CN109546650B - Estimation method and device for transient stability limit of transmission channel - Google Patents

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

Estimation method and device for transient stability limit of transmission channel

technical field

The present disclosure relates to the field of power systems, and in particular, to a method and device for estimating the temporary stability limit of a power transmission channel.

Background technique

With the increase of electricity load, the regional structure of the power grid becomes more complex, and the power exchange capacity between regions has a great impact on the security and stability of the power grid. Transmission capacity also varies with mode and operating conditions. Therefore, it is necessary to accurately and quickly determine the power transmission capability of the tie line, so that it can meet the power load demand to the greatest extent under the premise of satisfying safety and reliability, so as to improve the rapidity of decision-making.

In engineering, the temporary stability limit power is calculated by the time domain simulation program, and the output of the generator set at the sending and receiving ends needs to be changed during the power flow, and the stable limit value is approached through continuous simulation. However, if the power flow is heavy and the system does not converge due to serious voltage drop, the staff needs to adjust the voltage and reactive power to make the power flow calculation reconverge, which is complicated and inefficient.

SUMMARY OF THE INVENTION

In view of this, the present disclosure provides a method and device for estimating the transient stability limit of a power transmission channel.

The present disclosure provides a method for estimating the temporary stability limit of a power transmission channel, which is applied to a power system, where the power system includes a generator and a power transmission channel, and the method includes:

Obtain the static and stable limit power of the transmission channel before and after the fault.

The power angle of the generator when the fault is removed is calculated according to the static and stable limit power of the power transmission channel before and after the fault.

The coefficient K is calculated according to the power angle of the generator when the fault is removed.

The transient stability limit power is calculated according to the static stability limit power after the failure of the transmission channel and the coefficient K.

Further, the power system further includes a sending-end unit and a receiving-end unit, the sending-end unit and the receiving-end unit are connected through the power transmission channel, and the step of obtaining the static stability limit power before and after the fault of the power transmission channel include:

According to the static power angle stabilization practical algorithm, the power of the sending-end unit is gradually increased, and the power of the receiving-end unit is correspondingly reduced, so as to calculate the static power angle stability limit of the transmission channel before and after the fault.

Obtain the maximum transmission power of the transmission channel or section of the transmission channel before and after the fault according to the static power angle stability limits of the transmission channel before and after the fault, respectively, and use the obtained pre-fault and post-fault of the transmission channel respectively. The maximum transmission power of the transmission channel or section is taken as the static and stable 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 static and stable limit power of the transmission channel before and after the fault includes:

According to the static and stable limit power of the transmission channel before and after the fault, the initial power angle δ ₀ of the generator is calculated by the following formula:

According to the initial power angle δ ₀ of the generator, the rated active power of the generator and the moment of inertia, the power angle δ _c of the generator when the fault is removed is calculated by the following formula:

Among them, P _Imax is the static stability limit power before the fault, P _IImax is the static stability limit power after the fault, P _n is the rated active power of the generator, P _T is the mechanical power of the prime mover under the same initial power flow, ω ₀ is the initial generator speed, T _j is the moment of inertia, t is the fault time, in the calculation process,

Further, according to the power angle of the generator when the fault is removed, the coefficient K is calculated by the following formula:

Among them, δ _c is the power angle when the fault is removed, π-δst is the power angle when the limit is reached, that is, the static power angle stability limit after the fault, and δ ₀ is the initial power angle of the generator.

Further, the coefficient K is obtained through the following steps:

Calculate the acceleration area of the unit when the short circuit occurs to the moment when the fault is removed.

Calculate the deceleration area of the unit from the time of fault removal to the time of the limit removal angle.

Based on the principle of equal area, the acceleration area of the unit is equal to the deceleration area of the unit, and the coefficient K is obtained.

Further, the acceleration area of the unit is calculated by the following formula:

S _plus =(δ _C −δ ₀ )×P _T =(δ _C −δ ₀ )×P _IImax ×sinδ _st ;

Among them, δ ₀ is the initial power angle of the generator during normal operation, δ _c is the power angle of the generator when the fault is removed, π-δst is the power angle when the limit is reached, P _IImax is the static stability limit power after the fault, P _T Represents the mechanical power of the prime mover under the same initial power flow.

Further, the deceleration area of the unit is calculated by the following formula:

Among them, δ _c is the power angle when the fault is removed, π-δst is the power angle when the limit is reached, P _IImax is the static and stable limit power after the fault, P _T is the mechanical power of the prime mover under the same initial power flow, and P _E is the electromagnetic power. .

Further, based on the principle of equal area, the acceleration area of the unit is equal to the deceleration area of the unit, and the step of obtaining the coefficient K includes:

Definition ΔE = deceleration energy - acceleration energy = deceleration area - acceleration area, the calculation can be obtained:

ΔE=S _minus -S _plus =P _IImax ×(cosδ _st +cosδ _C )-P _IImax ×sinδ _st ×(π-δ _st −δ _C )-(δ _C −δ ₀ )×P _IImax ×sinδ _st ;

Simplified to:

ΔE=P _IImax ×(cosδ _st +cosδ _C )-P _IImax ×sinδ _st ×(π-δ _st +δ ₀ );

Based on the principle of equal area, the acceleration area of the unit is equal to the deceleration area of the unit, and ΔE=0 is obtained, and the calculation is as follows:

Introduce the coefficient K, let K=sinδ _st , get:

Among them, δ _c is the power angle when the fault is removed, π-δ _st is the power angle when the limit is reached, P _IImax is the static and stable limit power after the fault, and δ ₀ is the initial power angle of the generator during normal operation.

Further, the temporary stability limit power is calculated by the following formula:

P _st =K×P _IImax ;

Among them, P _st is the transient stability limit power, and P _IImax is the static stability limit power after the fault.

The present disclosure provides an estimation device for the temporary stability limit of a power transmission channel, which is applied to a power system. The power system includes a generator and a power transmission channel. The estimation device includes a processing module and a calculation module, and the processing module is used to obtain the The static limit power before and after the fault of the transmission channel.

The calculation module is used to calculate the power angle of the generator when the fault is removed according to the static and stable limit power of the transmission channel before and after the fault, and to calculate the coefficient K according to the power angle of the generator when the fault is removed; The static stability limit power after the generator failure and the coefficient K are used to calculate the temporary stability limit power.

The method and device for estimating the transient stability limit of a power transmission channel provided by the present disclosure are applied to a power system including a generator and a power transmission channel. The static and stable limit power before and after the fault is calculated to obtain the power angle of the generator when the fault is removed. After the power angle of the generator when the fault is removed, the coefficient K is calculated according to the power angle of the generator when the fault is removed. After K, the temporary stable limit power of the transmission channel is calculated according to the static and stable limit power after the failure of the transmission channel and the coefficient K, and there is no need to repeatedly adjust the voltage and reactive power. The operation is convenient and the calculation efficiency is greatly improved.

In order to make the above-mentioned objects, features and advantages of the present disclosure more obvious and easy to understand, the preferred embodiments are exemplified below, and are described in detail as follows in conjunction with the accompanying drawings.

Description of drawings

In order to illustrate the technical solutions of the present disclosure more clearly, the accompanying drawings required in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present disclosure, and therefore should not be It is regarded as a limitation of the scope, and for those of ordinary skill in the art, other related drawings can also be obtained according to these drawings without any creative effort.

FIG. 1 is a schematic block diagram of a power system provided by the present disclosure.

FIG. 2 is a schematic flowchart of a method for estimating the temporary stability limit of a power transmission channel provided by the present disclosure.

FIG. 3 is another schematic flowchart of the method for estimating the 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 static stability curve of a power transmission channel in the normal mode of the present disclosure.

FIG. 6 is a static stability curve of a power transmission channel after a fault of the present disclosure.

FIG. 7 is a generator power angle curve after a fault of the present disclosure.

FIG. 8 is a power angle curve of the generator after transient stabilization of the present disclosure.

FIG. 9 is an active power curve of a power transmission channel after transient stabilization of the present disclosure.

FIG. 10 is a schematic block diagram of an apparatus for estimating the transient stability limit of a power transmission channel provided by the present disclosure.

Icons: 100-power system; 10-sending unit; 11-generator; 20-receiving unit; 30-estimating device; 31-processing module; 32-calculating module.

Detailed ways

The technical solutions in the present disclosure will be clearly and completely described below with reference to the accompanying drawings in the present disclosure. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, but not all of the embodiments. The components of the present disclosure generally described and illustrated in the drawings herein may be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of the disclosure provided in the accompanying drawings is not intended to limit the scope of the disclosure as claimed, but is merely representative of selected embodiments of the disclosure. Based on the embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present disclosure.

It should be noted that like numerals and letters refer to like items in the following figures, so once an item is defined in one figure, it does not require further definition and explanation in subsequent figures.

With the increase of electricity load, the regional structure of the power grid becomes more complex, and the power exchange capacity between regions has a great impact on the security and stability of the power grid. Transmission capacity also varies with mode and operating conditions. Therefore, it is necessary to accurately and quickly determine the power transmission capability of the tie line, so that it can meet the power load demand to the greatest extent under the premise of satisfying safety and reliability, so as to improve the rapidity of decision-making.

In theory, the direct method is generally used to analyze the transient stability limit. The direct method has a good prospect in the online application of transient safety analysis due to its fast calculation speed, but it still cannot get rid of the conservatism and model of the direct method. The limitation of the defect, in short, the use of the direct method for transient stability limit analysis is restricted by the corresponding calculation accuracy and speed of the direct method. In engineering, the temporary stability limit power is calculated by the time domain simulation program, and the output of the generator set at the sending and receiving ends needs to be changed during the power flow, and the stable limit value is approached through continuous simulation. However, if the power flow is heavy and the system does not converge due to serious voltage drop, the mode personnel need to adjust the voltage and reactive power to re-converge the power flow calculation. This process of adjusting the power flow is time-consuming, complicated to operate, and inefficient.

Based on the above research, the present disclosure provides a method and device for estimating the transient stability limit of a power transmission channel to improve the above problems.

Please refer to FIG. 1 , the method for estimating the temporary stability limit of a transmission channel provided by the present disclosure is applied to the power system 100 shown in FIG. 1 . The sending-end unit 10 and the receiving-end unit 20 are connected by a power transmission channel, so that the sending-end unit 10 transmits electric power to the receiving-end unit 20 , and the sending-end unit 10 includes a generator 11 .

Please refer to FIG. 2 , which is a schematic flowchart of a method for estimating the transient stability limit of a power transmission channel provided by the present disclosure. The flow chart shown in FIG. 2 will be described in detail below.

Step S10: Obtain the static and stable limit power of the power transmission channel before and after the fault.

The purpose of the calculation and analysis of the static stability of the power system 100 is to apply the corresponding criteria to determine the static stability of the power system 100 loaded operating points one by one, to obtain the static transmission power limit and static stability reserve in a given mode, and to verify the given operation. Whether the static stability reserve of the method meets the requirements. Therefore, it is necessary to carry out static stability analysis for large power transmission lines, weak grid tie lines, large receiving end systems, and weak sections in the network.

Further, please refer to FIG. 3 , the steps of acquiring the static and stable limit power of the power transmission channel before and after the fault include steps S11 to S12 .

Step S12: According to the static power angle stabilization practical algorithm, gradually increase the power of the sending-end unit 10, and correspondingly reduce the power of the receiving-end unit 20, so as to calculate the static power angle stability before and after the failure of the transmission channel respectively. limit.

Step S12: Obtain the maximum transmission power of the transmission channel or section of the transmission channel before and after the failure according to the static power angle stability limits of the transmission channel before the failure and after the failure, respectively. and the maximum transmission power of the transmission channel or section after the fault as the static and stable limit power before and after the fault.

Among them, there are generally two methods for calculating the static power angle stability, which are the characteristic root discrimination method and the static power angle stability practical algorithm.

The general process of the characteristic root discriminant method is: calculate the steady state value of the power flow distribution and state quantity under a given operation mode; linearize the equation describing the transient process near the steady state value to form a characteristic matrix, and according to its characteristic value to judge the static stability of the system. If there is no positive real eigenvalue, the static power angle is determined to be stable.

The practical algorithm for static power angle stabilization is to use a stable calculation program to gradually increase the power of the sending-end unit 10 and correspondingly reduce the power of the receiving-end unit 20 until aperiodic distortion occurs in the system. At this time, the corresponding power angle is static. The stability limit of the power angle. That is, the static power angle stability limit. At the same time, the maximum transmission power of the transmission channel or section is obtained according to the static power angle stability limit, and this power is regarded as the static stability limit power.

Optionally, in the calculation process of the static stability limit power, the present disclosure selects a static power angle stability practical algorithm, and uses the obtained static stability limit power as an effective evaluation index for judging the stability of the power system 100 .

Static Stability Limit Power - Characterizes the maximum transmission capability of an AC cross-section (channel).

Among them, P _max is the static and stable limit power, E _q is the internal potential of the generator 11, U is the infinite node voltage, δ is the rotor angle of the generator 11, X _d is the generator 11 synchronous reactance, channel line equivalent reactance and The sum of the equivalent reactances of the transformers.

In the calculation process, the frequency and voltage of the system should be kept within the normal range as far as possible. Therefore, the speed regulation system and excitation system in the sending-end unit 10 and the receiving-end unit 20 should be considered to ensure the basic balance of increase and decrease power. At the same time, it should be noted that the increase or decrease scheme of power should conform to the actual power flow, and different schemes may obtain different static stability limits. Because in a multi-machine system, from the normal operation mode to the stable limit operation, different transition schemes may appear, and different operation schemes may lead to different stability limits, and the adjustment methods of power generation or load in each area may be different. As a result, the static stable power limit of the obtained tie line may differ by about 10%-20%. When the unit with increased output is located at the near end of the tie line, the static stability limit may be increased due to the increase of the voltage and reactive power support; when the unit with increased output is located at the far end of the tie line, because the power has to be transmitted over a long distance, it will Causes the reduction of the voltage along the line, thereby reducing the static stability limit. Similarly, when the power reducing unit is located at the near or far end of the tie line, it will also have the same impact on the static stability limit.

After obtaining the static power angle stability limit and static stability limit power before and after the fault according to the obtained static power angle stability practical algorithm, step S20 is entered.

Step S20: Calculate the power angle of the generator 11 when the fault is removed according to the static and stable limit power of the power transmission channel before and after the fault.

The calculation of the power angle when the generator 11 removes the fault according to the static and stable limit power of the power transmission channel before and after the fault can be obtained through the process 1 and the process 2.

Process 1: Calculate the initial power angle δ ₀ of the generator 11 by the following formula according to the static and stable limit power of the transmission channel before and after the fault:

Process 2: According to the initial power angle δ ₀ of the generator 11 , the rated active power of the generator 11 and the moment of inertia, the power angle δ _c of the generator 11 when the fault is removed is calculated by the following formula:

t为故障时间。Among them, P _Imax is the static stability limit power before the fault, P _IImax is the static stability limit power after the fault, P _n is the rated active power of the generator 11, P _T is the mechanical power of the prime mover under the same initial power flow, ω ₀ is Initial generator 11 speed, T _j is the moment of inertia, in the calculation process,

t is the failure time.

Step S30 is entered after the power angle of the generator 11 when the fault is removed is obtained.

Step S30: Calculate the coefficient K according to the power angle of the generator 11 when the fault is removed.

Wherein, according to the power angle of the generator 11 when the fault is removed, the coefficient K is calculated by the following formula:

Among them, δ _c is the power angle when the fault is removed, π-δst is the power angle when the limit is reached, that is, the static power angle stability limit after the fault, and δ ₀ is the initial power angle of the generator 11 .

After the coefficient K is obtained, go to step S40.

Step S40: Calculate the temporary stability limit power according to the static stability limit power after the failure of the power transmission channel and the coefficient K.

Among them, 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 a large disturbance. The purpose of transient stability calculation and analysis is to verify the transient stability of the system under the specified operation mode and fault state, to study the control strategy to ensure the safety and stability of the power grid, and to provide protection for relay protection and automatic devices as well as various security systems. Stabilization measures put forward corresponding requirements. During normal operation, the power system 100 can transition from the original operating state (balance point) to a new operating state after being subjected to a large disturbance, and operate stably in the new operating state. If the power angle can be stabilized at a certain value after oscillation, it indicates that the synchronous operation between the generators 11 has resumed, and the system has transient stability. Therefore, the time-varying characteristics of the power angle after a large disturbance is used as the transient stability criterion.

In the present disclosure, the temporary stability limit power is calculated by the following formula:

P _st =K×P _IImax ;

Among them, P _st is the transient stability limit power, and P _IImax is the static stability limit power after the fault. In the present disclosure, after the value of the coefficient K is obtained, the temporary stability limit power can be quickly estimated according to the static stability limit power after the fault and the coefficient K, which greatly improves the calculation efficiency.

Further, please refer to FIG. 4 . FIG. 4 is a power angle characteristic curve of a single-machine infinite system constructed by the present disclosure, and the coefficient K is obtained through process 3 to process 5 .

Process 3: Calculate the acceleration area of the unit when the short circuit occurs to the moment when the fault is removed.

Wherein, the unit is the sending end unit 10, and the acceleration area of the unit is calculated by the following formula:

S _plus =(δ _C −δ ₀ )×P _T =(δ _C −δ ₀ )×P _IImax ×sinδ _st ;

Among them, δ ₀ is the initial power angle of the generator 11 during normal operation, δ _c is the power angle of the generator 11 when the fault is removed, π-δst is the power angle when the limit is reached, P _IImax is the static stability limit power after the fault, P _T represents the mechanical power of the prime mover under the same initial power flow.

Process 4: Calculate the deceleration area of the unit from the time of fault removal to the time of limit removal angle.

Wherein, further, the deceleration area of the unit is calculated by the following formula:

Among them, δ _c is the power angle when the fault is removed, π-δst is the power angle when the limit is reached, P _IImax is the static and stable limit power after the fault, P _T is the mechanical power of the prime mover under the same initial power flow, and P _E is the electromagnetic power. .

Process 5: Based on the principle of equal area, the acceleration area of the unit is equal to the deceleration area of the unit, and the coefficient K is obtained.

Among them, the definition ΔE = deceleration energy - acceleration energy = deceleration area - acceleration area, the calculation can be obtained:

ΔE=S _minus -S _plus =P _IImax ×(cosδ _st +cosδ _C )-P _IImax ×sinδ _st ×(π-δ _st −δ _C )-(δ _C −δ ₀ )×P _IImax ×sinδ _st ;

Simplified to:

ΔE=P _IImax ×(cosδ _st +cosδ _C )-P _IImax ×sinδ _st ×(π-δ _st +δ ₀ );

Based on the principle of equal area, the acceleration area of the unit is equal to the deceleration area of the unit, and ΔE=0 is obtained, and the calculation is as follows:

Introduce the coefficient K, let K=sinδ _st , get:

Among them, δ _c is the power angle when the fault is removed, π-δ _st is the power angle when the limit is reached, P _IImax is the static and stable limit power after the fault, and δ ₀ is the initial power angle of the generator 11 during normal operation.

After the coefficient K is derived from the above process, when the subsequent transmission channel fails and the temporary stability limit power of the transmission channel is calculated, it is only necessary to obtain the static stability limit power and coefficient K before and after the failure through one simulation calculation, and then According to the static stability limit power and coefficient K after the fault, the temporary stability limit power is quickly estimated, which greatly improves the calculation efficiency.

The method for estimating the temporary stability limit of a power transmission channel provided by the present disclosure will be verified below with specific examples. The specific process is as follows.

(1) Use PSD-BPA electromechanical transient simulation software to build a single-machine infinite system, and calculate the static stability limit of the transmission channel before and after the fault. Please refer to Figure 5. Figure 5 is the static stability curve of the transmission channel in the normal mode. The static stability limit P _Imax = 1651MW, set the line XL head end Sanyong N-1 fault, please refer to Figure 6, Figure 6 is the static stability curve of the transmission channel after the fault, the static stability limit after the fault is P _IImax =1268MW.

(2) Determine the rated active power of the generator 11, the power angle when the fault is removed, and the moment of inertia. Please refer to FIG. 7. FIG. 7 is the power angle curve of the unit after the fault, wherein the rated active power of the generator 11 is P _n =1000MW, the inertia time constant of the generator 11 is T _j =10s, and the power angle of the generator 11 when the fault is removed δ ₀ = 39°

(3) Calculate the actual transient stability limit power, that is, the transient stability limit power. Please refer to Fig. 8 and Fig. 9 together, Fig. 8 is the power angle curve of the unit after transient stabilization, and Fig. 9 is the active power curve of the transmission channel after transient stabilization. Calculated by PSD-BPA, the temporary stable limit power under XL Sanyong N-1 fault is 1046MW.

计算得到K系数＝0.826，由P_st＝K×P_IImax快速估算暂稳极限功率P_st＝1047MW。(4) The temporary stability limit power is estimated by using the estimation method of the transmission channel temporary stability limit provided by the present disclosure. The rated active power of the generator 11 is P _n =1000MW, the inertia time constant of the generator 11 is T _j =10s, and the power angle δ ₀ =39° when the generator 11 removes the fault. In the normal mode, the static stability limit power P _Imax = 1651MW, set the line XL head end Sanyong N-1 fault, the static stability limit power P _IImax = 1268MW after the fault. Depend on

The K coefficient is calculated to be 0.826, and the temporary stability limit power P _st =1047MW is quickly estimated by P _st =K×P _IImax .

(5) Compare the transient stability limit power under XL Sanyong N-1 fault calculated by PSD-BPA with the transient stability limit power estimated by the transmission channel transient stability limit estimation method provided in the present disclosure. Using PSD-BPA simulation to calculate the temporary stability limit power under XL Sanyong N-1 fault is P _st =1046MW, the present disclosure estimates and obtains the temporary stability limit power P _st =1047MW, so the calculation error is 0.09%.

In addition, the PSD-BPA electromechanical transient simulation software is used to calculate the temporary stability limit power sent by the Toketuo Power Plant, and the correctness of the estimation method of the transmission channel temporary stability limit provided by the present disclosure is verified. The rated active power of the Tuoketuo unit is P _n =4800MW, the inertia time constant T _j =9.26s, and the power angle δ ₀ =48° when the generator 11 removes the fault. In the normal mode, the static and stable limit power is P _Imax = 6780MW, and the Sanyong N-1 fault on the Tuoketuo side of the Toketo-Hunyuan line is set, and the static and stable limit power after the fault is P _IImax = 6185MW. Calculated K coefficient = 0.82, and obtained the temporary stability limit power P _st = 5071MW by quick estimation. Calculated by PSD-BPA, the temporary stable limit power under XL Sanyong N-1 fault is 5312MW, so the calculation error is 4.5%.

Therefore, using the estimation method for the temporary stability limit of the transmission channel provided by the present disclosure to estimate the temporary stability limit power, the error is kept within 5%, and the accuracy meets the requirements of engineering applications, which can be used as the estimated value for practical application by engineers and technicians. used in practical engineering.

Further, please refer to FIG. 10 , the present disclosure provides an estimation device 30 for the temporary stability limit of a power transmission channel, which is applied to a power system 100 . The power system 100 includes a generator 11 and a power transmission channel, and the estimation device 30 includes a processing The module 31 and the calculation module 32, the processing module 31 is used to obtain the static and stable limit power of the power transmission channel before and after the fault.

The calculation module 32 is used to calculate the power angle of the generator 11 when the fault is removed according to the static and stable limit power of the transmission channel before and after the fault, and to calculate the coefficient K according to the power angle of the generator 11 when the fault is removed. ; and calculate the temporary stability limit power according to the static stability limit power after the generator 11 fails and the coefficient K.

Those skilled in the art can clearly understand that, for the convenience and brevity of the description, the specific working process of the device 30 for estimating the temporary stability limit of the power transmission channel described above can be referred to the corresponding process in the aforementioned method, which is not repeated here. of elaboration.

To sum up, the method and device for estimating the transient stability limit of a transmission channel provided by the present disclosure are applied to a power system including a generator and a transmission channel. According to the static and stable limit power of the transmission channel before and after the fault, the power angle of the generator when the fault is removed is obtained. After the power angle of the generator when the fault is removed, the coefficient K is calculated according to the power angle of the generator when the fault is removed. After the coefficient K is obtained, the transient stability limit power of the transmission channel can be calculated according to the static stability limit power after the transmission channel fault and the coefficient K, and the transient stability limit after the operation mode change can be quickly calculated by only one simulation. power, no need to repeatedly adjust the voltage and reactive power, which greatly improves the calculation efficiency, and the method and device for estimating the temporary stability limit of the transmission channel provided by the present disclosure have the same model applicability as the time domain simulation method and the direct method. Stability margin quantification, high precision and convenient operation.

In addition, the error of the temporary stability limit power estimated by the method and device for estimating the temporary stability limit of the transmission channel provided by the present disclosure is kept within 5%, and the accuracy meets the requirements of engineering applications, which can be used as practical applications by engineers and technicians. The estimated value is used in practical engineering.

In the several embodiments provided in the present disclosure, it should be understood that the disclosed apparatus and method may also be implemented in other manners. The apparatus and method embodiments described above are merely illustrative, for example, the flowcharts and block diagrams in the accompanying drawings illustrate the architecture, possible implementations of apparatus, methods and computer program products according to various embodiments of the present disclosure, function and operation. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code that contains one or more functions for implementing the specified logical function(s) executable instructions. 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 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 is also noted that each block of the block diagrams and/or flowchart illustrations, and combinations of blocks in the block diagrams and/or flowchart illustrations, can be implemented in dedicated hardware-based systems that perform the specified functions or actions , or can be implemented in a combination of dedicated hardware and computer instructions.

In addition, each functional module in each embodiment of the present disclosure may be integrated together to form an independent part, or each module may exist alone, or two or more modules may be integrated to form an independent part.

If the functions are implemented in the form of software function modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on such understanding, the technical solutions of the present disclosure can be embodied in the form of software products in essence, or the parts that contribute to the prior art or the parts of the technical solutions. The computer software products are stored in a storage medium, including Several instructions are used to cause a computer device (which may be a personal computer, an electronic device, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of the present disclosure. The aforementioned storage medium includes: U disk, mobile hard disk, Read-Only Memory (ROM, Read-Only Memory), Random Access Memory (RAM, Random Access Memory), magnetic disk or optical disk and other media that can store program codes . It should be noted that, herein, the terms "comprising", "comprising" or any other variation thereof are intended to encompass non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements, It also includes other elements not expressly listed or inherent to such a process, method, article or apparatus. Without further limitation, an element qualified by the phrase "comprising a..." does not preclude the presence of additional identical elements in a process, method, article or apparatus that includes the element.

The above descriptions are only optional embodiments of the present disclosure, and are not intended to limit the present disclosure. For those skilled in the art, the present disclosure may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included within the protection scope of the present disclosure.

Claims (8)

1. A method for estimating the temporary stability limit of a power transmission channel, characterized in that, applied to a power system, the power system comprising a generator and a power transmission channel, the method comprising: Obtain the static and stable limit power of the transmission channel before and after the fault; Calculate the power angle of the generator when the fault is removed according to the static and stable limit power of the power transmission channel before and after the fault; Calculate the coefficient K according to the power angle of the generator when the fault is removed; Calculate the temporary stability limit power according to the static stability limit power after the failure of the transmission channel and the coefficient K; The step of calculating the power angle of the generator when the fault is removed according to the static and stable limit power of the transmission channel before and after the fault includes: According to the static and stable limit power of the transmission channel before and after the fault, the initial power angle δ ₀ of the generator is calculated by the following formula:

According to the initial power angle δ ₀ of the generator, the rated active power of the generator and the moment of inertia, the power angle δ _c of the generator when the fault is removed is calculated by the following formula:

Among them, P _Imax is the static stability limit power before the fault, P _IImax is the static stability limit power after the fault, P _n is the rated active power of the generator, P _T is the mechanical power of the prime mover under the same initial power flow, ω ₀ is the initial generator speed, T _j is the moment of inertia, t is the fault time, in the calculation process,

δst is the supplementary angle of the power angle when the limit is reached; According to the power angle of the generator when the fault is removed, the coefficient K is calculated by the following formula:

Among them, δ _c is the power angle when the fault is removed, π-δst is the power angle when the limit is reached, that is, the static power angle stability limit after the fault, and δ ₀ is the initial power angle of the generator. 2 . The method for estimating the temporary stability limit of a transmission channel according to claim 1 , wherein the power system further comprises a sending-end unit and a receiving-end unit, and the sending-end unit and the receiving-end unit pass through the transmission channel. 3 . The steps of obtaining the static and stable limit power of the transmission channel before and after the fault include: According to the static power angle stabilization practical algorithm, gradually increase the power of the sending-end unit, and correspondingly reduce the power of the receiving-end unit, so as to calculate the static power angle stability limit of the transmission channel before and after the fault respectively; Obtain the maximum transmission power of the transmission channel or section of the transmission channel before and after the fault according to the static power angle stability limits of the transmission channel before and after the fault, respectively, and use the obtained pre-fault and post-fault of the transmission channel respectively. The maximum transmission power of the transmission channel or section is taken as the static and stable limit power before and after the fault. 3. The method for estimating the temporary stability limit of a power transmission channel according to claim 1, wherein the coefficient K is obtained by the following steps: Calculate the acceleration area of the unit when the short circuit occurs to the time when the fault is removed; Calculate the deceleration area of the unit from the moment of fault removal to the moment of limit removal angle; Based on the principle of equal area, the acceleration area of the unit is equal to the deceleration area of the unit, and the coefficient K is obtained. 4. The method for estimating the temporary stability limit of a power transmission channel according to claim 3, wherein the acceleration area of the unit is calculated by the following formula: S _plus =(δ _C −δ ₀ )×P _T =(δ _C −δ ₀ )×P _IImax ×sinδ _st ; Among them, δ ₀ is the initial power angle of the generator during normal operation, δ _c is the power angle of the generator when the fault is removed, δ _st is the supplementary angle of the power angle when the limit is reached, P _IImax is the static stability limit power after the fault, P _T represents the mechanical power of the prime mover under the same initial power flow. 5. The method for estimating the temporary stability limit of a power transmission channel according to claim 4, wherein the unit deceleration area is calculated by the following formula:

Among them, δ _c is the power angle when the fault is removed, π-δst is the power angle when the limit is reached, P _IImax is the static and stable limit power after the fault, P _T is the mechanical power of the prime mover under the same initial power flow, and P _E is the electromagnetic power. . 6. The method for estimating the temporary stability limit of a power transmission channel according to claim 5, wherein, based on the principle of equal area, the acceleration area of the unit is equal to the deceleration area of the unit, and the step of obtaining the coefficient K comprises: Definition ΔE = deceleration energy - acceleration energy = deceleration area - acceleration area, the calculation can be obtained: ΔE=S _minus -S _plus =P _IImax ×(cosδ _st +cosδ _C )-P _IImax ×sinδ _st ×(π-δ _st −δ _C )-(δ _C −δ ₀ )×P _IImax ×sinδ _st ; Simplified to: ΔE=P _IImax ×(cosδ _st +cosδ _C )-P _IImax ×sinδ _st ×(π-δ _st +δ ₀ ); Based on the principle of equal area, the acceleration area of the unit is equal to the deceleration area of the unit, and ΔE=0 is obtained, and the calculation is as follows:

Introduce the coefficient K, let K=sinδ _st , get:

Among them, δ _c is the power angle when the fault is removed, π-δst is the power angle when the limit is reached, P _IImax is the static and stable limit power after the fault, and δ ₀ is the initial power angle of the generator during normal operation. 7. The method for estimating the temporary stability limit of a power transmission channel according to claim 6, wherein the temporary stability limit power is calculated by the following formula: P _st =K×P _IImax ; Among them, P _st is the transient stability limit power, and P _IImax is the static stability limit power after the fault. 8. An estimation device for the temporary stability limit of a power transmission channel, characterized in that it is applied to a power system, the power system includes a generator and a power transmission channel, the estimation device includes a processing module and a calculation module, the processing module is used for Obtain the static and stable limit power of the transmission channel before and after the fault; The calculation module is used to calculate the power angle of the generator when the fault is removed according to the static and stable limit power of the transmission channel before and after the fault, and to calculate the coefficient K according to the power angle of the generator when the fault is removed; The static stability limit power after the generator failure and the coefficient K are used to calculate the temporary stability limit power; The step of the calculation module for calculating the power angle of the generator when the fault is removed according to the static and stable limit power of the transmission channel before and after the fault includes: According to the static and stable limit power of the transmission channel before and after the fault, the initial power angle δ ₀ of the generator is calculated by the following formula:

According to the initial power angle δ ₀ of the generator, the rated active power of the generator and the moment of inertia, the power angle δ _c of the generator when the fault is removed is calculated by the following formula:

Among them, P _Imax is the static stability limit power before the fault, P _IImax is the static stability limit power after the fault, P _n is the rated active power of the generator, P _T is the mechanical power of the prime mover under the same initial power flow, ω ₀ is the initial generator speed, T _j is the moment of inertia, t is the fault time, in the calculation process,

δ _st is the supplementary angle of the power angle when the limit is reached; The calculation module is configured to calculate the coefficient K by the following formula according to the power angle when the generator removes the fault:

Among them, δ _c is the power angle when the fault is removed, π-δst is the power angle when the limit is reached, that is, the static power angle stability limit after the fault, and δ ₀ is the initial power angle of the generator.

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