CN107169631B - Active power distribution network transformer substation planning method based on improved weighted Voronoi diagram - Google Patents

Active power distribution network transformer substation planning method based on improved weighted Voronoi diagram Download PDF

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CN107169631B
CN107169631B CN201710256654.4A CN201710256654A CN107169631B CN 107169631 B CN107169631 B CN 107169631B CN 201710256654 A CN201710256654 A CN 201710256654A CN 107169631 B CN107169631 B CN 107169631B
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transformer substation
substation
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capacity
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CN107169631A (en
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刘洪�
王博
郑楠
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Tianjin University
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Abstract

An active power distribution network transformer substation planning method based on an improved weighted Voronoi diagram comprises the following steps: evaluating the confidence capacity of the distributed power supply on the basis of considering the load characteristics, specifically calculating the size of the load supply capacity of the system under any load characteristics by the distributed power supply under the condition of maintaining the reliability level of the system unchanged; establishing a transformer substation optimization planning model considering the confidence capacity of the distributed power supply; a planning method based on an improved weighted Voronoi diagram is provided, and comprises the following steps: a hierarchical refinement to the weighted Voronoi diagram and a directional refinement to the weighted Voronoi diagram; and providing an optimization planning process of the transformer substation of the active power distribution network. The invention more accurately evaluates the confidence capacity of the distributed power supply; the speed of dividing the power supply range of the transformer substation by the weighted Voronoi graph algorithm is increased; the investment of the power grid can be effectively saved or delayed; the active power distribution network transformer substation planning can coordinate the relation between the distributed power supply load and the site selection and volume fixing of the newly-built transformer substation, and the integrated optimization of power supply reliability and economy is realized.

Description

Active power distribution network transformer substation planning method based on improved weighted Voronoi diagram
Technical Field
The invention relates to a planning method for an active power distribution network transformer substation. In particular to an active power distribution network transformer substation planning method based on an improved weighted Voronoi diagram and suitable for accessing a distributed power supply.
Background
The site selection and the volume fixing of the transformer substation are important links of power distribution network planning, and the result directly influences the network structure, the power supply reliability and the operation and maintenance economy of a future power distribution network. In recent years, China vigorously promotes the development and utilization of wind power and solar energy resources, the installed capacity of distributed power sources is continuously increased, and power systems are continuously developed towards low carbon, green and intelligent directions. Therefore, the capacity value of the distributed power supply is considered and participates in power and electricity quantity balance calculation, the relation between the distributed power supply load and the site selection and volume fixing of the newly-built transformer substation is well coordinated, the integrated optimization of power supply reliability and economy is realized, and the necessary foundation and the development direction of the optimization planning of the transformer substation are formed.
At present, the traditional theoretical research of substation planning is mature, and the related research after considering the distributed power supply access is mainly limited in the aspects of distribution planning of the distributed power supply, power distribution network extension planning of the distributed power supply and the like, and most of the research is on site selection and volume fixing of the distributed power supply. Although some documents research the collaborative planning problem of the distributed power supply and the site selection and volume fixing of the transformer substation. However, the documents do not establish an actual model for solving, and comprehensively consider the influence of the time sequence characteristics and the load characteristics of the distributed power supply output on the DG confidence capacity, so that the capacity value of the distributed power supply cannot be effectively evaluated; and the characteristic that the power supply radius of the transformer substation is increased in the DG direction is neglected by improving the Voronoi diagram, and the relationship between a distributed power supply and the supply load of a newly-built transformer substation cannot be reasonably coordinated.
Disclosure of Invention
The technical problem to be solved by the invention is to provide an active power distribution network transformer substation planning method based on an improved weighted Voronoi diagram, which can more scientifically and effectively play a role of DG confidence capacity in the division of the power supply range of the transformer substation.
The technical scheme adopted by the invention is as follows: an active power distribution network transformer substation planning method based on an improved weighted Voronoi diagram comprises the following specific steps:
1) evaluating the confidence capacity of the distributed power supply on the basis of considering the load characteristics, specifically calculating the size of the load supply capacity of the system under any load characteristics by the distributed power supply under the condition of maintaining the reliability level of the system unchanged;
2) establishing a transformer substation optimization planning model considering the confidence capacity of the distributed power supply;
3) a planning method based on an improved weighted Voronoi diagram is provided, and comprises the following steps: a hierarchical refinement to the weighted Voronoi diagram and a directional refinement to the weighted Voronoi diagram;
4) the method provides an active power distribution network transformer substation optimization planning process, which comprises the following steps:
(1) firstly, determining the number and capacity combination scheme of N newly-built substations according to target annual load, existing substation capacity and a given substation candidate capacity set in advance;
(2) the method comprises the steps that access of a distributed power supply is not considered, for each scheme, traditional substation planning is carried out on a planning area based on a weighted Voronoi graph algorithm, and a substation site and a power supply range of each substation are obtained as initial solutions;
(3) obtaining the distribution condition of the distributed power supply in each substation power supply range according to the planning result of the substation, and evaluating the confidence capacity of the distributed power supply in each substation power supply range by using a distributed power supply confidence capacity evaluation method considering load characteristics;
(4) on the basis of the existing distributed power supply confidence capacity, transformer substation planning is carried out on a planning area by using an improved weighted Voronoi graph algorithm, and a new transformer substation site and the power supply range of each transformer substation are obtained;
(5) the power supply range is correspondingly changed due to the movement of the substation address, the steps (3) and (4) are repeated until the confidence capacities of the movement of the substation address and the distributed power supply reach the set precision, and then the iteration is stopped to obtain a final result;
(6) and calculating the investment cost of the W schemes according to the optimized planning model of the transformer substation based on the capacity and site results of the transformer substation, sequencing the investment cost according to the cost, and selecting the scheme with the minimum cost as a final planning scheme.
The step 1) specifically comprises the following steps: the method comprises the following steps of selecting an electric power shortage expectation as a reliability index, wherein the electric power shortage expectation and the load size are in a monotonically increasing relation, and the reliability relation before and after the distributed power supply is added into a power distribution network is as follows:
f(G+GD>L+△L)＝f(G>L)＝r0 (1)
wherein f is a reliability estimation function; l and delta L are respectively the initial load and the newly added load of the system; gDG is the power generation capacity of the distributed power supply and the initial installed capacity of the system respectively; r is0The reliability index before power supply addition.
And solving the newly increased load delta L of the system by adopting a truncation method in a successive approximation mode, wherein the newly increased load delta L is the confidence capacity of the distributed power supply.
Step 2), after considering that the distributed power supply is connected to the power distribution network, the load of the power distribution network is shared by the transformer substation, the photovoltaic and the fan, and a new load inequality constraint is established by utilizing a confidence capacity evaluation result, so that a transformer substation optimization planning model is obtained:
Figure BDA0001273012620000021
in the formula: c is the total annual investment cost of the transformer substation; station is the annual cost of construction and maintenance of the transformer substation; the Feeder is the annual line investment cost of the low-voltage side of the transformer substation; CQ is the loss year cost of the low-voltage side line network of the transformer substation; piIs the load of the ith substation; siCapacity of the ith substation;
Figure BDA0001273012620000022
is the power factor; CC (challenge collapsar)PV(i) Confidence capacities of all photovoltaic power supplies in the power supply range of the ith transformer substation are obtained; CC (challenge collapsar)WTG(i) Confidence capacity of all fan power supplies in the power supply range of the ith transformer substation; j. the design is a squareiA set of loads supplied for the ith substation; n is the total number of the existing and newly-built transformer substations; j is the set of all load points; li,kIs the connection distance, R, between the ith substation and the kth loadiAnd (4) limitation of power supply radius for the ith substation.
And 3) the hierarchical improvement on the weighted Voronoi diagram is to complete each iteration of the weighted Voronoi diagram algorithm in 3 steps, namely, the power supply range of the transformer substation is expanded in three steps, wherein the weighted Voronoi diagram weight in each step of expansion is changed, and the weight depends on the load carried by the transformer substation and the capacity of the transformer substation. The specific weighted Voronoi diagram weight calculation formula is as follows:
Figure BDA0001273012620000031
in the formula:
Figure BDA0001273012620000032
respectively dividing speed and weight of the kth step in the jth iteration of the ith transformer substation;
Figure BDA0001273012620000033
the total load of the transformer substation after the 3 rd step division in the j-1 th iteration of the ith transformer substation is calculated;
Figure BDA0001273012620000034
the total load of the transformer substation after the 1 st step division in the jth iteration of the ith transformer substation is calculated;
Figure BDA0001273012620000035
the total load of the transformer substation after the 2 nd step division in the jth iteration of the ith transformer substation is calculated; the formula for the expansion range limit for three steps in each iteration is:
Figure BDA0001273012620000036
in the formula:
Figure BDA0001273012620000037
representing the speed of the kth division in the jth iteration of the ith substation;
Figure BDA0001273012620000038
standard distance for each step of dilation; dstationThe distance between each transformer substation;
Figure BDA0001273012620000039
for the jth stack of the ith substationExpanding range limitation of the 1 st step of generation;
Figure BDA00012730126200000310
representing the speed of the kth division in the jth iteration of the ith substation;
Figure BDA00012730126200000311
limiting the expansion range of the 2 nd step division in the jth iteration of the ith substation;
Figure BDA00012730126200000312
and limiting the expansion range of the 3 rd step division in the jth iteration of the ith substation.
The improvement on the directionality of the weighted Voronoi diagram in the step 3) specifically includes:
(1) determining the maximum power supply range of the transformer substation according to the capacity of the transformer substation and the load density around the transformer substation;
(2) determining the maximum power supply range of the distributed power supply according to the confidence capacity of the distributed power supply and the load density around the distributed power supply;
(3) taking the transformer substation A as a round point, taking the power supply range of the transformer substation A as a circle, and making two radiuses, wherein the two radiuses are respectively tangent to the circle formed by the power supply range of the distributed power supply B, the two radiuses are respectively intersected with the power supply range of the transformer substation A at an M point and a Z point, and the direction covered by a fan-shaped AMZ containing the power supply range of the distributed power supply B is regarded as the direction of increasing the power supply radius of the transformer substation A;
(4) selecting a point D on a connecting extension line of the transformer substation A and the distributed power supply B, drawing an arc line MEZ by taking DM AS a radius, enabling the area of the arc MEZ to be equal to the area of a circle formed by the power supply range of the distributed power supply B, calculating the position of the point D and the distance of the DM, and calculating the distance D of AS when a point S is selected from any point S on the arc MEZi,ASAfter the distributed power source B is added into the transformer substation A, the power supply radius in the AS direction, the expansion speed of the transformer substation and the weight calculation formula of the weighted Voronoi diagram are AS follows:
Figure BDA0001273012620000041
in the formula: v. ofASConsidering the expansion speed of the transformer substation A after DG for the AS direction; v is the expanding speed of the substation A without considering DG in the AS direction; dASDistance AS; dAMDistance of AM; omegaASAnd weighting the weighted Voronoi diagram weight of the AS direction substation A.
In the active power distribution network transformer substation planning method based on the improved weighted Voronoi diagram, the distributed power supply confidence capacity evaluation considers characteristic curves of different types of loads, and a single load model in the traditional method is replaced by diversified loads, so that the confidence capacity of the distributed power supply is more accurately evaluated; the hierarchical improvement of the weighted Voronoi diagram enables information interaction to be achieved twice in each iteration, the accuracy of division of the power supply range of the transformer substation in each iteration is enhanced, the success rate of one-time optimization is improved, and the speed of division of the power supply range of the transformer substation of the weighted Voronoi diagram algorithm is further improved; the directional improvement of the weighted Voronoi diagram ensures that the power supply range of the transformer substation is divided more reasonably, the DG confidence capacity is scientifically and effectively exerted, and the power grid investment can be effectively saved or delayed; the active power distribution network transformer substation planning can coordinate the relation between the distributed power supply load and the site selection and volume fixing of the newly-built transformer substation, and the integrated optimization of power supply reliability and economy is realized.
Drawings
FIG. 1 is a schematic diagram of a weighted Voronoi diagram directionality refinement;
FIG. 2 is a schematic view of a load type distribution;
FIG. 3 is a diagram of a conventional distribution network substation planning result;
fig. 4 is a schematic diagram of an active distribution network substation planning result based on a traditional Voronoi diagram;
fig. 5 is a schematic diagram of the active distribution network substation planning result based on the improved Voronoi diagram.
Detailed Description
The active power distribution network substation planning method based on the improved weighted Voronoi diagram is described in detail below with reference to examples and accompanying drawings.
The invention discloses an active power distribution network transformer substation planning method based on an improved weighted Voronoi diagram, which comprises the following specific steps of:
1) and evaluating the confidence capacity of the distributed power supply on the basis of considering the load characteristics.
Under the condition of maintaining the reliability level of the system unchanged, calculating the size of the load supply capacity of the system under any load characteristic by a Distributed Generation (DG); the method specifically comprises the following steps: the method comprises the following steps of selecting an electric power shortage expectation as a reliability index, wherein the electric power shortage expectation and the load size are in a monotonically increasing relation, and the reliability relation before and after the distributed power supply is added into a power distribution network is as follows:
f(G+GD>L+△L)＝f(G>L)＝r0 (1)
wherein f is a reliability estimation function; l and delta L are respectively the initial load and the newly added load of the system; gDG is the power generation capacity of the distributed power supply and the initial installed capacity of the system respectively; r is0The reliability index before power supply addition.
And solving the newly increased load delta L of the system by adopting a truncation method in a successive approximation mode, wherein the newly increased load delta L is the confidence capacity of the distributed power supply.
2) And establishing a model of the transformer substation optimization planning considering the confidence capacity of the distributed power supply.
The optimal planning problem of the substation can be described as that, under the condition that the planned target annual load distribution is known, in order to meet a certain load requirement, the load carrying capacity of the substation is taken as a constraint condition, and the number, the capacity and the position of the substations and the power supply range of the substation are determined by taking the approximate minimum investment and the annual operating cost (the annual cost of construction and maintenance of the substation, the annual cost of line investment on the low-voltage side of the substation and the annual cost of line loss on the low-voltage side of the substation) of the substation and a network as an objective function. Specifically, after the distributed power supply is connected to the power distribution network, the load of the power distribution network is jointly borne by the transformer substation, the photovoltaic and the fan, and a new load inequality constraint is established by using a confidence capacity evaluation result, so that a transformer substation optimization planning model is obtained:
Figure BDA0001273012620000051
in the formula: c is the total annual investment cost of the transformer substation; station is the annual cost of construction and maintenance of the transformer substation; the Feeder is the annual line investment cost of the low-voltage side of the transformer substation; CQ is the loss year cost of the low-voltage side line network of the transformer substation; piIs the load of the ith substation; siCapacity of the ith substation;
Figure BDA0001273012620000052
is the power factor; CC (challenge collapsar)PV(i) Confidence capacities of all photovoltaic power supplies in the power supply range of the ith transformer substation are obtained; CC (challenge collapsar)WTG(i) Confidence capacity of all fan power supplies in the power supply range of the ith transformer substation; j. the design is a squareiA set of loads supplied for the ith substation; n is the total number of the existing and newly-built transformer substations; j is the set of all load points; li,kIs the connection distance, R, between the ith substation and the kth loadiAnd (4) limitation of power supply radius for the ith substation.
3) A planning method based on an improved weighted Voronoi diagram is provided.
On the basis of the conventional Voronoi diagram definition, a weighted Voronoi diagram is defined as follows: let Q be { Q ═ Q1,q2,...,qn}，3≤n<Infinity is a set of points in the Euclidean space of the plane, ωi(i ═ 1,2, …, n) is n positive integers, then:
Figure BDA0001273012620000053
in the formula: d (x, q)i)，d(x,qj) Representing a point x and q on a planeiAnd q isjA linear distance between, wherein qi≠qj，i≠j，ωiIs a control point qiThe weight of (2).
The invention relates to an improvement of a Voronoi diagram, which specifically comprises the following steps: a hierarchical refinement to weighted Voronoi diagrams and a directional refinement to weighted Voronoi diagrams.
The hierarchical improvement of the weighted Voronoi diagram is that omega is known from the definition of the weighted Voronoi diagramiAs a control point qiThe weight of (2) reflects the capability of a central control point, namely a substation, and determines the division of a power supply range, which depends on the capacity Si of the substation and the regional load qi. Therefore, according to the requirement of the capacity-to-load ratio, the method can obtain
Figure BDA0001273012620000054
The weighted Voronoi diagram is centered on the substation and viThe expansion speed is expanded outwards at a constant speed until the two figures meet each other to form an evolved graph. V is theniAnd omegaiIn an inversely proportional relationship: v. ofi＝1/ωiMaximum power supply range d of the substationiIs supplied with power of radius RiThe limitation of (2): di＝Ri。
The method for applying the weighted Voronoi diagram to the division of the power supply range of the transformer substation is that the weight of the weighted Voronoi diagram is continuously adjusted to carry out iteration, each iteration obtains the power supply range of one transformer substation and obtains the weight of the next iteration, and after the iteration is carried out for n times, the weight is adjusted to reach a certain precision to stop the iteration, so that the final power supply range of the transformer substation is obtained.
Along with the enlargement of a planning area, the number of required substations is increased, the coordination difficulty of the power supply range among the substations is enhanced, and the times of adjusting the power supply range are increased due to repeated oscillation in the optimization searching process, so that the algorithm solving speed is reduced. Aiming at the problem, the weighted Voronoi diagram is hierarchically improved, each iteration of the weighted Voronoi diagram algorithm is completed in 3 steps, namely the power supply range of the transformer substation is expanded in three steps, wherein the weighted Voronoi diagram weight in each step of expansion is changed, and the weight depends on the load carried by the transformer substation and the capacity of the transformer substation. The hierarchical improvement of the weighted Voronoi diagram enables information interaction to be achieved twice in each iteration, the accuracy of division of the power supply range of the transformer substation in each iteration is enhanced, the success rate of one-time optimization is improved, and the implementation speed of the weighted Voronoi diagram algorithm is further improved. The specific weighted Voronoi diagram weight calculation formula is as follows:
Figure BDA0001273012620000061
in the formula:
Figure BDA0001273012620000062
respectively dividing speed and weight of the kth step in the jth iteration of the ith transformer substation;
Figure BDA0001273012620000063
the total load of the transformer substation after the 3 rd step division in the j-1 th iteration of the ith transformer substation is calculated;
Figure BDA0001273012620000064
the total load of the transformer substation after the 1 st step division in the jth iteration of the ith transformer substation is calculated;
Figure BDA0001273012620000065
and the total load of the transformer substation after the 2 nd step division in the jth iteration of the ith transformer substation is calculated. The formula for the expansion range limit for three steps in each iteration is:
Figure BDA0001273012620000066
in the formula:
Figure BDA0001273012620000067
representing the speed of the kth division in the jth iteration of the ith substation;
Figure BDA0001273012620000068
standard distance for each step of dilation; dstationThe distance between each transformer substation;
Figure BDA0001273012620000069
limiting the expansion range of the 1 st step division in the jth iteration of the ith substation;
Figure BDA00012730126200000610
representing the ith substation in the jth iterationThe speed of the kth division;
Figure BDA00012730126200000611
limiting the expansion range of the 2 nd step division in the jth iteration of the ith substation;
Figure BDA00012730126200000612
and limiting the expansion range of the 3 rd step division in the jth iteration of the ith substation.
The directionality improvement of the weighted Voronoi diagram specifically includes: due to the fact that DGs are connected into the power distribution network, line investment and loss are reduced, the load and capacity requirements of a main transformer are reduced, and the power supply range of a transformer substation is expanded. From the viewpoint of power supply range division of the transformer substation, in order to guarantee power supply economy, the power supply distance of the transformer substation should be correspondingly lengthened in the direction with lower load density. The DG output shares part of the load of the power distribution network, so that the density of the load supplied by the network in the area supplied by the DG is reduced, and the power supply radius of the transformer substation is correspondingly increased in the direction of the DG.
Since the confidence capacity of the DG determines the power supply range of the DG, that is, an area where the grid supply load density is reduced, the division of the power supply range of the substation is related to the confidence capacity of the DG and the relative position of the DG and the substation. In response to the above problem, the present invention performs directivity improvement on weighted Vonoroi, as shown in fig. 1. In the drawing, point a indicates the location of the substation, and point B indicates the location of the distributed power supply.
(1) Determining the maximum power supply range of the transformer substation according to the capacity of the transformer substation and the load density around the transformer substation, wherein the radius of a circle, in which the transformer substation A is located, is the power supply radius of the transformer substation when the DG is not considered, as shown in FIG. 1;
(2) determining the maximum power supply range of the distributed power supply according to the confidence capacity of the distributed power supply and the load density around the distributed power supply, wherein the radius of a circle, such as the circle where the distributed power supply B is located in FIG. 1, is the power supply radius of the distributed power supply;
(3) taking the transformer substation A as a round point, taking the power supply range of the transformer substation A as a circle, and making two radiuses, wherein the two radiuses are respectively tangent to the circle formed by the power supply range of the distributed power supply B, the two radiuses are respectively intersected with the power supply range of the transformer substation A at an M point and a Z point, and the direction covered by a fan-shaped AMZ containing the power supply range of the distributed power supply B is regarded as the direction of increasing the power supply radius of the transformer substation A;
(4) selecting a point D on a connecting extension line of the transformer substation A and the distributed power supply B, drawing an arc line MEZ by taking DM AS a radius, enabling the area of the arc MEZ to be equal to the area of a circle formed by the power supply range of the distributed power supply B, calculating the position of the point D and the distance of the DM, and calculating the distance D of AS when a point S is selected from any point S on the arc MEZi,ASAfter the distributed power source B is added into the transformer substation A, the power supply radius in the AS direction, the expansion speed of the transformer substation and the weight calculation formula of the weighted Voronoi diagram are AS follows:
Figure BDA0001273012620000071
in the formula: v. ofASConsidering the expansion speed of the transformer substation A after DG for the AS direction; v is the expanding speed of the substation A without considering DG in the AS direction; dASDistance AS; dAMDistance of AM; omegaASAnd weighting the weighted Voronoi diagram weight of the AS direction substation A.
4) The method provides an active power distribution network transformer substation optimization planning process, which comprises the following steps:
(1) firstly, determining the number and capacity combination scheme of W newly-built substations according to target annual load, existing substation capacity and a given substation candidate capacity set in advance;
(2) the method comprises the steps that access of a distributed power supply is not considered, for each scheme, traditional substation planning is carried out on a planning area based on a weighted Voronoi graph algorithm, and a substation site and a power supply range of each substation are obtained as initial solutions;
(3) obtaining the distribution condition of the distributed power supply in each substation power supply range according to the planning result of the substation, and evaluating the confidence capacity of the distributed power supply in each substation power supply range by using a distributed power supply confidence capacity evaluation method considering load characteristics;
(4) on the basis of the existing distributed power supply confidence capacity, transformer substation planning is carried out on a planning area by using an improved weighted Voronoi graph algorithm, and a new transformer substation site and the power supply range of each transformer substation are obtained;
(5) the power supply range is correspondingly changed due to the movement of the substation address, the steps (3) and (4) are repeated until the confidence capacities of the movement of the substation address and the distributed power supply reach the set precision, and then the iteration is stopped to obtain a final result;
(6) and calculating the investment cost of the W schemes according to the optimized planning model of the transformer substation based on the capacity and site results of the transformer substation, sequencing the investment cost according to the cost, and selecting the scheme with the minimum cost as a final planning scheme.
The best examples are given below
The example is a development area with a certain floor area of 63.08km2, the development area is divided into 368 cells according to land planning to carry out space load prediction, the planning target is 20 years, the target year prediction total load is 744.5MW, and the power factor is 0.9. The load characteristics of the different loads in the planned area, the load types are shown in fig. 2.
The photovoltaic power generation rated capacity is predicted to be 250.5MW by the planned area, and the fan power generation rated capacity is predicted to be 126.5 MW. The rated wind speed of the fan is 12.5m/s, the cut-in wind speed is 2.5m/s, the cut-out wind speed is 25m/s, the average wind speed is 19.56km/h, and the standard deviation of the wind speed distribution is 10.06 km/h; the rated photovoltaic illumination intensity is 1kW/m 2. The number of sampling years in the distributed power supply confidence capacity evaluation is 5 ten thousand years. The failure parameters are shown in table 1.
TABLE 1 failure Rate of the devices
Figure BDA0001273012620000081
The planning area is a brand new area to be planned without an existing station. Substations with four capacity specifications of 2 × 40MVA, 2 × 50MVA, 3 × 40MVA and 3 × 50MVA are used as alternative substations.
According to the principle of 'N-1', the load ratio of the two main transformer substations is limited to 65%, and the load ratio of the three main transformer substations is limited to 86.7%. Under the condition of not considering the influence of the distributed power supply, the traditional weighted Voronoi graph algorithm and the hierarchically improved weighted Voronoi graph algorithm are respectively used for site selection and volume fixing of the transformer substation of the traditional power distribution network. The capacity, position and power supply range of the transformer substation obtained by the two algorithms are the same. The convergence rate ratios of the two algorithms are shown in table 2.
TABLE 2 Convergence Rate comparison
Figure BDA0001273012620000082
As can be seen from Table 2, the hierarchical improvement greatly reduces the number of iterations required for the program and reduces the program run time. The substation power supply range is shown in fig. 3.
The active power distribution network substation location and volume determination is carried out based on a traditional weighted Voronoi graph algorithm and a directionality-improved weighted Voronoi graph algorithm, and the influence of load characteristics is considered when DG confidence capacity is evaluated by the two planning methods. The related results of the capacity and the like of the active power distribution network transformer substation based on the traditional weighted Voronoi graph algorithm are shown in the table 3, and the site and the power supply range are shown in the figure 4; the results of performing active power distribution network substation capacity and the like based on the improved weighted Voronoi diagram algorithm are shown in table 4, and the site and the power supply range are shown in fig. 5.
Table 3 active distribution network substation planning result based on traditional Voronoi diagram
Figure BDA0001273012620000083
Figure BDA0001273012620000091
As can be seen from table 3 and fig. 4, the DG confidence capacity in the active power distribution network is 32.95MW, which bears part of the load, the position and the power supply range of the substation are adjusted accordingly, the load demand can be satisfied by constructing 6 substations of 3 × 50MVA and 1 substation of 2 × 40MVA, and the annual investment cost of the scheme is 8112 ten thousand yuan. Compared with the traditional power distribution network planning, the active power distribution network planning reduces the installed capacity of the transformer substation and the investment cost of the transformer substation.
Table 4 active distribution network substation planning result based on improved Voronoi diagram
Figure BDA0001273012620000092
As can be seen from the comparative analysis of fig. 4 and 5, the directivity improvement takes into account the characteristic that the power supply radius of the substation increases in the DG direction, so that the location and the power supply range of the substation change. Distributed power supplies in the power supply range of the No. 1 transformer substation and the No. 7 transformer substation are relatively gathered, the transformer substation site moves towards the direction without DG, and the change of the power supply range is most obvious.
On the other hand, as can be seen from the comparison of the table 3 and the table 4, compared with the traditional Voronoi algorithm, the load rate of each transformer substation is more balanced due to the directivity improvement, the power supply range of the transformer substations is more reasonably divided, and the maximum difference value of the grid power supply load rates of the three transformer substations is reduced to 4.6% from 12.3%; due to reasonable power supply range division, the installed capacity and investment cost of the transformer substation are reduced by directional improvement, 5 3 × 50MVA transformer substations, 1 3 × 40MVA transformer substation and 12 × 40MVA transformer substation can be constructed to meet the load requirement, and the annual investment cost of the scheme is 7803 ten thousand yuan; due to the fact that the capacity of the transformer substation is less than 30MVA and the power supply range is divided reasonably, the power supply load rate of each transformer substation network is increased due to directional improvement, the value of the capacity of the DG is fully exerted, and the confidence capacity of the DG is increased from 32.95MW to 37.90 MW.
According to the results, the following can be analyzed: the solving speed of the planning model of the transformer substation is improved by improving the weighted Voronoi algorithm in a layering way, and the power supply range of the transformer substation is divided more reasonably and scientifically and effectively to play a role of DG confidence capacity by improving the directionality of the weighted Voronoi algorithm.

Claims (3)

1. An active power distribution network transformer substation planning method based on an improved weighted Voronoi diagram is characterized by comprising the following specific steps:
1) evaluating the confidence capacity of the distributed power supply on the basis of considering the load characteristics, specifically calculating the size of the load supply capacity of the system under any load characteristics by the distributed power supply under the condition of maintaining the reliability level of the system unchanged;
2) establishing a transformer substation optimization planning model considering the confidence capacity of the distributed power supply;
3) a planning method based on an improved weighted Voronoi diagram is provided, and comprises the following steps: a hierarchical refinement to the weighted Voronoi diagram and a directional refinement to the weighted Voronoi diagram; wherein the content of the first and second substances,
the hierarchical improvement of the weighted Voronoi diagram is that each iteration of the weighted Voronoi diagram algorithm is completed in 3 steps, namely the power supply range of the transformer substation is expanded in three steps, wherein the weighted Voronoi diagram weight is changed in each step of expansion, and the weight depends on the load carried by the transformer substation and the capacity of the transformer substation after the last step of expansion; the specific weighted Voronoi diagram weight calculation formula is as follows:
Figure FDA0002634502450000011
in the formula:
Figure FDA0002634502450000012
respectively dividing speed and weight of the kth step in the jth iteration of the ith transformer substation;
Figure FDA0002634502450000013
the total load of the transformer substation after the 3 rd step division in the j-1 th iteration of the ith transformer substation is calculated;
Figure FDA0002634502450000014
the total load of the transformer substation after the 1 st step division in the jth iteration of the ith transformer substation is calculated;
Figure FDA0002634502450000015
the total load of the transformer substation after the 2 nd step division in the jth iteration of the ith transformer substation is calculated; the formula for the expansion range limit for three steps in each iteration is:
Figure FDA0002634502450000016
in the formula:
Figure FDA0002634502450000017
representing the standard speed of the kth division in the jth iteration of the ith substation;
Figure FDA0002634502450000018
standard distance for each step of dilation; dstationThe distance between each transformer substation;
Figure FDA0002634502450000019
limiting the expansion range of the 1 st step division in the jth iteration of the ith substation;
Figure FDA00026345024500000110
representing the standard speed of the 1 st division in the jth iteration of the ith substation;
Figure FDA00026345024500000111
limiting the expansion range of the 2 nd step division in the jth iteration of the ith substation;
Figure FDA00026345024500000112
limiting the expansion range of the 3 rd division in the jth iteration of the ith substation;
the directionality improvement on the weighted Voronoi diagram specifically includes:
(1) determining the maximum power supply range of the transformer substation according to the capacity of the transformer substation and the load density around the transformer substation;
(2) determining the maximum power supply range of the distributed power supply according to the confidence capacity of the distributed power supply and the load density around the distributed power supply;
(3) taking the transformer substation A as a round point, taking the power supply range of the transformer substation A as a circle, and making two radiuses, wherein the two radiuses are respectively tangent to the circle formed by the power supply range of the distributed power supply B, the two radiuses are respectively intersected with the power supply range of the transformer substation A at an M point and a Z point, and the direction covered by a fan-shaped AMZ containing the power supply range of the distributed power supply B is regarded as the direction of increasing the power supply radius of the transformer substation A;
(4) selecting a point D on a connecting extension line of the transformer substation A and the distributed power supply B, drawing an arc line MEZ by taking DM AS a radius, enabling the area of the arc MEZ to be equal to the area of a circle formed by the power supply range of the distributed power supply B, calculating the position of the point D and the distance of the DM, and calculating the distance D of AS when a point S is selected from any point S on the arc MEZi,ASAfter the distributed power source B is added into the transformer substation A, the power supply radius in the AS direction, the expansion speed of the transformer substation and the weight calculation formula of the weighted Voronoi diagram are AS follows:
Figure FDA0002634502450000021
in the formula: v. ofASConsidering the expansion speed of the transformer substation A after the distributed power supply for the AS direction; v is the expanding speed of the substation A without considering the distributed power supply in the AS direction; dASDistance AS; dAMDistance of AM; omegaASWeighting the weighted Voronoi diagram weight of the AS direction transformer substation A;
4) the method provides an active power distribution network transformer substation optimization planning process, which comprises the following steps:
(1) firstly, determining the number and capacity combination scheme of newly built transformer substations in a target year according to the load of the target year, the capacity of the existing transformer substations and a given transformer substation candidate capacity set in advance;
(2) the method comprises the steps that access of a distributed power supply is not considered, for each scheme, traditional substation planning is carried out on a planning area based on a weighted Voronoi graph algorithm, and a substation site and a power supply range of each substation are obtained as initial solutions;
(3) obtaining the distribution condition of the distributed power supply in each substation power supply range according to the planning result of the substation, and evaluating the confidence capacity of the distributed power supply in each substation power supply range by using a distributed power supply confidence capacity evaluation method considering load characteristics;
(4) on the basis of the existing distributed power supply confidence capacity, transformer substation planning is carried out on a planning area by using an improved weighted Voronoi graph algorithm, and a new transformer substation site and the power supply range of each transformer substation are obtained;
(5) the power supply range is correspondingly changed due to the movement of the substation address, the steps (3) and (4) are repeated until the confidence capacities of the movement of the substation address and the distributed power supply reach the set precision, and then the iteration is stopped to obtain a final result;
(6) and (3) calculating the investment cost of each scheme determined in the step (1) according to a transformer substation optimization planning model based on the transformer substation capacity and site results, sequencing according to the cost, and selecting the scheme with the minimum cost as a final planning scheme.
2. The active power distribution network substation planning method based on the improved weighted Voronoi diagram according to claim 1, wherein the step 1) specifically comprises: the method comprises the following steps of selecting an electric power shortage expectation as a reliability index, wherein the electric power shortage expectation and the load size are in a monotonically increasing relation, and the reliability relation before and after the distributed power supply is added into a power distribution network is as follows:
f(G+GD＞L+ΔL)＝f(G＞L)＝r0 (1)
wherein f is a reliability estimation function; l and delta L are respectively the initial load and the newly added load of the system; gDG is the power generation capacity of the distributed power supply and the initial installed capacity of the system respectively; r is0The reliability index before power supply addition; and solving the newly increased load delta L of the system by adopting a truncation method in a successive approximation mode, wherein the newly increased load delta L is the confidence capacity of the distributed power supply.
3. The active power distribution network transformer substation planning method based on the improved weighted Voronoi diagram is characterized in that the step 2) comprises the following steps of considering that after the distributed power supply is connected to the power distribution network, the load of the power distribution network is shared by a transformer substation, photovoltaic and a fan, and establishing a new load inequality constraint by using a confidence capacity evaluation result so as to obtain a transformer substation optimization planning model:
Figure FDA0002634502450000031
in the formula: c is the total annual investment cost of the transformer substation; station is the annual cost of construction and maintenance of the transformer substation; the Feeder is the annual line investment cost of the low-voltage side of the transformer substation; CQ is the loss year cost of the low-voltage side line network of the transformer substation; piIs the load of the ith substation; siCapacity of the ith substation;
Figure FDA0002634502450000032
is the power factor; CC (challenge collapsar)PV(i) Confidence capacities of all photovoltaic power supplies in the power supply range of the ith transformer substation are obtained; CC (challenge collapsar)WTG(i) Confidence capacity of all fan power supplies in the power supply range of the ith transformer substation; j. the design is a squareiA set of loads supplied for the ith substation; n is the total number of the existing and newly-built transformer substations; j is the set of all load points; li,kIs the connection distance, R, between the ith substation and the kth loadiAnd (4) limitation of power supply radius for the ith substation.
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