CN113591397A - Power frequency electric field control method and system for alternating current overhead transmission line - Google Patents
Power frequency electric field control method and system for alternating current overhead transmission line Download PDFInfo
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Abstract
The invention provides a power frequency electric field control method and a power frequency electric field control system for an alternating current overhead transmission line, wherein the method comprises the following steps: establishing a three-dimensional power frequency electric field calculation model of the alternating current transmission line according to an overhead transmission line catenary equation; the method comprises the following steps of erecting a shielding line scheme at a proper position below an alternating-current transmission line, substituting the shielding line scheme into a three-dimensional power frequency electric field calculation model of the alternating-current transmission line, and calculating the environment-sensitive target power frequency electric field intensity of the shielding line scheme by using an improved simulation charge method; and setting the power frequency electric field at the environment sensitive target as an objective function to be optimized by adopting a genetic algorithm, solving the minimum value of the objective function, and taking the objective function as a solved fitness function. The method can organically combine environmental benefits and economic benefits, comprehensively find the optimal scheme by combining the construction cost and the shielding effect, and provide reference for engineering design and the control scheme of the power frequency electric field of the alternating current overhead transmission line.
Description
Technical Field
The invention relates to the technical field of electromagnetic pollution prevention and control of alternating current transmission lines, in particular to a power frequency electric field control method and a power frequency electric field control system for an alternating current overhead transmission line.
Background
With the development of social economy and the acceleration of urbanization, in order to meet the increasing demand of power load, in recent years, the scale of power transmission and transformation construction is steadily increased, various high-voltage power transmission lines are closer to public activity areas and inevitably close to residential houses, electromagnetic influence is generated on residents nearby along the power transmission lines, in recent years, environmental complaints and disputes caused by the power transmission lines are increased, and the phenomenon that a power frequency electric field exceeds the standard appears in part of environment sensitive targets close to the power transmission lines, so that the power transmission and transformation construction method becomes a focus problem of attention of ecological environment protection departments and power departments.
When an unfinished power transmission line is close to an environment sensitive point, comprehensive measures such as increasing the height of a tower, optimizing phase sequence arrangement, reducing the number of splits, changing the distance between leads, being far away from the environment sensitive point and the like can be taken in the design stage to ensure that the electromagnetic environment at the environment sensitive target meets the public exposure control limit requirement in electromagnetic environment control limit (GB 8702-2014). However, the measures are difficult to implement when the electromagnetic environment of the established power transmission line exceeds the standard, and the measures such as shielding lines and the like can be adopted to avoid power failure and high cost investment caused by the reconstruction of the existing line or reduce the social problems caused by the removal and the like.
Therefore, for the problem that the power frequency electric field under the power transmission line exceeds the standard, an optimal control scheme needs to be provided, and a basis is provided for engineering designers and the control of the power frequency electric field of the alternating current overhead power transmission line.
Disclosure of Invention
The invention provides a method and a system for controlling a power frequency electric field of an alternating current overhead transmission line, aiming at solving the problem that the power frequency electric field of the alternating current transmission line exceeds the standard. The method can organically combine environmental benefits and economic benefits, comprehensively find the optimal scheme by combining the construction cost and the shielding effect, and provide reference for engineering design and the control scheme of the power frequency electric field of the alternating current overhead transmission line.
In order to achieve the purpose, the invention adopts the following technical scheme:
a power frequency electric field control method for an alternating current overhead transmission line comprises the following steps:
establishing a three-dimensional power frequency electric field calculation model of the alternating current transmission line according to an overhead transmission line catenary equation;
the method comprises the following steps of erecting a shielding line scheme at a proper position below an alternating-current transmission line, substituting the shielding line scheme into a three-dimensional power frequency electric field calculation model of the alternating-current transmission line, and calculating the environment-sensitive target power frequency electric field intensity of the shielding line scheme by using an improved simulation charge method;
and setting the power frequency electric field at the environment sensitive target as an objective function to be optimized by adopting a genetic algorithm, solving the minimum value of the objective function, and taking the objective function as a solved fitness function.
The catenary equation of the overhead transmission line is as follows:
wherein z (x) is the height from ground of a point on the overhead transmission line; sigma0Is the horizontal stress of the wire; gamma is the specific load of the lead; l is a horizontal span; h is a height difference; h is the vertical distance between the hanging point and the ground; f. ofxIs a wire sag; lOA、lOBThe horizontal distance from the lowest point of the wire to the suspension point.
As a further improvement of the present invention, the calculation of the power frequency electric field strength of the environmental sensitive target of the shielded wire scheme by using the improved analog charge method specifically includes:
let the density be τmSimulation frameThe charge of the empty wire is uniformly distributed in the n-th conducting wiremSegment of potential generated at spatial Q point (x, y, z)
Is composed of
In the formula, epsilon0Is a vacuum dielectric constant; r ism、rm' the distance from the source point and its mirror image to the field point, respectively;
the potential coefficient is
Thereby obtaining a lead wire lmPotential coefficient generated by segment at Q point
In the formula, xm、ymRespectively is the nth wiremX, y axis coordinates of the segment; rhom、ρm' the distances from the source point and its mirror image to the point Q, respectively;
the potential generated by the transmission line at the space Q point is the result of the combined action of all line charges, and then the charge density is calculated according to the known potential of the wire surface matching point
τ＝P-1U
Wherein τ is a charge density column vector; p is a potential coefficient matrix; u is each conductor voltage column vector;
thereby obtaining the electric field intensity vector of the Q point
In the formula (I), the compound is shown in the specification,
is the n-th wiremThe potential generated by the segment; ex、Ey、EzX, y, z3 directional components of the electric field, respectively; e.g. of the typex、ey、ezUnit vectors in x, y, z3 directions, respectively; n is the number of phase lines; n is0The number of overhead ground wires;
the effective value of the electric field strength at the Q point is
As a further improvement of the present invention, the power frequency electric field at the environment sensitive target is set as an objective function to be optimized, specifically:
wherein, f (X) -is the objective function; e-power frequency electric field intensity; x-an optimized variable solution vector; d is the outer diameter of the shielded wire; l is the length of the shielded wire; pxThe lateral position of the shield wire in the system; pyThe longitudinal position of the shield wire in the system; gi(X) -the ith constraint; n is the number of constraint conditions;
and each variable is given a certain value range by combining with the actual engineering.
As a further improvement of the present invention, the genetic algorithm specifically comprises:
randomly generating an initial population pop (t), wherein the evolution generation number t is 1, the number of individuals is N, and each individual is composed of gene codes of chromosomes;
calculating the fitness f of each individual pop (t) in the population according to the following formula (a)iAnd judging whether the optimization criterion is met. If the data are in accordance with the optimal solution, outputting the optimal individual and the optimal solution represented by the optimal individual, and finishing the calculation; otherwise, carrying out the next step;
fi＝fitness(popi(t)) (a)
selecting regeneration individuals from the population pop (t) according to the probability distribution of the following formula (b), wherein individuals with high fitness are selected with high probability, and individuals with low fitness are possibly eliminated to form a new population (c):
newpop(t+1)＝{popj(t)|j＝1,2,...,N|} (c)
generating a new population crosstop (t +1) according to the cross probability Pc and a certain cross method;
and generating a new population mutpop (t +1) according to the variation probability Pm and a certain variation method.
Generating a new generation of population pop (t) ═ mutpop (t) by an evolution algebra t ═ t +1, and returning to calculate the fitness f of each individual pop (t) in the populationi。
As a further improvement of the present invention, the initial population is first subjected to initialization optimization data, where the initialization optimization data includes an outer diameter of a shield wire, a length of the shield wire, a transverse position of the shield wire, and a longitudinal position of the shield wire.
As a further improvement of the invention, the convergence criterion of the genetic algorithm is that the optimal results of two consecutive times are the same, namely the iteration number results, and the optimal scheme is output.
An alternating current overhead transmission line power frequency electric field control system, comprising:
the model establishing module is used for establishing a three-dimensional power frequency electric field calculation model of the alternating current transmission line according to an overhead transmission line catenary equation;
the electric field calculation module is used for erecting a shielding line scheme at a proper position below the alternating current transmission line, substituting the shielding line scheme into a three-dimensional power frequency electric field calculation model of the alternating current transmission line, and calculating the strength of an environment-sensitive target power frequency electric field of the shielding line scheme by using an improved analog charge method;
and the genetic algorithm module is used for setting the power frequency electric field at the environment sensitive target as a target function to be optimized by adopting a genetic algorithm, solving the minimum value of the target function and taking the target function as a solved fitness function.
An electronic device comprises a memory, a processor and a computer program which is stored in the memory and can run on the processor, wherein the processor executes the computer program to realize the steps of the alternating current overhead transmission line power frequency electric field control method.
A computer-readable storage medium storing a computer program which, when executed by a processor, implements the steps of the alternating current overhead transmission line power frequency electric field control method.
The invention has the beneficial effects that:
according to the method, firstly, a three-dimensional power frequency electric field calculation model of the alternating current transmission line is established according to a catenary equation of the overhead transmission line, then, the three-dimensional power frequency electric field distribution of the alternating current transmission line is calculated by adopting an improved analog charge method, finally, the power frequency electric field at an environment-sensitive target is set as a target function to be optimized by applying the overall optimization design idea of a genetic algorithm, optimization is carried out in the whole solution space at the same time, and the optimal scheme for erecting the shielding line is found out. The optimization method can simultaneously perform optimization in the whole solution space, has global optimal search capability, and can find the scheme with the optimal shielding effect in the shortest time. The optimization method can also bring the construction cost into the optimization scheme, organically combine the environmental benefit and the economic benefit under the condition of meeting the requirement of the power frequency electric field standard limit value, and comprehensively find the optimal scheme by combining the construction cost and the shielding effect, thereby providing reference for engineering design and the power frequency electric field control scheme of the alternating current overhead transmission line.
Drawings
Fig. 1 is a schematic flow chart of a power frequency electric field control method for an alternating current overhead transmission line according to a preferred embodiment of the invention.
FIG. 2 is a schematic catenary view of the present invention.
Where z (x) is the ground height, m, of a point of the overhead transmission line; sigma0Is the horizontal stress (i.e., the stress at the lowest point) of the conductive line, N/mm2(ii) a Gamma is the specific load of the wire (i.e. the load per unit length and unit cross section), N/(m mm)2) (ii) a l is the horizontal span (horizontal distance between two suspension points), m; h is height difference (vertical distance between two suspension points), m; h is the vertical distance between the hanging point and the ground, m; f. ofxIs a wire sag; lOA、lOBThe horizontal distance from the lowest point of the wire to the suspension point.
Fig. 3 is a system block diagram of the power frequency electric field control and optimization method of the alternating current overhead transmission line of the invention.
Fig. 4 is a schematic structural diagram of a power frequency electric field control system of an alternating current overhead transmission line in the preferred embodiment of the invention.
Fig. 5 is a schematic structural diagram of an electronic device according to a preferred embodiment of the invention.
Detailed Description
The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings. It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.
The following detailed description is exemplary in nature and is intended to provide further details of the invention. Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention.
As shown in fig. 1, a first object of the present invention is to provide a method for controlling a power frequency electric field of an ac overhead transmission line, comprising the following steps:
establishing a three-dimensional power frequency electric field calculation model of the alternating current transmission line according to an overhead transmission line catenary equation;
the method comprises the following steps of erecting a shielding line scheme at a proper position below an alternating-current transmission line, substituting the shielding line scheme into a three-dimensional power frequency electric field calculation model of the alternating-current transmission line, and calculating the environment-sensitive target power frequency electric field intensity of the shielding line scheme by using an improved simulation charge method;
and setting the power frequency electric field at the environment sensitive target as an objective function to be optimized by adopting a genetic algorithm, solving the minimum value of the objective function, and taking the objective function as a solved fitness function.
Firstly, dividing an overhead transmission line conductor, a ground wire and a shielding wire into a plurality of finite-length line segments, carrying out mirror image processing on the ground, solving a potential coefficient generated by each finite-length line segment at each matching point, and establishing an equation by taking the known potential as a boundary condition:
in the formula, P is a potential coefficient matrix; tau is the column vector of the analog charge density to be solved;
is a matching point potential column vector.
The power frequency electric field intensity of any point to be solved in space can be deduced through division of overhead transmission line conducting wires, ground wires and shielding wires and solving of analog charges.
Specifically, a three-dimensional power frequency electric field calculation model of the alternating current transmission line is established according to an overhead transmission line catenary equation. And calculating the three-dimensional power frequency electric field of the alternating current transmission line by adopting an improved analog charge method. The power frequency electric field of the alternating current overhead transmission line is controlled by setting a shielding line, and the strength of the environment sensitive target power frequency electric field after the shielding line is set is calculated, namely the shielding effect.
And introducing a genetic algorithm, setting the power frequency electric field at the environment sensitive target as an objective function to be optimized, solving the minimum value of the optimization function, and taking the objective function as a solved fitness function. And (4) carrying out range constraint on each optimization variable by combining with engineering practice.
Based on the genetic algorithm overall optimization design idea, initializing optimization data including the outer diameter of the shielded wire, the length of the shielded wire, the transverse position of the shielded wire, the longitudinal position of the shielded wire and the like, and finding out the optimal scheme of the shielded wire which meets the program end condition through a series of fitness calculation, selection, crossing, variation and the like.
When the three-dimensional power frequency electric field of the alternating current transmission line is calculated based on the improved analog charge method, the lightning conductor and the shielding line are both well grounded, and the ground voltage can be regarded as the large ground voltage, namely the zero potential.
The method of the present invention is described in detail below with reference to the accompanying drawings:
and establishing a three-dimensional power frequency electric field calculation model of the alternating current transmission line according to the catenary equation of the overhead transmission line.
According to the stress balance condition, the catenary equation of the overhead transmission line shown in the attached figure 2 can be obtained:
wherein z (x) is the height from ground of a point on the overhead transmission line, m; sigma0Is the horizontal stress (i.e., the stress at the lowest point) of the conductive line, N/mm2(ii) a Gamma is the specific load of the wire (i.e. the load per unit length and unit cross section), N/(m mm)2) (ii) a l is the horizontal span (horizontal distance between two suspension points), m; h is height difference (vertical distance between two suspension points), m; h is the vertical distance between the hanging point and the ground, m; f. ofxIs a wire sag; lOA、lOBThe horizontal distance from the lowest point of the wire to the suspension point.
Calculating the three-dimensional power frequency electric field of the alternating current transmission line by adopting an improved analog charge method:
let the density be τmThe analog overhead line charges are uniformly distributed in the n-th conductormSegment of potential generated at spatial Q point (x, y, z)
Is composed of
In the formula, epsilon0Is a vacuum dielectric constant; r ism、rm' is the distance of the source point and its mirror to the field point, respectively.
The potential coefficient is
The formula (2) is substituted for the formula (3) to obtain the conducting wire lmPotential coefficient generated by segment at Q point
In the formula, xm、ymRespectively is the nth wiremX, y axis coordinates of the segment; rhom、ρm' is the distance of the source point and its mirror to the point Q, respectively.
The potential generated by the transmission line at the space Q point is the result of the combined action of all line charges, and the charge density can be calculated according to the known potential of the wire surface matching point
τ＝P-1U (5)
Wherein τ is a charge density column vector; p is a potential coefficient matrix; u is the column vector of each conductor voltage.
Thus, the electric field intensity vector of the Q point can be obtained
In the formula (I), the compound is shown in the specification,
is the n-th wiremThe potential generated by the segment; ex、Ey、EzX, y, z3 directional components of the electric field, respectively; e.g. of the typex、ey、ezUnit vectors in x, y, z3 directions, respectively; n is the number of phase lines; n is0The number of overhead ground wires.
The effective value of the electric field strength at the Q point is
In order to control the power frequency electric field intensity under the AC power transmission line, a shielding line scheme is erected at a proper position below the AC power transmission line, the shielding line scheme is substituted into the established three-dimensional power frequency electric field calculation model of the AC power transmission line, and the shielding effect of the shielding line scheme is calculated by using an improved analog charge method.
The genetic algorithm has inherent implicit parallelism, and the optimization search is carried out in the whole solution space at the same time instead of one line from one point, so that the genetic algorithm has good global optimal search capability. In addition, the genetic algorithm has another main characteristic that the genetic algorithm belongs to a randomized search algorithm, the optimization direction is established by directly utilizing the information of the target function, the search does not depend on gradient information, the requirements of derivation and function continuity do not exist, the limitation on the optimization design problem is less, and the method has wider applicability. Therefore, the genetic algorithm is applied to the power frequency electric field control system of the alternating current overhead transmission line, and the scheme with the optimal shielding effect is found in the shortest time.
The optimization method can also bring the construction cost into the optimization scheme, integrate the construction cost and the shielding effect and seek the optimal scheme, thereby providing reference for engineering design and the power frequency electric field control scheme of the alternating current overhead transmission line.
In order to find out an optimal control scheme, a genetic algorithm is introduced, a power frequency electric field at an environment sensitive target is set as a target function to be optimized, the minimum value of the optimization function is solved, and the target function is used as a solved fitness function. The mathematical expression of the optimization problem is:
wherein, f (X) -is the objective function; e-power frequency electric field intensity; x-an optimized variable solution vector; d is the outer diameter of the shielded wire; l is the length of the shielded wire; pxThe lateral position of the shield wire in the system; pyThe longitudinal position of the shield wire in the system; gi(X) -the ith constraint; n is the number of constraint conditions.
And (4) carrying out range constraint on each optimized variable, namely combining the engineering practice to give a certain value range to each variable.
Based on the genetic algorithm overall optimization design idea, initializing optimization data including the outer diameter of the shielded wire, the length of the shielded wire, the transverse position of the shielded wire, the longitudinal position of the shielded wire and the like, and finding out the optimal scheme of the shielded wire which meets the program end condition through a series of fitness calculation, selection, crossing, variation and the like.
Examples
The invention is further illustrated with reference to the following figures and examples.
And establishing a three-dimensional power frequency electric field calculation model of the alternating current transmission line according to the catenary equation of the overhead transmission line.
The method is characterized in that a three-dimensional power frequency electric field of an alternating current transmission line, particularly the power frequency electric field intensity at an environment sensitive target is calculated by using an improved analog charge based method, and compared with a standard (public exposure control limit value 4000V/m specified in electromagnetic environment control limit value (GB 8702-2014)), the superscalar of the power frequency electric field intensity at the environment sensitive target is determined.
In order to control the superscalar of the power frequency electric field intensity of the environment sensitive target, a shielding line scheme is erected at a proper position below the alternating current transmission line, a shielding line model is incorporated into a three-dimensional power frequency electric field calculation model of the transmission line, and the shielding effect of the shielding line scheme is calculated by the method.
In order to find an optimal power frequency electric field control scheme, a genetic algorithm is applied to a power frequency electric field control system of an alternating current overhead transmission line, a power frequency electric field (or superscalar) at an environment sensitive target is set as an objective function to be optimized, the factors influencing the power frequency electric field at the environment sensitive target are subjected to parameter coding, the minimum value of the objective function is solved, and the objective function is used as a solved fitness function. The mathematical expression of the optimization problem is:
wherein, f (X) -is the objective function; e-power frequency electric field intensity; x-an optimized variable solution vector; d is the outer diameter of the shielded wire; l is the length of the shielded wire; pxThe lateral position of the shield wire in the system; pyThe longitudinal position of the shield wire in the system; gi(X) -the ith constraint; n is the number of constraint conditions.
And (4) carrying out range constraint on each optimized variable, namely combining the engineering practice to give a certain value range to each variable.
As shown in fig. 3, an initial population pop (t) is randomly generated, the evolution passage number t is 1, the number of individuals is N, and each individual is composed of a gene code of a chromosome.
Calculating the fitness f of each individual pop (t) in the population according to the formula (12)iAnd judging whether the optimization criterion is met. If so, outputting the best individual and its representativeAnd ending the calculation; otherwise, turning to the next step;
fi＝fitness(popi(t)) (12)
according to the probability distribution of the formula (13), regeneration individuals are selected from the population pop (t), individuals with high fitness are selected with high probability, individuals with low fitness are possibly eliminated, and a new population is formed according to the formula (14):
newpop(t+1)＝{popj(t)|j＝1,2,...,N|} (14)
generating a new population crosstop (t +1) according to the cross probability Pc and a certain cross method;
generating a new population mutpop (t +1) according to the variation probability Pm and a certain variation method;
generating a new generation of population pop (t) ═ mutpop (t) by an evolution algebra t ═ t +1, returning to the formula (12), and calculating the fitness f of each individual pop (t) in the populationi。
Convergence criterion of the genetic algorithm: through multiple genetic operations such as selection, intersection, variation and the like, the excellent quality of each generation of population is gradually accumulated, the population average fitness and the optimal individual fitness continuously rise, and the iteration process tends to be convergent. The convergence criterion of the invention is that the optimal results of two consecutive times are the same, namely the iteration times result, and the optimal scheme is output.
When the construction cost is brought into the treatment scheme, the treatment scheme is optimized to be the scheme with the lowest construction cost under the condition of meeting the power frequency electric field standard limit value at the environment sensitive target, and the environmental benefit and the economic benefit can be organically combined.
Therefore, the invention provides a power frequency electric field control and optimization method of an alternating current overhead transmission line based on a genetic algorithm, which comprises the following steps: firstly, according to an overhead transmission line catenary equation, a three-dimensional power frequency electric field calculation model of the alternating current transmission line is established, then three-dimensional power frequency electric field distribution of the alternating current transmission line is calculated by adopting an improved analog charge method, finally, a shielded wire erecting method is adopted for power frequency electric field control measures under the alternating current transmission line, and a genetic algorithm is applied to the shielded wire erecting method. The optimization method can also bring the construction cost into the optimization scheme, organically combine the environmental benefit and the economic benefit under the condition of meeting the requirement of the power frequency electric field standard limit value, and comprehensively find the optimal scheme by combining the construction cost and the shielding effect, thereby providing reference for engineering design and the power frequency electric field control scheme of the alternating current overhead transmission line.
As shown in fig. 4, another objective of the present invention is to provide a power frequency electric field control system for an ac overhead transmission line, including:
the model establishing module is used for establishing a three-dimensional power frequency electric field calculation model of the alternating current transmission line according to an overhead transmission line catenary equation;
the electric field calculation module is used for erecting a shielding line scheme at a proper position below the alternating current transmission line, substituting the shielding line scheme into a three-dimensional power frequency electric field calculation model of the alternating current transmission line, and calculating the strength of an environment-sensitive target power frequency electric field of the shielding line scheme by using an improved analog charge method;
and the genetic algorithm module is used for setting the power frequency electric field at the environment sensitive target as a target function to be optimized by adopting a genetic algorithm, solving the minimum value of the target function and taking the target function as a solved fitness function.
As shown in fig. 5, a third object of the present invention is to provide an electronic device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the power frequency electric field control method for the ac overhead transmission line when executing the computer program.
The method for controlling the power frequency electric field of the alternating current overhead transmission line comprises the following steps:
establishing a three-dimensional power frequency electric field calculation model of the alternating current transmission line according to an overhead transmission line catenary equation;
the method comprises the following steps of erecting a shielding line scheme at a proper position below an alternating-current transmission line, substituting the shielding line scheme into a three-dimensional power frequency electric field calculation model of the alternating-current transmission line, and calculating the environment-sensitive target power frequency electric field intensity of the shielding line scheme by using an improved simulation charge method;
and setting the power frequency electric field at the environment sensitive target as an objective function to be optimized by adopting a genetic algorithm, solving the minimum value of the objective function, and taking the objective function as a solved fitness function.
A fourth object of the present invention is to provide a computer-readable storage medium, which stores a computer program, and the computer program, when executed by a processor, implements the steps of the method for controlling a power frequency electric field of an ac overhead transmission line.
The method for controlling the power frequency electric field of the alternating current overhead transmission line comprises the following steps:
establishing a three-dimensional power frequency electric field calculation model of the alternating current transmission line according to an overhead transmission line catenary equation;
the method comprises the following steps of erecting a shielding line scheme at a proper position below an alternating-current transmission line, substituting the shielding line scheme into a three-dimensional power frequency electric field calculation model of the alternating-current transmission line, and calculating the environment-sensitive target power frequency electric field intensity of the shielding line scheme by using an improved simulation charge method;
and setting the power frequency electric field at the environment sensitive target as an objective function to be optimized by adopting a genetic algorithm, solving the minimum value of the objective function, and taking the objective function as a solved fitness function.
As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.
Claims (10)
1. A power frequency electric field control method for an alternating current overhead transmission line is characterized by comprising the following steps:
establishing a three-dimensional power frequency electric field calculation model of the alternating current transmission line according to an overhead transmission line catenary equation;
the method comprises the following steps of erecting a shielding line scheme at a proper position below an alternating-current transmission line, substituting the shielding line scheme into a three-dimensional power frequency electric field calculation model of the alternating-current transmission line, and calculating the environment-sensitive target power frequency electric field intensity of the shielding line scheme by using an improved simulation charge method;
and setting the power frequency electric field at the environment sensitive target as an objective function to be optimized by adopting a genetic algorithm, solving the minimum value of the objective function, and taking the objective function as a solved fitness function.
2. The method of claim 1,
the catenary equation of the overhead transmission line is as follows:
wherein z (x) is the height from ground of a point on the overhead transmission line; sigma0Is the horizontal stress of the wire; gamma is the specific load of the lead; l is a horizontal span; h is a height difference; h is the vertical distance between the hanging point and the ground; f. ofxIs a wire sag; lOA、lOBThe horizontal distance from the lowest point of the wire to the suspension point.
3. The method of claim 1,
the method for calculating the power frequency electric field intensity of the environment-sensitive target of the shielded wire scheme by using the improved analog charge method specifically comprises the following steps:
let the density be τmThe analog overhead line charges are uniformly distributed in the n-th conductormSegment of potential generated at spatial Q point (x, y, z)
Is composed of
In the formula, epsilon0Is a vacuum dielectric constant; r ism、rm' the distance from the source point and its mirror image to the field point, respectively;
the potential coefficient is
Thereby obtaining a lead wire lmPotential coefficient generated by segment at Q point
In the formula, xm、ymRespectively is the nth wiremX, y axis coordinates of the segment; rhom、ρm' the distances from the source point and its mirror image to the point Q, respectively;
the potential generated by the transmission line at the space Q point is the result of the combined action of all line charges, and then the charge density is calculated according to the known potential of the wire surface matching point
τ＝P-1U
Wherein τ is a charge density column vector; p is a potential coefficient matrix; u is each conductor voltage column vector;
thereby obtaining the electric field intensity vector of the Q point
In the formula (I), the compound is shown in the specification,
is the n-th wiremThe potential generated by the segment; ex、Ey、EzX, y, z3 directional components of the electric field, respectively; e.g. of the typex、ey、ezUnit vectors in x, y, z3 directions, respectively; n is the number of phase lines; n is0The number of overhead ground wires;
the effective value of the electric field strength at the Q point is
4. The method of claim 1,
setting a power frequency electric field at an environment sensitive target as a target function to be optimized, specifically:
wherein, f (X) -is the objective function; e-power frequency electric field intensity; x-an optimized variable solution vector; d is the outer diameter of the shielded wire; l is the length of the shielded wire; pxThe lateral position of the shield wire in the system; pyThe longitudinal position of the shield wire in the system; gi(X) -the ith constraint; n is the number of constraint conditions;
and each variable is given a certain value range by combining with the actual engineering.
5. The method of claim 1,
the genetic algorithm specifically comprises:
randomly generating an initial population pop (t), wherein the evolution generation number t is 1, the number of individuals is N, and each individual is composed of gene codes of chromosomes;
calculating the fitness f of each individual pop (t) in the population according to the following formula (a)iJudging whether the optimization criterion is met; if the data are in accordance with the optimal solution, outputting the optimal individual and the optimal solution represented by the optimal individual, and finishing the calculation; otherwise, carrying out the next step;
fi＝fitness(popi(t)) (a)
selecting regeneration individuals from the population pop (t) according to the probability distribution of the following formula (b), wherein individuals with high fitness are selected with high probability, and individuals with low fitness are possibly eliminated to form a new population (c):
newpop(t+1)＝{popj(t)|j＝1,2,...,N|} (c)
generating a new population crosstop (t +1) according to the cross probability Pc and a certain cross method;
generating a new population mutpop (t +1) according to the variation probability Pm and a certain variation method;
generating a new generation of population pop (t) ═ mutpop (t) by an evolution algebra t ═ t +1, and returning to calculate the fitness f of each individual pop (t) in the populationi。
6. The method of claim 5,
the initial population is initialized and optimized with data, wherein the initialized and optimized data comprise the outer diameter of the shielding wire, the length of the shielding wire, the transverse position of the shielding wire and the longitudinal position of the shielding wire.
7. The method of claim 1,
the convergence criterion of the genetic algorithm is that the optimal results of two consecutive times are the same, namely the iteration times result, and the optimal scheme is output.
8. The utility model provides an exchange overhead transmission line power frequency electric field control system which characterized in that includes:
the model establishing module is used for establishing a three-dimensional power frequency electric field calculation model of the alternating current transmission line according to an overhead transmission line catenary equation;
the electric field calculation module is used for erecting a shielding line scheme at a proper position below the alternating current transmission line, substituting the shielding line scheme into a three-dimensional power frequency electric field calculation model of the alternating current transmission line, and calculating the strength of an environment-sensitive target power frequency electric field of the shielding line scheme by using an improved analog charge method;
and the genetic algorithm module is used for setting the power frequency electric field at the environment sensitive target as a target function to be optimized by adopting a genetic algorithm, solving the minimum value of the target function and taking the target function as a solved fitness function.
9. An electronic device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method for controlling the power frequency electric field of an ac overhead transmission line according to any one of claims 1 to 7 when executing the computer program.
10. A computer-readable storage medium storing a computer program which, when executed by a processor, implements the steps of the method of controlling a power frequency electric field of an ac overhead transmission line of any one of claims 1 to 7.
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