CN109919350B - Multi-stage substation expansion planning method considering overall economy - Google Patents
Multi-stage substation expansion planning method considering overall economy Download PDFInfo
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Abstract
The invention relates to a multi-stage substation expansion planning method considering overall economy, which comprises the following steps: taking a load saturation period as a target year of a planning period, and planning the site selection and volume determination of the transformer substation under the condition of not considering the distributed power supply access scene according to the load level of a planning area of the target year; planning an area load level, the existing substation capacity, a DG confidence capacity and a given substation candidate capacity set according to a target year; the load level of the planning area at each stage of the middle year is combined, and the planning scheme of the transformer station in the middle year is obtained by carrying out back pushing from the target year to the current year stage by stage on the basis of the priority volume reduction principle; pushing back to the current year from the target year in stages by taking the priority station-going as a principle to obtain a planning scheme of the intermediate-year substation; the scheme with the optimal economy and the target annual substation planning scheme form a multi-stage substation expansion planning scheme; and calculating the overall economy of the multi-stage substation expansion planning scheme.
Description
Technical Field
The invention relates to a multi-stage substation expansion planning method considering overall economy, which is suitable for planning work of urban distribution network substations in China and belongs to the field of urban network planning management.
Background
The planning of the transformer substation is an important component in the planning of the power system, and the result of the planning scheme of the transformer substation influences the grid structure of the whole power distribution network, the economy of investment and operation and the reliability of power supply. Because the power load is increased year by year, the construction sequence of the transformer substation in the planning period should meet the load requirements of each stage. The planning schemes of the transformer stations in the target year and the middle year are coordinated, the economic transition of the transformer station development in the planning area is realized, the practical significance is great, and the method is also a main research direction in transformer station planning.
In the existing multi-stage substation planning research, a problem is usually decomposed into two problems, namely target annual substation planning and intermediate annual substation planning, and then the two problems are gradually solved. In the planning stage of the target annual substation, the station address and the station capacity of the target annual substation are decided by taking the minimum annual investment cost of a target annual planning scheme as a target according to the load requirements of a target annual planning area. And then, optimizing the construction and capacity expansion time of each transformer substation in the intermediate stage by combining the load level of the intermediate stage planning area based on the planning result of the target annual transformer substation. In the method, the target annual substation planning scheme is selected only in consideration of the economy of the target annual planning scheme, and the intermediate years are solved on the basis of the target annual planning scheme. In fact, since the construction costs of operating the substation in different years have different time values, the economy of the planning scheme of the substation in the target year and the middle year needs to be integrally measured from the perspective of the life cycle cost. Therefore, the step-by-step planning methods proposed by the existing research cannot effectively coordinate the interaction between the target year and the inter-year substation planning schemes.
Disclosure of Invention
The invention aims to provide a multi-stage substation double-layer optimization method on the basis of considering interaction between a target year and a planning scheme of a middle year substation, planning of the target year substation is carried out by adopting a weighted Voronoi diagram, a rapid push-back strategy of a transition scheme is formulated for the middle year, and an integrated solving process of multi-stage substation extension planning is formed. The technical scheme is as follows:
a multi-stage substation expansion planning method considering overall economy comprises the following steps:
(1) Taking a load saturation period as a target year of a planning period, planning the load level of an area according to the target year, carrying out site selection and volume determination planning on a transformer substation under the condition that a Distributed Generation (DG) is not considered to be accessed, and evaluating DG confidence capacity according to a planning scheme;
(2) Determining N transformer substation capacity combination schemes meeting capacity constraints according to the load level of a planned area, the capacity of an existing transformer substation, the DG confidence capacity and a given transformer substation candidate capacity set in a target year;
(3) And (3) planning a target annual transformer substation aiming at the kth capacity combination scheme, wherein the method comprises the following steps:
a) The method comprises the steps that DG access is not considered, substation planning is carried out on a planning area by adopting a weighted Voronoi graph algorithm according to a substation capacity combination scheme, and an initial substation site and a power supply range of a substation are obtained;
b) According to the obtained DG distribution condition in the power supply range of each transformer substation, evaluating the DG confidence capacity in the power supply range of each transformer substation;
c) On the basis of the obtained DG confidence capacity, dividing the power supply range of each transformer substation by using a weighted Voronoi graph algorithm, and determining a new transformer substation site by using the minimum load moment in the power supply range of each transformer substation as a principle;
d) Repeating the steps b) -c) until the substation site movement and the DG confidence capacity reach a certain precision, and stopping iteration to obtain a target annual substation planning scheme I k ；
(4) According to the planning scheme I of the target annual transformer substation k And in combination with the load level of the planning area at each stage of the middle year, the planning scheme M of the transformer station in the middle year is obtained by carrying out back pushing from the target year to the current year from stage to stage on the basis of the priority volume reduction principle k The method comprises the following steps:
a) Selecting a construction scheme of the transformer substation at the t +1 stage as an initial construction state of the transformer substation at the t stage, and dividing the power supply range of each transformer substation by using a weighted Voronoi diagram method;
b) The transformer substation with the lowest load capacity is subjected to station-going processing, and the construction state of each transformer substation is updated;
c) Dividing the power supply range of each transformer substation again by adopting a weighted Voronoi diagram method, judging whether the capacity constraint and the power supply radius constraint of the transformer substation are met, if so, repeating the step b), and if not, abandoning the substation-going operation; judging whether the expansion of the transformer substation is finished or not, if so, reducing the capacity of the transformer substation, and dividing the power supply range again, if so, repeating the step b), and if not, entering the next step;
d) Abandoning the operation of the transformer substation, updating the construction state of the transformer substation, taking the scheme as the final construction scheme of the current stage, enabling t = t-1, returning to the step a) until the calculation of each stage is completed, and obtaining a planning scheme M of the middle-aged transformer substation k ；
(5) According to the planning scheme I of the target annual transformer substation k And pushing the target year back to the current year from stage to stage by taking priority station-going as a principle to obtain a planning scheme N of the intermediate-year substation k The method comprises the following steps:
a) Selecting a construction scheme of the transformer substation at the t +1 stage as an initial construction state of the transformer substation at the t stage, and dividing the power supply range of each transformer substation by using a weighted Voronoi diagram method;
b) Sequencing according to the ratio of the actual load rate of the transformer substation to the rated load rate of the transformer substation, judging whether the transformer substation with the lowest ratio completes capacity expansion, if so, performing capacity reduction operation on the transformer substation, otherwise, performing station-removing processing on the transformer substation, and updating the construction state of each transformer substation;
c) Recalculating the power supply range of the transformer substation, judging whether the transformer substation capacity constraint and the transformer substation power supply radius constraint are met, if so, repeating the step b), and if not, giving up the operation and entering the next step;
d) Abandoning the operation of the transformer substation, updating the construction state of the transformer substation, taking the scheme as the final construction scheme of the current stage, enabling t = t-1, returning to the step a) until the calculation of each stage is completed, and obtaining the planning scheme N of the middle-aged transformer substation k ；
(6) Respectively calculating planning scheme M of middle-year substation k 、N k The economic efficiency of the two is the optimal scheme of the economic efficiency and the target annual substation planning scheme I k Jointly form a multi-stage substation extension planning scheme F k ；
(7) Calculation multi-stage substation extension planning scheme F k The overall economy of (2);
(8) Enabling k = k +1, and returning to the step (3) until the solution of the capacity combination scheme of all the N target annual transformer stations is completed;
(9) Planning scheme F of multi-stage transformer substation 1 To F N And taking the scheme with the optimal overall economy as a planning result of the multi-stage transformer substation in the planning area.
The step (7) is specifically as follows:
a) Setting the annual load growth rate of the saturation period to be 0.4% by combining with the constraint of the load rate of the transformer substation, and solving the construction scheme I of the target annual transformer substation k Maximum age T which can still meet load demand after planning period f ；
b) After the current year reaches saturation period T f The investment cost of the transformer substation in each phase in the year is taken as the economic cost of the planning scheme of the multi-phase transformer substation, and can be expressed as follows:
in the formula: m station The annual investment cost value of the transformer substation in the middle stage comprises the construction cost and the maintenance cost of the transformer substation; m line Annual investment cost values for the middle-aged lines, including line construction, maintenance and network loss costs, T m The time when the load enters the saturation period; r is the discount rate; c Station 、C Feeder For the target annual substation and line investment cost annual value, C CQ The annual loss cost annual value of the road network is the target annual.
Drawings
FIG. 1 is a model solution framework;
FIG. 2 is an economic calculation model;
FIG. 3 is a current distribution of regional loads;
FIG. 4 is a regional load target annual distribution;
FIG. 5 is a diagram of a multi-stage substation step plan result;
FIG. 6 is a schematic diagram of a radius change factor;
fig. 7 shows the transformer substation construction situation of each stage in the area, which is obtained by performing joint planning on the target year and the middle year in the development area by using the multi-stage transformer substation double-layer planning optimization model provided herein.
Detailed Description
The invention relates to a multi-stage substation expansion planning method considering overall economy, which comprises the following steps:
(1) Establishing a two-tier optimization framework for a multi-phase substation
The multi-stage substation planning problem comprises two problems of target annual substation planning and intermediate annual substation planning. The planning of the middle-year substation is performed based on the planning result of the target-year substation, and the planning result is limited by the planning scheme of the target year, so that the economy of the planning scheme of the middle-year substation needs to be considered in the planning of the target-year substation. In order to coordinate interaction between the target year and the middle year transformer station planning scheme, the invention provides a double-layer optimization model, wherein the upper layer takes the optimal overall economy of the target year and the middle year as a target, solves the target year transformer station planning scheme and transmits the planning scheme to the lower layer model; the lower layer model is used for solving the construction sequence of the transformer stations in each phase of the middle year by taking the minimum capacity-to-load ratio of the transformer stations meeting the N-1 criterion as a target according to the planning result of the target annual transformer station, and transmitting the planning scheme of the middle annual transformer station to the upper layer as a part of overall economic evaluation to select the optimal multi-phase transformer station planning scheme.
Through the double-layer planning optimization model, the economy of the construction scheme of the transformer substation in the middle year is considered in the selection of the transformer substation planning scheme in the target year, and the interaction relation between the planning problems of the transformer substations in the target year and the middle year can be effectively coordinated, so that the overall optimization of the multi-stage transformer substation is realized.
(2) Method for calculating overall economy of multi-stage transformer substation
The multi-stage substation expansion planning optimizes the dynamic substation expansion process from the current year to the target year. In the process, a new substation can be built or the capacity of the existing substation can be expanded at each stage until the construction of all substations is completed in a target year. Considering the relationship between the life cycle and the planning period of the substation, only a few substations can reach the service life exactly when reaching the target year, and the rest substations may have a certain service life (such as the transformer 3 in fig. 2) or reach the service life (such as the transformer 1 in fig. 2) before reaching the target year, so that the problems of residual value, reconstruction and the like of the substations need to be considered. In addition, in the long-term multi-phase substation planning problem, a load increase saturation period is often used as a planning target year. And when the load enters a saturation stage, the increase is slow, and the planning scheme of the target annual transformer substation can still meet the load demand in a long period in the future. In the period, the substation is circularly put into construction after the service life is reached, so that the circulating investment cost of the substation in the period is also included in the overall economic calculation of the multi-stage substation, so that the target year and the middle year planning scheme are integrally measured. Because the investment time scales of all transformer substations are different, the problem of repeated construction is also involved, all expenses cannot be directly accumulated, and the expenses must be converted to a uniform time base point for settlement. For this reason, it is necessary to determine the time domain of the cyclic commissioning of the substation after the target year.
Through research on economic development conditions and load development conditions of developed countries such as the United states, the United kingdom and Japan, the power load of a region shows continuous low-speed smooth increase after entering a saturation stage. In this phase, the load growth trend is slower, with an average growth rate of not more than 4% over consecutive 10 years. The method takes the time of the load entering the saturation period of the planning region as the planning target year, supposes that the load still increases at the annual increase level of 0.4 percent thereafter, and under the capacity-to-load ratio constraint of the transformer substation, the transformer substation planning scheme of the target year is T after the target year f All within the yearThe load requirements of the area can be met, and then the substation of the area needs to be re-planned. Therefore, the invention will be based on the T after the current year to the target year f The annual costs are used as the economic cost of the multi-stage substation planning scheme, and are shown in fig. 2 in detail.
(3) Establishing multi-stage transformer substation double-layer optimization model
(3.1) model for planning target annual substation
1) Objective function
In order to perform overall optimization on the multi-stage substation planning scheme, the optimal overall economy of the multi-stage substation is adopted as a target function in a target annual substation planning model, as shown in formula (1).
C MID ＝M station +M line (2)
Wherein, C MID For the annual value of the post-intermediate investment costs, M station The annual investment cost value of the transformer substation in the middle stage comprises the construction cost and the maintenance cost of the transformer substation, and the formula (3) is shown. M line The specific calculation is shown as formula (4) for the annual value of the line investment cost in the middle year, including the line construction cost, the maintenance cost and the network loss cost. C Station 、C Feeder For the target annual transformer station and line investment cost annual value, C CQ For the target annual line network loss cost annual value,the specific calculation is the same as the calculation of the cost of the intermediate-year substation and the line. N is the total number of the transformer substations; t is a unit of m The time when the load enters the saturation period;
the investment cost of the transformer substation i is saved; />
The variable is 0/1 and indicates whether the transformer station i completes the construction in the stage t; />
The expansion cost of the transformer substation i; />
The variable is 0/1, and represents whether the expansion of the transformer station i is completed or not in the stage t; r is the discount rate; m is i Indicating the life of substation i; u. of i Zi is the maintenance cost proportion and the residual value cost proportion of the transformer substation i; j. the design is a square i,t The load set is carried by the transformer substation i in the stage t, and j is a load node; h is a line type set, and H is a line type; />
The unit construction cost of the h-shaped line; l i,j The connection distance between the transformer substation i and the load point j is obtained; lambda [ alpha ] fi,t,j,h The variable is 0/1 and indicates whether an h-type line is built between the transformer substation i and the load point j in the stage t; e.g. of the type h The life of the h-type line; v. of h Is the maintenance cost proportion of the h-type line; y is h Is the residual cost ratio of the h-type line; />
For loss conversion coefficients of h-lines>
For the current electricity price, <' >>
For the number of hours lost per year of the line, based on the number of hours lost>
Resistance per kilometer for h-type line, U i For the i-line voltage of the substation, < >>
Is the power factor.
Considering that after the DG is connected into the power distribution network, partial load is supplied by the DG, the transmission capacity of a line is reduced, and the running loss coefficient k (M) of the line is increased i,t ) Will follow DG permeability M i,t Is increased and decreased, where M i,t Is calculated as follows:
in the formula, P DG As confidence capacity of DG, P L Is the maximum load.
2) Constraint conditions
In the planning of the transformer substation, the load rate of each transformer substation must meet the N-1 principle, so the construction capacity and the load level of the transformer substation must meet certain inequality requirements. Meanwhile, the network supply load of a planning area is reduced by the access of the DGs, the power supply range of the transformer substation in the DG direction is enlarged, and the influence of the DGs must be considered in the power supply radius constraint of the transformer substation. The final set-up constraints are as follows:
(1) and (3) capacity constraint of the transformer substation:
in the formula: s i Representing the construction capacity of a target annual substation i; gamma ray i The rated load rate of the transformer substation i; t is i PV The confidence capacity of the photovoltaic power supply in the power supply range of the transformer substation i is obtained; t is i WTG And (4) the confidence capacity of the fan power supply in the power supply range of the transformer substation i.
(2) Radius constraint of power supply of transformer substation
l i,j ≤R i ×ψ i,j (8)
In the formula, R i The method is restricted by the power supply radius of a transformer substation i in the traditional power distribution network; radius variation factor psi i,j Reflecting the influence of the DG power supply in the direction of the load point j, the larger the DG confidence capacity influencing the load point j is, the larger psi i,j The larger the value is, the specific calculation is as follows:
in the formula: g i A DG set for supplying power to a transformer substation i, wherein g is a DG node; s i,g And R i,g Respectively providing installed capacity and equivalent power supply radius of a DG node g for supplying power to a transformer substation i; l i,g The distance between the transformer substation i and the DG node g is calculated; ρ is a unit of a gradient i Load density within the range of power supply to substation i.
(3) The power supply range of the transformer substation is not crossed:
in the formula: eta i,j The variable is 0/1 and is used for judging whether the load point j is powered by the transformer substation i; delta i,g And the variable is also a 0/1 variable and is used for judging whether the DG point g supplies power to the substation i.
(3.2) planning model of middle-aged substation
And the planning model of the middle annual transformer station is based on the planning result of the target annual transformer station, takes the lowest capacity-to-load ratio of the transformer station meeting the N-1 criterion as a target function, and decides the construction scheme of the middle annual transformer station. The planning layer objective function of the middle-year substation is as follows:
minF＝∑S i,t /P t (12)
wherein S is i,t Indicating rated capacity, P, of substation i in the t-th phase t,max Representing the load maximum at the t-th stage.
In the planning of the middle-age substation, the capacity constraint, the power supply radius constraint and the power supply range constraint of the substation also need to be met. In addition, due to the high dismantling cost of the substation, the substation construction scheme is constrained by the planning scheme in the preorder stage without considering the dismantling and rebuilding condition of the substation. The final set-up constraints are as follows:
(1) and (3) capacity constraint of the transformer substation:
(2) power supply radius constraint of transformer substation
l i,j,t ≤R i,t ×ψ i,j,t (14)
(3) The power supply range of the transformer substation is not crossed:
(4) and (3) construction sequence constraint of the transformer substation:
(5) and (3) station site constraint of the transformer substation:
L i,t ＝L i,T (17)
in the formula, L i,t Indicating the site of substation i at stage t, L i,T And represents the site of the target annual substation i.
(4) Method for providing integrated planning of multi-stage transformer substation
(4.1) solving of planning model of target annual substation
The target annual substation planning is single-stage substation planning based on the load level of a target annual planning area, and the decision variables are the site and the capacity of a newly-built substation. Firstly, under the condition that DG is not considered, transformer substation planning is carried out according to the load level of a planning area and the capacity of an existing transformer substation, and DG confidence capacity is evaluated according to a planning result. And estimating the number range of the newly-built substations by combining the DG confidence capacity and the capacity to be selected of the substation, wherein the number of capacity combination schemes meeting the capacity-to-load ratio requirement of the substation is less under the constraint of the determined number of the newly-built substations, the capacity combination scheme of the substation can be solved by directly adopting an enumeration method, and finally, site selection and volume determination of the substation are performed by combining a weighted Voronoi graph algorithm. The specific solving process is as follows:
(1) and planning the transformer substation according to the load level of the target year planning area without considering the DG access scene, and evaluating the DG confidence capacity according to a planning scheme.
(2) And determining N transformer substation capacity combination schemes meeting the capacity constraint according to the load level of the planned region in the target year, the capacity of the existing transformer substation, the DG confidence capacity and the given candidate capacity set of the transformer substation.
(3) And (4) performing traditional substation planning on a planning area by adopting a weighted Voronoi graph algorithm according to each substation capacity combination scheme without considering DG access to obtain an initial substation site and a power supply range of the substation.
(4) And obtaining the distribution condition of the DGs in the power supply range of each transformer substation according to the planning result of the transformer substation, and evaluating the confidence capacity of the DGs in the power supply range of each transformer substation.
(5) On the basis of the obtained DG confidence capacity, the power supply range of each transformer substation is divided by using a weighted Voronoi graph algorithm, a new transformer substation site is determined by using the principle that the load moment in the power supply range of each transformer substation is minimum, and the process is continuously repeated until the movement of the transformer substation site reaches certain precision.
(6) And (4) repeating the steps (3) to (4) until the station address of the transformer substation moves and the confidence capacity of the distributed power supply reaches a certain precision, and stopping iteration to obtain the final result of the scheme.
(4.2) solving planning model of middle-aged substation
The planning of the transformer station in the middle year relates to a plurality of time nodes, the planning schemes of all the nodes have high relevance, and the solving difficulty is high. In order to solve the problem, a rapid push-back strategy for transition from the current year to the current year in stages based on a target year planning scheme is provided. Starting from the construction condition of a target annual transformer substation, the construction condition is used as the preset construction state of the transformer substation in the previous stage, the construction capacity of the transformer substation is continuously reduced according to the load capacity of the transformer substation, and the construction is pushed back to the current year stage by stage. In the pushing-back process, two ideas of preferentially reducing the commissioning capacity of a certain transformer substation and preferentially reducing the number of the commissioned transformer substations are mainly provided. In the method, the middle year construction scheme under the target year transformer station planning scheme is solved on the basis of priority volume reduction and priority station arrival in the transformer station middle year planning scheme solving, and finally the scheme with lower cost in the volume reduction and the priority station arrival is selected as the middle year construction scheme of the target year planning scheme.
The quick push-back strategy flow under the priority station-leaving principle is as follows:
(1) selecting a construction scheme of the transformer substation at the t +1 stage as a transformer substation initial state at the t stage, and dividing the power supply range of each transformer substation by using a weighted Voronoi diagram method;
(2) carrying out station-going processing on the transformer substation with the lowest load capacity, and updating the construction state of each transformer substation;
(3) and (3) dividing the power supply range of each transformer substation by adopting a weighted Voronoi diagram method, judging whether the power supply range meets transformer substation capacity constraint and power supply radius constraint, if so, repeating the step (2), and otherwise, giving up the station-going operation. If the capacity expansion of the transformer substation is completed, carrying out capacity reduction on the transformer substation, dividing a power supply range again, judging whether the constraint is met, if so, repeating the step (2), and if not, entering the next step;
(4) abandoning the operation of the transformer substation, updating the construction state of the transformer substation, taking the scheme as a final construction scheme of the current stage, and repeating the steps (1) - (4) until the calculation of each stage is completed, wherein t = t-1;
(5) and calculating the comprehensive investment cost in the whole planning period according to the construction scheme of the transformer substation in the target year and each intermediate stage.
The priority volume reduction principle is substantially the same as the specific operation flow of the priority outbound principle, the main difference is steps (2) - (3), and the operation methods of the priority volume reduction strategy steps (2) - (3) are listed as follows:
(2) sequencing according to the ratio of the actual load rate of the transformer substation to the rated load rate of the transformer substation, judging whether the transformer substation with the lowest ratio completes capacity expansion, if so, performing capacity reduction operation on the transformer substation, otherwise, performing station-removing processing on the transformer substation, and updating the construction state of each transformer substation;
(3) and (3) recalculating the power supply range of the transformer substation, judging whether the transformer substation capacity constraint and the transformer substation power supply radius constraint are met, if so, repeating the step (2), and otherwise, abandoning the operation and entering the next step.
The floor area of 97.56km is selected for the calculation example 2 Is divided into 308 cells according to the right-of-way plan. And (4) predicting the load of the development area according to the load density of different types of planning land and the occupied area of each cell until the total load of the target year is 1676.5MW and the power factor is 0.9. The photovoltaic rated capacity of the area in the target year is predicted to be 301.5MW, and the fan rated capacity is predicted to be 225MW. The selectable capacities of the transformer substation to be built are 2 × 40MVA, 2 × 50MVA, 3 × 40MVA and 3 × 50MVA, and the construction costs are 2200 ten thousand yuan, 2500 ten thousand yuan, 3200 ten thousand yuan and 3600 ten thousand yuan respectively. The two transformer substations can be expanded into three transformer substations, and the expansion cost of the 2 x 40MVA and the 2 x 50MVA transformer substations is 1000 ten thousand yuan and 1200 ten thousand yuan respectively. The service life of the transformer substation is 30 years. According to the principle of 'N-1', the load factor of a transformer substation with two main transformers is limited to 65%, and the load factor of the transformer substation with three main transformers is limited to 85%.
The planning area includes three existing stations of 3 × 50MVA, and the site, capacity and power supply range are shown in fig. 3. Fig. 3 shows the existing loads of the development area, other emerging loads are divided into loads starting to develop in the 1 st year and loads starting to develop in the 5 th year according to the load size of the target year, all the loads increase according to the increasing trend of an S-shaped curve, and the loads start to enter a saturation period from the point load in the development area in the 20 th year of the planning period. The increasing trend of various types of loads is shown in fig. 5, and the planning period is divided into 4 stages according to the increasing condition of the loads.
Firstly, the existing multi-stage transformer substation planning idea is adopted, and the annual investment cost of the target annual planning scheme is optimally used as a target to solve the site capacity of the target annual transformer substation. The plan of the target annual substation is obtained as shown in fig. 6 (d). According to the target annual substation planning scheme, the rapid push-back strategy proposed in (3.2) is adopted to solve the planning result of the intermediate annual substation, and the result is shown in fig. 6. The target year of the development area under the scheme is 15 substations which comprise 2 substations with the capacity of 3 multiplied by 40MW and 12 substations with the capacity of 3 multiplied by 50MW, the total commissioning capacity of the substations is 2190MW, and the substation 1, the substation 2 and the substation 3 are existing substations in the area. Under the scheme, the capacity-load ratio of the transformer substation in the target year is 1.377, and the annual investment cost in the target year is 15417 ten thousand yuan per year.
By adopting the multi-stage transformer substation double-layer planning optimization model provided by the text, the target year and the middle year of the development area are planned in a combined manner, and the construction condition of the transformer substation in each stage of the area is obtained as shown in fig. 7. As can be seen from the figure, by the target year, 16 substations including 1 substation with 2 × 40MW capacity, 4 substations with 3 × 40MW capacity and 11 substations with 3 × 50MW capacity are built in the region, and the total installed capacity reaches 2210WM. The data of the transformer substation construction capacity, the investment cost and the like of the target year and each intermediate stage obtained by the scheme and the step-by-step planning method are shown in tables 1 and 2.
Table 1 comparison of target year transformer station construction results under two schemes
TABLE 2 comparison of the middle year planning results for the two schemes
As can be seen from the data in table 1, compared with the traditional multi-stage substation step-by-step planning method, the scheme obtained by the joint planning method requires 16 substations in a target year, the construction capacity of the substation is increased by 20MVA, and the annual investment cost in the target year is increased by 132 ten thousand yuan/year. But from the whole planning period, the comprehensive investment cost of the scheme obtained by the multi-stage transformer substation joint planning method provided by the invention is reduced by 4.2%. The method for planning the multi-stage transformer substation in the step-by-step optimization mode can eliminate the global optimal solution in the planning stage of the target annual transformer substation, and enables the final planning result to fall into the local optimal solution. As can be seen from the data in table 2, the solution obtained by the step planning is slightly lower in investment cost in the fourth stage, but the investment cost in the first stage and the third stage is higher than that obtained by the solution of the joint planning method. Meanwhile, in the two schemes, the investment cost of the intermediate stage (and the first, second and third stages) accounts for more than 40% of the total investment cost of the planning period, and is an important part which is not ignored in the total investment cost of the planning period.
The following conclusion can be drawn through the target year and middle year economic comparison results of the two schemes, in the multi-stage transformer substation planning, the proportion of the investment cost of the middle year transformer substation in the total investment cost in the whole planning period is not negligible, and the investment cost of the target year is used as an inaccurate index for judging the economic performance of the multi-stage transformer substation planning scheme. Meanwhile, the construction sequence of the transformer substation must meet certain constraints, so the selection of the planning scheme of the target annual transformer substation limits the selection range of the planning scheme of the middle annual transformer substation. In the traditional multi-stage transformer substation step-by-step planning method, only the investment cost of the target year is considered in the selection of the construction scheme of the target year, the influence of the investment cost of the middle year on the overall planning scheme is ignored, the traditional multi-stage transformer substation step-by-step planning method is a step-by-step optimizing strategy, the obtained result is usually trapped in local optimization, and the global optimal solution cannot be obtained.
Claims (1)
1. A multi-stage substation expansion planning method considering overall economy comprises the following steps:
(1) Taking a load saturation period as a target year of a planning period, planning the load level of an area according to the target year, carrying out site selection and volume setting planning on the transformer substation without considering the access scene of the distributed power supply, and evaluating the confidence capacity of the distributed power supply according to a planning scheme;
(2) Determining N transformer substation capacity combination schemes meeting capacity constraints according to the load level of a planned area of a target year, the capacity of an existing transformer substation, the confidence capacity of a distributed power supply and a given transformer substation candidate capacity set;
(3) And planning a target annual transformer substation aiming at the kth capacity combination scheme, wherein the method comprises the following steps:
a) The distributed power supply access is not considered, and a weighted Voronoi graph algorithm is adopted to plan the transformer substation in the planning area aiming at the transformer substation capacity combination scheme, so that an initial transformer substation site and the power supply range of the transformer substation are obtained;
b) According to the obtained distribution condition of the distributed power supply in the power supply range of each transformer substation, evaluating the confidence capacity of the distributed power supply in the power supply range of each transformer substation;
c) On the basis of the obtained confidence capacity of the distributed power supply, dividing the power supply range of each transformer substation by using a weighted Voronoi graph algorithm, and determining a new transformer substation site by using the minimum load moment in the power supply range of each transformer substation as a principle;
d) Repeating the steps b) -c) until the station address of the transformer substation moves and the confidence capacity of the distributed power supply reaches a certain precision, and stopping iteration to obtain a planning scheme I of the transformer substation in the target year k ；
(4) According to the planning scheme I of the target annual transformer substation k And the planning plan M of the substation in the middle year is obtained by combining the load level of the planning area in each stage of the middle year and pushing the planning area back to the current year from the target year to the current year in stages by taking the priority volume reduction as the principle k The method comprises the following steps:
a) Selecting a construction scheme of the transformer substation at the t +1 stage as an initial construction state of the transformer substation at the t stage, and dividing the power supply range of each transformer substation by using a weighted Voronoi diagram method;
b) The transformer substation with the lowest load capacity is subjected to station-going processing, and the construction state of each transformer substation is updated;
c) Dividing the power supply range of each transformer substation again by adopting a weighted Voronoi diagram method, judging whether the capacity constraint and the power supply radius constraint of the transformer substation are met, if so, repeating the step b), and if not, giving up the station-going operation; judging whether the expansion of the transformer substation is finished or not, if so, reducing the capacity of the transformer substation, and dividing the power supply range again, if so, repeating the step b), and if not, entering the next step;
d) Giving up the operation of the transformer substation, updating the construction state of the transformer substation, taking the scheme as the final construction scheme of the stage, enabling t = t-1, returning to the step a) until the calculation of each stage is completed, and obtaining a planning scheme M of the transformer substation in the middle year k ；
(5) According to the planning scheme I of the target annual transformer substation k And pushing the target year back to the current year from stage to stage on the basis of priority station-going to obtain a planning scheme N of the intermediate-year substation k The method comprises the following steps:
a) Selecting a construction scheme of the transformer substation at the t +1 stage as an initial construction state of the transformer substation at the t stage, and dividing the power supply range of each transformer substation by using a weighted Voronoi diagram method;
b) Sequencing according to the ratio of the actual load rate of the transformer substation to the rated load rate of the transformer substation, judging whether the transformer substation with the lowest ratio completes capacity expansion, if so, performing capacity reduction operation on the transformer substation, otherwise, performing station-removing processing on the transformer substation, and updating the construction state of each transformer substation;
c) Recalculating the power supply range of the transformer substation, judging whether the transformer substation capacity constraint and the transformer substation power supply radius constraint are met, if so, repeating the step b), and if not, giving up the operation and entering the next step;
d) Abandoning the operation of the transformer substation, updating the construction state of the transformer substation, taking the scheme as the final construction scheme of the current stage, enabling t = t-1, returning to the step a) until the calculation of each stage is completed, and obtaining the planning scheme N of the middle-aged transformer substation k ；
(6) Respectively calculating planning scheme M of middle-year substation k 、N k The economic efficiency of the two is the optimal scheme of the economic efficiency and the target annual substation planning scheme I k Jointly form a multi-stage substation expansion planning scheme F k ；
(7) Computing multiple stagesSubstation extension planning scheme F k The overall economy of the process is as follows:
a) Setting the annual load growth rate of the saturation period to be 0.4% by combining with the constraint of the load rate of the transformer substation, and solving the construction scheme I of the target annual transformer substation k Maximum age T which can still meet load demand after planning period f ；
b) After the current year reaches saturation period T f The investment cost of the transformer substation in each phase in the year is taken as the economic cost of the planning scheme of the multi-phase transformer substation, and can be expressed as follows:
in the formula: m station The annual investment cost value of the transformer substation in the middle stage comprises the construction cost and the maintenance cost of the transformer substation; m line Annual investment cost values for the middle-aged lines, including line construction, maintenance and network loss costs, T m The time when the load enters the saturation period; r is the discount rate; c Station 、C Feeder For the target annual substation and line investment cost annual value, C CQ The annual loss cost value of the target annual line network is set;
(8) Enabling k = k +1, and returning to the step (3) until the solution of the capacity combination scheme of all the N target annual transformer stations is completed;
(9) Planning scheme F of multi-stage transformer substation 1 To F N And taking the scheme with the optimal overall economy as a planning result of the multi-stage transformer substation in the planning area.
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