Unified evaluation method, device and system for transient stability of power system

Abstract

This invention discloses a unified evaluation method, apparatus, and system for power system transient stability. The method includes: acquiring the difference between the equivalent single-unit electromagnetic power and mechanical power of the power system after only equipment protection actions; acquiring the sequence of actions of equipment protection and emergency control, and the difference between the equivalent single-unit electromagnetic power and mechanical power of the power system under different action sequences; determining a unified evaluation index for transient stability based on the extended equal area rule, considering the influence of the sequence of actions of equipment protection and emergency control on the direction and magnitude of the change in the difference between the equivalent single-unit electromagnetic power and mechanical power; and conducting evaluation based on the unified evaluation index for transient stability. This invention analyzes the influence of the implementation sequence of emergency control and equipment protection on the direction and magnitude of sudden changes in generator electromagnetic power. Based on the extended equal area rule, it distinguishes the changes in the acceleration and deceleration areas of the equivalent generator trajectory under different time sequences, and formulates different quantitative evaluation indices for transient stability to improve system transient stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of power system automatic control, and in particular relates to a method, device and system for uniformly evaluating transient stability of a power system. Background Art

[0002] The current "Technical Guidelines for Safety and Stability Control of Power Systems" (GB / T 26399-2011) classifies "when a short-circuit fault occurs in the power system, the inherent control equipment and relay protection devices of the power system quickly and accurately cut off the faulty components of the power system" as the first line of defense; and classifies "according to the pre-considered fault form and operation mode, according to the predetermined control strategy, the use of safety and stability control systems (devices) to implement control measures such as cutting the machine, cutting the load, and partial decoupling to prevent the system from losing stability" as the second line of defense. Generally speaking, emergency control is implemented after the switch of the faulty component is confirmed to be tripped, that is, the equipment protection is activated. However, it will be detrimental to the stability of the system in scenarios with certain requirements for control time, or the equipment protection has the situation of refusal to operate or malfunction. The early action of emergency control will be beneficial to the stability of the system in certain scenarios. Therefore, it is necessary to study a unified transient stability evaluation method for the different action sequences of equipment protection and emergency control.

[0003] Regarding the impact of different emergency control times or equipment protection times on transient stability, the more common method is to use step-by-step perturbation to observe the changes in the system electrical quantities and stability, so as to determine the more serious moments. This method usually consumes a large amount of calculation. ZL201410798155.4 formulates performance indicators for different emergency control measures for the situation where emergency control is implemented after equipment protection, but does not consider the situation where emergency control is implemented in advance of equipment protection, especially before the equipment protection clears the short-circuit fault, the change in the electromagnetic power of all generators except the cut-off unit is no longer equal to the electromagnetic power of the cut-off unit, and the calculation of the performance indicators of emergency control measures no longer conforms to the situation where emergency control is implemented after equipment protection. It is urgent to formulate a unified quantitative indicator of transient stability based on the direction and size of the mutation of the equivalent single-machine electromagnetic power after the implementation of emergency control. Summary of the invention

[0004] In view of the above problems, the present invention proposes a unified evaluation method, device and system for transient stability of power system. By analyzing the influence of emergency control before and after equipment protection on the sudden change direction and size of electromagnetic power of generator, based on the extended equal area law, the changes of acceleration area and deceleration area of ​​equivalent generator trajectory under different time sequences are distinguished, and different transient stability quantitative evaluation indicators are formulated, which is helpful to formulate a coordination plan of emergency control and equipment protection, improve the emergency control effect, and improve the transient stability of the system.

[0005] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0006] In a first aspect, the present invention provides a unified evaluation method for transient stability of a power system, comprising:

[0007] Obtain the difference between the equivalent single-machine electromagnetic power and mechanical power of the power system after only the equipment protection is actuated;

[0008] Obtain the action sequence of equipment protection and emergency control, as well as the difference between the equivalent single-machine electromagnetic power and mechanical power of the power system under different action sequences;

[0009] Based on the extended equal area law, the unified transient stability evaluation index is determined according to the influence of the sequence of equipment protection and emergency control on the change direction and magnitude of the difference between the equivalent single-machine electromagnetic power and mechanical power.

[0010] Based on the unified transient stability evaluation index, a unified evaluation of power system transient stability is performed.

[0011] Optionally, obtaining the difference between the equivalent single-machine electromagnetic power and mechanical power of the system after only the equipment protection action is performed comprises the following steps:

[0012] According to the typical offline operating conditions and expected faults of the power system, the equipment protection action is performed without considering emergency control and only considering fault interruption;

[0013] If the power system is transiently unstable at this time, the extended equal area method is used to obtain the difference φ between the equivalent single-machine electromagnetic power and mechanical power of the power system.

[0014] Optionally, after different action sequences of equipment protection and emergency control, the difference between the equivalent single-machine electromagnetic power and mechanical power of the power system may have different mutation directions and sizes at the moment of emergency control.

[0015] Optionally, the obtaining of the sequential action sequence of equipment protection and emergency control, and the difference between the equivalent single-machine electromagnetic power and mechanical power of the power system under different action sequences, comprises the following steps:

[0016] When encountering a DSP point, based on the typical operating mode data of the power grid and expected faults, as well as the different action sequences of equipment protection and emergency control, for the situations where emergency control is before and after equipment protection, the equivalent generator image trajectory of the power system is obtained based on the extended equal area law, and the difference between the equivalent single-machine electromagnetic power and mechanical power is calculated.

[0017] Optionally, for the case where equipment protection is first adopted and then emergency control is implemented after a fault, the corresponding transient stability evaluation index γ' is calculated as follows:

[0018]

[0019] Where ΔA dec ' is the deceleration area increased after the emergency control is implemented compared with the single machine with the same value of equipment protection only; A inc is the equivalent single-machine acceleration area after equipment protection only; ΔP is the emergency control quantity, in units of per-unit value; δ DSP ,δ DSP ' are the rotor angles of the equivalent single-machine DSP points after only equipment protection and after equipment protection and emergency control respectively; δ ec ' is the equivalent single-machine rotor angle at the time of emergency control; P' e , P' m To implement emergency control after taking equipment protection measures, the equivalent single-machine electromagnetic power and mechanical power, and satisfy φ'=P' e -P' m .

[0020] Optionally, for the case where emergency control is first adopted and then equipment protection is implemented after a fault, the corresponding transient stability evaluation index γ" is calculated as follows:

[0021]

[0022] Where ΔA dec ” is the deceleration area increased by the equivalent single machine after the emergency control is activated first and the equipment protection is activated later; δ τ ”、δ ec ”、δ DSP "respectively, the equivalent single-machine equipment protection moment after emergency control is first actuated, equipment protection is then actuated, the emergency control moment, and the equivalent single-machine rotor angle at the DSP point; P" e ,P” m The emergency control is activated first, and the equipment protection is activated later, and the single machine electromagnetic power and mechanical power are equal, and φ”=P” is satisfied. e -P" m .

[0023] In a second aspect, the present invention provides a unified evaluation device for transient stability of a power system, comprising:

[0024] The first acquisition module is used to obtain the difference between the equivalent single-machine electromagnetic power and mechanical power of the power system after only the equipment protection action;

[0025] The second acquisition module is used to obtain the action sequence of equipment protection and emergency control, as well as the difference between the equivalent single-machine electromagnetic power and mechanical power of the power system under different action sequences;

[0026] The module for determining the unified transient stability evaluation index is used to determine the unified transient stability evaluation index based on the extended equal area law and the influence of the sequence of equipment protection and emergency control on the change direction and change magnitude of the difference between the equivalent single-machine electromagnetic power and mechanical power;

[0027] The evaluation module is used to perform a unified evaluation of the transient stability of the power system based on the unified transient stability evaluation index.

[0028] Optionally, obtaining the difference between the equivalent single-machine electromagnetic power and mechanical power of the system after only the equipment protection action is performed comprises the following steps:

[0029] According to the typical offline operating conditions and expected faults of the power system, the equipment protection action is performed without considering emergency control and only considering fault interruption;

[0030] If the power system is transiently unstable at this time, the extended equal area method is used to obtain the difference φ between the equivalent single-machine electromagnetic power and mechanical power of the power system.

[0031] 13. Optionally, the acquisition of the sequential action sequence of equipment protection and emergency control, and the difference between the equivalent single-machine electromagnetic power and mechanical power of the power system under different action sequences, includes the following steps:

[0032] When encountering a DSP point, based on the typical operating mode data of the power grid and expected faults, as well as the different action sequences of equipment protection and emergency control, for the situations where emergency control is before and after equipment protection, the equivalent generator image trajectory of the power system is obtained based on the extended equal area law, and the difference between the equivalent single-machine electromagnetic power and mechanical power is calculated.

[0033] Optionally, for the case where equipment protection is first adopted and then emergency control is implemented after a fault, the corresponding transient stability evaluation index γ' is calculated as follows:

[0034]

[0035] Where ΔA dec ' is the deceleration area increased after the emergency control is implemented compared with the single machine with the same value of equipment protection only; A inc is the equivalent single-machine deceleration area after equipment protection only; ΔP is the emergency control quantity, in units of per-unit value; δ DSP , δ DSP ' are the rotor angles of the equivalent single-machine DSP points after only equipment protection and after equipment protection and emergency control respectively; δ ec ' is the equivalent single-machine rotor angle at the time of emergency control; P' e , P' m To implement emergency control after taking equipment protection measures, the equivalent single-machine electromagnetic power and mechanical power, and satisfy φ'=P'e -P' m . .

[0036] Optionally, for the case where emergency control is first adopted and then equipment protection is implemented after a fault, the corresponding transient stability evaluation index γ" is calculated as follows:

[0037]

[0038] Where ΔA dec ” is the deceleration area increased by the equivalent single machine after the emergency control is activated first and the equipment protection is activated later; δ τ ”、δ ec ”、δ DSP "respectively, the equivalent single-machine equipment protection moment after emergency control is first actuated, equipment protection is then actuated, the emergency control moment, and the equivalent single-machine rotor angle at the DSP point; P" e ,P” m The emergency control is activated first, and the equipment protection is activated later, and the single machine electromagnetic power and mechanical power are equal, and φ"=P e ”-P m ”.

[0039] In a third aspect, the present invention provides a unified evaluation system for transient stability of a power system, including a storage medium and a processor;

[0040] The storage medium is used to store instructions;

[0041] The processor is configured to operate according to the instructions to execute the steps of the method according to any one of the first aspects.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] The present invention analyzes the influence of the sequence of equipment protection and emergency control actions on the transient stability of the system, analyzes the influence of the implementation of emergency control before and after equipment protection on the direction and size of the sudden change of the electromagnetic power of the generator, and based on the extended equal area law, distinguishes the changes in the acceleration area and deceleration area of ​​the equivalent generator trajectory under different time sequences, and formulates a unified transient stability quantitative evaluation index. The present invention can reduce the number of trials and calculations for the actual optimization of the emergency control action time, improve the efficiency and reliability of the emergency control, and enhance the effectiveness and real-time performance of the safe and stable control of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments and in conjunction with the accompanying drawings, wherein:

[0045] Figure 1It is a schematic flow chart of an embodiment of a unified transient stability evaluation method considering the timing of equipment protection and emergency control actions of the present invention;

[0046] Figure 2 Shown is a schematic diagram of a simple power system;

[0047] Figure 3 The figure shows the power difference curve under different equipment protection and emergency control action sequences in a short-circuit fault application example;

[0048] Figure 4 The figure shows the power difference curve under different equipment protection and emergency control action timing in another short circuit fault application example. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0050] The application principle of the present invention is described in detail below in conjunction with the accompanying drawings.

[0051] The extended equal area theory (EEAC) gives the necessary and sufficient conditions for transient stability of non-autonomous nonlinear multi-machine power systems through the complementary group center of inertia-relative motion (CCCOI-RM) transformation, and gives quantitative information on large disturbance stability from an energy perspective, revealing that the essence of system instability lies in the fact that the inter-group oscillation energy of the dominant complementary group is greater than the corresponding energy barrier, which can guide the study of the influence of equipment protection and emergency control action sequence on transient stability.

[0052] Therefore, the present invention proposes: obtaining the difference between the equivalent single-machine electromagnetic power and mechanical power of the system after only the equipment protection action; obtaining the order of equipment protection and emergency control actions; obtaining the difference between the equivalent single-machine electromagnetic power and mechanical power of the system after different action orders of equipment protection and emergency control; based on the extended equal area rule, according to the order of equipment protection and emergency control actions, the change direction and change magnitude of the difference between the equivalent single-machine electromagnetic power and mechanical power are determined to determine the unified transient stability evaluation index. In this way, the emergency control time after a short-circuit fault under different time difference ranges is formulated for emergency control when an actual short-circuit fault occurs.

[0053] Example 1

[0054] An embodiment of the present invention provides a unified evaluation method for transient stability of a power system, comprising:

[0055] Obtain the difference between the equivalent single-machine electromagnetic power and mechanical power of the power system after only the equipment protection is actuated;

[0056] Obtain the action sequence of equipment protection and emergency control, as well as the difference between the equivalent single-machine electromagnetic power and mechanical power of the power system under different action sequences;

[0057] Based on the extended equal area law, the unified transient stability evaluation index is determined according to the influence of the sequence of equipment protection and emergency control on the change direction and magnitude of the difference between the equivalent single-machine electromagnetic power and mechanical power.

[0058] Based on the unified transient stability evaluation index, a unified evaluation of power system transient stability is performed.

[0059] In a specific implementation of the embodiment of the present invention, the acquisition of the difference between the equivalent single-machine electromagnetic power and the mechanical power of the system after only the equipment protection action is taken includes the following steps:

[0060] According to the typical offline operating conditions and expected faults of the power system, the equipment protection action is performed without considering emergency control and only considering fault interruption;

[0061] If the power system is transiently unstable at this time, the extended equal area method is used to obtain the difference φ between the equivalent single-machine electromagnetic power and mechanical power of the power system, and then the next step is to obtain the sequence of actions for equipment protection and emergency control, as well as the difference between the equivalent single-machine electromagnetic power and mechanical power of the power system under different action sequences; otherwise, it is considered that no emergency control is required, and this method is terminated.

[0062] After the equipment protection and emergency control have different action sequences, the difference between the equivalent single-machine electromagnetic power and the mechanical power of the power system has different mutation directions and mutation sizes at the moment of emergency control, but all encounter dynamic saddle points, i.e., DSP points. To this end, in a specific implementation of an embodiment of the present invention, the acquisition of the action sequence of equipment protection and emergency control, as well as the difference between the equivalent single-machine electromagnetic power and the mechanical power of the power system under different action sequences, includes the following steps:

[0063] When encountering a dynamic saddle point, based on the typical operating mode data of the power grid and expected faults, as well as different action sequences of equipment protection and emergency control, for the situations before and after the emergency control of the equipment protection, the equivalent generator image trajectory of the power system is obtained based on the extended equal area law, and the difference between the equivalent single-machine electromagnetic power and mechanical power is calculated.

[0064] For the case where equipment protection is adopted first and then emergency control is implemented after a fault, the corresponding transient stability evaluation index γ' is calculated as follows:

[0065]

[0066] Where ΔA dec' is the deceleration area increased after the emergency control is implemented compared with the single machine with the same value of equipment protection only; A inc is the equivalent single-machine acceleration area after equipment protection only; ΔP is the emergency control quantity, in units of per-unit value; δ DSP ,δ DSP ' are the rotor angles of the equivalent single-machine DSP points after only equipment protection and after equipment protection and emergency control respectively; δ ec ' is the equivalent single-machine rotor angle at the time of emergency control; P' e , P' m To implement emergency control after taking equipment protection measures, the equivalent single-machine electromagnetic power and mechanical power, and satisfy φ'=P' e -P' m .

[0067] For the case where emergency control is adopted first and then equipment protection is implemented after a fault, the corresponding transient stability evaluation index γ" is calculated as follows:

[0068]

[0069] Where ΔA dec ” is the deceleration area increased by the equivalent single machine after the emergency control is activated first and the equipment protection is activated later; δ τ ”、δ ec ”、δ DSP "respectively, the equivalent single-machine equipment protection moment after emergency control is first actuated, equipment protection is then actuated, the emergency control moment, and the equivalent single-machine rotor angle at the DSP point; P" e ,P” m The emergency control is activated first, and the equipment protection is activated later, and the single machine electromagnetic power and mechanical power are equal, and φ”=P” is satisfied. e -P" m .

[0070] The larger the transient stability evaluation index is, the more beneficial the timing coordination scheme of equipment protection and emergency control action is to the transient stability of the system.

[0071] In the specific process, it is necessary to constantly judge whether the time differences of all equipment protection and emergency control actions have been completely calculated. If they have been calculated, the performance index information under the sequence and time difference of all equipment protection and emergency control actions is saved, and the method is terminated. Otherwise, the next action sequence and time difference are selected, and the previous steps are repeated to calculate the corresponding transient stability evaluation index for unified evaluation of transient stability of the power system.

[0072] Let's take a simple 9-node system as an example. Figure 2The system shown is obtained by modifying the standard 3-machine 9-node ring system. In order to study the control effect, the 3 machines are split into 11 machines, and each generator is adjusted to a classic second-order model). The transient stability emergency control strategy considering the time difference between equipment protection and emergency control action is analyzed. The short-circuit faults are bus-8-7 three-phase short-circuit faults. The equipment protection action fault disappears in 0.44s. The emergency control action times are 0.28s and 0.5s respectively. The emergency control measures are to cut off G21, G21, G21, and G21, totaling 136MW. The power difference curves of the equivalent single-machine system electromagnetic power and mechanical power after different emergency controls are shown in the figure. Figure 3 shown.

[0073] Bus-8-7 three-phase short circuit fault, 0.44s after the equipment protection action fault disappears, when the emergency control time is 0.28s, compared with only taking equipment protection, the power difference between the electromagnetic power and mechanical power of the equivalent single-machine system suddenly changes downward, making the acceleration area of ​​the system increase and the deceleration area increase. Substituting it into formula (2), the transient stability evaluation index γ" is 0.092; when the emergency control time is 0.5s, compared with only taking equipment protection, the power difference between the electromagnetic power and mechanical power of the equivalent single-machine system suddenly changes upward, making the deceleration area of ​​the system increase and the acceleration area unchanged. Substituting it into formula (1), the transient stability evaluation index γ' is 0.123, that is, the control effect of the emergency control time of 0.5s is better than that of the emergency control time of 0.28s.

[0074] Another short-circuit fault was a three-phase short-circuit fault in one of the bus-4-6 double-circuit lines. The equipment protection action disappeared at 0.38s and the line was cut off. The emergency control action times were 0.3s and 0.42s respectively. The emergency control measures were to cut off G21, G21, G21, and G21, totaling 136MW. The power difference curves of the equivalent single-machine system electromagnetic power and mechanical power after different emergency controls are shown in Figure 2. Figure 4 shown.

[0075] Bus-4-6 three-phase short circuit fault occurs, and the equipment protection action disappears after 0.38s. When the emergency control time is 0.3s, compared with only taking equipment protection, the power difference between the electromagnetic power and the mechanical power of the equivalent single-machine system suddenly changes upward, which increases the acceleration area and reduces the deceleration area of ​​the system. Substituting it into formula (2), the transient stability evaluation index γ" is 0.094; when the emergency control time is 0.42s, compared with only taking equipment protection, the power difference between the electromagnetic power and the mechanical power of the equivalent single-machine system suddenly changes upward, which increases the deceleration area and keeps the acceleration area unchanged. Substituting it into formula (1), the transient stability evaluation index γ' is 0.029, that is, the control effect of the emergency control time of 0.3s is better than that of the emergency control time of 0.42s.

[0076] Example 2

[0077] Based on the same inventive concept as that of Embodiment 1, an embodiment of the present invention provides a unified evaluation device for transient stability of a power system, comprising:

[0078] The first acquisition module is used to obtain the difference between the equivalent single-machine electromagnetic power and mechanical power of the power system after only the equipment protection action;

[0079] The second acquisition module is used to obtain the action sequence of equipment protection and emergency control, as well as the difference between the equivalent single-machine electromagnetic power and mechanical power of the power system under different action sequences;

[0080] The module for determining the unified transient stability evaluation index is used to determine the unified transient stability evaluation index based on the extended equal area law and the influence of the sequence of equipment protection and emergency control on the change direction and change magnitude of the difference between the equivalent single-machine electromagnetic power and mechanical power;

[0081] The evaluation module is used to perform a unified evaluation of the transient stability of the power system based on the unified transient stability evaluation index.

[0082] In a specific implementation of the embodiment of the present invention, the acquisition of the difference between the equivalent single-machine electromagnetic power and the mechanical power of the system after only the equipment protection action is taken includes the following steps:

[0083] According to the typical offline operating conditions and expected faults of the power system, the equipment protection action is performed without considering emergency control and only considering fault interruption;

[0084] If the power system is transiently unstable at this time, the extended equal area method is used to obtain the difference φ between the equivalent single-machine electromagnetic power and mechanical power of the power system.

[0085] After different action sequences of equipment protection and emergency control, the difference between the equivalent single-machine electromagnetic power and the mechanical power of the system has different mutation directions and mutation sizes at the moment of emergency control, but all encounter dynamic saddle points, i.e., DSP points; therefore, in a specific implementation of an embodiment of the present invention, the acquisition of the action sequence of equipment protection and emergency control, and the difference between the equivalent single-machine electromagnetic power and the mechanical power of the power system under different action sequences, includes the following steps:

[0086] When encountering a dynamic saddle point, based on the typical operating mode data of the power grid and expected faults, as well as different action sequences of equipment protection and emergency control, for the situations before and after the emergency control of the equipment protection, the equivalent generator image trajectory of the power system is obtained based on the extended equal area law, and the difference between the equivalent single-machine electromagnetic power and mechanical power is calculated.

[0087] For the case where equipment protection is adopted first and then emergency control is implemented after a fault, the corresponding transient stability evaluation index γ' is calculated as follows:

[0088]

[0089] Where ΔA dec ' is the deceleration area increased after the emergency control is implemented compared with the single machine with the same value of equipment protection only; A inc is the equivalent single-machine acceleration area after equipment protection only; ΔP is the emergency control quantity, in units of per-unit value; δ DSP ,δ DSP ' are the rotor angles of the equivalent single-machine DSP points after only equipment protection and after equipment protection and emergency control respectively; δ ec ' is the equivalent single-machine rotor angle at the time of emergency control; P' e , P' m To implement emergency control after taking equipment protection measures, the equivalent single-machine electromagnetic power and mechanical power, and satisfy φ'=P' e -P' m .

[0090] For the case where emergency control is adopted first and then equipment protection is implemented after a fault, the corresponding transient stability evaluation index γ" is calculated as follows:

[0091]

[0092] Where ΔA dec ” is the deceleration area increased by the equivalent single machine after the emergency control is activated first and the equipment protection is activated later; δ τ ”、δ ec ”、δ DSP "respectively, the equivalent single-machine equipment protection moment after emergency control is first actuated, equipment protection is then actuated, the emergency control moment, and the equivalent single-machine rotor angle at the DSP point; P" e ,P” m The emergency control is activated first, and the equipment protection is activated later, and the single machine electromagnetic power and mechanical power are equal, and φ”=P” is satisfied. e -P" m .

[0093] Example 3

[0094] An embodiment of the present invention provides a unified evaluation system for transient stability of a power system, including a storage medium and a processor;

[0095] The storage medium is used to store instructions;

[0096] The processor is used to operate according to the instructions to execute the steps of the method according to any one of Embodiment 1.

[0097] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A unified evaluation method for transient stability of a power system, characterized in that: include: Obtain the difference between the equivalent single-machine electromagnetic power and mechanical power of the power system after only the equipment protection is actuated; Obtain the action sequence of equipment protection and emergency control, as well as the difference between the equivalent single-machine electromagnetic power and mechanical power of the power system under different action sequences; Based on the extended equal area law, the unified transient stability evaluation index is determined according to the influence of the sequence of equipment protection and emergency control on the change direction and magnitude of the difference between the equivalent single-machine electromagnetic power and mechanical power. Based on the unified transient stability evaluation index, a unified evaluation of transient stability of the power system is performed; For the case where equipment protection is adopted first and then emergency control is implemented after a fault, the corresponding transient stability evaluation index γ' is calculated as follows: Where ΔA dec ' is the deceleration area increased after the emergency control is implemented compared with the single machine with the same value of equipment protection only; A inc is the equivalent single-machine acceleration area after equipment protection only; ΔP is the emergency control quantity, in units of per-unit value; δ DSP , δ DSP ' are the rotor angles of the equivalent single-machine DSP points after only equipment protection and after equipment protection and emergency control respectively; δ ec ' is the equivalent single-machine rotor angle at the time of emergency control; P' e , P′ m To implement emergency control after taking equipment protection measures, the equivalent single-machine electromagnetic power and mechanical power, and satisfy φ'=P' e -P′ m ; For the case where emergency control is adopted first and then equipment protection is implemented after a fault, the corresponding transient stability evaluation index γ" is calculated as follows: Where ΔA dec ” is the deceleration area increased by the equivalent single machine after the emergency control is activated first and the equipment protection is activated later; δ τ ”、δ ec ”、δ DSP ” are the equivalent single-machine equipment protection moment after emergency control is first actuated, equipment protection is then actuated, the emergency control moment, and the equivalent single-machine rotor angle at the DSP point; P e ”、P m " is the equivalent single-machine electromagnetic power and mechanical power after emergency control is activated first and equipment protection is activated later, and satisfies φ" = P e ”-P m ”.

2. A unified evaluation method for transient stability of a power system according to claim 1, characterized in that: The method of obtaining the difference between the equivalent single-machine electromagnetic power and the mechanical power of the system after only the equipment protection action is performed comprises the following steps: According to the typical offline operating conditions and expected faults of the power system, the equipment protection action is performed without considering emergency control and only considering fault interruption; If the power system is transiently unstable at this time, the extended equal area method is used to obtain the difference between the equivalent single-machine electromagnetic power and mechanical power of the power system.

3. A unified evaluation method for transient stability of a power system according to claim 2, characterized in that: After different action sequences of equipment protection and emergency control, the difference between the equivalent single-machine electromagnetic power and mechanical power of the power system will have different mutation directions and magnitudes at the moment of emergency control.

4. A unified evaluation method for transient stability of a power system according to claim 3, characterized in that: The method of obtaining the sequential action sequence of equipment protection and emergency control, and the difference between the equivalent single-machine electromagnetic power and mechanical power of the power system under different action sequences, includes the following steps: When encountering a DSP point, based on the typical operation mode data of the power grid and expected faults, as well as the different action sequences of equipment protection and emergency control, for the situations before and after the emergency control of the equipment protection, the equivalent generator image trajectory of the power system is obtained based on the extended equal area law, and the difference between the equivalent single-machine electromagnetic power and mechanical power is calculated.

5. A unified evaluation device for transient stability of a power system, characterized in that: include: The first acquisition module is used to obtain the difference between the equivalent single-machine electromagnetic power and mechanical power of the power system after only the equipment protection action; The second acquisition module is used to obtain the action sequence of equipment protection and emergency control, as well as the difference between the equivalent single-machine electromagnetic power and mechanical power of the power system under different action sequences; The module for determining the unified transient stability evaluation index is used to determine the unified transient stability evaluation index based on the extended equal area law and the influence of the sequence of equipment protection and emergency control on the change direction and change magnitude of the difference between the equivalent single-machine electromagnetic power and mechanical power; An evaluation module, used for performing a unified evaluation of transient stability of the power system based on the unified transient stability evaluation index; For the case where equipment protection is adopted first and then emergency control is implemented after a fault, the corresponding transient stability evaluation index γ' is calculated as follows: Where ΔA dec ' is the deceleration area increased after the emergency control is implemented compared with the single machine with the same value of equipment protection only; A inc is the equivalent single-machine acceleration area after equipment protection only; ΔP is the emergency control quantity, in units of per-unit value; δ DSP , δ DSP ' are the rotor angles of the equivalent single-machine DSP points after only equipment protection and after equipment protection and emergency control respectively; δ ec ' is the equivalent single-machine rotor angle at the time of emergency control; P' e , P′ m To implement emergency control after taking equipment protection measures, the equivalent single-machine electromagnetic power and mechanical power, and satisfy φ'=P' e -P′ m ; For the case where emergency control is adopted first and then equipment protection is implemented after a fault, the corresponding transient stability evaluation index γ" is calculated as follows: Where ΔA dec ” is the deceleration area increased by the equivalent single machine after the emergency control is activated first and the equipment protection is activated later; δ τ ”、δ ec ”、δ DSP ” are the equivalent single-machine equipment protection moment after emergency control is first actuated, equipment protection is then actuated, the emergency control moment, and the equivalent single-machine rotor angle at the DSP point; P e ”、P m " is the equivalent single-machine electromagnetic power and mechanical power after emergency control is activated first and equipment protection is activated later, and satisfies φ" = P e ”-P m ”.

6. A unified evaluation device for transient stability of a power system according to claim 5, characterized in that: The method of obtaining the difference between the equivalent single-machine electromagnetic power and the mechanical power of the system after only the equipment protection action is performed comprises the following steps: According to the typical offline operating conditions and expected faults of the power system, the equipment protection action is performed without considering emergency control and only considering fault interruption; If the power system is transiently unstable at this time, the extended equal area method is used to obtain the difference between the equivalent single-machine electromagnetic power and mechanical power of the power system.

7. A unified evaluation device for transient stability of a power system according to claim 6, characterized in that: The method of obtaining the sequential action sequence of equipment protection and emergency control, and the difference between the equivalent single-machine electromagnetic power and mechanical power of the power system under different action sequences, includes the following steps: When encountering a DSP point, based on the typical operation mode data of the power grid and expected faults, as well as the different action sequences of equipment protection and emergency control, for the situations before and after the emergency control of the equipment protection, the equivalent generator image trajectory of the power system is obtained based on the extended equal area law, and the difference between the equivalent single-machine electromagnetic power and mechanical power is calculated.

8. A unified evaluation system for transient stability of a power system, characterized in that: including storage media and processors; The storage medium is used to store instructions; The processor is configured to operate according to the instructions to execute the steps of the method according to any one of claims 1 to 4.

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