CN110880760A - Low-voltage distribution network line loss and reactive compensation collaborative optimization method - Google Patents
Low-voltage distribution network line loss and reactive compensation collaborative optimization method Download PDFInfo
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Classifications
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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
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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
- H02J3/04—Circuit arrangements for ac mains or ac distribution networks for connecting networks of the same frequency but supplied from different sources
- H02J3/06—Controlling transfer of power between connected networks; Controlling sharing of load between connected networks
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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
- H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
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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
- H02J3/26—Arrangements for eliminating or reducing asymmetry in polyphase 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
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
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- 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
- Y02E40/30—Reactive power compensation
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- 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 provides a line loss and reactive compensation collaborative optimization method for a low-voltage distribution network. Step S1 is adopted: the method comprises the steps that user voltage and current data provided by a smart electric meter at a low-voltage side of a transformer area are utilized, the influence of grid connection of a distributed power supply is considered, and accurate measurement data are obtained; step S2: the method comprises the following steps of taking a forward-backward substitution algorithm as a main body, locally correcting by adopting a Newton method, a sensitivity method and a loop method, and establishing an accurate three-phase load flow calculation model; step S3: accurately analyzing and calculating theoretical line loss by using data and line parameters after load flow calculation; step S4: and establishing a reactive compensation optimization model of the power distribution network by taking the minimum line loss as an optimization aim and the economy of reactive compensation as a constraint condition, so as to realize the cooperative optimization of the line loss and the reactive compensation. A line loss and reactive compensation collaborative optimization method based on multi-dimensional data fusion realizes intelligent management and economical and reliable operation of a power distribution area. The line loss and reactive compensation collaborative optimization method based on multi-dimensional data fusion is suitable for application.
Description
Technical Field
The invention relates to intelligent self-management, economical and reliable operation of a power distribution station area. In particular to a line loss and reactive compensation collaborative optimization method based on multi-dimensional data fusion.
Background
The power distribution network is responsible for directly transmitting the electric energy after voltage reduction to users and using the electric energy in the power system, and the power distribution network becomes the final link of power production, transmission and consumption and directly influences the power supply reliability and the power supply quality of the users. In recent years, with the rapid advance of science and technology, economy and the like in China, the related technology of the power distribution network is rapidly promoted and developed. But compared with a transmission network and a high-voltage distribution network, the automation degree of the low-voltage distribution network in China is still not ideal.
Along with the improvement of the requirement of the quality of life of people, the precision degree of the equipment and the electric appliances of the enterprise units is increased, and the requirements for the distribution quality and the safety and the stability of the power distribution network of a power supply enterprise are further met. The national grid company provides in 2014 that the power supply reliability in important areas of large and medium-sized towns, namely the online rate of the electric energy of a power distribution network is more than 99.990%, and the annual power failure time of each average power consumer is less than 0.85 hour and is a qualified standard; the reliable electric energy online rate of rural and three-wire cities is greater than 99.954%, and the average annual power failure time of each power consumer is less than 4 hours, which is the qualified standard. When the demand for power supply reliability is increased, the scale of the power distribution network is gradually enlarged, the number of power distribution network lines is greatly increased, and the difficulty of operating modes and fault handling modes of the power distribution network lines is continuously increased due to diversification of line structures, operation modes and types. Meanwhile, with the continuous improvement of lean management requirements of a low-voltage distribution network, functions of a distribution substation are diversified and intelligentized, accessed information and equipment are multiplied, more than 10 types of distribution transformer state monitoring, reactive compensation, leakage protection switches, electric energy meters, distributed power sources, electric automobile charging piles and the like are involved, and a lot of discrete equipment and systems are installed in the traditional method. For example, a voltage quality monitoring system, a reactive compensation system, a distribution transformer monitoring system, an electricity consumption information acquisition system and the like. However, compared with the requirements of the smart grid, the traditional platform area construction mode needs to be changed, and economic applicability, integration and intellectualization are the future direction.
Disclosure of Invention
The invention provides a line loss and reactive compensation collaborative optimization method for a low-voltage distribution network, aiming at solving the problems of separated equipment, high cost and isolated data analysis of the traditional distribution network. According to the method, the line loss and reactive compensation collaborative optimization method based on the multidimensional data fusion is adopted, the intelligent management and economical and reliable operation of the power distribution station are realized, and the technical problems of the traditional power distribution station that the equipment is separated, the cost is high and the data analysis is isolated are solved.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a low-voltage distribution network line loss and reactive compensation collaborative optimization method comprises the following steps:
step S1: forming a more accurate measurement data set by using user voltage and current data provided by the intelligent electric meter at the low-voltage side of the power distribution area and the grid-connected related data of the distributed power supply;
step S2; the forward-backward substitution method is taken as a main body, local Newton method, sensitivity method and loop method are adopted for correction, three-phase power flow analysis is carried out, and problems of PV type nodes, PQ type nodes and the like can be solved;
step S3: accurately analyzing and calculating theoretical line loss by using data and line parameters after load flow calculation;
step S4: and establishing a reactive compensation optimization model of the power distribution network by taking the minimum line loss as an optimization aim and the economy of reactive compensation as a constraint condition, so as to realize the cooperative optimization of the line loss and the reactive compensation.
Further: in the step S1, measurement data are acquired, the range data are acquired mainly by acquiring real-time voltage and current data of a user through a smart meter at a low-voltage side of the distribution area, and the data of the smart meter are collected and processed in a unified manner and meanwhile, relevant data after the distributed power supply is connected to the grid are acquired, so that a data basis is provided for collaborative optimization.
And further: the forward-pushing substitution calculation method in the step S2 has the following specific implementation principle:
the initial end voltage and the end load of the power distribution network are known, and the feeder line is used as a basic calculation unit. Firstly, assuming that the voltage of the whole network is rated voltage, calculating section by section from the tail end to the initial end according to the load power, only calculating the power loss in each element without calculating the node voltage, solving the current and the power loss on each branch circuit, and obtaining the power of the initial end according to the current and the power loss, which is a back-substitution process; then, according to the given initial end voltage and the obtained initial end power, the voltage drop is calculated section by section from the initial end to the tail end, and the voltage of each node is obtained, which is a forward process; repeating the above processes until the power deviation of each node meets the allowable condition;
the three-phase power flow analysis method of the power distribution network comprising the distributed power supply comprises the following steps:
step 1, introducing 380V low-voltage distribution network real-time measurement data into load flow calculation, and improving the accuracy of the load flow calculation;
step 2, initializing node voltage amplitude values and phase angle values, taking a forward substitution method as a main body, and calculating to obtain the voltage and amplitude values of each node;
in the step, a forward-backward substitution method is adopted to calculate the three-phase load flow by utilizing user, line and topological data; for each sampling moment, iteratively calculating the current of each branch upwards from a leaf node (namely a user node), accumulating the phase current of a downstream branch directly connected with the branch to obtain a certain phase current of each branch, and repeating the steps until a root node is calculated; then gradually calculating the voltage of each branch tail end node from the root node downwards in each iteration, wherein the voltage of each branch tail end node is obtained by calculating the voltage of the branch head end node, the current of the branch and the impedance of the branch, and so on;
step 3, comprehensively considering the grid-connected factors of the distributed energy sources, selecting nodes containing the distributed power sources, and carrying out symmetrical component analysis;
step 4, substituting the sequence components into a distributed power control equation to solve, and judging whether the PV node is out of bounds in a reactive power mode;
step 5, converting the sequence component current into three-phase current, and calculating a circuit current injection value of a splitting point by a circuit analysis method; the loop method is a solution method which takes a group of independent loop currents of a planar circuit or a non-planar circuit as circuit variables and lists an equation expressing related branch voltage by using the loop currents for the independent loop by using KVL; the loop current is an imaginary current flowing along the loop boundary; usually, the basic loop is selected as an independent loop, and the loop current is the corresponding branch current;
step 6, judging whether the iterative errors of the current and the voltage are smaller than a threshold value, if so, obtaining an ideal load flow calculation result, and finishing the calculation; and if the threshold value is exceeded, returning to the step 2, recalculating the node voltage and the amplitude, and repeating the subsequent steps.
And further: based on the load flow calculation, the step S3 is to analyze and calculate the theoretical line loss as follows:
step 1: initializing, namely, arranging user voltage and current data, user power factors and affiliated phases, line impedance parameters, network topology information and the like of each sampling moment measured by the intelligent electric meter into a data set which can be processed;
step 2: performing three-phase load flow calculation by using user, line and topological data through a forward-backward substitution method, calculating the voltage and current values of each section branch at each sampling moment, and initializing t =1 at the moment;
and step 3: and performing line loss calculation. Firstly, calculating the loss generated by the current flowing on a zero line due to the unbalance of three-phase current in a three-phase four-wire system line, namely the loss of the zero line, wherein the current on each section of the zero line adopts a method of three-phase current vector superposition calculation; then, calculating the sum of the line losses of each phase, namely the loss of the three-phase power supply line; and finally, calculating the line loss and the ammeter loss of the user section, namely the user loss. For each sampling moment, calculating the total loss and the line loss rate by using data and line parameters after load flow calculation, wherein t = t + 1;
and 4, step 4: comparing the time value T with the total time number T of the ammeter sampling in the investigation period, outputting the proportion of various types of loss in the total loss when T is greater than T, visually reflecting the influence degree of various types of loss in a chart form, and storing the line loss information at the time in a data file to finish the line loss calculation; and when T is less than T, resetting T =1, and returning to the step 2 to perform power flow calculation until an ideal line loss result is obtained.
And further: the step S4 specifically implements the cooperative optimization of the line loss and the reactive compensation as follows:
step 1: first, an objective function with minimal line loss is established:
in the formula: nl is the total number of branches of the system;
is the conductance of branch i-j;
、
voltages of nodes i and j, respectively;
、
phase angles of nodes i and j are respectively;
step 2: and establishing a constraint condition. The inequality constraints of the reactive power optimization of the power distribution network comprise control variable constraints and state variable constraints, the control variable constraints comprise reactive compensation capacity constraints and transformer tap constraints, and the control variable constraints are discrete variables. The state variable constraints include voltage effective value size constraints for each node. Furthermore the distributed power supply has access capacity constraints;
and step 3: and (4) considering the economy of reactive compensation, and establishing an optimization model. The number of installation points of the reactive power compensation device in the power distribution network is not too large, and the limit of compensation capacity of each installation point is considered when the distributed reactive power optimization configuration calculation is carried out, and the limit of the total number of the installation points of the reactive power compensation device in the whole transformer area is considered. When the reactive power optimization model adopts a dispersion compensation mode, all load nodes in the transformer area can be selected as candidate installation nodes. When the compensation capacity of the candidate point is equal to zero, the node does not need to be provided with a reactive compensation device; when the compensation capacity of the candidate point is larger than zero, the reactive compensation device needs to be installed on the node. In the optimization model, all load nodes are used as candidate installation nodes, the installation position of the reactive compensation device is obtained by solving the optimization model, and the subjectivity of installation point selection of the reactive compensation device can be avoided;
and 4, step 4: solving the objective function by adopting a genetic algorithm, generating a group of initial power flow solutions in a current system environment, evaluating the quality degree of individuals in a population by the limitation of the constraint conditions and the calculation of the objective function and the fitness function, namely carrying out primary power flow calculation, eliminating the individuals with lower fitness values and the excellent individuals with higher genetic fitness values, calculating primary system power flow distribution for each evaluation to obtain information contents such as system active network loss, node voltage violation and the like, punishing the violation items by adopting a penalty function, and continuously carrying out genetic operations such as selection, crossing, variation and the like so as to obtain the optimal solution.
The positive effect is that the invention adopts the step S1: the method comprises the steps that user voltage and current data provided by a smart electric meter at a low-voltage side of a transformer area are utilized, the influence of grid connection of a distributed power supply is considered, and accurate measurement data are obtained; step S2: the method comprises the following steps of taking a forward-backward substitution algorithm as a main body, locally correcting by adopting a Newton method, a sensitivity method and a loop method, and establishing an accurate three-phase load flow calculation model; step S3: accurately analyzing and calculating theoretical line loss by using data and line parameters after load flow calculation; step S4: and establishing a reactive compensation optimization model of the power distribution network by taking the minimum line loss as an optimization aim and the economy of reactive compensation as a constraint condition, so as to realize the cooperative optimization of the line loss and the reactive compensation. Aiming at the construction requirements of intelligentization telephone, informatization, automation and interaction of the distribution transformer area, the invention provides a line loss and reactive power compensation collaborative optimization method based on multi-dimensional data fusion on the basis of the function integration of the distribution transformer area, and realizes the intelligentization management and the economic and reliable operation of the distribution transformer area. The line loss and reactive compensation collaborative optimization method based on multi-dimensional data fusion is suitable for application.
Detailed Description
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
A low-voltage distribution network line loss and reactive compensation collaborative optimization method comprises the following steps:
step S1: forming a more accurate measurement data set by using user voltage and current data provided by the intelligent electric meter at the low-voltage side of the power distribution area and the grid-connected related data of the distributed power supply;
step S2; the forward-backward substitution method is taken as a main body, local Newton method, sensitivity method and loop method are adopted for correction, three-phase power flow analysis is carried out, and the problems of PV type nodes and PQ type nodes can be solved;
step S3: accurately analyzing and calculating theoretical line loss by using data and line parameters after load flow calculation;
step S4: and establishing a reactive compensation optimization model of the power distribution network by taking the minimum line loss as an optimization aim and the economy of reactive compensation as a constraint condition, so as to realize the cooperative optimization of the line loss and the reactive compensation.
In the step S1, measurement data are acquired, the range data are acquired mainly by acquiring real-time voltage and current data of a user through a smart meter at a low-voltage side of the distribution area, and the data of the smart meter are collected and processed in a unified manner and meanwhile, relevant data after the distributed power supply is connected to the grid are acquired, so that a data basis is provided for collaborative optimization.
The forward-pushing substitution calculation method in the step S2 has the following specific implementation principle:
the initial end voltage and the end load of the power distribution network are known, and the feeder line is used as a basic calculation unit. Firstly, assuming that the voltage of the whole network is rated voltage, calculating section by section from the tail end to the initial end according to the load power, only calculating the power loss in each element without calculating the node voltage, solving the current and the power loss on each branch circuit, and obtaining the power of the initial end according to the current and the power loss, which is a back-substitution process; then, according to the given initial end voltage and the obtained initial end power, the voltage drop is calculated section by section from the initial end to the tail end, and the voltage of each node is obtained, which is a forward process; repeating the above processes until the power deviation of each node meets the allowable condition;
the three-phase power flow analysis method of the power distribution network comprising the distributed power supply comprises the following steps:
step 1, introducing 380V low-voltage distribution network real-time measurement data into load flow calculation, and improving the accuracy of the load flow calculation;
step 2, initializing node voltage amplitude values and phase angle values, taking a forward substitution method as a main body, and calculating to obtain the voltage and amplitude values of each node;
in the step, a forward-backward substitution method is adopted to calculate the three-phase load flow by utilizing user, line and topological data; for each sampling moment, iteratively calculating the current of each branch upwards from a leaf node (namely a user node), accumulating the phase current of a downstream branch directly connected with the branch to obtain a certain phase current of each branch, and repeating the steps until a root node is calculated; then gradually calculating the voltage of each branch tail end node from the root node downwards in each iteration, wherein the voltage of each branch tail end node is obtained by calculating the voltage of the branch head end node, the current of the branch and the impedance of the branch, and so on;
step 3, comprehensively considering the grid-connected factors of the distributed energy sources, selecting nodes containing the distributed power sources, and carrying out symmetrical component analysis;
step 4, substituting the sequence components into a distributed power control equation to solve, and judging whether the PV node is out of bounds in a reactive power mode;
step 5, converting the sequence component current into three-phase current, and calculating a circuit current injection value of a splitting point by a circuit analysis method; the loop method is a solution method which takes a group of independent loop currents of a planar circuit or a non-planar circuit as circuit variables and lists an equation expressing related branch voltage by using the loop currents for the independent loop by using KVL; the loop current is an imaginary current flowing along the loop boundary; usually, the basic loop is selected as an independent loop, and the loop current is the corresponding branch current;
step 6, judging whether the iterative errors of the current and the voltage are smaller than a threshold value, if so, obtaining an ideal load flow calculation result, and finishing the calculation; and if the threshold value is exceeded, returning to the step 2, recalculating the node voltage and the amplitude, and repeating the subsequent steps.
Based on the load flow calculation, the step S3 is to analyze and calculate the theoretical line loss as follows:
step 1: initializing, namely, arranging user voltage and current data, user power factors and affiliated phases, line impedance parameters, network topology information and the like of each sampling moment measured by the intelligent electric meter into a data set which can be processed;
step 2: performing three-phase load flow calculation by using user, line and topological data through a forward-backward substitution method, calculating the voltage and current values of each section branch at each sampling moment, and initializing t =1 at the moment;
and step 3: and performing line loss calculation. Firstly, calculating the loss generated by the current flowing on a zero line due to the unbalance of three-phase current in a three-phase four-wire system line, namely the loss of the zero line, wherein the current on each section of the zero line adopts a method of three-phase current vector superposition calculation; then, calculating the sum of the line losses of each phase, namely the loss of the three-phase power supply line; and finally, calculating the line loss and the ammeter loss of the user section, namely the user loss. For each sampling moment, calculating the total loss and the line loss rate by using data and line parameters after load flow calculation, wherein t = t + 1;
and 4, step 4: comparing the time value T with the total time number T of the ammeter sampling in the investigation period, outputting the proportion of various types of loss in the total loss when T is greater than T, visually reflecting the influence degree of various types of loss in a chart form, and storing the line loss information at the time in a data file to finish the line loss calculation; and when T is less than T, resetting T =1, and returning to the step 2 to perform power flow calculation until an ideal line loss result is obtained.
The step S4 specifically implements the cooperative optimization of the line loss and the reactive compensation as follows:
step 1: first, an objective function with minimal line loss is established:
in the formula: nl is the total number of branches of the system;
is the conductance of branch i-j;
、
voltages of nodes i and j, respectively;
、
phase angles of nodes i and j are respectively;
step 2: and establishing a constraint condition. The inequality constraints of the reactive power optimization of the power distribution network comprise control variable constraints and state variable constraints, the control variable constraints comprise reactive compensation capacity constraints and transformer tap constraints, and the control variable constraints are discrete variables. The state variable constraints include voltage effective value size constraints for each node. Furthermore the distributed power supply has access capacity constraints;
and step 3: and (4) considering the economy of reactive compensation, and establishing an optimization model. The number of installation points of the reactive power compensation device in the power distribution network is not too large, and the limit of compensation capacity of each installation point is considered when the distributed reactive power optimization configuration calculation is carried out, and the limit of the total number of the installation points of the reactive power compensation device in the whole transformer area is considered. When the reactive power optimization model adopts a dispersion compensation mode, all load nodes in the transformer area can be selected as candidate installation nodes. When the compensation capacity of the candidate point is equal to zero, the node does not need to be provided with a reactive compensation device; when the compensation capacity of the candidate point is larger than zero, the reactive compensation device needs to be installed on the node. In the optimization model, all load nodes are used as candidate installation nodes, the installation position of the reactive compensation device is obtained by solving the optimization model, and the subjectivity of installation point selection of the reactive compensation device can be avoided;
and 4, step 4: solving the objective function by adopting a genetic algorithm, generating a group of initial power flow solutions in a current system environment, evaluating the quality degree of individuals in a population by the limitation of the constraint conditions and the calculation of the objective function and the fitness function, namely carrying out primary power flow calculation, eliminating the individuals with lower fitness values and the excellent individuals with higher genetic fitness values, calculating primary system power flow distribution for each evaluation to obtain information contents such as system active network loss, node voltage violation and the like, punishing the violation items by adopting a penalty function, and continuously carrying out genetic operations such as selection, crossing, variation and the like so as to obtain the optimal solution.
The invention has the advantages that:
1. aiming at the construction requirements of intelligentization telephone, informatization, automation and interaction of the distribution transformer area, the invention provides a line loss and reactive power compensation collaborative optimization method based on multi-dimensional data fusion on the basis of the function integration of the distribution transformer area, and realizes the intelligentization management and the economic and reliable operation of the distribution transformer area.
2. Compared with the traditional line loss calculation method, the new method is improved from the month/representative day to the density of the measurement interval set by the intelligent electric meter on the acquired data source, and is more accurate on the calculation method.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments or portions thereof without departing from the spirit and scope of the invention.
Claims (5)
1. A low-voltage distribution network line loss and reactive compensation collaborative optimization method is characterized by comprising the following steps: the method comprises the following steps:
step S1: forming a more accurate measurement data set by using user voltage and current data provided by the intelligent electric meter at the low-voltage side of the power distribution area and the grid-connected related data of the distributed power supply;
step S2; the forward-backward substitution method is taken as a main body, local Newton method, sensitivity method and loop method are adopted for correction, three-phase power flow analysis is carried out, and the problems of PV type nodes and PQ type nodes can be solved;
step S3: accurately analyzing and calculating theoretical line loss by using data and line parameters after load flow calculation;
step S4: and establishing a reactive compensation optimization model of the power distribution network by taking the minimum line loss as an optimization aim and the economy of reactive compensation as a constraint condition, so as to realize the cooperative optimization of the line loss and the reactive compensation.
2. The line loss and reactive compensation collaborative optimization method for the low-voltage distribution network according to claim 1, characterized in that: in the step S1, measurement data are acquired, the range data are acquired mainly by acquiring real-time voltage and current data of a user through a smart meter at a low-voltage side of the distribution area, and the data of the smart meter are collected and processed in a unified manner and meanwhile, relevant data after the distributed power supply is connected to the grid are acquired, so that a data basis is provided for collaborative optimization.
3. The line loss and reactive compensation collaborative optimization method for the low-voltage distribution network according to claim 1, characterized in that: the forward-pushing substitution calculation method in the step S2 has the following specific implementation principle:
the initial end voltage and the terminal end load of the known power distribution network take a feeder line as a basic calculation unit;
firstly, assuming that the voltage of the whole network is rated voltage, calculating section by section from the tail end to the initial end according to the load power, only calculating the power loss in each element without calculating the node voltage, solving the current and the power loss on each branch circuit, and obtaining the power of the initial end according to the current and the power loss, which is a back-substitution process; then, according to the given initial end voltage and the obtained initial end power, the voltage drop is calculated section by section from the initial end to the tail end, and the voltage of each node is obtained, which is a forward process; repeating the above processes until the power deviation of each node meets the allowable condition;
the three-phase power flow analysis method of the power distribution network comprising the distributed power supply comprises the following steps:
step 1, introducing 380V low-voltage distribution network real-time measurement data into load flow calculation, and improving the accuracy of the load flow calculation;
step 2, initializing node voltage amplitude values and phase angle values, taking a forward substitution method as a main body, and calculating to obtain the voltage and amplitude values of each node;
in the step, a forward-backward substitution method is adopted to calculate the three-phase load flow by utilizing user, line and topological data; for each sampling moment, iteratively calculating the current of each branch upwards from a leaf node (namely a user node), accumulating the phase current of a downstream branch directly connected with the branch to obtain a certain phase current of each branch, and repeating the steps until a root node is calculated; then gradually calculating the voltage of each branch tail end node from the root node downwards in each iteration, wherein the voltage of each branch tail end node is obtained by calculating the voltage of the branch head end node, the current of the branch and the impedance of the branch, and so on;
step 3, comprehensively considering the grid-connected factors of the distributed energy sources, selecting nodes containing the distributed power sources, and carrying out symmetrical component analysis;
step 4, substituting the sequence components into a distributed power control equation to solve, and judging whether the PV node is out of bounds in a reactive power mode;
step 5, converting the sequence component current into three-phase current, and calculating a circuit current injection value of a splitting point by a circuit analysis method; the loop method is a solution method which takes a group of independent loop currents of a planar circuit or a non-planar circuit as circuit variables and lists an equation expressing related branch voltage by using the loop currents for the independent loop by using KVL; the loop current is an imaginary current flowing along the loop boundary; usually, the basic loop is selected as an independent loop, and the loop current is the corresponding branch current;
step 6, judging whether the iterative errors of the current and the voltage are smaller than a threshold value, if so, obtaining an ideal load flow calculation result, and finishing the calculation; and if the threshold value is exceeded, returning to the step 2, recalculating the node voltage and the amplitude, and repeating the subsequent steps.
4. The line loss and reactive compensation collaborative optimization method for the low-voltage distribution network according to claim 1, characterized in that: based on the load flow calculation, the step S3 is to analyze and calculate the theoretical line loss as follows:
step 1: initializing, namely, arranging user voltage and current data, user power factors and affiliated phases, line impedance parameters, network topology information and the like of each sampling moment measured by the intelligent electric meter into a data set which can be processed;
step 2: performing three-phase load flow calculation by using user, line and topological data through a forward-backward substitution method, calculating the voltage and current values of each section branch at each sampling moment, and initializing t =1 at the moment;
and step 3: performing line loss calculation;
firstly, calculating the loss generated by the current flowing on a zero line due to the unbalance of three-phase current in a three-phase four-wire system line, namely the loss of the zero line, wherein the current on each section of the zero line adopts a method of three-phase current vector superposition calculation; then, calculating the sum of the line losses of each phase, namely the loss of the three-phase power supply line; finally, the line loss and the electric meter loss of the user section, namely the user loss,
for each sampling moment, calculating the total loss and the line loss rate by using data and line parameters after load flow calculation, wherein t = t + 1;
and 4, step 4: comparing the time value T with the total time number T of the ammeter sampling in the investigation period, outputting the proportion of various types of loss in the total loss when T is greater than T, visually reflecting the influence degree of various types of loss in a chart form, and storing the line loss information at the time in a data file to finish the line loss calculation; and when T is less than T, resetting T =1, and returning to the step 2 to perform power flow calculation until an ideal line loss result is obtained.
5. The line loss and reactive compensation collaborative optimization method for the low-voltage distribution network according to claim 1, characterized in that: the step S4 specifically implements the cooperative optimization of the line loss and the reactive compensation as follows:
step 1: first, an objective function with minimal line loss is established:
in the formula: nl is the total number of branches of the system;
is the conductance of branch i-j;
、
voltages of nodes i and j, respectively;
、
phase angles of nodes i and j are respectively;
step 2: establishing a constraint condition;
the inequality constraints of the reactive power optimization of the power distribution network comprise control variable constraints and state variable constraints, the control variable constraints comprise reactive compensation capacity constraints and transformer tap constraints, the control variable constraints are discrete variables, the state variable constraints comprise voltage effective value size constraints of each node, and in addition, the distributed power supply has access capacity constraints;
and step 3: considering the economy of reactive compensation, establishing an optimization model, wherein the number of installation points of reactive compensation devices in a power distribution network is not too large, the limit of compensation capacity of each installation point is considered when performing distributed reactive power optimization configuration calculation, the limit of the total number of installation points of the reactive compensation devices in the whole transformer area is also considered, when the reactive optimization model adopts a distributed compensation mode, all load nodes in the transformer area can be selected as candidate installation nodes, and when the compensation capacity of the candidate points is equal to zero, the reactive compensation devices do not need to be installed at the nodes; when the compensation capacity of the candidate point is larger than zero, the reactive compensation device needs to be installed on the node, in the optimization model related to the invention, all load nodes are used as candidate installation nodes, the installation position of the reactive compensation device is obtained by solving the optimization model, and the subjectivity of the installation point selection of the reactive compensation device can be avoided;
and 4, step 4: solving the objective function by adopting a genetic algorithm, generating a group of initial power flow solutions in a current system environment, evaluating the quality degree of individuals in a population by the limitation of the constraint conditions and the calculation of the objective function and the fitness function, namely carrying out primary power flow calculation, eliminating the individuals with lower fitness values and the excellent individuals with higher genetic fitness values, calculating primary system power flow distribution for each evaluation to obtain information contents such as system active network loss, node voltage violation and the like, punishing the violation items by adopting a penalty function, and continuously carrying out genetic operations such as selection, crossing, variation and the like so as to obtain the optimal solution.
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