CN108280539B - Reactive compensation equal-loss-reduction optimization method based on rural power grid typical distribution area line loss calculation - Google Patents

Abstract

The invention belongs to the technical field of power transmission and distribution, and particularly relates to a loss reduction optimization method based on reactive power compensation and the like of rural power grid typical transformer area line loss calculation. The method comprises the following steps: analyzing the topological structure of the network to prepare for accurate line loss calculation; according to different characteristics of typical transformer areas of the rural power grid, data cleaning and mining of physical parameters such as power supply radius and the like, typical classification is carried out on the transformer areas of the rural power grid; calculating the loss of the rural power grid platform area by adopting an improved forward-push load flow method; establishing a reactive power optimization objective function and adding constraint conditions of voltage, power factor, compensation capacity and compensation equipment; determining the compensation positions of reactive compensation of different types of typical transformer areas and the compensation capacity of each compensation device; establishing a rural power grid platform area combined by multiple loss reduction measures; and establishing reactive compensation capacity of a decomposition coordination method. The invention can prepare for accurate line loss calculation; according to different characteristics of a typical platform area of the rural power grid, physical parameter data such as power supply radius and the like, cleaning and mining; the calculated line loss result is more accurate.

Description

Reactive compensation equal-loss-reduction optimization method based on rural power grid typical distribution area line loss calculation

Technical Field

The invention belongs to the technical field of power transmission and distribution, and particularly relates to a loss reduction optimization method based on reactive power compensation and the like of rural power grid typical transformer area line loss calculation.

Background

In recent years, the economy of China is rapidly developed, the power industry is rapidly developed, the mechanical manufacturing level of China is greatly improved, and the manufacturing technology of primary and secondary electrical equipment of a power grid is remarkably improved. After national power grid upgrading and transformation for years, the equipment level and technical performance of the power grid are greatly improved. For many years, the line loss management of a power company, especially the line loss management of a rural distribution network, is always a difficult point and a key point of the line loss management. Many relevant statistical data consulted show that in each voltage class power grid in China, the power loss of a distribution network of 10KV and below accounts for about 49% of the power loss of the whole area, and how well a power supply enterprise reduces the power loss of the distribution network is a long-term target and a working key point of management work of the power supply enterprise.

Each power supply enterprise takes the statistics, analysis and management of line loss as the daily managerial work of the enterprise. The method comprises the steps of managing and controlling various electric energy and line loss indexes, which are main means of line loss statistics work, making line loss statistics, analysis and management work, searching and analyzing various related factors which can affect line loss rate change, obtaining related conclusions through line loss analysis, and making related loss reduction measures according to local conditions aiming at actual conditions so as to enable a power supply enterprise manager where a power distribution network is located to really know the actual loss electric energy condition in operation of a power grid under jurisdiction. The method comprises the following steps of taking theoretical calculation and analysis of the line loss of the power grid as a hand grip, determining the variable loss and fixed loss ratio of the power transmission network and the power distribution network, calculating, analyzing and mastering the line loss change rule, comparing a theoretical line loss value with an actual line loss value, comparing ring ratio data with same ratio data, and comparing similar lines to find the reason influencing line loss change; the proportion of technical line loss and management line loss can be clearly judged through line loss theoretical calculation, and a foundation is laid for making loss reduction index measures and assessment index measures. Therefore, whether the current distribution network structure is reasonable or not can be effectively verified through line loss theoretical calculation and analysis, and a relevant theoretical basis is provided for the transformation of the distribution network.

The applicant researches and finds that the reactive compensation can balance the reactive power on the spot and reduce the reactive power transmitted from the power supply side; and the installation and maintenance are convenient, the cost is low, the compensation benefit is good, and the like. The reactive compensation has the function of compensating reactive power and regulating voltage. On the basis of reactive compensation loss reduction, loss reduction measures such as three-phase unbalance improvement, transformer replacement, line sectional area replacement and the like are added, so that the line loss can be reduced to an ideal result.

Therefore, the method for optimizing loss reduction such as reactive power compensation based on the line loss calculation of the typical transformer area of the rural power grid has certain theoretical basis and practical significance.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a loss reduction optimization method based on reactive power compensation and the like of the line loss calculation of a typical transformer area of a rural power grid. The method aims to prepare for more accurate line loss calculation and calculate the loss of the rural power grid transformer area more accurately.

In order to realize the purpose of the invention, the invention is realized by the following technical scheme:

the loss reduction optimization method based on reactive compensation and the like of the rural power grid typical distribution area line loss calculation comprises the following steps:

step 1: analyzing the topological structure of the network, and acquiring accurate physical parameters by adopting a gradient search method to prepare for accurate line loss calculation; according to different characteristics of a typical platform area of the rural power grid, data cleaning and mining of physical parameters such as power supply radius, the service life of the model capacity of the transformer, load distribution conditions and the like, typical classification is carried out on the platform area of the rural power grid;

step 2: calculating the loss of the rural power grid platform area by adopting an improved forward-push load flow method;

and step 3: establishing a reactive power optimization objective function and adding constraint conditions of voltage, power factor, compensation capacity and compensation equipment;

and 4, step 4: determining the compensation positions of reactive compensation of different types of typical transformer areas and the compensation capacity of each compensation device;

and 5: establishing a rural power grid platform area combined by multiple loss reduction measures;

step 6: and establishing reactive compensation capacity of a decomposition coordination method.

The step 1 comprises the following steps: classifying the loads of the power distribution network according to the network structure and the switch running state of the power distribution network system, and performing gradient search according to different loads and measured values to obtain parameters of each branch of the system and voltage, active power and reactive power of nodes;

the active power, reactive power and voltage values of a main transformer and a distribution transformer in a distribution feeder line are searched in a first gradient mode;

performing a second gradient search on the transformer which cannot obtain real-time measurement, and performing line loss calculation by using a state estimation method in order to obtain complete operation parameters with accuracy meeting requirements;

and after the number of the transformers is searched, performing third gradient search, and searching each node on the user, the overhead line and the cable line to form a node matrix.

The improved forward power flow method in the step 2 is that the voltage value of each node is more accurate and the calculated line loss value is more real by measuring and calculating the voltage value of the node and taking the average value of the obtained results;

the step 2 comprises the following steps: calculating the voltage value and the power value of the last node corresponding to each node by a forward method by acquiring the actual measurement data of each terminal load node, if the last node has no actual measurement value, calculating the voltage value obtained by forward calculation, and if the actual measurement value exists, taking the average value of the actual measurement value and the calculated value; if the last node corresponds to two load nodes, if the node has no measured value, taking the average value of the forward voltage of the two loads, otherwise, taking the average value of the three values, and so on; up to the root node; the result of line loss is equal to the total loss calculated by the transformer plus the total loss calculated on the line;

A_loss＝T_loss+L_loss

in the above formula A_lossFor all line losses, T_lossIs the loss of the transformer, L_lossLoss of the transmission line;

step 21: under the condition that the line impedance parameters are known, the loss on a line between a load node and a superior node thereof and the voltage of the superior node can be accurately solved as long as the effective values of the active, the reactive and the voltage of the load node are measured, and the complex multiplication and division are avoided when the line loss and the node voltage are calculated; line l between nodes 2 and 3_2-3Impedance of each phase is Z_2-3＝R_2-3+jX_2-3The three-phase output power of the node 3 is measured as P at the same time₃+jQ₃The effective value of the line voltage is U₃；

Line l_2-3The active power loss in (c) is:

in the above formula,. DELTA.P_2-3Refers to the line l_2-3Active power loss on; p₃Is the active power of node 3, Q₃Is the reactive power of node 3; u shape₃Is the voltage of node 3, R_2-3Is a line l_2-3A resistance value of (d);

the reactive power loss is:

in the above formula,. DELTA.Q_2-3Refers to the line l_2-3Active power loss on; p₃Is the active power of node 3, Q₃Is the reactive power of node 3; u shape₃Is the voltage of node 3, R_2-3Is a line l_2-3A resistance value of (d);

the output power of node 2 is:

S₂＝(P₃+ΔP_2-3)+j(Q₃+ΔQ_2-3)

in the above formula, S₂Refers to the output power of node 2; p₃Is the active power of node 3, Q₃Is the reactive power of node 3; delta P_2-3、ΔQ_2-3Respectively is a line l_2-3Upper loss active and reactive power;

effective voltage value U of node 2₂Comprises the following steps:

in the above formula, U₂Refers to the effective value voltage DeltaU of node 2_2-3、δU_2-3Is a line l_2-3The longitudinal and lateral components of the voltage drop;

step 22: assuming a certain region, the region has 11 nodes in total, the resistance and reactance between the nodes are known, and the active power, reactive power and voltage effective value of each load node are obtained through a data acquisition system;

the specific implementation steps of the algorithm are as follows:

(1) firstly, classifying and numbering nodes, and clearly distinguishing power supply nodes and load nodes; the power supply node is a node 0, and the load nodes are nodes 2, 3, 8, 9 and 10;

(2) calculating the voltage value and the power value of the last node corresponding to each node by a forward method by acquiring the actual measurement data of each terminal load node, if the last node has no actual measurement value, calculating the voltage value obtained by forward calculation, and if the actual measurement value exists, taking the average value of the actual measurement value and the calculated value; if the last node corresponds to two load nodes, if the node has no measured value, taking the average value of the forward voltage of the two loads, otherwise, taking the average value of the three values, and so on; up to the power supply node;

the line between nodes 8 and 6 is l_8-6Each impedance between the lines is Z_8-6＝R_8-6+jX_8-6The three measured output powers of the load 8 nodes are P₈+jQ₈Then line l_8-6Active power loss between:

in the above formula,. DELTA.P_8-6Is a line l_8-6Active power loss of P₈Is the active power of node 8, Q₈Reactive power of node 8, U₈Is the effective value of the voltage at node 8, R_8-6Is a line l_8-6Impedance in between;

the reactive power loss is:

in the above formula,. DELTA.Q_8-6Is a line l_8-6Reactive power loss of P₈Is the active power of node 8, Q₈Reactive power of node 8, U₈Is the effective value of the voltage at node 8, X_8-6Is a line l_8-6Reactance between;

the output power of node 6 is:

S₆＝P₆+jQ₆＝(P₈+ΔP_8-6)+j(Q₈+ΔQ_8-6)

in the above formula, S₆Refers to the output power of node 6; p₆Is the active power, Q, of node 6₆Is the reactive power of node 6; delta P_8-6、ΔQ_8-6Respectively is a line l_8-6Upper loss active and reactive power; p₈、Q₈Respectively, the active power and reactive power of node 8;

the voltage value at node 6 is:

in the above formula, U₈Is the effective value of the voltage at node 8, Δ U_8-6Is a line l_8-6Longitudinal component of voltage drop, δ U_8-6Is a line l_8-6Transverse to voltage dropA component;

wherein:

the same can pass through the line l_9-6Calculating the voltage and the output power of the node 6, if the voltage value and the output power of the node 6 can be measured, calculating the average value of the voltage value and the output power of the node 6 to obtain the voltage value and the power value of the node 6, and if the voltage value and the power value of the node 6 are not measured, calculating the average value of the voltage value of the node 6 and calculating the average value of the power value;

(3) marking the calculated lines, and continuously searching unmarked lines until all the lines are calculated;

(4) calculating the loss of all the public transformers, and calculating the copper loss and the iron loss of the transformers by using the actually measured node load and voltage values during calculation; therefore, the influence of load and voltage is fully considered in transformer loss calculation;

(5) total line loss:

A_loss＝T_loss+L_loss

wherein A is_lossFor all line losses, T_lossIs the loss of the transformer, L_lossIs the loss of the transmission line.

The objective function in step 3:

min(P₁-P₂)

wherein P1 is investment cost, P2 is loss reduction profit, and the objective function is the minimum value of the difference value of the two;

wherein:

in the above formula, n isNode compensation equipment total number; n is a radical of_iThe number of groups of the compensating capacitor of the ith equipment; ci is the capacity of a single group of capacitors corresponding to the compensation equipment; ma is the unit price of the compensation capacity; mb is a single set price for the compensation device; mc is the cost invested in installing the equipment;

wherein:

P₂＝(f₁-f₂)·c·T

in the above formula, f₁To compensate for the previous power loss, f₂For the compensated power loss, c is the corresponding electricity price, T time of operation;

the method comprises the following steps: the reactive compensation decentralized configuration optimization model of the low-voltage power distribution network is as follows by taking the active loss of the minimum low-voltage power distribution network as a target:

min f(x)

s.t h(x)＝0,

in the above formula: the objective function f (x) is the difference value of the investment cost and the loss reduction profit; h (x) is a power balance equation of each node, x is a decision variable and a state variable of the system, the decision variable is a parallel reactive compensation capacity Q of a reactive compensation point, and the state variable comprises a voltage amplitude V and a phase angle delta of each node; the inequality constraint l (x) comprises upper and lower limit constraints of voltage amplitude of each node, upper and lower limit constraints of parallel reactive compensation capacity of each reactive compensation point, upper and lower limits of power factor and upper and lower limits of compensation equipment grouping number;

the difference between the investment cost and the loss reduction profit is an objective function f (x), and the expression is as follows:

f(x)＝P₁-P₂

step 32: the constraint condition; the equation constraint h (x) is expressed as:

the following can be obtained from the power flow calculation equation:

in the above formula, P_iAnd Q_iActive power and reactive power injected into the transformer area respectively, wherein the inflow is positive, the outflow is negative, and Q is_ciFor compensating reactive power, V_iIs the voltage amplitude of node i, δ_ijIs the voltage phase angle difference between node i and node j, G_ijAnd B_ijRespectively a real part and an imaginary part of j columns of elements in the ith row of the network node admittance matrix, wherein n is the total number of the nodes in the transformer area;

the inequality constraint l (x) is expressed as:

in the above formula V_imin、V_imaxIs the minimum and maximum voltage allowed by the node, Q_cimin、Q_cimaxIs the minimum reactive power following maximum reactive power compensation allowed by the node, rho_imin、ρ_imaxAre the maximum and minimum power factors allowed at the node measurement,

the minimum packet number and the maximum packet number for the switching of the compensation equipment.

The step 4 comprises the following steps:

step 41: firstly, calculating compensation quantity required by all nodes in a typical rural transformer area, calculating total reactive compensation capacity required by the transformer area, carrying out reactive compensation on each node, wherein the reactive compensation is not in accordance with the reality, and selecting important nodes with large load power as nodes needing compensation by using a sensitivity analysis method and a human factor method; setting 2 genes on a chromosome of each compensation device in the population by using a genetic algorithm, respectively representing the group number of the compensation devices and each group of compensation capacity, and calculating the optimal reactive compensation capacity of the node;

step 42: when calculating reactive power configuration optimization of different types of distribution areas on the basis of the step 41, firstly defining three electrical characteristic index circuit distribution transformation average load rate alpha, natural power factor cos phi, power supply radius L and reactive power compensation rate beta, and setting typical rural electrical indexes as ground state values according to rural power planning design guide rules and a specific electrical characteristic index system of local rural areas;

in the above formula, beta₀Is the optimal reactive compensation rate, W, of a typical rural area_nReactive configuration capacity, S, to be supplemented for the area_NThe rated capacity of the platform area;

when the reactive compensation capacity of the random distribution area is calculated, the change condition of the optimal reactive compensation rate is recorded by respectively changing each electrical characteristic index, the change degree of the reactive compensation rate is represented by the size of sensitivity, the size of the sensitivity is equal to the change of the reactive compensation rate corresponding to each electrical characteristic change, the reactive capacity of the random distribution area is configured, the difference value of the actual value of each electrical characteristic value and the electrical characteristic corresponding to the typical distribution area is used as a decision, and the size of the sensitivity is used for carrying out corresponding weighted calculation;

in the above formula beta₀Is the reactive compensation rate of a typical distribution area, Δ m_iIs the difference between the electrical characteristic values of the random area and the typical area, lambda_iThe sensitivity corresponding to the electrical characteristic value.

The step 5 comprises the following steps:

step 51: firstly, determining loss reduction measures of rural power grid transformer area and recording the loss reduction measures as X_iWherein i is 1,2,. 4; x₁～X₄The method corresponds to four rural power grid district loss reduction measure types of reactive compensation, three-phase unbalance improvement, transformer capacity replacement and line section area replacement; on the basis, the possible implementation scheme of a certain type of loss reduction measures is taken as the loss reduction scheme in the loss reduction of the rural power grid distribution area, namely the possible implementation scheme is the loss reduction scheme

Indicates the ith speciesThe j-th possible implementation of the impairment reduction measure category; x₁The loss reduction scheme corresponding to the loss reduction measures comprises a transformer station centralized compensation device, a user decentralized control device and an optimized reactive compensation device; x₂The loss reduction scheme corresponding to the loss reduction measures comprises the steps of changing the phase sequence of the wiring of a client, a three-phase unbalanced voltage regulator and an autotransformer; x₃The loss reduction scheme corresponding to the loss reduction measure comprises a capacity reduction transformation method, an economic operation mode of the transformer and an energy-saving transformer; x₄The loss reduction scheme corresponding to the loss reduction measure comprises the steps of parallel bunched conductors, increase of the sectional area of the conductors and line insulation transformation;

for loss reduction measure X_iBecause of the existence of loss influence factor analysis, the loss reduction measure type with larger weight is selected from the loss reduction measure influence weight evaluation analysis result to be used as an alternative loss reduction measure to be implemented on the current rural power grid platform area, so that the loss reduction measure X is implemented_iWhether selected may be described by the following equation;

aiming at the selected loss reduction measures, possible loss reduction measures can be further considered to implement the project, namely the possible loss reduction project

Aiming at the description of the implementation principle of the loss reduction measures of the rural power grid district, various selectable implementation items are provided for each type of loss reduction measure according to manual experience and different existing optimization algorithms, and the following formula is a description of whether the jth loss reduction item in the ith loss reduction measure is selected or not;

step 52: in order to ensure that the loss reduction achieves a better effect, a loss reduction alternative scheme is formed through the following steps;

the alternative scheme for reducing loss is formed by combining loss reduction projects, and the loss influence factors of the rural power grid transformer area are analyzedThe main influence factors influencing the technical loss of the rural power grid distribution area in the current rural power grid distribution area and the corresponding types of the loss reduction measures can be preliminarily determined, so that the selection condition of the loss reduction measures can be determined when the loss reduction alternative scheme is generated, and the selected loss reduction measures after the loss analysis are assumed to be X_a、X_b、X_cThen, the structure of the loss reduction option in this case is as follows:

under the condition that the implementation items of each type of loss reduction measure are determined, one loss reduction candidate item is the combination of the selected loss reduction items, and the loss reduction items are met

Mutual exclusivity between them, as shown by the following formula:

in the above formula: f. of_iThe ith loss reduction candidate item is pointed; g refers to the mutual exclusivity among loss reduction projects, namely the constraint that the implementation of different implementation projects of the same type of loss reduction measures in the rural power grid area cannot occur simultaneously; mutual exclusion relation constraint among projects is mainly embodied in a loss reduction decision flow;

the generation flow of the loss reduction alternative item of the rural power grid district is as follows:

(1) determining loss influence factors playing a key important role in the technical line loss of the rural power grid platform area through rural power grid platform area loss analysis;

(2) based on sensitivity analysis, determining loss reduction measure X in rural power grid platform area optimization decision_iSelecting the condition;

(3) for each selected loss reduction measure X_iAlternative loss reduction projects are obtained through research of weight analysis of measure schemes

(4) Generating initial rural power grid distribution area loss reduction according to various combinations of loss reduction projectsCandidate item f_i；

Step 53: in the rural power grid distribution area loss reduction decision model, comprehensive benefits of loss reduction electric quantity brought by loss reduction measures to the current rural power grid distribution area are fully reflected, and the rural power grid distribution area loss reduction optimization decision model containing a decision objective function and decision constraint conditions is established by analyzing investment benefit evaluation;

(1) a decision-making objective function;

in order to comprehensively optimize the benefits obtained by reducing the construction and operation costs and the power consumption of the rural power grid transformer area, under the support of a life cycle cost theory, an objective function is established, wherein the objective function comprises the comprehensive cost, the loss reduction cost, the operation and maintenance cost, the fault cost, the removal and recovery cost and the power selling cost caused by the power consumption of the rural power grid transformer area within the operation period;

(2) constraint conditions of the decision:

the constraint conditions of the rural power grid distribution area loss reduction optimization decision model comprise six contents: power supply reliability constraint, user average power failure time constraint, voltage deviation constraint, line transmission constraint, investment limit constraint and inter-project mutual exclusion relationship constraint;

power supply reliability constraint: the power supply reliability is not lower than a preset specified limit value;

constraint of average power failure time of users: the average power failure time of a user does not exceed a preset specified limit value;

voltage deviation constraint: the absolute value of the voltage deviation should not exceed 7% of the standard voltage;

fourthly, line transmission constraint: the actual transmission capacity of the line should not exceed its maximum transmission capacity, generally expressed in terms of transmission current;

investment restriction constraint: the investment limit constraint means that the investment of a loss reduction scheme adopting a plurality of loss reduction measure combinations is within a preset investment limit, and the loss reduction scheme investment mainly aims at loss reduction cost;

(3) investment benefit evaluation indexes are as follows:

according to the basic steps of technical-economic comparison and evaluation, for the rural power grid loss reduction and energy conservation transformation project, corresponding technical indexes are firstly determined, and then the technical indexes are preferentially selected according to economic indexes in a qualified scheme; the specific technical indexes of the loss reduction scheme comprise electric energy loss rate, voltage qualification rate, power factor and service life;

according to the economic technology assessment in the rural power network planning and design guide rule, the economic indexes of the specified loss reduction scheme comprise an investment recovery period, a net present value, a net annual value, a net present value rate and an internal yield rate;

(4) and (3) decision of the loss reduction optimization scheme:

the decision of the loss reduction scheme aims to optimize a loss reduction scheme set comprising various selection possibilities of loss reduction measures and determine a loss reduction measure combination and a loss reduction implementation scheme with optimal comprehensive benefits.

The step 6 comprises the following steps:

step 61: setting the reactive compensation capacity calculated in the step 4 as c₁And the reactive compensation capacity calculated in the step 5 is c₂If the difference value calculated by the two is less than the set margin epsilon, taking the reactive compensation capacity as c₁If the difference value of the two is larger than the set margin, establishing a decomposition coordination method to solve the reactive compensation capacity; decomposing an original target function into two mutually-connected sub-target functions; the two sub-target functions interact with each other to jointly optimize and calculate the final reactive compensation capacity;

step 62: firstly, establishing a mathematical model:

min C(x)+D(x)

s.t A(x)≥B

E(x)+F(x)≥g

R(x)+T(x)＝h

in the above formula, x is the configured reactive compensation capacity, y is the actual operation parameter of the power grid under the existing configuration, c (x) + d (x) is the cost for configuring the reactive power supply, a (x) is not less than B is the investment constraint (plan configuration constraint, configuration capacity constraint), e (x) + f (x) is not less than g is the voltage inequality constraint, and r (x) + t (x) is the tidal current balance equality constraint;

as long as the reactive compensation capacity investment variable x is determined, the actual operation parameter y can be determined through optimization of the system operation mode; namely, the original problem can be regarded as the unification of two optimization processes, namely, the investment optimization process for determining the position and the size of the reactive configuration capacity is called as a main investment problem; secondly, determining an operation optimization process which minimizes the operation cost under the existing configuration, which is called as an operation sub-problem;

when any one of the determined capacities x is given^*And the optimal value D corresponding to the operation subproblem can be represented as w (x), the corresponding investment main problem and operation subproblem can be decomposed as follows:

(1) the main problems of investment are as follows:

Min C(x)+W(x)

s.t A(x)≥B

in the above formula, C (x) + W (x) is the total cost of investment, wherein W (x) is a link connecting the main problem and the subproblems, and A (x) ≧ B is the condition of investment constraint;

(2) the operation sub-problem:

W(x)＝minD(y)

s.t F(x)≥g-E(x^*)

T(y)＝h-R(x^*)

in the above formula, minD (y) is the cost of operation optimization, F (x) is not less than g-E (x)^*) For voltage inequality constraints, t (y) h-R (x)^*) Constraint for power flow balance equality;

obviously, the main investment problem and the sub-operation problem are closely related by using W (x), the correction of W (x) is provided by solving the sub-operation problem, a new linear constraint after the correction is formed, then the main investment problem is returned, the main problem and the sub-problem are alternately solved, and the optimal solution of the reactive compensation quantity is obtained.

Compared with the prior art, the invention has the advantages and beneficial effects that:

according to the invention, the topological structure of the network is fully analyzed, and accurate physical parameters are obtained by adopting a gradient search method, so that preparation is made for accurate line loss calculation; and (4) cleaning and mining data according to different characteristics of a typical transformer area of the rural power grid, power supply radius, service life of the type capacity of the transformer, load distribution condition and other physical parameters. The loss of the rural power grid area is calculated by adopting an improved forward-push tidal current method, the calculated line loss result is more accurate, the constraint conditions of voltage, power factor, compensation capacity and compensation equipment are added in the reactive compensation on the basis of the line loss, the reactive compensation can achieve reactive local balance, and the optimal compensation effect of regulating the voltage and calculating the force can be achieved while loss reduction measures are carried out. In order to obtain better loss reduction effect, loss reduction measures such as three-phase unbalance improvement, transformer capacity replacement, line sectional area replacement and the like are added on the basis of reactive compensation.

The invention will be further described and illustrated with reference to the following drawings and specific examples, but the invention is not limited to these examples.

Drawings

FIG. 1 is a voltage versus power diagram of a circuit in accordance with the method of the present invention;

FIG. 2 is a diagram of a region structure corresponding to the method of the present invention;

FIG. 3 is a structural diagram of a corresponding loss reduction scheme of the method of the present invention;

FIG. 4 is a block diagram of the optimization of loss reduction measures in rural power grid areas corresponding to the investment benefit rate of the method of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. 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.

The invention relates to a reactive compensation equal-loss-reduction optimization method based on rural power grid typical transformer area line loss calculation, which comprises the following steps of:

step 1: analyzing the topological structure of the network, and acquiring accurate physical parameters by adopting a gradient search method to prepare for accurate line loss calculation; and (3) performing typical classification on the rural power grid transformer area according to different characteristics of the rural power grid typical transformer area and data cleaning and mining of physical parameters such as power supply radius, transformer model capacity service life, load distribution condition and the like.

According to the network structure and the switch operation state of the power distribution network system, the loads of the power distribution network are classified, and gradient search is carried out according to different loads and measured values to obtain parameters of all branches of the system and voltage, active power and reactive power of nodes.

The first gradient searches active power, reactive power and voltage values of a main transformer and a distribution transformer in the distribution feeder line.

And performing second gradient search on the transformer which cannot obtain real-time measurement, and performing line loss calculation by using a state estimation method in order to obtain complete operating parameters with accuracy meeting requirements.

And after the number of the transformers is searched, performing third gradient search, and searching each node on the user, the overhead line and the cable line to form a node matrix.

Step 2: calculating the loss of the rural power grid platform area by adopting an improved forward-push load flow method;

the improved forward power flow method is that the voltage value of each node is more accurate and the calculated line loss value is more real by measuring and calculating the voltage value of the node and taking the average value of the obtained results.

The step 2 comprises the following steps: calculating the voltage value and the power value of the last node corresponding to each node by a forward method by acquiring the actual measurement data of each terminal load node, if the last node has no actual measurement value, calculating the voltage value obtained by forward calculation, and if the actual measurement value exists, taking the average value of the actual measurement value and the calculated value; if the last node corresponds to two load nodes, if the node has no measured value, taking the average value of the forward voltage of the two loads, otherwise, taking the average value of the three values, and so on; up to the root node. The result of the line loss is equal to the total loss calculated by the transformer plus the total loss calculated on the line.

A_loss＝T_loss+L_loss

In the above formula A_lossFor all line losses, T_lossIs the loss of the transformer, L_lossIs the loss of the transmission line.

Step 21: in the case of a known line impedance parameter, it is only necessary to measureThe effective values of active power, reactive power and voltage to the load node can accurately calculate the loss on a line between the load node and a superior node thereof and the voltage of the superior node, and the calculation of the line loss and the node voltage avoids complex multiplication and division. Line l between nodes 2 and 3 as shown in fig. 1_2-3Impedance of each phase is Z_2-3＝R_2-3+jX_2-3The three-phase output power of the node 3 is measured as P at the same time₃+jQ₃The effective value of the line voltage is U₃。

Line l_2-3The active power loss in (c) is:

in the above formula,. DELTA.P_2-3Refers to the line l_2-3Active power loss on; p₃Is the active power of node 3, Q₃Is the reactive power of node 3; u shape₃Is the voltage of node 3, R_2-3Is a line l_2-3A resistance value of (c).

The reactive power loss is:

in the above formula,. DELTA.Q_2-3Refers to the line l_2-3Active power loss on; p₃Is the active power of node 3, Q₃Is the reactive power of node 3; u shape₃Is the voltage of node 3, R_2-3Is a line l_2-3A resistance value of (c).

The output power of node 2 is:

S₂＝(P₃+ΔP_2-3)+j(Q₃+ΔQ_2-3)

in the above formula, S₂Refers to the output power of node 2; p₃Is the active power of node 3, Q₃Is the reactive power of node 3; delta P_2-3、ΔQ_2-3Respectively is a line l_2-3The active and reactive power lost.

Effective voltage value U of node 2₂Comprises the following steps:

in the above formula, U₂Refers to the effective value voltage DeltaU of node 2_2-3、δU_2-3Is a line l_2-3The longitudinal and lateral components of the voltage drop.

Step 22: assume a certain region whose structure is shown in fig. 2. The station area has 11 nodes, the resistance and the reactance between the nodes are known, and the active power, the reactive power and the voltage effective value of each load node are obtained through a data acquisition system.

The specific implementation steps of the algorithm are as follows:

(1) firstly, classifying and numbering nodes, and distinguishing power supply nodes and load nodes.

Taking fig. 2 as an example, the power node is a 0 node, and the load nodes are 2, 3, 8, 9, and 10 nodes

(2) Calculating the voltage value and the power value of the last node corresponding to each node by a forward method by acquiring the actual measurement data of each terminal load node, if the last node has no actual measurement value, calculating the voltage value obtained by forward calculation, and if the actual measurement value exists, taking the average value of the actual measurement value and the calculated value; if the last node corresponds to two load nodes, if the node has no measured value, taking the average value of the forward voltage of the two loads, otherwise, taking the average value of the three values, and so on; up to the power supply node.

The line between nodes 8 and 6 is l as shown in fig. 2_8-6Each impedance between the lines is Z_8-6＝R_8-6+jX_8-6The three measured output powers of the load 8 nodes are P₈+jQ₈Then line l_8-6Active power loss between:

in the above formula,. DELTA.P_8-6Is a line l_8-6Active power loss of P₈Is the active power of node 8, Q₈Reactive power of node 8, U₈Is the effective value of the voltage at node 8, R_8-6Is a line l_8-6The impedance therebetween.

The reactive power loss is:

in the above formula,. DELTA.Q_8-6Is a line l_8-6Reactive power loss of P₈Is the active power of node 8, Q₈Reactive power of node 8, U₈Is the effective value of the voltage at node 8, X_8-6Is a line l_8-6The reactance between.

The output power of node 6 is:

S₆＝P₆+jQ₆＝(P₈+ΔP_8-6)+j(Q₈+ΔQ_8-6)

in the above formula, S₆Refers to the output power of node 6; p₆Is the active power, Q, of node 6₆Is the reactive power of node 6; delta P_8-6、ΔQ_8-6Respectively is a line l_8-6The active and reactive power lost. P₈、Q₈Respectively the active power and the reactive power of the node 8.

The voltage value at node 6 is:

in the above formula, U₈Is the effective value of the voltage at node 8, Δ U_8-6Is a line l_8-6Longitudinal component of voltage drop, δ U_8-6Is a line l_8-6The transverse component of the voltage drop.

Wherein:

the same can pass through the line l_9-6The voltage and output power of the node 6 are calculated, if the voltage and output power of the node 6 can be measured, the voltage and power of the node 6 are obtained by calculating the average value of the three values, if the voltage and power of the node 6 are not measured, the voltage of the node 6 is obtained by calculating the average value, and the power is also obtained by calculating the average value.

(3) And marking the lines which are already calculated, and continuing to search for unmarked lines until all the lines are calculated.

(4) And calculating the loss of all the public transformers, and calculating the copper loss and the iron loss of the transformers by using the actually measured node load and voltage values during calculation. Thus, the transformer loss calculation takes the influences of the load and the voltage into full consideration.

(5) Total line loss:

A_loss＝T_loss+L_loss

wherein A is_lossFor all line losses, T_lossIs the loss of the transformer, L_lossIs the loss of the transmission line.

And step 3: establishing a reactive power optimization objective function and adding constraint conditions of voltage, power factor, compensation capacity and compensation equipment;

step 31: the objective function is:

min(P₁-P₂)

wherein P1 is investment cost, P2 is loss reduction profit, and the objective function is the minimum value of the difference value of the two.

Wherein:

in the above formula, n is the total number of node compensation devices; n is a radical of_iIs a component of a compensating capacitor of an ith apparatusThe number of groups; ci is the capacity of a single group of capacitors corresponding to the compensation equipment; ma is the unit price of the compensation capacity; mb is a single set price for the compensation device; mc is the cost invested in installing the equipment.

Wherein:

P₂＝(f₁-f₂)·c·T

in the above formula, f₁To compensate for the previous power loss, f₂For compensated power loss, c is the corresponding electricity price, T time of operation.

The method comprises the following steps: the reactive compensation decentralized configuration optimization model of the low-voltage power distribution network is as follows by taking the active loss of the minimum low-voltage power distribution network as a target:

min f(x)

s.t h(x)＝0,

in the above formula: the objective function f (x) is the difference value of the investment cost and the loss reduction profit; h (x) is a power balance equation of each node, x is a decision variable and a state variable of the system, the decision variable is a parallel reactive compensation capacity Q of a reactive compensation point, and the state variable comprises a voltage amplitude V and a phase angle delta of each node. The inequality constraint l (x) comprises upper and lower limit constraints of voltage amplitude of each node, upper and lower limit constraints of parallel reactive compensation capacity of each reactive compensation point, upper and lower limits of power factor and upper and lower limits of compensation equipment grouping number.

The difference between the investment cost and the loss reduction profit is an objective function f (x), and the expression is as follows:

f(x)＝P₁-P₂

step 32: the constraint condition.

The equation constraint h (x) is expressed as:

the following can be obtained from the power flow calculation equation:

in the above formula, P_iAnd Q_iActive power and reactive power injected into the transformer area respectively, wherein the inflow is positive, the outflow is negative, and Q is_ciFor compensating reactive power, V_iIs the voltage amplitude of node i, δ_ijIs the voltage phase angle difference between node i and node j, G_ijAnd B_ijThe real part and the imaginary part of the j column elements of the ith row of the network node admittance matrix are respectively, and n is the total number of the station area nodes.

The inequality constraint l (x) is expressed as:

in the above formula V_imin、V_imaxIs the minimum and maximum voltage allowed by the node, Q_cimin、Q_cimaxIs the minimum reactive power following maximum reactive power compensation allowed by the node, rho i_min、ρ_imaxAre the maximum and minimum power factors allowed at the node measurement,

the minimum packet number and the maximum packet number for the switching of the compensation equipment.

And 4, step 4: determining the compensation positions of reactive compensation of different types of typical transformer areas and the compensation capacity of each compensation device;

step 41: firstly, the compensation quantity required by all nodes in a typical rural transformer area is calculated, the total reactive compensation capacity required by the transformer area is calculated, each node is subjected to reactive compensation, the reactive compensation is not practical, and important nodes with large load power are selected as nodes needing compensation by using a sensitivity analysis method and a human factor method. And setting 2 genes on a chromosome of each compensation device in the population by using a genetic algorithm, respectively representing the group number of the compensation devices and each group of compensation capacity, and calculating the optimal reactive compensation capacity of the node.

Step 42: when calculating reactive power configuration optimization of different types of distribution areas on the basis of the step 41, firstly, defining three electrical characteristic index circuit distribution transformation average load rate alpha, natural power factor cos phi, power supply radius L and reactive power compensation rate beta, and setting a typical rural electrical index as a ground state value according to rural power planning design guide rules and a specific electrical characteristic index system of local rural areas.

In the above formula, beta₀Is the optimal reactive compensation rate, W, of a typical rural area_nReactive configuration capacity, S, to be supplemented for the area_NIs the rated capacity of the platform area.

When the reactive compensation capacity of the random distribution area is calculated, the change condition of the optimal reactive compensation rate is recorded by respectively changing each electrical characteristic index, the change degree of the reactive compensation rate is represented by the size of sensitivity, the size of the sensitivity is equal to the change of the reactive compensation rate corresponding to each electrical characteristic change, the reactive capacity of the random distribution area is configured, the difference value of the actual value of each electrical characteristic value and the electrical characteristic corresponding to the typical distribution area is used as a decision, and corresponding weighted calculation is carried out by using the size of the sensitivity.

In the above formula beta₀Is the reactive compensation rate of a typical distribution area, Δ m_iIs the difference between the electrical characteristic values of the random area and the typical area, lambda_iThe sensitivity corresponding to the electrical characteristic value.

And 5: and establishing a rural power grid platform area with a plurality of loss reduction measure combinations.

Step 51: firstly, determining loss reduction measures of rural power grid transformer area and recording the loss reduction measures as X_iWherein i is 1,2,. 4; x₁～X₄The method corresponds to four rural power grid district loss reduction measures types of reactive compensation, three-phase imbalance improvement, transformer capacity replacement and line section area replacement. On the basis, the possible implementation scheme of a certain type of loss reduction measures is taken as the loss reduction scheme in the loss reduction of the rural power grid distribution area, namely the possible implementation scheme is the loss reduction scheme

Represents the j-th possible implementation of the ith kind of loss reduction measure. X₁The loss reduction scheme corresponding to the loss reduction measures comprises a transformer station centralized compensation device, a user decentralized control device and an optimized reactive compensation device. X₁The loss reduction scheme corresponding to the loss reduction measures comprises the steps of changing the phase sequence of the wiring of a customer, a three-phase unbalanced voltage regulator and an autotransformer. X₃The loss reduction scheme corresponding to the loss reduction measure comprises a capacity reduction transformation method, an economic operation mode of the transformer and an energy-saving transformer. X₄The loss reduction scheme corresponding to the loss reduction measures comprises the steps of parallel bunched conductors, increase of the sectional area of the conductors and line insulation transformation.

For loss reduction measure X_iBecause of the existence of loss influence factor analysis, the loss reduction measure type with larger weight is selected from the loss reduction measure influence weight evaluation analysis result to be used as an alternative loss reduction measure to be implemented on the current rural power grid platform area, so that the loss reduction measure X is implemented_iWhether selected can be described by the following equation.

Aiming at the selected loss reduction measures, possible loss reduction measures can be further considered to implement the project, namely the possible loss reduction project

For the description of the implementation principle of the loss reduction measures of the rural power grid district, a plurality of selectable implementation items can be provided for each type of loss reduction measure according to manual experience and different existing optimization algorithms, and the following formula is a description of whether the jth loss reduction item in the ith loss reduction measure is selected or not.

The structure diagram of the loss reduction scheme corresponding to the method of the invention is shown in fig. 3.

Step 52: the loss reduction alternative is formed by the following steps in order to ensure that the loss reduction achieves a better effect.

The loss reduction alternative scheme is formed by combining loss reduction projects, and due to the existence of loss influence factor analysis of the rural power grid transformer area, main influence factors influencing the technical loss of the rural power grid transformer area in the current rural power grid transformer area and corresponding types of loss reduction measures can be preliminarily determined, so that the selection condition of the loss reduction measures can be determined when the loss reduction alternative scheme is generated, and the selected loss reduction measures after the loss analysis are assumed to be X_a、X_b、X_cThen, the structure of the loss replacement option in this case is shown in fig. 3:

under the condition that the implementation items of each type of loss reduction measure are determined, one loss reduction candidate item is the combination of the selected loss reduction items, and the loss reduction items are met

Mutual exclusivity between them, as shown by the following formula:

in the above formula: f. of_iThe ith loss reduction candidate item is pointed; g refers to the mutual exclusivity among loss reducing projects, namely the constraint that the implementation of different implementation projects of the same kind of loss reducing measures in the rural power grid area is impossible to occur simultaneously. The mutual exclusion relationship constraint among the projects is mainly embodied in a loss reduction decision flow.

The generation flow of the loss reduction alternative item of the rural power grid district is as follows:

(1) determining loss influence factors playing a key important role in the technical line loss of the rural power grid platform area through rural power grid platform area loss analysis;

(2) based on sensitivity analysis, determining loss reduction measure X in rural power grid platform area optimization decision_iSelecting the condition;

(3) for each selected loss reduction measure X_iAlternative loss reduction projects are obtained through research of weight analysis of measure schemes

(4) Generating initial rural power grid distribution area loss reduction alternative item f according to various combinations of loss reduction items_i；

Step 53: in the rural power grid distribution area loss reduction decision model, the comprehensive benefit of loss reduction electric quantity brought by loss reduction measures to the current rural power grid distribution area is fully reflected, the rural power grid distribution area loss reduction optimization decision model containing decision objective functions and decision constraint conditions is established by analyzing investment benefit evaluation, and a loss reduction measure optimization frame of the rural power grid distribution area is shown in fig. 4.

(1) Objective function of decision:

in order to comprehensively optimize the benefits obtained by reducing the construction and operation costs and the power consumption of the rural power grid transformer area, under the support of a life cycle cost theory, an objective function is established, wherein the objective function comprises the comprehensive cost (the loss reduction cost, the operation and maintenance cost, the fault cost and the removal and recovery cost) of the rural power grid transformer area within the operation age and the power selling cost caused by the power consumption.

(2) Constraint conditions of the decision:

the constraint conditions of the rural power grid distribution area loss reduction optimization decision model comprise six contents: the method comprises the following steps of power supply reliability constraint, user average power failure time constraint, voltage deviation constraint, line transmission constraint, investment limit constraint and inter-project mutual exclusion relationship constraint.

Power supply reliability constraint: the power supply reliability should not be lower than a preset specified limit.

Constraint of average power failure time of users: the average power failure time of the user should not exceed a preset limit value.

Voltage deviation constraint: the absolute value of the voltage deviation should not exceed 7% of the standard voltage.

Fourthly, line transmission constraint: the actual transmission capacity of the line should not exceed its maximum transmission capacity, generally expressed in terms of transmission current.

Investment restriction constraint: the investment limit constraint means that the investment of the loss reduction scheme adopting a plurality of loss reduction measure combinations is within a preset investment limit, and the loss reduction scheme investment mainly aims at loss reduction cost.

(3) Investment benefit evaluation indexes are as follows:

according to the basic steps of technical and economic comparison and evaluation, for the rural power grid loss reduction and energy saving reconstruction project, corresponding technical indexes are firstly established, and then the technical indexes are preferentially selected according to economic indexes in a qualified scheme. The specific technical indexes of the loss reduction scheme comprise electric energy loss rate, voltage qualification rate, power factor, service life and the like.

According to the economic technology assessment in the rural power network planning and design guide rule, the economic indexes of the loss reduction scheme comprise the investment recovery period, the net present value, the net annual value, the net present value rate, the internal yield rate and the like.

(4) And (3) decision of the loss reduction optimization scheme:

the decision of the loss reduction scheme aims to optimize a loss reduction scheme set comprising various selection possibilities of loss reduction measures and determine a loss reduction measure combination and a loss reduction implementation scheme with optimal comprehensive benefits.

Step 6: and establishing reactive compensation capacity of a decomposition coordination method.

Step 61: setting the reactive compensation capacity calculated in the step 4 as c₁And the reactive compensation capacity calculated in the step 5 is c₂If the difference value calculated by the two is less than the set margin epsilon, taking the reactive compensation capacity as c₁And if the difference value of the two is larger than the set margin, establishing a decomposition coordination method to solve the reactive compensation capacity. An original objective function is decomposed into two interconnected sub-objective functions. And the two sub-target functions interact with each other to jointly optimize and solve the final reactive compensation capacity.

Step 62: firstly, establishing a mathematical model:

min C(x)+D(x)

s.t A(x)≥B

E(x)+F(x)≥g

R(x)+T(x)＝h

in the above formula, x is the configured reactive compensation capacity, y is the actual operation parameter of the power grid under the existing configuration, c (x) + d (x) is the cost for configuring the reactive power supply, a (x) is not less than B is the investment constraint (plan configuration constraint, configuration capacity constraint), e (x) + f (x) is not less than g is the voltage inequality constraint, and r (x) + t (x) is the power flow balance equality constraint.

As long as the reactive compensation capacity investment variable x is determined, the actual operation parameter y can be determined through optimization of the system operation mode. Namely, the original problem can be regarded as the unification of two optimization processes, namely, the investment optimization process for determining the position and the size of the reactive configuration capacity is called as a main investment problem; and secondly, determining an operation optimization process which minimizes the operation cost under the existing configuration, which is called as an operation subproblem.

When any one of the determined capacities x is given^*And the optimal value D corresponding to the operation subproblem can be represented as w (x), the corresponding investment main problem and operation subproblem can be decomposed as follows:

(1) the main problems of investment are as follows:

Min C(x)+W(x)

s.t A(x)≥B

in the above formula, C (x) + W (x) is the total cost of investment, wherein W (x) is a link connecting the main problem and the subproblems, and A (x) ≧ B is the condition of investment constraint.

(2) The operation sub-problem:

W(x)＝minD(y)

s.t F(x)≥g-E(x^*)

T(y)＝h-R(x^*)

in the above formula, minD (y) is the cost of operation optimization, F (x) is not less than g-E (x)^*) For voltage inequality constraints, t (y) h-R (x)^*) Is a power flow balance equality constraint.

Obviously, the main investment problem and the running subproblems are closely related by using W (x), and the W (x) is modified by solving the running subproblems, so that a new linear constraint after modification is formed, and the main investment problem is returned. And solving the main problem and the sub problem alternately to obtain the optimal solution of the reactive compensation quantity.

Claims (5)

1. Reactive compensation loss reduction optimization method based on rural power grid typical distribution area line loss calculation is characterized in that: the method comprises the following steps:

step 1: analyzing the topological structure of the network, and acquiring accurate physical parameters by adopting a gradient search method to prepare for accurate line loss calculation; performing typical classification on the rural power grid transformer area according to different characteristics of the rural power grid typical transformer area, power supply radius, the service life of the type capacity of the transformer and data cleaning and mining of physical parameters of load distribution conditions;

step 2: calculating the loss of the rural power grid platform area by adopting an improved forward-push load flow method;

and step 3: establishing a reactive power optimization objective function and adding constraint conditions of voltage, power factor, compensation capacity and compensation equipment;

and 4, step 4: determining the compensation positions of reactive compensation of different types of typical transformer areas and the compensation capacity of each compensation device;

and 5: establishing a rural power grid platform area combined by multiple loss reduction measures;

step 6: establishing reactive compensation capacity of a decomposition coordination method;

the improved forward power flow method in the step 2 is that the voltage value of each node is more accurate and the calculated line loss value is more real by measuring and calculating the voltage value of the node and taking the average value of the obtained results;

the step 2 comprises the following steps: calculating the voltage value and the power value of the last node corresponding to each node by a forward method by acquiring the actual measurement data of each terminal load node, if the last node has no actual measurement value, calculating the voltage value obtained by forward calculation, and if the actual measurement value exists, taking the average value of the actual measurement value and the calculated value; if the last node corresponds to two load nodes, if the node has no measured value, taking the average value of the forward voltage of the two loads, otherwise, taking the average value of the three values, and so on; up to the root node; the result of line loss is equal to the total loss calculated by the transformer plus the total loss calculated on the line;

A_loss＝T_loss+L_loss

in the above formula A_lossFor all line losses, T_lossIs the loss of the transformer, L_lossLoss of the transmission line;

step 21: on the line impedance parameterUnder the known condition, the loss on a line between the load node and a superior node thereof and the voltage of the superior node can be accurately solved as long as the effective values of the active power, the reactive power and the voltage of the load node are measured, and the complex multiplication and division are avoided by calculating the line loss and the node voltage; line l between nodes 2 and 3_2-3Impedance of each phase is Z_2-3＝R_2-3+jX_2-3While measuring the three-phase output power P of the node 3₃+jQ₃The effective value of the line voltage is U₃；

Line l_2-3The active power loss in (c) is:

in the above formula,. DELTA.P_2-3Refers to the line l_2-3Active power loss on; p₃Is the active power of node 3, Q₃Is the reactive power of node 3; u shape₃Is the voltage of node 3, R_2-3Is a line l_2-3A resistance value of (d);

the reactive power loss is:

in the above formula,. DELTA.Q_2-3Refers to the line l_2-3Active power loss on; p₃Is the active power of node 3, Q₃Is the reactive power of node 3; u shape₃Is the voltage of node 3, R_2-3Is a line l_2-3A resistance value of (d);

the output power of node 2 is:

in the above formula, the first and second carbon atoms are,

refers to the output power of node 2; p₃Is the active power of node 3, Q₃Is the reactive power of node 3; delta P_2-3、ΔQ_2-3Respectively is a line l_2-3Upper loss active and reactive power;

effective voltage value U of node 2₂Comprises the following steps:

in the above formula, U₂Refers to the effective value voltage DeltaU of node 2_2-3、δU_2-3Is a line l_2-3The longitudinal and lateral components of the voltage drop;

step 22: assuming a certain region, the region has 11 nodes, the resistance and reactance between each node are known, and the active power, reactive power and voltage effective value of each load node are obtained through a data acquisition system;

the specific implementation steps of the algorithm are as follows:

(1) firstly, classifying and numbering nodes, and clearly distinguishing power supply nodes and load nodes; the power supply node is a node 0, and the load nodes are nodes 2, 3, 8, 9 and 10;

(2) calculating the voltage value and the power value of the last node corresponding to each node by a forward method by acquiring the actual measurement data of each terminal load node, if the last node has no actual measurement value, calculating the voltage value obtained by forward calculation, and if the actual measurement value exists, taking the average value of the actual measurement value and the calculated value; if the last node corresponds to two load nodes, if the node has no measured value, taking the average value of the forward voltage of the two loads, otherwise, taking the average value of the three values, and so on; up to the power supply node;

the line between nodes 8 and 6 is l_8-6Each impedance between the lines is Z_8-6＝R_8-6+jX_8-6The three measured output powers of the load 8 nodes are P₈+jQ₈Then line l_8-6Active power loss between:

in the above formula,. DELTA.P_8-6Is a line l_8-6Active power loss of P₈Is the active power of node 8, Q₈Reactive power of node 8, U₈Is the effective value of the voltage at node 8, R_8-6Is a line l_8-6Impedance in between; the reactive power loss is:

in the above formula,. DELTA.Q_8-6Is a line l_8-6Reactive power loss of P₈Is the active power of node 8, Q₈Reactive power of node 8, U₈Is the effective value of the voltage at node 8, X_8-6Is a line l_8-6Reactance between; the output power of node 6 is:

S₆＝P₆+jQ₆＝(P₈+ΔP_8-6)+j(Q₈+ΔQ_8-6)

in the above formula, S₆Refers to the output power of node 6; p₆Is the active power, Q, of node 6₆Is the reactive power of node 6; delta P_8-6、ΔQ_8-6Respectively is a line l_8-6Upper loss active and reactive power; p₈、Q₈Respectively, the active power and reactive power of node 8;

the voltage value at node 6 is:

in the above formula, U₈Is the effective value of the voltage at node 8, Δ U_8-6Is a line l_8-6Longitudinal component of voltage drop, δ U_8-6Is a line l_8-6The transverse component of the voltage drop;

wherein:

the same can pass through the line l_9-6Calculating the voltage and the output power of the node 6, if the voltage value and the output power of the node 6 can be measured, calculating the average value of the voltage value and the output power of the node 6 to obtain the voltage value and the power value of the node 6, and if the voltage value and the power value of the node 6 are not measured, calculating the average value of the voltage value of the node 6 and calculating the average value of the power value;

(3) marking the calculated lines, and continuously searching unmarked lines until all the lines are calculated;

(4) calculating the loss of all the public transformers, and calculating the copper loss and the iron loss of the transformers by using the actually measured node load and voltage values during calculation; therefore, the influence of load and voltage is fully considered in transformer loss calculation;

(5) total line loss:

A_loss＝T_loss+L_loss

wherein A is_lossFor all line losses, T_lossIs the loss of the transformer, L_lossLoss of the transmission line; the step 5 comprises the following steps:

step 51: firstly, determining loss reduction measures of rural power grid transformer area and recording the loss reduction measures as X_iWherein i is 1,2,. 4; x₁～X₄The method corresponds to four rural power grid district loss reduction measure types of reactive compensation, three-phase unbalance improvement, transformer capacity replacement and line section area replacement; on the basis, the possible implementation scheme of a certain type of loss reduction measures is taken as the loss reduction scheme in the loss reduction of the rural power grid distribution area, namely the possible implementation scheme is the loss reduction scheme

J possible embodiments representing the ith category of impairment mitigation measures; x₁The loss reduction scheme corresponding to the loss reduction measures comprises a transformer station centralized compensation device, a user decentralized control device and an optimized reactive compensation device; x₂The loss reduction scheme corresponding to the loss reduction measures comprises the steps of changing the phase sequence of the wiring of a client, a three-phase unbalanced voltage regulator and an autotransformer; x₃The loss reduction scheme corresponding to the loss reduction measure comprises a capacity reduction transformation method, an economic operation mode of the transformer and an energy-saving transformer; x₄The loss reduction scheme corresponding to the loss reduction measure comprises the steps of parallel bunched conductors, increase of the sectional area of the conductors and line insulation transformation;

for loss reduction measure X_iBecause of the existence of loss influence factor analysis, the loss reduction measure type with larger weight is selected from the loss reduction measure influence weight evaluation analysis result to be used as an alternative loss reduction measure to be implemented on the current rural power grid platform area, so that the loss reduction measure X is implemented_iWhether selected may be described by the following equation;

aiming at the selected loss reduction measures, possible loss reduction measures can be further considered to implement the project, namely the possible loss reduction project

Aiming at the description of the implementation principle of the loss reduction measures of the rural power grid district, various selectable implementation items are provided for each type of loss reduction measure according to manual experience and different existing optimization algorithms, and the following formula is a description of whether the jth loss reduction item in the ith loss reduction measure is selected or not;

step 52: in order to ensure that the loss reduction achieves a better effect, a loss reduction alternative scheme is formed through the following steps;

the loss reduction alternative scheme is formed by combining loss reduction projects, and due to the existence of loss influence factor analysis of the rural power grid transformer area, main influence factors influencing the technical loss of the rural power grid transformer area in the current rural power grid transformer area and corresponding types of loss reduction measures can be preliminarily determined, so that the selection condition of the loss reduction measures can be determined when the loss reduction alternative scheme is generated, and the selected loss reduction measures after the loss analysis are assumed to be X_a、X_b、X_cThen, the structure of the loss reduction option in this case is as follows:

under the condition that the implementation items of each type of loss reduction measure are determined, one loss reduction candidate item is the combination of the selected loss reduction items, and the loss reduction items are met

Mutual exclusivity between them, as shown by the following formula:

in the above formula: f. of_iThe ith loss reduction candidate item is pointed; g refers to the mutual exclusivity among loss reduction projects, namely the constraint that the implementation of different implementation projects of the same type of loss reduction measures in the rural power grid area cannot occur simultaneously; mutual exclusion relation constraint among projects is mainly embodied in a loss reduction decision flow;

the generation flow of the loss reduction alternative item of the rural power grid district is as follows:

(1) determining loss influence factors playing a key important role in the technical line loss of the rural power grid platform area through rural power grid platform area loss analysis;

(2) based on sensitivity analysis, determining loss reduction measure X in rural power grid platform area optimization decision_iSelecting the condition;

(3) for each selected loss reduction measure X_iAlternative loss reduction projects are obtained through research of weight analysis of measure schemes

(4) Generating initial rural power grid distribution area loss reduction alternative item f according to various combinations of loss reduction items_i；

Step 53: in the rural power grid distribution area loss reduction decision model, comprehensive benefits of loss reduction electric quantity brought by loss reduction measures to the current rural power grid distribution area are fully reflected, and the rural power grid distribution area loss reduction optimization decision model containing a decision objective function and decision constraint conditions is established by analyzing investment benefit evaluation;

(1) a decision-making objective function;

in order to comprehensively optimize the benefits obtained by reducing the construction and operation costs and the power consumption of the rural power grid transformer area, under the support of a life cycle cost theory, an objective function is established, wherein the objective function comprises the comprehensive cost, the loss reduction cost, the operation and maintenance cost, the fault cost, the removal and recovery cost and the power selling cost caused by the power consumption of the rural power grid transformer area within the operation period;

(2) constraint conditions of the decision:

the constraint conditions of the rural power grid distribution area loss reduction optimization decision model comprise six contents: power supply reliability constraint, user average power failure time constraint, voltage deviation constraint, line transmission constraint, investment limit constraint and inter-project mutual exclusion relationship constraint;

power supply reliability constraint: the power supply reliability is not lower than a preset specified limit value;

constraint of average power failure time of users: the average power failure time of a user does not exceed a preset specified limit value;

voltage deviation constraint: the absolute value of the voltage deviation should not exceed 7% of the standard voltage;

fourthly, line transmission constraint: the actual transmission capacity of the line should not exceed its maximum transmission capacity, generally expressed in terms of transmission current;

investment restriction constraint: the investment limit constraint means that the investment of a loss reduction scheme adopting a plurality of loss reduction measure combinations is within a preset investment limit, and the loss reduction scheme investment mainly aims at loss reduction cost;

(3) investment benefit evaluation indexes are as follows:

according to the basic steps of technical-economic comparison and evaluation, for the rural power grid loss reduction and energy conservation transformation project, corresponding technical indexes are firstly determined, and then the technical indexes are preferentially selected according to economic indexes in a qualified scheme; the specific technical indexes of the loss reduction scheme comprise electric energy loss rate, voltage qualification rate, power factor and service life;

according to the economic technology assessment in the rural power network planning and design guide rule, the economic indexes of the specified loss reduction scheme comprise an investment recovery period, a net present value, a net annual value, a net present value rate and an internal yield rate;

(4) and (3) decision of the loss reduction optimization scheme:

the decision of the loss reduction scheme aims to optimize a loss reduction scheme set comprising various selection possibilities of loss reduction measures and determine a loss reduction measure combination and a loss reduction implementation scheme with optimal comprehensive benefits.

2. The reactive compensation loss reduction optimization method based on rural power grid typical transformer area line loss calculation according to claim 1, which is characterized in that: the step 1 comprises the following steps: classifying the loads of the power distribution network according to the network structure and the switch running state of the power distribution network system, and performing gradient search according to different loads and measured values to obtain parameters of each branch of the system and voltage, active power and reactive power of nodes;

the active power, reactive power and voltage values of a main transformer and a distribution transformer in a distribution feeder line are searched in a first gradient mode;

performing a second gradient search on the transformer which cannot obtain real-time measurement, and performing line loss calculation by using a state estimation method in order to obtain complete operation parameters with accuracy meeting requirements;

and after the number of the transformers is searched, performing third gradient search, and searching each node on the user, the overhead line and the cable line to form a node matrix.

3. The reactive compensation loss reduction optimization method based on rural power grid typical transformer area line loss calculation according to claim 1, which is characterized in that: the objective function in step 3:

min(P₁-P₂)

wherein P1 is investment cost, P2 is loss reduction profit, and the objective function is the minimum value of the difference value of the two;

wherein:

in the above formula, n is the total number of node compensation devices; n is a radical of_iThe number of groups of the compensating capacitor of the ith equipment; ci is the capacity of a single group of capacitors corresponding to the compensation equipment; ma is the unit price of the compensation capacity; mb is a single set price for the compensation device; mc is the cost invested in installing the equipment;

wherein:

P₂＝(f₁-f₂)·c·T

in the above formula, f₁To compensate for the previous power loss, f₂For the compensated power loss, c is the corresponding electricity price, T time of operation;

the method comprises the following steps: the reactive compensation decentralized configuration optimization model of the low-voltage power distribution network is as follows by taking the active loss of the minimum low-voltage power distribution network as a target:

min f(x)

s.t h(x)＝0,

in the above formula: the objective function f (x) is the difference value of the investment cost and the loss reduction profit; h (x) is a power balance equation of each node, x is a decision variable and a state variable of the system, the decision variable is a parallel reactive compensation capacity Q of a reactive compensation point, and the state variable comprises a voltage amplitude V and a phase angle delta of each node; the inequality constraint l (x) comprises upper and lower limit constraints of voltage amplitude of each node, upper and lower limit constraints of parallel reactive compensation capacity of each reactive compensation point, upper and lower limits of power factor and upper and lower limits of compensation equipment grouping number;

the difference between the investment cost and the loss reduction profit is an objective function f (x), and the expression is as follows:

f(x)＝P₁-P₂

step 32: the constraint condition; the equation constraint h (x) is expressed as:

the following can be obtained from the power flow calculation equation:

in the above formula, P_iAnd Q_iActive power and reactive power injected into the transformer area respectively, wherein the inflow is positive, the outflow is negative, and Q is_ciFor compensating reactive power, V_iIs the voltage amplitude of node i, δ_ijIs the voltage phase angle difference between node i and node j, G_ijAnd B_ijRespectively a real part and an imaginary part of j columns of elements in the ith row of the network node admittance matrix, wherein n is the total number of the nodes in the transformer area;

the inequality constraint l (x) is expressed as:

in the above formula V_imin、V_imaxIs the minimum and maximum voltage allowed by the node, Q_cimin、Q_cimaxIs the minimum reactive power allowed by the node and the maximum reactive compensation power, rho_imi_n、ρ_imaxAre the maximum and minimum power factors allowed at the node measurement,

the minimum packet number and the maximum packet number for the switching of the compensation equipment.

4. The reactive compensation loss reduction optimization method based on rural power grid typical transformer area line loss calculation according to claim 1, which is characterized in that: the step 4 comprises the following steps:

step 41: firstly, calculating compensation quantity required by all nodes in a typical rural transformer area, calculating total reactive compensation capacity required by the transformer area, carrying out reactive compensation on each node, wherein the reactive compensation is not in accordance with the reality, and selecting important nodes with large load power as nodes needing compensation by using a sensitivity analysis method and a human factor method; setting 2 genes on a chromosome of each compensation device in the population by using a genetic algorithm, respectively representing the group number of the compensation devices and each group of compensation capacity, and calculating the optimal reactive compensation capacity of the node;

step 42: when calculating reactive power configuration optimization of different types of distribution areas on the basis of the step 41, firstly defining three electrical characteristic index circuit distribution transformation average load rate alpha, natural power factor cos phi, power supply radius L and reactive power compensation rate beta, and setting typical rural electrical indexes as ground state values according to rural power planning design guide rules and a specific electrical characteristic index system of local rural areas;

in the above formula, beta₀Is the optimal reactive compensation rate, W, of a typical rural area_nReactive configuration capacity, S, to be supplemented for the area_NThe rated capacity of the platform area;

when the reactive power compensation capacity of the random distribution area is calculated, the change condition of the optimal reactive power compensation rate is recorded by respectively changing each electrical characteristic index, the change degree of the reactive power compensation rate is represented by the size of sensitivity, the size of the sensitivity is equal to the change of the reactive power compensation rate corresponding to each electrical characteristic change, in the reactive power capacity configuration of the random distribution area, the difference value of the actual value of each electrical characteristic value and the electrical characteristic corresponding to the typical distribution area is used as a decision, and corresponding weighting calculation is carried out by using the size of the sensitivity;

in the above formula beta₀Is the reactive compensation rate of a typical distribution area, Δ m_iTo followDifference, lambda, between the electrical characteristic values of the machine area and the typical area_iThe sensitivity corresponding to the electrical characteristic value.

5. The reactive compensation loss reduction optimization method based on rural power grid typical transformer area line loss calculation according to claim 1, which is characterized in that: the step 6 comprises the following steps:

step 61: setting the reactive compensation capacity calculated in the step 4 as c₁And the reactive compensation capacity calculated in the step 5 is c₂If the difference value calculated by the two is less than the set margin epsilon, taking the reactive compensation capacity as c₁If the difference value of the two is larger than the set margin, establishing a decomposition coordination method to solve the reactive compensation capacity; decomposing an original target function into two mutually-connected sub-target functions; the two sub-target functions interact with each other to jointly optimize and calculate the final reactive compensation capacity;

step 62: firstly, establishing a mathematical model:

min C(x)+D(x)

s.t A(x)≥B

E(x)+F(x)≥g

R(x)+T(x)＝h

in the above formula, x is the configured reactive compensation capacity, y is the actual operation parameter of the power grid under the existing configuration, c (x) + d (x) is the cost for configuring the reactive power supply, a (x) is not less than B is the investment constraint (plan configuration constraint, configuration capacity constraint), e (x) + f (x) is not less than g is the voltage inequality constraint, and r (x) + t (x) is the tidal current balance equality constraint;

as long as the reactive compensation capacity investment variable x is determined, the actual operation parameter y can be determined through optimization of the system operation mode; namely, the original problem can be regarded as the unification of two optimization processes, namely, the investment optimization process for determining the position and the size of the reactive configuration capacity is called as a main investment problem; secondly, determining an operation optimization process which minimizes the operation cost under the existing configuration, which is called as an operation sub-problem;

when any one of the determined capacities x is given^*And the optimal value D corresponding to the operation subproblem can be represented as w (x), the corresponding investment main problem and operation subproblem can be decomposed as follows:

(1) the main problems of investment are as follows:

Min C(x)+W(x)

s.t A(x)≥B

in the above formula, C (x) + W (x) is the total cost of investment, wherein W (x) is a link connecting the main problem and the subproblems, and A (x) ≧ B is the condition of investment constraint;

(2) the operation sub-problem:

W(x)＝minD(y)

s.t F(x)≥g-E(x*)

T(y)＝h-R(x^*)

in the above formula, minD (y) is the cost of operation optimization, F (x) is not less than g-E (x)^*) For voltage inequality constraints, t (y) h-R (x)^*) Constraint for power flow balance equality;

obviously, the main investment problem and the sub-operation problem are closely related by using W (x), the correction of W (x) is provided by solving the sub-operation problem, a new linear constraint after the correction is formed, then the main investment problem is returned, the main problem and the sub-problem are alternately solved, and the optimal solution of the reactive compensation quantity is obtained.

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