CN109546650B - Method and device for estimating transient stability limit of power transmission channel - Google Patents

Method and device for estimating transient stability limit of power transmission channel Download PDF

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CN109546650B
CN109546650B CN201811462312.9A CN201811462312A CN109546650B CN 109546650 B CN109546650 B CN 109546650B CN 201811462312 A CN201811462312 A CN 201811462312A CN 109546650 B CN109546650 B CN 109546650B
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fault
generator
transmission channel
angle
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CN109546650A (en
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程雪婷
张文朝
郑惠萍
杨俊炜
刘新元
张亚丽
薄利明
段伟文
杨尉薇
曲莹
王玮茹
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Electric Power Research Institute of State Grid Shanxi Electric Power Co Ltd
Beijing Kedong Electric Power Control System Co Ltd
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Electric Power Research Institute of State Grid Shanxi Electric Power Co Ltd
Beijing Kedong Electric Power Control System Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • 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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • 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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Abstract

The disclosure provides a method and a device for estimating transient stability limit of a power transmission channel, and belongs to the field of power systems. The power transmission channel transient stability limit estimation method and device are applied to a power system, the power system comprises a generator and a power transmission channel, the transient stability limit power before and after the fault of the power transmission channel is obtained, the power angle of the generator when the fault is removed is obtained through calculation according to the transient stability limit power before and after the fault of the power transmission channel, the coefficient K is obtained through calculation according to the power angle of the generator when the fault is removed after the power angle of the generator when the fault is removed, the transient stability limit power of the power transmission channel is obtained through calculation according to the transient stability limit power after the fault of the power transmission channel and the coefficient K after the coefficient K is obtained, voltage reactive power does not need to be adjusted repeatedly, and the calculation efficiency is greatly improved.

Description

Method and device for estimating transient stability limit of power transmission channel
Technical Field
The disclosure relates to the field of power systems, in particular to a method and a device for estimating transient stability limit of a power transmission channel.
Background
With the increase of the electric load, the regional structure of the power grid is more complex, the power exchange capacity among the regions has great influence on the safety and stability of the power grid, and in addition, the flexible variability of the operation mode and the operation working condition of the modern power system, the power transmission capacity also changes along with the change of the mode and the working condition. Therefore, there is a need to accurately and quickly determine the power transmission capability of the tie line, so as to meet the demand of the electrical load to the maximum extent on the premise of meeting the safety and reliability, thereby improving the rapidity of decision making.
In engineering, the transient stability limit power is calculated by adopting a time domain simulation program, the output of a generator set at a transmitting end and a receiving end needs to be changed in power flow, and a stability limit value is approached by continuous simulation. However, if the load flow calculation is not converged due to serious voltage drop of the system under the condition of heavy load flow, the worker needs to adjust the voltage reactive power to enable the load flow calculation to be converged again, and the operation is complex and the efficiency is low.
Disclosure of Invention
In view of the above, the present disclosure provides a method and an apparatus for estimating transient stability limit of a power transmission channel.
The present disclosure provides a method for estimating transient stability limit of a power transmission channel, which is applied to a power system, wherein the power system comprises a generator and the power transmission channel, and the method comprises the following steps:
and acquiring the static limiting power before and after the power transmission channel fails.
And calculating a power angle when the generator removes the fault according to the static limiting power before and after the fault of the power transmission channel.
And calculating a coefficient K according to the power angle when the generator cuts off the fault.
And calculating transient stability limit power according to the static stability limit power after the power transmission channel fails and the coefficient K.
Further, the power system further includes a sending terminal unit and a receiving terminal unit, the sending terminal unit and the receiving terminal unit are connected through the power transmission channel, and the step of obtaining the static limiting power before and after the power transmission channel fails includes:
and according to a static power angle stabilization practical algorithm, gradually increasing the power of the sending end unit, and correspondingly reducing the power of the receiving end unit so as to respectively calculate and obtain the static power angle stabilization limits before and after the transmission channel fault.
And respectively obtaining the maximum transmission power of the transmission channel or the section before and after the transmission channel fault according to the static power angle stability limits before and after the transmission channel fault, and taking the obtained maximum transmission power of the transmission channel or the section before and after the transmission channel fault as the static limit power before and after the fault.
Further, the step of calculating the power angle of the generator when the fault is removed according to the steady limit power before and after the fault of the power transmission channel comprises the following steps:
calculating an initial power angle delta of the generator according to the static limiting power before and after the transmission channel fault by the following formula0：
Figure BDA0001887481520000031
According to the initial power angle delta of the generator0The rated active power and the rotational inertia of the generator are calculated by the following formula to obtain a power angle delta when the generator is subjected to fault removalc：
Figure BDA0001887481520000032
Wherein, PImaxFor the steady limit power before failure, PIImaxFor the steady limit power after a fault, PnFor rated active power of the generator, PTIs the mechanical power of prime mover under the same initial power flow, omega0To the initial generator speed, TjIs the moment of inertia, t is the fault time, during the calculation,
Figure BDA0001887481520000033
further, according to the power angle of the generator when the fault is removed, the coefficient K is calculated by the following formula:
Figure BDA0001887481520000034
wherein, deltacFor removing the power angle when the fault occurs, pi-delta st is the power angle when the limit is reached, namely the stable limit of the static power angle after the fault, delta0Is the initial power angle of the generator.
Further, the coefficient K is obtained by:
and calculating the acceleration area of the unit from the short circuit to the fault removal time.
And calculating the deceleration area of the unit from the fault removal moment to the limit removal angle moment.
Based on the equal area principle, the unit acceleration area is equal to the unit deceleration area, and the coefficient K is obtained.
Further, the unit acceleration area is calculated by the following formula:
Sadding＝(δC-δ0)×PT＝(δC-δ0)×PIImax×sinδst；
Wherein, delta0For the initial power angle, delta, of the generator in normal operationcThe power angle when the fault is removed for the generator, pi-delta st is the power angle when the limit is reached, PIImaxFor the steady limit power after a fault, PTRepresenting the mechanical power of the prime mover in the same initial power flow.
Further, the unit deceleration area is calculated by the following formula:
Figure BDA0001887481520000041
wherein, deltacTo remove the power angle at fault, pi- δ st is the power angle at the limit, PIImaxFor the steady limit power after a fault, PTRepresenting the mechanical power of the prime mover, P, at the same initial tideEIs electromagnetic power.
Further, based on the equal area principle, the unit acceleration area is equal to the unit deceleration area, and the step of obtaining the coefficient K includes:
defining Δ E as deceleration energy-acceleration energy as deceleration area-acceleration area, and calculating:
ΔE＝Sreducing-SAdding＝PIImax×(cosδst+cosδC)-PIImax×sinδst×(π-δst-δC)-(δC-δ0)×PIImax×sinδst；
Simplifying to obtain:
ΔE＝PIImax×(cosδst+cosδC)-PIImax×sinδst×(π-δst+δ0)；
based on the equal area principle, the unit acceleration area is equal to the unit deceleration area, Δ E is obtained as 0, and the calculation result is:
Figure BDA0001887481520000042
introducing a coefficient K, making K equal to sin deltastObtaining:
Figure BDA0001887481520000051
wherein, deltacFor removing the power angle at fault, pi-deltastTo achieve the limit time power angle, PIImaxFor the post-fault quiescent limit power, delta0The initial power angle of the generator in normal operation.
Further, the transient stability limit power is calculated by the following formula:
Pst＝K×PIImax；
wherein, PstFor temporarily stabilizing the limiting power, PIImaxFor the post-failure restful limitAnd (4) power.
The utility model provides an estimation device of transmission channel transient stability limit, is applied to electric power system, electric power system includes generator and transmission channel, the estimation device includes processing module and calculation module, processing module is used for obtaining transmission channel before the trouble and after the trouble statics limit power.
The calculation module is used for calculating a power angle when the generator removes the fault according to the static limiting power before and after the fault of the power transmission channel, and calculating a coefficient K according to the power angle when the generator removes the fault; and calculating transient stability limit power according to the static stability limit power after the generator fails and the coefficient K.
The power transmission channel transient stability limit estimation method and device are applied to a power system, the power system comprises a generator and a power transmission channel, the transient stability limit power before and after the fault of the power transmission channel is obtained, the power angle when the fault of the generator is removed is obtained according to the transient stability limit power before and after the fault of the power transmission channel, the coefficient K is obtained according to the power angle when the fault of the generator is removed after the power angle when the fault of the generator is removed, the transient stability limit power of the power transmission channel is obtained according to the transient stability limit power after the fault of the power transmission channel and the coefficient K after the coefficient K is obtained, voltage reactive power does not need to be adjusted repeatedly, operation is convenient and fast, and calculation efficiency is greatly improved.
In order to make the aforementioned objects, features and advantages of the present disclosure more comprehensible, preferred embodiments accompanied with figures are described in detail below.
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To more clearly illustrate the technical solutions of the present disclosure, the drawings needed for the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present disclosure, and therefore should not be considered as limiting the scope, and those skilled in the art can also obtain other related drawings based on the drawings without inventive efforts.
Fig. 1 is a block diagram of an electrical power system provided by the present disclosure.
Fig. 2 is a schematic flow chart of a method for estimating transient stability limit of a power transmission channel according to the present disclosure.
Fig. 3 is another schematic flow chart of the method for estimating transient stability limit of a power transmission channel provided by the present disclosure.
Fig. 4 is a power-angle characteristic curve of a single-machine infinite system provided by the present disclosure.
Fig. 5 is a quiet curve of a power transmission channel in a normal mode of the present disclosure.
Fig. 6 is a quiet curve of a power transmission channel after a fault of the present disclosure.
Fig. 7 is a power angle curve of a generator after a fault according to the present disclosure.
Fig. 8 is a power angle curve of the transient stabilized generator of the present disclosure.
Fig. 9 is an active power curve of a power transmission channel after transient stabilization according to the present disclosure.
Fig. 10 is a block diagram of an estimation apparatus for transient stability limit of a power transmission channel provided by the present disclosure.
Icon: 100-an electric power system; 10-sending end machine set; 11-a generator; 20-receiving end machine set; 30-an estimation device; 31-a processing module; 32-calculation module.
Detailed Description
The technical solutions in the present disclosure will be described clearly and completely with reference to the accompanying drawings in the present disclosure, and it is to be understood that the described embodiments are only a part of the embodiments of the present disclosure, and not all of the embodiments. The components of the present disclosure, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present disclosure, presented in the figures, is not intended to limit the scope of the claimed disclosure, but is merely representative of selected embodiments of the disclosure. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the disclosure without making creative efforts, shall fall within the protection scope of the disclosure.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.
With the increase of the electric load, the regional structure of the power grid is more complex, the power exchange capacity among the regions has great influence on the safety and stability of the power grid, and in addition, the flexible variability of the operation mode and the operation working condition of the modern power system, the power transmission capacity also changes along with the change of the mode and the working condition. Therefore, there is a need to accurately and quickly determine the power transmission capability of the tie line, so as to meet the demand of the electrical load to the maximum extent on the premise of meeting the safety and reliability, thereby improving the rapidity of decision making.
Theoretically, the transient stability limit is generally analyzed by adopting a direct method, and the direct method has a good prospect in the online application of the transient safety analysis due to the characteristic of high calculation speed, but still gets rid of the defects of direct method conservation and model limitation, and in a word, the transient stability limit analysis by using the direct method is limited by the corresponding calculation precision and speed of the direct method. In engineering, the transient stability limit power is calculated by adopting a time domain simulation program, the output of a generator set at a transmitting end and a receiving end needs to be changed in power flow, and a stability limit value is approached by continuous simulation. However, if the system is severely subjected to voltage sag to cause the non-convergence of the power flow calculation under the condition of heavy power flow, the personnel needs to adjust the voltage reactive power to enable the power flow calculation to be re-converged. This process of tuning is time consuming, complex to operate and inefficient.
Based on the above research, the present disclosure provides a method and an apparatus for estimating transient stability limit of a power transmission channel, so as to improve the above problem.
Referring to fig. 1, the method for estimating transient stability limit of a power transmission channel provided by the present disclosure is applied to a power system 100 shown in fig. 1, where the power system 100 includes a sending-end unit 10, a receiving-end unit 20, and a power transmission channel, the sending-end unit 10 and the receiving-end unit 20 are connected through the power transmission channel, so that the sending-end unit 10 transmits power to the receiving-end unit 20, and the sending-end unit 10 includes a generator 11.
Referring to fig. 2, fig. 2 is a schematic flow chart of a method for estimating transient stability limit of a power transmission channel according to the present disclosure. The flow diagram shown in fig. 2 is specifically described below.
Step S10: and acquiring the static limiting power before and after the power transmission channel fails.
The purpose of the static stability calculation and analysis of the power system 100 is to apply corresponding criteria to determine the static stability of the operating points to which the power system 100 is loaded one by one, to obtain the static transmission power limit and the static stability reserve in a given mode, and to check whether the static stability reserve in the given operating mode meets the requirements. Therefore, static stability analysis is required for large power supply outgoing lines, weak-connection power grid connecting lines, large receiving end systems, weak sections in networks and the like.
Further, referring to fig. 3, the step of obtaining the before-fault and after-fault quiescent limit powers of the power transmission channel includes steps S11 to S12.
Step S12: according to a static power angle stabilization practical algorithm, the power of the sending terminal unit 10 is gradually increased, and the power of the receiving terminal unit 20 is correspondingly reduced, so that the static power angle stabilization limits before and after the transmission channel fault are respectively calculated.
Step S12: and respectively obtaining the maximum transmission power of the transmission channel or the section before and after the transmission channel fault according to the static power angle stability limits before and after the transmission channel fault, and taking the obtained maximum transmission power of the transmission channel or the section before and after the transmission channel fault as the static limit power before and after the fault.
The static power angle stability calculation method generally includes two methods, namely a feature root discrimination method and a static power angle stability practical algorithm.
The general process of the feature root discrimination method is as follows: calculating the steady state values of the load flow distribution and the state quantity in a given operation mode; and (3) linearizing an equation describing the transient process near a steady state value to form a characteristic matrix, and judging the static stability of the system according to the property of the characteristic value. And if the real number characteristic root does not exist, judging that the static power angle is stable.
The static power angle stabilization practical algorithm adopts a stable calculation program, gradually increases the power of the sending end unit 10, correspondingly reduces the power of the receiving end unit 20 until the system generates aperiodic distortion, and the corresponding power angle is the stable limit of the static power angle at the moment. Namely the static power angle stability limit, and meanwhile, the maximum transmission power of the transmission channel or the section is obtained according to the static power angle stability limit, and the power is used as the static stability limit power.
Optionally, in the calculation process of the static limiting power, the static power angle stability practical algorithm is selected for use in the disclosure, and the obtained static limiting power is used as an effective evaluation index for judging the stability of the power system 100.
The restabilization limit power-characterizes the maximum transmission capacity of the alternating current section (channel).
Figure BDA0001887481520000101
Wherein, PmaxTo a steady limit power, EqIs the internal potential of the generator 11, U is the infinite node voltage, δ is the rotor angle of the generator 11, XdIs the sum of the synchronous reactance of the generator 11, the equivalent reactance of the channel line and the equivalent reactance of the transformer.
In the calculation process, the frequency and the voltage of the system should be ensured to be within a normal range as much as possible, so that the speed regulation system and the excitation system in the sending end unit 10 and the receiving end unit 20 are considered to ensure that the increase and decrease of the power are basically balanced. Meanwhile, the power increase and decrease scheme is required to be in accordance with the actual power flow direction, and different schemes may obtain different static stability limits. Because in a multi-machine system, different transition schemes may occur when the normal operation mode is transited to the stable limit operation condition, and different operation schemes may obtain different stable limits, different adjustment modes of power generation or load in each region may cause that the obtained static stable power limits of the connecting line may have a difference of about 10% -20%. When the unit for increasing the output is positioned at the near end of the connecting line, the static stability limit can be increased due to the improvement of the voltage reactive support; when the power-added unit is located at the far end of the connecting line, the voltage along the line is reduced because the power is transmitted in a long distance, so that the static stability limit is reduced. Similarly, the force reducing unit may also have the same effect on the instability limit when located near or far from the tie line.
And after obtaining the static power angle stability limit and the static limit power before and after the fault according to the obtained static power angle stability practical algorithm, entering the step S20.
Step S20: and calculating the power angle of the generator 11 when the fault is removed according to the static limiting power before and after the fault of the power transmission channel.
The power angle when the generator 11 removes the fault is calculated according to the instability limit power before and after the fault of the power transmission channel, and the power angle can be obtained through a process 1 and a process 2.
Scheme 1: calculating an initial power angle delta of the generator 11 according to the static limiting power before and after the transmission channel fault by the following formula0：
Figure BDA0001887481520000111
And (2) a flow scheme: according to the initial power angle delta of the generator 110The rated active power and the rotational inertia of the generator 11 are calculated by the following formula to obtain a power angle delta when the generator 11 is in fault removalc：
Figure BDA0001887481520000112
Wherein, PImaxFor the steady limit power before failure, PIImaxFor the steady limit power after a fault, PnFor rating the active power, P, of the generator 11TIs the mechanical power of prime mover under the same initial power flow, omega0For the initial generator 11 speed, TjAs the moment of inertia, in the calculation process,
Figure BDA0001887481520000113
and t is the failure time.
After obtaining the power angle at which the generator 11 is out of order, the process proceeds to step S30.
Step S30: and calculating a coefficient K according to the power angle when the generator 11 cuts the fault.
Wherein, according to the power angle when the generator 11 cuts off the fault, the coefficient K is calculated by the following formula:
Figure BDA0001887481520000114
wherein, deltacFor removing the power angle when the fault occurs, pi-delta st is the power angle when the limit is reached, namely the stable limit of the static power angle after the fault, delta0Is the initial power angle of the generator 11.
After the coefficient K is obtained, the process proceeds to step S40.
Step S40: and calculating transient stability limit power according to the static stability limit power after the power transmission channel fails and the coefficient K.
Transient stability is the ability of each synchronous motor to maintain synchronous operation and transition to a new or return to the original steady state operation mode after the power system 100 is subjected to large disturbance. The transient stability calculation and analysis aims to verify the transient stability of the system under a specified operation mode and a specified fault state, research a control strategy for ensuring the safety and stability of a power grid, and provide corresponding requirements for relay protection, automatic devices and various safety and stability measures. The power system 100 can transit from the original operation state (balance point) to the new operation state after a large disturbance in the normal operation and stably operate in the new operation state. If the power angle can be stabilized at a certain value after oscillation, it indicates that synchronous operation is restored between the generators 11, and the system has transient stability, otherwise if the power angle is continuously increased, it indicates that the system loses transient balance. Therefore, the time-varying characteristic of the power angle after large disturbance is used as the transient stability criterion.
In the present disclosure, the transient stability limit power is calculated by the following formula:
Pst＝K×PIImax；
wherein, PstFor temporarily stabilizing the limiting power, PIImaxThe power limit is the steady state power after the fault. In the method, after the value of the coefficient K is obtained, the transient stability limit power can be rapidly estimated according to the static stability limit power after the fault and the coefficient K, and the calculation efficiency is greatly improved.
Further, referring to fig. 4, fig. 4 is a power angle characteristic curve of the single-machine infinite system constructed according to the present disclosure, and the coefficient K is obtained through the processes 3 to 5.
And (3) a flow path: and calculating the acceleration area of the unit from the short circuit to the fault removal time.
The unit is a sending-end unit 10, and the unit acceleration area is calculated by the following formula:
Sadding＝(δC-δ0)×PT＝(δC-δ0)×PIImax×sinδst；
Wherein, delta0For the initial power angle, delta, of the generator 11 in normal operationcThe power angle at which the fault is removed for the generator 11, pi- δ st is the power angle at which the limit is reached, PIImaxFor the steady limit power after a fault, PTRepresenting the mechanical power of the prime mover in the same initial power flow.
And (4) a flow chart: and calculating the deceleration area of the unit from the fault removal moment to the limit removal angle moment.
Further, the unit deceleration area is calculated by the following formula:
Figure BDA0001887481520000131
wherein, deltacTo remove the power angle at fault, pi- δ st is the power angle at the limit, PIImaxFor the steady limit power after a fault, PTRepresenting the mechanical power of the prime mover, P, at the same initial tideEIs electromagnetic power.
And (5) a flow chart: based on the equal area principle, the unit acceleration area is equal to the unit deceleration area, and the coefficient K is obtained.
Where Δ E is defined as deceleration energy-acceleration energy as deceleration area-acceleration area, and calculated as:
ΔE＝Sreducing-SAdding＝PIImax×(cosδst+cosδC)-PIImax×sinδst×(π-δst-δC)-(δC-δ0)×PIImax×sinδst；
Simplifying to obtain:
ΔE＝PIImax×(cosδst+cosδC)-PIImax×sinδst×(π-δst+δ0)；
based on the equal area principle, the unit acceleration area is equal to the unit deceleration area, Δ E is obtained as 0, and the calculation result is:
Figure BDA0001887481520000141
introducing a coefficient K, making K equal to sin deltastObtaining:
Figure BDA0001887481520000142
wherein, deltacFor removing the power angle at fault, pi-deltastTo achieve the limit time power angle, PIImaxFor the post-fault quiescent limit power, delta0The initial power angle of the generator 11 for normal operation.
After the coefficient K is obtained through deduction in the process, when the power transmission channel breaks down and the transient stability limiting power of the power transmission channel is calculated, only one simulation calculation is needed to obtain the transient stability limiting power and the coefficient K before and after the fault, the transient stability limiting power can be quickly estimated according to the transient stability limiting power and the coefficient K after the fault, and the calculation efficiency is greatly improved.
The method for estimating transient stability limit of a power transmission channel provided by the present disclosure is verified by the following specific examples. The specific process is as follows.
(1) Adopting PSD-BPA electromechanical transient simulation software to construct a single-machine infinite system, calculating the static stability limit before and after the fault of the power transmission channel, please refer to FIG. 5, wherein FIG. 5 is the static stability curve of the power transmission channel in the normal mode, and in the normal mode, the static stability limit P isImax1651MW, a triple permanent N-1 fault is set at the head end of the line XL, please refer to fig. 6, where fig. 6 is a quiet curve of a power transmission channel after the fault, and the quiet limit after the fault is PIImax＝1268MW。
(2) And determining indexes such as rated active power of the generator 11, a power angle when the fault is removed, rotational inertia and the like. Referring to fig. 7, fig. 7 is a power angle curve of the unit after fault, in which the rated active power P of the generator 11 is shownn1000MW, generator 11 inertial time constant TjPower angle delta at fault removal of generator 11, 10s0＝39°
(3) And calculating the actual transient stability limit power, namely the transient stability limit power. Referring to fig. 8 and 9 in combination, fig. 8 is a power angle curve of the transient-stabilized power unit, and fig. 9 is an active power curve of the transient-stabilized power transmission channel. And calculating by adopting PSD-BPA to obtain the transient stability limit power of 1046MW under the fault of XL Tri-permanent N-1.
(4) The transient stability limit power is estimated by adopting the estimation method of the transient stability limit of the power transmission channel provided by the disclosure. Wherein the generator 11 has a rated active power Pn1000MW, generator 11 inertial time constant TjPower angle delta at fault removal of generator 11, 10s039 deg. Steady limit power P in normal modeImax1651MW, setting fault of three permanent N-1 at head end of line XL, and quiescent limit power P after faultIImax1268 MW. By
Figure BDA0001887481520000151
The K coefficient is calculated to be 0.826 from Pst＝K×PIImaxFast estimation of transient stability limit power Pst＝1047MW。
(5) Temporary stability limit power under XL triple-permanent N-1 fault calculated by PSD-BPA and estimation method of temporary stability limit of power transmission channel provided by the methodAnd comparing the estimated transient stability limiting power. The temporary stability limit power of XL Tri-permanent N-1 fault is calculated to be P by adopting PSD-BPA simulationst1046MW, the disclosure estimates the transient stability limit power Pst1047MW, the error of calculation is 0.09%.
And PSD-BPA electromechanical transient simulation software is adopted to calculate the output transient stability limit power of the Tokton power plant, and the correctness of the estimation method of the transient stability limit of the power transmission channel provided by the disclosure is verified. Rated active power P of Tokton unitn4800MW, time constant of inertia TjThe power angle delta at fault removal of the generator 11 is 9.26s048 deg.. In normal mode, the static limiting power is PImaxSetting 6780MW, setting a Tortto-muddy source line Tortto side three permanent N-1 fault, and setting the static limit power P after the faultIImax6185 MW. Calculating K coefficient to be 0.82, and quickly estimating to obtain transient stability limit power Pst5071 MW. The temporary stability limit power of XL Tri-permanent N-1 under the fault is 5312MW calculated by PSD-BPA, so the calculation error is 4.5%.
Therefore, the estimation method for the transient stability limit of the power transmission channel provided by the disclosure is used for estimating the transient stability limit power, the error is kept within 5%, the requirement of engineering application is met in precision, and the transient stability limit power can be used as a predicted value of the actual application of engineering technicians and applied to actual engineering.
Further, please refer to fig. 10, the present disclosure provides an estimation apparatus 30 for transient stability limit of a power transmission channel, which is applied to a power system 100, where the power system 100 includes a generator 11 and the power transmission channel, the estimation apparatus 30 includes a processing module 31 and a calculating module 32, and the processing module 31 is configured to obtain the transient stability limit power before and after the power transmission channel fails.
The calculation module 32 is configured to calculate a power angle when the generator 11 removes the fault according to the instability limit power before and after the fault of the power transmission channel, and calculate a coefficient K according to the power angle when the generator 11 removes the fault; and calculating transient stability limit power according to the static stability limit power of the generator 11 after the fault and the coefficient K.
It is clear to those skilled in the art that, for convenience and brevity of description, the specific working process of the estimation apparatus 30 for transient stability limit of power transmission channel described above may refer to the corresponding process in the foregoing method, and will not be described in detail herein.
In summary, the estimation method and device for transient stability limit of power transmission channel provided by the present disclosure are applied to a power system, the power system includes a generator and a power transmission channel, the power stability limit power before and after a fault of the power transmission channel is obtained, the power angle when the generator is subjected to fault removal is obtained by calculation according to the power stability limit power before and after the fault of the power transmission channel, the coefficient K is obtained by calculation according to the power angle when the generator is subjected to fault removal after the power angle when the generator is subjected to fault removal, the transient stability limit power after a change of an operation mode can be quickly obtained by one-time simulation after the coefficient K is obtained by calculation according to the power stability limit power after the fault of the power transmission channel and the coefficient K, repeated adjustment of voltage and reactive power is not required, and the calculation efficiency is greatly improved The method has the advantages of high stability, high measurement tolerance, high precision and convenient operation.
In addition, the transient stability limit power error estimated by the power transmission channel transient stability limit estimation method and device provided by the disclosure is kept within 5%, the requirements of engineering application are met in precision, and the transient stability limit power error can be used as a predicted value of the actual application of engineering technicians and applied to actual engineering.
In the several embodiments provided in the present disclosure, it should be understood that the disclosed apparatus and method may be implemented in other manners. The apparatus and method embodiments described above are illustrative only, as the flowcharts and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of apparatus, methods and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
In addition, functional modules in the embodiments of the present disclosure may be integrated together to form an independent part, or each module may exist separately, or two or more modules may be integrated to form an independent part.
The functions, if implemented in the form of software functional modules and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present disclosure may be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, an electronic device, or a network device) to execute all or part of the steps of the method according to the embodiments of the present disclosure. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes. It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The foregoing is illustrative of only alternative embodiments of the present disclosure and is not intended to limit the disclosure, which may be modified and varied by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present disclosure should be included in the protection scope of the present disclosure.

Claims (8)

1. A method of estimating sag limits of a power transmission path, applied to a power system including a generator and the power transmission path, the method comprising:
acquiring the static limiting power before and after the fault of the power transmission channel;
calculating a power angle when the generator removes the fault according to the static limiting power before and after the fault of the power transmission channel;
calculating a coefficient K according to a power angle when the generator cuts off the fault;
calculating transient stability limit power according to the static stability limit power after the power transmission channel fails and the coefficient K;
the step of calculating the power angle when the generator removes the fault according to the static limiting power before and after the fault of the power transmission channel comprises the following steps:
calculating an initial power angle delta of the generator according to the static limiting power before and after the transmission channel fault by the following formula0：
Figure FDA0002419756090000011
According to the initial power angle delta of the generator0The rated active power and the rotational inertia of the generator are calculated by the following formula to obtain the work of the generator when the fault is removedAngle deltac：
Figure FDA0002419756090000012
Wherein, PImaxFor the steady limit power before failure, PIImaxFor the steady limit power after a fault, PnFor rated active power of the generator, PTIs the mechanical power of prime mover under the same initial power flow, omega0To the initial generator speed, TjIs the moment of inertia, t is the fault time, during the calculation,
Figure FDA0002419756090000013
δ st is the complement angle of the power angle when the limit is reached;
and according to the power angle when the generator cuts off the fault, calculating the coefficient K by the following formula:
Figure FDA0002419756090000021
wherein, deltacFor removing the power angle when the fault occurs, pi-delta st is the power angle when the limit is reached, namely the stable limit of the static power angle after the fault, delta0Is the initial power angle of the generator.
2. The method according to claim 1, wherein the power system further includes a sending terminal unit and a receiving terminal unit, the sending terminal unit and the receiving terminal unit are connected via the power transmission channel, and the step of obtaining the before-failure and after-failure quiescent limit powers of the power transmission channel comprises:
according to a static power angle stabilization practical algorithm, gradually increasing the power of the sending end unit, and correspondingly reducing the power of the receiving end unit so as to respectively calculate and obtain static power angle stabilization limits before and after the transmission channel fault;
and respectively obtaining the maximum transmission power of the transmission channel or the section before and after the transmission channel fault according to the static power angle stability limits before and after the transmission channel fault, and taking the obtained maximum transmission power of the transmission channel or the section before and after the transmission channel fault as the static limit power before and after the fault.
3. The method of estimating the sag limit of a power transmission channel according to claim 1, wherein the coefficient K is obtained by:
calculating the unit acceleration area from the time of short circuit occurrence to the time of fault removal;
calculating the deceleration area of the unit from the fault removal moment to the limit removal angle moment;
based on the equal area principle, the unit acceleration area is equal to the unit deceleration area, and the coefficient K is obtained.
4. A method for estimating transient stability limit of a power transmission path according to claim 3, wherein said unit acceleration area is calculated by the following formula:
Sadding＝(δC-δ0)×PT＝(δC-δ0)×PIImax×sinδst；
Wherein, delta0For the initial power angle, delta, of the generator in normal operationcCutting-off the power angle, delta, of the generator in case of failurestTo achieve the complement of the power angle at the limit, PIImaxFor the steady limit power after a fault, PTRepresenting the mechanical power of the prime mover in the same initial power flow.
5. The method for estimating transient stability limit of a power transmission channel according to claim 4, wherein said unit deceleration area is calculated by the following formula:
Figure FDA0002419756090000031
wherein, deltacTo remove the power angle at fault, pi- δ st is the power angle at the limit, PIImaxFor calming after failureLimiting power, PTRepresenting the mechanical power of the prime mover, P, at the same initial tideEIs electromagnetic power.
6. The method for estimating transient stability limit of power transmission channel according to claim 5, wherein said unit acceleration area is equal to said unit deceleration area on the basis of equal area principle, and the step of obtaining the coefficient K comprises:
defining Δ E as deceleration energy-acceleration energy as deceleration area-acceleration area, and calculating:
ΔE＝Sreducing-SAdding＝PIImax×(cosδst+cosδC)-PIImax×sinδst×(π-δst-δC)-(δC-δ0)×PIImax×sinδst；
Simplifying to obtain:
ΔE＝PIImax×(cosδst+cosδC)-PIImax×sinδst×(π-δst+δ0)；
based on the equal area principle, the unit acceleration area is equal to the unit deceleration area, Δ E is obtained as 0, and the calculation result is:
Figure FDA0002419756090000041
introducing a coefficient K, making K equal to sin deltastObtaining:
Figure FDA0002419756090000042
wherein, deltacTo remove the power angle at fault, pi- δ st is the power angle at the limit, PIImaxFor the post-fault quiescent limit power, delta0The initial power angle of the generator in normal operation.
7. The method for estimating transient stability limit of power transmission channel according to claim 6, wherein said transient stability limit power is calculated by the following formula:
Pst＝K×PIImax；
wherein, PstFor temporarily stabilizing the limiting power, PIImaxThe power limit is the steady state power after the fault.
8. The estimation device for the transient stability limit of the power transmission channel is applied to a power system, the power system comprises a generator and the power transmission channel, the estimation device comprises a processing module and a calculation module, and the processing module is used for acquiring the transient stability limit power before and after the fault of the power transmission channel;
the calculation module is used for calculating a power angle when the generator removes the fault according to the static limiting power before and after the fault of the power transmission channel, and calculating a coefficient K according to the power angle when the generator removes the fault; calculating transient stability limit power according to the static stability limit power after the generator fails and the coefficient K;
the step that the calculation module is used for calculating the power angle when the generator removes the fault according to the static limiting power before and after the fault of the power transmission channel comprises the following steps:
calculating an initial power angle delta of the generator according to the static limiting power before and after the transmission channel fault by the following formula0：
Figure FDA0002419756090000051
According to the initial power angle delta of the generator0The rated active power and the rotational inertia of the generator are calculated by the following formula to obtain a power angle delta when the generator is subjected to fault removalc：
Figure FDA0002419756090000052
Wherein, PImaxFor the steady limit power before failure, PIImaxFor the steady limit power after a fault, PnIs the generator volumeConstant active power, PTIs the mechanical power of prime mover under the same initial power flow, omega0To the initial generator speed, TjIs the moment of inertia, t is the fault time, during the calculation,
Figure FDA0002419756090000053
δstthe angle is compensated for when the limit is reached;
the calculation module is used for calculating the coefficient K according to a power angle when the generator removes the fault by the following formula:
Figure FDA0002419756090000054
wherein, deltacFor removing the power angle when the fault occurs, pi-delta st is the power angle when the limit is reached, namely the stable limit of the static power angle after the fault, delta0Is the initial power angle of the generator.
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