CN107221926B - TSC-based feeder line access user capacity calculation method - Google Patents
TSC-based feeder line access user capacity calculation method Download PDFInfo
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- H—ELECTRICITY
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- H—ELECTRICITY
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Abstract
The invention aims to provide a TSC-based feeder access user capacity calculation method, which aims to solve the problem that the feeder access user capacity can only be judged by experience in the prior art. The method comprises the following steps of obtaining the existing load of each feeder line, the load on each feeder line on the primary side and the conversion coefficient between the capacity of the distribution transformer on the secondary side; calculating according to a TSC model to obtain a TSC value; calculating according to the feeder model to obtain the theoretical load of each feeder; calculating accessible loads on each feed line according to the theoretical load and the existing load; judging whether the accessible load on each feeder is non-negative, if so, taking the accessible load on the feeder as the accessible capacity of the corresponding feeder; and obtaining the capacity of the access user distribution transformer of the feeder line of the distribution network according to the accessible capacity of each feeder line and the corresponding conversion coefficient. The capacity of the distribution transformer of the feeder line access user can be calculated by the method.
Description
Technical Field
The invention relates to a power system, in particular to a TSC-based feeder line access user capacity calculation method.
Background
The economic development of China is rapid, the electricity consumption is rising year by year, a power distribution network is often required to be connected with a new load to meet the requirement of load change, and on the premise that the power supply point of the power distribution network is insufficient and N-1 safety is required to be met, it is very important to mine the power supply potential of the power distribution network according to the maximum power supply capacity (Total Supply Capability, TSC) of the power distribution network.
The feeder line of the distribution network fed out by the transformer substation is generally divided into a plurality of sections, and the terminal of the feeder line is communicated with other feeder lines. The power supply potential of the power distribution network is that the maximum power supply capacity of each link of the transformer substation interval, the feeder line and the feeder line segment of the power distribution network is analyzed, and then the power supply capacity is compared with the existing load size to obtain the accessible capacity. Therefore, the accessible capacity is the capacity that each feeder and main transformer can also access when the N-1 criterion is satisfied, taking into account the rated capacity of the device. In the actual power distribution network expansion work, new loads are accessed at any time, and whether enough residual capacity exists to support the access of the new loads needs to be judged in advance. However, the actual situation is that no effective measuring and calculating means for the available capacity of each stage of the power distribution network exists at present, and only recommended values about the upper limit of the connecting capacity of the power distribution transformer exist in the planning technical principle, so that the actual situation is judged by means of artificial experience, and the situation that the feeder line is excessively connected with load possibly causes a certain potential safety hazard to the operation of the power distribution network; and some feeder lines are too little in access load, so that precious power grid resources are not fully utilized.
TSC is becoming an important index for evaluating a power distribution network, and means the maximum total load of the power distribution network when all feeder N-1 checks of the power distribution network and the main transformer N-1 checks of a transformer substation are met. And during N-1 verification, the actual operation constraint of the power distribution network such as load transfer between main transformers and feeder lines, connection relations between the main transformers and the feeder lines in a network, capacities of the main transformers and the feeder lines, overload coefficients of the main transformers and the like are required to be considered. The paper "maximum power supply capacity model of distribution network based on feeder interconnection relationship", published source is "Automation of electric Power System", 2011,35 (24): 47-52; the main transformer interconnection and the feeder interconnection are fully considered, a strict linear programming mathematical model for calculating the TSC is established, an optimal solution can be obtained, and the TSC solving method closest to the actual condition of the power distribution network at present is also formed.
Besides the total TSC of the power distribution network, the TSC model and calculation can also provide the load distribution conditions on each main transformer and each feed line when the TSC is achieved, and the most balanced load distribution under the TSC can be obtained by further setting a load balancing objective function.
The scientific calculation of the accessible capacity of the power distribution network is an urgent need of the industrial expansion work, and the planning of the power grid and the reconstruction of the power grid are the first precious data for the next step. The practical problem is researched by applying TSC theory, and a new feeder access user capacity calculation method is provided.
Disclosure of Invention
The invention aims to provide a TSC-based feeder access user capacity calculation method, which aims to solve the problem that the feeder access user capacity can only be judged by experience in the prior art.
In order to achieve the purpose, the invention relates to a TSC-based feeder line access user capacity calculation method, which comprises the following steps,
step 1: acquiring the existing load of each feeder line, the load on each feeder line on the primary side and the conversion coefficient between the capacity of the secondary side distribution transformer;
step 2: calculating according to a TSC model to obtain a TSC value;
step 3: calculating according to the feeder model to obtain the theoretical load of each feeder; calculating accessible loads on each feed line according to the theoretical load and the existing load;
the feeder line model takes the maximum number of feeder lines with non-negative accessible loads as an objective function, and takes the condition function of the TSC model combined with the load carried by the power distribution network as the maximum power supply value as a condition function;
the accessible load on the feeder is the difference value between the theoretical load of the feeder and the corresponding existing load;
step 4: judging whether the accessible load on each feeder is non-negative, if so, taking the accessible load on the feeder as the accessible capacity of the corresponding feeder;
step 5: and obtaining the capacity of the access user distribution transformer of the feeder line of the distribution network according to the accessible capacity of each feeder line and the corresponding conversion coefficient.
Preferably, the TSC model in step 2 is:
TSC is the maximum power supply value, F i For the load carried by the main transformer i,
F m is the load of feeder m; t is t rfmn The load quantity of the feeder line N is transferred when the feeder line m has N-1 fault; t is t rtij The load quantity of the main transformer j is transferred when the N-1 fault occurs to the main transformer i; f (F) m ∈T i Representing the corresponding bus of the feeder line m from the main transformer i; f (F) n ∈T j Representing a corresponding bus of the feeder n from the main transformer j; r is R Fn Is the rated capacity of the feeder line n; f (F) n Is the load of the feeder n; r is R j Rated capacity of the main transformer j; l (L) D A lower limit for a load in a heavy load area; z is all main transformer sets of the reloading area.
Preferably, when judging whether the accessible loads on the feed lines are all non-negative, if the judging result is negative, adjusting the position of the sectionalizer switch or the interconnecting switch, updating the accessible loads on the feed lines according to the adjustment of the sectionalizer switch or the interconnecting switch, judging whether the updated accessible loads are all non-negative, and if the judging result is positive, taking the updated accessible loads as the accessible capacity of the corresponding feed lines.
Preferably, the method for adjusting the position of the sectionalizer or the tie switch is as follows: in a feeder segment pair, the tie switch or sectionalizer is moved from a feeder with a positive accessible load to a feeder with a negative accessible load.
Preferably, when the position of the sectionalizer or the tie switch is adjusted, the following condition is satisfied:
wherein δF represents the amount of load change in the feeder segment pair caused by moving the position of the sectionalizer or tie switch;
representing the accessible load with the accessible capacity on the positive side in the feeder segment pair; />
Representing the accessible load on the negative side of the accessible capacity within the feeder segment pair.
Preferably, step 1 further includes a step of setting a scaling factor, and step 4, when judging whether the updated accessible loads are all non-negative, if the judging result is negative, the maximum power supply value is reduced according to the scaling factor, and step 3 is entered.
Preferably, when the maximum power supply value is lowered, the maximum power supply value is lowered to 0.9 times the original maximum power supply value.
Preferably, the access user distribution transformer capacity UAC of the distribution network feeder m is calculated by the following formula:
wherein η is a conversion coefficient between the load on the primary side feeder m and the capacity of the secondary side distribution transformer; ΔF (delta F) m The accessible load on feeder m is the difference between the theoretical load of feeder m and the existing load of feeder m.
Preferably, the conversion factor η is obtained from the user load type, the load type proportion, and the total capacity of the distribution transformer on the feeder m.
Preferably, the step of obtaining the conversion coefficient η from the user load type, the load type proportion, and the total capacity of the distribution transformer on the feeder m is as follows: judging whether the user load type is civil load, commercial load or industrial load;
if it is a civil load, then:
if a commercial load, then:
if a commercial load, then:
in the above, x 1 、x 2 And x 3 The civil load size, the commercial load size and the industrial load size on a certain time section are respectively represented; y is 1 、y 2 And y 3 The total capacity of the civil distribution transformer, the total capacity of the commercial distribution transformer and the total capacity of the industrial distribution transformer are respectively represented; beta represents the optimal load rate of the distribution transformer.
The following beneficial technical effects can be achieved by implementing the invention: the method can calculate the capacity of the feeder line access user distribution transformer, and the feeder line access user distribution transformer calculated according to the method can be accessed, so that the feeder line cannot generate potential safety hazards due to excessive access load, and the power grid resources cannot be fully utilized due to insufficient access coincidence.
Drawings
FIG. 1 is a flow chart of the present invention;
FIG. 2 is a diagram of a cable single ring network before a tie switch is changed in an embodiment of the invention;
FIG. 3 is a diagram of a cable single ring network after a tie switch is changed in an embodiment of the invention;
FIG. 4 is a schematic diagram of a power distribution network in an embodiment of the invention;
FIG. 5 is an actual wiring diagram at P in FIG. 4;
FIG. 6 is an actual wiring diagram of a distribution network circuit in an embodiment of the present invention;
FIG. 7 is a wiring diagram of a feed-line segment pair F2-F16 in an embodiment of the invention;
FIG. 8 is a wiring diagram of a feed-line segment pair F6-F20 in an embodiment of the invention;
fig. 9 is a flow chart of the invention after modification.
Detailed Description
The invention will be further described in conjunction with the following specific examples, which are intended to facilitate an understanding of those skilled in the art:
as shown in fig. 1, the method for calculating the capacity of the feeder access user based on the TSC of the present invention includes the following steps,
step 1: acquiring the conversion coefficient between the existing load of each feeder line, the load on the primary side feeder line and the capacity of the secondary side distribution transformer;
step 2: calculating a maximum power supply value (namely a TSC value) according to the TSC model;
step 3: calculating according to the feeder model to obtain the theoretical load of each feeder; calculating accessible loads on each feed line according to the theoretical load and the existing load;
the feeder line model takes the maximum number of feeder lines with non-negative accessible loads as an objective function, and takes the condition function of the TSC model combined with the load carried by the power distribution network as the maximum power supply value as a condition function;
the accessible load on the feeder is the difference value between the theoretical load of the feeder and the corresponding existing load;
step 4: judging whether the accessible load on each feeder is non-negative, if so, taking the accessible load on the feeder as the accessible capacity of the corresponding feeder;
step 5: and obtaining the capacity of the access user distribution transformer of the feeder line of the distribution network according to the accessible capacity of each feeder line and the corresponding conversion coefficient.
The feeder line can be accessed according to the capacity of the access user distribution transformer of the feeder line of the distribution network, so that potential safety hazards caused by excessive access load of the feeder line can be avoided, and the feeder line can not be fully utilized due to insufficient access coincidence.
In step 1, the conversion coefficient between the load on the primary side feeder and the capacity of the secondary side distribution transformer may be a conversion coefficient between the load on the 10kV side feeder and the capacity of the 0.4kV side distribution transformer.
In step 2, the TSC model may be a TSC model in "maximum power capacity of distribution network model based on feeder interconnection relationship" described in the background art.
The urban distribution network is short in line length and small in voltage drop, and can be further regulated through reactive compensation equipment, so that voltage constraint can be ignored in a TSC model; meanwhile, the feeder outlet load in the TSC model already contains the net loss. In summary, the TSC model simplifies the voltage, reactive power, and other factors, and the simplified TSC model is as follows.
TSC is the maximum power supply value, F i For the load carried by main transformer i, F m Is the load of feeder m; t is t rfmn The load quantity of the feeder line N is transferred when the feeder line m has N-1 fault; t is t rtij The load quantity of the main transformer j is transferred when the N-1 fault occurs to the main transformer i; f (F) m ∈T i Representing the corresponding bus of the feeder line m from the main transformer i; f (F) n ∈T j Representing the pair of feeder n out of main transformer jA bus is used; r is R Fn Is the rated capacity of the feeder line n; f (F) n Is the load of the feeder n; r is R j Rated capacity of the main transformer j; l (L) D A lower limit for a load in a heavy load area; z is all main transformer sets of the heavy load area;
represents any of m, n, ">
Representing any i, j.
In the formula (1):
The objective function of the feeder model is that the maximum number of feeder lines with non-negative accessible load
The condition function of the feeder line model by combining the load carried by the power distribution network with the condition function with the maximum power supply value is taken as the condition function, and the condition function specifically comprises the following steps:
in the above formula, the TSC is the maximum power supply value calculated according to the TSC model, and if the maximum power supply value is reduced by the scaling factor, the TSC is the reduced maximum power supply value.
As shown in fig. 9, in step 4, if the accessible loads on the feed lines are all non-negative, if the judgment result is negative, then: the position of the sectionalizer or the tie switch is adjusted, the accessible load on the feeder is updated according to the adjustment of the sectionalizer or the tie switch (the existing load after the adjustment of the sectionalizer or the tie switch is changed, but the theoretical load is not changed, that is, the accessible load is obtained only by adding or subtracting the change amount corresponding to the existing load, which is known by those skilled in the art, if the accessible load on the feeder is updated according to the adjustment of the sectionalizer or the tie switch, the detailed description is not performed here), whether the updated accessible load is non-negative is judged, if the judgment result is yes, the updated accessible load is taken as the accessible capacity of the corresponding feeder, if the judgment result is no, the TSC value is reduced according to the proportion coefficient, and the step 3 is entered. The scaling factor may be set in step 1, and the scaling factor may be set to 0.9, i.e. after the TSC value is reduced by the scaling factor, the reduced TSC value is 0.9 times the original TSC value; likewise, the scaling factor may be set according to the actual situation. In order to prevent the TSC value from being too small, the capacity of the distribution transformer of the access user is calculated to be too small, a TSC lower limit value can be set, and when the TSC value after reduction is lower than the TSC lower limit value, the capacity of the distribution transformer of the access user is not calculated any more, namely, the capacity of the distribution transformer of the access user is not reasonable.
Specific methods of adjusting the switch position and feeder segment pairs (Dual Feeder Sections, DFS) are explained herein. Starting from both sides of a sectionalizer or a tie switch, the rest of the sectionalizers, tie switches or feeder switches can always be searched in opposite directions, and then the two feeders between the two switches are one feeder section pair. Taking the cable single ring network as an example in fig. 2, the tie switch is B in the ring network cabinet 2, the feeder switch is A, C, two sections of feeders BA and BC are a pair of feeder section pairs, the load of BA section in the feeder section pairs comprises F0, F1 and F2, and the load of BC section comprises F3, F4 and F5.
The feeder may herein be a feeder segment between a switch (sectionalizer or tie switch or feeder switch) and an adjacent switch (sectionalizer or tie switch or feeder switch).
Taking fig. 2 and 3 as an example, assuming that the accessible capacity of the BA feeder is positive and the accessible capacity of the BC feeder is negative, a method for calculating the accessible load
F m ' represents the existing load on feeder m, F m TSC For theoretical load on feeder m, the actual load F in the BA feeder is described m ' theoretical load less than TSC +.>
BC feeder internal actual load F m ' theoretical load when greater than TSC +.>
In a power distribution network, a feeder section pair may be changed by adjusting a tie switchActual load F of feeder line in m ' distribution, obviously, if the actual load F of BC is to be calculated at this time m ' transfer a portion to BA, F of BC at this time m ' reduction, F of BA m 'increasing, it is possible to both fully exploit the accessible load of the BA and to change the accessible load of the BC from negative to positive, so the tie-switch B should be moved towards C, the operation being in contrast to FIGS. 2 and 3, where the tie-switch changes from B to B'. The loads of the B 'a sections in the feeder section pair then comprise F0, F1, F2, F3, and the loads of the B' C sections comprise F4, F5. The moving direction and the moving size of the contact switch need to satisfy the following conditions:
1) The direction is: in a feeder section pair, a tie switch or a sectionalizer is moved from a feeder with positive accessible capacity to a feeder with negative accessible capacity;
2) Size of: after the tie switch or the sectionalizer is adjusted, the load change caused by the adjustment should satisfy the following conditions:
wherein δF represents the amount of load change in the feeder segment pair caused by moving the position of the sectionalizer or tie switch;
representing the accessible load with the accessible capacity on the positive side in the feeder segment pair; />
Representing the accessible load on the negative side of the accessible capacity within the feeder segment pair.
The essence of the feeder segment pair is that the minimum unit for load adjustment is given, the accessible capacity can directly lead to load adjustment in the feeder segment pair, namely, the movement of the position of the contact switch or the sectionalizing switch is guided, the basis of the movement is the formula (2), thus, through the movement of the switch, the power distribution network can have the maximum accessible capacity, and the accessible capacity of each feeder is non-negative.
It should be noted that: 1) The feeder section pair where a certain load is located may be more than one, and the method for selecting the feeder section pair is to preferably select the feeder section pair containing the tie switch; 2) If some feeder sections can be actually operated, the actual situation of the actual power distribution network needs to be considered, and the actual engineering may not meet the requirement of adjusting the switch position, mainly because: (1) the adjustment of the load by the sectionalizer or the tie switch is discrete, and the load variation inequality may not be satisfied all the time; (2) the automation degree of the power distribution network is not completely covered, and time and labor are wasted in adjusting the sectionalizing switch or the interconnection switch.
In step 5: the capacity UAC of the distribution transformer of the access user of the distribution network feeder line m is calculated by the following formula:
wherein η is a conversion coefficient between the load on the primary side feeder m and the capacity of the secondary side distribution transformer, such as a conversion coefficient between the load on the 10kV side feeder and the capacity of the 0.4kV side distribution transformer; ΔF (delta F) m Is the accessible load on feeder m, i.e. the difference between the theoretical load of feeder m and the existing load of feeder m.
η may be obtained using calculation means known in the art. The invention provides a new practical method for calculating a conversion coefficient eta in order to obtain a simple and practical access user capacity calculation method which can be used for avoiding extracting a large amount of original data and calculating any time section. The method of calculating the conversion factor eta is determined based on the load type, the load type ratio, and the total capacity of the distribution transformer on the feeder. Wherein the load types are mainly classified into civil load, commercial load and industrial load, and the classification can be roughly classified according to government land types; the proportion of each load type can be obtained according to the proportion of the total load on different government land types; the total capacity of the distribution transformer can be calculated according to the number and the capacity of the distribution transformer on a known line, namely, the total capacity=the number of the distribution transformers. For example, if the civil load, the commercial load and the industrial load on a certain time section are x respectively for one line 1 MVA，x 2 MVA，x 3 MVA, distribution transformer total capacity is y respectively 1 MVA，y 2 MVA，y 3 MVA, the conversion coefficients for different load types on the line can be calculated according to the following formulas:
in the above-mentioned method, the step of,
conversion coefficient representing civil load, +.>
The calculation coefficients obtained by weighting civil load, commercial load and industrial load according to different load proportions are represented; />
Distribution transformer parameters representing that all line loads can be connected into civil loads, and +.>
The meaning is similar; beta represents the optimal load rate of the distribution transformer, beta is a variable known in the art, and reference can be made to the paper energy conservation of distribution transformers, here: eastern china power, 2010, 38 (9): 1475-1477.
Similarly, for the commercial load conversion factor η Commercial business Conversion coefficient eta of sum industrial load Industrial process The calculation method of (1) is as follows:
the following will take specific examples as examples for further explanation:
in fig. 4, there are 2 substations, 4 main transformers, 20 feeder outgoing lines, 22 feeder loads, respectively denoted as F1 to F22, where the loads refer to concentrated loads on the feeder lines, and there are many loads and switches on the actual feeder lines, and the actual wiring diagram obtained by amplifying the feeder lines in the dashed red frame P in fig. 4 is shown in fig. 5.
The accessible load on each feeder is recorded as ΔF 1 ～ΔF 22 The feeder lines all adopt JKLYJ-185 with the capacity of 11.30MVA. The main transformer data of the transformer substation are shown in table 1.
TABLE 1 Main data
Table 2 shows the current load values of F1 to F22, i.e. the existing loads, for an operating point P of the example distribution network.
Table 2 operating point P
The load distribution at the operating point P is denoted as F m ' at the current load level, the total load size of the distribution network is 49.75MVA.
According to the TSC model, calculating the TSC value of the power grid to be 114.33MVA. The maximum number of feeder lines with non-negative accessible load is taken as an objective function (i.e. the accessible load on the feeder lines
The maximum number of non-negative values is used as an objective function), and a conditional function of a TSC model and 114.33MVA of load carried by the power distribution network are used as conditional functions. Determining the theoretical load of the feed lines, i.e. the load distribution ∈ ->
See table 3, third column,/->
Represents the theoretical load of the feeder m.
TABLE 3 TSC, TSC cut Lower load distribution and accessible load
Taking the first row F1 of the first four columns in Table 3 as an example, solving the theoretical load (load distribution) of the feeder line by the TSC model as F 1 TSC =5.83 MVA, existing load F 1 ' =2.04 MVA, then the accessible load calculation method for F1 is Δf 1 TSC ＝F 1 TSC -F 1 ' =5.83-2.04=3.79 MVA. All accessible loads for F2-F22 are similarly available (column 4). From the last row (top 4 columns) a total load value of 49.75MVA for the current operating point is available, and the total accessible load theoretical value is equal to 114.33 (TSC value) -49.75=64.58 MVA.
Due to column 4
There are 5 negative values and the position of the sectionalizer or tie switch is then adjusted as per step 4. It was found that for this actual distribution network, the negative amount of accessible capacity cannot be completely removed by adjusting the sectionalizer or tie switch positions, for example: taking F22 as an example, the feeder pairs F12-F22 are located at the stippled frame part in fig. 4, and the actual wiring diagram of the power distribution network is shown in fig. 6.
As shown in Table 3, the accessible capacities of F12 and F22 are 7.00MVA and-1.36 MVA respectively, and the load change delta F when the tie switch moves to the F22 side is 1.36 MVA-delta F-7.00 MVA. As can be seen from the actual wiring diagram (MVA in the drawing) of fig. 6, when the tie switch moves toward F22, the minimum value of the discrete load variation of the feeder segment pairs F12-F22 is δf=f3=1.20 MVA, which is smaller than 1.36MVA, and the tie switch is changed from the initial position to 1 or 2; the next smallest value is δf=f3+f4=7.10 MVA, greater than 7.00MVA, when the tie switch is changed from the initial position to 3 or 4; after which δf becomes larger, greater than 7.00MVA. Because δF is not satisfied with 1.36MVA less than or equal to δF less than or equal to 7.00MVA all the time, no matter how the position of the tie switch is regulated, main transformer or feeder overload always occurs in the power distribution network, i.e. the safety of the whole network N-1 is not satisfied. Therefore, for this actual distribution network, there is a negative accessible load even after the position of the sectionalizer or tie switch has been adjusted by steps.
Further. The TSC is reduced to 0.9 times of the original value, so that the TSC value is updated, the updated TSC value is represented by TSCcut, that is, tsccut=0.9×tsc, and tsccut= 102.90MVA is calculated. At this time, the power distribution network obtains the load distribution under TSCcut under the power supply capacity
And accessible capacity->
See fifth and sixth columns of table 3:
as can be seen from table 3, the distribution of the accessible load non-negative values of each feeder is significantly improved by the small amount of TSC reduction adjustment described above,
there are only 2 negative values, which are reduced by 3 negative values before the TSC is reduced. For the case where the accessible load at 2 is negative, feed line segment pair optimization is further employed, i.e., adjusting the position of the sectionalizer or tie switch.
TABLE 3 TSC, TSC cut Lower load distribution and accessible capacity
The accessible loads of F2 and F20 are negative, feeder line segments F2-F16 and F6-F20 where F2 and F20 are located are selected respectively, and because the accessible loads of F2 and F20 are negative, the contact switch is required to move towards F2 and F20 respectively, the moving load change amounts are respectively that MVA is more than or equal to 0.09 and less than or equal to delta F1 and less than or equal to 4.67MVA, delta F2 is more than or equal to 0.86 and less than or equal to 4.62MVA, and detailed wiring diagrams of the feeder line segments F2-F16 and F6-F20 are shown in figures 7 and 8:
as can be seen from the detailed wiring diagram, for the feed line segment pair F2-F16, when the tie switch moves toward the tie switch toward F2, the minimum value of the discrete load variation amount of the feed line segment pair F2-F16 is δf1=f2=0.20 MVA, 0.09MVA is δf1 is smaller than or equal to 4.67MVA, the next minimum value δf1=f2+f1=0.32 MVA, and 0.09MVA is also 0.09MVA is smaller than or equal to δf1 is smaller than or equal to 4.67MVA, and in consideration of the balance of the load distribution, the load variation of δf1=0.20 MVA is selected as the load adjustment amount, so that the tie switch moves to the position of 1 or 2 of fig. 7; for the feed line segment pair F6-F20, when the tie switch is moved toward the tie switch toward F20, the minimum value of the discrete load variation of the feed line segment pair F6-F20 is δf2=f3=2.00 MVA,0.86MVA Σf2 Σ4.62MVA is satisfied, the next smaller value δf2=f3+f4=4.98 MVA is not satisfied, 0.86MVA δf2 δf2=4.62 MVA, so the tie switch is moved to the position of 1 or 2 of fig. 8. At this point, a complete tie switch adjustment scheme is obtained, see table 4.
TABLE 4 TSC cut Lower load adjustment condition and accessible capacity
The method comprises the following steps of: the maximum power supply capacity of the power distribution network of the calculation example is 114.33MVA, the current total load size is 49.75MVA, the power distribution network has 64.58MVA of accessible total capacity, and the initial load distribution of the power distribution network is unreasonable, so that the maximum power supply capacity of the power distribution network is fully utilized, and the accessible capacity which can guide actual engineering (namely, all the power distribution network is non-negative) is obtained, and the following steps are needed:
1) Reducing TSC to 0.9 times of original value, and planning and solving to obtain load distribution with maximum accessible capacity and non-negative value;
2) According to the positive and negative distribution of the accessible capacity, the interconnecting switch is guided to be adjusted (see table 4), the load distribution balance of the working point is improved, the accessible capacity of each feeder line is all non-negative, and the final result is shown in table 5:
TABLE 5 TSC cut Lower all non-negative accessible capacity
According to the accessible capacity of each feeder line in table 5, in combination with the government specified land type, the total capacity of the distribution transformer of each land and the total load of each land in the power supply area on each feeder line, the optimal load rate β of the distribution transformer is 95%, and the optimal load rate of the distribution transformer can be referred to as follows: power conservation in distribution transformers eastern power, 2010, 38 (9): 1475-1477, and obtaining the access user capacities with different load types according to formulas (4), (5) and (6).
Taking the feeder F1 of fig. 3 as an example, the accessible capacity is 2.67MVA according to table 5. The load of the power grid in FIG. 3, which is obtained by calling the data in PMS2.0, is divided into civil load, commercial load and industrial load, the load size is 0.81MVA, 0.72MVA and 0.51MVA respectively, the total load size is 2.04MVA, and the total capacity of the three load types of the access distribution transformer is 1.10MVA, 1.10MVA and 1.05MVA respectively. The load conversion factor of the civil load on line F1 is as follows:
the load conversion coefficients of the commercial load and the industrial load obtained according to the formulas (5) and (6) are eta Commercial business ＝0.65、η Industrial process =0.46. According to formula (3), the calculation results of the access user capacities UAC of the civil load, the commercial load and the industrial load on the feeder line F1 of fig. 3 are respectively: 3.69MVA, 4.08MVA, 5.77MVA. According to the method, the access user capacity of civil load, commercial load and industrial load of the rest feeder lines can be calculated.
The above embodiments are merely illustrative embodiments of the present invention, but the technical features of the present invention are not limited thereto, and any changes or modifications made by those skilled in the art within the scope of the present invention are included in the scope of the present invention.
Claims (8)
1. A method for calculating the capacity of a feeder line access user based on TSC is characterized in that: comprises the following steps of the method,
step 1: acquiring the existing load of each feeder line, the load on each feeder line on the primary side and the conversion coefficient between the capacity of the secondary side distribution transformer;
step 2: calculating according to the TSC model to obtain a maximum power supply value;
step 3: calculating according to the feeder model to obtain the theoretical load of each feeder; calculating accessible loads on each feed line according to the theoretical load and the existing load;
the feeder line model takes the maximum number of feeder lines with non-negative accessible loads as an objective function, and takes the condition function of the TSC model combined with the load carried by the power distribution network as the maximum power supply value as a condition function;
the accessible load on the feeder is the difference value between the theoretical load of the feeder and the corresponding existing load;
step 4: judging whether the accessible load on each feeder is non-negative, if so, taking the accessible load on the feeder as the accessible capacity of the corresponding feeder;
step 5: obtaining the capacity of an access user distribution transformer of the feeder line of the distribution network according to the accessible capacity of each feeder line and the corresponding conversion coefficient;
judging whether the accessible loads on all the feed lines are non-negative, if the judging result is negative, adjusting the position of the sectionalizing switch or the interconnecting switch, updating the accessible loads on the feed lines according to the adjustment of the sectionalizing switch or the interconnecting switch, judging whether the updated accessible loads are non-negative, and if the judging result is positive, taking the updated accessible loads as the accessible capacity of the corresponding feed lines;
and step 1, setting a proportion coefficient, wherein in step 4, when the updated accessible loads are all non-negative, if the updated accessible loads are not negative, the maximum power supply value is reduced according to the proportion coefficient, and step 3 is carried out.
2. The TSC-based feeder access user capacity calculation method of claim 1, wherein: the TSC model in step 2 is:
TSC is the maximum power supply value, fi is the load carried by main transformer i, F m Is the load of feeder m; t is t rfmn The load quantity of the feeder line N is transferred when the feeder line m has N-1 fault; t is t rtij The load quantity of the main transformer j is transferred when the N-1 fault occurs to the main transformer i; f (F) m ∈T i Representing the corresponding bus of the feeder line m from the main transformer i; f (F) n ∈T j Representing a corresponding bus of the feeder n from the main transformer j; r is R Fn Is the rated capacity of the feeder line n; f (F) n Is the load of the feeder n; r is R j Rated capacity of the main transformer j; l (L) D A lower limit for a load in a heavy load area; z is all main transformer sets of the reloading area.
3. The TSC-based feeder access user capacity calculation method of claim 1, wherein: the method for adjusting the position of the sectionalizer or the tie switch comprises the following steps: in a feeder segment pair, the tie switch or sectionalizer is moved from a feeder with a positive accessible load to a feeder with a negative accessible load.
4. A method for calculating the capacity of a feeder access user based on a TSC as claimed in claim 3, wherein: when the position of the sectionalizer or the tie switch is adjusted, the following conditions are satisfied:
wherein δF represents the amount of load change in the feeder segment pair caused by moving the position of the sectionalizer or tie switch;
representing the accessible load with the accessible capacity on the positive side in the feeder segment pair; />
Representing the accessible load on the negative side of the accessible capacity within the feeder segment pair.
5. The TSC-based feeder access user capacity calculation method of claim 1, wherein: when the maximum power supply value is reduced, the maximum power supply value is reduced to 0.9 times of the original maximum power supply value.
6. The TSC-based feeder access user capacity calculation method of claim 1, wherein: the capacity UAC of the distribution transformer of the access user of the distribution network feeder line m is calculated by the following formula:
wherein eta is the conversion between the load on the primary feeder m and the capacity of the secondary distribution transformerCoefficients; ΔF (delta F) m The accessible load on feeder m is the difference between the theoretical load of feeder m and the existing load of feeder m.
7. The TSC-based feeder access user capacity calculation method of claim 6, wherein: the conversion factor η is obtained from the user load type, the load type ratio, and the total capacity of the distribution transformer on the feeder m.
8. The TSC-based feeder access user capacity calculation method of claim 7, wherein: the step of obtaining a conversion coefficient eta based on the user load type, the load type proportion, and the total capacity of the distribution transformer on the feeder m is as follows: judging whether the user load type is civil load, commercial load or industrial load, if the user load type is civil load, then:
if a commercial load, then:
in the above formula, x1, x2 and x3 respectively represent civil load size, commercial load size and industrial load size on a certain time section; y1, y2 and y3 represent the total capacity of the civil distribution transformer, the total capacity of the commercial distribution transformer and the total capacity of the industrial distribution transformer, respectively; beta represents the optimal load rate of the distribution transformer.
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