WO2014107997A1

WO2014107997A1 - Method for real-time discrimination of transient power angle destabilization based on actually-measured response information

Info

Publication number: WO2014107997A1
Application number: PCT/CN2013/087999
Authority: WO
Inventors: 汤涌; 吴为; 孙华东; 何剑
Original assignee: 国家电网公司; 中国电力科学研究院
Priority date: 2013-01-09
Filing date: 2013-11-28
Publication date: 2014-07-17
Also published as: CN103094901B; CN103094901A

Abstract

A method for real-time discrimination of transient power angle destabilization based on actually-measured response information for judging transient power angle stability after a multi-machine interconnected electric power system has failed, comprising: determining an oscillation tie section of a multi-machine interconnected electric power system; acquiring dynamic feature information about the tie section; according to the dynamic feature information about the tie section, when the three conditions are determined to be satisfied at the same time that the active power of a tie line on the oscillation tie section at the i^th moment after a failure is smaller than the active power at the (i-T)^th moment after the failure and the bus voltage phase angle difference thereof is greater than the bus voltage phase angle difference at the (i-T)^th moment after the failure, and the frequency of a sending-end bus of the tie line on the oscillation tie section at the i^th moment after the failure is greater than the frequency at the (i-T)^th moment after the failure, determining that transient power angle destabilization will occur in the multi-machine interconnected electric power system at the i^th moment after the failure, otherwise, determining that transient power angle destabilization will not occur in the multi-machine interconnected electric power system at the i^th moment after the failure, taking full consideration of the nonlinear characteristic of the system, and being capable of accurately analyzing the transient power angle stability after the system is disturbed.

Description

Method for real-time discrimination of transient power angle instability based on measured response information

Technical field

The invention relates to the field of power systems, and particularly relates to a method for real-time discrimination of transient power angle instability based on measured response information. Background technique

With the construction of UHV large power grids, the introduction of new energy power generation and new power electronic equipment, the scale of the power grid is expanding, the complexity is increasing, and the dynamic characteristics of the system are more complicated. The interconnection of regional power systems improves the ability to optimize the allocation of energy in a large range. At the same time, it may also cause local faults in the region to spread to a wider extent through the inter-regional communication sections, making the safe and stable operation of large power grids more challenging.

For multi-machine interconnected large-scale power systems, the transient stability problem is the focus of attention. With the increasing scale of networking, the transient stability analysis and control mode of "offline decision, online matching" and "online decision making, real-time matching" can not meet the requirements of safe and stable operation of large power grids, and gradually move to "real-time decision-making, real-time control". "The direction of development. In order to meet the requirements of real-time analysis, the existing transient stability analysis methods mainly focus on real-time/super real-time time domain simulation and direct method research. The study of these methods has greatly improved the speed of transient stability analysis. Real-time transient stability analysis and control based on measured response data is essentially a "response control" model based on measured data, which can meet the requirements of "real-time decision-making, real-time control". The key lies in the study of fast transient stability criterion. . At present, the research on the fast transient stability criterion mainly focuses on using the wide-area information to study the instability criterion when the trajectory encounters the dynamic saddle point according to the slope and power when the trajectory traverses the dynamic saddle point. Based on the extended phase plane of the kinetic energy-power angle curve of the generator, the transient stability index criterion of the generator after the fault is maintained, the first pendulum is unstable and the coasting is out of step. Based on the trajectory analysis method, starting from the energy function, the multi-pendulum stability identification criterion is studied. Based on the trajectory geometry, the transient instability criterion for multi-machine systems is studied. The study of these methods enriches the research theory of rapid stability criteria, but there are problems such as slow calculation speed and inaccurate recognition. Summary of the invention

The present invention relates to a method for real-time discrimination of transient power angle instability based on measured response information, and for determining transient power angle stability of a multi-machine interconnected power system after a fault, the method comprising:

Step S1, determining, by the information measured by the WAMS measurement system, an oscillating contact section of the multi-machine interconnected power system after the fault;

Step S2, periodically acquiring, by the WAMS measurement system, the contact section dynamic feature information capable of reflecting the dynamic characteristics of the multi-machine interconnection power system by using the MS as a sampling period;

Step S3, determining, according to the contact section dynamic feature information, that the contact line on the oscillating contact section is after a fault Whether the active power at the first moment is less than the active power at the first moment after the fault, yes, step S4 is performed, NO, step S6 is performed;

Step S4, determining, according to the contact section dynamic characteristic information, whether the phase difference of the bus voltage at the time after the fault of the tie line on the oscillating contact section is greater than the phase difference of the bus voltage at the first time after the fault, yes, Step S5 is performed, and no, step S6 is performed;

Step S5, determining, according to the contact section dynamic characteristic information, whether the frequency at the first moment after the fault of the sending end bus of the contact line on the oscillating contact section is greater than the frequency of the first time after the fault, and determining that the multi-machine interconnection The power system will have a transient power angle instability at the first time after the fault, otherwise, step S6 is performed;

Step S6: It is determined that the multi-machine interconnected power system does not have a transient power angle instability after the fault, and the set value is = + Γ, and the step SI is performed.

In the first preferred embodiment provided by the present invention, in the step S1, after the information of the WAMS measurement system is used to determine the oscillating contact section of the system after the fault, the contact line on the oscillating contact section is determined.

In a second preferred embodiment of the present invention, when a plurality of active powers of the tie line oscillate in the multi-machine interconnected power system, when a change trend of a variable on the contact line meets an instability condition, The oscillation instability occurs between the multi-machine interconnected power systems; in the case where the oscillation center is in the plurality of the tie lines, the transient power angle instability determination is separately performed for each of the tie lines.

In the third preferred embodiment provided by the present invention, in the step S2, the contact section dynamic feature information capable of reflecting the dynamic characteristics of the multi-machine interconnected power system is periodically acquired by the WAMS measurement system from the fault, The sampling period of the contact section dynamic characteristic information is the same as the sampling period of the PMU measuring unit in the WAMS measurement system;

The dynamic characteristic information of the contact section includes active power of different tie lines on the oscillating contact section at different times, a voltage phase angle of the first end of the tie line, and a frequency of the tie line feed end bus; wherein, the first tie line on the contact section at the first moment after the fault The active power is, the voltage phase angle of the first end of the tie line is respectively, and the contact line bus frequency is Λ'.

According to a fourth preferred embodiment of the present invention, in the step S3, it is determined whether the active power of the contact line on the oscillating contact section at the first moment after the fault is greater than the fault after the fault according to the contact section dynamic characteristic information. The method of active power at the moment is:

The active power of the kth tie line on the oscillating contact section at the first moment after the fault and at the first-time after the fault is respectively ;

And determining, according to the contact section dynamic characteristic information, that the k-th tie line on the oscillating contact section has an active power at a time after the fault is less than an active power at a time after the fault. According to a fifth preferred embodiment of the present invention, in the step S4, it is determined whether the phase difference of the bus voltage at the moment after the fault is greater than the contact line on the oscillating contact section according to the contact section dynamic characteristic information is greater than The method of the phase difference of the bus voltage at the first-time after the fault is:

The phase angle difference of the bus voltage of the kth tie line on the oscillating contact section at the first moment after the fault is: Θ = δ - δ[ ₂ ; the kth tie line on the oscillating contact section is at the moment after the fault The difference between the phase angle difference of the bus voltage and the phase angle of the bus voltage at the time after the fault is: - Θ [- ^τ = {δ _χ - δ[ ₂ ) - (δ^ -s ₂ ^T );

Determining, according to the contact section dynamic characteristic information, that the k-th contact line on the oscillating contact section has a bus voltage phase angle difference at a time after the fault is greater than a bus voltage at a time after the fault Phase angle difference.

In a sixth preferred embodiment provided by the present invention

In the step S5, according to the contact section dynamic feature information, it is determined whether the frequency at the first moment after the fault of the sending bus of the contact line on the oscillating contact section is greater than the frequency at the -r time after the fault is:

The first and second time after a fault - r time of the oscillation frequency of the first contact section of the sending end bus bar contact line k, respectively and f f- ^T · '

And determining, according to the contact section dynamic characteristic information, that the frequency of the sending terminal bus of the kth contact line on the oscillating contact section at the first moment after the fault is greater than the frequency of the first time after the fault when Δ/ = > 0. The beneficial effects of a real-time discriminant method for transient power angle instability based on measured response information provided by the present invention include:

The invention provides a method for real-time discrimination of transient power angle instability based on measured response information, and identifies an oscillating contact section of a multi-machine interconnected power system by using information measured by a WAMS measurement system, and extracting can reflect transient power between oscillating systems The real-time response information of the angular stability characteristic, real-time analysis of the transient power angle stability based on the real-time response information, provides technical support for the safe and stable operation of the large-scale power system.

The power-phase angle-frequency is used as a criterion for quickly determining the stability of the power system transient power angle. The power, phase angle and frequency can be directly obtained by the real-time response information measured by the WAMS measurement system, making the judgment more intuitive and quick. Make this judgment method more practical. DRAWINGS

FIG. 1 is a flow chart of a method for real-time discrimination of transient power angle instability based on measured response information according to the present invention;

2 is a schematic diagram of an oscillating area system provided by the present invention;

FIG. 3 is a schematic structural diagram of an equivalent two-machine system provided by the present invention; 4 is an equivalent circuit diagram of an equivalent two-machine system provided by the present invention;

Figure 5 is a phasor diagram of an equivalent two-machine system provided by the present invention;

FIG. 6 is an equivalent circuit diagram of a tie line provided by the present invention;

FIG. 7 is a schematic diagram of an embodiment of a network structure of a regional multi-machine interconnected power system according to the present invention; FIG. 8 is a view showing a phase angle difference and an active power of a regional multi-machine interconnected power system according to the present invention; Time trend graph;

FIG. 9 is a graph showing a trend of a bus line frequency of a regional multi-machine interconnected power system as a function of time according to the present invention. detailed description

The invention provides a real-time discrimination method for transient power angle instability based on measured response information, and identifies an oscillating contact section of a multi-machine interconnected power system by using information measured by a WAMS (Wide Area Measurement System) measurement system. The measured response information that can reflect the transient power angle stability characteristics of the oscillating system is extracted, and the transient stability of the multi-machine interconnected power system is analyzed in real time according to the measured response information. Specifically, the flowchart of the method is shown in FIG. 1. As can be seen from FIG. 1, the method includes:

Step S l, determining the oscillating contact surface of the multi-machine interconnected power system after the fault by using the information measured by the WAMS measurement system.

In step S2, the WAMS measurement system periodically acquires the dynamic characteristics of the contact section that can reflect the dynamic characteristics of the multi-machine interconnected power system by using the Γ as the sampling period.

Step S3: Determine whether the active power of the contact line on the oscillating contact section at the first moment after the fault is less than the active power at the time after the fault according to the dynamic characteristic information of the contact section. If yes, go to step S4, otherwise, go to step S6.

Step S4: determining, according to the dynamic characteristic information of the contact section, whether the phase difference of the bus voltage of the contact line on the oscillating contact section at the time after the fault is greater than the phase difference of the bus voltage of the first time after the fault, and executing step S5. Otherwise, go to step S6.

Step S5, determining, according to the dynamic characteristic information of the contact section, whether the frequency at the first moment after the fault of the sending bus of the contact line on the oscillating contact section is greater than the frequency of the first time after the fault, and determining that the multi-connected power system is after the fault The transient power angle instability will occur at the first moment, otherwise, step S6 is performed.

Step S6: It is determined that the multi-machine interconnected power system does not have transient power angle instability after the fault, and the set value is i = i + T, and step S l is performed.

In step S6, after determining that the multi-machine interconnected power system does not have transient power angle instability after the fault, the set value is = _{ί +} Γ, and step SI is performed, that is, the multi-machine after the sampling period Γ time is judged. Transient power angle stability of interconnected power systems. Embodiment 1:

Embodiment 1 of the present invention provides an embodiment of a method for real-time discrimination of transient power angle instability based on WAMS measurement information provided by the present invention.

Specifically, in this embodiment, the transient power angle stability of the multi-machine interconnected power system is determined in real time, and the measurement is performed by the WAMS system from the time of the fault. In step S1, the oscillating contact section of the multi-machine interconnected power system after the fault is determined by the measurement information measured by the WAMS system, and the tie line at the oscillating center is identified, thereby dividing the multi-machine interconnected power system into an oscillating two-area system.

In step S2, the contact section dynamic characteristic information capable of reflecting the dynamic characteristics of the multi-machine interconnected power system is periodically obtained from the WAMS measurement system after the fault, and the sampling period of the contact section dynamic characteristic information is compared with the WAMS measurement system. The sampling period of the PMU (Phasor Measurement Unit) measurement unit is the same, including the active power of different tie lines on the oscillating contact section at different times, the voltage phase angle of the first end of the line, and the bus frequency of the tie line. The active power of the first tie line on the oscillating contact section at the first moment after the fault is , the voltage phase angle of the first end of the tie line is respectively, and the bus frequency of the tie line feed end is .

As shown in the schematic diagram of the oscillating two-zone system shown in FIG. 2, the two regions are respectively zone A and zone B, and zone A and zone B contain multiple generators, and the system of zone A and the system of zone B are respectively equivalent. The structure diagram and the equivalent circuit diagram of the equivalent two-machine system shown in FIG. 3 and FIG. 4 can be obtained, and FIG. 5 is the phasor diagram of the equivalent two-machine system.

The principle and method for identifying the transient power angle instability of the system based on the measured response information of the oscillating contact section are:

The active power on the tie line between area A and area B is P _eAB , and the phase angle difference between the two ends of the tie line between area A and area B is ^ the mechanical power of the prime mover that maintains the active power of the tie line between area A and area B For _ΑΒ , the dynamic stability characteristics of the system reflected on the contact line between the area _区域 and the area B are shown in Table 1.

Table 1: Contact line information change corresponding system dynamic stability characteristics table

No. Contact line information change relationship stability

1 △ >0, Αθ>0, P _mAB < P _eAB power angle is stable

2 △ >0, Αθ>0, P _{mAB >} P _eAB power angle stability

3 _{ΔΡ Μβ >} 0, Αθ<0, P _mAB < P _eAB power angle stable

4 _{ΔΡ Μβ} <0, Αθ<0, P _mAB < P _eAB power angle stability

5 Δ^ _β <0, Αθ<0, P _mAB > P _eAB power angle stability

6 _{ΔΡ Μβ} <0, Αθ>0, P _mAB < P _eAB power angle stable

_{7 ^ P eAB <0- Δ ^} > 0, P mAB> P eAB angle instability _ΔΡ ΜΒ Table I represents the change amount of the active region of the contact line between Α and the region B, ΑΘ represents area A and The amount of change in the phase angle difference between the two ends of the tie line between the areas B is as shown in Table 1, _{ΔΡ ΜΒ} >0, Δθ<0, /^>/ ⁵ ^ except for the case where the contact line information is only the area Α The amount of change in the active power Δ _Β < 0 on the line of communication with the area B, the amount of change in the phase angle difference between the two ends of the line between the area Α and the area Δ > 0, the line between the area Α and the area 联络When the prime mover mechanical power of the active power is greater than the active power Ρ _{,, the} transient power angle instability occurs in the multi-machine interconnected power system composed of the Α region and the B region.

When there is a plurality of tie line active power oscillations in the multi-machine interconnected power system, the active power delivered to each of the contact lines where the oscillation center is located has the same property as shown in Table 1 for the corresponding mechanical power. When it is observed that the variation trend of the variable on any of the contact lines satisfies the instability condition, it indicates that the oscillation instability occurs between the multi-machine interconnected power systems. Therefore, in the case where the oscillation center is in multiple tie lines, it is only necessary to analyze and judge each tie line separately.

Specifically, the amount of change in the active power at the contact line and the phase angle difference at both ends takes the amount of change from the first time to the first time after the fault, that is, when the ^^ </^- τ and > are satisfied, the multi-machine interconnected power system Transient power angle instability will occur. Where _λ and _λ respectively represent the active power of the kth tie line on the oscillating contact section at the first moment after the fault, the phase angle difference between the two ends of the tie line and the prime mover mechanical power, ^ and ^ respectively indicate the time after the fault The active power of the kth tie line on the oscillating contact section and the phase angle difference between the two ends of the tie line.

As can be seen from Figure 5, the electromagnetic power output by the equalizer A is:

According to the relationship between the variables shown in Figure 5:

I _B X _L

then:

Active power expression on the contact line between area A and area B

_ ^{V s} -sin( _ ) (4) where is the voltage phase angle at the beginning of the line, and the voltage amplitude at the head end of the line is the reactance of the transmission line. According to Figure 4 and Figure 5:

P _eAB = I _B V _B ∞ + δ) = Ι _Β Ε _Β οο^φ

= Ε _Α Ι _Β οί,(φ + δ) = Ρ ₀

That is, when the resistance characteristics between the systems are neglected, the active power delivered on the tie line is equal to the electromagnetic power output by the equivalent generator of the delivery system during the oscillation process. Combined with formula (4), the active power and the delivery system on the contact line where the oscillation center is located The electromagnetic power of the equivalent generator in the transient process has the same geometrical variation characteristics.

The phase difference of the bus voltage of the first tie line on the oscillating contact section at the first moment after the fault is:

Then, the change in the phase difference of the bus voltage of the kth tie line on the oscillating contact section at the i-th time after the fault at the i-th time is:

Note that it is only necessary to satisfy the condition > θ[- ^τ in step S4:

-^) >0 (8) Analysis Figure 2, for the delivery system, each tie line port has a generator characteristic, which can be equivalent to a generator connected to the bus. The active power on the contact line has a load characteristic for the delivery system, which can be equivalent to the load connected to the bus. Therefore, at the first moment in the transient process, the equivalent circuit diagram of the first tie line is shown in Fig. 6. Then the rotor equation of the equivalent generator at the moment is:

Where M _t is the inertia time constant of the equivalent generator, which is the difference in rotational speed under synchronous coordinates. Differential is used instead of differential:

Μ,, ~ ^k - = Μ,, 丄P _ _k (10)

At At

In the formula, the frequency change of ΔΛ'' is the equivalent generator port time. It can be seen from Table 1 that when the power angle is unstable, ^ _S > P^, Bay iJ:

(11)

At

The condition that the frequency at the first moment after the fault of the sending bus of the kth contact line on the oscillating contact section in step S5 is greater than the frequency at the first moment after the fault is satisfied:

ΔΛ ^! =Λ ^! _Λ ^! — ^Γ >ο (12) can satisfy ^ > , to meet the conditions of transient power angle instability in Table 1: P _mAB >P _eAB , where / d, equivalent generator (3⁄4 Port frequency at the first, -r time. Since the equivalent generator is directly connected to the tie line bus, the generator port frequency is equal to the contact line bus frequency, which can be acquired in real time according to the WAMS measurement system.

In summary, the following power-phase angle-frequency fast criterion for transient power angle instability can be obtained: II) K >0 (13)

In step S3, the amount of active power change of the first tie line on the oscillating contact section at the first moment after the fault is: Δ3⁄4=3⁄4 (14) If Λ^=^- ^Τ <0 is satisfied, the criterion condition (I) is established, and step S4 is performed; if Λ^ _ ^τ <ϋ is not satisfied, step S6 is executed.

In step S4, the change in the angular phase difference of the bus voltage of the kth contact line on the oscillating contact section at the i-th time after the fault at the i-th time is:

If Λ = Κ > 0 is satisfied, the criterion condition (Π) is established, and step S5 is performed; if Ae' = e'-e'- ^f > 0 is not satisfied, step S6 is performed.

In step S5, the frequency change of the bus line at the sending end of the kth contact line on the oscillating contact section at the first moment after the fault is:

If ΔΛ' = -/Γ ^Τ >Ο is satisfied, the criterion condition (in) is established, and the system will have transient power angle instability;

Af = fi - f ^T > 0, then step S6 is performed.

Embodiment 2:

The second embodiment of the method for real-time discrimination of transient power angle stability based on the measured response information provided by the present invention is an embodiment of a real-time discrimination method for transient power angle stability of a multi-machine interconnected power system in a certain area, the region The schematic diagram of the grid structure of the interconnected system is shown in Figure 7. Using the 2010 winter mode data, the simulation calculation tool is a full-process dynamic simulation program (PSD-FDS), and the disturbance response data obtained by the simulation program is used to simulate the wide-area measurement system. Real-time measurement data. The fault condition is that a three-phase short-circuit fault occurs on the bus B1 side of the line L1 at the 0s time, 0.09s trips the B1 side switch, 0.1s trips the B13 side switch, and the line L2 is tripped. Monitor the tie line L3 connected to System A.

Step S1' _: Simulate the real-time measurement data of the wide-area measurement system by using the disturbance response data obtained by the simulation program, and determine the contact line on the oscillation contact section. In this example, the contact line L3.

Step S2': extracting the contact section characteristic information reflecting the oscillation characteristic of the system, the data after the fault starts from 0.1s, the characteristic quantity is the active power P _e of the tie line L3, the phase angle of the bus line B2 and the phase angle of the bus line B3 and the bus line B3 frequency/. The trend of the characteristic variables is shown in Figure 8 and Figure 9.

Step S3': According to the dynamic characteristic information, analyze the variation characteristic of the active power of the tie line, and the amount of active power change of the first tie line on the oscillating contact section at the time of the fault is: if Δ = -/^ < 0 is satisfied, the criterion is Condition (I) is established, step S4 is performed; if ΛΡΧ_Ρ ^τ <0 is not satisfied, step S6 is performed.

It can be seen from Fig. 8 that before = 0.42 s, the active power of line L3 continues to increase, and the criterion condition is not satisfied; t = 0A2s After that, the active power continues to decrease and the criteria are met.

Step S4': The phase difference of the bus voltage of the first tie line on the oscillating contact section at the first moment after the fault is:

θ' = _ 3⁄42

Then, the change in the voltage phase angle difference of the bus voltage of the first tie line on the oscillating contact section at the first moment is:

ΑΘ· =θ· -θ- ^τ = (δ ₁ -δ ₂ )-(δ^ _] ^τ -δ^)

If Δ^ = ^ -^ >0 is satisfied, the criterion condition (Π) is established, and step S5 is performed; if Δ ' = ^ -^ >0 is not satisfied, step S6 is performed.

It can be seen from Fig. 8 that the phase angle difference of the line L3 continues to increase after the failure, and the criterion condition is established.

Step S5': The frequency change of the bus line at the kth contact line of the oscillation contact section at the first moment after the fault is:

= f -f ^T

Af = ft - f ^T > 0, then step S6 is performed.

It can be seen from Fig. 9 that before i = 0.52 s, the bus frequency of the transmitting end of line L3 continues to decrease, and the criterion condition is not satisfied; after i = 0.52 s, the frequency of the transmitting bus starts to rise, and the criterion condition is established.

Step S6': The condition for determining the transient power angle instability of the system is indispensable, that is, the condition (1), the condition (Π), and the condition (III) are simultaneously established. It can be seen from the above analysis that after i = 0.52 s, the criterion conditions are all established, so after i = 0.52 s, it can be judged that the transient power angle instability will occur.

The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but are not limited to the specific embodiments, and various equivalent and modified processes performed by those skilled in the art according to the specific technical solutions are also in the protection scope of the present invention. Inside.

Claims

Rights request

1. A method for real-time determination of transient power angle stability based on measured response information to determine the transient power angle stability of a multi-machine interconnected power system after a fault, characterized in that the method includes:

Step S1, determine the oscillation contact section of the multi-machine interconnected power system after the fault through the information measured by the WAMS measurement system;

Step S2, using Γ as the sampling period, periodically obtain the dynamic characteristic information of the contact section that can reflect the dynamic characteristics of the multi-machine interconnected power system through the WAMS measurement system;

Step S3: Based on the dynamic characteristic information of the contact section, determine whether the active power of the tie line on the oscillating contact section at the -th moment after the fault is less than the active power at the -th moment after the fault. If yes, proceed to step S4. No, Execute step S6;

Step S4: Based on the dynamic characteristic information of the contact section, determine whether the bus voltage phase angle difference of the tie line on the oscillating contact section at the th time after the fault is greater than the bus voltage phase angle difference at the th time after the fault. If so, execute step S5, No, execute step S6;

Step S5: According to the dynamic characteristic information of the contact section, determine whether the frequency of the sending end busbar of the tie line on the oscillating contact section at the time after the fault is greater than the frequency at the -th time after the failure. If so, determine the multi-machine interconnection The power system will experience transient power angle instability at the first moment after the fault. If not, proceed to step S6;

Step S6: It is judged that the multi-machine interconnected power system will not experience transient power angle instability at the moment after the fault, set the value to ί' = ί' + Γ, and execute step SI.

2. The method of claim 1, wherein in step S1, after determining the oscillation contact section of the post-fault system through the information measured by the WAMS measurement system, the tie line on the oscillation contact section is determined. .

3. The method according to claim 1, characterized in that when the active power of multiple tie lines in the multi-machine interconnected power system oscillates, the changing trend of variables on any one of the tie lines satisfies the failure condition. When the stable condition is reached, oscillation instability occurs between the multi-machine interconnected power systems; when the oscillation center is located in multiple tie lines, a transient power angle instability judgment is performed for each tie line separately. .

4. The method of claim 3, wherein in step S2, dynamic characteristics of the contact section that can reflect the dynamic characteristics of the multi-machine interconnected power system are periodically acquired through the WAMS measurement system starting from the time of the fault. Information, the sampling period Γ of the contact section dynamic characteristic information is the same as the sampling period of the PMU measurement unit in the WAMS measurement system;

The dynamic characteristic information of the contact section includes the active power of different tie lines on the oscillating contact section at different times, the voltage phase angle at the beginning and end of the tie line, and the bus frequency at the sending end of the tie line; among them, the th tie line on the oscillating tie section at the first moment after the fault The active power is, the voltage phase angles at the first and end of the tie line are, _Sk ' ₂ respectively, and the frequency of the bus at the sending end of the tie line is Λ'.

5. The method according to claim 4, characterized in that, in step S3, based on the dynamic characteristic information of the contact section, it is determined whether the active power of the tie line on the oscillating tie section at the first moment after the fault is less than the fault. The method of active power at the last -Γ moment is:

The active power of the k-th tie line on the oscillation tie section at the -th time and -Γ-th time after the fault are respectively and P ^{i T} .,

According to the dynamic characteristic information of the contact section, it is judged that when -C<o, the active power of the k-th tie line on the oscillating contact section at the -th time after the fault is less than the active power at the -Γ-th time after the fault.

6. The method of claim 4, wherein in step S4, the bus voltage phase of the tie line on the oscillating tie section at the first moment after the fault is determined based on the dynamic characteristic information of the tie section. The method to determine whether the angle difference is greater than the bus voltage phase angle difference at the i - T moment after the fault is:

The bus voltage phase angle difference of the k-th tie line on the oscillating tie section at the first moment after the fault is: Θ =δ[ _χ -δ[ _2. , the k-th tie line on the oscillating tie section after the fault The difference between the bus voltage phase angle difference at the Γth moment after the fault and the bus voltage phase angle difference at the Γth moment after the fault is: Θ[-Θ ^Τ =(δ[ _γ -5[ ₂ )-(5^ -Slf);

It is determined based on the dynamic characteristic information of the contact section that when - )>0, the bus voltage phase angle difference of the k-th tie line on the oscillating contact section at the th moment after the fault is greater than the bus voltage phase angle difference at the th moment after the fault. .

7. The method according to claim 4, characterized in that, in the step S5, based on the dynamic characteristic information of the contact section, it is determined whether the frequency of the sending end bus of the tie line on the oscillating contact section at the first moment after the failure is The method that is greater than the frequency at the moment after the fault is:

The frequencies of the sending end busbar of the k-th tie line on the oscillating tie section at the -th and -Γth moments after the fault are f and f — ^T respectively;

According to the dynamic characteristic information of the contact section, it is judged that when Δ/ = f _k -f _k ^T > 0, the frequency of the sending end bus of the k-th tie line on the oscillating contact section at the i-th moment after the fault is greater than that after the fault. The frequency at - Γ moment.