A method and device for online analysis of power grid frequency security

Abstract

The present application relates to the field of power systems, and specifically to a method and device for online analysis of power grid frequency security. The method for online analysis of power grid frequency security provided by the present application includes obtaining system inertia margin; obtaining a calculation method for the frequency change rate based on the system inertia margin; obtaining frequency safety influencing factors based on the calculation method of the frequency change speed; evaluating the system inertia margin and obtaining an inertia margin evaluation result; judging whether there is a safe operation domain of the power grid frequency based on the frequency change rate and the frequency safety influencing factors; analyzing the power grid frequency security under the current operation mode based on the inertia margin evaluation result and the existence of the safe operation domain. This analysis method can effectively establish an online evaluation index for the power grid frequency security level, propose an online frequency security level evaluation method applicable to interconnected power grids with a high proportion of new energy, simplify the security evaluation work, and provide a decision-making basis for the safe operation of the power grid.

Description

Technical Field

[0001] The present application relates to the field of power systems, and specifically to a method and device for online analysis of power grid frequency security. Background Art

[0002] As the proportion of installed renewable energy capacity continues to increase, the system's inertia is rapidly decreasing. Strengthening grid interconnection and supply chains has become a crucial technical measure to address the intermittent and random nature of renewable energy generation and ensure power supply. However, DC transmission fragments large power grids, making it difficult to share rotational inertia. Furthermore, the complex and volatile operation of renewable energy power systems makes online assessment and control of grid inertia difficult.

[0003] Currently, online assessments of system inertia are primarily based on operational experience and system simulations, lacking theoretical support. Indicators such as frequency regulation reserve and asynchronous generation penetration only provide indirect indicators of the system's online frequency security, but cannot directly quantitatively assess it. These indicators are only suitable as a reference and are insufficient for guiding online frequency security assessments. Summary of the Invention

[0004] In view of this, the present application provides a method and device for online analysis of power grid frequency security, which solves or improves the technical problems in the prior art of insufficient accuracy of online analysis and evaluation of power grid system frequency and difficulty in ensuring power grid frequency security.

[0005] According to one aspect of the present application, the present application provides an online analysis method for power grid frequency security, which includes: obtaining system inertia margin and obtaining a calculation method for the frequency change rate based on the system inertia margin; obtaining a frequency safety influencing factor based on the calculation method of the frequency change rate; evaluating the system inertia margin and obtaining an inertia margin evaluation result; and judging whether there is a safe operation domain of the power grid frequency based on the frequency change rate and the frequency safety influencing factor; analyzing the power grid frequency safety under the current operating mode based on the inertia margin evaluation result and the existence of the safe operation domain.

[0006] In one possible implementation, obtaining the system equivalent inertia margin includes: obtaining a system equivalent inertia coefficient and an inertia margin reference; normalizing the system equivalent inertia coefficient according to the inertia margin reference, and using the normalized system equivalent inertia coefficient as the system inertia margin.

[0007] In one possible implementation, obtaining the system equivalent inertia coefficient includes: obtaining the rotational kinetic energy and start / stop status of the generator set, the rotational kinetic energy and start / stop status of the motor, the equivalent rotational kinetic energy and start / stop status of the power electronic power supply, and the load of the system; substituting the start / stop status of the rotational kinetic energy of the generator set, the rotational kinetic energy and start / stop status of the motor, the equivalent rotational kinetic energy and start / stop status of the power electronic power supply, and the load of the system into formula (1) to calculate the system equivalent inertia coefficient;

[0008] (Formula 1)

[0009] Where ρ represents the system equivalent inertia coefficient, represents the rotational kinetic energy of generator set i, represents the rotational kinetic energy of motor j, represents the equivalent rotational kinetic energy of the power electronic power supply k, 、 、 Respectively represent the start and stop status of the generator, motor and power electronic power supply, and their values ​​are shown in formula (2). Indicates the load of the system.

[0010] (Calculation formula 2).

[0011] In a possible implementation, obtaining the load of the system includes: obtaining a synchronous power supply output, a power electronic power supply output, and an external power supply; and calculating the load of the system based on the synchronous power supply output, the power electronic power supply output, and the external power supply.

[0012] In one possible implementation, the method for calculating the frequency change rate based on the system inertia margin includes obtaining power impact, the start / stop status of the power supply, the load of the system, and the load of the motor; and calculating the frequency change rate based on the power impact, the start / stop status of the power supply, the load of the system, and the load of the motor.

[0013] In one possible implementation, evaluating the system inertia margin and obtaining an inertia margin evaluation result includes: obtaining a minimum inertia margin under a typical operating mode of a current regional power grid; comparing the system inertia margin and the minimum inertia margin; when the system inertia margin is greater than or equal to the minimum inertia margin, the inertia margin evaluation result is that the frequency safety margin is sufficient; when the system inertia margin is less than the minimum inertia margin, the inertia margin evaluation result is that the frequency safety margin is insufficient, and adjusting the current operating mode of the power grid.

[0014] In one possible implementation, judging whether there is a safe operation domain of the grid frequency based on the frequency change rate and the frequency safety influencing factors includes: obtaining the maximum power impact under the current operation mode of the grid; obtaining the load inertia characteristics under the current operation mode of the grid; obtaining the equivalent rotational kinetic energy demand of the power supply based on the maximum power impact and the load inertia characteristics; obtaining the start-stop combination of the unit; and judging whether there is a safe operation domain of the grid frequency based on the start-stop combination of the unit and the equivalent rotational kinetic energy demand of the power supply; wherein, when the start-stop combination of the unit meets the equivalent rotational kinetic energy demand of the power supply, there is a safe operation domain of the grid frequency, and when the start-stop combination of the unit does not meet the equivalent rotational kinetic energy demand of the power supply, there is no safe operation domain of the grid frequency.

[0015] In one possible implementation, obtaining the maximum power impact under the current operating mode of the power grid includes: obtaining the voltage impact and power impact under the current operating mode of the power grid; and obtaining the maximum impact power under the current operating mode of the power grid based on the voltage impact and power impact under the current operating mode of the power grid.

[0016] In one possible implementation, obtaining the load inertia characteristics under the current operating mode of the power grid includes: obtaining the motor inertia and load size under the current operating mode of the power grid; and obtaining the load inertia characteristics under the current operating mode of the power grid based on the motor inertia and load size under the current operating mode of the power grid.

[0017] According to another aspect of the present application, the present application also provides an online analysis device for power grid frequency security, which includes: a system inertia margin acquisition module for acquiring system inertia margin; a frequency change rate calculation module for acquiring a calculation method for the frequency change rate based on the system inertia margin; a frequency safety influencing factor acquisition module for acquiring a frequency safety influencing factor based on the calculation method for the frequency change rate; an inertia margin evaluation result acquisition module for evaluating the system inertia margin and acquiring an inertia margin evaluation result; and a safe operation domain judgment module for judging whether there is a safe operation domain of the power grid frequency based on the frequency change rate and the frequency safety influencing factor; a power grid frequency security analysis module for analyzing the power grid frequency security under the current operation mode based on the inertia margin evaluation result and the existence of the safe operation domain.

[0018] The present application provides a method and device for online analysis of power grid frequency security. Among them, the above-mentioned online analysis method for power grid frequency security specifically includes the following steps: obtaining system inertia margin; obtaining the calculation method of the frequency change rate based on the system inertia margin; obtaining the frequency safety influencing factor based on the calculation method of the frequency change rate; evaluating the system inertia margin and obtaining the inertia margin evaluation result; and judging whether there is a safe operation domain of the power grid frequency based on the frequency change rate and the frequency safety influencing factor; analyzing the power grid frequency safety under the current operation mode based on the inertia margin evaluation result and the existence of the safe operation domain. The online analysis method for power grid frequency security provided by the present application can effectively establish an online evaluation index for the power grid frequency security level, propose an online evaluation method for the frequency security level that can be applied to interconnected power grids with a high proportion of new energy, simplify the safety evaluation work, reduce the required simulation calculation workload, propose an online evaluation process for power grid inertia margin and a safe operation domain analysis method, and provide a decision-making basis for the safe operation of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The figure shows a flow chart of a method for online analysis of power grid frequency security provided in one embodiment of the present application.

[0020] Figure 2 Shown is a flow chart of a method for online analysis of power grid frequency security provided in another embodiment of the present application.

[0021] Figure 3 The figure shows a flow chart of an online evaluation method for system inertia margin in an online analysis method for power grid frequency security provided by another embodiment of the present application.

[0022] Figure 4 The figure shows a flow chart of a method for determining a safe operating domain of a power grid frequency in an online power grid frequency security analysis method provided by another embodiment of the present application.

[0023] Figure 5 The figure shows the relationship between the power impact ratio, inertia margin and RoCoF in a grid frequency security online analysis method provided by another embodiment of the present application.

[0024] Figure 6 The figure shows a flow chart of an online evaluation method of a power grid safety operation domain in an online analysis method of power grid frequency security provided by another embodiment of the present application.

[0025] Figure 7 Shown is a schematic diagram of a power grid frequency safety operation domain in a power grid frequency safety online analysis method provided in another embodiment of the present application.

[0026] Figure 8Shown is a structural diagram of an improved WSCC9 node system in a simulation verification process provided by another embodiment of the present application.

[0027] Figure 9 The figure shows a RoCoF change curve of the improved WSCC9 node system after power impact in the simulation verification process provided by another embodiment of the present application.

[0028] Figure 10 The figure shows a curve diagram of the RoCoF change of the system after a tie line fault during a simulation verification process provided by another embodiment of the present application.

[0029] Figure 11 Shown is a curve diagram of the influence of motor load inertia on RoCoF during a simulation verification process provided by another embodiment of the present application.

[0030] Figure 12 Shown is a frequency change characteristic curve diagram of different operating modes in the simulation verification process provided by another embodiment of the present application.

[0031] Figure 13 Shown is a structural block diagram of an electronic device provided in one embodiment of the present application. DETAILED DESCRIPTION

[0032] In the description of the application, the meaning of "multiple" is at least two, for example two, three, etc., unless otherwise clearly and specifically limited. In the embodiments of the present application, all directional indications (such as up, down, left, right, front, back, top, bottom ...) are only used to explain the relative position relationship, motion situation, etc. between each component under a certain specific posture (as shown in the drawings). If this specific posture changes, this directional indication also changes accordingly. In addition, the terms "comprise" and "have" and any deformation thereof are intended to cover non-exclusive inclusion. For example, the process, method, system, product or equipment comprising a series of steps or units is not limited to the steps or units listed, but optionally also includes the steps or units not listed, or optionally also includes other steps or units inherent to these processes, methods, products or equipment.

[0033] In addition, references to "embodiments" herein mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of such phrases in various places in the specification does not necessarily refer to the same embodiment, nor does it necessarily refer to independent or alternative embodiments that are mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0034] The applicant further analyzed the reasons why online analysis and evaluation of power grid system frequency in the prior art is inaccurate and grid frequency security is difficult to ensure, and found that:

[0035] As the proportion of installed renewable energy capacity continues to increase, the system's inertia is rapidly decreasing. Strengthening grid interconnection and supply chains has become a crucial technical measure to address the intermittent and random nature of renewable energy generation and ensure power supply. However, DC transmission fragments large power grids, making it difficult to share rotational inertia. Furthermore, the complex and volatile operation of renewable energy power systems makes online assessment and control of grid inertia difficult.

[0036] Research on frequency security issues in power grids with a high proportion of renewable energy mainly focuses on system response characteristics, system inertia assessment, stability analysis and control. Among them, system inertia is an important indicator that characterizes the power grid's ability to resist frequency changes. It is also the basis for studying system response characteristics and formulating stability control strategies. The three frequency security indicators of the power grid, rate of change of frequency (RoCoF), transient frequency deviation and steady-state frequency deviation, are all related to the system inertia level. Existing technologies have defined the generalized inertia of the power system from the perspectives of synchronous and asynchronous rotating inertia, electromagnetic coupling equivalent inertia and virtual inertia, analyzed the supporting role of the demand side on the system inertia, and proposed an online rapid estimation method for the rotational inertia characteristics of the source and load sides based on the perturbation method. This provides a decision-making basis for the formulation of the system's power generation strategy and the approval of transmission limits, and also provides a basis for the assessment of the system's frequency security level.

[0037] Currently, online assessments of system inertia are primarily based on operational experience and system simulations, lacking theoretical support. Indicators such as frequency regulation reserve and asynchronous generation penetration only provide indirect indicators of the system's online frequency security, but cannot directly quantitatively assess it. These indicators are only suitable as a reference and are insufficient for guiding online frequency security assessments.

[0038] To address the above issues, we comprehensively consider the inertia composition of the power grid, establish a reference benchmark for the power grid inertia level, and propose the power grid inertia margin index and RoCoF index by taking into account the power source inertia, load inertia and exchange power. We analyze the factors affecting the system frequency security, and propose an online frequency security level assessment method and a frequency safety operation domain analysis method considering RoCoF constraints. These methods provide a decision-making basis for the online frequency security assessment and safety management of the power grid, which is of great significance to the safe operation of the power grid.

[0039] Therefore, the present application provides a method and device for online analysis of power grid frequency security. Among them, the above-mentioned online analysis method for power grid frequency security specifically includes the following steps: obtaining system inertia margin; obtaining the calculation method of the frequency change rate based on the system inertia margin; obtaining the frequency safety influencing factors based on the calculation method of the frequency change rate; evaluating the system inertia margin and obtaining the inertia margin evaluation result; and judging whether there is a safe operation domain of the power grid frequency based on the frequency change rate and the frequency safety influencing factors; analyzing the power grid frequency safety under the current operation mode based on the inertia margin evaluation result and the existence of the safe operation domain. The online analysis method for power grid frequency security provided by the present application can effectively establish an online evaluation index for the power grid frequency security level, propose an online evaluation method for the frequency security level that can be applied to interconnected power grids with a high proportion of new energy, simplify the safety evaluation work, reduce the required simulation calculation workload, propose an online evaluation process for power grid inertia margin and a safe operation domain analysis method, and provide a decision-making basis for the safe operation of the power grid.

[0040] The following will be combined with the accompanying drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0041] Figure 1 FIG. 1 is a flow chart of a method for online analysis of power grid frequency security provided by an embodiment of the present application. Figure 1 As shown, the grid frequency security online analysis method may specifically include the following steps:

[0042] Step 100: Obtain system inertia margin.

[0043] System inertia represents the resistance to changes in the system's state (frequency), encompassing all factors that inhibit frequency changes before the speed control system takes effect. System inertia margin is used to indicate the steady-state performance of a power system. System inertia margin is a concept defined in this application. Because the power system's frequency security level is closely related to the margin of the system's (equivalent) rotational inertia, the system's (equivalent) rotational inertia can be expressed as the sum of the total kinetic energy of all rotating components in the grid and the equivalent kinetic energy of the power electronic generator.

[0044] Step 200: Obtain a calculation method for the frequency change rate according to the system inertia margin.

[0045] The system's rate of change of frequency (RoCoF) is a technical indicator directly related to the system's inertia level. By converting the aforementioned system inertia margin, combined with factors such as system power impact and initial operating frequency, we can derive a method for calculating the rate of change of frequency, enabling more effective determination of the system's inertia level.

[0046] Step 300: Obtain frequency safety impact factors according to the frequency change rate calculation method.

[0047] Factors affecting frequency safety include, but are not limited to, fault impacts on the system, motor inertia, and external exchange power. These factors all affect system frequency changes. Based on these factors, the safety of the grid frequency can be more effectively evaluated and analyzed to ensure the reliability of the grid operation process.

[0048] Step 400: Evaluate the system inertia margin and obtain the inertia margin evaluation result.

[0049] The inertia margin assessment results are frequency security analysis results obtained through an online evaluation of the system's inertia margin, indicating whether the frequency security margin is sufficient or insufficient under the current operating mode. This assessment method is suitable for new energy power systems with frequently changing load characteristics, generation methods, and external exchange power, significantly reducing the workload of online assessments.

[0050] Step 500: Determine whether there is a safe operation domain for the power grid frequency based on the frequency change rate and frequency safety influencing factors.

[0051] The safe operating domain of the power grid frequency is the area where the entire power grid system can operate safely and stably. The relative relationship between the system operating point and the boundary can provide safety margin and optimal control information, making the online real-time safety monitoring, defense and control of the power system more scientific and effective.

[0052] Step 600: Analyze the grid frequency safety under the current operation mode based on the inertia margin assessment result and the existence of the safe operation domain.

[0053] This application takes into account the system startup mode, output plan, load inertia and external power supply level, defines the system inertia margin index of the interconnected power grid, obtains the system RoCoF calculation method, proposes an analysis method for the safe operation domain and a calculation method for the external power supply capacity, and provides technical indicators and evaluation basis for online frequency security analysis. This method is concise and clear, with accurate calculations, and can provide quantitative indicators for power grid frequency security analysis, significantly improving the efficiency of power grid frequency security analysis.

[0054] In one possible implementation, Figure 2As shown, step 100 (obtaining system inertia margin) may further include the following steps:

[0055] Step 110: Obtain the system equivalent inertia coefficient and inertia margin benchmark.

[0056] The system equivalent inertia coefficient is determined by combining multiple factors, including the synchronous power supply, motor load, and the inertia support capability of the power electronics. The inertia margin benchmark is the benchmark data used to normalize the system equivalent inertia coefficient.

[0057] Step 120: Normalize the system equivalent inertia coefficient according to the inertia margin standard, and use the normalized system equivalent inertia coefficient as the system inertia margin.

[0058] The system inertia margin is obtained by integrating the system equivalent inertia coefficient of multiple factors. This system inertia margin is used as an indicator for online evaluation of the power grid frequency security level. This can simplify the evaluation process, reduce the workload of simulation calculations, and provide a decision-making basis for the safe operation of the power grid.

[0059] Specifically, in one embodiment of the present application, step 110 (obtaining the system equivalent inertia coefficient and the inertia margin benchmark) may include the following steps:

[0060] Step 111: Obtain the rotational kinetic energy and start / stop status of the generator set, the rotational kinetic energy and start / stop status of the motor, the equivalent rotational kinetic energy and start / stop status of the power electronic power supply, and the load of the system.

[0061] Step 112: Substitute the start / stop state of the rotational kinetic energy of the generator set, the rotational kinetic energy and start / stop state of the motor, the equivalent rotational kinetic energy and start / stop state of the power electronic power supply, and the load of the system into formula (1) to calculate the system equivalent inertia coefficient.

[0062] (Formula 1)

[0063] Where ρ represents the system equivalent inertia coefficient, represents the rotational kinetic energy of generator set i, represents the rotational kinetic energy of motor j, represents the equivalent rotational kinetic energy of the power electronic power supply k, 、 、 Respectively represent the start and stop status of the generator, motor and power electronic power supply, and their values ​​are shown in formula (2). Indicates the load of the system.

[0064] (Calculation formula 2).

[0065] Furthermore, "obtaining the system load" in step 111 (obtaining the rotational kinetic energy and start / stop status of the generator set, the rotational kinetic energy and start / stop status of the motor, the equivalent rotational kinetic energy and start / stop status of the power electronic power supply, and the system load) may specifically include the following steps:

[0066] Step 1110: Obtain the synchronous power supply output, the power electronic power supply output, and the external power received.

[0067] Step 1111: Calculate the system load based on the synchronous power supply output, the power electronic power supply output, and the external power received.

[0068] When network losses are ignored, the system load can be expressed as the sum of the system's internal synchronous power supply output, power electronic power supply output, and external power supply power, as shown in Formula (3).

[0069] (Formula 3)

[0070] in, Indicates the load of the system. Indicates the rated capacity of synchronous power supply i, Indicates the rated capacity of the power electronic power supply k, Indicates the output coefficient of the synchronous power supply, Indicates the external power received by the system.

[0071] In addition, the total amount of rotational kinetic energy of the motor in formula (1) can be obtained by the following formula (4):

[0072] (Formula 4)

[0073] in, is the motor load ratio, is the uniform inertia time constant of the motor.

[0074] Substituting formula (3) and formula (4) into formula (1), we can obtain formula (5) for calculating the load inertia and the equivalent inertia coefficient of the system affected by external power.

[0075] (Formula 5)

[0076] According to the calculation formula (5) and the above-mentioned inertia margin standard, the system equivalent inertia coefficient is normalized to obtain the calculation formula (6) of the system equivalent inertia margin as follows:

[0077] (Calculation formula 6)

[0078] in, is the inertia margin benchmark, It is the system inertia margin.

[0079] Inertia margin standard The calculation method of is shown in formula (VII),

[0080] (Formula 7)

[0081] It is not difficult to understand that when When the system inertia margin is equivalent to At this time, the system's inertia margin is equivalent to operating state B, that is, the system's external exchange power is zero, all synchronous power supplies are operating at rated power, all power electronic power supplies are shut down, and the load does not contain rotating elements. When the system inertia margin is less than that of the operating state B, When , the system inertia margin is greater than that of operating state B.

[0082] The following takes the inertia margin benchmark of a typical provincial power grid as an example. The specific inertia margin benchmark is shown in Table 1.

[0083] Table 1 Inertia margin benchmarks for typical provincial power grids

[0084]

[0085] In Table 1, grid a is a typical AC receiving grid, grid b is a typical AC / DC receiving grid, and grid c is a hydropower-rich sending grid.

[0086] Without considering the inertia effects of power electronic power supplies and motor loads, the hydropower plants in the grid shown in Table 1 are operated in phase shift mode, and the thermal power plants are operated at minimum technical output (30% of rated power). The (maximum) system inertia margins of a typical provincial grid are obtained, as shown in Table 2.

[0087] Table 2 Inertia margin of typical provincial power grids

[0088]

[0089] In another possible implementation, Figure 2 As shown, step 200 (obtaining a calculation method for the frequency change rate based on the system inertia margin) may further include the following steps:

[0090] Step 210: Obtain power impact, power on / off status, system load, and motor load.

[0091] Step 220: Calculate the frequency change rate according to the power impact, the start and stop status of the power supply, the load of the system, and the load of the motor.

[0092] The frequency change rate of the system is a technical indicator directly related to the system inertia level. The power impact on the system is , then the RoCoF of the system after disturbance is as shown in formula (8),

[0093] (Formula 8)

[0094] Where f0 represents the initial operating frequency of the system. Substituting formula (3) and calculation formula (5) into formula (8), the RoCoF of the system can be obtained as shown in formula (9).

[0095] (Formula 9)

[0096] Further deduction can be obtained as formula (10) as follows:

[0097] Formula (10)

[0098] Formula (9) shows that the system's frequency change rate is affected by the magnitude of the power surge, the power supply's on / off status, the system load level, and the motor load. Reducing the power surge of a fault, turning on a power supply with (equivalent) rotational inertia, and increasing the load's inertia can all reduce the system's RoCoF after a disturbance.

[0099] It is worth mentioning that for the above factors that can reduce the frequency change rate after the system is disturbed, this application can provide the following analysis:

[0100] First, for the power impact of the fault, it can be seen from formula (9) that in order to make the RoCoF of the system after the disturbance lower than the maximum safe rate of frequency change , the maximum power impact that the system can withstand should meet the following restrictions:

[0101] (Formula 11)

[0102] From formula (11), we can see that the maximum power impact that the system can withstand is related to the start and stop status of the units in the grid, the motor load characteristics, and the maximum RoCoF allowed by the system.

[0103] Ignoring the impact of frequency changes at the initial stage of the disturbance on frequency-sensitive loads, the power shock to the system can be decomposed into direct power shock and voltage change power shock ,Right now:

[0104] (Formula 12)

[0105] Direct power shock It is the power shortage caused directly by the fault, such as line disconnection, power failure, DC blocking, etc. When the voltage changes, the voltage-sensitive load can be expressed as:

[0106] (Formula 13)

[0107] In formula (13), Indicates the load value of normal operation under rated voltage; 、 、 Indicates the proportion of constant impedance load, constant current load and constant power load respectively, the sum of the three is 1; Indicates the normal operating voltage when there is no disturbance; Indicates the voltage disturbance.

[0108] From formula (13), we can know that the power impact caused by instantaneous voltage change is:

[0109] (Formula 14)

[0110] Therefore, when considering the system's fault impact tolerance, both the direct power shortage caused by the fault and the power disturbance caused by voltage changes should be considered.

[0111] Secondly, the impact of external switching power on the system can be analyzed as follows:

[0112] The above calculation formula (5) is decomposed as follows:

[0113] (Calculation formula 15)

[0114] in, 、 They are the power supply side inertia and the load side inertia. When there is no correlation with the maximum power shock that the system may withstand, as shown in calculation formula (15), for the operation mode determined by the load size and load characteristics, the load inertia is a given value, so that the total inertia of the system (At this time Compared with the formula 1 different meanings) to meet frequency safety requirements, power supply rotational inertia This is the primary controllable factor. Therefore, while meeting the minimum margin requirement, shutting down units within the zone that do not contribute rotational inertia and maintaining the minimum technical output of the remaining synchronous units can maximize external power consumption. If the external power exchange exceeds this value, the system's frequency security is at risk.

[0115] When the system exchanges power externally The maximum power shock that the system may withstand When they are equal (such as DC blocking), the maximum external power receiving capacity of the system can be obtained from formula (10):

[0116] (Formula 16).

[0117] Again, for the motor inertia, it can be seen from the calculation formula (15) that the load inertia in the same system is and power inertia The ratio is:

[0118] (Formula 17)

[0119] my country often uses the typical "constant impedance + motor" load model in power grid simulations. The motor load ratio in provincial power grids ranges from 30% to 70%, and the load model's uniform inertia coefficient is 2s. Based on Formula (17), the ratio of load inertia to power supply inertia for a typical provincial power grid, ignoring the equivalent inertia of power electronic power supplies, is calculated and shown in Table 3.

[0120] Table 3 Load-source inertia ratio of typical provincial power grids

[0121]

[0122] As shown in Table 3, the rotational inertia of motor loads accounts for approximately 15%-40% of the power supply inertia. Therefore, it is essential to consider the impact of grid load rotational inertia in power grid frequency security analysis. Ignoring load inertia can result in significant deviations. In practice, statistical and perturbation methods can be used to assess grid load inertia.

[0123] Finally, for the replacement relationship between inertia and output in the system, the equivalent inertia coefficient of the regional power grid is shown in formula (15). The system equivalent inertia includes the power supply part. and load part On two aspects, and The total inertia of the system does not change when performing equal replacement size.

[0124] Similarly, as shown in formula (3), when the on / off status of power sources within the regional grid is fixed and their (equivalent) rotational inertia does not change with their output level, equal substitution of the total power generation output of each power source and the external power supply level does not change the system's inertia. Equal substitution of output levels also exists between power sources within the regional grid; simply changing the power generation schedule does not alter the system's inertia.

[0125] Specifically, in another embodiment of the present application, Figure 2 As shown, step 400 (evaluating system inertia margin and obtaining inertia margin evaluation results) may specifically include the following steps:

[0126] Step 410: Obtain the minimum inertia margin under the typical operation mode of the current regional power grid.

[0127] Energy and power systems operate in many different modes and change rapidly. Real-time evaluation of the system's inertia redundancy level through online simulation is labor-intensive, time-sensitive, and difficult.

[0128] From the above analysis, we can see that the rotational inertia and power output are interchangeable, and the inertia margin is The same inertia margin level is the same for different operating modes. When there is no major change in the grid structure, the minimum safe inertia margin level is obtained by checking the typical operating mode of a regional grid. , which is generally applicable to other operating modes.

[0129] Step 420 : Compare the system inertia margin and the minimum inertia margin. When the system inertia margin is greater than or equal to the minimum inertia margin, the inertia margin assessment result indicates that the frequency safety margin is sufficient.

[0130] Step 430: When the system inertia margin is less than the minimum inertia margin, the inertia margin assessment result is that the frequency safety margin is insufficient, and the current operation mode of the power grid is adjusted.

[0131] Figure 3 FIG. 1 is a flow chart of online evaluation of system inertia margin in an online analysis method for power grid frequency security provided by another embodiment of the present application. Figure 3 As shown in the figure, system inertia margin assessment can be conducted using the "offline verification + online comparison" approach. This assessment method is suitable for new energy power systems with frequently changing load characteristics, generation methods, and external exchange power, significantly reducing the workload of online assessments. Furthermore, if the assessment result indicates that the system's frequency safety margin is insufficient, the current operating mode can be adjusted promptly, thereby ensuring the normal operation of the power system and reducing the probability of safety accidents.

[0132] In one possible implementation, Figure 4 FIG. 1 is a flow chart of a method for determining a safe operating domain of a power grid frequency in a power grid frequency safety online analysis method provided by another embodiment of the present application. Figure 4 As shown, step 500 (determining whether there is a safe operation domain of the power grid frequency based on the frequency change rate and the frequency safety influencing factors) may include the following steps:

[0133] Step 510: Obtain the maximum power impact under the current operation mode of the power grid.

[0134] Step 520: Obtain the load inertia characteristics under the current operation mode of the power grid.

[0135] Step 530: Obtain the power supply equivalent rotational kinetic energy requirement according to the maximum power impact and load inertia characteristics.

[0136] Step 540: Obtain the start / stop combination of the unit.

[0137] Step 550: Determine whether there is a safe operating range for the grid frequency based on the start / stop combination of the unit and the equivalent rotational kinetic energy demand of the power supply.

[0138] Among them, when the start-stop combination of the unit meets the equivalent rotational kinetic energy demand of the power supply, there is a safe operating domain of the grid frequency. When the start-stop combination of the unit does not meet the equivalent rotational kinetic energy demand of the power supply, there is no safe operating domain of the grid frequency.

[0139] To analyze the safe operation domain of the power grid system, the ratio of the power shock suffered by the regional power grid to the total load of the regional power grid is:

[0140] (Formula 18)

[0141] Substituting formula (18) into formula (8) yields:

[0142] (Formula 19)

[0143] It can be seen that for a certain regional power grid, the power impact ratio , Inertia margin The relationship between the frequency change rate τ and the frequency change rate τ is as shown in formula (19) and Figure 5 As shown, Figure 5 The figure shows the relationship between the power impact ratio, inertia margin and RoCoF in a grid frequency security online analysis method provided by another embodiment of the present application.

[0144] In real-world power grids, the maximum allowable RoCoF is typically set to a fixed value. The operating mode of a regional power grid constantly changes, and load levels, motor inertia, and the potential maximum power surge all fluctuate with these changes. Power supply on / off status, generation schedules, and external power supply levels all become controllable factors in ensuring a secure RoCoF.

[0145] In order to maintain a certain frequency safety margin in the system operation mode, the analysis process shown in step 500 may be combined to evaluate the feasible region of safe operation of the power grid online.

[0146] Specifically, in one embodiment of the present application, step 510 (obtaining the maximum power impact under the current operation mode of the power grid) may include the following steps:

[0147] Step 511: Obtain voltage shock and power shock under the current operation mode of the power grid.

[0148] Step 512: According to the voltage impact and power impact under the current operation mode of the power grid, the maximum impact power under the current operation mode of the power grid is obtained.

[0149] Meanwhile, step 520 (obtaining the load inertia characteristics under the current operation mode of the power grid) may include the following steps:

[0150] Step 521: Obtain the motor inertia and load size under the current operation mode of the power grid.

[0151] Step 522: Obtain the load inertia characteristics under the current operation mode of the power grid according to the motor inertia and load size under the current operation mode of the power grid.

[0152] By evaluating and monitoring factors such as voltage supply, power impact, motor inertia and load size in the real-time operation mode, the maximum power impact and load inertia characteristics under the operation mode can be obtained, taking into account the frequency change constraints of the power grid. , the equivalent rotational kinetic energy requirement of the power supply can be obtained.

[0153] Under this operating mode, if the start-stop combination of the unit cannot meet the minimum safe rotational kinetic energy requirement, there is no frequency safety operating domain, and the operating mode needs to be adjusted to cut off part of the load; if the start-stop combination of the unit can obtain rotational kinetic energy greater than the minimum safety requirement, there is a frequency safety operating domain. Figure 6 The figure shows a flow chart of an online evaluation method of a power grid safety operation domain in an online analysis method of power grid frequency security provided by another embodiment of the present application. Figure 7 The figure shows a schematic diagram of the grid frequency safety operation domain in a grid frequency safety online analysis method provided by another embodiment of the present application. The power supply start-stop state, unit power generation plan, and external power supply safety combination form the following: Figure 7 The grid frequency safe operating domain is shown.

[0154] The start / stop status of the grid's generators determines the equivalent rotational energy of the power supply. The sum of the grid's internal power generation and external power consumption is approximately equal to the system load. The grid's internal power generation is constrained by the maximum and minimum technical outputs of the active generators. The actual generator start / stop status, power generation plan, and external power consumption can be determined within the safe frequency operating range, taking into account other constraints such as economic efficiency.

[0155] In addition, the applicant has conducted simulation verification of the accuracy of relevant indicators of the above-mentioned online analysis method for power grid frequency security, which is sufficient to illustrate the accuracy of this online analysis method.

[0156] Figure 8 The diagram shows the structure of the improved WSCC9 node system in the simulation verification process provided by another embodiment of the present application. Based on the PSD-BPA software, the improved WSCC 9 node example is built for simulation verification. The source and load conditions of the example are shown in Table 4. Figure 8 The operating state shown is based on Option A. System S1 connects to the 9-node case via power electronics, providing no rotational inertia support. The photovoltaic power source does not contribute equivalent rotational inertia, and the unit's frequency regulation system is not considered. Option A's load model is a "constant impedance + motor" model, with a motor ratio of 60%.

[0157] Table 4 Improved WSCC 9-node system configuration

[0158]

[0159] Theoretical calculation: Equation (5) calculates the equivalent inertia coefficient ρ for the example in mode a to be 6.813s. Equation (7) calculates the inertia margin benchmark for the example to be 4.865s, and Equation (6) calculates the inertia margin index to be 1.4. Equation (9) calculates that when the system is subjected to a 10MW power shock, the frequency drop rate is 0.04696Hz / s.

[0160] Figure 9 The figure shows the RoCoF change curve of the improved WSCC9 node system after the power shock in the simulation verification process provided by another embodiment of the present application. In order to verify the evaluation effect of the frequency safety index, the simulation method a is obtained. The frequency change curve of the system after the 10MW power shock at 1s is as follows: Figure 9 shown.

[0161] Depend on Figure 9 The simulation curve shows that the system frequency dropped by 0.04653 Hz 1 second after the fault. Considering the frequency regulation effect of the load, the maximum frequency drop rate of the system should be slightly greater than 0.04653 Hz / s. Applying the above information using Formula (9), the theoretical system frequency drop rate is calculated to be 0.04696 Hz / s. The difference between the theoretical calculation result and the simulation result is less than 0.00043 Hz / s, and the calculation error of Formula (9) is less than 1.1%. The proposed frequency safety assessment index can accurately calculate the frequency drop rate.

[0162] Figure 10The figure shows the RoCoF change curve of the system after the tie line fault in the simulation verification process provided by another embodiment of the present application. The maximum RoCoF allowed by the above system is set to 0.500Hz / s, and the maximum external power is calculated to be 109.1MW according to formula (16). Keep G1 and G2 turned on, the external power is 109.1MW, and the simulation shows that when the tie line is disconnected at 1s, the frequency change of the system is as follows Figure 10 shown.

[0163] The frequency drops by about 0.487 Hz 1 s (i.e. 2 s) after the fault. Considering the regulating effect of the load, the frequency drop rate after the fault should be greater than 0.487 Hz / s. The simulation result differs from the set value of 0.500 Hz by less than 2.6%.

[0164] Table 5 shows the comparison between the calculated and simulated values ​​of the system's maximum external power supply capability under different RoCoF limits. The errors under the three RoCoF limits are between 2.2% and 4.0%, which shows that Equation (16) can more accurately calculate the external power supply capability under the maximum RoCoF limit after the system is disturbed.

[0165] Table 5 Comparison of calculated and simulated values ​​of the system's maximum external power supply

[0166]

[0167] The equivalent inertia coefficient of the power supply under mode a is calculated by formula (15): is 5.556s, load equivalent inertia coefficient The load inertia is 17.8% of the system equivalent inertia.

[0168] Figure 11 The figure shows the influence of motor load inertia on RoCoF during the simulation verification process provided by another embodiment of the present application. Under mode a, when the simulation system is subjected to the same power impact, the system RoCoF curves considering and ignoring the influence of motor inertia are as follows: Figure 10 As shown. Figure 11 It can be seen that when the influence of motor inertia is not considered, the system's RoCoF is significantly higher than when the motor load inertia is considered. Motor inertia is a significant component of the system's equivalent inertia. Ignoring the influence of motor inertia will lead to inaccurate assessment of grid frequency characteristics and an overly conservative assessment of the operating mode.

[0169] To verify the replacement characteristics of the above equivalent inertia and power output, we used basic mode a as a reference, kept the equivalent inertia margin ρ* at 1.4, and replaced the rotational kinetic energy and power output to form four operating modes: b, c, d, and e. The above five operating modes were simulated to analyze the frequency change characteristics of the system when subjected to the same power shock under different operating modes. The configuration of the five operating modes is shown in Table 6. Figure 12 The frequency change characteristic curves of different operating modes in the simulation verification process provided by another embodiment of the present application are shown. The frequency change curves are as follows Figure 12 shown.

[0170] Table 6 System parameters for different operating modes

[0171]

[0172] As shown in Table 6, compared with method a, method b increases the load rotational inertia and reduces the inertia of thermal power unit G1; method c increases the load rotational inertia and reduces the inertia of all thermal power units; method d readjusts the power generation of the two thermal power units; method e reduces the power generation of the thermal power units and increases the external power supply.

[0173] like Figure 12 As shown in the figure, when methods a, b, c, and d are subjected to the same power shock fault, the frequency drop curves are basically the same, all at 0.04653 Hz / s. The initial drop speed of method e is the same, and the drop depth is slightly different from the former, with the maximum difference not exceeding 3.2%.

[0174] Comparing methods a with methods b and c reveals a permutation relationship between the system's source and load inertias; maintaining the total inertia constant results in a constant system frequency characteristic. Comparing methods a with methods d and e reveals that, when the equivalent rotational inertia remains constant, there is a permutation relationship between the power sources within the grid and between the grid's internal power generation and external power reception. Simulation results show that operating methods with the same equivalent inertia coefficient exhibit essentially identical frequency change characteristics after a power surge, indirectly validating the accuracy of equations (5) and (9).

[0175] As can be seen, this application takes into account the system startup mode, output plan, load inertia, and external power supply level, defines the system inertia margin index of the interconnected power grid, derives the system RoCoF calculation method, proposes an analysis method for the safe operating domain and a method for calculating the external power supply capacity, and provides technical indicators and evaluation basis for online frequency security analysis. Through mutual verification between theory and simulation, the accuracy of the proposed indicators is verified. This method is concise and clear, with precise calculations, and can provide quantitative indicators for grid frequency security analysis, significantly improving the efficiency of grid frequency security analysis.

[0176] According to the second aspect of the present application, the present application also provides a power grid frequency safety online analysis device, which includes: a system inertia margin acquisition module, a frequency change rate calculation module, a frequency safety influencing factor acquisition module, an inertia margin evaluation result acquisition module, a safe operation domain judgment module, and a power grid frequency safety analysis module. Among them, the system inertia margin acquisition module is used to obtain the system inertia margin; the frequency change rate calculation module is used to obtain the calculation method of the frequency change rate based on the system inertia margin; the frequency safety influencing factor acquisition module is used to obtain the frequency safety influencing factor based on the calculation method of the frequency change rate; the inertia margin evaluation result acquisition module is used to evaluate the system inertia margin and obtain the inertia margin evaluation result; the safe operation domain judgment module is used to determine whether there is a safe operation domain of the power grid frequency based on the frequency change rate and the frequency safety influencing factor; the power grid frequency safety analysis module is used to analyze the power grid frequency safety under the current operation mode based on the inertia margin evaluation result and the existence of the safe operation domain.

[0177] The above-mentioned power grid frequency security online analysis device is used to apply the above-mentioned power grid frequency security online analysis method, and the beneficial effects produced are the same as those of the above-mentioned method, which will not be repeated here.

[0178] Below, reference Figure 13 To describe the electronic device according to the embodiment of the present application.

[0179] Figure 13 The figure shows a block diagram of an electronic device according to an embodiment of the present application.

[0180] like Figure 13 As shown, the electronic device 10 includes one or more processors 11 and a memory 12 .

[0181] The processor 11 may be a central processing unit (CPU) or other forms of processing units having data processing capabilities and / or instruction execution capabilities, and may control other components in the electronic device 10 to perform desired functions.

[0182] The memory 12 may include one or more computer program products, which may include various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. The volatile memory may include, for example, random access memory (RAM) and / or cache memory. The non-volatile memory may include, for example, read-only memory (ROM), a hard disk, flash memory, etc. One or more computer program instructions may be stored on the computer-readable storage medium, and the processor 11 may execute the program instructions to implement the above-described methods for online analysis of power grid frequency security according to various embodiments of the present application and / or other desired functions.

[0183] In one example, the electronic device 10 may further include an input device 13 and an output device 14 , and these components are interconnected via a bus system and / or other forms of connection mechanisms (not shown).

[0184] When the electronic device is a stand-alone device, the input device 13 may be a communication network connector, configured to receive collected input signals from the first device and the second device.

[0185] In addition, the input device 13 may also include, for example, a keyboard, a mouse, and the like.

[0186] The output device 14 can output various information to the outside, including determined distance information, direction information, etc. The output device 14 can include, for example, a display, a speaker, a printer, a communication network and a remote output device connected thereto, and the like.

[0187] Of course, to simplify, Figure 13 Only some of the components related to the present application in the electronic device 10 are shown, and components such as a bus, an input / output interface, etc. are omitted. In addition, the electronic device 10 may further include any other appropriate components according to specific application scenarios.

[0188] As a third aspect of the present application, the present application provides a computer-readable storage medium, wherein the storage medium stores a computer program, and the computer program is configured to perform the following steps:

[0189] Obtain the system inertia margin; based on the system inertia margin, obtain the calculation method of the frequency change rate; based on the calculation method of the frequency change rate, obtain the frequency safety influencing factors; evaluate the system inertia margin and obtain the inertia margin evaluation results; and based on the frequency change rate and the frequency safety influencing factors, determine whether there is a safe operating domain for the power grid frequency; based on the inertia margin evaluation results and the existence of the safe operating domain, analyze the power grid frequency safety under the current operating mode.

[0190] In addition to the above-mentioned methods and devices, an embodiment of the present application may also be a computer program product, which includes computer program information. When the computer program information is executed by a processor, the processor executes the steps of the grid frequency security online analysis method according to various embodiments of the present application described in this specification.

[0191] The computer program product may be written in any combination of one or more programming languages ​​to implement the program code for performing the operations of the embodiments of the present application, including object-oriented programming languages ​​such as Java, C++, and conventional procedural programming languages ​​such as "C" or similar programming languages. The program code may be executed entirely on the user's computing device, partially on the user's computing device, as a standalone software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server.

[0192] In addition, an embodiment of the present application may also be a computer-readable storage medium on which computer program information is stored. When the computer program information is executed by a processor, the processor executes the steps of the grid frequency security online analysis method according to various embodiments of the present application in this specification.

[0193] Computer-readable storage media can be any combination of one or more readable media. The readable medium can be a readable signal medium or a readable storage medium. The readable storage medium can include, for example, but is not limited to, electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, or components, or any combination thereof. More specific examples (a non-exhaustive list) of readable storage media include: an electrical connection having one or more wires, a portable disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof.

[0194] The basic principles of the present application have been described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, and effects mentioned in this application are merely illustrative and not restrictive, and it should not be assumed that these advantages, strengths, and effects are required of each embodiment of this application. In addition, the specific details disclosed above are merely illustrative and facilitating understanding, and are not restrictive. The above details do not limit this application to necessarily being implemented using the above specific details.

[0195] The block diagrams of the devices, devices, equipment, and systems involved in this application are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As will be appreciated by those skilled in the art, these devices, devices, equipment, and systems can be connected, arranged, or configured in any manner. Words such as "include," "comprise," "have," and the like are open-ended words, meaning "including but not limited to," and can be used interchangeably therewith. The words "or" and "and" used herein refer to the words "and / or" and can be used interchangeably therewith, unless the context clearly indicates otherwise. The word "such as" used herein refers to the phrase "such as but not limited to," and can be used interchangeably therewith.

[0196] It should also be noted that in the apparatus, device, and method of the present application, each component or each step can be decomposed and / or recombined, and such decomposition and / or recombination should be regarded as equivalent solutions of the present application.

Claims

1. A method for online analysis of power grid frequency security, characterized in that: include: Get the system inertia margin; The obtaining of the system equivalent inertia margin includes: Obtain the system equivalent inertia coefficient and inertia margin benchmark; performing per-unit normalization processing on the system equivalent inertia coefficient according to the inertia margin standard, and using the processed system equivalent inertia coefficient as the system inertia margin; The obtaining of the system equivalent inertia coefficient includes: Obtain the rotational kinetic energy and start / stop status of the generator set, the rotational kinetic energy and start / stop status of the motor, the equivalent rotational kinetic energy and start / stop status of the power electronic power supply, and the system load; Substitute the start / stop state of the rotational kinetic energy of the generator set, the rotational kinetic energy and start / stop state of the motor, the equivalent rotational kinetic energy and start / stop state of the power electronic power supply, and the load of the system into formula (1) to calculate the equivalent inertia coefficient of the system; (Formula 1) Where ρ represents the system equivalent inertia coefficient, represents the rotational kinetic energy of generator set i, represents the rotational kinetic energy of motor j, represents the equivalent rotational kinetic energy of the power electronic power supply k, 、 、 Respectively represent the start and stop status of the generator, motor and power electronic power supply, and their values ​​are shown in formula (2). Indicates the load of the system. (Calculation formula 2); According to the system inertia margin, a calculation method for obtaining the frequency change rate is obtained; Obtaining frequency safety impact factors according to the frequency change rate calculation method; evaluating the system inertia margin and obtaining an inertia margin evaluation result; and Determining whether there is a safe operation domain for the power grid frequency based on the frequency change rate and the frequency safety influencing factors; The frequency safety of the power grid under the current operating mode is analyzed based on the inertia margin evaluation result and the existence of the safe operating domain.

2. The method for online analysis of power grid frequency security according to claim 1, characterized in that: The obtaining of the load of the system includes: Obtain synchronous power supply output, power electronic power supply output and external power; The load of the system is calculated according to the synchronous power supply output, the power electronic power supply output and the external power received.

3. The method for online analysis of power grid frequency security according to claim 1, characterized in that: The method for calculating the frequency change rate according to the system inertia margin includes: Obtain power surge, power on / off status, system load, and motor load; The frequency change rate is calculated according to the power impact, the start / stop state of the power supply, the load of the system, and the load of the motor.

4. The method for online analysis of power grid frequency security according to claim 1, characterized in that: The evaluating the system inertia margin and obtaining the inertia margin evaluation result includes: Obtain the minimum inertia margin under the typical operation mode of the current regional power grid; The system inertia margin and the minimum inertia margin are compared. When the system inertia margin is greater than or equal to the minimum inertia margin, the inertia margin evaluation result indicates that the frequency safety margin is sufficient.

5. The method for online analysis of power grid frequency security according to claim 4, characterized in that: The step of evaluating the system inertia margin and obtaining an inertia margin evaluation result further includes: When the system inertia margin is less than the minimum inertia margin, the inertia margin assessment result is that the frequency safety margin is insufficient, and the current operation mode of the power grid is adjusted.

6. The method for online analysis of power grid frequency security according to claim 1, characterized in that: The determining, based on the frequency change rate and the frequency safety influencing factors, whether there is a safe operation domain of the power grid frequency includes: Obtain the maximum power impact under the current operation mode of the power grid; Obtain the load inertia characteristics under the current operation mode of the power grid; Obtaining a power supply equivalent rotational kinetic energy requirement based on the maximum power impact and the load inertia characteristics; Get the start and stop combination of the unit; and According to the start-stop combination of the unit and the equivalent rotational kinetic energy demand of the power supply, it is determined whether there is a safe operating domain of the grid frequency.

7. The method for online analysis of power grid frequency security according to claim 5, characterized in that: When the start-stop combination of the unit meets the equivalent rotational kinetic energy requirement of the power supply, there is a safe operating domain of the grid frequency. When the start-stop combination of the unit does not meet the equivalent rotational kinetic energy requirement of the power supply, there is no safe operating domain of the grid frequency.

8. The method for online analysis of power grid frequency security according to claim 6, characterized in that: The obtaining of the maximum power impact under the current operation mode of the power grid includes: Obtain voltage shock and power shock under the current operation mode of the power grid; According to the voltage impact and power impact under the current operation mode of the power grid, the maximum impact power under the current operation mode of the power grid is obtained.

9. The method for online analysis of power grid frequency security according to claim 6, characterized in that: The obtaining of load inertia characteristics under the current operation mode of the power grid includes: Obtain the motor inertia and load size under the current operation mode of the power grid; According to the motor inertia and load size under the current operation mode of the power grid, the load inertia characteristics under the current operation mode of the power grid are obtained.

10. A power grid frequency security online analysis device, applicable to the power grid frequency security online analysis method according to any one of claims 1 to 9, characterized in that: include: System inertia margin acquisition module, used to obtain system inertia margin; A frequency change rate calculation module, configured to obtain a calculation method for the frequency change rate based on the system inertia margin; A frequency safety influencing factor acquisition module, configured to acquire the frequency safety influencing factor according to the frequency change rate calculation method; An inertia margin evaluation result acquisition module is used to evaluate the system inertia margin and obtain an inertia margin evaluation result; as well as a safe operation domain judgment module, configured to judge whether there is a safe operation domain of the power grid frequency according to the frequency change rate and the frequency safety influencing factors; The power grid frequency security analysis module is used to analyze the power grid frequency security under the current operation mode according to the inertia margin evaluation result and the existence of the safe operation domain.

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