CN110165662B - Power transmission section conservative stability limit determination method based on optimization calculation - Google Patents
Power transmission section conservative stability limit determination method based on optimization calculation Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
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- H—ELECTRICITY
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- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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Abstract
The invention discloses a method for determining a conservative stability limit of a power transmission section based on optimization calculation, which comprises the following steps: acquiring basic parameters of a power transmission section J; acquiring an expected fault set M of the power transmission section; determining a minimum added value of the total power of each member line of the power transmission section J when the transmission power of the member line i reaches an out-of-limit critical value due to the occurrence of an expected open-circuit fault on a line M in an expected fault set M by adjusting the power generation/load power of the transmission and reception end of the power transmission section and the power generation/load of each member line J and the transmission and reception end of the power transmission section in the power transmission section meet preset constraint conditions; and sequentially selecting the lines which are expected to generate open circuit faults and correspond to the lines i from the expected fault set M, and repeating the previous step to obtain local stable conservative limits of the power transmission section determined by the member lines i. The method can quickly determine the conservative limit of the power transmission section of the power grid, and is high in speed and accuracy.
Description
Technical Field
The invention belongs to the field of on-line safety and stability calculation and analysis of power systems, and particularly relates to a method for determining a conservative stability limit of a power transmission section based on optimization calculation.
Background
The power grid regulation and control not only ensures the safety of equipment and a power grid in normal operation, but also needs to ensure the short-time power grid safety when the power grid is subjected to expected accident conditions, namely the static safety of the power grid.
In the regulation and control of the power grid, the static safety of the power grid is realized by monitoring a stable section when the power grid normally runs, in addition to the N-1 static safety analysis.
At present, according to a scheduling experience, analysis software such as PSASP and BPA is adopted for off-line analysis, and the power grid section and the power limit value of the section are determined according to extreme meteorological conditions and an extreme power grid operation mode.
The method has the defects of low search efficiency, long search time, insufficient accuracy of the section power limit value and the like.
Disclosure of Invention
The invention provides a method for determining a conservative stability limit of a power transmission section based on optimization calculation, which aims to solve the problems of long search time, insufficient accuracy and the like of the power limit value of the current power transmission section.
The invention provides a method for determining a conservative stability limit of a power transmission section based on optimization calculation, which comprises the following steps:
step S10: obtaining basic parameters of a power transmission section J, wherein the basic parameters comprise: rated current carrying capacity of each member line J of the power transmission section J, ground state power of each member line J, and power generation/load information of a transmitting end and a receiving end;
step S20: acquiring an expected fault set M of the power transmission section, wherein the expected fault set M comprises a plurality of lines expected to generate open circuit faults;
step S30: determining a minimum increase value of the total power of each member line of the power transmission section J when the transmission power of the member line i reaches an out-of-limit critical value due to the occurrence of an expected open-circuit fault on a line M in the expected fault set M by adjusting the power generation/load power of the transmission section transmission and reception end and the power generation/load of each member line J and the transmission section transmission and reception end in the power transmission section meet preset constraint conditions,
the minimum added value of the total power is a stable conservative limit of the member line i when an expected open circuit fault occurs in the line m, wherein i is not equal to j is not equal to m;
step S40: sequentially selecting a line M expected to have an open-circuit fault corresponding to the line i from the expected fault set M, and repeating the step S30,
and obtaining a local stable conservative limit Li of the power transmission section determined by the member line i, wherein the local stable conservative limit Li is the minimum value of stable conservative limits respectively determined by the member line i when a plurality of expected open circuit faults occur.
Further, after step S40, the method further includes:
sequentially selecting member lines in the power transmission section, and repeating the steps from S30 to S40 to obtain a global stability conservative limit L of the power transmission section determined by each member line j;
the global stability conservative limit L is a minimum value among local stability conservative limits respectively determined by each member line j.
Further, the method comprises the following steps of,
in step S30, the adjusting of the power generation/load power of the transmission/reception end of the transmission section includes:
determining 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 ground state power of each member line J;
when the power generation/load power of the transmitting and receiving end of the power transmission section is adjusted to change the transmission power of each member line j, preferentially increasing the power of the member line with the heavier load rate; or
The transmission power of the member line with lighter load rate is increased more slowly.
Further, in the method, in step S30, the method for determining whether each member line j in the power transmission section satisfies a predetermined constraint condition includes:
each member line j in the power transmission section satisfies the following thermal stability constraint:
the ground state power of each member line j and the transmission power of the member line j after the expected fault occurs are both smaller than the rated current-carrying capacity:
wherein, PjThe ground state power of the member line j;
Pmthe ground state power of the member line m before the open circuit fault occurs;
λm-jand after the member line m has an open circuit fault, the member line m transfers the distribution factor of the power to the member line j.
Further, in the method, in step S30, the power generation/load of the power transmission section transmission/reception end satisfies a predetermined constraint condition, and the method includes:
the output power of the power generation is between the minimum allowable output and the maximum allowable output, and the received power of the load is between the maximum allowable load and the minimum allowable load; and
the power generation/load of the transmission and receiving ends of the transmission section meets the tidal current balance constraint.
Further, the method comprises the following steps of,
in step S30, the determining step includes that, when the power generation/load of each member line J and the power transmission cross-section transmitting/receiving end in the power transmission cross-section satisfies a predetermined constraint condition by adjusting the power generation/load of the power transmission cross-section transmitting/receiving end, and the transmission power of the member line i reaches an out-of-limit threshold value due to an expected open-circuit fault occurring in the line M in the expected fault set M, the minimum increase value of the total power of each member line in the power transmission cross-section J is:
when the constraint condition is met, the following formula is an optimization objective function, and the minimum added value of the total power of each member line of the power transmission section J is determined by adopting an optimization algorithm of linear programming:
wherein，
When the expected failure m occurs and the transmission power of the member line i reaches the threshold value, the transmission power of the power transferred by the expected short-circuit failure line m is not included in each member line j in the transmission section.
Further, in the method, when the transmission power of the member line i reaches the out-of-limit threshold value due to the occurrence of the expected open circuit fault on the line m, the minimum increase value of the total power sum of the member lines of the power transmission section J uniquely corresponds to the method for adjusting the power generation/load power of the power transmission section transmitting/receiving end.
Further, in the method, in step S10, the obtaining of the basic parameters of the power transmission section J includes:
obtaining the operation of the power grid from an online monitoring device;
in step S20, the acquiring the set M of the expected faults of the power transmission cross section is:
and obtaining the data from the power grid security check device.
Further, the method comprises the following steps of,
and sending the adjusting method of the power generation/load power of the transmitting and receiving end of the power transmission section corresponding to the minimum added value of the total power of all the member lines of the power transmission section J to a power grid operation online regulating and controlling device when the expected open circuit fault of the line m causes the transmission power of the member line i to reach an out-of-limit critical value.
The invention provides a method for determining a conservative stability limit of a power transmission section based on optimization calculation. Firstly, determining the adjustment direction of the conservative limit of the power transmission section, then generating a constraint condition of the conservative stable limit of the power transmission section, and determining the conservative limit of the power transmission section through optimization solution by combining an optimization target of the generated optimal calculation of the conservative stable limit of the power transmission section.
The method for determining the conservative stability limit of the power transmission section based on the optimization calculation can quickly determine the conservative limit of the power transmission section of the power grid, and is higher in speed and accuracy; the conservative limit with high accuracy can fully guarantee the short-time power grid safety when the power grid is in an expected accident situation.
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A more complete understanding of exemplary embodiments of the present invention may be had by reference to the following drawings in which:
fig. 1 is a schematic flow chart of a power transmission section conservative stability limit determination method based on optimization calculation according to an embodiment of the present invention;
fig. 2 is a schematic flow chart of a power transmission section conservative stability limit determination method based on optimization calculation according to another embodiment of the present invention.
Detailed Description
The 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 complete and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, the same units/elements are denoted by the same reference numerals.
Unless otherwise defined, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Further, it will be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense.
Generally, a transmission section or a stable section is a line set consisting of a group of lines (the group of lines is electrically connected with a transmitting and receiving terminal set or a load) which are in close electrical connection according to the scheduling operation experience; the sum of the powers of all the lines in the line set is the section power of the stable section. The section power limit value is to ensure that the section can normally transmit power under the short-time safety condition of other lines in the section when a line in the section has a fault.
Because the load rates (defined as the ratio of the active power transmitted by each member line to the limit active power) of each member line in the power transmission section are different, when the power in the power transmission section is increased by adjusting the power generation and the load of the transmitting and receiving ends of the power transmission section, the power increase ratios of each member line in the power transmission section may be different, so that the stability limits of the power transmission section may be different in different power increase modes.
When the power grid is scheduled and operated, the power grid safety needs to be guaranteed preferentially, and therefore a more conservative power transmission section stability limit, namely the most conservative section power limit value in different power increasing modes, needs to be calculated.
As shown in fig. 1, a method for determining a 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: obtaining basic parameters of a power transmission section J, wherein the basic parameters comprise: rated current carrying capacity of each member line J of the power transmission section J, ground state power of each member line J, and power generation/load information of a transmitting end and a receiving end;
step S20: acquiring an expected fault set M of the power transmission section, wherein the expected fault set M comprises a plurality of lines expected to generate open circuit faults;
step S30: determining a minimum increase value of the total power of each member line of the power transmission section J when the transmission power of the member line i reaches an out-of-limit critical value due to the occurrence of an expected open-circuit fault on a line M in the expected fault set M by adjusting the power generation/load power of the transmission section transmission and reception end and the power generation/load of each member line J and the transmission section transmission and reception end in the power transmission section meet preset constraint conditions,
the minimum added value of the total power is a stable conservative limit of the member line i when an expected open circuit fault occurs in a line m, wherein i is not equal to j is not equal to m;
step S40: sequentially selecting a line M expected to have an open-circuit fault corresponding to the line i from the expected fault set M, and repeating the step S30,
and obtaining a local stable conservative limit Li of the power transmission section determined by the member line i, wherein the local stable conservative limit Li is the minimum value of stable conservative limits respectively determined by the member line i when a plurality of expected open circuit faults occur.
It should be understood that the out-of-limit threshold is the limit active power (in MW) of the member line, and is determined by the rated ampacity (in kA) of the line and the voltage class at which the line is located.
So far, the lowest stability limit of each predicted fault of each member line is the key member line and the key predicted fault.
It should be understood that the ground state power of each member line j is used to determine the duty cycle.
The above describes a method for sequentially determining the minimum added value of the total power of each member line of the power transmission section J corresponding to each of a plurality of faults of a single line, so as to obtain the local stable conservative limit Li.
It should be understood that the minimum increase value of the total power sum of the member lines of the power transmission section J corresponding to a plurality of associated lines of a single expected fault line may also be adjusted from the minimum increase value of the total power sum of the member lines of the power transmission section J corresponding to a plurality of faults of a single line being determined in sequence.
The above only changes the loop variables in the traversal process, and does not change the loop times; both have the same technical complexity and the same technical effect.
Further, after step S40, the method further includes:
sequentially selecting member lines in the power transmission section, and repeating the steps from S30 to S40 to obtain a global stability conservative limit L of the power transmission section determined by each member line j;
the global stability conservative limit L is a minimum value among local stability conservative limits respectively determined by each member line j.
Further, the method comprises the following steps of,
in step S30, the adjusting of the power generation/load power of the transmission/reception end of the transmission section includes:
determining 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 ground state power of each member line J;
when the power generation/load power of the transmitting and receiving end of the power transmission section is adjusted to change the transmission power of each member line j, preferentially increasing the power of the member line with the heavier load rate; or
The transmission power of the member line with lighter load rate is increased more slowly.
By adopting the power distribution strategy among the lines in the power transmission section, the situation that each member line is easy to exceed the limit after the ground state and the expected fault when the power of the power transmission section is increased can be realized, so that the stability limit of the power transmission section is ensured to be smaller, the optimization process can be rapidly converged, and the searching speed can be improved.
Further, in the method, in step S30, the method for determining whether each member line j in the power transmission section satisfies a predetermined constraint condition includes:
each member line j in the power transmission section satisfies the following thermal stability constraint:
the ground state power of each member line j and the transmission power of the member line j after the expected fault occurs are both smaller than the rated current-carrying capacity:
wherein, PjThe ground state power of the member line j;
Pmthe ground state power of the member line m before the open circuit fault occurs;
λm-jand after the member line m has an open circuit fault, the member line m transfers the distribution factor of the power to the member line j. Further, in the method, in the step S30, the power generation/load of the power transmission section transmitting/receiving end satisfies the requirementThe preset constraint conditions are as follows:
the output power of the power generation is between the minimum allowable output and the maximum allowable output, and the received power of the load is between the maximum allowable load and the minimum allowable load; and
the power generation/load of the transmission and receiving ends of the transmission section meets the tidal current balance constraint.
Further, the method comprises the following steps of,
in step S30, the determining step includes that, when the power generation/load of each member line J and the power transmission cross-section transmitting/receiving end in the power transmission cross-section satisfies a predetermined constraint condition by adjusting the power generation/load of the power transmission cross-section transmitting/receiving end, and the transmission power of the member line i reaches an out-of-limit threshold value due to an expected open-circuit fault occurring in the line M in the expected fault set M, the minimum increase value of the total power of each member line in the power transmission cross-section J is:
when the constraint condition is met, the following formula is an optimization objective function, and the minimum added value of the total power of each member line of the power transmission section J is determined by adopting an optimization algorithm of linear programming:
wherein,
when the expected failure m occurs and the transmission power of the member line i reaches the threshold value, the transmission power of the power transferred by the expected short-circuit failure line m is not included in each member line j in the transmission section.
Aiming at the multivariable and multi-constraint optimization problem, the global optimum value can be ensured to be obtained by adopting linear programming, and the searching efficiency is ensured.
Further, in the method, when the transmission power of the member line i reaches the out-of-limit threshold value due to the occurrence of the expected open circuit fault on the line m, the minimum increase value of the total power sum of the member lines of the power transmission section J uniquely corresponds to the method for adjusting the power generation/load power of the power transmission section transmitting/receiving end.
Further, in the method, in step S10, the obtaining of the basic parameters of the power transmission section J includes:
obtaining the operation of the power grid from an online monitoring device;
in step S20, the acquiring the set M of the expected faults of the power transmission cross section is:
and obtaining the data from the power grid security check device.
Further, the method comprises the following steps of,
and sending the adjusting method of the power generation/load power of the transmitting and receiving end of the power transmission section corresponding to the minimum added value of the total power of all the member lines of the power transmission section J to a power grid operation online regulating and controlling device when the expected open circuit fault of the line m causes the transmission power of the member line i to reach an out-of-limit critical value.
After the power grid operation online regulation and control device receives the method for regulating the power generation/load power of the transmitting end and the receiving end of the power transmission section, the power grid operation online regulation and control device carries out power grid dispatching and operation according to the regulating quantity of the power generation load power of the transmitting end and the receiving end under the conservative stability limit of the power transmission section, and is favorable for improving the stability of the power grid.
It should be understood that the online monitoring device for power grid operation, the online checking device for power grid safety, and the online regulating device for power grid operation all adopt technical solutions known to those skilled in the art, such as real-time measurement of basic parameters of a power transmission section, for example, determination of a power transmission section and an expected fault set of the power transmission section, adjustment of power generation/load power at a transmitting end and a receiving end of the power transmission section in a power grid, and the like.
In summary, according to the method for determining the conservative stability limit of the power transmission section based on the optimization calculation, firstly, the adjustment direction of the conservative limit of the power transmission section is determined, then, the constraint condition of the conservative limit of the power transmission section is provided, then, the optimization target of the optimization calculation of the conservative limit of the power transmission section is determined, and finally, the conservative limit of the power transmission section is solved through optimization.
The method can quickly determine the conservative limit of the power transmission section of the power grid, and is higher in speed and accuracy; the conservative limit is used for guaranteeing the safety of the short-time power grid when the power grid is subjected to an expected accident situation, providing decision support for making power grid dispatching measures and providing reliable technical support for the operation of the power market.
As shown in fig. 2, another embodiment of a method for quickly determining conservative limits of a power transmission section based on optimization calculation includes the following steps:
1) determining the adjustment direction of the conservative limit of the power transmission section;
2) aiming at each member line in the power transmission section, aiming at each expected fault, calculating a stability limit of a limit value reached by a certain member line under the certain expected fault one by one, and taking the stability limit as a power transmission section conservative limit taking the expected fault of the member line as a reference;
3) determining a constraint condition of a conservative limit of a power transmission section by taking a certain expected fault of a certain member line as a reference;
4) determining an optimization target of power transmission section conservative limit optimization calculation by taking a certain expected fault of a certain member line as a reference;
5) obtaining a conservative limit of a power transmission section by taking a certain expected fault of a certain member line as a reference;
6) the conservative limits for the entire transmission section are determined synthetically.
It should be noted that, the optimization is for a certain expected fault of a certain member line, and for each expected fault of each member line, whether other member lines are out of limit is judged, and one optimization solution needs to be performed; therefore, for a cross section consisting of N member lines, N × N (N-1) sub-optimal solution is required.
And selecting a combined adjustment mode of the output and the load of the unit, so that the power of the member line is a critical value when the expected fault occurs, and other non-fault lines on the power transmission section are not out of limit, wherein the sum of the transmission power of each member line on the power transmission section is a conservative limit value corresponding to the expected fault of the line.
Preferably, the conservative limit of the entire transmission section is the minimum of the above line conservative limits. It should be understood that other statistically significant numbers of features, such as median, may be selected.
Generally, any power transmission section J in the power grid consists of a plurality of member lines; when power grid dispatching measures are made, it is required to ensure that all member lines of a power transmission section J do not exceed the limit in the ground state and after an expected fault occurs, namely short-time power grid safety, namely power grid static safety.
The set of anticipated faults M of the power transmission section J typically contains anticipated faults and other related faults that may occur on all member lines on the power transmission section.
It should be understood that each of the expected failure modes for each member line in the expected failure set M is an independent failure, and each of the expected failure modes is independent of each other; it is envisioned that failure set M does not include an associated failure.
Because the load rates of all member lines of the power transmission section are different, when the output power and/or the load receiving power of a generator set at the transmitting and receiving ends of the power transmission section are/is adjusted to increase the transmittable power on the power transmission section, the power increase proportion of all member lines of the power transmission section is possibly different, so that the stability limit of the power transmission section is different in different power increase modes.
Therefore, the determining of the adjustment direction of the conservative stability limit of the power transmission section in the step 1) comprises the following steps:
the conservative stability limit of the power transmission section is adjusted in the following way: the power of the member lines of the power transmission section with the heavier load rate is preferentially increased as much as possible, and the power of the member lines of the power transmission section with the lighter load rate is slowly increased as much as possible.
Therefore, when the power of the power transmission section is increased, the member lines of the power transmission section are easy to exceed the limit in the ground state and after expected faults, and the determined stability limit of the power transmission section is smaller and accords with the conservation principle of a power grid.
Wherein, the step 2) is to calculate, for each member line of the power transmission section and for each expected fault, a stability limit when the load of a member line reaches a limit value under a certain expected fault by one member line, as a power transmission section conservative stability limit with the expected fault of the line as a reference, specifically as follows:
calculating for each member line i of the power transmission section JTransmission section limit X at which line i reaches a limit after each expected fault mim。
That is, a conservative stability limit is determined for each expected failure of the member line i.
Wherein, the step 3) determines a constraint condition of a conservative stability limit of a power transmission section with reference to a certain expected fault of a certain member line, and specifically comprises the following steps:
and the constraint conditions of the conservative stability limit of the power transmission section by taking the expected fault m of the member line i as a reference comprise the thermal stability constraint of the member line i of the power transmission section, the constraint of power generation and load adjustment of a power transmission section transmitting and receiving end and the load balance constraint of the power generation and load adjustment.
1) Thermally stable constraint of member line i of power transmission section J
The method is defined as that the initial power (namely the power in the ground state) and the power after the expected fault of all member lines of a power transmission section meet the rated ampacity constraint of the line, namely the power flow of each line after the other lines have the expected fault exceeds the limit.
The following is given as the thermal stability constraint of any member line i in anticipation of fault m:
in the above formula, PiIs the initial power of line i;
Pi+Pmλm-ito predict the transmission power of line i after a fault m (e.g., an open circuit fault in line m) has occurred;
Pi maxis the ultimate active power of line i;
λm-iin order to anticipate that the power of the line m is transferred to the distribution factor of the line i after the fault m occurs (e.g. the line m is broken), the value of the distribution factor is predetermined according to the grid topology and the electrical basic parameters of the line and remains fixed during the grid regulation.
In determining the conservative stability limit of a power transmission section, all member lines j (including the line in which the fault is expected and also the line i currently under investigation) in the power transmission section also need to satisfy similar thermal stability constraints at the time of the fault m.
2) Regulating power constraints of the equipment, i.e. constraints on power generation and load regulation at the transmitting and receiving ends of the transmission section
And the power adjustment of the generator set and the load at the transmitting and receiving end of the power transmission section is restricted, specifically, the output of the generator set is between the minimum allowable output and the maximum allowable output, and the received power of the load is between the allowable range of the load.
Given that the number and location of the transmitting and receiving end gensets, loads are fixed for a transmission section, the power constraints of the regulating device are the same for any combination of member lines and anticipated faults within the transmission section.
3) Load flow balance constraints, i.e. load flow balance constraints for power generation load adjustment
When the power transmission section is adjusted to transmit and receive the generator set and the load power, the load power should meet the load flow balance constraint, namely the power generation increased power is matched with the load received power.
Wherein, the step 4) determines an optimization target of the power transmission section conservative stability limit optimization calculation by taking a certain expected fault of a certain member line as a reference, and comprises the following steps:
and the optimization target of the power transmission section conservative stability limit optimization calculation by taking the expected fault m of the member line i as a reference is the optimization target of the total power sum of all member lines of the power transmission section before the occurrence of the expected fault m before the fault is the minimum when the current-carrying capacity of the member line i reaches the limit value when the expected fault m occurs.
Wherein,
when the predicted fault m occurs and the transmission power of the member line i reaches the threshold value, the power transferred by the predicted short-circuit fault line m is not included in each member line j in the transmission sectionThe transmission power of (1).
That is, the sum of the powers of all the member lines of the power transmission section before the occurrence of the fault m is expected.
At this time, the constraint that "the occurrence of the expected fault m will cause the line i to exceed the limit, and the other lines do not exceed the limit" is satisfied.
That is, when the current determined power increase method (corresponding to the corresponding transmission section transmitting and receiving end generator set and load power adjustment mode, the adjustment mode redistributes active power among member lines, so that each member line has corresponding redistributed power, and the adjustment mode increases the total power of the section), and the expected fault m occurs, the active power transferred by the expected short-circuit fault line m is received on the line i; at this time, the member line i reaches the out-of-limit critical value under the combined action of the current redistributed power and the active power transferred by the expected short-circuit fault line m; at this time, the other member lines do not go out of limit (that is, satisfy the thermal balance theorem) under the combined action of the respective current redistributed power and the active power transferred from the expected short-circuit fault line m.
Wherein, the step 5) of obtaining the conservative stability limit of the power transmission section by taking a certain expected fault of a certain member line as a reference comprises the following steps:
and (3) solving a conservative stability limit of the power transmission section by taking the expected fault m of the member line i as a reference, and solving an optimal solution through optimization calculation, wherein the result comprises the following steps:
1) and the adjustment quantity of the power generation load power of the transmitting and receiving end of the power transmission section is referred by a power supply network scheduling operator and is used as a reference for power grid scheduling operation and power market operation.
2) And adding the power of all member lines of the power transmission section corresponding to the adjustment quantity of the power generation load power of the transmitting and receiving end of the power transmission section, namely the conservative stability limit of the power transmission section.
Wherein, the step 6) of comprehensively determining the conservative stability limit of the power transmission section comprises the following steps:
and taking the minimum value of the conservative stability limit of the power transmission section by taking each expected fault of each member line as reference as the conservative stability limit of the power transmission section.
Up to this point, the stability limits for the worst case on the transmission profile have been found. And guiding the operation of the power grid according to the adjustment mode and the stability limit, so that the safety level of the operation of the power grid can be improved.
And analyzing the operation data of the power grid in North-China at a certain daily load peak period by taking the operation data as an example, and calculating the conservative stability limit of the power transmission section based on the optimized calculation by taking the Yu jaw section as an example. As shown in table 1, the yu jaw cross section is composed of 4 lines. The set of predicted faults to be considered when calculating the conservative stability limit of the Yu jaw cross-section is shown in Table 2. With the method for quickly determining the conservative stability limit of a power transmission section based on optimization calculation according to this embodiment, the stability limits of the power transmission section with reference to different member lines and different expected faults are shown in table 3.
Watch 1 Yu jaw section combined watch
| Serial number | Line name | Line power (MW) |
| 1 | Chinese coiled dragon I line | 239 |
| 2 | Huazhong coiled dragon II line | 221 |
| 3 | Zhang en I loop in Huazhong | 105 |
| 4 | Zhangenii loop in Huazhong | 105 |
Watch 2 Yu jaw section fault set
| Serial number | Line name |
| 1 | Zhang en I loop in Huazhong |
| 2 | Zhangenii loop in Huazhong |
| 3 | Chinese coiled dragon I line |
| 4 | Huazhong coiled dragon II line |
TABLE 3 stability limit of Yu jaw section under different references
| Serial number | Expected failure | Reference member line name | Stability Limit (MW) |
| 1. | Huazhong coiled dragon II line | Chinese coiled dragon I line | 2453 |
| 2. | Zhang en I loop in Huazhong | Chinese coiled dragon I line | 4930 |
| 3. | Zhangenii loop in Huazhong | Chinese coiled dragon I line | 4930 |
| 4. | Chinese coiled dragon I line | Huazhong coiled dragon II line | 2596 |
| 5. | Zhang en I loop in Huazhong | Huazhong coiled dragon II line | 5823 |
| 6. | Zhangenii loop in Huazhong | Huazhong coiled dragon II line | 5823 |
| 7. | Chinese coiled dragon I line | Zhang en I loop in Huazhong | 7299 |
| 8. | Huazhong coiled dragon II line | Zhang en I loop in Huazhong | 7423 |
| 9. | Zhangenii loop in Huazhong | Zhang en I loop in Huazhong | 3994 |
| 10. | Chinese coiled dragon I line | Zhangenii loop in Huazhong | 7300 |
| 11. | Huazhong coiled dragon II line | Zhangenii loop in Huazhong | 7424 |
| 12. | Zhang en I loop in Huazhong | Zhangenii loop in Huazhong | 3994 |
In view of the fault of the line A, only the critical value when other lines are out of limit needs to be judged; therefore, from tables 1 and 2, the stability limits after the combination of the 12 member lines and the expected faults in table 3 can be determined.
The minimum value of each line and the expected fault combination is 2453MW, namely the conservative stability limit of the Yu jaw section is 2453 MW. And (4) making a power grid dispatching measure according to the conservative stability limit, and then, in the power transmission section, the central line I of the coiled dragon is in the central line and the central line II of the coiled dragon is out of limit when the fault occurs.
The invention has been described above by reference to a few embodiments. However, other embodiments of the invention than the one disclosed above are equally possible within the scope of the invention, as would be apparent to a person skilled in the art from 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/an/the [ device, component, etc ]" are to be interpreted openly as referring to at least one instance of said device, component, etc., unless explicitly 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 a conservative stability limit of a power transmission section based on optimization calculation is characterized by comprising the following steps:
step S10: obtaining basic parameters of a power transmission section J, wherein the basic parameters comprise: rated current carrying capacity of each member line J of the power transmission section J, ground state power of each member line J, and power generation/load information of a transmitting end and a receiving end;
step S20: acquiring an expected fault set M of the power transmission section, wherein the expected fault set M comprises a plurality of lines expected to generate open circuit faults;
step S30: determining a minimum increase value of the total power of each member line of the power transmission section J when the transmission power of the member line i reaches an out-of-limit critical value due to the occurrence of an expected open-circuit fault on a line M in the expected fault set M by adjusting the power generation/load power of the transmission section transmission and reception end and the power generation/load of each member line J and the transmission section transmission and reception end in the power transmission section meet preset constraint conditions,
the minimum added value of the total power is a conservative stability limit of the member line i when an expected open circuit fault occurs in a line m, wherein i is not equal to j is not equal to m;
when the constraint condition is met, the following formula is an optimization objective function, and the minimum added value of the total power of each member line of the power transmission section J is determined by adopting an optimization algorithm of linear programming:
wherein,
when the expected failure m occurs and the transmission power of the member line i reaches the out-of-limit critical value, the transmission power of the power transferred by the expected open failure line m is not included on each member line j in the power transmission section;
step S40: sequentially selecting a line M expected to have an open-circuit fault corresponding to the line i from the expected fault set M, and repeating the step S30,
and obtaining a local conservative stability limit Li of the power transmission section determined by the member line i, wherein the local conservative stability limit Li is the minimum value of conservative stability limits respectively determined by the member line i when a plurality of expected open circuit faults occur.
2. The optimization calculation-based power transmission section conservative stability limit determination method according to claim 1,
after step S40, the method further includes:
sequentially selecting member lines in the power transmission section, and repeating the steps from S30 to S40 to obtain a global conservative stability limit L of the power transmission section determined by each member line j;
the global conservative stability limit L is a minimum value among local conservative stability limits respectively determined by each member line j.
3. The optimization calculation-based power transmission section conservative stability limit determination method according to claim 2,
in step S30, the adjusting of the power generation/load power of the transmission/reception end of the transmission section includes:
determining 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 ground state power of each member line J;
when the power generation/load power of the transmitting and receiving end of the power transmission section is adjusted to change the transmission power of each member line j, preferentially increasing the power of the member line with the heavier load rate; or
The transmission power of the member line with lighter load rate is increased more slowly.
4. The optimization calculation-based power transmission section conservative stability limit determination method according to claim 2,
in step S30, the condition that each member line j in the power transmission section satisfies a predetermined constraint condition is:
each member line j in the power transmission section satisfies the following thermal stability constraint:
the ground state power of each member line j and the transmission power of the member line j after the expected fault occurs are both smaller than the rated current-carrying capacity:
wherein, PjThe ground state power of the member line j;
Pmthe ground state power of the member line m before the open circuit fault occurs;
Pj maxthe limit active power is determined by the rated current-carrying capacity of the line j and the current working voltage;
λm-jand after the member line m has an open circuit fault, the member line m transfers the distribution factor of the power to the member line j.
5. The optimization calculation-based power transmission section conservative stability limit determination method according to claim 2,
in step S30, the power generation/load at the power transmission section transmitting/receiving end satisfies a predetermined constraint condition, and the constraint condition is:
the output power of the power generation is between the minimum allowable output and the maximum allowable output, and the received power of the load is between the maximum allowable load and the minimum allowable load; and
the power generation/load of the transmission and receiving ends of the transmission section meets the tidal current balance constraint.
6. The optimization calculation-based power transmission section conservative stability limit determination method according to claim 2,
when the transmission power of the member line i reaches the out-of-limit critical value due to the occurrence of the expected open circuit fault on the line m, the minimum increment of the total power sum of each member line of the power transmission section J uniquely corresponds to the method for adjusting the power generation/load power of the transmitting end and the receiving end of the power transmission section.
7. The optimization calculation-based power transmission section conservative stability limit determination method according to claim 2,
in step S10, the obtaining of the basic parameters of the power transmission section J includes:
obtaining the operation of the power grid from an online monitoring device;
in step S20, the acquiring the set M of the expected faults of the power transmission cross section is:
and obtaining the data from the power grid security check device.
8. The optimization calculation-based power transmission section conservative stability limit determination method according to claim 6,
and sending the adjusting method of the power generation/load power of the transmitting and receiving end of the power transmission section corresponding to the minimum added value of the total power of all the member lines of the power transmission section J to a power grid operation online regulating and controlling device when the expected open circuit fault of the line m causes the transmission power of the member line i to reach an out-of-limit critical value.
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