CN108988320A - Electrical Power System Dynamic element responds characteristic is to Enhancement of Transient Voltage Stability impact analysis method - Google Patents

Abstract

The invention discloses a kind of Electrical Power System Dynamic element responds characteristics to Enhancement of Transient Voltage Stability impact analysis method.In order to study generator, the main influence of HVDC transmission system (HVDC) and induction conductivity on Enhancement of Transient Voltage Stability, from the angle of broad sense branch potential energy, new analysis method is proposed to study influence of the above-mentioned main dynamic element to Enhancement of Transient Voltage Stability.The information of the changing rule and stability margin that are distributed according to transient potential energy in network after failure is basic variable with the idle recovery characteristics of dynamic element each after failure, establishes evaluation index, and then to causing power grid transient voltage instability Mechanism to analyze.Finally, carried out emulation testing using three machines, nine node ac and dc systems on MATLAB and PSAT software platform, the results showed that the feasibility and validity of this method.

Description

Analysis Method of Influence of Response Characteristics of Power System Dynamic Components on Transient Voltage Stability

technical field

The invention relates to the technical field of impact analysis of power grid transient voltage stability, in particular to the analysis of the influence of dynamic components including high-voltage direct current transmission, generators, induction motors, etc. The stability mechanism is analyzed.

Background technique

As the number of DC feed-in loops of the receiving-end power grid represented by the Yangtze River Delta and the Pearl River Delta continues to increase, and the proportion of DC power feed-in continues to increase, my country's power grid will no longer be a pure AC grid, but will become a nationwide AC-DC system. Large interconnected power grids with progressively increasing complexity. Large-scale power outages due to voltage instability or voltage collapse have occurred one after another. Electric power scholars at home and abroad have to pay more and more attention to voltage stability. Compared with the traditional AC system, the high-voltage DC system with the thyristor as the core has many new dynamic characteristics. The influence of the reactive power recovery characteristics after the fault on the voltage stability is more prominent. As the proportion of DC feed-in gradually increases, the voltage of the system Stability will be more affected. How to better evaluate the impact of a series of dynamic components including DC converters on stability after faults, and guide the method of optimizing stability performance are of practical significance. In traditional research ideas, the time-domain simulation method is often used to analyze the influence of dynamic components on the transient stability of the system by changing system parameters, but it takes a long time. The direct method has gradually entered the public's field of vision because it can be used to analyze stability and provide stability margins, and the energy function has become an important method. In the AC/DC hybrid system, whether the reactive power recovery characteristics of the DC receiving end commutation system or the voltage instability of the entire system caused by the instability of the induction motor is difficult to distinguish the specific reasons. There is little work on this issue. However, how to construct corresponding evaluation indicators to distinguish the impact of different dynamic components is a difficult problem.

Contents of the invention

With the increase of the complexity of the power network, the dynamic recovery characteristics of various power equipment will have different impacts on the transient voltage stability of the power system after the system fails. The excessive concentration of system transient energy after a fault is the main cause of system instability, and the change of generator kinetic energy will be reflected in various local potential changes according to the parameters and characteristics of each part of the system. Inspired by the above ideas and transient voltage analysis techniques, the present invention proposes an evaluation method for evaluating the influence of different system dynamic components on the transient voltage stability. From the perspective of generalized branch potential energy, the invention proposes a new analysis method to study the influence of main dynamic elements such as generators, high-voltage direct current transmission systems (HVDC), induction motors, etc. on transient voltage stability. According to the change law of transient potential energy distribution in the network after the fault and the information of the stability margin, the dynamic recovery characteristics of the reactive power of each electrical equipment after the fault are used as the basic variable, and the evaluation index is established, and then the mechanism of the transient voltage instability of the power grid is established. for analysis. This method can quantitatively weigh the role of each dynamic component, analyze the mechanism of system voltage instability, and use it to guide the optimization strategy of system transient voltage stability.

The purpose of the present invention can be achieved by taking the following technical solutions:

A method for analyzing the influence of response characteristics of power system dynamic components on transient voltage stability, the analysis method comprising the following steps:

S1. Establish a mathematical model of the power system, and construct an energy function expression that can reflect the system model based on Lyapunov theory;

S2. Determine the transient voltage stability. The present invention judges the transient voltage stability by adopting the bifurcation condition of the power system and the constant energy surface constructed by the heuristic voltage instability type dominant unstable equilibrium point, but is not limited to this method. The steps are as follows:

S201, constructing an energy function;

S202, finding the dominant unstable equilibrium point;

S203, find the critical energy Ucr;

S204. Find the energy U at the moment of fault clearing;

S205. Determine the magnitude of the energy U and the critical energy Ucr at the time of fault clearing, if the energy U at the time of fault clearing is greater than the critical energy Ucr, then determine that the transient voltage of the system is unstable; otherwise, continue to the next step;

S206 , judging whether a singular surface is encountered, if so, judging that the transient voltage of the system is unstable, otherwise, judging that the system is stable.

S3. According to the energy function expression constructed in step S1, extract the part related to the dynamic power element, and establish the potential energy component function of each dynamic element, wherein the dynamic element includes but not limited to generator, high voltage direct current transmission system, induction motor ;

S4. During the fault period, the power system injects a large amount of energy into the grid, and the increase in the generator speed leads to an increase in kinetic energy. After the fault is cleared, the total energy is conserved, and the kinetic energy is gradually converted into the potential energy of each component and transmission line along the power network. With the oscillating change of kinetic energy, the potential energy of each dynamic element increases gradually and is accompanied by certain oscillation. The dynamic element with the largest increase in potential energy will be subject to greater energy impact, and accordingly it is easier to form local energy overshoot, which makes it more prone to collapse here. Therefore, after a fault, the potential energy of the maximum potential energy of each dynamic element can be used The potential energy increment of the first half cycle wave of the oscillation curve is used to simply analyze the vulnerable area of the power grid.

Suppose the time when the potential energy component of the equipment reaches the maximum value (or maximum value) after the fault is T ₂ , and the potential energy component at the corresponding time is U ₂ , in this cycle, the time of the minimum value before reaching the maximum value is T ₁ , and the potential energy The component is U ₁ , then the potential energy difference in this cycle is ΔU=U ₂ -U ₁ .

Evaluation index one: σ ₁ = ΔU/ΔQ

Evaluation index two: σ ₂ ＝V(T ₂ )/ΔU

Among them, ΔQ is the reactive power variation of the power equipment under the influence of dynamic recovery characteristics after a fault within the corresponding time period. V(T ₂ ) is the corresponding voltage amplitude of the equipment connected to the bus at T ₂ time. _The larger the value of σ1, it means that in this cycle, the reactive power dynamic changes of the power equipment make the potential energy increase larger, that is, the energy impact suffered is greater, and it is easier to exceed the range that the network can withstand. Then, the easier it is to lead to the destruction of stable conditions here, and finally lead to the collapse of the system; the smaller the value of _σ2 , it means that when the equipment is restored after a fault, the voltage value of the connected bus node Still relatively low, that is to say, it is more likely to become a critical branch here. Thus, the evaluation of the influence of different system dynamic elements on the transient voltage stability can be realized.

Furthermore, there are n generator nodes, N load nodes, two DC system converter station bus nodes, and only one balance node in the power system. The mathematical model and energy function expression of the dynamic components are as follows:

The fourth-order generator model used is:

The third-order induction motor model used is:

The energy function expression is:

U＝U _AC +U _L1 +U _L2i +U _g +U _R +U _I +U _d +U _DC

in:

and have:

Wherein, subscripts i and j represent network bus node numbers, i=1, 2, . . . , n+N+3; j=1, 2, . . . , n+N+3.

Among them, ρ _i is the parameter to make B _i ^-1 T _i positive definite, and for any non-zero matrix vector, there is x ^T B _i ^-1 T _i x>0, i=1, 2,...,n . C=[C ₁ ,...,C _n ] ^T , C _i =[0 l];

U _DC ＝-V _I V _R B _IR cos(θ _I -θ _R );

In the above formula, when i=1, 2,...,n, ω _i is the generator speed, δ _i is the generator rotor angle, M _i is the generator inertia time constant, P _mi is the generator mechanical power, D _i is the damping coefficient, E′ _qi is the q-axis transient potential, X _di is the transient reactance of the generator, X′ _di is the sub-transient reactance of the generator, T’ _doi is the d-axis transient time constant, E _fdi is Excitation potential, P _ei is the electromagnetic power of the generator, μ _i is the feedback gain coefficient of the excitation controller, T _vi is the excitation control time constant, k _i is the linear coefficient related to the connected bus voltage in the first-order mathematical model of the excitation voltage, l _i is the control constant connected to the bus i to make the excitation of the generator positive; the subscript R represents the variable on the rectifier side, the subscript I represents the variable on the inverter side, and the voltage amplitude of the AC bus of _VR and V _I , P _dR +jQ _dR and P _dI + jQ _dI is the compensation power injected by the converter; when i=n+1, n+2,...,n+N+3, T′ _doi is the stator open circuit time constant, _Mi is the induction motor Inertial time constant, E′ _Li is the amplitude of the internal potential, X _r is the equivalent leakage reactance of the rotor winding, X _m is the mutual inductance of the stator and rotor, X _s is the leakage reactance of the stator winding, X′ _i is the transient reactance, and X _i is Synchronous reactance, δ _i is the power angle of the induction motor, s _i is the slip of the induction motor, T _mi is the electromagnetic torque of the induction motor, T _ei is the mechanical torque; U _AC is the AC network potential energy, U _L1 is the static load potential energy, U _L2i is the load potential energy of the induction motor connected to node i, U _g is the energy sum of all generators in the system, U _R is the potential energy of the DC rectifier side and the AC network interface, U _I is the potential energy of the DC inverter side and the AC network interface, and U _DC is the DC Potential energy between network nodes, U _d is the potential energy component formed by DC power exchange, V _i and V _j are the voltage amplitudes of bus labels i and j respectively, θ _i and θ _j are the voltage phase angles of bus labels i and j, respectively, Q _Li is the reactive power of the static load connected to the bus marked i, and P _Li is the active power of the static load connected to the bus marked i.

Compared with the prior art, the present invention has the following advantages and effects:

From the perspective of energy and domain, based on the distribution and propagation characteristics of energy in the power system, the present invention takes the reactive dynamic characteristics of dynamic components as the variable of interest to analyze the factors affecting the transient voltage instability of the system. Compared with the time-domain simulation The method can provide quantitative margin information, takes a short time, can predict and analyze the factors related to transient voltage instability in advance, and distinguishes the influence characteristics of various dynamic components. The present invention provides a simple evaluation index, combines the transient voltage, reactive power and energy, and comprehensively analyzes the influence of each dynamic element on the transient voltage stability from a systematic point of view. On this basis, it can further guide the selection of voltage optimization measures, such as , compared with the traditional method of directly installing reactive power compensation equipment, this embodiment also provides another idea, that is, the potential energy change trend after a fault can be affected by improving the relevant parameters of the DC system during the construction of the power grid, and then fundamentally improve Transient voltage stability under fault conditions, and this method may also be more economical than configuring certain reactive power compensation equipment.

Description of drawings

Fig. 1 is a schematic flow chart of the method for analyzing the influence of the response characteristics of power system dynamic components on transient voltage stability disclosed in the present invention;

Figure 2 is a schematic diagram of a three-machine nine-node system including DC;

Fig. 3 is a part of the bus node voltage diagram when the fault is cleared at 1.18s;

Figure 4 is a curve diagram of the induction motor and DC potential energy change after the fault is cleared in 1.178s;

Fig. 5 is a curve diagram of generator potential energy change after 1.178s to clear the fault;

Figure 6 is the power angle diagram of the generator when the fault is cleared in 1.178s;

Figure 7 is the slip diagram of the induction motor under the condition of instability after clearing the fault in 1.18s.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments It is a part of embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Example

As shown in FIG. 1 , the flow chart of the method for analyzing the influence of the response characteristics of the dynamic components of the power system on the transient voltage stability, the method for analyzing the influence of the response characteristics of the dynamic components of the power system on the transient voltage stability disclosed in this embodiment includes the following steps:

Step S1, establishing a mathematical model of the power system, and constructing an energy function expression that can reflect the system model based on Lyapunov theory. The obtained energy function expression is as follows:

U＝U _AC +U _L1 +U _L2i +U _g +U _R +U _I +U _d +U _DC

in:

and have:

Among them, ρ _i is a parameter to make B _i ^-1 T _i positive definite, and for any non-zero matrix vector, x ^T B _i ^-1 T _i x>0, i=1, 2, 3;

C=[C ₁ ,...,C _n ] ^T , C _i =[0 l];

The subscripts i and j represent the network bus node labels. In the present embodiment, i and j=1, 2, 3, ..., 9, when i=1, 2, 3, the bus bar of the generator is connected, When i=6, the induction motor load bus is connected, and the subscripts i and j represent the node numbers of the network bus. When i=1, 2, 3, ω _i is the generator speed, δ _i is the rotor angle of the generator, _Mi is the inertia time constant of the generator, P _mi is the mechanical power of the generator, D _i is the damping coefficient, E′ _qi is the q-axis transient potential, X _di is the transient reactance of the generator, X′ _di is the sub-transient reactance of the generator, T’ _doi is the d-axis transient time constant, E _fdi is the excitation potential, P _ei is Generator electromagnetic power, μ _i is the feedback gain coefficient of the excitation controller, T _vi is the excitation control time constant, k _i is the linear coefficient related to the connected bus voltage in the first-order mathematical model of the excitation voltage, l _i is the connected bus i is the control constant that makes the generator excitation positive; R subscript represents the variable on the rectifier side, I subscript represents the variable on the inverter side, V _R and V _I AC bus voltage amplitude, P _dR +jQ _dR and P _dI +jQ _dI is the compensation power injected by the converter; when i=6, T′ _doi is the stator open-circuit time constant, M _i is the inertia time constant of the induction motor, E _L ′ _i is the amplitude of the internal potential, X _r is the rotor winding, etc. X _m is the mutual inductance of the stator and rotor, X _s is the leakage reactance of the stator winding, X′ _i is the transient reactance, X _i is the synchronous reactance, δ _i is the power angle of the induction motor, s _i is the slip of the induction motor, T _mi is the electromagnetic torque of the induction motor, T _ei is the mechanical torque; U _AC is the potential energy of the AC network, U _L1 is the static load potential energy, U _L2i is the load potential energy of the induction motor connected to node i, and U _g is the energy of all generators in the system and, U _R is the potential energy of the DC rectifier side and the AC network interface, U _I is the potential energy of the DC inverter side and the AC network interface, U _DC is the potential energy between the DC network nodes, U _d is the potential energy component formed by the DC power exchange, V _i and V _j is the voltage amplitude of the bus labels i and j respectively, θ _i and θ _j are the voltage phase angles of the bus labels i and j respectively, Q _Li is the reactive power of the static load connected to the bus labeled i, P _Li is the active power of the static load connected to the bus marked i.

Step S2, determining transient voltage stability. The present invention judges the transient voltage stability by using the bifurcation condition of the power system and the constant energy surface constructed based on the heuristically obtained voltage instability type dominant unstable equilibrium point, but is not limited to this method.

In this implementation case, a three-phase short-circuit fault is set at 1s on busbar 5 and cleared at 1.18s. PSAT is interrupted during time-domain simulation, as shown in Figure 3. Under this fault, the transient operation track after the fault encounters The singular surface makes it impossible to calculate the time domain simulation under the differential algebraic equation (DAE) model. At this time, the instantaneous energy value after the fault is cleared is 0.36, which is less than the critical energy obtained from the dominant unstable equilibrium point. However, under the fault , after the fault, the transient operation trajectory encounters a singular surface, which makes the time domain simulation under the DAE model impossible to calculate. Since the singular bifurcation phenomenon is closely related to the transient voltage instability, this embodiment is also regarded as the occurrence of transient voltage instability. stable.

Step S3, according to the energy function expression constructed in step S1, extract the part related to the dynamic power components, and establish the potential energy component function of each dynamic component, wherein the dynamic components include but not limited to generators, high-voltage direct current transmission systems, induction electric motor.

The potential energy component function of each dynamic element obtained by step S1 is expressed as follows:

Generator potential energy:

Induction motor potential energy components:

Potential energy components of DC transmission system:

See step S1 for each symbolic representation variable. The value and change curve of each potential energy component at each time step can be obtained from the time domain simulation results.

Step S4. During the fault period, the power system injects a large amount of energy into the grid, and the increase in the generator speed leads to an increase in kinetic energy. After the fault is cleared, the total energy is conserved, and the kinetic energy is gradually converted into the potential energy of each component and transmission line along the power network. With the oscillating change of kinetic energy, the potential energy of each dynamic element increases gradually and is accompanied by certain oscillation. The dynamic element with the largest increase in potential energy will be subject to greater energy impact, and accordingly it is easier to form local energy overshoot, which makes it more prone to collapse here. Therefore, after a fault, the potential energy of the maximum potential energy of each dynamic element can be used The potential energy increment of the first half cycle wave of the oscillation curve is used to simply analyze the vulnerable area of the power grid.

Suppose the time when the potential energy component of the equipment reaches the maximum value (or maximum value) after the fault is T ₂ , and the potential energy component at the corresponding time is U ₂ , in this cycle, the time of the minimum value before reaching the maximum value is T ₁ , and the potential energy The component is U ₁ , then the potential energy difference in this cycle is ΔU=U ₂ -U ₁ .

Evaluation index one: σ ₁ = ΔU/ΔQ

Evaluation index two: σ ₂ ＝V(T ₂ )/ΔU

Among them, ΔQ is the reactive power variation of the power equipment under the influence of dynamic recovery characteristics after a fault within the corresponding time period. V(T ₂ ) is the corresponding voltage amplitude of the equipment connected to the bus at T ₂ time. _The larger the value of σ1, it means that in this cycle, the dynamic change of reactive power of the power equipment makes the potential energy increase faster, and the greater the increase, that is, the greater the energy impact it bears, the easier it is to exceed the power of the network. The range that can be tolerated is more likely to lead to the destruction of stable conditions here, and finally lead to the collapse of the system; the smaller the value of σ ₂ , it means that when the equipment receives a greater energy impact when recovering from a fault, the The voltage value of the input bus node is still relatively low, which means that it is more likely to become a critical branch.

Based on the system in Figure 2, a three-phase short-circuit fault is set when bus 5 is in 1s, and the faults are cleared at 1.05s, 1.1s, 1.14s, and 1.178s respectively.

Comparing the post-fault potential energy oscillation amplitude curves (take Fig. 4 and Fig. 5 as examples) at the same time when the fault is cleared, it can be clearly found that in the period when the DC system and No. The oscillation amplitude of the maximum value is the largest, followed by the induction motor load, and finally by generators 1 and 3. At the same time, it can also be found that with the increase of the electrical distance from the fault point, the time for the maximum amplitude of potential energy oscillation of each electrical equipment under the energy impact gradually passes, which also reflects the propagation characteristics of energy in the network and the temporary State voltage instability may occur in the case of multiple swings.

Table 1. Index σ ₁

Table 2. Index two σ ₂

In Table 1, the corresponding value of index σ ₁ of the DC system is much higher than that of other equipment, followed by No. 2 generator and induction motor load, while No. 3 generator whose electrical distance from the fault point is the farthest is the smallest. It shows that under the influence of the recovery characteristics of each electrical equipment, the change of dynamic reactive power of the DC receiving-end commutation system leads to the potential energy oscillation amplitude and the increase speed of the DC system are easier to become larger when the maximum energy impact is received, that is, it is easier in this pendulum The local energy is too large, and the system stability is destroyed beyond the bearing capacity of the place, thereby accelerating the transient voltage collapse of the system. Therefore, the reactive power recovery characteristics of the DC receiving-end commutation system play a dominant role in the transient voltage instability of the system.

With the increase of fault clearing time, the absolute value of induction motor load and No. 2 generator index σ ₁ increases gradually, while the value of σ ₁ of DC system decreases slightly. Therefore, the longer the fault clearing time, the larger the voltage drop of each node of the system when the fault occurs, and the influence of the load characteristics of the induction motor on the transient voltage stability gradually increases. Among the three generators, when Generator No. 2 is impacted by energy, under the action of the DC recovery characteristics, the load characteristics of the induction motor and the transmission characteristics of the transmission network, the dynamic change of reactive power formed to support the network node voltage will affect the oscillation amplitude of its own potential energy. The value and frequency are higher than those of the other two generators, indicating that after the fault is cleared, among the three generators, generator No. 2 is more prone to excessive local energy changes. The generator should experience power angle instability earlier than the other two generators. Because the No. 2 bus connected to it is connected to the DC system, and at the same time, in Table 2, the index 2 σ ₂ corresponding value of No. 2 generator, high-voltage DC system and induction motor load is far lower than that of No. 1 generator and No. 3 Generator, so No. 2 generator, DC system, induction motor load form the voltage vulnerability point of this power system.

In addition, it can be clearly seen from the data in Table 1 and the above two tables that with the increase of the fault clearing time, the greater the amplitude of the voltage drop during the fault, the greater the value of energy injected into the system during the fault, and the dynamics of the system after the fault. The greater the energy impact on the components, the greater the local energy value accumulated at the No. 2 generator, the DC system, and the load of the induction motor, and the lower the transient voltage stability.

In a stable situation (Figure 6 as an example), the relative power angle swing range of No. 2 generator is far greater than that of the other two units, and the power angle is ahead. When the transient voltage instability occurs, although PSAT cannot continue to simulate due to the limitation of the DAE model due to the encounter with the singular surface, it can be seen from Figure 7 that the slip of the induction motor reaches a peak value and tends to decrease at 1.2s , that is, the load rotor of the induction motor has begun to accelerate, indicating that when encountering a singular surface, it is not because the induction motor cannot accelerate normally and the rotor is blocked, which causes the load voltage of the induction motor to become unstable, which leads to the voltage collapse of the entire system, so it also explains from the side The dominance of the reactive power recovery characteristics of the DC receiving-end converter system on the influence of transient voltage instability on the system.

In summary, in order to study the main influences of generators, high-voltage direct current transmission systems (HVDC) and motors on transient voltage stability, the present invention proposes a new analysis method to study the above-mentioned main dynamics from the perspective of generalized branch potential energy Effect of components on transient voltage stability. According to the change law of transient potential energy distribution in the network after the fault and the information of the stability margin, the dynamic recovery characteristics of the reactive power of each electrical equipment after the fault are used as the basic variable, and the evaluation index is established, and then the mechanism of the transient voltage instability of the power grid is established. for analysis. The time-domain simulation results are basically consistent with the analysis results of the method of the present invention, which verifies the effectiveness of the method.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (4)

1. a kind of power system dynamic element response characteristic is to transient voltage stability influence analysis method, it is characterized in that, described analysis method comprises the following steps: S1. Establish a mathematical model of the power system, and construct an energy function expression that can reflect the system model based on Lyapunov theory; S2. Judging transient voltage stability, judging transient voltage stability through power system bifurcation conditions and a constant energy surface constructed based on heuristically obtained voltage instability-type dominant unstable equilibrium points; S3. According to the energy function expression constructed in step S1, extract the part related to the dynamic power element, and establish the potential energy component function of each dynamic element, wherein the dynamic element includes a generator, a high-voltage direct current transmission system, and an induction motor ; S4. During the fault period, the power system injects a large amount of energy into the grid, and the increase in the generator speed leads to an increase in kinetic energy. After the fault is cleared, the total energy is conserved, and the kinetic energy is gradually converted into the potential energy of each component and transmission line along the power network. With the increase of kinetic energy Oscillation changes, the potential energy of each dynamic element gradually increases and is accompanied by a certain oscillation, the dynamic element with the largest increase in potential energy will receive a greater energy impact, and use the first half of the potential energy oscillation curve where the maximum potential energy of each dynamic element is located. The potential energy increment of the wave is used to analyze the vulnerable areas of the power grid. 2. the power system dynamic element response characteristic according to claim 1 influences analysis method on transient voltage stability, it is characterized in that, described step S2 process is as follows: S201, constructing an energy function; S202, finding the dominant unstable equilibrium point; S203, find the critical energy Ucr; S204. Find the energy U at the moment of fault clearing; S205. Determine the magnitude of the energy U and the critical energy Ucr at the time of fault clearing, if the energy U at the time of fault clearing is greater than the critical energy Ucr, then determine that the transient voltage of the system is unstable; otherwise, continue to the next step; S206 , judging whether a singular surface is encountered, if so, judging that the transient voltage of the system is unstable, otherwise, judging that the system is stable. 3. The method for analyzing the influence of response characteristics of power system dynamic components on transient voltage stability according to claim 1, wherein in the step S4, the first half period wave of the potential energy oscillation curve where the potential energy maximum value of each dynamic component is located The potential energy increment is used to analyze the vulnerable areas of the power grid, and the impact of different system dynamic components on the transient voltage stability can be evaluated through the following evaluation indicators, as follows: Suppose the moment when the potential energy component of the equipment reaches the maximum value or the maximum value after the fault is T ₂ , and the potential energy component at the corresponding time is U ₂ , in this potential energy fluctuation cycle, the minimum value time before reaching the maximum value is T ₁ , and the corresponding time The potential energy component is U ₁ , then the potential energy difference in this potential energy fluctuation cycle is ΔU=U ₂ -U ₁ , and the evaluation index is defined as follows: Evaluation index one: σ ₁ = ΔU/ΔQ Evaluation index two: σ ₂ ＝V(T ₂ )/ΔU Among them, ΔQ is the reactive power variation of the power equipment under the influence of dynamic recovery characteristics after a fault within the corresponding time period, and V(T ₂ ) is the voltage amplitude of the equipment connected to the bus at time T ₂ . 4. The method for analyzing the influence of the dynamic element response characteristics of the power system on transient voltage stability according to claim 1, wherein the dynamic element mathematical model and the energy function expression of the power system are as follows: The fourth-order generator model used is: The third-order induction motor model used is: The energy function expression of the power system with n generator nodes, N load nodes, two DC system converter station bus nodes, and only one balance node is: U＝U _AC +U _L1 +U _L2i +U _g +U _R +U _I +U _d +U _DC in: and have: E=[E ₁ ,…,E _n ] ^T , E _i =[E′ _qi E _fdi ]; T=blockdiag[T ₁ ,…,T _n ], A=blockdiag[A ₁ ,...,A _n ], B=blockdiag[B ₁ ,...,B _n ], Among them, the subscripts i and j represent the network bus node labels, i=1, 2,..., n+N+3, j=1, 2,..., n+N+3, ρ _i is to make B _i ^-1 T _i is a positive definite parameter, and for any non-zero matrix vector, there is x ^T B _i ^-1 T _i x>0, i=1, 2..., n; C=[C ₁ ,...,C _n ] ^T , C _i =[0 l]; U _DC ＝-V _I V _R B _IR cos(θ _I -θ _R ); In the above formula, when i=1, 2,...,n, ω _i is the generator speed, δ _i is the generator rotor angle, M _i is the generator inertia time constant, P _mi is the generator mechanical power, D _i is the damping coefficient, E′ _qi is the q-axis transient potential, X _di is the transient reactance of the generator, X′ _di is the sub-transient reactance of the generator, T′ _doi is the d-axis transient time constant, E _fdi is Excitation potential, P _ei is the electromagnetic power of the generator, μ _i is the feedback gain coefficient of the excitation controller, T _vi is the excitation control time constant, k _i is the linear coefficient related to the connected bus voltage in the first-order mathematical model of the excitation voltage, l _i is the control constant connected to the bus i to make the excitation of the generator positive; the subscript R represents the variable on the rectifier side, the subscript I represents the variable on the inverter side, and the voltage amplitude of the AC bus of _VR and V _I , P _dR +jQ _dR and P _dI + jQ _dI is the compensation power injected by the converter; when i=n+1, n+2,...,n+N+3, T′ _doi is the stator open circuit time constant, _Mi is the induction motor Inertial time constant, E′ _Li is the amplitude of the internal potential, X _r is the equivalent leakage reactance of the rotor winding, X _m is the mutual inductance of the stator and rotor, X _s is the leakage reactance of the stator winding, X′ _i is the transient reactance, and X _i is Synchronous reactance, δ _i is the power angle of the induction motor, s _i is the slip of the induction motor, T _mi is the electromagnetic torque of the induction motor, T _ei is the mechanical torque; U _AC is the AC network potential energy, U _L1 is the static load potential energy, U _L2i is the load potential energy of the induction motor connected to node i, U _g is the energy sum of all generators in the system, U _R is the potential energy of the DC rectifier side and the AC network interface, U _I is the potential energy of the DC inverter side and the AC network interface, and U _DC is the DC Potential energy between network nodes, U _d is the potential energy component formed by DC power exchange, V _i and V _j are the voltage amplitudes of bus labels i and j respectively, θ _i and θ _j are the voltage phase angles of bus labels i and j, respectively, Q _Li is the reactive power of the static load connected to the bus marked i, and P _Li is the active power of the static load connected to the bus marked i.