A frequency control auxiliary decision-making method based on system frequency safety level

Abstract

The application relates to a frequency control auxiliary decision-making method based on a system frequency safety level, and belongs to the technical field of power system frequency control. In order to solve the problems that the current system has single frequency safety evaluation index and lacks clear corresponding relationship between the frequency safety level and the frequency control strategy, the application is based on three indexes of the maximum frequency difference margin, the maximum frequency change rate margin and the quasi-steady frequency deviation margin, and further establishes a system frequency safety comprehensive score model and a mapping relationship table between the comprehensive score model and the frequency safety level; for different safety levels, the preset system frequency modulation resource cooperative control strategy is matched; according to the real-time frequency data of the power grid, after disturbance occurs, the system frequency safety score is judged based on the system frequency safety comprehensive score model, the current system frequency safety level is determined according to the mapping relationship table; based on the system frequency safety level, the preset cooperative control strategy corresponding to the level is matched and executed, and auxiliary decision-making is realized.

Description

A frequency control auxiliary decision-making method based on system frequency security level Technical Field

[0001] This invention belongs to the field of power system frequency control technology, and specifically relates to a frequency control auxiliary decision-making method that combines system frequency security. Background Technology

[0002] With the increasing proportion of wind power, photovoltaic, and other new energy units connected to the grid, a high proportion of new energy has become a prominent feature of future power systems. The uncertainty and volatility of new energy output exacerbate the complexity of system frequency stability issues. Currently, the lack of clear classification of power system frequency security levels makes it difficult to formulate matching frequency regulation control strategies, further increasing frequency stability risks. Therefore, how to systematically classify frequency security levels under disturbances and formulate corresponding frequency control strategies based on these levels to achieve scientific and effective auxiliary decision-making has become one of the key issues that urgently need to be addressed to improve the frequency regulation capabilities of power systems.

[0003] Currently, there are several solutions for system frequency security assessment and frequency modulation control, such as:

[0004] The article "Online Frequency Security Analysis of Interconnected Power Grids Considering Inertia Adequacy and Frequency Change Rate" by Liu Xiangyu et al., Power System Technology, 2023, 47(05): 1780-1788, analyzes the influencing factors of frequency security using inertia and frequency change rate as indicators, and simultaneously assesses the level of system frequency security online, providing a decision-making basis for the safe operation of the power grid. However, the analysis process selects too few indicators, fails to include indicators such as frequency deviation, and lacks a clear classification of system frequency security levels.

[0005] The article "Two-Stage Multi-Level Early Warning of Power System Frequency Security Based on Improved Residual Network" by Li Lusu et al., Automation of Electric Power Systems, 2023, 47(01): 22-34, takes the frequency of the system inertia center as the research object and the magnitude of the system frequency deviation as the evaluation index. It divides the system frequency security level into three levels and uses an improved residual network to realize the system frequency security early warning, providing a basis for the selection of subsequent control strategies. However, the evaluation index only includes frequency deviation, which is too simplistic. At the same time, the three-level security level division lacks precision to some extent.

[0006] The "Emergency Control Strategy for 'Dual-High' Sending-End Power Grid Frequency Coordination Based on Multi-Type Resource Coordination" proposed by Zhong Zuhao et al., Automation of Electric Power Systems, 2023, 48(09): 3801-3811, aims to minimize the control cost under DC blocking and formulates a coordinated control strategy for multiple frequency regulation resources in the system. The strategy can meet frequency security constraints while coordinating various resources and fully utilizing the frequency regulation efficiency of various resources. However, its control strategy focuses on the coordination of multiple resources and lacks a clear division of frequency security levels. There is no clear relationship between the strategy and frequency security, making it unsuitable for auxiliary decision-making in system frequency control.

[0007] In summary, current system frequency security assessments often rely on single or limited indicators and lack refined security level classifications. Frequency control, on the other hand, focuses on the coordination of multiple resources and lacks a connection to frequency security. This results in security assessments considering only a few factors and being difficult to accurately map into control commands, thus failing to effectively support system frequency control decision-making. Therefore, there is an urgent need for a decision-making support method that can finely classify system frequency security levels and automatically match frequency control strategies according to different levels, in order to better ensure system frequency security. Summary of the Invention

[0008] This invention aims to address the problems in current systems where frequency security assessment indicators are singular and the relationship between frequency security levels and frequency control strategies is unclear.

[0009] A frequency control auxiliary decision-making method based on system frequency security level includes model building steps and auxiliary decision-making steps;

[0010] The steps for building the model include:

[0011] S1. Based on three indicators—maximum frequency difference margin, maximum frequency change rate margin, and transient steady-state frequency deviation margin—a multi-indicator weighted approach is used to establish a comprehensive scoring model for system frequency security.

[0012] S2. Classify the system security level based on the security comprehensive score determined by the system frequency security comprehensive scoring model, so as to establish a mapping relationship table between the comprehensive scoring model and the frequency security level; and pre-set the collaborative control strategy of each frequency modulation resource of the system for different security levels.

[0013] The steps for assisting decision-making include:

[0014] Based on real-time power grid frequency data, after a disturbance occurs, the system frequency security score is evaluated using a comprehensive system frequency security scoring model, and the current system frequency security level is determined based on a mapping table. Based on the system frequency security level, a preset collaborative control strategy corresponding to that level is matched and executed to achieve auxiliary decision-making.

[0015] Furthermore, the maximum frequency difference margin r1, the maximum frequency change rate margin r2, and the metastable state frequency deviation margin r3 are as follows:

[0016] (1)

[0017] In the formula, Δf max , Δf RoCoF,max and Δf ss These represent the maximum frequency difference, the maximum rate of frequency change, and the metastable frequency deviation, respectively; Δf lim , Δf RoCoF,lim and Δf ss,lim These are the frequency difference limit, the frequency change rate limit, and the metastable frequency deviation limit, respectively.

[0018] Furthermore, the process of establishing a comprehensive scoring model for system frequency security includes:

[0019] A1, Confirm The minimum value among the three indicators is denoted as ;

[0020] A2. Based on historical frequency dynamic data of the power grid, according to The total safety margin of the system is determined by using a multi-index weighted approach. ;

[0021] A3. Introducing the fusion coefficient β, its adaptive adjustment principle is as follows:

[0022] (5)

[0023] In the formula, β base ,β correct They represent the basic fusion coefficient and the correction term, respectively; k is the basic variation coefficient, and β is the basic fusion coefficient. max ,β min These represent the maximum and minimum fusion coefficients, respectively, both set manually based on actual conditions; dev(r) is... The difference between the average of the two larger indicators and the smallest indicator;

[0024] A4. Determine the comprehensive scoring model for system frequency security:

[0025] (8)

[0026] in The score is given by the comprehensive scoring model for system frequency security.

[0027] Furthermore, a multi-indicator weighted approach is used to determine the overall system safety margin. During the process, The weight is C iThe information content of the i-th indicator is calculated using the Critic objective weighting method.

[0028] Furthermore, the fusion coefficient β in step A3 needs to be subject to a range restriction: .

[0029] Furthermore, the process of pre-setting the coordinated control strategy for each frequency modulation resource in the system includes:

[0030] B1. Preset system frequency modulation control parameter optimization schemes, divided into economic, performance and environmental optimizations;

[0031] Based on three categories of indicators—economic, performance, and environmental—a weighted approach is used to determine the comprehensive evaluation indicators. The economic indicators include frequency regulation costs, operation and maintenance costs, and lifespan costs. The performance indicators include maximum frequency deviation, transient steady-state frequency deviation, and total skewness coefficient. The environmental indicators include renewable energy utilization rate and pollutant emissions.

[0032] Based on the system's frequency response analytical model and comprehensive evaluation index, the TOPSIS method is used to evaluate the system's frequency modulation efficiency under the influence of virtual inertia coefficient, frequency modulation dead zone, and modulation drop coefficient of each frequency modulation resource in the current system. The differential evolution algorithm is then used to iteratively optimize the comprehensive evaluation index value of the current frequency modulation parameters, thereby optimizing the frequency modulation parameters.

[0033] B2. Preset system coordinated frequency modulation control strategies under different frequency safety levels:

[0034] The system security levels corresponding to the ranges from largest to smallest comprehensive security scores are set as 5 levels, which are respectively denoted as system security levels I to V;

[0035] When the frequency drops: System safety level I, preset only thermal power units participate in frequency regulation; system safety level II, preset joint frequency regulation by thermal and new energy units, while optimizing frequency regulation parameters from an economic perspective; system safety level III, preset joint frequency regulation by thermal and new energy units, while optimizing frequency regulation parameters from an environmental perspective; system safety level IV, preset joint frequency regulation by thermal, new energy units, and energy storage units, optimizing control parameters from a frequency regulation performance perspective, while cutting off some interruptible loads; system safety level V, preset joint frequency regulation by thermal, new energy units, and energy storage units, optimizing frequency regulation parameters from a frequency regulation performance perspective, while cutting off interruptible loads and some loads, and taking pump-storage tripping measures.

[0036] When the frequency increases: At system safety level I, only thermal power units are pre-programmed to participate in frequency regulation; at system safety level II, thermal power and energy storage units are pre-programmed to jointly regulate the frequency, while optimizing regulation parameters from an economic perspective; at system safety level III, thermal power, new energy units, and energy storage units are pre-programmed to jointly regulate the frequency, while optimizing regulation parameters from an economic perspective; at system safety level IV, thermal power, new energy units, and energy storage units are pre-programmed to jointly regulate the frequency, optimizing regulation parameters from a regulation performance perspective, while also engaging some interruptible loads; at system safety level V, thermal power, new energy units, and energy storage units are pre-programmed to jointly regulate the frequency, optimizing regulation parameters from a regulation performance perspective, while also disconnecting some generator units.

[0037] Furthermore, the specific details of the three categories of indicators—economic, performance, and environmental—are as follows:

[0038] The economic indicators, including frequency regulation cost C1, operation and maintenance cost C2, and lifespan cost C3, are as follows:

[0039] (9)

[0040] In the formula, N represents the number of different types of frequency modulation resources, and iN represents the label of the frequency modulation resource. The cost of compensation per frequency modulation unit. This refers to the power adjustment of the frequency regulation unit iN during the frequency regulation operation period t. Let t be the duration of the frequency modulation (FM) runtime segment, and T be the number of FM runtime segments. and These are the operation and maintenance costs and life-cycle costs of thermal power units. It is the operation and maintenance cost of new energy units. and These are the operation and maintenance costs and lifespan costs of energy storage power stations;

[0041] The performance indicators include the maximum frequency deviation Δf nadir , Quasi-steady-state frequency deviation Δf qs and total adjustment coefficient δ sys Specifically as follows:

[0042] (11)

[0043] In the formula, The lowest frequency value, The initial frequency before the disturbance. For frequency stability value, This refers to the droop coefficient of the generator set iG. It is the total number of generator sets. The rated active power of the generator set iG, This is the start / stop flag position for the generator unit;

[0044] The environmental indicators include the utilization rate of new energy sources and the amount of pollutants emitted, as follows:

[0045] The utilization rate of new energy sources is the actual total output P of the new energy generating units during one cycle of frequency regulation. ENV To represent:

[0046] (12)

[0047] In the formula, N RE This represents the number of new energy generating units, with iRE being the corresponding unit number. The real-time power of the new energy unit iRE during frequency regulation operation segment t;

[0048] Pollutant emissions A ENV The expression is as follows:

[0049] (13)

[0050] In the formula, a, b, and c are the coefficients of the function relating pollutant emissions to power; This refers to the power adjustment amount of the iTH thermal power unit during frequency regulation operation within the specified time period t.

[0051] Furthermore, the aforementioned , , , and as follows:

[0052] (10)

[0053] In the formula, N TH N RE and N ST These represent the number of thermal power units, new energy units, and energy storage power stations, respectively. iTH, iRE, and iST are the corresponding unit or power station designations. The unit power generation operation and maintenance cost of thermal power units. , This represents the real-time power of the thermal power unit iTH during frequency regulation operation period t+1 and frequency regulation operation period t. The additional cost per megawatt of thermal power unit incurred due to hill climbing; For the unit power operation and maintenance cost of new energy generating units, The real-time power of the new energy unit iRE during frequency regulation operation segment t; It is the unit power operation and maintenance cost of the energy storage power station. , α represents the charging and discharging power of the iST energy storage power station during frequency regulation operation period t, respectively; α is the wear coefficient per unit frequency regulation power, and λ is the lifespan depreciation cost per unit frequency regulation throughput.

[0054] Furthermore, the five levels of system security corresponding to the range of comprehensive security scores from highest to lowest are set as follows:

[0055] A score in the range (0.7, 1) indicates a system security level of I; a score in the range (0.3, 0.7) indicates a system security level of II; a score in the range (0, 0.3) indicates a system security level of III; a score of 0 indicates a system security level of IV; and a score of -1 indicates a system security level of V.

[0056] Furthermore, the process of evaluating the system frequency security score based on the system frequency security comprehensive scoring model and determining the current system frequency security level according to the mapping relationship table includes:

[0057] Real-time power grid frequency data is collected using power grid monitoring devices such as PMUs; if a disturbance occurs during this period, the maximum rate of change of system frequency in the initial stage is measured. Then, the magnitude of the disturbance is calculated according to equation (14);

[0058] (14)

[0059] In the formula, The change in frequency Indicates time; ΔP L H represents the magnitude of the disturbance. sys The system's inertial time constant;

[0060] The frequency response analytical model of the disturbance input is used to obtain the maximum frequency deviation, maximum frequency change rate, and quasi-steady-state frequency deviation. Based on the three indicators of maximum frequency deviation margin, maximum frequency change rate margin, and quasi-steady-state frequency deviation margin, a comprehensive safety score is obtained based on the system frequency safety comprehensive scoring model. The corresponding frequency safety level is obtained according to the mapping relationship table between the comprehensive safety score and the safety level.

[0061] The beneficial effects of this invention are as follows:

[0062] To address the current situation where system frequency security assessment indicators are singular, level classifications are coarse, and the correlation between frequency security levels and frequency control strategies is unclear, this invention employs a multi-indicator comprehensive scoring model to achieve refined grading of system frequency security. Simultaneously, it links security assessment with control strategies, proposing a frequency control auxiliary decision-making method based on system frequency security levels. This method pre-defines control strategies for different levels, determines the security level through a mapping table between frequency security levels and scoring model scores, and automatically allocates control strategies to achieve auxiliary decision-making. This method can provide technical support for frequency regulation in new power systems. Attached Figure Description

[0063] Figure 1 is a schematic diagram of the comprehensive scoring model of the present invention;

[0064] Figure 2 is a schematic diagram of the system frequency security scoring and frequency level classification of the present invention;

[0065] Figure 3 is a schematic diagram of the automatic matching of the control strategy and safety level of the present invention;

[0066] Figure 4 shows the distribution of indicators under the three control schemes;

[0067] Figure 5 shows the power output curves of thermal power units under three control schemes.

[0068] Figure 6 shows the output curves of the photovoltaic unit under three control schemes;

[0069] Figure 7 shows the power output curves of the wind turbine under three control schemes;

[0070] Figure 8 shows the output curves of the energy storage unit under three control schemes;

[0071] Figure 9 shows the frequency curves under the three control schemes. Detailed Implementation

[0072] This invention proposes a frequency control auxiliary decision-making method based on system frequency security level. The method establishes a comprehensive scoring model using multiple indicators, realizes refined classification of system frequency security, links security assessment with frequency control strategies of various frequency modulation resources in the system, and presets control strategies under different levels. The security level is determined based on the mapping table between frequency security level and scoring model score, thereby automatically allocating control strategies and realizing auxiliary decision-making.

[0073] The auxiliary decision-making process of this invention is as follows: S1. Based on three indicators—maximum frequency deviation margin, maximum frequency change rate margin, and transient steady-state frequency deviation margin—and combining multi-indicator weighted theory and the bottleneck effect, a comprehensive scoring model for system frequency security is established; S2. A mapping table between the comprehensive scoring model and frequency security levels is established, and collaborative control strategies for each frequency regulation resource of the system are preset for different security levels; S3. Based on real-time frequency data of the power grid, after a disturbance occurs, the system frequency security score is evaluated through the comprehensive scoring model, and the current system frequency security level is determined according to the mapping table; S4. Based on the system frequency security level, the preset collaborative control strategy corresponding to that level is matched and executed to achieve auxiliary decision-making. The invention will now be described in detail with reference to the embodiments.

[0074] Specific implementation method one:

[0075] The frequency control auxiliary decision-making method based on system frequency security level described in this embodiment includes the following steps:

[0076] S1. Based on three indicators—maximum frequency margin, maximum frequency change rate margin, and transient steady-state frequency deviation margin—and combined with multi-indicator weighted theory and the weakest link effect, a comprehensive scoring model for system frequency security is established.

[0077] The expressions for the maximum frequency deviation margin r1, the maximum frequency change rate margin r2, and the metastable state frequency deviation margin r3 are as follows:

[0078] (1)

[0079] In the formula, Δf max , Δf RoCoF,max and Δf ss These represent the maximum frequency difference, the maximum rate of frequency change, and the metastable frequency deviation, respectively; Δf lim , Δf RoCoF,lim and Δf ss,lim These are the limits for frequency difference, rate of frequency change, and metastable frequency deviation. The specific limits are determined based on GB / T 26399-2011 and in conjunction with the actual system.

[0080] As shown in Figure 1, the steps for establishing the comprehensive scoring model are as follows:

[0081] A1. Considering the weakest link effect, based on equation (1), the minimum values ​​of the three indicators are calculated as follows:

[0082] (2)

[0083] A2. Based on the historical frequency dynamic data of the power grid, combined with Equation (1), the total safety margin of the system is determined by multi-index weighting, and the corresponding weights are determined by the Critic objective weighting method.

[0084] The overall system safety margin is as follows:

[0085] (3)

[0086] In the formula, w i The weight of the i-th indicator.

[0087] The weights of each margin were determined using the Critic objective weighting method as follows:

[0088] (4)

[0089] In the formula, C i The information content of the i-th indicator is calculated using the Critic objective weighting method.

[0090] A3. Introduce the fusion coefficient β and set its adaptive adjustment principle as follows:

[0091] (5)

[0092] In the formula, β base ,β correct They represent the basic fusion coefficient and the correction term, respectively; k is the basic variation coefficient, and β is the basic fusion coefficient. max ,β min These represent the maximum and minimum fusion coefficients, respectively, both set manually based on actual conditions; dev(r) is... The difference between the average of the two larger indicators and the smallest indicator is expressed as follows:

[0093] (6)

[0094] In the formula, r j This indicates the two larger safety margins among the three indicators.

[0095] Meanwhile, to prevent the adjustment of the fusion coefficient from causing the comprehensive scoring model to only reflect the weakest link effect or only reflect the multi-index weighting theory, the range of values ​​for the fusion coefficient needs to be limited:

[0096] (7)

[0097] A4. Based on steps A1 to A3, the comprehensive scoring model for system frequency security can be obtained as follows:

[0098] (8)

[0099] S2. Establish a mapping table between the system frequency comprehensive scoring model and the frequency security level, and preset the collaborative control strategy of each frequency modulation resource of the system for different security levels.

[0100] In this embodiment, the process of establishing the mapping relationship table between the comprehensive scoring model and the frequency security level includes:

[0101] A score in the range (0.7, 1) indicates a system security level of I; a score in the range (0.3, 0.7) indicates a system security level of II; a score in the range (0, 0.3) indicates a system security level of III; a score of 0 indicates a system security level of IV; and a score of -1 indicates a system security level of V.

[0102] It should be noted that this implementation method determines 5 frequency security levels based on a comprehensive scoring model. In other schemes, the number of frequency security levels can also be determined according to actual needs, such as 2 levels. The corresponding control scheme can also be designed according to the actual situation.

[0103] In this implementation system, the adjustable frequency generator units include thermal power, new energy (wind, solar), and energy storage units. Both the new energy units and the energy storage units employ virtual inertia and droop control. The specific preset steps for the system's collaborative control strategy under different safety levels are as follows:

[0104] B1. Preset system frequency modulation control parameter optimization schemes, divided into economic, performance and environmental optimizations;

[0105] Three categories of indicators are set: economic, performance, and environmental. Economic indicators include frequency regulation cost, operation and maintenance cost, and lifespan cost. Performance indicators include maximum frequency deviation, metasteady-state frequency deviation, and total droop coefficient. Environmental indicators include renewable energy utilization rate and pollutant emissions. The specific expressions for each indicator are as follows:

[0106] The frequency regulation cost C1, operation and maintenance cost C2, and lifespan cost C3 are as follows:

[0107] (9)

[0108] In the formula, N represents the number of different types of frequency modulation resources, and iN represents the label of the frequency modulation resource. The cost of compensation per frequency modulation unit. This refers to the power adjustment of the frequency regulation unit iN during the frequency regulation operation period t. Let t be the duration of the frequency modulation (FM) runtime segment, and T be the number of FM runtime segments. and These are the operation and maintenance costs and life-cycle costs of thermal power units. It is the operation and maintenance cost of new energy units. and These are the operation and maintenance costs and lifespan costs of the energy storage power station, respectively, as shown in the following expressions:

[0109] (10)

[0110] In the formula, N TH N RE and N ST These represent the number of thermal power units, new energy units, and energy storage power stations, respectively. iTH, iRE, and iST are the corresponding unit or power station designations. The unit power generation operation and maintenance cost of thermal power units. , This represents the real-time power of the thermal power unit iTH during frequency regulation operation period t+1 and frequency regulation operation period t. The additional cost per megawatt of thermal power unit incurred due to hill climbing; For the unit power operation and maintenance cost of new energy generating units, The real-time power of the new energy unit iRE during frequency regulation operation segment t; It is the unit power operation and maintenance cost of the energy storage power station. , α represents the charging and discharging power of the iST energy storage power station during frequency regulation operation period t, respectively; α is the wear coefficient per unit frequency regulation power, and λ is the lifespan depreciation cost per unit frequency regulation throughput.

[0111] Maximum frequency deviation Δf nadir , Quasi-steady-state frequency deviation Δf qs and total adjustment coefficient δ sys Specifically as follows:

[0112] (11)

[0113] In the formula, The lowest frequency value, The initial frequency before the disturbance. For frequency stability value, This refers to the droop coefficient of the generator set iG. It is the total number of generator sets. The rated active power of the generator set iG, This is the start / stop flag for the generator unit.

[0114] The utilization rate of new energy sources can be expressed as the actual total output P of the new energy unit within one cycle during frequency regulation. ENV To represent:

[0115] (12)

[0116] Pollutant emissions A ENV The expression is as follows:

[0117] (13)

[0118] In the formula, a, b, and c are the coefficients of the function relating pollutant emissions to power; This refers to the power adjustment amount of the iTH thermal power unit during frequency regulation operation within the specified time period t.

[0119] Based on the above indicators, when optimizing for economic reasons, the weight of the economic indicator is greater than that of the other two indicators; when optimizing for performance reasons, the weight of the performance indicator is greater than that of the other two indicators; when optimizing for environmental reasons, the weight of the environmental indicator is greater than that of the other two indicators. The specific weight values ​​are assigned using a subjective weighting method and can be determined according to the actual system situation. Combining the three types of indicators and their weights, a comprehensive evaluation index can be obtained.

[0120] Based on the frequency response of traditional synchronous machines and combined with the frequency response of new energy generating units, an analytical model of the system frequency response with a single inertia center is established. This model can quickly obtain the frequency response curve under system disturbances. Based on this model and comprehensive evaluation indicators, the TOPSIS method is used to evaluate the system frequency regulation efficiency under the influence of virtual inertia coefficients, frequency regulation dead zones, and droop coefficients of various frequency regulation resources in the current system. A differential evolution algorithm is then employed, using progressive steps of mutation, crossover, boundary condition processing, and selection to iteratively optimize the comprehensive evaluation index values ​​of the current frequency regulation parameters, thereby optimizing the frequency regulation parameters. The parameter optimization range is determined based on the grid connection standard GB / T40595-2021.

[0121] B2. Based on the parameter optimization scheme set in B1, the following system coordinated frequency modulation control strategies can be preset under different frequency safety levels:

[0122] When the frequency drops: System safety level I, pre-set only thermal power units participate in frequency regulation; System safety level II, pre-set joint frequency regulation of thermal and new energy units, while optimizing frequency regulation parameters from an economic perspective; System safety level III, pre-set joint frequency regulation of thermal and new energy units, while optimizing frequency regulation parameters from an environmental perspective; System safety level IV, pre-set joint frequency regulation of thermal, new energy units, and energy storage units, optimizing control parameters from a frequency regulation performance perspective, while disconnecting some interruptible loads; System safety level V, pre-set joint frequency regulation of thermal, new energy units, and energy storage units, optimizing frequency regulation parameters from a frequency regulation performance perspective, while disconnecting interruptible loads and some loads, and taking pump-storage tripping measures.

[0123] When the frequency increases: At system safety level I, only thermal power units are pre-programmed to participate in frequency regulation; at system safety level II, thermal power and energy storage units are pre-programmed to jointly regulate the frequency, while optimizing regulation parameters from an economic perspective; at system safety level III, thermal power, new energy units, and energy storage units are pre-programmed to jointly regulate the frequency, while optimizing regulation parameters from an economic perspective; at system safety level IV, thermal power, new energy units, and energy storage units are pre-programmed to jointly regulate the frequency, optimizing regulation parameters from a regulation performance perspective, while also engaging some interruptible loads; at system safety level V, thermal power, new energy units, and energy storage units are pre-programmed to jointly regulate the frequency, optimizing regulation parameters from a regulation performance perspective, while also disconnecting some generator units.

[0124] S3. Based on real-time power grid frequency data, after a disturbance occurs, the system frequency security score is evaluated based on the system frequency security comprehensive scoring model, and the current system frequency security level is determined based on the mapping relationship table.

[0125] As shown in Figure 2, the specific implementation process of evaluating the system frequency security score based on the system frequency security comprehensive scoring model and determining the current system frequency security level according to the mapping relationship table is as follows:

[0126] Real-time power grid frequency data is collected using power grid monitoring devices such as PMUs. If a disturbance occurs during this period, the maximum frequency change rate of the system in the initial stage can be measured, and the approximate disturbance size can be calculated according to equation (14). The disturbance is input into the frequency response analytical model to obtain the maximum frequency deviation, the maximum frequency change rate, and the transient steady-state frequency deviation. The corresponding three margin indices are calculated according to equation (1), and after scoring through the system frequency security comprehensive scoring model, the corresponding frequency security level is obtained according to the mapping relationship table between the comprehensive security score and the security level.

[0127] Maximum rate of change of frequency df / dt in the initial stage of the system t→0 The relationship between the magnitude of the disturbance and the magnitude of the disturbance can be expressed as:

[0128] (14)

[0129] In the formula, The change in frequency Indicates time; ΔP L H represents the magnitude of the disturbance. sys The system inertial time constant is obtained by aggregating the time of each unit in the system.

[0130] S4. Based on the system frequency security level, match and execute the preset collaborative control strategy corresponding to that level to achieve auxiliary decision-making.

[0131] As shown in Figure 3, the system frequency control strategy adopts the scheme preset in step S2, which will dynamically match the frequency safety level of the system after the disturbance occurs, thereby providing auxiliary decision-making for system frequency control.

[0132] Example: A DC blocking fault was simulated in the system using simulation software. According to step S3, the corresponding frequency safety level was determined to be Level V, and control scheme 3 was obtained through matching in step S4. A control group was set up to verify the effectiveness of the auxiliary decision-making method. Control scheme 1 and control scheme 2 were defined, where scheme 1 is an unspecified frequency regulation resource type, and all frequency regulation parameters use default parameters; scheme 2 is the corresponding strategy proposed in S2, but without parameter optimization. This yields a comparison of the system frequency response curves and the output of each frequency regulation resource under the three control schemes. Figure 4 shows a comparison of the distribution of economic, frequency regulation performance, and environmental indicators. Figures 5-8 show the output curves of thermal power units, photovoltaic units, wind turbine units, and energy storage units. Figure 9 shows the frequency curves under the three control schemes. Figures 4 and 9 show that control schemes 2 and 3, compared to scheme 1, achieved improvements of over 20% in maximum frequency deviation and transient and transient steady-state frequency indicators, indicating that they achieved a significant improvement in frequency safety at a certain economic cost, demonstrating outstanding cost-effectiveness. Scheme 3 further optimizes Scheme 2, reducing not only the maximum frequency deviation and the transient steady-state frequency offset, but also the economic cost. This scheme demonstrates excellent performance in dynamic response, economic operating efficiency, and system adaptability, providing a practical and feasible technical solution for the safe and stable operation of high-proportion renewable energy power systems.

[0133] The above examples of the present invention are merely illustrative of the computational model and process of the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is impossible to exhaustively list all possible implementations here. Any obvious variations or modifications derived from the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A frequency control auxiliary decision-making method based on system frequency security level, characterized in that, The process includes model building steps and decision support steps. The model building steps include: S1, establishing a comprehensive system frequency security scoring model based on three indicators: maximum frequency deviation margin, maximum frequency change rate margin, and quasi-steady-state frequency deviation margin, using a multi-indicator weighted approach; the maximum frequency deviation margin r1, maximum frequency change rate margin r2, and quasi-steady-state frequency deviation margin r3 are as follows: In the formula, Δf max , Δf RoCoF,max and Δf ss These represent the maximum frequency difference, the maximum rate of frequency change, and the metastable frequency deviation, respectively; Δf lim , Δf RoCoF,lim and Δf ss,lim These are the frequency difference limit, the frequency change rate limit, and the transient steady-state frequency deviation limit, respectively; the process of establishing a comprehensive scoring model for system frequency security includes: A1, determining... The minimum value among the three indicators is denoted as A2. Based on historical frequency dynamic data of the power grid, according to The total safety margin of the system is determined by using a multi-index weighted approach. A3. Introduce the fusion coefficient β, whose adaptive adjustment principle is as follows: In the formula, β base ,β correct They represent the basic fusion coefficient and the correction term, respectively; k is the basic variation coefficient, and β is the basic fusion coefficient. max ,β min These represent the maximum and minimum fusion coefficients, respectively, both set manually based on actual conditions; dev(r) is... The difference between the average of the two larger indicators and the smallest indicator; i=1,2,3. Corresponding representation A4. Determine the comprehensive scoring model for system frequency security: ,in The steps include: S1) Scoring the system frequency security comprehensive scoring model; S2) Dividing the system security level according to the comprehensive security score determined by the system frequency security comprehensive scoring model to establish a mapping relationship table between the comprehensive scoring model and the frequency security level; For different security levels, pre-setting collaborative control strategies for each frequency regulation resource of the system; The auxiliary decision-making steps include: Based on the real-time frequency data of the power grid, after a disturbance occurs, judging the system frequency security score based on the system frequency security comprehensive scoring model, and determining the current system frequency security level according to the mapping relationship table; Based on the system frequency security level, matching and executing the pre-set collaborative control strategy corresponding to the level to achieve auxiliary decision-making.

2. The frequency control auxiliary decision-making method based on system frequency security level according to claim 1, characterized in that, The overall system safety margin is determined using a multi-index weighted approach. During the process, The weight is C i The information content of the i-th indicator is calculated using the Critic objective weighting method.

3. The frequency control auxiliary decision-making method based on system frequency security level according to claim 1, characterized in that, The fusion coefficient β in step A3 needs to be subject to a range restriction: 。 4. A frequency control auxiliary decision-making method based on system frequency security level according to any one of claims 1 to 3, characterized in that, The process of pre-setting the coordinated control strategy for various frequency modulation resources in the system includes: B1. Pre-setting the optimization scheme for the frequency modulation control parameters of the system, which is divided into economic, performance, and environmental optimizations; Based on the three categories of indicators—economic, performance, and environmental—a weighted average is used to determine the comprehensive evaluation index; the economic indicators include frequency modulation cost, operation and maintenance cost, and lifespan cost; the performance indicators include maximum frequency deviation, transient steady-state frequency deviation, and total droop coefficient; and the environmental indicators include renewable energy utilization rate and pollutant emissions; Based on the system's frequency response analytical model and the comprehensive evaluation index, TOPSIS is used... The method is used to evaluate the system's frequency regulation efficiency under the influence of virtual inertia coefficients, dead zones, and droop coefficients of various frequency regulation resources in the current system. A differential evolution algorithm is used to iteratively optimize the comprehensive evaluation index value of the current frequency regulation parameters, thereby optimizing the frequency regulation parameters. B2. Preset system coordinated frequency regulation control strategies under different frequency safety levels: The system safety level corresponding to the intervals from largest to smallest safety comprehensive score is set to 5 levels, denoted as system safety levels I to V respectively. When the frequency drops: System safety level I, preset only thermal power units participate in frequency regulation; System safety level II, preset joint regulation of thermal power and new energy units. The system operates at frequency, with frequency regulation parameters optimized from an economic perspective. At system safety level III, joint frequency regulation by thermal power and new energy units is preset, with frequency regulation parameters optimized from an environmental perspective. At system safety level IV, joint frequency regulation by thermal power, new energy units, and energy storage units is preset, with control parameters optimized from a frequency regulation performance perspective, while some interruptible loads are disconnected. At system safety level V, joint frequency regulation by thermal power, new energy units, and energy storage units is preset, with frequency regulation parameters optimized from a frequency regulation performance perspective, while interruptible loads and some loads are disconnected, and pump-storage tripping measures are implemented. When the frequency rises: at system safety level I, only thermal power is preset... The generating units participate in frequency regulation; the system safety level is II, with pre-set joint frequency regulation of thermal power and energy storage units, while optimizing frequency regulation parameters from an economic perspective; the system safety level is III, with pre-set joint frequency regulation of thermal power, new energy units, and energy storage units, while optimizing frequency regulation parameters from an economic perspective; the system safety level is IV, with pre-set joint frequency regulation of thermal power, new energy units, and energy storage units, while optimizing frequency regulation parameters from a frequency regulation performance perspective, and simultaneously putting some interruptible loads into operation; the system safety level is V, with pre-set joint frequency regulation of thermal power, new energy units, and energy storage units, while optimizing frequency regulation parameters from a frequency regulation performance perspective, and simultaneously disconnecting some generating units.

5. The frequency control auxiliary decision-making method based on system frequency security level according to claim 4, characterized in that, The specific indicators for the three categories—economic, performance, and environmental—are as follows: The economic indicators, including frequency regulation cost C1, operation and maintenance cost C2, and lifespan cost C3, are as follows: In the formula, N represents the number of different types of frequency modulation resources, and iN represents the label of the frequency modulation resource. The cost of compensation per frequency modulation unit. This refers to the power adjustment of the frequency regulation unit iN during the frequency regulation operation period t. Let t be the duration of the frequency modulation (FM) runtime segment, and T be the number of FM runtime segments. and These are the operation and maintenance costs and life-cycle costs of thermal power units. It is the operation and maintenance cost of new energy units. and These are the operation and maintenance costs and lifespan costs of energy storage power stations; the performance indicators include the maximum frequency deviation Δf. nadir , Quasi-steady-state frequency deviation Δf qs and total adjustment coefficient δ sys Specifically as follows: In the formula, The lowest frequency value, The initial frequency before the disturbance. For frequency stability value, This refers to the droop coefficient of the generator set iG. It is the total number of generator sets. The rated active power of the generator set iG, This is the unit start / stop flag; the environmental indicators include the utilization rate of new energy sources and pollutant emissions as follows: the utilization rate of new energy sources is the actual total output P of the new energy unit within one cycle during frequency regulation. ENV To represent: In the formula, N RE This represents the number of new energy generating units, with iRE being the corresponding unit number. The real-time power of the new energy unit iRE during frequency regulation operation period t; pollutant emissions A ENV The expression is as follows: In the formula, a, b, and c are the coefficients of the function relating pollutant emissions to power. This refers to the power adjustment amount of the iTH thermal power unit during frequency regulation operation within the specified time period t.

6. The frequency control auxiliary decision-making method based on system frequency security level according to claim 5, characterized in that, The 、 、 、 and as follows: In the formula, N TH N RE and N ST These represent the number of thermal power units, new energy units, and energy storage power stations, respectively. iTH, iRE, and iST are the corresponding unit or power station designations. The unit power generation operation and maintenance cost of thermal power units. 、 This represents the real-time power of the thermal power unit iTH during frequency regulation operation period t+1 and frequency regulation operation period t. The additional cost per megawatt of thermal power unit incurred due to hill climbing; For the unit power operation and maintenance cost of new energy generating units, The real-time power of the new energy unit iRE during frequency regulation operation segment t; It is the unit power operation and maintenance cost of the energy storage power station. 、 α represents the charging and discharging power of the iST energy storage power station during frequency regulation operation period t, respectively; α is the wear coefficient per unit frequency regulation power, and λ is the lifespan depreciation cost per unit frequency regulation throughput.

7. The frequency control auxiliary decision-making method based on system frequency security level according to claim 4, characterized in that, The system security levels corresponding to the ranges from highest to lowest comprehensive security score are set at 5 levels as follows: a score in the range (0.7, 1] corresponds to system security level I; a score in the range (0.3, 0.7] corresponds to system security level II; a score in the range (0, 0.3] corresponds to system security level III; a score of 0 corresponds to system security level IV; and a score of -1 corresponds to system security level V.

8. The frequency control auxiliary decision-making method based on system frequency security level according to claim 4, characterized in that, The process of evaluating the system frequency security score based on the system frequency security comprehensive scoring model and determining the current system frequency security level according to the mapping relationship table includes: collecting real-time power grid frequency data using power grid monitoring devices such as PMUs; and measuring the maximum rate of change of system frequency in the initial stage if a disturbance occurs during the period. And then according to The magnitude of the disturbance is calculated; where, The change in frequency Indicates time; ΔP L H represents the magnitude of the disturbance. sys Let be the system inertial time constant; the frequency response analytical model of the disturbance input is used to obtain the maximum frequency deviation, maximum frequency change rate, and quasi-steady-state frequency deviation; based on the three indicators of maximum frequency deviation margin, maximum frequency change rate margin, and quasi-steady-state frequency deviation margin, a comprehensive safety score is obtained based on the system frequency safety comprehensive scoring model; and the corresponding frequency safety level is obtained based on the mapping relationship table between the comprehensive safety score and the safety level.

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