-reducing effects of the power distribution network are improved.
Drawings
Fig. 1 is a topology structure diagram of a power distribution network system according to an embodiment of the present invention.
Fig. 2 is a diagram of a two-node power distribution system according to an embodiment of the invention.
Fig. 3 is a topology structure diagram of a three-phase four-wire device according to an embodiment of the present invention.
FIG. 4 is an on-state loss diagram of an England IGBT (FF300R12ME4) according to an embodiment of the present invention.
Fig. 5 is a topology structure diagram of an IEEE-33 node network according to an embodiment of the present invention.
Detailed Description
The invention is further explained below with reference to the drawings and the embodiments.
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an", and/or "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of the features, steps, operations, devices, components, and/or combinations thereof.
In this embodiment, a preferable method for a power quality energy-saving efficiency-increasing scheme of a power distribution network includes the following steps:
step S1: dividing the network into each sub-region by adopting a Kmeans clustering method, and determining the optimal distribution point of the electric energy quality comprehensive treatment device through the stability index (SI index) in each sub-region;
step S2: two goals of comprehensive treatment of power quality are considered: the network loss reduction amount after the power quality comprehensive treatment device is installed, the investment cost and the self running cost of the multi-target power quality comprehensive treatment device are calculated, and the energy-saving potential after the power distribution network quality comprehensive treatment is quantized;
the quantitative calculation formula of the energy-saving potential of the power distribution network is as follows: TES is f1-f2-f3Wherein f is1Representing a network loss reduction value after the implementation of the power quality comprehensive treatment scheme; f. of2Representing the investment cost of the increased electric energy quality comprehensive treatment device; f. of3The operation cost of the multi-target power quality comprehensive treatment device is represented;
step S3: considering a power distribution network planning and transformation scene, namely considering investment costs of line new construction or transformation and transformer new construction or transformation, and carrying out quantitative calculation on the energy-saving potential of a power distribution network in the power distribution network planning and transformation scene;
step S4: establishing a loss reduction target function F1Target function F for charging after implementation of comprehensive control scheme for power quality2And optimizing to obtain the optimal scheme for controlling the power quality.
In this embodiment, the step S1 specifically includes the following steps:
step S11: clustering and partitioning a distance matrix constructed by a topological structure and parameters of the power distribution network by using a Kmeans clustering method, and dividing the whole power distribution network into a plurality of sub-regions;
firstly, a node association matrix A is obtained from a network topology structure of the power distribution network, and if the number of nodes of the power distribution network is n, the matrix A is (a)ij)n×nIs a symmetric matrix of order n × n, and each element in the matrix a is defined as follows:
Figure BDA0002193362310000101
then, an incidence matrix A obtained by combining the network parameters of the power distribution network is provided to calculate an electrical distance matrix D between each node, wherein the matrix D is (D)ij)n×nIs a symmetric matrix of n x n order, the element d in the matrixijRepresents the distance between node i and node j; the values of the elements in the matrix D in a 4-node system are defined as follows:
Figure BDA0002193362310000102
partitioning the power distribution network by clustering and analyzing the distance matrix D;
step S12: and selecting a load center in each subarea as a mounting point of the comprehensive power quality treatment device to avoid uneven distribution of comprehensive power quality treatment positions and overlapping of treatment ranges.
In this embodiment, the step S12 specifically includes the following steps: the stability index numerical value of each node in each partition of the power distribution network is calculated, and the node with the maximum stability index numerical value in each partition is the installation position of the comprehensive control device for the power quality;
the specific process for calculating the stability index value of the power distribution network comprises the following steps:
the current flowing through the distribution network line is:θmand thetanAre respectively a voltage VmAnd VnThe complex power is: s is VI, then
According to the two above ImThe expressions of (a) are cross multiplied to obtain:
Figure BDA0002193362310000113
assuming that the real part and the imaginary part are equal,
Figure BDA0002193362310000118
the phase angle of the voltage can be ignored to obtain
VmVn-Vn 2＝PnRm+QnXm
Figure BDA0002193362310000114
Substituting the above two formulas to obtain:
Figure BDA0002193362310000115
to ensure that the root of the above formula is a solid root, it is necessary to satisfy
Figure BDA0002193362310000116
Therefore, the stability index is calculated by the formula:
Figure BDA0002193362310000117
and calculating the stability index values of all nodes in different partitions of the power distribution network, wherein the node with the maximum stability index value in a partition is a candidate node for installing the comprehensive control device for the power quality in the partition.
In this embodiment, the specific calculation process of the network loss reduction amount after the installation of the power quality comprehensive treatment device in step S2 is as follows:
after the power quality comprehensive treatment device is installed, namely the network loss reduction value after the power quality comprehensive treatment scheme is implemented is expressed as follows:
f1＝Wtotal＝Ke(ΔPloss-peak×Tpeak+ΔPloss-medium×Tmedium+ΔPloss-light×Tlight)
in the formula, KeIs the cost of the network loss reduction; delta Ploss-peak、TpeakNetwork drop before and after implementation of comprehensive control scheme for power quality at heavy load levelLoss in kW and duration of heavy load level in hours; delta Ploss-light、TlightRespectively representing a unit kW of network loss reduction and a unit hour of duration of the light load level before and after the implementation of the comprehensive control scheme of the power quality at the light load level; delta Ploss-medium、TmediumNetwork loss reduction unit kW and normal load level duration unit hour before and after the implementation of the power quality comprehensive treatment scheme at the normal load level are respectively set; the sum of the duration of different load levels is one year, Tpeak+Tlight+Tmedium＝8760h；
Assuming that the additional loss of the distribution transformer and the distribution line is equal to the sum of the additional loss under the disturbance of three composite power qualities of harmonic wave, three-phase imbalance and voltage deviation, the network loss reduction before and after the implementation of the comprehensive power quality control scheme is represented as follows:
Figure BDA0002193362310000121
ΔPloss＝ΔPloss-peak+ΔPloss-medium+ΔPloss-light
wherein, Δ PTransformAnd Δ PLineLosses of the transformer and the line, respectively; HRIhThe h-th harmonic content; i is1Is the root mean square value of the fundamental current; rTThe constant resistance of the transformer winding is the fundamental wave; kTRepresenting the three-phase unbalance coefficient of the transformer; i isavIs the average value of the effective values of three-phase current, i.e. Iav＝(IA+IB+IC)/3，IA、IB、ICIs the effective value of each phase current; u shapeNThe rated voltage of the distribution transformer; poIs the no-load loss of the distribution transformer at rated voltage; delta is the voltage deviation, delta ═ U-UN)/UNX is 100%; γ is a coefficient related to the transformer voltage deviation: when the | delta | is less than 7%, the gamma is 2, when the | delta | is less than or equal to 7% and less than 10%, the gamma is 3.5, and when the | delta | is more than or equal to 10%, the gamma is 4; rLhIs a cableEquivalent resistance, K, at the h harmonicLRepresenting the three-phase unbalance coefficient of the line, RLIs the line fundamental wave resistance.
In this embodiment, the specific calculation process of the investment cost of the multi-target power quality comprehensive treatment device in step S2 is as follows:
considering the investment cost of increasing the comprehensive treatment device for the power quality, the investment cost is shown as the following formula:
wherein K is a conversion factor; priceMOPQCDThe installation and maintenance cost of the comprehensive treatment device for the electric energy quality; m is the number of installed devices; priceSIs the price per unit capacity of the device, SMOPQCDiCompensation capacity at ith for installation;
because the installation cost of the electric energy quality comprehensive treatment equipment is one-time investment, conversion needs to be carried out according to the service life of the equipment, and the calculation formula of the conversion coefficient K is as follows:
Figure BDA0002193362310000132
in the formula, r is the equipment depreciation rate; n isMOPQCDThe service life of the device.
In this embodiment, the specific calculation process of the self operation cost of the multi-target power quality comprehensive treatment device in step S2 is as follows:
the self running cost of the multi-target electric energy quality comprehensive treatment device is related to power electronic devices and main components used in the device, and the voltage-sharing resistance loss at the direct current side can be ignored;
the operating cost of a three-phase four-wire device is as follows:
f3＝4m(Psw+Pt+PD+Pshunt)
wherein, PswThe switch loss, P, of the IGBT used in the multi-target electric energy quality comprehensive treatment devicesw＝Fpwm*[Eon+Eoff](ii) a Wherein, FpwmRepresenting the switching frequency Eon+EoffRepresents the heat when the IGBT is turned on or off; ptIs the on-state loss, P, of the IGBTt＝Ic*Vce(ii) a Wherein, VceIs the voltage between the collector and emitter of the tube, IcIs the collector current; pDIs the diode loss of the IGBT with a tube voltage drop of 0.7, PD＝0.7*IC。
In this embodiment, the specific formula for quantitatively calculating the energy saving potential of the power distribution network in the power distribution network planning and transformation scenario in step S3 is as follows:
Figure BDA0002193362310000141
wherein priceLineShowing the unit price of a line to be reformed or newly built is planned to be ten thousand yuan/kilometer; pricetypeThe construction cost or the line cost unit generated additionally due to different line types of the line to be replaced or modified is ten thousand yuan/kilometer;
Figure BDA0002193362310000142
the unit of expense generated by the replacement of the distribution transformer is represented by ten thousand yuan; c is the number of transformers to be modified or replaced; length means the unit kilometer of the modified or replaced wire Length.
In this embodiment, the step S4 specifically includes the following steps:
the objective function is specifically:
Figure BDA0002193362310000151
constraint conditions are as follows: the equality constraint, i.e., the power flow constraint, is shown as follows:
in the formula, PiIndicates that node i is injected withWork power; qiRepresents the injected reactive power of node i; b isij、GijRespectively representing conductance susceptances between nodes i and j; n represents the total number of nodes;
inequality constraint conditions:
Uimin≤Ui≤Uimax,i∈Nb
Figure BDA0002193362310000153
0≤SMOPQCDi≤SMOPQCDimax,i∈m
THDi≤THDmax
Figure BDA0002193362310000154
wherein N represents the number of nodes of the power distribution network; u shapeimin、UimaxThe upper limit and the lower limit of the node voltage are respectively within the interval of 0.9 and 1.1; simin、SiminRespectively an upper limit and a lower limit of the line power flow; sMOPQCDimaxThe upper limit of the capacity of the electric energy quality comprehensive treatment device is represented, and 10000kVA is used; THDmax5 percent according to the national standard.
Preferably, the specific examples of the present embodiment are as follows:
and a suitable power quality comprehensive treatment position is searched, namely the optimal combination of the system nodes, and compared with the combination of other nodes with the same quantity, the power quality comprehensive treatment equipment with the same capacity is added in the nodes, so that the system network loss can be reduced to the maximum extent.
Aiming at the selection problem of the comprehensive treatment position of the power quality, a point selection method based on a Kmeans clustering method is provided. The basic idea of the method is as follows: firstly, clustering and partitioning a distance matrix constructed by a topological structure and parameters of the power distribution network by using a Kmeans clustering method, and dividing the whole power distribution network into a plurality of sub-regions; and then selecting a load center in each subarea as a mounting point of the electric energy quality comprehensive treatment equipment, so that the problems of uneven distribution of electric energy quality comprehensive treatment positions, overlapping treatment ranges and the like are avoided.
Obtaining a node incidence matrix A from a network topology structure of the power distribution network, and if the number of nodes of the power distribution network is n, obtaining the matrix A as (a)ij)n×nIs a symmetric matrix of order n × n, and each element in the matrix a is defined as follows:
Figure BDA0002193362310000161
the electrical distance matrix D between each node is obtained by the known network parameters of the power distribution network and the obtained incidence matrix A, and the matrix D is (D)ij)n×nAlso a symmetrical matrix of order n x n, the element d in the matrixijRepresenting the distance between node i and node j. The present embodiment does not use the conventional euler distance, but uses the resistance value between two nodes to represent the electrical distance. A simple 4-node system is taken as an example to illustrate how the values of the elements in the matrix D are defined, as shown in fig. 1. From the connection relationship between the nodes and the given resistance value, the matrix D can be obtained as a 4 × 4 symmetric matrix. And the distance matrix D is subjected to clustering analysis to realize the partition of the power distribution network.
Figure BDA0002193362310000162
Because the power distribution network partitions only group nodes with close electrical distances into one group, the clustering result often has a problem, namely, the nodes in the groups are not interconnected in the system network, some isolated nodes which are not connected with any other nodes in the groups exist, and the isolated nodes need to be re-judged and divided into other groups according to the incidence matrix A because the network topology is determined.
The selection of the position of the compensation point by the capacity of the comprehensive treatment equipment also has great influence, and after the power distribution network is partitioned, an electric energy quality comprehensive treatment node needs to be selected in each area. In the embodiment, Stability Indexes (SI) are used, and by calculating SI values of nodes in each partition of the power distribution network, the node with the largest SI value in each partition is the location where the power quality comprehensive treatment device is installed. A simple two-node power distribution system is used to illustrate the calculation process of the SI value, as shown in fig. 2.
As can be seen from fig. 2, the current flowing through the line can be calculated as:
θ m and θ n are the angles of voltages Vm and Vn, respectively, the complex power being:
S-VI then
The expression cross multiplication according to the above two ims can result in:
VmVn∠(θm-θn)-Vn 2＝PnRm+QnXm-j(RmQn-PnXm)
assuming that the real part and the imaginary part are equal,the phase angle of the voltage can be ignored, and can be obtained
VmVn-Vn 2＝PnRm+QnXm
Figure BDA0002193362310000173
Substituting the above two equations can obtain:
Figure BDA0002193362310000174
to ensure that the root of the above formula is a solid root, it is necessary to satisfy
Figure BDA0002193362310000175
Therefore, the SI calculation method is
Figure BDA0002193362310000181
And calculating the SI index values of all nodes in different partitions of the power distribution network, wherein the node with the maximum SI value in a partition is a candidate node for installing the comprehensive treatment device in the partition.
1) Network loss reduction amount after implementation of electric energy quality comprehensive treatment scheme
In the process of quantitatively calculating the energy-saving potential of the power distribution network, firstly, the condition of improving the network loss after the electric energy quality comprehensive treatment scheme is implemented is considered, and the network loss reduction value after the electric energy quality comprehensive treatment scheme is implemented is used for representing:
f1＝Wtotal＝Ke(ΔPloss-peak×Tpeak+ΔPloss-medium×Tmedium+ΔPloss-light×Tlight)
in the formula, KeIs the cost of the network loss reduction; delta Ploss-peak、TpeakRespectively representing the network loss reduction (kW) before and after the implementation of the comprehensive control scheme of the power quality at the heavy load level and the duration (unit hour) of the heavy load level; delta Ploss-light、TlightRespectively representing the network loss reduction (kW) before and after the implementation of the comprehensive control scheme of the electric energy quality at the light load level and the duration (unit hour) of the light load level; delta Ploss-medium、TmediumThe network loss reduction (kW) before and after the implementation of the comprehensive management scheme for the electric energy quality at the normal load level and the duration (in unit hour) of the normal load level are respectively. The sum of the duration of different load levels is one year, Tpeak+Tlight+Tmedium8760 h. According to an additional loss model under the composite power quality disturbance (assuming that the distribution transformer under the disturbance of three composite power qualities of harmonic wave, three-phase imbalance and voltage deviationThe additional loss of the transformer and the distribution line is equal to the sum of the additional loss under each single power quality disturbance), and the network loss reduction amount before and after the implementation of the power quality comprehensive treatment scheme can be represented as follows:
Figure BDA0002193362310000191
wherein, HRIhThe h-th harmonic content; i is1Is the root mean square value of the fundamental current; rTThe equivalent resistance of the transformer winding is the fundamental wave; kTRepresenting the three-phase unbalance coefficient of the transformer; i isavIs the average value of the effective values of three-phase current, i.e. Iav＝(IA+IB+IC)/3，IA、IB、ICIs the effective value of each phase current; u shapeNThe rated voltage of the distribution transformer; poIs the no-load loss of the distribution transformer at rated voltage; delta is the voltage deviation, delta ═ U-UN)/UNX is 100%; γ is a coefficient related to the transformer voltage deviation: when the | delta | is less than 7%, the gamma is 2, when the | delta | is less than or equal to 7% and less than 10%, the gamma is 3.5, and when the | delta | is more than or equal to 10%, the gamma is 4; rLhIs equivalent resistance, K, under the h harmonic wave of the cableLRepresenting the three-phase unbalance factor, R, of the lineLIs the line fundamental wave resistance.
2) Cost of comprehensive treatment scheme for power quality
In the process of quantitatively calculating the energy-saving potential of the Power distribution network, the investment cost and the self running cost of a Multi-Objective Power Quality comprehensive treatment Device (MOPQCD) need to be considered.
Considering the investment cost of increasing the comprehensive treatment equipment for the power quality, the investment cost is shown as the following formula:
Figure BDA0002193362310000192
wherein K is a conversion factor; priceMOPQCDThe installation and maintenance cost of the comprehensive treatment device for the electric energy quality; m is the number of installed devices; priceQ is the price per unit capacity of the device, SMOPQCDiCompensation capacity at ith for installation;
because the installation cost of the electric energy quality comprehensive treatment equipment is one-time investment, conversion needs to be carried out according to the service life of the equipment, and the calculation formula of the conversion coefficient K is as follows:
Figure BDA0002193362310000201
in the formula, r is the equipment depreciation rate; n isMOPQCDThe service life of the device.
The self running cost of the multi-target electric energy quality comprehensive treatment device is related to power electronic devices and main components (as shown in a dotted frame in figure 3) used in the device, and the voltage-sharing resistance loss on the direct current side can be ignored.
The operation cost of the multi-target power quality comprehensive treatment device (taking a three-phase four-wire device as an example) is shown as follows:
f3＝4m(Psw+Pt+PD+Pshunt)
wherein, PswIs the switching loss, P, of MOPQCD using IGBTsw＝Fpwm*[Eon+Eoff]. Taking the Yingfei IGBT (FF300R12ME4) as an example, the switching frequency F is obtained according to the data manual of the IGBT of the modelpwmCalculated according to 10k, E is calculated when the IGBT working temperature is 125 DEG Con＝17mJ， Eoff＝37.5mJ，Psw＝545W。
PtIs the on-state loss of the IGBT, P is shown in FIG. 4t＝Ic*Vce. Taking the same IGBT as an example, when the working temperature is 125 ℃, and the current reaches 100A, VceThe voltage is about 1.2V, so Pt＝120W。
PDIs the diode loss of the IGBT with a tube voltage drop of 0.7, PD＝0.7*IC。PD＝70W。
Therefore, the model is FF300R12ME4 english flying IGBT, and when the switching frequency is 10KHz, the operating current is 100A, and the operating temperature is 125 ℃, the total heating power is 735W × 2 — 1470W.
In summary, the quantitative calculation of the Energy Saving potential (TES) of the power distribution network is shown as follows:
TES＝f1-f2-f3
considering a power distribution network planning and transformation scene, the quantitative calculation of the energy saving potential of the power distribution network needs to consider the investment cost of line new construction or transformation and transformer new construction or transformation besides considering the network loss reduction amount after the new power quality comprehensive treatment scheme is implemented after the power distribution network planning and transformation and the investment cost and the operation cost under the number of new comprehensive treatment devices. Therefore, the quantitative calculation of the energy-saving potential of the power distribution network in the power distribution network planning and transformation scene is shown as the following formula:
Figure BDA0002193362310000211
wherein priceLineThe unit price (ten thousand yuan/kilometer) of a line to be reformed or newly built is planned; pricetypeRepresents the construction cost or the line cost (ten thousand yuan/kilometer) additionally generated by replacing or modifying the line due to different line types;
Figure BDA0002193362310000212
represents the cost (ten thousand yuan) generated by the change of the distribution transformer; c is the number of transformers to be rebuilt or replaced, and Length represents the Length (in kilometers) of the rebuilt or replaced conductors. The parameter value settings related to the investments are shown in table 1:
TABLE 1 investment-related parameters
Figure BDA0002193362310000213
2) Energy-saving efficiency-increasing optimal scheme for comprehensive treatment of power quality
Objective function
minF1＝Ke(ΔPloss-peak×Tpeak+ΔPloss-medium×Tmedium+ΔPloss-light×Tlight)
From the above formula, the optimal scheme for comprehensive control of power quality, energy saving and efficiency improvement is a multi-objective optimization problem with two objective functions, the first objective function is the loss reduction effect after the implementation of the scheme, and the second objective function is the economy of the scheme (assuming that the running costs of the comprehensive control equipment with different capacities are basically consistent).
Constraint conditions
The energy-saving and efficiency-increasing optimal scheme has the constraint of equality and inequality conditions. The equality constraint, i.e. the tidal flow constraint, is given by:
Figure BDA0002193362310000222
in the formula, PiRepresenting the injected active power of the node i; qiRepresents the injected reactive power of node i; b isij、GijRespectively representing conductance susceptances between nodes i and j; n represents the total number of nodes;
inequality constraint condition
Uimin≤Ui≤Uimax,i∈Nb
Figure BDA0002193362310000223
0≤SMOPQCDi≤SMOPQCDimax,i∈m
THDi≤THDmax
In the formula, the constraint condition in the above formula is mainly the safe and stable operation of the power distribution networkThe operating range specified by the row; wherein N represents the number of nodes of the power distribution network; uimin and Uimax are respectively the upper limit and the lower limit of the node voltage, and the lower limit and the upper limit (per-unit value) are respectively in the interval of 0.9 and 1.1; simin、 SiminUpper and lower limits of line flow (thermal limit constraints), respectively; sMOPQCDimaxRespectively representing the upper limit of the capacity of the electric energy quality comprehensive treatment device, 10000 kVA; THDmax5 percent according to the national standard.
In order to verify the feasibility of the optimal scheme of energy conservation and efficiency improvement of the power quality of the power distribution network, simulation analysis is carried out on the IEEE-33 node power distribution network. The topology structure of the IEEE-33 node power distribution network is shown in figure 5, a node 1 is a balance node, and the reference voltage is 10.5 kV. As in tables 2 to 4.
TABLE 2 IEEE-33 node network parameters
Figure BDA0002193362310000231
TABLE 3 IEEE-33 node load level and duration thereof
Figure BDA0002193362310000232
TABLE 4 energy-saving efficiency-increasing optimized protocol parameters
Figure BDA0002193362310000233
Figure BDA0002193362310000241
The IEEE-33 node power distribution network is partitioned and subjected to comprehensive treatment optimal distribution analysis, the power distribution network is divided into 2 partitions, 3 partitions and 4 partitions, and corresponding partition results and optimal distribution results (in bold) are shown in table 5.
Then, taking three partitions as an example, an energy-saving and efficiency-increasing optimal scheme is solved by using an optimization method of a user preference information-oriented consensus multi-target particle group, and the calculation results are shown in table 6:
TABLE 6 energy-saving and efficiency-increasing optimization scheme calculation results
Figure BDA0002193362310000243
Preferably, the embodiment provides a power quality energy-saving improvement technology optimization principle of the power distribution network from the perspective of global optimization and hierarchical control. Aiming at reducing the system network loss to the maximum extent, providing an optimal distribution method for comprehensive treatment of electric energy quality based on a clustering technology, and realizing distribution network partition and distribution considering the electrical distance; and the capacity configuration method of the electric energy quality comprehensive treatment device takes the loss reduction effect and the investment cost after the electric energy quality comprehensive treatment scheme is implemented as a target function, and improves the energy-saving and loss reduction effect of the power distribution network.
The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be covered by the present invention.

Claims (8)

1. A power quality energy-saving efficiency-increasing scheme optimization method for a power distribution network is characterized by comprising the following steps: the method comprises the following steps:
step S1: dividing the network into each sub-region by adopting a Kmeans clustering method, and determining the optimal distribution point of the electric energy quality comprehensive treatment device according to the stability index in each sub-region;
step S2: two goals of comprehensive treatment of power quality are considered: the network loss reduction amount after the power quality comprehensive treatment device is installed, the investment cost and the self running cost of the multi-target power quality comprehensive treatment device, and the energy-saving potential after the power distribution network quality comprehensive treatment are quantitatively calculated;
the quantitative calculation formula of the energy-saving potential of the power distribution network is as follows: TES is f1-f2-f3Wherein f is1Representing a network loss reduction value after the implementation of the power quality comprehensive treatment scheme; f. of2Comprehensive treatment for increasing electric energy qualityInvestment cost of the plant; f. of3The operation cost of the multi-target power quality comprehensive treatment device is represented;
step S3: considering a power distribution network planning and transformation scene, namely considering investment costs of line new construction or transformation and transformer new construction or transformation, and carrying out quantitative calculation on the energy-saving potential of the power distribution network in the power distribution network planning and transformation scene;
step S4: establishing a loss reduction target function F1And an objective function F of the investment costs2And optimizing to obtain the optimal scheme for controlling the power quality.
2. The method for optimizing the power quality energy-saving efficiency improvement scheme of the power distribution network according to claim 1, characterized by comprising the following steps: the step S1 specifically includes the following steps:
step S11: clustering and partitioning a distance matrix constructed by a topological structure and parameters of the power distribution network by using a Kmeans clustering method, and dividing the whole power distribution network into a plurality of sub-regions;
firstly, a node association matrix A is obtained from a network topology structure of the power distribution network, and if the number of nodes of the power distribution network is n, the matrix A is (a)ij)n×nIs a symmetric matrix of order n × n, and each element in the matrix a is defined as follows:
Figure FDA0002193362300000021
then, an incidence matrix A obtained by combining the network parameters of the power distribution network is provided to calculate an electrical distance matrix D between each node, wherein the matrix D is (D)ij)n×nIs a symmetric matrix of n x n order, the element d in the matrixijRepresents the distance between node i and node j; the values of the elements in the matrix D in a 4-node system are defined as follows:
partitioning the power distribution network by clustering and analyzing the distance matrix D;
step S12: and selecting a load center in each subarea as a mounting point of the electric energy quality comprehensive treatment device so as to avoid uneven distribution of electric energy quality comprehensive treatment positions and overlapping treatment ranges.
3. The method for optimizing the power quality energy-saving efficiency improvement scheme of the power distribution network according to claim 2, characterized by comprising the following steps: the step S12 specifically includes the following steps: the stability index numerical value of each node in each partition of the power distribution network is calculated, and the node with the maximum stability index numerical value in each partition is the installation position of the comprehensive control device for the power quality;
the specific process for calculating the stability index value of the power distribution network comprises the following steps:
the current flowing through the distribution network line is:
Figure FDA0002193362300000023
θmand thetanAre voltages Vm and V, respectivelynThe complex power is: s is VI, then
Figure FDA0002193362300000024
According to the two above ImThe expressions of (a) are cross multiplied to obtain:
Figure FDA0002193362300000025
assuming that the real part and the imaginary part are equal,the phase angle of the voltage can be ignored to obtain
Figure FDA0002193362300000033
Substituting the above two formulas to obtain:
Figure FDA0002193362300000034
to ensure that the root of the above formula is a solid root, it is necessary to satisfy
Figure FDA0002193362300000035
Therefore, the stability index is calculated by the formula:
Figure FDA0002193362300000036
and calculating the stability index values of all nodes in different partitions of the power distribution network, wherein the node with the maximum stability index value in a partition is a candidate node for installing the comprehensive control device for the power quality in the partition.
4. The method for optimizing the power quality energy-saving efficiency improvement scheme of the power distribution network according to claim 1, characterized by comprising the following steps: the specific calculation process of the network loss reduction amount after the power quality comprehensive treatment device is installed in the step S2 is as follows:
after the power quality comprehensive treatment device is installed, namely the network loss reduction value after the power quality comprehensive treatment scheme is implemented is expressed as follows:
f1＝Wtotal＝Ke(ΔPloss-peak×Tpeak+ΔPloss-medium×Tmedium+ΔPloss-light×Tlight)
in the formula, KeIs the cost of the network loss reduction; delta Ploss-peak、TpeakRespectively representing the unit kW of network loss reduction and the unit hour of duration of the heavy load level before and after the implementation of the comprehensive control scheme for the power quality at the heavy load level; delta Ploss-light、TlightRespectively a network loss reduction unit kW and a duration unit hour of the light load level before and after the implementation of the comprehensive control scheme of the power quality at the light load level；ΔPloss-medium、TmediumNetwork loss reduction unit kW and normal load level duration unit hour before and after the implementation of the power quality comprehensive treatment scheme at the normal load level are respectively set; the sum of the duration of different load levels is one year, Tpeak+Tlight+Tmedium＝8760h；
Assuming that the additional loss of the distribution transformer and the distribution line is equal to the sum of the additional loss under the disturbance of three composite power qualities of harmonic wave, three-phase imbalance and voltage deviation, the network loss reduction before and after the implementation of the comprehensive power quality control scheme is represented as follows:
Figure FDA0002193362300000041
ΔPloss＝ΔPloss-peak+ΔPloss-medium+ΔPloss-light
wherein, Δ PTransformAnd Δ PLineLosses of the transformer and the line, respectively; HRIhThe h-th harmonic content; i is1Is the root mean square value of the fundamental current; rTThe equivalent resistance of the transformer winding is the fundamental wave; kTRepresenting the three-phase unbalance coefficient of the transformer; i isavIs the average value of the effective values of three-phase current, i.e. Iav＝(IA+IB+IC)/3，IA、IB、ICIs the effective value of each phase current; u shapeNThe rated voltage of the distribution transformer; poIs the no-load loss of the distribution transformer at rated voltage; delta is the voltage deviation, delta ═ U-UN)/UNX is 100%; γ is a coefficient related to the transformer voltage deviation: when the | delta | is less than 7%, the gamma is 2, when the | delta | is less than or equal to 7% and less than 10%, the gamma is 3.5, and when the | delta | is more than or equal to 10%, the gamma is 4; rLhIs equivalent resistance, K, under the h harmonic wave of the cableLRepresenting the three-phase unbalance factor of the line, RLIs the line fundamental wave resistance.
5. The method for optimizing the power quality energy-saving efficiency improvement scheme of the power distribution network according to claim 1, characterized by comprising the following steps: the specific calculation process of the investment cost of the multi-target power quality comprehensive treatment device in the step S2 is as follows:
considering the investment cost of increasing the comprehensive treatment device for the power quality, the investment cost is shown as the following formula:
Figure FDA0002193362300000051
wherein K is a conversion factor; priceMOPQCDThe installation and maintenance cost of the comprehensive treatment device for the electric energy quality; m is the number of installed devices; priceSIs the price per unit capacity of the device, SMOPQCDiCompensation capacity at ith for installation;
because the installation cost of the electric energy quality comprehensive treatment equipment is one-time investment, conversion needs to be carried out according to the service life of the equipment, and the calculation formula of the conversion coefficient K is as follows:
Figure FDA0002193362300000052
in the formula, r is the equipment depreciation rate; n isMOPQCDThe service life of the device.
6. The method for optimizing the power quality energy-saving efficiency improvement scheme of the power distribution network according to claim 1, characterized by comprising the following steps: the specific calculation process of the self operation cost of the multi-target power quality comprehensive treatment device in the step S2 is as follows:
the self running cost of the multi-target electric energy quality comprehensive treatment device is related to power electronic devices and main components used in the device, and the loss of the voltage-sharing resistor on the direct current side is ignored;
the operation cost of the three-phase four-wire system multi-target electric energy quality comprehensive treatment device is shown as the following formula:
f3＝4m(Psw+Pt+PD+Pshunt)
wherein, PswIs a multi-target electric energy quality comprehensive treatment deviceIn which switching losses, P, of the IGBT are usedsw＝Fpwm*[Eon+Eoff](ii) a Wherein, FpwmIndicating the switching frequency, Eon+EoffRepresents the heat when the IGBT is turned on or off; ptIs the on-state loss, P, of the IGBTt＝Ic*Vce(ii) a Wherein, VceIs the voltage between the collector and emitter of the tube, IcIs the collector current; pDIs the diode loss of the IGBT with a tube voltage drop of 0.7, PD＝0.7*IC。
7. The method for optimizing the power quality energy-saving efficiency improvement scheme of the power distribution network according to claim 1, characterized by comprising the following steps: the specific formula for quantitatively calculating the energy saving potential of the power distribution network in the power distribution network planning and transformation scene in the step S3 is as follows:
Figure FDA0002193362300000061
wherein priceLineShowing the unit price of a line to be reformed or newly built is planned to be ten thousand yuan/kilometer; pricetypeThe unit of construction cost or line cost additionally generated due to different line types for replacing or reconstructing the line is ten thousand yuan/kilometer;representing the unit of ten thousand yuan of expense generated by the replacement of the distribution transformer; c is the number of transformers to be modified or replaced; length means the unit kilometer of the modified or replaced wire Length.
8. The method for optimizing the power quality energy-saving efficiency improvement scheme of the power distribution network according to claim 1, characterized by comprising the following steps: the step S4 specifically includes the following steps:
the objective function is specifically:
Figure FDA0002193362300000063
constraint conditions are as follows: the equality constraint, i.e., the power flow constraint, is shown as follows:
Figure FDA0002193362300000071
in the formula, PiRepresenting the injected active power of the node i; qiRepresents the injected reactive power at node i; b isij、GijRespectively representing conductance susceptances between nodes i and j; n represents the total number of nodes;
inequality constraint conditions:
Uimin≤Ui≤Uimax,i∈Nb
Figure FDA0002193362300000072
0≤SMOPQCDi≤SMOPQCDimax,i∈m
THDi≤THDmax
wherein N represents the number of nodes of the power distribution network; u shapeimin、UimaxThe upper limit and the lower limit of the node voltage are respectively within the interval of 0.9 and 1.1; simin、SiminRespectively an upper limit and a lower limit of the line power flow; sMOPQCDimaxThe upper limit of the capacity of the electric energy quality comprehensive treatment device is represented, and 10000kVA is used; THDmax5 percent according to the national standard.
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