An emergency control strategy optimization method in a switch refusal scenario

Abstract

The application discloses an emergency control strategy optimization method in a switch refusal operation scene, determines an emergency control trigger criterion in a switch refusal operation scene after a fault, and divides the scene into two categories of system stability before switch refusal and system instability before switch refusal; the emergency control best action time is determined according to the direction of electromagnetic power mutation of an equivalent single-machine system caused by the emergency control; and the emergency control measure quantity is determined through time domain simulation at the emergency control best action time. The application analyzes the influence law of the emergency control action on transient stability in different switch refusal scenes, optimizes the emergency control action time and the emergency control quantity, improves the effect of the emergency control when the equipment protection switch refuses to operate, reduces the control strength, reduces the equipment risk and the system risk, and improves the system transient stability.

Description

Technical Field

[0001] This invention belongs to the field of power system automatic control technology, specifically relating to an emergency control strategy optimization method in the scenario of switch failure to operate. Background Technology

[0002] With the development of large-scale power grids operating over long distances and with AC / DC parallel operation, the safe and stable operation of the power grid relies increasingly on circuit breakers and secondary systems. Once a fault occurs in the AC system, and the main protection or circuit breaker fails to operate, it can cause damage to power system equipment and the risk of large-scale power outages. Circuit breaker failure to operate refers to a situation where a three-phase short-circuit fault occurs on a line, and both three-phase circuits trip. Because one phase circuit breaker fails to trip, the backup protection trips the faulty phase after a period of time. Since many substations currently use a 3 / 2 connection configuration for their main wiring, a situation where a three-phase fault occurs on one line in a series, and the intermediate circuit breaker fails to operate on one or all three phases, causing another line or component in the same series to trip, is called a serious fault where the intermediate circuit breaker fails to operate on one or all three phases. When a circuit breaker failure to operate leads to system instability, measures must be taken to prevent system collapse.

[0003] Emergency control is feedforward control implemented after a fault occurs to prevent system instability or widespread power outages. Most current control devices employ the traditional "offline budgeting, real-time matching" approach. This involves preparing a strategy table offline, using pre-defined operating conditions and disturbance scenarios as indexes for the decision table. Emergency control is implemented only after the faulty component's switch is confirmed to have tripped. However, following a fixed sequence of equipment protection followed by emergency control requires confirmation that the faulty equipment has been disconnected before emergency control can be executed. In scenarios where equipment protection switches fail to operate, the need for remote switch clearance increases both equipment and system risks, compromising the effectiveness of emergency control. For control scenarios with high time sensitivity, this significantly reduces the effectiveness of emergency control. Furthermore, if the pre-decision table does not consider scenarios where switches fail to operate, only corrective control can restore system stability. Therefore, it is necessary to implement safeguards against such faults and add corresponding safety and stability control strategies for switch failure scenarios. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide an optimization method for emergency control strategies in scenarios where a switch fails to operate.

[0005] Technical solution: The present invention provides an emergency control strategy optimization method for a switch refusal scenario, the method comprising the following steps:

[0006] (1) Determine the emergency control trigger criteria in the scenario of switch failure after fault, and divide the scenario into two categories: system stability before switch failure and system instability before switch failure.

[0007] (2) The optimal action time of emergency control is determined by using the direction of sudden change in electromagnetic power of the equivalent single-machine system through emergency control.

[0008] (3) Determine the amount of emergency control measures through time-domain simulation under the optimal action time of emergency control.

[0009] Preferably, in step (1), the typical offline operating conditions of the power system are obtained, a permanent three-phase fault of the line and main transformer of the 220 kV and above system is set, and a time-domain simulation is performed under the correct operation of the switch to obtain the conclusion of whether the system is stable or unstable.

[0010] After obtaining typical offline operating conditions of the power system, and setting up a three-phase permanent fault in the line and main transformer of the 220 kV and above system, a switch failure fault is set in the simulation. Time-domain simulation is performed without considering emergency control to obtain the conclusion of whether the system is stable or unstable under the switch failure scenario.

[0011] Preferably, the switch failure fault specifically refers to: a fault occurring at 0 seconds, t τ1 The main protection trips phases BC, phase A fails to operate, and then the failure protection outputs an alert. The switching time is t. τ2 Always trip adjacent switches to isolate faults. If one switch fails to operate, at t τ2 The faulty line or main transformer should be tripped immediately; if the intermediate switch fails to operate, then at t τ2 Always disconnect the faulty line or main transformer, in t τ2 At the same time, the switch trips, opening another circuit or component in the same series.

[0012] Preferably, when the switch operates correctly and the system is stable in the scenario of failure to operate, emergency control is not required;

[0013] The system is stable when the switch operates correctly, but becomes unstable when the switch fails to operate. In this case, emergency control measures are implemented to address the switch failure scenario. The emergency control trigger criterion in this scenario is t. τ1 Always display a switch failure signal;

[0014] If the system becomes unstable when the switch operates correctly, and also becomes unstable after the switch fails to operate, then emergency control measures are added for the switch failure scenario. The emergency control actions are performed in two rounds, with the trigger criteria being a short-circuit fault signal and t. τ1 Always switch off the signal indicating failure to operate.

[0015] Preferably, in step (2), when t is received τ1 When the switch failure signal is used as the emergency control trigger signal, the optimal action time for emergency control is determined based on the direction of the sudden change in electromagnetic power of the equivalent single-unit system caused by the emergency control. The specific method is as follows:

[0016] ΔT is the delay in receiving the short-circuit fault signal, and the emergency control time is within [t]. τ1 +ΔT,tτ2 Between +ΔT]; for emergency control time within [t] τ1 +ΔT,t τ2 ] and (t τ2 , t τ2 Time-domain simulations were performed on [+ΔT] respectively to obtain the equivalent single-machine electromagnetic power curves of the system;

[0017] If the emergency control time is within [t] τ1 +ΔT,t τ2 The equivalent single-unit electromagnetic power of the system suddenly increases at time (t). τ2 , t τ2 When the equivalent single-unit electromagnetic power of the system suddenly increases by +ΔT], the optimal emergency control action time t is then determined. EC For t τ1 +ΔT;

[0018] If the emergency control time is within [t] τ1 +ΔT,t τ2 The equivalent single-unit electromagnetic power of the system suddenly increases at time (t). τ2 , t τ2 When the system's equivalent single-unit electromagnetic power suddenly decreases by +ΔT], then by comparing the emergency control at t τ1 +ΔT、t τ2 The system stability margin during +ΔT implementation determines the optimal action time for emergency control.

[0019] If the emergency control time is within [t] τ1 +ΔT,t τ2 The equivalent single-machine electromagnetic power of the system undergoes a downward abrupt change at time (t). τ2 , t τ2 When the equivalent single-unit electromagnetic power of the system suddenly increases by +ΔT], the optimal emergency control action time t is then determined. EC For t τ2 ;

[0020] If the emergency control time is within [t] τ1 +ΔT,t τ2 The equivalent single-machine electromagnetic power of the system undergoes a downward abrupt change at time (t). τ2 , t τ2 When the system's equivalent single-unit electromagnetic power suddenly decreases by +△T], the optimal emergency control action time t at this time is... EC For t τ2 +△T.

[0021] Preferably, in step (2), when a short-circuit fault signal is received as an emergency control trigger signal, the optimal action time for emergency control is determined based on the direction of the sudden change in the equivalent single-unit system electromagnetic power caused by emergency control. The specific method is as follows:

[0022] △T is the delay for receiving the short-circuit fault signal, and the emergency control action time is in the range [△T, t]. τ1 The emergency control time is between [ΔT, t]; τ1 Perform time-domain simulation using +△T] to obtain the equivalent single-machine electromagnetic power curve of the system. If the equivalent single-machine electromagnetic power of the system suddenly increases at the moment of emergency control, then the optimal action time t for emergency control at this time is... EC1 Let ΔT be the value of the system's equivalent single-unit electromagnetic power; if the system's equivalent single-unit electromagnetic power suddenly decreases during the emergency control moment, then the optimal emergency control action time t is... EC1 For t τ1 +△T.

[0023] Preferably, in step (3), when the switch operates correctly, the system is stable; when the switch fails to operate, the system becomes unstable. Then, under the optimal emergency control time, time-domain simulation is performed according to the optimal emergency control time t. EC Emergency control measures are implemented until the system stabilizes. The emergency control quantity after the switch fails to operate is ΔP.

[0024] Preferably, in step (3), when the system becomes unstable when the switch operates correctly, and when the system also becomes unstable when the switch fails to operate, the measures for the two rounds of emergency control are calculated separately, and the specific methods are as follows:

[0025] (S1) Based on the correct operation of the switch, in the first round of optimal action time t of emergency control EC1 Under the condition that the switch is correct, the emergency control quantity is perturbed until the system stabilizes, and the first round of emergency control quantity is obtained as ΔP1.

[0026] (S2) Based on the situation of switch failure to operate, set a fault for switch failure to operate, and add a fault at t EC1 Implement emergency control with a value of ΔP1, based on the optimal emergency control action time t. EC Emergency control measures are implemented until the system stabilizes, and the second round of emergency control measures is obtained as ΔP2.

[0027] The Extended Equal Area Theory (EEAC) provides 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. It offers quantitative information on stability under large disturbances from an energy perspective, revealing that the essence of system instability lies in the inter-group oscillation energy of the dominant complementary group exceeding the corresponding energy barrier. This theory can guide the study of the impact of emergency control actions on transient stability under switch failure scenarios. Therefore, based on the extended equal area rule, analysis of the impact of emergency control time parameters on system stability shows that the direction of the electromagnetic power mutation of the equivalent generator differs after emergency control is implemented at different times, i.e., the delta-axis effect. For Hamiltonian systems, there is no p-axis effect. Therefore, the effect of implementing emergency control at different times depends on the delta-axis effect. When the electromagnetic power of the equivalent generator mutates upward after emergency control, it is a positive delta-axis effect, meaning that implementing emergency control in advance is beneficial to system stability; otherwise, it will be detrimental to system stability.

[0028] Beneficial effects: By analyzing the system stability after normal switch operation and switch failure, the emergency control action triggering criteria are obtained. Through a small amount of time-domain simulation, the direction of the electromagnetic power change of the equivalent generator after emergency control is determined, the optimal action time of emergency control is quickly obtained, and different rounds of emergency control quantities are formulated. This helps to improve the effect of emergency control when the equipment protection switch fails to operate, reduces the control intensity, reduces equipment risk and system risk, and improves the transient stability of the system. Attached Figure Description

[0029] Figure 1 This is a schematic diagram illustrating the workflow of the emergency control strategy optimization method for switch failure scenarios according to the present invention.

[0030] Figure 2 The diagram shows the system stability when the switch operates correctly, and the emergency control time in the scenario of system instability after the switch fails to operate, within [t]. τ1 +△T,t τ2 The electromagnetic power variation curve of the equivalent generator at that time;

[0031] Figure 3 The diagram shows the system stability when the switch operates correctly, and the emergency control time in the scenario of system instability after the switch fails to operate, within the range of (t). τ2 , t τ2 The electromagnetic power variation curve of the equivalent generator at +△T];

[0032] Figure 4 Emergency control time is within [t] when the system is unstable due to either correct or failed operation of the switch. τ1 +△T,t τ2 The electromagnetic power variation curve of the equivalent generator at that time;

[0033] Figure 5Emergency control time within (t) is required in scenarios where the system becomes unstable regardless of whether the switch operates correctly or fails to operate. τ2 , t τ2 The electromagnetic power variation curve of the equivalent generator at +△T]. Detailed Implementation

[0034] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0035] An optimization method for emergency control strategies in switch refusal scenarios, such as... Figure 1 As shown, the method includes the following steps:

[0036] Step 1: Divide the scenarios into two categories. Scenario 1: The system is stable when the switch operates correctly, and becomes unstable when the switch fails to operate. Scenario 2: The system is unstable whether the switch operates correctly or fails to operate. Determine the emergency control trigger criteria for the switch failure scenario after a fault, as follows:

[0037] Obtain typical offline operating conditions of the power system, set up three-phase permanent faults in the lines and main transformers of the 220 kV and above system, perform time-domain simulation under correct switching operation, and obtain the conclusion of system stability or instability.

[0038] Typical offline operating conditions of the power system were obtained. After a permanent three-phase fault in the line and main transformer of a 220 kV and above system, a switch failure fault was set, and a time-domain simulation was performed without considering emergency control. The switch failure fault was set up in the simulation as follows: the fault occurred at 0 seconds, and t... τ1 The main protection trips phases BC, phase A fails to operate, and then the failure protection trips, with the switching time being t. τ2 Trip adjacent switches to isolate the fault. If the adjacent switch fails to operate, at t τ2 Simply disconnect the faulty line or main transformer; if the intermediate switch fails to operate, in addition to... τ2 In addition to disconnecting the faulty line or main transformer, it should also be done at t τ2 The circuit or component in the same series as the tripped switch is then checked. This leads to a conclusion regarding whether the system is stable or unstable in the scenario where the switch fails to operate.

[0039] If the system is stable when the switch operates correctly and fails to operate, no emergency control is needed, and this method exits. If the system is stable when the switch operates correctly, but becomes unstable after the switch fails to operate, then emergency control measures for the switch failure scenario need to be added. The emergency control trigger criterion is t. τ1 The system is unstable when the switch operates correctly, and also unstable after the switch fails to operate. Therefore, emergency control measures are needed for the switch failure scenario. The emergency control actions are implemented in two rounds, triggered by a short-circuit fault signal and a timeout. τ1 The switch fails to operate signal.

[0040] Step 2: Use emergency control to determine the optimal action time of emergency control by making the direction of the sudden change in electromagnetic power of the equivalent single-machine system change.

[0041] When the system becomes unstable when the switch operates correctly, or when the system also becomes unstable after the switch fails to operate, emergency control requires two rounds. The first round of emergency control can be implemented upon receiving a short-circuit fault signal. At this time, the optimal timing for the first round of emergency control is determined based on the direction of the sudden change in electromagnetic power of the equivalent single-unit system caused by the emergency control. The specific method is as follows:

[0042] After receiving a short-circuit fault signal, emergency control requires a delay of ΔT, with the earliest action time being ΔT. Following the logic that emergency control can only be executed after the original faulty equipment has been disconnected, the latest emergency control action time is t. τ1 +ΔT, meaning the time for the first round of emergency control actions is within [ΔT, t] τ1 Between +△T], generally, t τ1 +△T <t τ2 .

[0043] Based on the assumption that the switch operates correctly, the emergency control time is within [△T, t]. τ1 Time-domain simulation was performed using +ΔT], and the equivalent single-unit electromagnetic power curve of the system was obtained using FASTEST software. If the equivalent single-unit electromagnetic power of the system suddenly increases at the moment of emergency control, then implementing emergency control earlier is more beneficial to system stability. The optimal action time t for the first round of emergency control is... EC1 Let ΔT be the value of the system's equivalent single-unit electromagnetic power; if the system's equivalent single-unit electromagnetic power suddenly decreases during emergency control, the optimal action time t for the first round of emergency control will be... EC1 For t τ1 +ΔT.

[0044] In the second round of emergency control, when the system is stable when the switch operates correctly but becomes unstable after the switch fails to operate, or when the system is unstable when the switch operates correctly but also becomes unstable after the switch fails to operate, both of these situations require obtaining t τ1 Emergency control can only be implemented when the switch fails to operate. The optimal action time for emergency control is determined based on the direction of the sudden change in electromagnetic power of the equivalent single-unit system caused by the emergency control. The specific method is as follows:

[0045] Emergency control at t τ1 Upon receiving an action signal, a delay of ΔT is required, with the earliest action time being t. τ1 +ΔT; According to the logic that emergency control can only be executed after the original faulty equipment is disconnected, the latest time for emergency control action is t. τ2 +ΔT, that is, the emergency control time is within [t] τ1 +ΔT,t τ2 Between +ΔT];

[0046] Emergency control time at [t]τ1 +ΔT,t τ2 ] and (t τ2 , t τ2 Time-domain simulation between +ΔT] was performed using FASTEST software to obtain the equivalent single-unit electromagnetic power curve of the system. If the equivalent single-unit electromagnetic power of the system suddenly increases at the moment of emergency control, then implementing emergency control earlier is more beneficial to system stability, and vice versa. The following situations exist:

[0047] Emergency control time is in [t] τ1 +△T,t τ2 The equivalent single-unit electromagnetic power of the system suddenly increases at time (t). τ2 , t τ2 When +ΔT] occurs, the equivalent single-unit electromagnetic power of the system suddenly increases, and the optimal action time t for emergency control is determined. EC For t τ1 +△T;

[0048] Emergency control time is in [t] τ1 +△T,t τ2 The equivalent single-unit electromagnetic power of the system suddenly increases at time (t). τ2 , t τ2 When +△T], the equivalent single-unit electromagnetic power of the system suddenly decreases downward. By comparing the emergency control at t, τ1 +△T、t τ2 The system stability margin during +△T implementation determines the optimal action time for emergency control.

[0049] Emergency control time is in [t] τ1 +△T,t τ2 The equivalent single-machine electromagnetic power of the system undergoes a downward abrupt change at time (t). τ2 , t τ2 When +△T] occurs, the equivalent single-unit electromagnetic power of the system suddenly increases, and the optimal action time t for emergency control is determined. EC For t τ2 ;

[0050] Emergency control time is in [t] τ1 +△T,t τ2 The equivalent single-machine electromagnetic power of the system undergoes a downward abrupt change at time (t). τ2 , t τ2 When +△T] occurs, the equivalent single-unit electromagnetic power of the system suddenly decreases downward, and the optimal action time t for emergency control is determined. EC For t τ2 +△T.

[0051] Step 3: Determine the emergency control measures through time-domain simulation under the optimal emergency control action time. The specific method is as follows:

[0052] The system is stable when the switch operates correctly; the system becomes unstable when the switch fails to operate, according to the optimal emergency control time t. EC Emergency control measures are implemented until the system stabilizes. The emergency control quantity after the switch fails to operate is ΔP.

[0053] The system becomes unstable when the switch operates correctly, and also when the switch fails to operate. Since two rounds of emergency control are required, the measures need to be calculated separately: Based on the scenario of correct switch operation, the optimal action time t for the first round of emergency control is determined. EC1 Under the condition that the switch is in good working order, the emergency control quantity is perturbed until the system stabilizes, and the first round of emergency control quantity is obtained as ΔP1; based on the case of switch failure, a fault for switch failure is set, and an additional step is added at t EC1 Implement emergency control with a value of ΔP1, based on the optimal emergency control action time t. EC Emergency control measures are implemented until the system stabilizes, and the second round of emergency control measures is obtained as ΔP2.

[0054] Taking a typical AC fault in the Honggou-Banqiao power grid under certain conditions as an example, and different switch failure scenarios, this paper analyzes the optimization of emergency control strategies under switch failure scenarios:

[0055] Fault 1 is a three-phase short circuit N-1 occurring on the Honggou-Banqiao I line at 0s, with a single-phase switch failing to operate. Phases BC trip at 0.1s, and the three phases trip via backup protection at 0.25s. Simultaneously, the Honggou-Banqiao II line in the same series trips, causing system instability. This scenario represents a situation where the system is stable when the switch operates correctly, but becomes unstable after the switch fails to operate. τ1 =0.1s,t τ2 =0.25s Since the original decision table did not consider this scenario of failure to operate, it is necessary to add a corresponding safety and stability control strategy for the scenario of switch failure to operate, ΔT = 0.1s.

[0056] The emergency control trigger criterion is that a switch failure signal is received at 0.1s. Time-domain simulations are required for emergency control times between [0.2, 0.25] and (0.25, 0.35]. Figure 2 and Figure 3 The figure shows the electromagnetic power changes of the equivalent generators in the system after emergency control was implemented at 0.2s and 0.35s, disconnecting the 2.8 million kW units at Ertan and Pubugou in Sichuan. It can be seen that the equivalent single-unit electromagnetic power of the system abruptly increases when the emergency control time is [0.2, 0.25], and abruptly decreases when it is (0.25, 0.35]. The system stability margins when emergency control is implemented at 0.2s and 0.35s are -24.86% and -27.15%, respectively. Therefore, the optimal action time t for emergency control can be obtained. EC=0.2s. Time-domain simulation was conducted by implementing emergency control at 0.2s. When the emergency control measures were increased to 3.8 million kilowatts, the system stabilized. Therefore, the required new emergency control strategy is: if the safety control device receives a switch failure signal at 0.1s, the Ertan and Pubugou units, totaling 3.8 million kilowatts, are shut down at 0.2s. Compared to the original safety control strategy, which did not consider failure to operate and relied solely on corrective control to restore system stability, this new strategy significantly improves the effectiveness of emergency control for fault 1.

[0057] Fault 2 occurs when an N-2 fault occurs at Honggou-Banqiao. After the equipment protection operates normally for 0.1 seconds, the power angle of the Sichuan main grid becomes unstable. Following the N-2 fault at Honggou-Banqiao, the Hongban I line trips normally for 0.1 seconds, but the BC phase of the Hongban II line trips for 0.1 seconds. The side switch fails to operate, and the failure protection trips the Hongban II line for 0.25 seconds, causing system instability. This scenario represents a situation where system instability occurs both after the switch operates correctly and after its failure to operate. τ1 =0.1s,t τ2 =0.25s, the safety and stability control strategy needs to be optimized in the scenario of switch failure, △T=0.1s.

[0058] After the N-2 fault occurs at Honggou-Banqiao, when the equipment protection operates normally for 0.1s, the first round of emergency control triggers a short-circuit fault signal at 0s. Time-domain simulation is performed on the emergency control time in the range [0.1, 0.2]. The equivalent generator electromagnetic power undergoes a sudden upward change. The optimal action time t for the first round of emergency control is... EC1 The time is 0.1s. During this time, the Ertan unit is disconnected, and emergency control perturbation is performed until the system stabilizes. The first round of emergency control is 2.2 million kilowatts.

[0059] The second round of emergency control is triggered when a switch failure signal is received at 0.1s. Based on the first round of emergency control that shuts down the 2.2 million kW unit at 0.1s, time-domain simulations need to be performed for emergency control times between [0.2, 0.25] and (0.25, 0.35]. Figure 3 The figure shows the electromagnetic power change curves of the equivalent generator in the system after the second round of emergency control was implemented at 0.2s and 0.35s, followed by the replacement of the 1,000 MW unit at Pubugou. It can be seen that when the emergency control time is between [0.2, 0.25], the equivalent single-unit electromagnetic power of the system abruptly increases upwards. Figure 4 As shown, the equivalent single-unit electromagnetic power of the system abruptly increases upwards at (0.25, 0.35], as... Figure 5 As shown, the optimal action time t for the second round of emergency control EC=0.2s. After the second round of emergency control measures shut down the 1.6 million kW units at Pubugou and Gongzui, the system stabilized. Therefore, the optimized emergency control strategy is: if the safety control device receives a fault signal at 0s, shut down the 2.2 million kW Ertan unit at 0.1s; if it receives a switch failure signal at 0.1s, supplementarily shut down the 1.6 million kW units at Pubugou and Gongzui at 0.2s.

[0060] Compared to the implementation plan of first protecting the equipment and then controlling the emergency, the emergency control requires waiting for all three phases to trip for 0.25 seconds, followed by a 100ms delay (0.35 seconds) to disconnect the 5.1 million kW unit system before it can return to stable operation. The two-round optimization strategy proposed in this patent saves 1.3 million kW of unit disconnection.

[0061] In summary, the emergency control strategy optimization method disclosed in this application for the switch failure scenario can greatly improve the emergency control efficiency and reduce the control cost by improving the emergency control trigger criteria in the switch failure scenario and using the direction of the equivalent single-machine electromagnetic power change caused by emergency control as a guide to optimize the emergency control time.

Claims

1. An emergency control strategy optimization method in a switch-refused scene, characterized in that: The method comprises the following steps: (1) determining an emergency control trigger criterion under a switch failure to act scenario, and dividing the scenario into two categories of system stability before switch failure to act and system instability before switch failure to act; When the system is stable under the scenarios of correct switch action and failure to act, the emergency control is not needed; The system is stable when the switch operates correctly, and the system is unstable when the switch fails to operate. Therefore, the emergency control measure under the condition of switch failure is supplemented, and the emergency control trigger criterion is the switch failure signal at the moment The system is unstable when the switch operates correctly, and the system is also unstable after the switch fails to operate. Therefore, the emergency control measure quantity under the supplementary switch failure scenario is two rounds of emergency control actions, and the trigger criteria are short-circuit fault signals and switch failure signals at different times, respectively. switch failure signals at different times. (2) determining an emergency control optimal action time according to an equivalent single-machine system electromagnetic power mutation direction by using the emergency control; The step (2) is when receiving When the time switch refuses to act as an emergency control trigger signal, the equivalent single-machine system electromagnetic power mutation direction determines the optimal action time of the emergency control according to the emergency control. The specific method is as follows: The emergency control time is between [t1, t2] for receiving the short-circuit fault signal; time-domain simulation is performed on the emergency control time in [t1, t2], [t2, t3] and [t3, t4] respectively, and the system equivalent single-machine electromagnetic power curve is obtained; , ] between; time-domain simulation is performed on the emergency control time in [t1, t2], [t2, t3] and [t3, t4] respectively, and the system equivalent single-machine electromagnetic power curve is obtained; , ] and ( , ] respectively, and the system equivalent single-machine electromagnetic power curve is obtained; If the emergency control time is in [ , ], the equivalent single-machine electromagnetic power of the system will suddenly increase, and if it is in ( , ), the equivalent single-machine electromagnetic power of the system will suddenly increase, and at this time, the optimal action time of the emergency control is . ​ If the emergency control time is in [ , ], the equivalent single-machine electromagnetic power of the system suddenly increases, and if it is in ( , ), the equivalent single-machine electromagnetic power of the system suddenly decreases, then the optimal emergency control action time is determined by comparing the system stability margin when the emergency control is implemented in , ;​ If the emergency control time is in [ , ], the equivalent single-machine electromagnetic power of the system suddenly decreases, and if it is in ( , ), the equivalent single-machine electromagnetic power of the system suddenly increases, then the optimal action time of the emergency control is . ​ If the emergency control time is in [ , ], the equivalent single-machine electromagnetic power of the system will suddenly decrease, and if the emergency control time is in ( , ), the equivalent single-machine electromagnetic power of the system will suddenly decrease, and at this time, the optimal action time of the emergency control is . ​ (3) determining an emergency control measure quantity by time domain simulation at the emergency control optimal action time.

2. The method of claim 1, wherein: In the step (1), the off-line typical operating conditions of the power system are acquired, the three-phase permanent faults of the system lines and main transformers of 220 kV and above are set, time domain simulation under correct switch action is performed, and a conclusion of system stability or instability is obtained; The off-line typical operating conditions of the power system are acquired, the three-phase permanent faults of the system lines and main transformers of 220 kV and above are set, switch failure to act faults are set in simulation, time domain simulation without considering the emergency control is performed, and a conclusion of system stability or instability under the switch failure to act scenario is obtained.

3. The method of claim 2, wherein: The switch refusal failure is specifically: 0 second failure occurs, The main protection action opens BC phase at the moment, A phase refuses to act, and then the loss of function protection action exports. The switch action time is in The adjacent switch is opened at the moment to isolate the failure. If the side switch refuses to act, the adjacent switch is opened at the moment to isolate the failure. The fault line or the main transformer is opened at the moment. If the middle switch refuses to act, the fault line or the main transformer is opened at the moment. The fault line or the main transformer is opened at the moment. If the middle switch refuses to act, the fault line or the main transformer is opened at the moment. The switch and the other line or element in the same string are simultaneously opened at the moment.

4. The method of claim 1, wherein: In the step (2), when a short-circuit fault signal is received as an emergency control trigger signal, the emergency control optimal action time is determined according to an equivalent single-machine system electromagnetic power mutation direction, and the specific method is as follows: To delay the reception of short-circuit fault signals, the emergency control action time is within [ , Between ]; for emergency control time within [ , Perform time-domain simulation to obtain the equivalent single-unit electromagnetic power curve of the system. If the equivalent single-unit electromagnetic power of the system suddenly increases during emergency control, then the optimal action time for emergency control at this moment is determined. for If the equivalent single-unit electromagnetic power of the system suddenly decreases during an emergency control moment, then the optimal action time for emergency control at this time is... for .

5. The method of claim 1, wherein: The step (3) is time-domain simulation at the best action time of the emergency control when the switch is correctly operated and the system is stable, and when the switch fails to operate and the system is unstable The emergency control measure is perturbed until the system is stable, and the emergency control amount after the switch fails to operate is obtained .

6. The method of claim 4, wherein the method further comprises: In the step (3), when the system is unstable under correct switch action and the system is also unstable under switch failure to act, the measure quantities of the two rounds of emergency control are calculated, and the specific method is as follows: (S1) Based on the correct action of the switch, the emergency control first round optimal action time is The emergency control amount perturbation under the correct switch condition is carried out until the system is stable, and the emergency control first round control amount is obtained ; (S2) based on the switch refusal, set the switch failure, and increase the emergency control amount is , the emergency control measures amount perturbation is performed according to the emergency control optimal action time , until the system is stable, and the emergency control second round control amount is .

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