CN110165662B - Power transmission section conservative stability limit determination method based on optimization calculation - Google Patents

Abstract

The invention discloses a method for determining the conservative stability limit of a power transmission section based on optimization calculation, comprising: obtaining basic parameters of a power transmission section J; obtaining an expected fault set M of the power transmission section; /load power, and the power generation/load of each member line j in the transmission section and the transmitting and receiving ends of the transmission section meet the preset constraints, and the predicted open-circuit fault occurs in the line m in the predicted fault set M, which will cause the transmission power of the member line i to reach the higher level. When the critical value is limited, the minimum increase value of the total power of each member line of the transmission section J; select the line i corresponding to the line i corresponding to the expected open-circuit fault from the expected fault set M in turn, and repeat the previous step to The local stability conservative limit of the transmission section determined by the member line i is obtained. This method can quickly determine the conservative limit of the power grid transmission section, which is faster and more accurate.

Description

Determination method of conservative stability limit of transmission section based on optimization calculation

technical field

The invention belongs to the field of on-line security and stability calculation and analysis of power systems, in particular to a method for determining the conservative stability limit of a transmission section based on optimal calculation.

Background technique

In addition to ensuring the safety of equipment and power grids during normal operation, power grid regulation also needs to ensure the short-term power grid safety in the event of an expected accident in the power grid, that is, the static power grid security.

In power grid regulation, in addition to N-1 static safety analysis, grid static safety is more importantly achieved by monitoring the stable section of the power grid during normal operation.

At present, based on the dispatching experience, analysis software such as PSASP and BPA is used for offline analysis, and the power grid section and section power limit are determined according to extreme weather conditions and extreme power grid operation modes.

This method has defects such as low search efficiency, long search time and insufficient accuracy of section power limit.

SUMMARY OF THE INVENTION

The invention provides a method for determining the conservative stability limit of a power transmission section based on optimal calculation, so as to solve the problems of long search time and insufficient accuracy of the current power limit value of the power transmission section.

The invention provides a method for determining the conservative stability limit of a power transmission section based on optimal calculation, comprising:

Step S10: acquiring basic parameters of the power transmission section J, the basic parameters include: the rated current carrying capacity of each member line j of the power transmission section J, the base state power of each member line j, and the power generation/load information of the sending and receiving ends;

Step S20: obtaining an expected fault set M of the power transmission section, where the expected fault set M includes a plurality of lines that are expected to have open-circuit faults;

Step S30: Determine that by adjusting the power generation/load power of the sending and receiving ends of the power transmission section, the power generation/load of each member line j in the power transmission section and the sending and receiving ends of the power transmission section meet the preset constraints, and the lines in the expected fault set M The minimum increase in the total sum of the powers of the member lines of the transmission section J when the expected open-circuit fault will cause the transmission power of the member line i to reach the critical value of exceeding the limit,

The minimum increase value of the total power is the conservative and stable limit of the member line i when the line m is expected to open circuit fault, where i≠j≠m;

Step S40: Select the line m corresponding to the line i that is expected to have an open-circuit fault in sequence from the expected fault set M, and repeat step S30,

In order to obtain the local stability conservative limit Li of the power transmission section determined by the member line i, the local stability conservative limit Li is the minimum value among the stability conservative limits determined respectively by the member line i when multiple expected open-circuit faults occur. .

Further, the method, after step S40, further includes:

Selecting member lines in the power transmission section in turn, and repeating steps S30 to S40, to obtain the global stability conservative limit L of the power transmission section determined by each member line j;

The global stability conservative limit L is the minimum value among the local stability conservative limits determined by each member line j respectively.

Further, the method,

In the step S30, the adjustment of the power generation/load power at the sending and receiving ends of the power transmission section is as follows:

Determine the load rate of each member line j according to the rated current carrying capacity of each member line j of the power transmission section J and the base state power of each member line j;

When the transmission power of each member line j is changed by adjusting the generation/load power of the sending and receiving ends of the transmission section, the power of the member line with a heavier load rate is given priority to increase; or

Make the transmission power of member lines with light load rate increase more slowly.

Further, in the method, in the step S30, each member line j in the power transmission section satisfies a preset constraint condition, which is:

Each member line j in the transmission section satisfies the following thermal stability constraints:

The base state power of each member line j and the transmission power of member line j after the expected fault are less than its rated current carrying capacity:

Among them, P _j is the ground state power of member line j;

P _m is the ground-state power before the open-circuit fault occurs on the member line m;

为由线路j的额定载流量与当前的工作电压确定的极限有功功率；

is the limit active power determined by the rated current carrying capacity of line j and the current working voltage;

λ _mj is the distribution factor when the member line m transfers power to the member line j after the member line m has an open circuit fault.

Further, in the method, in the step S30, the power generation/load at the sending and receiving ends of the power transmission section satisfies a preset constraint condition, which is:

The output power of the generator is between the minimum allowable output and the maximum allowable output, and the received power of the load is between its maximum allowable load and the minimum allowable load; and

The power generation/load at the sending and receiving ends of the transmission section meets the constraints of power flow balance.

Further, the method,

In the step S30, it is determined that by adjusting the power generation/load power of the sending and receiving ends of the power transmission section, the power generation/load of each member line j in the power transmission section and the sending and receiving ends of the power transmission section satisfies the preset constraints, and the predicted fault is When the expected open-circuit fault of the line m in the set M will cause the transmission power of the member line i to reach the critical value of exceeding the limit, the minimum increase in the total sum of the power of each member line of the transmission section J is:

When the constraints are met, the following formula is the optimization objective function, and the linear programming optimization algorithm is used to determine the minimum increase in the total power of each member line of the transmission section J:

为在预想故障m发生且成员线路i的输送功率达到越限临界值时，输电断面内各成员线路j上不包括预想短路故障线路m转移来的功率的传输功率。in,

When the predicted fault m occurs and the transmission power of the member line i reaches the threshold value, the transmission power of each member line j in the transmission section does not include the power transferred from the predicted short-circuit fault line m.

Further, in the method, when the expected open-circuit fault occurs in line m, causing the transmission power of member line i to reach a critical value of exceeding the limit, the minimum increase in the total sum of the powers of each member line of said transmission section J is related to said transmission section. The adjustment method of the generation/load power of the sender and receiver is uniquely matched.

Further, in the method, in the step S10, the basic parameters of the acquired power transmission section J are:

Obtained from the power grid operation online monitoring device;

In the step S20, the acquisition of the expected fault set M of the power transmission section is:

Obtained from the power grid safety check device.

Further, the method,

The power generation at the sending and receiving ends of the power transmission section corresponding to the minimum increase in the total power of each member line of the power transmission section J when the expected open-circuit fault on the line m will cause the transmission power of the member line i to reach the threshold value exceeding the limit. / The adjustment method of load power is sent to the online control device for grid operation.

The invention provides a method for determining the conservative stability limit of a power transmission section based on optimal calculation. Firstly, the adjustment direction of the conservative limit of the transmission section is determined, and then the constraint conditions of the conservative stability limit of the transmission section are generated, and the conservative limit of the transmission section is determined through the optimization solution combined with the generated optimization objective of the optimization calculation of the conservative stability limit of the transmission section.

The method for determining the conservative stability limit of the power transmission section based on the optimization calculation provided by the invention can quickly determine the conservative limit of the power transmission section of the power grid, with faster speed and higher accuracy; short-term grid security.

Description of drawings

Exemplary embodiments of the present invention may be more fully understood by reference to the following drawings:

1 is a schematic flowchart of a method for determining the conservative stability limit of a power transmission section based on optimal calculation according to an embodiment of the present invention;

FIG. 2 is a schematic flowchart of a method for determining the conservative stability limit of a power transmission section based on optimization calculation according to another embodiment of the present invention.

Detailed ways

Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the embodiments described herein, which are provided for the purpose of this thorough and complete disclosure invention, and fully convey the scope of the invention to those skilled in the art. The terms used in the exemplary embodiments shown in the drawings are not intended to limit the invention. In the drawings, the same elements/elements are given the same reference numerals.

Unless otherwise defined, terms (including scientific and technical terms) used herein have the commonly understood meanings to those skilled in the art. In addition, it is to be understood that terms defined in commonly used dictionaries should be construed as having meanings consistent with the context in the related art, and should not be construed as idealized or overly formal meanings.

Usually, the transmission section or the stable section is a line collection composed of a group of lines with close electrical connection (the group of lines is electrically connected to the sending and receiving units or loads) according to the experience of dispatching operation; the total power of all lines in the line collection The addition is the section power of the stable section. The section power limit is to ensure that the section of other lines in the section can transmit power normally under short-term safety conditions when a line in the section fails.

Since the load rate of each member line in the transmission section (defined as the ratio of the active power transmitted by each member line to the limit active power) is different, when the power in the transmission section increases by adjusting the power generation and load at the sending and receiving ends of the transmission section, The power increase ratio of each member line of the transmission section may be different, so the stability limit of the transmission section may be different under different power increase modes.

When the power grid is dispatched and operated, the priority is to ensure the security of the power grid. For this reason, it is necessary to calculate the more conservative transmission section stability limit, that is, the most conservative section power limit in different power growth modes.

As shown in FIG. 1 , a method for determining the conservative stability limit of a power transmission section based on optimization calculation according to an embodiment of the present invention includes the following steps:

Step S10: acquiring basic parameters of the power transmission section J, the basic parameters include: the rated current carrying capacity of each member line j of the power transmission section J, the base state power of each member line j, and the power generation/load information of the sending and receiving ends;

Step S20: obtaining an expected fault set M of the power transmission section, where the expected fault set M includes a plurality of lines that are expected to have open-circuit faults;

Step S30: Determine that by adjusting the power generation/load power of the sending and receiving ends of the power transmission section, the power generation/load of each member line j in the power transmission section and the sending and receiving ends of the power transmission section meet the preset constraints, and the lines in the expected fault set M The minimum increase in the total sum of the powers of the member lines of the transmission section J when the expected open-circuit fault will cause the transmission power of the member line i to reach the critical value of exceeding the limit,

The minimum increase value of the total power is the stable and conservative limit of the member line i when the expected open circuit fault occurs on the line m, where i≠j≠m;

Step S40: Select the line m corresponding to the line i that is expected to have an open-circuit fault in sequence from the expected fault set M, and repeat step S30,

In order to obtain the local stability conservative limit Li of the power transmission section determined by the member line i, the local stability conservative limit Li is the minimum value among the stability conservative limits determined respectively by the member line i when multiple expected open-circuit faults occur. .

It should be understood that the over-limit critical value here is the limit active power (in MW) of the member line, which is determined by the rated current carrying capacity (in kA) of the line and the voltage level of the line.

So far, the lowest stability limit of each expected fault of each member line is the key member line and the key expected fault.

It should be understood that the base state power of each member line j is used to determine the load factor.

The above describes the method of sequentially determining the minimum increase in the total power of each member line of the transmission section J corresponding to multiple faults of a single line, thereby obtaining the local stability conservative limit Li.

It should be understood that it is also possible to sequentially determine the minimum increase in the total power of each member line of the transmission section J corresponding to the multiple faults of a single line, and adjust it to sequentially determine the multiple associated lines of the single predicted fault line respectively corresponding to the line. The minimum increase value of the total sum of the power of each member line of the transmission section J.

The above only changes the loop variables in the traversal process, but does not change the number of loops; both have the same technical complexity and the same technical effect.

Further, the method, after step S40, further includes:

Selecting member lines in the power transmission section in turn, and repeating steps S30 to S40, to obtain the global stability conservative limit L of the power transmission section determined by each member line j;

The global stability conservative limit L is the minimum value among the local stability conservative limits determined by each member line j respectively.

Further, the method,

In the step S30, the adjustment of the power generation/load power at the sending and receiving ends of the power transmission section is as follows:

Determine the load rate of each member line j according to the rated current carrying capacity of each member line j of the power transmission section J and the base state power of each member line j;

When the transmission power of each member line j is changed by adjusting the generation/load power of the sending and receiving ends of the transmission section, the power of the member line with a heavier load rate is given priority to increase; or

Make the transmission power of member lines with light load rate increase more slowly.

Using the above power distribution strategy between lines within a transmission section, it can be realized that when the power of the transmission section increases, each member line is prone to exceed the limit in the base state and after the expected failure, thereby ensuring that the stability limit of the transmission section is small, which is conducive to optimization. The process converges quickly, increasing the speed of the search.

Further, in the method, in the step S30, each member line j in the power transmission section satisfies a preset constraint condition, which is:

Each member line j in the transmission section satisfies the following thermal stability constraints:

The base state power of each member line j and the transmission power of member line j after the expected fault are less than its rated current carrying capacity:

Among them, P _j is the ground state power of member line j;

P _m is the ground-state power before the open-circuit fault occurs on the member line m;

为由线路j的额定载流量与当前的工作电压确定的极限有功功率；

is the limit active power determined by the rated current carrying capacity of line j and the current working voltage;

λ _mj is the distribution factor when the member line m transfers power to the member line j after the member line m has an open circuit fault. Further, in the method, in the step S30, the power generation/load at the sending and receiving ends of the power transmission section satisfies a preset constraint condition, which is:

The output power of the generator is between the minimum allowable output and the maximum allowable output, and the received power of the load is between its maximum allowable load and the minimum allowable load; and

The power generation/load at the sending and receiving ends of the transmission section meets the constraints of power flow balance.

Further, the method,

In the step S30, it is determined that by adjusting the power generation/load power of the sending and receiving ends of the power transmission section, the power generation/load of each member line j in the power transmission section and the sending and receiving ends of the power transmission section satisfies the preset constraints, and the predicted fault is When the expected open-circuit fault of the line m in the set M will cause the transmission power of the member line i to reach the critical value of exceeding the limit, the minimum increase in the total sum of the power of each member line of the transmission section J is:

When the constraints are met, the following formula is the optimization objective function, and the linear programming optimization algorithm is used to determine the minimum increase in the total power of each member line of the transmission section J:

为在预想故障m发生且成员线路i的输送功率达到越限临界值时，输电断面内各成员线路j上不包括预想短路故障线路m转移来的功率的传输功率。in,

When the predicted fault m occurs and the transmission power of the member line i reaches the threshold value, the transmission power of each member line j in the transmission section does not include the power transferred from the predicted short-circuit fault line m.

For the above multi-variable and multi-constrained optimization problems, the use of linear programming can ensure that the global optimal value can be obtained, and the search efficiency can be guaranteed.

Further, in the method, when the expected open-circuit fault occurs in line m, causing the transmission power of member line i to reach a critical value of exceeding the limit, the minimum increase in the total sum of the powers of each member line of said transmission section J is related to said transmission section. The adjustment method of the generation/load power of the sender and receiver is uniquely matched.

Further, in the method, in the step S10, the basic parameters of the acquired power transmission section J are:

Obtained from the power grid operation online monitoring device;

In the step S20, the acquisition of the expected fault set M of the power transmission section is:

Obtained from the power grid safety check device.

Further, the method,

The power generation at the sending and receiving ends of the power transmission section corresponding to the minimum increase in the total power of each member line of the power transmission section J when the expected open-circuit fault on the line m will cause the transmission power of the member line i to reach the threshold value exceeding the limit. / The adjustment method of load power is sent to the online control device for grid operation.

After receiving the adjustment method of the power generation/load power at the sending and receiving ends of the power transmission section, the power grid operation online control device performs grid scheduling and operation according to the adjustment amount of the power generation load power of the sending and receiving ends under the conservative and stable limit of the power transmission section, It is beneficial to improve the stability of the power grid.

It should be understood that the power grid operation online monitoring device, power grid safety check device, and power grid operation online control device here all adopt technical solutions known to those skilled in the art, such as real-time measurement of the basic parameters of the power transmission section, such as determining the power transmission section and The expected fault collection of the transmission section, and the adjustment of the power generation/load power at the sending and receiving ends of the transmission section in the power grid, etc.

To sum up, the method for determining the conservative stability limit of transmission section based on the optimization calculation first determines the adjustment direction of the conservative limit of the transmission section, then puts forward the constraints of the conservative limit of the transmission section, and then determines the optimization objective of the optimal calculation of the conservative limit of the transmission section. Finally, the conservative limit of the transmission section is obtained through the optimization solution.

This method can quickly determine the conservative limit of the power grid transmission section, with faster speed and higher accuracy; the conservative limit is used to ensure the short-term power grid safety in the event of an expected accident in the power grid, provide decision support for the formulation of power grid dispatching measures, and provide power The operation of the market provides reliable technical support.

As shown in FIG. 2 , the method for quickly determining the conservative limit of a power transmission section based on optimization calculation according to another embodiment includes the following steps:

1) Determine the adjustment direction of the conservative limit of the transmission section;

2) For each member line in the transmission section, for each expected fault, calculate one by one the stable limit when a member line reaches the limit under a certain expected fault, as the conservative limit of the transmission section with the expected fault of the member line as a reference;

3) Determine the constraints of the conservative limit of the transmission section with an expected fault of a member line as a reference;

4) Determine the optimization objective of the optimal calculation of the conservative limit of the transmission section with an expected fault of a member line as a reference;

5) Obtain the conservative limit of the transmission section with an expected fault of a member line as a reference;

6) Comprehensively determine conservative limits for the entire transmission section.

It should be noted that the optimization is for an expected fault of a member line. For each expected fault of each member line, to determine whether other member lines exceed the limit, an optimization solution needs to be carried out; therefore, for N The section formed by the member lines needs to be optimized for N*(N-1) times.

The combined adjustment method of unit output and load is selected, so that the power on the member line is the critical value when the expected fault occurs, and other non-faulty lines on the transmission section do not exceed the limit. At this time, the transmission of each member line on the transmission section is The total power is the conservative limit value corresponding to the expected fault of the line.

Preferably, the conservative limit of the entire power transmission section takes the minimum value among the conservative limits of the above lines. It should be understood that other statistical characteristics such as median can also be selected.

Usually, any transmission section J in the power grid is composed of multiple member lines; when formulating grid dispatching measures, it is necessary to ensure that all member lines of the transmission section J do not exceed the limit in the base state and after the expected fault occurs, that is, short Time grid security, that is, grid static security.

The expected fault set M of the transmission section J usually contains the expected faults and other related faults that may occur on all member lines on the transmission section.

It should be understood that each expected fault mode for each member line in the expected fault set M is an independent fault, and each expected fault mode is independent of each other; the expected fault set M does not include associated faults.

Due to the different load rates of each member line of the transmission section, when the output power of the generator sets at the sending and receiving ends of the transmission section and/or the received power of the load are adjusted to increase the transmittable power on the transmission section, the proportion of the power increase of each member line of the transmission section may increase. Therefore, under different power growth modes, the stability limit of the transmission section will be different.

Therefore, the adjustment direction of determining the conservative stability limit of the transmission section in the step 1) includes:

The conservative and stable limit of the transmission section should be adjusted as follows: try to make the power of the member lines of the transmission section with heavier load rate increase preferentially, and try to make the power of the member lines of the transmission section with light load rate increase slowly.

In this way, when the power of the transmission section increases, the member lines of the transmission section are prone to exceed the limit in the base state and after the expected failure, and the determined stability limit of the transmission section is small, which conforms to the conservative principle of the power grid.

Wherein, in the step 2), for each member line of the power transmission section, for each expected fault, calculate one by one the stability limit when the load of a member line reaches the limit value under a certain expected fault, as the expected fault of the line. is the conservative stability limit of the reference transmission section, specifically:

For each member line i of transmission section J, calculate the transmission section limit X _im when line i reaches the limit after each of its expected faults m.

That is, a conservative stability limit is determined for each expected fault of the member line i one by one.

Wherein, the step 3) determines the constraint condition of the conservative stability limit of the transmission section with a certain expected fault of a certain member line as a reference, specifically:

The constraints of the conservative stability limit of the transmission section with the predicted fault m of the member line i as the reference, including the thermal stability constraints of the member line i of the transmission section, the constraints of power generation and load adjustment at the sending and receiving ends of the transmission section, and the power flow balance constraints of power generation and load adjustment.

1) Thermal stability constraints of member line i of transmission section J

It is defined as the initial power of all member lines of the transmission section (that is, the power in the base state) and the power after the expected fault meet the rated current carrying capacity constraints of the line, that is, the power flow of each line exceeds the limit after the expected fault occurs on other lines.

Given below are the thermal stability constraints for any member line i when a fault m is expected:

In the above formula, Pi is the initial power of line _i ;

P _i +P _m λ _mi is the transmission power of line i after the expected fault m (such as an open-circuit fault of line m) occurs;

P _i ^max is the limit active power of line i;

_λmi is the distribution factor of the power transfer from line m to line i after the expected fault m occurs (for example, line m is open circuit), its value is predetermined according to the grid topology and the basic electrical parameters of the line, and is kept fixed during the grid adjustment process. Change.

When determining the conservative stability limit of the transmission section, all member lines j in the transmission section (including the predicted fault line and the currently investigated line i) also need to satisfy similar thermal stability constraints when the predicted fault m is present.

2) Adjust the power constraints of the equipment, that is, the constraints of power generation and load adjustment at the sending and receiving ends of the transmission section

The power adjustment of the generator set and load at the sending and receiving end of the transmission section is constrained. Specifically, the output of the generator set should be between the minimum allowable output and the maximum allowable output, and the received power of the load should be within the allowable range of the load.

Given that the number and location of generators and loads at the sending and receiving ends of a transmission section are fixed, the power constraints of the adjustment equipment are the same for any combination of member lines and expected faults in the transmission section.

3) The power flow balance constraint, that is, the power flow balance constraint of power generation load adjustment

When adjusting the power of the generator set and the load at the sending and receiving ends of the transmission section, the power flow balance constraint should be satisfied, that is, the increased power of the power generation and the received power of the load should be matched.

Wherein, the step 4) determines the optimization objective of the conservative stability limit optimization calculation of the transmission section with a certain expected fault of a certain member line as a reference, including:

The optimization objective of the optimization calculation of the conservative stability limit of the transmission section with the predicted fault m of the member line i as the reference is that when the current carrying capacity of the member line i reaches the limit value when the predicted fault m is, all the member lines of the transmission section before the fault are in the predicted fault. The minimization of the total sum of power before the occurrence of m is the optimization goal.

为在预想故障m发生且成员线路i的输送功率达到越限临界值时，输电断面内各成员线路j上不包括预想短路故障线路m转移来的功率的传输功率。in,

When the predicted fault m occurs and the transmission power of the member line i reaches the threshold value, the transmission power of each member line j in the transmission section does not include the power transferred from the predicted short-circuit fault line m.

That is, it is the total sum of the powers of all the member lines of the transmission section before the predicted fault m occurs.

At this time, the constraint of "it is expected that the occurrence of fault m will cause line i to exceed the limit, and other lines will not exceed the limit" is satisfied.

That is, in the currently determined power increase method (corresponding to the corresponding transmission section sending and receiving end generator sets, load power adjustment method; this adjustment method redistributes active power among each member line, so that each member line has a corresponding and this adjustment method makes the total power of the section increase), and the expected fault m occurs, it will cause the line i to receive the active power transferred from the expected short-circuit fault line m; at this time, the member line i Under the combined action of the current redistributed power and the active power transferred from the predicted short-circuit fault line m, the threshold value of over-limit is reached; at this time, the other member lines are under their respective current redistributed power and from the predicted short-circuit fault line. Under the combined action of the active power transferred from m, no overrun occurs (that is, the thermal equilibrium theorem is satisfied).

Wherein, the step 5) obtains the conservative stability limit of the transmission section with a certain expected fault of a certain member line as a reference, including:

Obtain the conservative stability limit of the transmission section with the predicted fault m of the member line i as the reference, and obtain the optimal solution through the optimization calculation. The results include:

1) The adjustment amount of the power generation load at the sending and receiving ends of the transmission section is used as a reference for the dispatching and operation personnel of the power supply grid, and as a reference for the dispatching operation of the power grid and the operation of the power market.

2) Corresponding to the adjustment amount of the power generation load at the sending and receiving ends of the transmission section, the sum of the powers of all member lines of the transmission section is the conservative stability limit of the transmission section.

Wherein, the step 6) comprehensively determines the conservative stability limit of the transmission section, including:

The minimum value of the conservative stability limit of the transmission section with each expected fault of each member line as a reference is taken as the conservative stability limit of the transmission section.

So far, the worst-case stability limit on the transmission section has been found. According to the adjustment method and the stability limit, the grid operation can be guided, and the security level of the grid operation can be improved.

Taking the operation data of the North China-Central China power grid during a certain day's peak load period as an example, the conservative stability limit of the transmission section based on the optimization calculation is calculated by taking the Yuja section as an example. As shown in Table 1, the Chongqing jaw section consists of 4 lines. When calculating the conservative stability limit of the Yu jaw section, the expected fault set to be considered is shown in Table 2. Using the method for quickly determining the conservative stability limit of transmission section based on optimization calculation in this embodiment, the stability limit of transmission section with different member lines and different expected faults as reference is shown in Table 3.

Table 1. The composition table of the jaw section

serial number line name Line power (MW) 1 Central China. Panlong I Line 239 2 Central China. Panlong II line 221 3 Central China. Zhang En Ⅰ loop 105 4 Central China. Zhang En Ⅱ loop 105

Table 2 Fault set of Yu jaw section

serial number line name 1 Central China. Zhang En Ⅰ loop 2 Central China. Zhang En Ⅱ loop 3 Central China. Panlong I Line 4 Central China. Panlong II line

Table 3 Stability limit of Yu jaw section under different references

serial number Anticipate failure Reference member line name Stability limit (MW) 1. Central China. Panlong II line Central China. Panlong I Line 2453 2. Central China. Zhang En Ⅰ loop Central China. Panlong I Line 4930 3. Central China. Zhang En Ⅱ loop Central China. Panlong I Line 4930 4. Central China. Panlong I Line Central China. Panlong II line 2596 5. Central China. Zhang En Ⅰ loop Central China. Panlong II line 5823 6. Central China. Zhang En Ⅱ loop Central China. Panlong II line 5823 7. Central China. Panlong I Line Central China. Zhang En Ⅰ loop 7299 8. Central China. Panlong II line Central China. Zhang En Ⅰ loop 7423 9. Central China. Zhang En Ⅱ loop Central China. Zhang En Ⅰ loop 3994 10. Central China. Panlong I Line Central China. Zhang En Ⅱ loop 7300 11. Central China. Panlong II line Central China. Zhang En Ⅱ loop 7424 12. Central China. Zhang En Ⅰ loop Central China. Zhang En Ⅱ loop 3994

In view of the failure of line A, it is only necessary to judge the critical value when other lines exceed the limit; therefore, according to Table 1 and Table 2, the stability limit of the combination of the 12 member lines in Table 3 and the expected fault can be determined.

The minimum value of each line and the expected fault combination is 2453MW, that is, the conservative stability limit of the Yu jaw section is 2453MW. According to the conservative stability limit, the power grid dispatching measures are formulated. In the transmission section, the Huazhong. Panlong I line will exceed the limit when the Huazhong. Panlong II line fails.

The present invention has been described above with reference to a few embodiments. However, as is known to those skilled in the art, other embodiments than the above disclosed invention are equally within the scope of the invention, as defined by the appended patent claims.

Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/the/the [means, component, etc.]" are open to interpretation as at least one instance of said means, component, etc., unless expressly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

Claims (8)

1. a method for determining the conservative stability limit of a power transmission section based on optimal calculation, is characterized in that, comprising: Step S10: acquiring basic parameters of the power transmission section J, the basic parameters include: the rated current carrying capacity of each member line j of the power transmission section J, the base state power of each member line j, and the power generation/load information of the sending and receiving ends; Step S20: obtaining an expected fault set M of the power transmission section, where the expected fault set M includes a plurality of lines that are expected to have open-circuit faults; Step S30: Determine that by adjusting the power generation/load power of the sending and receiving ends of the power transmission section, the power generation/load of each member line j in the power transmission section and the sending and receiving ends of the power transmission section meet the preset constraints, and the lines in the expected fault set M When the expected open-circuit fault occurs, the transmission power of member line i will reach the critical value of exceeding the limit, the minimum increase value of the total sum of the power of each member line of said transmission section J, The minimum increase value of the total power is the conservative and stable limit of the member line i when the expected open circuit fault occurs on the line m, where i≠j≠m; When the constraints are met, the following formula is the optimization objective function, and the linear programming optimization algorithm is used to determine the minimum increase in the total power of each member line of the transmission section J:

in,

is the transmission power that does not include the power transferred from the predicted open-circuit fault line m on each member line j in the transmission section when the predicted fault m occurs and the transmission power of the member line i reaches the critical value; Step S40: Select the line m corresponding to the line i that is expected to have an open-circuit fault in sequence from the expected fault set M, and repeat step S30, In order to obtain the local conservative stability limit Li of the transmission section determined by the member line i, the local conservative stability limit Li is the minimum value of the conservative stability limits determined respectively by the member line i when multiple expected open-circuit faults occur. . 2. The method for determining the conservative stability limit of a power transmission section based on optimal calculation according to claim 1, wherein, After step S40, it also includes: Selecting member lines in the power transmission section in turn, and repeating steps S30 to S40, to obtain the global conservative stability limit L of the power transmission section determined by each member line j; The global conservative stability limit L is the minimum value among the local conservative stability limits determined by each member line j respectively. 3. The method for determining the conservative stability limit of power transmission section based on optimal calculation according to claim 2, wherein, In the step S30, the adjustment of the power generation/load power at the sending and receiving ends of the power transmission section is as follows: Determine the load rate of each member line j according to the rated current carrying capacity of each member line j of the power transmission section J and the base state power of each member line j; When the transmission power of each member line j is changed by adjusting the generation/load power of the sending and receiving ends of the transmission section, the power of the member line with a heavier load rate is given priority to increase; or Make the transmission power of member lines with light load rate increase more slowly. 4. The method for determining the conservative stability limit of a power transmission section based on optimal calculation according to claim 2, wherein, In the step S30, each member line j in the power transmission section satisfies a preset constraint condition, which is: Each member line j in the transmission section satisfies the following thermal stability constraints: The base state power of each member line j and the transmission power of member line j after the expected fault are less than its rated current carrying capacity:

Among them, P _j is the ground state power of member line j; P _m is the ground-state power before the open-circuit fault occurs on the member line m; P _j ^max is the limit active power determined by the rated current carrying capacity of line j and the current working voltage; λ _mj is the distribution factor when the member line m transfers power to the member line j after the member line m has an open circuit fault. 5. The method for determining the conservative stability limit of power transmission section based on optimization calculation according to claim 2, wherein, In the step S30, the power generation/load at the sending and receiving ends of the power transmission section satisfies a preset constraint condition, which is: The output power of the generator is between the minimum allowable output and the maximum allowable output, and the received power of the load is between its maximum allowable load and the minimum allowable load; and The power generation/load at the sending and receiving ends of the transmission section meets the constraints of power flow balance. 6. The method for determining the conservative stability limit of power transmission section based on optimization calculation according to claim 2, wherein, When the expected open-circuit fault of line m causes the transmission power of member line i to reach the critical value of exceeding the limit, the minimum increase in the total power of each member line of said transmission section J and the adjustment of the power generation/load power at the sending and receiving ends of said transmission section methods uniquely correspond. 7. The method for determining the conservative stability limit of power transmission section based on optimization calculation according to claim 2, wherein, In the step S10, the basic parameters of the acquired power transmission section J are: Obtained from the power grid operation online monitoring device; In the step S20, the acquisition of the expected fault set M of the power transmission section is: Obtained from the power grid safety check device. 8. The method for determining the conservative stability limit of power transmission section based on optimization calculation according to claim 6, wherein, The power generation at the sending and receiving ends of the transmission section corresponding to the minimum increase in the total sum of the powers of the member lines of the transmission section J when the expected open-circuit fault of the line m will cause the transmission power of the member line i to reach the threshold value exceeding the limit. / The adjustment method of load power is sent to the online control device for grid operation.

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