Main network adequacy improvement method and system considering static voltage safety boundary relaxation

Abstract

The invention discloses a main network adequacy improvement method and system considering static voltage safety boundary relaxation, and the method comprises the steps: obtaining a critical voltage value through employing a CPF method, carrying out the static stability margin evaluation, and determining a relaxation range; based on the obtained static voltage safety boundary and limit boundary, simulating a re-fluctuation scene of load increase after relaxation, and recording a limit boundary crossing system load sample and probability; solving the minimum load shedding capacity of the limit boundary after the voltage is prevented from crossing the relaxation through a prevention and control model, and describing the relaxation risk of the safety boundary in combination with the boundary crossing probability; obtaining an optimal boundary relaxation degree; the system comprises a relaxation evaluation module, a load simulation module, a system load module and a search optimization module. According to the method, the relaxation range of the static voltage safety boundary can be accurately obtained, the relaxation risk of the safety boundary is effectively represented, and the method has very important application value for the safety operation boundary which is strictly relaxed in power system optimization scheduling and effectively improving the overall adequacy.

Description

Technical Field

[0001] This invention relates to the field of smart distribution network control, and in particular to a method and system for improving the adequacy of the main grid considering the relaxation of the static voltage safety boundary. Background Technology

[0002] The continuous expansion of power systems, the increasing demand for electricity, and the large-scale integration of renewable energy have led to increased uncertainties and more complex operating conditions. Uncertain load fluctuations in extreme scenarios often cause system voltage to approach safe operating boundaries, resulting in insufficient overall system adequacy and frequent major power outages. Power system adequacy reflects the system's ability to meet user demands for power and electricity. Adequacy is divided into generation adequacy and transmission adequacy. The former includes the adequacy of installed capacity and the adequacy of dispatch reserves during operation, while the latter refers to the static and dynamic transmission capacity of transmission equipment to meet electricity demand and is closely related to transmission stability. Furthermore, power systems allow for a certain margin in receiving-end voltage deviation and static stability assessments. This ensures system safety and stability during normal operation, but becomes a limit to load increases when adequacy is insufficient. Therefore, conducting static voltage stability analysis and relaxing the static voltage safety boundary is of great significance for improving system adequacy. Summary of the Invention

[0003] Purpose of the invention: The purpose of this invention is to provide a method and system for improving the adequacy of the main grid considering the relaxation of the static voltage safety boundary.

[0004] Technical solution: The main grid adequacy improvement method considering the relaxation of static voltage safety boundary as described in this invention includes the following steps:

[0005] Step 1: Use the CPF method to obtain the critical voltage value and perform static stability margin assessment. Combine the lower limit of allowable voltage deviation and the low voltage load shedding threshold to characterize the static voltage safety boundary and the static voltage limit boundary, thereby determining the relaxation range.

[0006] Step 2: Based on the static voltage safety boundary and limit boundary obtained in Step 1, simulate the re-fluctuation scenario of increased load after relaxation, and record the load samples and probabilities of the system exceeding the limit boundary;

[0007] Step 3: Based on the load samples of the system that exceed the limit boundary obtained in Step 2, the minimum load shedding amount to avoid the voltage exceeding the relaxation limit boundary is obtained through the preventive control model, and the risk of relaxation of the safety boundary is characterized by combining the over-limit probability.

[0008] Step 4: Based on Step 3, use the sensitivity search method to search and optimize the sufficiency improvement effect and relaxation risk to obtain the optimal boundary relaxation degree.

[0009] Furthermore, the load-type CPF equation in step 1 is expressed as:

[0010] f(x, y, λ) = 0

[0011] Where x and y are the system's state variables and node-injected power, respectively, and λ represents the step size parameter in the set power growth direction. To simplify the analysis, it is assumed that all load nodes maintain their initial power factor, and all loads are added synchronously, expressed as:

[0012]

[0013] Among them, P Li P Li0 Q Li Q Li0 These are the node active and reactive power after equal step size growth and in the ground state, respectively, k Li The direction of node power growth is set.

[0014] Furthermore, in step 1, the static stability reserve coefficient is used as an evaluation index, as shown below:

[0015]

[0016] Among them, U z U represents the current voltage value of the node. c This represents the critical voltage value of the node, i.e., the critical voltage value corresponding to the SNB point.

[0017] Furthermore, during normal system operation in step 1, a 15% static reserve is maintained and the voltage values ​​at each node are constrained within 0.90-1.10 pu. The static reserve and voltage limits together constitute the voltage safety boundary.

[0018]

[0019] A decrease in static voltage reserve does not directly lead to voltage collapse, and a brief overshoot of node voltage will not cause system instability. The defined voltage critical value and the low-voltage load shedding threshold together constitute the stringent voltage boundary:

[0020]

[0021] The area between the safety boundary and the stringent boundary is the relaxation range.

[0022] Further, step 2 includes:

[0023] Under the load condition after the safety boundary is relaxed, the load variation is described using a Gaussian distribution, and the probability density function it follows is as follows:

[0024]

[0025] Where X is a random variable, σ is the active or reactive power of a node, and μ and σ are the expected value and standard deviation of the random variable, respectively.

[0026] Further, step 3 includes:

[0027] Based on the system load state exceeding the voltage limit obtained through sampling, voltage prevention control is performed by controlling the generator's active power, reactive power, and adjustable load resources in the system. The objective function for optimization is the total power adjustment C. n Minimum, including generator active power reactive power output and adjustable resource output

[0028]

[0029] Where: P i and Q i These are the active power output and reactive power output of the i-th generator, respectively. Γ represents the load reduction amount for the i-th load node; G and Γ P Let a1, a2, a3, b1, and c1 represent the generator node and load node in the system, respectively. a1, a2, a3, b1, and c1 are weighting coefficients. When establishing the reactive power output model, it is assumed that the reactive power output of the i-th generator is below a certain level. The output range is flexible; optimization is performed when the output exceeds the set value. i ) for Q i and The relevant logical functions.

[0030] Furthermore, in step 3, when the system performs optimized scheduling, it satisfies the power flow constraints of the power grid, as shown below:

[0031]

[0032]

[0033] Where: P Gi and Q Gi These represent the active and reactive power outputs of the generator at node i, respectively; P Li and Q Li These represent the active and reactive loads of node i, respectively; P ij P ki Q ij and Q ki These represent the active power and reactive power transmitted on the corresponding lines, respectively; r ki and x kiThese represent the resistance and reactance of the corresponding circuits, respectively; ki v is the square of the line. j It is the square of the node voltage.

[0034] Furthermore, in step 3, the voltages of each node in the system should meet upper and lower limit constraints, as shown in the following formula:

[0035]

[0036] in, Take the voltage value corresponding to the voltage safety boundary at node j; This represents the upper limit of the allowable voltage deviation at node j.

[0037] The active and reactive power output constraints of the generator and the operational constraints of adjustable resources are shown in the following formulas:

[0038]

[0039] in, and P represents the upper limit of active power output and the upper limit of reactive power output of the i-th generator, respectively. imin and P imax Let Q be the upper and lower limits of the adjustable resource active power at node i. imin and Q imax These are the upper and lower limits of the adjustable resource reactive power at node i, respectively.

[0040] Further, step 4 includes:

[0041] The static voltage safety boundary relaxation risk C′ is calculated based on the sampling probability of samples exceeding the limit boundary obtained in step 2 and the minimum power adjustment obtained from optimization in step 3. re :

[0042]

[0043] Among them, K f For the sample set that crosses the voltage limit boundary, P n Let C be the probability of sample n occurring. n To prevent control, the minimum power adjustment is obtained; the relaxation level is optimal when the total load connection obtained from the search is maximized. The overall objective function is as follows:

[0044]

[0045] Among them, e i ΔL represents the weighting coefficient for the power increase of node i in the system. i This represents the load increment after the node relaxes, and Δt represents the optimization time scale, taken as 5 minutes; C reThis represents the risk calculated using the risk characterization method under the current conditions.

[0046] The main grid adequacy enhancement system considering the relaxation of static voltage safety boundary as described in this invention includes the following steps:

[0047] The relaxation assessment module is used to obtain the critical voltage value using the CPF method and to assess the static stability margin. It combines the lower limit of the allowable voltage deviation and the low-voltage load shedding threshold to characterize the static voltage safety boundary and the static voltage limit boundary, thereby determining the relaxation range.

[0048] The load simulation module is used to simulate the re-fluctuation scenario of load increase after relaxation based on the static voltage safety boundary and the limit boundary, and to record the load samples and probabilities of the system when the limit boundary is exceeded.

[0049] The system load module is used to determine the minimum load shedding amount to avoid the voltage from exceeding the relaxation limit boundary based on the obtained system load samples that exceed the limit boundary through a preventive control model, and to characterize the risk of relaxation of the safety boundary by combining the over-limit probability.

[0050] The search optimization module is used to search and optimize the sufficiency improvement effect and relaxation risk based on the sensitivity search method to obtain the optimal boundary relaxation degree.

[0051] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: The present invention can accurately obtain the relaxation range of the static voltage safety boundary, effectively characterize the risk of safety boundary relaxation, and has very important application value for relaxing strict safety operation boundaries and effectively improving overall adequacy in power system optimization scheduling. Attached Figure Description

[0052] Figure 1 This is a flowchart of the present invention;

[0053] Figure 2 This is a diagram showing the determination of the static voltage safety boundary and limit boundary of the present invention;

[0054] Figure 3 The image shows the search results for the relaxation risk and adequacy improvement effect of the present invention. Detailed Implementation

[0055] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0056] like Figure 1 As shown, this invention proposes a method for improving the adequacy of the main grid considering the relaxation of the static voltage safety boundary, including:

[0057] Step S1: In practical systems, load-type CPF is a relatively mature and widely used analytical method for determining the static voltage stability of a power system by obtaining the PV curve. Its main equation can be expressed as:

[0058] f(x, y, λ) = 0 (1)

[0059] Where x and y are the system's state variables and node-injected power, respectively, and λ represents the step size parameter in the set power growth direction. To simplify the analysis, it is assumed that all load nodes maintain their initial power factor, and all loads are added synchronously. This process can be expressed as:

[0060]

[0061] Among them, P Li P Li0 Q Li Q Li0 These are the node active and reactive power after equal step size growth and in the ground state, respectively, k Li The direction of node power growth is set.

[0062] When λ is selected, the CPF will use the ground state as the initial point and perform "prediction-correction". The prediction stage uses the tangent method to find an approximate value for the next solution, which is then used as the initial value for the correction step. In the correction stage, the initial value is corrected by solving the augmented power flow equations with added parameters using Newton's method or a quasi-Newton method. This process searches for points on the PV curve according to the given power direction. The "inflection point" of the PV curve is the saddle node bifurcation (SNB) in the corresponding power growth direction. The voltage at this point represents the critical voltage point of the load node. The CPF can effectively track the static voltage stability margin under different parameters. To intuitively represent the static voltage stability margin, this paper uses the static stability reserve coefficient as an evaluation index, as shown below:

[0063]

[0064] Among them, U z U represents the current voltage value of the node. c This represents the critical voltage value of the node, i.e., the critical voltage value corresponding to the SNB point.

[0065] Under normal operating conditions, K V The requirement should be 10%–15% under post-accident operating conditions and special operating conditions, K V The value should not be less than 8%. In the static voltage instability analysis, this paper considers K to be... V When the static reserve is ≥15%, the voltage is stable, and K V When ≤0, the system voltage is considered unstable; when 0≤K, the voltage is unstable.V A static reserve coefficient of ≤15% is considered insufficient, indicating a risk of system instability. Furthermore, low-voltage load shedding is a common load management measure in power systems, primarily applied to supply-demand imbalances at low voltage levels. This paper considers the voltage threshold for triggering low-voltage load shedding to be 0.85 pu, and the allowable voltage deviation limit for the system to be 0.90-1.10 pu.

[0066] like Figure 2 As shown, to maintain static voltage safety during normal system operation, a 15% static reserve needs to be maintained and the voltage values ​​of each node need to be constrained within 0.90-1.10 pu. The static reserve and voltage limit together constitute the voltage safety boundary.

[0067]

[0068] A suitable reduction in static voltage reserve will not directly lead to voltage collapse, and a brief overshoot of node voltage will not cause system instability. The defined voltage critical value and the low-voltage load shedding threshold together constitute the stringent voltage boundary:

[0069]

[0070] The area between the safety boundary and the stringent boundary is the relaxation range.

[0071] Step S2: Under the load state after the safety boundary is relaxed, considering the uncertainty of load fluctuations at each node of the system, a Gaussian distribution is used to describe the load changes, and its probability density function is as follows:

[0072]

[0073] Where X is a random variable, which can be the active power or reactive power of a node, and μ and σ are the expected value and standard deviation of the random variable, respectively.

[0074] For load re-fluctuation after the safety boundary has been relaxed, if the static reserve is insufficient, the static reserve coefficient may further decrease or even lead to system voltage instability. If the current voltage exceeds the system limit, the voltage level may further decrease and trigger the low-voltage load shedding protection action. That is, samples that cause load re-fluctuation are obtained, the system load state and the number of occurrences of exceeding the voltage limit boundary are recorded, and the voltage overrun probability caused by load fluctuation under the base state is calculated from the number of voltage overrun samples and the total number of samples.

[0075] Step S3: Based on the system load state exceeding the voltage limit boundary obtained from the sampling in Step S2, voltage prevention control is performed by controlling the generator's active power, reactive power, and adjustable load resources in the system. The objective function for optimization is the total power adjustment C. n Minimum, including generator active power reactive power output and adjustable resource output

[0076]

[0077]

[0078] Among them, P i and Q i These are the active power output and reactive power output of the i-th generator, respectively. Γ represents the load reduction amount for the i-th load node; G and Γ P Let a1, α2, a3, b1, and c1 represent the generator node and load node in the system, respectively. a1, α2, a3, b1, and c1 are weighting coefficients. When establishing the reactive power output model, it is assumed that the reactive power output of the i-th generator is below a certain level. The output range is flexible; optimization is performed when the output exceeds the set value. i ) is the same as Q i and The relevant logical functions.

[0079] When performing optimized scheduling, the system must satisfy power flow constraints, as shown in the equation:

[0080]

[0081] Among them, P Gi and Q Gi These represent the active and reactive power outputs of the generator at node i, respectively; P Li and Q Li These represent the active and reactive loads of node i, respectively; P ij P ki Q ij and Q ki These represent the active power and reactive power transmitted on the corresponding lines, respectively; r ki and x ki These represent the resistance and reactance of the corresponding circuits, respectively; ki v is the square of the line. j It is the square of the node voltage.

[0082] The voltages at each node of the system should meet the upper and lower limits, as shown in the following formula:

[0083]

[0084] in, Take the voltage value corresponding to the voltage safety boundary at node j; This represents the upper limit of the allowable voltage deviation at node j.

[0085] The active and reactive power output constraints of the generator and the operational constraints of adjustable resources are shown in the following equation:

[0086]

[0087] in, and P represents the upper limit of active power output and the upper limit of reactive power output of the i-th generator, respectively. imin and P imax Let Q be the upper and lower limits of the adjustable resource active power at node i. imin and Q imax These are the upper and lower limits of the adjustable resource reactive power at node i, respectively.

[0088] Step S4: Calculate the static voltage safety boundary relaxation risk C based on the sample probability of exceeding the limit boundary obtained in Step S2 and the minimum power adjustment obtained in Step S3. re :

[0089]

[0090] Among them, K f For the sample set that crosses the voltage limit boundary, P n Let C be the probability of sample n occurring. n The minimum power adjustment amount obtained for prevention and control.

[0091] like Figure 3 As shown, in order to allow more loads to be connected due to voltage safety boundaries and improve the system's transmission adequacy, the static voltage safety boundary is relaxed. The risk after relaxation can be accurately characterized by calculating the voltage overshoot probability and subsequent preventative control measures. To improve adequacy while ensuring a good degree of relaxation, the system load state after relaxation needs to be searched and optimized by combining risk calculation and load growth. The degree of relaxation is optimal when the total load connected is maximized. The overall objective function is as follows:

[0092]

[0093] Among them, e i ΔL represents the weighting coefficient for the power increase of node i in the system. i This represents the load increment after the node relaxes, and Δt represents the optimization time scale, taken as 5 minutes; C re This represents the risk calculated using the risk characterization method under the current conditions.

[0094] This paper uses sensitivity analysis to evaluate the impact of load changes at each node in a system on the node voltage. Sensitivity analysis allows for the understanding and quantification of the system's response to various disturbances, thus providing important information for system optimization and control. The impact of load changes on voltage is shown below:

[0095]

[0096] Among them, S U，P This represents the voltage sensitivity to power, where U is the node voltage and P is the load power. After calculating the sensitivity of each node, the corresponding load is increased according to the sensitivity magnitude to perform an optimization search. In addition to satisfying the power flow constraints and generator output mentioned above, the voltage limit boundary constraints must also be met during the optimization process.

[0097]

[0098] in: Take the voltage value corresponding to the voltage limit boundary at node j; This represents the upper limit of the allowable voltage deviation at node j.

[0099] This invention proposes a method for improving the adequacy of the main grid considering the relaxation of the static voltage safety boundary. For situations where a strict voltage safety boundary leads to insufficient system adequacy, the CPF method is used to obtain the critical voltage value and perform static stability margin assessment. Combined with the lower bound of the allowable voltage deviation and the low-voltage load shedding threshold, the static voltage safety boundary and the static voltage limit boundary are characterized, thus simply and reliably determining the allowable relaxation range. Then, a relaxation risk characterization method is proposed. After relaxing the safety boundary, a load re-fluctuation scenario is simulated, and the probability of exceeding the limit boundary is statistically analyzed. The minimum power adjustment amount to avoid the voltage exceeding the relaxed limit boundary is obtained through a preventive control model. The relaxation risk of the safety boundary is characterized by the probability of exceeding the limit after relaxation and the preventive control results. Finally, a sensitivity search method is used to search and optimize the adequacy improvement effect and relaxation risk to obtain the optimal degree of boundary relaxation. Applying this method can accurately obtain the allowable relaxation range of the static voltage safety boundary and effectively characterize the safety boundary relaxation risk. It has significant application value for relaxing strict safety operation boundaries and effectively improving overall adequacy in power system optimal scheduling.

Claims

1. A method for improving the adequacy of the main grid considering the relaxation of the static voltage safety boundary, characterized in that, Includes the following steps: Step 1: Use the CPF method to obtain the critical voltage value and perform static stability margin assessment. Combine the lower limit of allowable voltage deviation and the low voltage load shedding threshold to characterize the static voltage safety boundary and the static voltage limit boundary, thereby determining the relaxation range. Step 2: Based on the static voltage safety boundary and limit boundary obtained in Step 1, simulate the re-fluctuation scenario of increased load after relaxation, and record the load samples and probabilities of the system exceeding the limit boundary; Step 3: Based on the load samples of the system that exceed the limit boundary obtained in Step 2, the minimum load shedding amount to avoid the voltage exceeding the relaxation limit boundary is obtained through the preventive control model, and the risk of relaxation of the safety boundary is characterized by combining the over-limit probability. Step 4: Based on Step 3, use the sensitivity search method to search and optimize the sufficiency improvement effect and relaxation risk to obtain the optimal boundary relaxation degree.

2. The method for improving grid adequacy considering relaxation of static voltage safety boundary as described in claim 1, characterized in that, The load-type CPF equation in step 1 is expressed as follows: f(x, y, λ) = 0 Where x and y are the system's state variables and node-injected power, respectively, and λ represents the step size parameter in the set power growth direction. To simplify the analysis, it is assumed that all load nodes maintain their initial power factor, and all loads are added synchronously, expressed as: Among them, P Li P Li0 Q Li Q Li0 These are the node active and reactive power after equal step size growth and in the ground state, respectively, k Li The direction of node power growth is set.

3. The method for improving grid adequacy considering relaxation of static voltage safety boundary as described in claim 1, characterized in that, In step 1, the static stable reserve coefficient is used as an evaluation indicator, as shown below: Among them, U z U represents the current voltage value of the node. c This represents the critical voltage value of the node, i.e., the critical voltage value corresponding to the SNB point.

4. The method for improving grid adequacy considering static voltage safety boundary relaxation as described in claim 1, characterized in that, During normal system operation in step 1, a 15% static reserve is maintained, and the voltage values ​​at each node are constrained within 0.90-1.10 pu. The static reserve and voltage limits together constitute the voltage safety boundary. A decrease in static voltage reserve does not directly lead to voltage collapse, and a brief overshoot of node voltage will not cause system instability. The defined voltage critical value and the low-voltage load shedding threshold together constitute the stringent voltage boundary: The area between the safety boundary and the stringent boundary is the relaxation range.

5. The method for improving grid adequacy considering static voltage safety boundary relaxation as described in claim 1, characterized in that, Step 2 includes: Under the load condition after the safety boundary is relaxed, the load variation is described using a Gaussian distribution, and the probability density function it follows is as follows: Where X is a random variable, σ is the active or reactive power of a node, and μ and σ are the expected value and standard deviation of the random variable, respectively.

6. The method for improving grid adequacy considering static voltage safety boundary relaxation as described in claim 1, characterized in that, Step 3 includes: Based on the system load state exceeding the voltage limit obtained through sampling, voltage prevention control is performed by controlling the generator's active power, reactive power, and adjustable load resources in the system. The objective function for optimization is the total power adjustment C. n Minimum, including generator active power reactive power output and adjustable resource output Where: P i and Q i These represent the active and reactive power outputs of the i-th generator, respectively; P i L Γ represents the load reduction amount for the i-th load node; G and Γ P Let a1, α2, a3, b1, and c1 represent the generator node and load node in the system, respectively. a1, α2, a3, b1, and c1 are weighting coefficients. When establishing the reactive power output model, it is assumed that the reactive power output of the i-th generator is below a certain level. The output range is flexible; optimization is performed when the output exceeds the set value. i ) for Q i and The relevant logical functions.

7. The method for improving grid adequacy considering static voltage safety boundary relaxation as described in claim 1, characterized in that, In step 3, when the system performs optimized scheduling, it satisfies the power flow constraints of the power grid, as shown below: Where: P Gi and Q Gi These represent the active and reactive power outputs of the generator at node i, respectively; P Li and Q Li These represent the active and reactive loads of node i, respectively; P ij P ki Q ij and Q ki These represent the active power and reactive power transmitted on the corresponding lines, respectively; r ki and x ki These represent the resistance and reactance of the corresponding circuits, respectively; ki v is the square of the line. j It is the square of the node voltage.

8. The method for improving grid adequacy considering static voltage safety boundary relaxation as described in claim 1, characterized in that, In step 3, the voltage of each node in the system should meet the upper and lower limit constraints, as shown in the following formula: in, Take the voltage value corresponding to the safety boundary of node k; This represents the upper limit of the allowable voltage deviation at node j. The active and reactive power output constraints of the generator and the operational constraints of adjustable resources are shown in the following formulas: Among them, P i max and P represents the upper limit of active power output and the upper limit of reactive power output of the i-th generator, respectively. imin and P imax Let Q be the upper and lower limits of the adjustable resource active power at node i. imin and Q imax These are the upper and lower limits of the adjustable resource reactive power at node i, respectively.

9. The method for improving grid adequacy considering static voltage safety boundary relaxation as described in claim 1, characterized in that, Step 4 includes: The static voltage safety boundary relaxation risk C is calculated based on the sampling probability of samples exceeding the limit boundary obtained in step 2 and the minimum power adjustment obtained from optimization in step 3. re : Among them, K f For the sample set that crosses the voltage limit boundary, P n Let C be the probability of sample n occurring. n To prevent control, the minimum power adjustment is obtained; the relaxation level is optimal when the total load connection obtained from the search is maximized. The overall objective function is as follows: Among them, e i ΔL represents the weighting coefficient for the power increase of node i in the system. i This represents the load increment after the node relaxes, and Δt represents the optimization time scale, taken as 5 minutes; C re This represents the risk calculated using the risk characterization method under the current conditions.

10. A main grid adequacy enhancement system considering static voltage safety boundary relaxation, characterized in that, Includes the following steps: The relaxation assessment module is used to obtain the critical voltage value using the CPF method and to assess the static stability margin. It combines the lower limit of the allowable voltage deviation and the low-voltage load shedding threshold to characterize the static voltage safety boundary and the static voltage limit boundary, thereby determining the relaxation range. The load simulation module is used to simulate the re-fluctuation scenario of load increase after relaxation based on the static voltage safety boundary and the limit boundary, and to record the load samples and probabilities of the system when the limit boundary is exceeded. The system load module is used to determine the minimum load shedding amount to avoid the voltage from exceeding the relaxation limit boundary based on the obtained system load samples that exceed the limit boundary through a preventive control model, and to characterize the risk of relaxation of the safety boundary by combining the over-limit probability. The search optimization module is used to search and optimize the sufficiency improvement effect and relaxation risk based on the sensitivity search method to obtain the optimal boundary relaxation degree.

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