CN117436222B - Method and system for calculating maximum power supply capacity of power distribution network - Google Patents

Abstract

The invention belongs to the technical field of power distribution network planning, and discloses a method and a system for calculating the maximum power supply capacity of a power distribution network, wherein the calculating method comprises the following steps: determining the main transformer acting capacity of the maximum power supply capacity of the power distribution network according to network parameters of the power distribution network; determining main transformer capacity configuration according to main transformer acting capacity and feeder line capacity; dividing a safety boundary according to main transformer capacity and main transformer acting capacity in main transformer capacity configuration, and establishing a power distribution network maximum power supply capacity calculation model; the power distribution network maximum power supply capacity calculation model comprises a maximum power supply capacity calculation model containing main transformer constraints and a maximum power supply capacity calculation model neglecting the main transformer constraints; and solving a calculation model of the maximum power supply capacity of the power distribution network to obtain the maximum power supply capacity of the power distribution network. The invention discloses an influence mechanism of the main transformer capacity on the maximum power supply capacity, and provides a quantification criterion whether the main transformer constraint can be ignored in the modeling and calculation of the maximum power supply capacity of the power distribution network, so that the modeling of the maximum power supply capacity is simplified and the calculation is faster.

Description

Method and system for calculating maximum power supply capacity of power distribution network

Technical Field

The invention belongs to the technical field of power distribution network planning, and particularly relates to a method and a system for calculating the maximum power supply capacity of a power distribution network.

Background

The maximum power supply capacity (Total Supply Capability, TSC) is an important indicator of the distribution network, defined as the maximum load supply capacity of the distribution network that meets a given safety criterion. The maximum power supply capacity is mainly formed by a main transformer (main transformer for short) of a transformer substation and a power distribution network. Regarding the influence of a power distribution network on TSC, various researches exist, and the TSC is influenced by the contact position, scale and construction sequence; under the same contact scale, the larger the contact weighting balance degree is, the larger the TSC is; under the optimal contact position, when the contact number is increased from 0 to 70% -80% of the maximum contact number, the TSC reaches the maximum; under normal construction sequences, TSC slowly rises in waves after a rapid linear increase.

There is a great lack of research on the influence of main transformers on TSCs. In the small calculation example of most theoretical researches, the main transformer has fewer feeder lines, the main transformer constraint is simplified and deleted in modeling, and finally the influence of the main transformer on TSC is not reflected. In practical distribution networks, particularly in urban as-built area distribution networks, the outgoing line scale has reached or approached its final scale, and the effect of the main transformer on the TSC is not negligible. In some existing TSC studies, the example is out of line enough, the TSC results reflect the main transformer constraint, but the influence of the main transformer on the TSC is not analyzed.

Disclosure of Invention

Aiming at the problems, the invention provides a method and a system for calculating the maximum power supply capacity of a power distribution network, which adopts the following technical scheme:

A calculation method of the maximum power supply capacity of a power distribution network comprises the following steps: determining the main transformer acting capacity of the maximum power supply capacity of the power distribution network according to network parameters of the power distribution network; determining main transformer capacity configuration according to main transformer acting capacity and feeder line capacity; dividing a safety boundary according to main transformer capacity and main transformer acting capacity in main transformer capacity configuration, and establishing a power distribution network maximum power supply capacity calculation model; the power distribution network maximum power supply capacity calculation model comprises a maximum power supply capacity calculation model containing main transformer constraints and a maximum power supply capacity calculation model neglecting the main transformer constraints; and solving a calculation model of the maximum power supply capacity of the power distribution network to obtain the maximum power supply capacity of the power distribution network.

Further, determining the main transformer acting capacity of the maximum power supply capacity of the power distribution network according to the network parameters of the power distribution network, wherein the main transformer acting capacity comprises the following steps:

And determining the active capacity of the main transformer according to the maximum outgoing line number of the main transformer in the power distribution network and the feeder capacity of the main transformer with the maximum outgoing line number.

Further, according to the main transformer acting capacity and the feeder line capacity, the main transformer capacity configuration is determined, and the method comprises the following steps:

And determining the lower limit of the main transformer capacity as feeder capacity, and dividing the main transformer capacity configuration into a first main transformer capacity configuration, a second main transformer capacity configuration, a third main transformer capacity configuration and a fourth main transformer capacity configuration.

Further, the main transformer capacity in the first main transformer capacity configuration is larger than the main transformer acting capacity, the main transformer capacity in the second main transformer capacity configuration is equal to the main transformer acting capacity, the main transformer capacity in the third main transformer capacity configuration is between the feeder capacity and the main transformer acting capacity, and the main transformer capacity in the fourth main transformer capacity configuration is equal to the feeder capacity.

Further, according to the main transformer capacity and the main transformer acting capacity in the main transformer capacity configuration, dividing a safety boundary and establishing a calculation model of the maximum power supply capacity of the power distribution network, comprising the following steps:

And when the main transformer capacity is larger than or equal to the main transformer acting capacity in the main transformer capacity configuration, establishing a maximum power supply capacity calculation model neglecting the main transformer constraint.

Further, dividing a safety boundary and establishing a calculation model of the maximum power supply capacity of the power distribution network according to the main transformer capacity and the main transformer acting capacity in the main transformer capacity configuration, and further comprising the following steps:

When the main transformer capacity is smaller than the main transformer acting capacity in the main transformer capacity configuration, determining a safety boundary expression and dividing the safety boundary type, if a feeder boundary exists in the safety boundary type, establishing a maximum power supply capacity calculation model neglecting the main transformer constraint, otherwise, establishing a maximum power supply capacity calculation model containing the main transformer constraint.

Further, the security boundary types also include a hybrid boundary and a main transformer boundary.

Further, when the main transformer capacity is smaller than the main transformer acting capacity in the main transformer capacity configuration, determining a safety boundary expression and dividing the safety boundary type, including the following steps:

Dividing the safe boundary expression into a feeder critical equation and a main transformer critical equation according to the type of the medium-number right constant in the safe boundary expression;

the security boundary types are divided into feeder boundaries, hybrid boundaries and main transformer boundaries according to feeder critical equations and main transformer critical equations.

Further, the right constant of the equal sign in the feeder critical equation is the feeder capacity, and the right constant of the equal sign in the main transformer critical equation is the main transformer capacity.

Further, the feeder boundary includes only the boundary of the feeder critical equation, the main transformer boundary includes only the boundary of the main transformer critical equation, and the hybrid boundary includes the boundary of the feeder critical equation and the main transformer critical equation.

Further, a maximum power supply capacity calculation model containing main transformer constraints is established, and the method comprises the following steps:

and taking the maximum load of the power distribution network as an objective function, taking the feeder constraint of the feeder N-1 and the main transformer constraint checked by the main transformer N-1 as constraint conditions, and establishing a maximum power supply capacity calculation model containing the main transformer constraint.

Further, a maximum power supply capacity calculation model neglecting main transformer constraint is established, and the method comprises the following steps:

and removing the main transformer constraint in the maximum power supply capacity calculation model containing the main transformer constraint to obtain the maximum power supply capacity calculation model neglecting the main transformer constraint.

Further, the main transformer acting capacity is determined according to the maximum line outgoing number of the main transformer and the feeder line capacity of the main transformer with the maximum line outgoing number in the power distribution network, and the method specifically comprises the following steps:

Wherein R _op represents the main transformer operating capacity, And c represents the feeder capacity of the main transformer of the maximum outgoing line number of the power distribution network.

The invention also provides a power distribution network maximum power supply capacity computing system, which comprises:

The first calculation module is used for determining the main transformer acting capacity of the maximum power supply capacity of the power distribution network according to the network parameters of the power distribution network;

the second calculation module is used for determining main transformer capacity configuration according to the main transformer acting capacity and the feeder line capacity;

The third calculation module is used for dividing a safety boundary and establishing a calculation model of the maximum power supply capacity of the power distribution network according to the main transformer capacity and the main transformer acting capacity in the main transformer capacity configuration; the power distribution network maximum power supply capacity calculation model comprises a maximum power supply capacity calculation model containing main transformer constraints and a maximum power supply capacity calculation model neglecting the main transformer constraints;

And the fourth calculation module is used for solving a calculation model of the maximum power supply capacity of the power distribution network to obtain the maximum power supply capacity of the power distribution network.

Further, the first computing module is specifically configured to:

And determining the active capacity of the main transformer according to the maximum outgoing line number of the main transformer in the power distribution network and the feeder capacity of the main transformer with the maximum outgoing line number.

Further, the third computing module is specifically configured to:

And when the main transformer capacity is larger than or equal to the main transformer acting capacity in the main transformer capacity configuration, establishing a maximum power supply capacity calculation model neglecting the main transformer constraint.

The invention has the beneficial effects that: the invention discloses an influence mechanism of main transformer capacity on maximum power supply capacity, provides a quantification criterion for whether main transformer constraint can be ignored in modeling and calculation of the maximum power supply capacity of the power distribution network, and simplifies the modeling of the maximum power supply capacity and calculates more quickly for the power distribution network meeting the criterion. Under the scenes of planning, regulating and controlling the power distribution network, operation and maintenance and the like, the method can be used for obtaining the maximum power supply capacity of the power distribution network more quickly, and is particularly suitable for the scene with larger power distribution network scale.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and drawings.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the following description will briefly explain the drawings used in the embodiments or the description of the prior art, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic flow chart of a method for calculating a maximum power supply capacity of a power distribution network according to an embodiment of the present invention;

fig. 2 is a detailed flowchart of a method for calculating a maximum power supply capacity of a power distribution network according to an embodiment of the present invention;

FIG. 3 shows a schematic diagram of a network architecture of a single-connection patch cord in accordance with an embodiment of the present invention;

FIG. 4 is a schematic diagram of a two-wire-for-one network according to an embodiment of the present invention;

fig. 5 shows a network structure schematic diagram of a substation common to an urban distribution network according to an embodiment of the invention;

Fig. 6 shows a schematic structural diagram of a power distribution network maximum power supply capability computing system according to an embodiment of the present invention.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

It should be noted that the terms "first," "second," and the like herein are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate in order to describe the embodiments of the application herein.

The invention provides a method and a system for calculating the maximum power supply capacity of a power distribution network by analyzing the influence mechanism of a main transformer on the maximum power supply capacity, which can help judge whether the modeling calculation of the maximum power supply capacity of the power distribution network can ignore the constraint of the main transformer or not, and realize simplified modeling and rapid calculation of the maximum power supply capacity. Under the scenes of planning, regulating and controlling, operation and maintenance of the power distribution network, the method and the system can obtain the maximum power supply capacity of the power distribution network more quickly, and are particularly suitable for the scene with larger power distribution network scale.

As shown in fig. 1 and 2, a method for calculating a maximum power supply capacity of a power distribution network includes the following steps:

s1, determining main transformer acting capacity of the maximum power supply capacity of the power distribution network according to network parameters of the power distribution network comprises the following steps: the main transformer acting capacity is determined according to the maximum outgoing line number of the main transformer and the feeder line capacity of the main transformer with the maximum outgoing line number in the power distribution network, and is specifically as follows:

Wherein R _op represents the main transformer operating capacity, And c represents the feeder capacity of the main transformer with the maximum number of outgoing lines of the power distribution network.

The maximum capacity of the main transformer capacity affecting the maximum power supply capacity (TSC) of the power distribution network is the main transformer acting capacity, which is obtained by the above method and is related to the maximum wire outlet number and feeder capacity only, and is unrelated to the wiring mode, the main transformer capacity and the voltage level.

S2, determining main transformer capacity configuration according to main transformer acting capacity and feeder line capacity, wherein the main transformer capacity configuration is specifically as follows:

Determining the lower limit of the main transformer capacity as the feeder capacity, dividing the main transformer capacity configuration into a first main transformer capacity configuration, a second main transformer capacity configuration, a third main transformer capacity configuration and a fourth main transformer capacity configuration, wherein the main transformer capacity in the first main transformer capacity configuration is larger than the main transformer acting capacity, the main transformer capacity in the second main transformer capacity configuration is equal to the main transformer acting capacity, the main transformer capacity in the third main transformer capacity configuration is between the feeder capacity and the main transformer acting capacity, and the main transformer capacity in the fourth main transformer capacity configuration is equal to the feeder capacity.

Of the 4 main transformer capacity configurations determined above, the second main transformer capacity configuration and the fourth main transformer capacity configuration are both theoretical extreme cases, and the first main transformer capacity configuration and the third main transformer capacity configuration are actual cases of the power distribution network.

S3, dividing a safety boundary and establishing a power distribution network maximum power supply capacity calculation model according to the main transformer capacity and the main transformer acting capacity in the main transformer capacity configuration; the power distribution network maximum power supply capacity calculation model comprises a maximum power supply capacity calculation model containing main transformer constraints and a maximum power supply capacity calculation model neglecting the main transformer constraints, and specifically comprises the following steps:

And S31, when the main transformer capacity is larger than or equal to the main transformer acting capacity in the main transformer capacity configuration, the maximum power supply capacity is not changed along with the change of the main transformer capacity, and a maximum power supply capacity calculation model neglecting the main transformer constraint is established.

When the main transformer capacity is larger than or equal to the main transformer acting capacity, the main transformer constraint is not acted, the maximum power supply capacity cannot be changed along with the change of the main transformer capacity, and the main transformer constraint can be ignored in the modeling calculation process. When the main transformer capacity is smaller than the main transformer acting capacity, the type of the safety boundary needs to be further judged.

S32, when the main transformer capacity is smaller than the main transformer acting capacity in the main transformer capacity configuration, determining a safety boundary expression and dividing safety boundary types, wherein the safety boundary types comprise feeder line boundaries, mixed boundaries and main transformer boundaries, and specifically comprise the following steps:

S321, dividing the safety boundary expression into a feeder critical equation and a main transformer critical equation according to the type of the constant on the right side of the medium number in the safety boundary expression.

The right constant of the equal sign in the feeder critical equation is feeder capacity, and the feeder critical equation means that the feeder capacity constraint critical is achieved after the power distribution network generates N-1, namely, the feeder load exceeds the feeder capacity after the N-1 is increased by any load.

The right constant of the equal sign in the main transformer critical equation is the main transformer capacity, and the main transformer critical equation means that the power distribution network reaches the critical of the main transformer constraint after N-1 occurs, namely, the main transformer load exceeds the main transformer capacity after N-1 due to the increase of any load.

S322, dividing the safety boundary types into a feeder boundary, a hybrid boundary and a main transformer boundary according to the feeder critical equation and the main transformer critical equation.

Where the feeder boundary contains only the boundary of the feeder critical equation, i.e. only the feeder capacity constraint is active. The main transformer boundaries only contain boundaries of main transformer critical equations, i.e. only main transformer constraints are active. The hybrid boundary contains both the boundary of the feeder critical equation and the main transformer critical equation, i.e., both the feeder capacity constraint and the main transformer constraint are active.

And S33, when the main transformer capacity in the main transformer capacity configuration is smaller than the main transformer acting capacity, determining a safety boundary type in the main transformer capacity configuration, if a feeder boundary exists in the safety boundary type, determining to establish a maximum power supply capacity calculation model neglecting the main transformer constraint, otherwise, establishing a maximum power supply capacity calculation model containing the main transformer constraint.

It can be seen that both the main transformer boundary and the hybrid boundary contain main transformer critical equations, any increase in load will cause the main transformer load to exceed the main transformer capacity, so that a decrease in the main transformer capacity will make both types of boundaries more stringent, and the load supply capacity of the operating point on the corresponding boundary will decrease. The feeder boundary only contains the feeder critical equation, the main transformer capacity does not affect the feeder boundary, and the load supply capacity does not decrease with the decrease of the main transformer capacity. Three types of security boundaries are relaxed to strict ordering: feeder boundary > hybrid boundary > main transformer boundary. The maximum power supply capability should be taken out of one of the three types of boundaries in this order, and if a feeder boundary exists, the maximum power supply capability is taken out of the most relaxed feeder boundary, and is not taken out of the mixed boundary and the main transformer boundary, which means that the maximum power supply capability is not affected by main transformation. Therefore, modeling calculation of the maximum power supply capacity can ignore the main transformer constraint at the moment, and otherwise, the main transformer constraint cannot be ignored.

The method comprises the following steps of: and taking the maximum load of the power distribution network as an objective function, taking the feeder constraint of the feeder N-1 and the main transformer constraint checked by the main transformer N-1 as constraint conditions, and establishing a maximum power supply capacity calculation model containing the main transformer constraint.

The method comprises the following steps of: and removing the main transformer constraint in the maximum power supply capacity calculation model containing the main transformer constraint, obtaining the maximum power supply capacity calculation model neglecting the main transformer constraint, and completing the simplification of the model.

The method comprises the steps of firstly establishing a maximum power supply capacity calculation model containing main transformer constraints, taking the maximum load of a power distribution network as an objective function, taking the condition meeting the check of a feeder line N-1 and a main transformer N-1 as a constraint condition, then judging whether the main transformer constraints in the model can be ignored, and if so, simplifying the calculation model to obtain the maximum power supply capacity calculation model neglecting the main transformer constraints.

S4, solving a calculation model of the maximum power supply capacity of the power distribution network to obtain the maximum power supply capacity of the power distribution network, wherein the calculation model is specifically as follows:

For example, a maximum power supply capacity calculation model neglecting main transformer constraints and a maximum power supply capacity calculation model containing main transformer constraints are solved respectively, and the maximum power supply capacity of the power distribution network under each main transformer capacity configuration is obtained.

The invention reveals the influence mechanism of the main transformer on the maximum power supply capacity, and firstly gives a quantitative criterion for judging whether the modeling calculation of the maximum power supply capacity of the power distribution network can ignore the constraint of the main transformer, thereby achieving the advantages of simplifying the maximum power supply capacity model and the calculation method, and leading the results to be equal before and after simplification.

For example, the method for calculating the maximum power supply capacity of the power distribution network is applied to a network structure with single connection wires, as shown in fig. 3, F1-F4 are feeder lines, and T1-T3 are main transformers.

1. Calculating main transformer acting capacity

As shown in fig. 3, in the network structure of the single-connection wiring calculation example, in the calculation example, the maximum number of outgoing lines of the main transformer T1 is 2, the feeder capacity is 10MVA, and the main transformer active capacity is calculated:

(1)

2. Main transformer capacity configuration

Main transformer active capacity R _op = 20MVA, actual power distribution network main transformer capacity is not smaller than feeder line capacity, 10MVA is main transformer capacity selection lower limit, 4 representative main transformer capacity configurations are selected, as shown in table 1, and table 1 shows main transformer capacity configurations of single-network wiring.

TABLE 1

Of the above 4 configurations, the second main transformer capacity configuration and the fourth main transformer capacity configuration are both theoretical extreme cases, and the first main transformer capacity configuration and the third main transformer capacity configuration are actual cases of the power distribution network.

3. Construction of safety boundaries under different main transformer configurations

For the case that the main transformer capacity is smaller than the main transformer acting capacity, the boundary area is calculated, the composition analysis is carried out on various boundaries, and the boundary composition of the single-connection wiring is shown in table 2. The main transformer capacity of the first main transformer capacity configuration and the second main transformer capacity configuration is larger than or equal to the main transformer working capacity, and boundary composition analysis is not needed.

TABLE 2

4. Maximum power capability TSC calculation

When the main transformer capacity is equal to or greater than the main transformer acting capacity (the first main transformer capacity configuration and the second main transformer capacity configuration), the maximum power supply capacity does not change with the change of the main transformer capacity, and the main transformer constraint does not play a role and can be ignored.

When the main transformer capacity is smaller than the main transformer active capacity (the third main transformer capacity configuration and the fourth main transformer capacity configuration), as can be seen from table 2, a feeder boundary exists in the safety boundary, and the main transformer constraint can be ignored according to the criteria of the invention.

Taking the first main transformer capacity configuration as an example, establishing a maximum power supply capacity calculation model containing main transformer constraints:

(2)

in the method, in the process of the invention, ～/>The loads of the feeder lines F1 to F4 are shown, respectively.

(3)

The formulas (2) and (3) are respectively an objective function and a constraint condition, the formulas (3-1) and (3-2) are feeder constraint, and the formulas (3-3) and (3-4) are main transformer constraint.

The main transformer capacity is larger than or equal to the main transformer acting capacity, the main transformer constraint is negligible, the simplification of the first main transformer capacity configuration is a maximum power supply capacity calculation model for neglecting the main transformer constraint, and the method specifically comprises the following steps:

(4)

(5)

the second main variable capacity configuration is the same as the first main variable capacity configuration. Feeder line boundaries exist in the safety boundaries of the third main transformer capacity configuration and the fourth main transformer capacity configuration, and main transformer constraints are negligible. The simplified maximum power capability calculation model ignoring the main transformer constraint for the 4 configurations is the same. After simplification, the number of constraints on the model is reduced by half.

And solving a maximum power supply capacity calculation model neglecting the main transformer constraint to obtain the maximum power supply capacity of 20MVA. The maximum power supply capacity obtained before and after model simplification is equal.

For example, the method for calculating the maximum power supply capacity of the power distribution network is applied to a network structure of a two-supply one-standby wiring calculation example, as shown in fig. 4, F2, F3 and F5 form two-supply one-standby, and F3 is a standby feeder line; f1, F4 and F6 form two standby feeders, F4 is a standby feeder, and T1-T3 represent main transformers.

5. Calculating main transformer acting capacity

As shown in fig. 4, in this example, the number of lines of each main transformer is the same, the maximum number of lines is 2, the feeder capacity is 10MVA, and the main transformer operating capacity is calculated:

(6)

6. Main transformer capacity configuration

Main transformer active capacity R _op =20mva, 10mva is the main transformer capacity selection lower limit, and 4 representative main transformer capacity configurations are selected, as shown in table 3, table 3 shows the main transformer capacity configurations of two supply and one standby wire:

TABLE 3 Table 3

Of the above 4 configurations, the second main transformer capacity configuration and the fourth main transformer capacity configuration are both theoretical extreme cases, and the first main transformer capacity configuration and the third main transformer capacity configuration are actual cases of the power distribution network.

7. Construction of safety boundaries under different main transformer configurations

By calculating the boundary area, the composition analysis is performed on various boundaries, and the boundary composition of two-supply-one-standby wiring is shown in table 4.

TABLE 4 Table 4

8. Analysis calculation of maximum power capability TSC

When the main transformer capacity is equal to or greater than the main transformer acting capacity (the first main transformer capacity configuration and the second main transformer capacity configuration), the maximum power supply capacity does not change with the change of the main transformer capacity, and the main transformer constraint does not play a role and can be ignored. Exactly as in the single-connection mode.

When the main transformer capacity is smaller than the main transformer active capacity (the third main transformer capacity configuration and the fourth main transformer capacity configuration), as can be seen from table 4, the feeder line boundary is not present in the safety boundary, and only the main transformer boundary is judged according to the method of the invention, and the main transformer constraint cannot be ignored at this time.

Establishing a maximum power supply capacity calculation model containing main transformer constraints:

(7)

(8)

Wherein R represents the main transformer capacity under each configuration, ～/>The loads of the feeder lines F1 to F6 are shown, respectively.

And judging that the main transformer constraints of the first main transformer capacity configuration and the second main transformer capacity configuration are negligible, and establishing a maximum power supply capacity calculation model for omitting the main transformer constraints as follows:

(9)

(10)

after the model is simplified, the number of constraint conditions is reduced, the complexity of the model is reduced, and the calculation efficiency of the maximum power supply capacity is improved. And calculating the maximum power supply capacity of the first main transformer capacity configuration and the second main transformer capacity configuration to be 40MVA, wherein the results obtained before and after model simplification are equal.

The maximum power supply capacity calculation model of the third main transformer capacity configuration and the fourth main transformer capacity configuration cannot ignore the main transformer constraint, and the model is directly calculated, so that the maximum power supply capacity of the third main transformer capacity configuration and the fourth main transformer capacity configuration is 30MVA and 20MVA respectively.

For example, the calculation method of the maximum power supply capacity of the power distribution network is applied to a common 110kV/10kV transformer substation of an urban power distribution network, wherein one transformer substation is provided with 2-3 main transformers, and the single main transformer is common 50MVA or 40MVA. The final scale of each main transformer has 8-12 loops of 10kV outgoing lines, and the single loop of outgoing line capacity is about 8MVA. The power distribution network calculation example comprises 2 110kV substations, each substation has 2 main transformers, the number of lines of each main transformer is 10, the lines of each main transformer are connected in a single-network mode, the network structure is shown in fig. 5, S1 and S2 in fig. 5 respectively represent the substations, T1-T4 represent the main transformers, and feeder lines comprise 1-40.

Table 5 shows that the main transformer line number range of the distribution network is 8-12 cycles, the feeder line capacity range is 6-10 MVA, the maximum line number and feeder line capacity of the main transformer in the calculation example are changed under the range, and the range of the main transformer acting capacity is calculated.

TABLE 5

As can be seen from table 5, for the distribution network with the main transformer acting capacity ranging from 48MVA to 120MVA, in the combined scene of the maximum line number and the feeder line capacity, the acting capacity of most scenes is greater than 50MVA, at this time, the main transformer constraint cannot be directly ignored, the boundary structure needs to be judged first, and if the feeder line boundary exists in the boundary, the main transformer constraint cannot be ignored in the calculation of the maximum power supply capacity, otherwise.

When the maximum line outgoing number is 8 times, the feeder line capacity is 6MVA, the main transformer acting capacity is 48MVA, if a 40MVA main transformer is adopted in a 110kV transformer substation, the main transformer constraint cannot be directly ignored, and the boundary formation condition is to be judged; if the 50MVA main transformer is adopted, the maximum power supply capacity is not affected, and the modeling calculation can ignore the main transformer constraint.

The existing high-voltage distribution transformer substation has voltage levels of 63kV, 35kV and the like, the main transformer capacity is smaller, and main transformer constraint cannot be directly ignored when the maximum power supply capacity is calculated.

For some distribution networks, the number of outgoing lines of the transformer substation is small, and table 6 is the range of the active capacity of the main transformer when the range of the number of outgoing lines of the main transformer is 3-7 turns and the range of the feeder capacity is 6-10 MVA.

TABLE 6

Note that: the main transformation action capacity R _op of the thickening part is between 40MVA and 50 MVA; the main transformer action capacity R _op at the left side of the part is smaller than 40MVA; the main transformer operating capacity R _op on the right side of the section is greater than 50MVA.

As can be seen from Table 6, the main transformer operating capacity of the distribution network is obviously reduced, and the range is 18 MVA-70 MVA. In the combined scene of the maximum line number and the feeder line capacity, the main transformer acting capacity of about half of the scenes is smaller than 40MVA, which means that the main transformer generally does not influence the power supply capacity, and the main transformer constraint can be omitted in the modeling calculation of the maximum power supply capacity to simplify the calculation.

Table 6 shows that the main transformer operating capacity is between 40 and 50MVA in the combination of the thickened portions. If a 40MVA main transformer is adopted in a 110kV transformer substation, main transformer constraint cannot be directly ignored, and the boundary formation condition is to be judged; if the 50MVA main transformer is adopted, the maximum power supply capacity is not affected, and the modeling calculation can ignore the main transformer constraint. When the maximum line number is more (6-7), the feeder line capacity is more (8-10 MVA), the main transformer acting capacity is more than 50MVA, and the main transformer constraint cannot be directly ignored when the maximum power supply capacity is calculated.

For clearer and more visual display, the simplicity brought by modeling calculation of maximum power supply capacity by main transformer constraint is ignored, the network structure of fig. 5 is taken as an example, the feeder capacity is 8MVA, the main transformer capacity is represented by R, and a maximum power supply capacity calculation model containing the main transformer constraint is listed.

(11)

(12)

(13)/>

(14)

Equations (12) and (13) represent the feeder constraint and the main transformer constraint respectively,Respectively representing the load of the feeder m.

The method provided by the invention is adopted to judge, the main transformer constraint is ignored, the number of inequality in the constraint conditions of the model is reduced from 32 to 20, and the complexity of the model is greatly reduced. The model solution was performed with a maximum power supply capacity of 160MVA. The results obtained before and after model simplification are equal.

Based on the method for calculating the maximum power supply capacity of the power distribution network, as shown in fig. 6, the invention further provides a system for calculating the maximum power supply capacity of the power distribution network, which comprises a first calculation module, a second calculation module, a third calculation module and a fourth calculation module.

The first calculation module is used for determining the main transformer acting capacity of the maximum power supply capacity of the power distribution network according to network parameters of the power distribution network; the second calculation module is used for determining main transformer capacity configuration according to the main transformer acting capacity and the feeder line capacity; the third calculation module is used for dividing a safety boundary and establishing a calculation model of the maximum power supply capacity of the power distribution network according to the main transformer capacity and the main transformer acting capacity in the main transformer capacity configuration; and the fourth calculation module is used for solving a calculation model of the maximum power supply capacity of the power distribution network to obtain the maximum power supply capacity of the power distribution network.

The invention reveals the influence mechanism of the main transformer capacity on the maximum power supply capacity, gives out a quantitative criterion whether the main transformer constraint can be ignored in the modeling and calculation of the maximum power supply capacity of the power distribution network, and simplifies the modeling of the maximum power supply capacity and calculates the maximum power supply capacity more quickly for the power distribution network meeting the criterion. Under the scenes of planning, regulating and controlling the power distribution network, operation and maintenance and the like, the method can be used for obtaining the maximum power supply capacity of the power distribution network more quickly, and is particularly suitable for the scene with larger power distribution network scale.

Although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (6)

1. The method for calculating the maximum power supply capacity of the power distribution network is characterized by comprising the following steps of:

The main transformer acting capacity of the maximum power supply capacity of the power distribution network is determined according to the network parameters of the power distribution network, and the main transformer acting capacity comprises the following steps: the main transformer action capacity is determined according to the maximum outgoing line number of the main transformer and the feeder line capacity of the main transformer with the maximum outgoing line number in the power distribution network, and is specifically as follows:

Wherein R _op represents the main transformer operating capacity, The maximum outgoing line number of the main transformer in the power distribution network is represented, and c represents the feeder line capacity of the main transformer with the maximum outgoing line number of the power distribution network;

According to the main transformer acting capacity and the feeder line capacity, determining the main transformer capacity configuration comprises the following steps: determining the lower limit of the main transformer capacity as feeder capacity, and dividing the main transformer capacity configuration into a first main transformer capacity configuration, a second main transformer capacity configuration, a third main transformer capacity configuration and a fourth main transformer capacity configuration; the main transformer capacity in the first main transformer capacity configuration is larger than the main transformer acting capacity, the main transformer capacity in the second main transformer capacity configuration is equal to the main transformer acting capacity, the main transformer capacity in the third main transformer capacity configuration is between the feeder capacity and the main transformer acting capacity, and the main transformer capacity in the fourth main transformer capacity configuration is equal to the feeder capacity;

Dividing a safety boundary according to main transformer capacity and main transformer acting capacity in main transformer capacity configuration, and establishing a power distribution network maximum power supply capacity calculation model; the power distribution network maximum power supply capacity calculation model comprises a maximum power supply capacity calculation model containing main transformer constraints and a maximum power supply capacity calculation model neglecting the main transformer constraints, and comprises the following steps: when the main transformer capacity is larger than or equal to the main transformer acting capacity in the main transformer capacity configuration, establishing a maximum power supply capacity calculation model neglecting the main transformer constraint; when the main transformer capacity is smaller than the main transformer acting capacity in the main transformer capacity configuration, determining a safety boundary expression and dividing a safety boundary type, if a feeder boundary exists in the safety boundary type, establishing a maximum power supply capacity calculation model neglecting main transformer constraint, otherwise, establishing a maximum power supply capacity calculation model containing the main transformer constraint; the security boundary type also includes a hybrid boundary and a main transformer boundary;

When the main transformer capacity is smaller than the main transformer acting capacity in the main transformer capacity configuration, determining a safety boundary expression and dividing the safety boundary types, wherein the method comprises the following steps of: dividing the safe boundary expression into a feeder critical equation and a main transformer critical equation according to the type of the medium-number right constant in the safe boundary expression; dividing the safety boundary type into a feeder boundary, a mixed boundary and a main transformer boundary according to a feeder critical equation and a main transformer critical equation;

And solving a calculation model of the maximum power supply capacity of the power distribution network to obtain the maximum power supply capacity of the power distribution network.

2. The method for calculating the maximum power supply capacity of the power distribution network according to claim 1, wherein the right constant of the equal sign in the feeder critical equation is feeder capacity, and the right constant of the equal sign in the main transformer critical equation is main transformer capacity.

3. The method of calculating maximum power capacity of a power distribution network according to claim 1, wherein the feeder boundary includes only a boundary of a feeder critical equation, the main transformer boundary includes only a boundary of a main transformer critical equation, and the hybrid boundary includes a boundary of the feeder critical equation and the main transformer critical equation.

4. A method for calculating maximum power supply capacity of a power distribution network according to any one of claims 1 to 3, wherein the step of establishing a maximum power supply capacity calculation model including main transformer constraints comprises the steps of:

and taking the maximum load of the power distribution network as an objective function, taking the feeder constraint of the feeder N-1 and the main transformer constraint checked by the main transformer N-1 as constraint conditions, and establishing a maximum power supply capacity calculation model containing the main transformer constraint.

5. A method of calculating maximum power supply capacity of a power distribution network according to any one of claims 1 to 3, wherein the step of establishing a maximum power supply capacity calculation model that ignores main transformer constraints comprises the steps of:

and removing the main transformer constraint in the maximum power supply capacity calculation model containing the main transformer constraint to obtain the maximum power supply capacity calculation model neglecting the main transformer constraint.

6. A power distribution network maximum power capability computing system, comprising:

the first calculation module is used for determining the main transformer acting capacity of the maximum power supply capacity of the power distribution network according to the network parameters of the power distribution network, and comprises the following steps: the main transformer action capacity is determined according to the maximum outgoing line number of the main transformer and the feeder line capacity of the main transformer with the maximum outgoing line number in the power distribution network, and is specifically as follows:

Wherein R _op represents the main transformer operating capacity, The maximum outgoing line number of the main transformer in the power distribution network is represented, and c represents the feeder line capacity of the main transformer with the maximum outgoing line number of the power distribution network;

The second calculation module is used for determining main transformer capacity configuration according to the main transformer acting capacity and the feeder line capacity, and comprises the following steps: determining the lower limit of the main transformer capacity as feeder capacity, and dividing the main transformer capacity configuration into a first main transformer capacity configuration, a second main transformer capacity configuration, a third main transformer capacity configuration and a fourth main transformer capacity configuration; the main transformer capacity in the first main transformer capacity configuration is larger than the main transformer acting capacity, the main transformer capacity in the second main transformer capacity configuration is equal to the main transformer acting capacity, the main transformer capacity in the third main transformer capacity configuration is between the feeder capacity and the main transformer acting capacity, and the main transformer capacity in the fourth main transformer capacity configuration is equal to the feeder capacity;

The third calculation module is used for dividing a safety boundary and establishing a calculation model of the maximum power supply capacity of the power distribution network according to the main transformer capacity and the main transformer acting capacity in the main transformer capacity configuration; the power distribution network maximum power supply capacity calculation model comprises a maximum power supply capacity calculation model containing main transformer constraints and a maximum power supply capacity calculation model neglecting the main transformer constraints, and comprises the following steps: when the main transformer capacity is larger than or equal to the main transformer acting capacity in the main transformer capacity configuration, establishing a maximum power supply capacity calculation model neglecting the main transformer constraint; when the main transformer capacity is smaller than the main transformer acting capacity in the main transformer capacity configuration, determining a safety boundary expression and dividing a safety boundary type, if a feeder boundary exists in the safety boundary type, establishing a maximum power supply capacity calculation model neglecting main transformer constraint, otherwise, establishing a maximum power supply capacity calculation model containing the main transformer constraint; the security boundary type also includes a hybrid boundary and a main transformer boundary;

When the main transformer capacity is smaller than the main transformer acting capacity in the main transformer capacity configuration, determining a safety boundary expression and dividing the safety boundary types, wherein the method comprises the following steps of: dividing the safe boundary expression into a feeder critical equation and a main transformer critical equation according to the type of the medium-number right constant in the safe boundary expression; dividing the safety boundary type into a feeder boundary, a mixed boundary and a main transformer boundary according to a feeder critical equation and a main transformer critical equation;

And the fourth calculation module is used for solving a calculation model of the maximum power supply capacity of the power distribution network to obtain the maximum power supply capacity of the power distribution network.