A method and system for evaluating power grid frequency safety margin

Abstract

The application provides a power grid frequency safety margin evaluation method and system, comprising the following steps: determining inertia ratio of the inertia margin demarcation point of the power grid system based on the inertia of the inertia margin demarcation point and the inertia of the inflection point corresponding to the relationship curve between the frequency deviation amplitude and the system inertia of the power grid system; determining inertia ratio of the actual operating point of the power grid system based on the inertia of the actual operating point of the power grid system and the inertia of the inflection point; and evaluating the safety margin of the power grid frequency based on the inertia ratio of the inertia margin demarcation point and the inertia ratio of the actual operating point of the power grid system. The technical scheme realizes the rapid evaluation of the safety margin of the power grid frequency by constructing the inertia ratio index of the frequency stability characteristic analysis model and the system of the power grid system.

Description

Technical Field

[0001] This invention relates to the field of power system large power grid safety and stability control technology, specifically to a method and system for evaluating the frequency security margin of a power grid. Background Technology

[0002] As new energy sources such as wind and solar power, along with high-voltage, high-power direct current (DC) transmission, gradually become the dominant form of new power systems, the power system is exhibiting highly electronic characteristics and will gradually evolve into a low-inertia power system with high DC and new energy penetration. With the rapid increase in the proportion of new energy sources, some power grids are showing signs of hollowing out conventional power sources, exacerbating the decline in system rotational inertia and significantly increasing frequency stability risks. Rapidly assessing the frequency stability level of power grids with a high proportion of new energy sources has become a focus of attention for power grid operators and research institutions.

[0003] Existing methods for assessing power grid frequency stability do not consider the impact of security control measures on system frequency stability, making it difficult to guarantee the effectiveness and accuracy of the assessment results and limiting their applicability. Summary of the Invention

[0004] To address the shortcomings of existing power grid frequency stability assessment methods, such as difficulty in guaranteeing the validity and accuracy of assessment results and limited applicability, this invention proposes a method for evaluating the adequacy of power grid frequency security, comprising:

[0005] The inertia ratio of the dividing point is determined based on the moment of inertia corresponding to the dividing point of the moment of inertia adequacy of the power grid system and the moment of inertia corresponding to the inflection point of the curve relating the amplitude of the frequency deviation of the power grid system to the moment of inertia of the system.

[0006] The inertia ratio of the actual operating point is determined based on the moment of inertia corresponding to the actual operating point of the power grid system and the moment of inertia corresponding to the inflection point of the relationship curve.

[0007] The safety margin of the power grid frequency is assessed based on the inertia ratio at the boundary point and the inertia ratio at the actual operating point.

[0008] The relationship curve is the relationship curve between the amplitude of the system frequency deviation and the system moment of inertia obtained based on a pre-constructed power grid system frequency stability characteristic analysis model.

[0009] The power grid system frequency stability characteristic analysis model is constructed from the system frequency response transfer function considering security control measures.

[0010] Preferably, the determination of the inertia ratio at the boundary point based on the moment of inertia corresponding to the boundary point of the power grid system's moment of inertia adequacy and the moment of inertia corresponding to the inflection point of the curve relating the power grid system's frequency deviation amplitude to the system's moment of inertia includes:

[0011] Substitute the system parameters of the power grid system into the formula for calculating the moment of inertia corresponding to the inflection point to obtain the moment of inertia corresponding to the inflection point.

[0012] Set the margin index of the rotational inertia of the power grid system based on the rotational inertia corresponding to the inflection point.

[0013] The margin index is used as the inertia ratio at the dividing point.

[0014] Preferably, the determination of the inertia ratio at the boundary point based on the moment of inertia corresponding to the boundary point of the power grid system's moment of inertia adequacy and the moment of inertia corresponding to the inflection point of the curve relating the power grid system's frequency deviation amplitude to the system's moment of inertia includes:

[0015] Substitute the system parameters of the power grid system into the formula for calculating the moment of inertia corresponding to the inflection point to obtain the moment of inertia corresponding to the inflection point.

[0016] Find the first derivative k corresponding to the inflection point. d According to the first derivative k d The slope of the relationship curve calculated by the pre-constructed power grid system frequency stability characteristic analysis model is k. d The moment of inertia corresponding to point / a, where a is the slope coefficient, and the slope is k. d The moment of inertia corresponding to point / a is taken as the moment of inertia corresponding to the dividing point.

[0017] The inertia ratio of the dividing point is obtained by the ratio of the moment of inertia corresponding to the dividing point to the moment of inertia corresponding to the inflection point.

[0018] Preferably, the frequency stability characteristic analysis model of the power grid system is shown in the following equation:

[0019]

[0020] Where s is the Laplace operator, Δf(s) is the complex function of the frequency variation of the power grid system, and ΔP L The active power disturbance of the power grid system, t c The delay time for the safety control device's operation is given by k, the tripping ratio coefficient of the safety control device is given by H, the inertial time constant is given by D, and the damping coefficient is given by D. is the convergence factor.

[0021] Preferably, determining the inertia ratio of the actual operating point based on the moment of inertia corresponding to the actual operating point of the power grid system and the moment of inertia corresponding to the inflection point of the relationship curve includes:

[0022] Substitute the system parameters of the power grid system into the formula for calculating the moment of inertia corresponding to the inflection point to obtain the moment of inertia corresponding to the inflection point.

[0023] The moment of inertia corresponding to the actual operating point is obtained based on the number of units started at the actual operating point of the power grid system.

[0024] The inertia ratio of the actual operating point is obtained by the ratio of the moment of inertia corresponding to the actual operating point to the moment of inertia corresponding to the inflection point.

[0025] Preferably, the formula for calculating the moment of inertia corresponding to the inflection point is as follows;

[0026]

[0027] Among them, J tp Let S be the moment of inertia corresponding to the inflection point of the curve relating the frequency deviation amplitude of the power grid system to the system's moment of inertia, where D is the damping coefficient and S is the moment of inertia. N The system capacity is ω0, the initial speed of the unit is t. c Delay the operation of the safety control device.

[0028] Preferably, the assessment of the safety margin of the power grid frequency based on the inertia ratio at the boundary point and the inertia ratio at the actual operating point includes:

[0029] When the inertia ratio at the actual operating point is greater than the inertia ratio at the boundary point, the power grid system is in a state of sufficient rotational inertia.

[0030] When the inertia ratio at the actual operating point is greater than 1 and less than the inertia ratio at the boundary point, the power grid system is in a state where the rotational inertia is sufficient but not abundant.

[0031] When the inertia ratio at the actual operating point is less than 1, the power grid system is in a state of insufficient rotational inertia.

[0032] Based on the same inventive concept, this invention also proposes an evaluation system for the frequency security margin of a power grid, comprising:

[0033] The inertia ratio determination unit at the boundary point is used to determine the inertia ratio at the boundary point based on the rotational inertia corresponding to the boundary point of the rotational inertia adequacy of the power grid system and the rotational inertia corresponding to the inflection point of the curve relating the amplitude of the frequency deviation of the power grid system to the rotational inertia of the system.

[0034] The inertia ratio determination unit for actual operating points is used to determine the inertia ratio of the actual operating point based on the rotational inertia corresponding to the actual operating point of the power grid system and the rotational inertia corresponding to the inflection point of the relationship curve.

[0035] An evaluation unit is used to evaluate the frequency security margin of the power grid system based on the inertia ratio at the boundary point and the inertia ratio at the actual operating point.

[0036] The relationship curve is the relationship curve between the amplitude of the system frequency deviation and the system moment of inertia obtained based on a pre-constructed power grid system frequency stability characteristic analysis model.

[0037] The power grid system frequency stability characteristic analysis model is constructed from the system frequency response transfer function considering security control measures.

[0038] Preferably, the evaluation unit includes:

[0039] The comparison subunit is used to compare the inertia ratio of the actual running point with the inertia ratio of the boundary point and the inertia ratio of the inflection point;

[0040] The determination subunit is used to determine the frequency security adequacy level of the power grid system based on the comparison result of the comparison subunit.

[0041] Preferably, it also includes a model building unit for constructing a power grid system frequency stability characteristic analysis model from the system frequency response transfer function.

[0042] Preferably, the frequency stability characteristic analysis model of the power grid system is shown in the following equation:

[0043]

[0044] Where s is the Laplace operator, Δf(s) is the complex function of the frequency variation of the power grid system, and ΔP L The active power disturbance of the power grid system, t c The delay time for the safety control device is denoted by ; k is the proportional control coefficient for switching off the device, H is the inertial time constant, and D is the damping coefficient. is the convergence factor.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] The method and system for evaluating the frequency security margin of the power grid provided by this invention obtains the relationship curve between the amplitude of the system frequency deviation and the system rotational inertia, as well as the rotational inertia corresponding to the inflection point of the curve, by constructing an analysis model of the frequency stability characteristics of the power grid system. Furthermore, it constructs an inertia ratio index and achieves rapid assessment of the frequency security margin of the power grid by comparing the inertia ratio at the actual operating point with the inertia ratio at the boundary point of the system rotational inertia margin and the inertia ratio at the inflection point of the curve. Attached Figure Description

[0047] Figure 1 A flowchart of the power grid frequency security margin evaluation method provided by the present invention;

[0048] Figure 2 A schematic diagram of the frequency response characteristics of a power grid system under different security control coefficients;

[0049] Figure 3 A schematic diagram of the frequency response model of a single-machine system taking security control measures into account;

[0050] Figure 4 A schematic diagram showing the variation of the frequency deviation amplitude of the power grid system with the moment of inertia under different disturbances and tripping times;

[0051] Figure 5 This is a schematic diagram of the first method for determining the boundary point of the rotational inertia margin of a power grid system provided by the present invention;

[0052] Figure 6 This is a schematic diagram of the second method for determining the boundary point of the rotational inertia margin of a power grid system provided by the present invention. Detailed Implementation

[0053] This invention discloses a method and system for evaluating the frequency security margin of a power grid. By constructing an analysis model of the frequency stability characteristics of a power grid system and an inertia ratio index, it enables a rapid assessment of the frequency security margin of the power grid and provides a powerful analytical and evaluation method for studying the evolution law of the frequency stability characteristics of a power grid system.

[0054] Example 1:

[0055] A method for evaluating the frequency security adequacy of a power grid, such as... Figure 1 As shown, it includes:

[0056] Step 1: Determine the inertia ratio at the boundary point based on the moment of inertia corresponding to the boundary point of the power grid system's moment of inertia adequacy and the moment of inertia corresponding to the inflection point of the curve relating the power grid system's frequency deviation amplitude to the system's moment of inertia.

[0057] Step 2: Determine the inertia ratio of the actual operating point based on the moment of inertia corresponding to the actual operating point of the power grid system and the moment of inertia corresponding to the inflection point of the relationship curve;

[0058] Step 3: Assess the safety margin of the power grid frequency based on the inertia ratio at the boundary point and the inertia ratio at the actual operating point;

[0059] Among them, the relationship curve is the relationship curve between the amplitude of the system frequency deviation and the system rotational inertia obtained based on the pre-constructed power grid system frequency stability characteristic analysis model; the power grid system frequency stability characteristic analysis model is constructed from the system frequency response transfer function considering security control measures.

[0060] The technical solution of the present invention will be described in detail below using a power grid system in a new energy sending area as an example.

[0061] Considering a region with a high proportion of renewable energy transmission, the load level of the power grid under winter off-peak conditions is approximately 78,000 MW, the DC transmission capacity is approximately 35,000 MW, the operating capacity of conventional generating units is approximately 100,000 MW, and the actual system rotational inertia is approximately 8,600 tm. 2 In this mode, if a bipolar blocking fault occurs in a certain ultra-high voltage DC transmission line (capacity 8000MW), it is necessary to quickly assess the frequency safety margin of the power grid system under this disturbance.

[0062] Before step 1, the following steps are also included: constructing an analysis model of the frequency stability characteristics of the power grid system.

[0063] Frequency stability characteristic analysis model considering stabilization measures, such as Figure 3 As shown, taking into account the number of machine switching operations due to security control measures, the frequency domain expression for the system frequency change is:

[0064]

[0065] Where Δf is the frequency deviation, D is the damping coefficient, R is the system droop coefficient, and F is the system droop coefficient. H T is the high-pressure cylinder capacity coefficient. R K is the reheat time constant. m P is the gain factor. s ΔP represents the total active power cut-off. L Let ωn be the active power disturbance of the power system, and ωn be the angular frequency. The damping ratio is denoted as .

[0066]

[0067] Where H is the inertial time constant, and the unit is seconds.

[0068]

[0069] Since the frequency change under the disturbance fault is mainly constrained by the system inertia and the total active power cut-off under safety control within the hundreds of milliseconds after a large system disturbance, the primary frequency regulation capability of the unit has a relatively small impact on the frequency and can be approximately ignored. Therefore, the frequency domain expression of the system frequency change can be simplified as follows:

[0070]

[0071] Where s is the Laplace operator, t c The delay time for the safety control device is denoted by k, which is the tripping ratio coefficient of the safety control device, and k ≥ 0.7. is the convergence factor.

[0072] Perform an inverse Laplace transform on the above equation, and then... Substituting the values, we obtain the analytical expression for the frequency extrema of the system under large disturbances as follows:

[0073]

[0074] Where J is the minimum moment of inertia under the system frequency stability constraint, and S N Let ω be the system capacity and ω0 be the initial speed of the unit. The minimum rotational inertia requirement of the system under frequency stability constraints can be derived as follows:

[0075]

[0076] Based on the frequency stability characteristic analysis model considering stability measures, the relationship curves between the frequency deviation amplitude and the system moment of inertia of the power grid system under different disturbances are as follows: Figure 4 As shown. By Figure 4 It can be seen that the smaller the system's moment of inertia, the greater the frequency deviation under the same switching time.

[0077] The following evaluation method is applicable to the large disturbance mode of the power grid, and its implementation premises are as follows: The sending-end power grid; under large disturbances, the safety control action time is on the order of hundreds of milliseconds, and the safety control device tripping ratio is greater than 0.7; after the safety control action, the system frequency no longer increases but shows a downward trend, such as... Figure 2 As shown.

[0078] Step 1 specifically includes:

[0079] 1.1 Substitute the system parameters of the power grid system into the formula for calculating the moment of inertia at the inflection point of the curve relating frequency deviation amplitude and system moment of inertia to obtain the moment of inertia corresponding to the inflection point.

[0080] Using the concept of the concavity and convexity of a function, the moment of inertia corresponding to the inflection point of the frequency deviation change under a specific disturbance can be calculated. The formula for calculating the moment of inertia corresponding to the inflection point is:

[0081]

[0082] Among them, J tp This is the moment of inertia corresponding to the inflection point of the curve relating the frequency deviation amplitude of the power grid system to the system's moment of inertia. By substituting the system parameters of the power grid system, including damping coefficient, system capacity, initial unit speed, and the operating delay of safety control devices, into the above formula, the moment of inertia corresponding to the inflection point can be obtained.

[0083] From the above equation, we can see that the inflection point corresponds to the moment of inertia J. tp Determined by variables such as system damping coefficient and stabilization action time, for a specific operating mode of the power system, J tp The value is constant and greater than the system's minimum moment of inertia J.

[0084] 1.2 Determine the inertia ratio at the boundary point of inertia adequacy based on the moment of inertia corresponding to the inflection point.

[0085] Depend on Figure 4 It can be seen that to the right of the inflection point, the absolute value of the curve slope is smaller, the system frequency stability level is less affected by the change in moment of inertia, and the system frequency is relatively stable; to the left of the inflection point, the absolute value of the curve slope is larger, and a small decrease in moment of inertia will cause a large increase in frequency deviation, resulting in a rapid deterioration of the frequency stability level.

[0086] Therefore, the inertia ratio index can be constructed as an evaluation index for the adequacy of frequency stability level, further realizing the evaluation of system inertia adequacy. The system inertia ratio index shows a linear trend with the change of system rotational inertia. Therefore, by defining the boundary between the system inertia ratio margin and the sufficient region, that is, the dividing point of rotational inertia adequacy, the frequency stability level of large-scale power transmission systems can be quickly assessed.

[0087] Depend on Figure 4 It can be seen that when the system operating point is far from the inflection point of rotational inertia, the rotational inertia is close to the flat region on the right side of the curve, the system inertia ratio is relatively large, the inertia margin is sufficient, and the frequency stability level is high. When the system operating point is close to the inflection point of rotational inertia, the system inertia ratio is close to 1, the system can guarantee frequency stability, but the inertia margin is small, and there is a risk of frequency instability. Therefore, in order to accurately assess and judge the adequacy of system inertia at the power grid operating point, a boundary is set between the inertia ratio margin and the sufficient region, that is, a rotational inertia adequacy dividing point is set, and the system inertia is divided into three levels: sufficient inertia, inertia margin, and insufficient inertia.

[0088] There are two methods for determining the moment ratio at the boundary point of moment of inertia margin:

[0089] The first type:

[0090] like Figure 5 As shown, the moment of inertia J corresponding to the inflection point of the curve relating the frequency deviation amplitude to the system's moment of inertia is calculated. tp Based on this, and considering the stability characteristics of the actual power grid system, the rotational inertia margin index k is given. m Let the moment of inertia be k. m ·J tp The point is the boundary point for the margin of rotational inertia, and the moment of inertia J1 at this boundary point is k. m ·J tp Then the inertia ratio index ρ1 = k at the dividing point m Margin index k m The value is typically between 1.2 and 1.4. In this embodiment, k m The value is set to 1.3, meaning the inertia ratio index at the dividing point of the moment of inertia adequacy is 1.3.

[0091] The main advantage of this method is that it is relatively easy to understand, and with a full understanding of the characteristics of the power grid, it can more accurately achieve the system's rotational inertia margin and sufficient grading.

[0092] The second type:

[0093] like Figure 6 As shown, the moment of inertia J corresponding to the inflection point of the curve relating the frequency deviation amplitude to the system's moment of inertia is calculated. tp Based on this, find the first derivative k corresponding to the inflection point. d Since the change in moment of inertia is relatively gradual when the system's operating point is far from the inflection point of moment of inertia, the slope is defined as k. d The point / a is the boundary between the inertia ratio margin and the sufficient region, i.e., the slope is k. d The point / a is the boundary point for the margin of rotational inertia, where 'a' is a coefficient that can be flexibly chosen based on the system's stability characteristics, typically between 2 and 3. The inertia J1 at the boundary point for the margin of rotational inertia can be determined by the slope k. d / a is obtained by reverse calculation, then the inertia ratio index ρ1 = J1 / J at the boundary of rotational inertia margin. tp .

[0094] The main advantage of this method is that the system can adaptively adjust the moment of inertia margin boundary point ρ1 under different frequency difference disturbances.

[0095] Step 2 specifically includes:

[0096] 2.1 Substitute the system parameters of the power grid system into the inflection point J tp The formula for calculating the moment of inertia is used to obtain the moment of inertia corresponding to the inflection point.

[0097] 2.2 Obtain the moment of inertia corresponding to the actual operating point based on the number of units started at the actual operating point of the power grid system.

[0098] In this embodiment, the rotational inertia at the actual operating point of the system can be calculated to be approximately 8600 tm based on real-time monitoring of the number of grid units in operation. 2 ,tm 2 It is measured in tons per square meter.

[0099] 2.3 The inertia ratio of the actual operating point can be obtained by the ratio of the moment of inertia corresponding to the actual operating point to the moment of inertia corresponding to the inflection point.

[0100] The formula for calculating the inertia ratio at the actual operating point of the system is:

[0101]

[0102] Where, ρ op J is the inertia ratio at the actual operating point of the system. tp J is the moment of inertia corresponding to the inflection point. act This represents the moment of inertia corresponding to the actual operating point of the system.

[0103] Step 3 includes:

[0104] The inertia ratio ρ at the actual operating point of the power grid system op The inertia ratio ρ1 is compared with the inertia margin at the boundary point of rotational inertia margin to assess the frequency security margin of the power grid. When ρ op When ρ is greater than 1, the system inertia is sufficient, and the maximum fluctuation value of the power grid frequency will not change significantly under different system disturbances; when 1 < ρ op When ρ < 1, the system inertia is in a state of surplus but not sufficient. High-power DC disturbances will cause a short-term increase in the grid frequency. Although the overall system can still remain stable, there is still a certain frequency security risk in some local areas; when ρ op When the inertia ratio is less than 1, the inertia ratio at the actual operating point of the system is located to the left of the inflection point of the curve relating the frequency deviation amplitude to the system's moment of inertia. This indicates insufficient system inertia, making it difficult to cope with the impact of DC faults and posing a risk of frequency instability. Therefore, the rapid assessment criterion for the frequency stability level of large-scale power transmission systems is as follows:

[0105]

[0106] In this embodiment, the maximum allowable frequency deviation Δf of the system max With a frequency of 0.6Hz, substituting the system parameters into the following formula, the minimum rotational inertia requirement of the system under an 8000MW disturbance can be calculated to be 6200tm. 2 .

[0107]

[0108] The system damping coefficient D and the system capacity S N Initial unit speed ω0, safety control device action delay parameter t c Substitute J tp The formula can be used to calculate the moment of inertia J corresponding to the inflection point of the curve relating the frequency deviation amplitude to the system's moment of inertia. tp 8250tm 2 According to ρ op =J act / J tp The inertia ratio at the actual operating point of the power grid system is 1.04. Since the inertia ratio of 1.04 at the actual operating point of the power grid system is between 1 and the inertia ratio of 1.3, which is the dividing point of sufficient rotational inertia, the system is in an inertia margin state. The overall frequency stability level of the system meets the operating requirements. However, the inertia margin needs to be monitored during operation, and if necessary, measures such as increasing the number of conventional generating units should be taken to ensure the safety of the power grid frequency.

[0109] Example 2:

[0110] A system for evaluating the frequency security margin of a power grid, comprising:

[0111] The inertia ratio determination unit at the boundary point is used to determine the inertia ratio at the boundary point based on the rotational inertia corresponding to the boundary point of the rotational inertia margin of the power grid system and the rotational inertia corresponding to the inflection point of the curve relating the amplitude of the frequency deviation of the power grid system to the rotational inertia of the system.

[0112] The inertia ratio determination unit for actual operating points is used to determine the inertia ratio for actual operating points based on the rotational inertia corresponding to the actual operating points of the power grid system and the rotational inertia corresponding to the inflection point of the relationship curve.

[0113] An evaluation unit is used to evaluate the frequency security margin of the power grid system based on the inertia ratio at the boundary point and the inertia ratio at the actual operating point.

[0114] The relationship curve between the frequency deviation amplitude and the system's moment of inertia was obtained based on a pre-constructed power grid system frequency stability characteristic analysis model; the power grid system frequency stability characteristic analysis model was constructed from the system frequency response transfer function considering security control measures.

[0115] The evaluation units include:

[0116] The comparison sub-unit is used to compare the inertia ratio at the actual operating point with the inertia ratio at the boundary point and the inertia ratio at the inflection point;

[0117] The determination subunit is used to determine the frequency security adequacy level of the power grid system based on the comparison results of the comparison subunit.

[0118] In this embodiment, the method for determining the frequency security margin level is as follows:

[0119] When the inertia ratio at the actual operating point of the power grid system is greater than the inertia ratio at the boundary point of sufficient rotational inertia, the power grid system is in a state of sufficient rotational inertia.

[0120] When the inertia ratio at the actual operating point of the power grid system is greater than 1 and less than the inertia ratio at the boundary point of rotational inertia sufficiency, the power grid system is in a state of surplus but not sufficiency of rotational inertia.

[0121] When the inertia ratio at the actual operating point of the power grid system is less than 1, the power grid system is in a state of insufficient rotational inertia.

[0122] The evaluation system also includes a model building unit, which is used to construct an analysis model of the frequency stability characteristics of the power grid system from the system frequency response transfer function.

[0123] The frequency stability characteristic analysis model of the power grid system is shown in the following equation:

[0124]

[0125] Where s is the Laplace operator, Δf(s) is the complex function of the frequency variation of the power grid system, and ΔP L The active power disturbance of the power grid system, t c The delay time for the safety control device's operation is given by k, the proportional control coefficient for the device's tripping mechanism is given by H, the inertial time constant is given in seconds, and D is the damping coefficient. is the convergence factor.

[0126] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0127] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0128] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0129] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0130] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of the claims of the present invention pending approval.

Claims

1. A method for evaluating the frequency security adequacy of a power grid, characterized in that, include: The inertia ratio of the dividing point is determined based on the moment of inertia corresponding to the dividing point of the moment of inertia adequacy of the power grid system and the moment of inertia corresponding to the inflection point of the curve relating the amplitude of the frequency deviation of the power grid system to the moment of inertia of the system. The inertia ratio of the actual operating point is determined based on the moment of inertia corresponding to the actual operating point of the power grid system and the moment of inertia corresponding to the inflection point of the relationship curve. The safety margin of the power grid frequency is assessed based on the inertia ratio at the boundary point and the inertia ratio at the actual operating point. The relationship curve is the relationship curve between the amplitude of the system frequency deviation and the system moment of inertia obtained based on a pre-constructed power grid system frequency stability characteristic analysis model. The frequency stability characteristic analysis model of the power grid system is constructed from the system frequency response transfer function considering security control measures; The inertia ratio at the dividing point is determined by the inertia corresponding to the dividing point of the inertia adequacy of the power grid system and the inertia corresponding to the inflection point of the curve relating the amplitude of the power grid system frequency deviation to the system's inertia. This includes: Substitute the system parameters of the power grid system into the formula for calculating the moment of inertia corresponding to the inflection point to obtain the moment of inertia corresponding to the inflection point. Set the margin index of the rotational inertia of the power grid system based on the rotational inertia corresponding to the inflection point. The margin index is used as the inertia ratio at the dividing point; The formula for calculating the moment of inertia corresponding to the inflection point is as follows: in, J tp Let be the moment of inertia corresponding to the inflection point of the curve relating the frequency deviation amplitude of the power grid system to the system's moment of inertia. D The damping coefficient is... S N For system capacity, This is the initial speed of the unit. t c Delay the operation of the safety control device.

2. The evaluation method as described in claim 1, characterized in that, The inertia ratio at the dividing point is determined by the inertia corresponding to the dividing point of the inertia adequacy of the power grid system and the inertia corresponding to the inflection point of the curve relating the amplitude of the power grid system frequency deviation to the system's inertia. This includes: Substitute the system parameters of the power grid system into the formula for calculating the moment of inertia corresponding to the inflection point to obtain the moment of inertia corresponding to the inflection point. Find the first derivative corresponding to the inflection point. k d According to the first derivative k d The slope of the relationship curve calculated by the pre-constructed power grid system frequency stability characteristic analysis model is... k d / a The moment of inertia corresponding to the point, where, a The slope coefficient is the slope value. k d / a The moment of inertia corresponding to the point is taken as the moment of inertia corresponding to the dividing point. The inertia ratio of the dividing point is obtained by the ratio of the moment of inertia corresponding to the dividing point to the moment of inertia corresponding to the inflection point.

3. The evaluation method as described in claim 2, characterized in that, The frequency stability characteristic analysis model of the power grid system is shown in the following equation: Where s is the Laplace operator, It is a complex function of the frequency variation of the power grid system. This represents the active power disturbance in the power grid system. t c To delay the operation of the safety control device, This refers to the switching ratio coefficient of the safety control device. H The inertial time constant, D The damping coefficient is... is the convergence factor.

4. The evaluation method as described in claim 1, characterized in that, The determination of the inertia ratio at the actual operating point based on the moment of inertia corresponding to the actual operating point of the power grid system and the moment of inertia corresponding to the inflection point of the relationship curve includes: Substitute the system parameters of the power grid system into the formula for calculating the moment of inertia corresponding to the inflection point to obtain the moment of inertia corresponding to the inflection point. The moment of inertia corresponding to the actual operating point is obtained based on the number of units started at the actual operating point of the power grid system. The inertia ratio of the actual operating point is obtained by the ratio of the moment of inertia corresponding to the actual operating point to the moment of inertia corresponding to the inflection point.

5. The evaluation method as described in claim 1, characterized in that, The assessment of the safety margin of the power grid frequency based on the inertia ratio at the boundary point and the inertia ratio at the actual operating point includes: When the inertia ratio at the actual operating point is greater than the inertia ratio at the boundary point, the power grid system is in a state of sufficient rotational inertia. When the inertia ratio at the actual operating point is greater than 1 and less than the inertia ratio at the boundary point, the power grid system is in a state where the rotational inertia is sufficient but not abundant. When the inertia ratio at the actual operating point is less than 1, the power grid system is in a state of insufficient rotational inertia.

6. A power grid frequency security adequacy evaluation system, used to implement the method as described in claim 1, characterized in that, include: The inertia ratio determination unit at the boundary point is used to determine the inertia ratio at the boundary point based on the rotational inertia corresponding to the boundary point of the rotational inertia adequacy of the power grid system and the rotational inertia corresponding to the inflection point of the curve relating the amplitude of the frequency deviation of the power grid system to the rotational inertia of the system. The inertia ratio determination unit for actual operating points is used to determine the inertia ratio of the actual operating point based on the rotational inertia corresponding to the actual operating point of the power grid system and the rotational inertia corresponding to the inflection point of the relationship curve. An evaluation unit is used to evaluate the frequency security margin of the power grid system based on the inertia ratio at the boundary point and the inertia ratio at the actual operating point. The relationship curve is the relationship curve between the amplitude of the system frequency deviation and the system moment of inertia obtained based on a pre-constructed power grid system frequency stability characteristic analysis model. The power grid system frequency stability characteristic analysis model is constructed from the system frequency response transfer function that takes into account security control measures.

7. The evaluation system as described in claim 6, characterized in that, The evaluation unit includes: The comparison subunit is used to compare the inertia ratio of the actual running point with the inertia ratio of the boundary point and the inertia ratio of the inflection point; The determination subunit is used to determine the frequency security adequacy level of the power grid system based on the comparison result of the comparison subunit.

8. The evaluation system as described in claim 6, characterized in that, It also includes a model building unit, used to construct a power grid system frequency stability characteristic analysis model from the system frequency response transfer function.

9. The evaluation system as described in claim 8, characterized in that, The frequency stability characteristic analysis model of the power grid system is shown in the following equation: Where s is the Laplace operator, It is a complex function of the frequency variation of the power grid system. This represents the active power disturbance in the power grid system. t c Delay for the operation of safety control devices; This refers to the switching ratio coefficient of the safety control device. H The inertial time constant, D The damping coefficient is... is the convergence factor.

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