An evaluation method for the asynchronous power supply carrying capacity

Abstract

The present application provides a method for evaluating the asynchronous power carrying capacity. The technical solution first constructs a full-unit frequency response model, and determines the maximum expected value of the asynchronous power carrying capacity and the corresponding starting mode, equivalent inertia constant, and lower limit of mechanical power through initial optimization. Then, a pre-conceived fault is set, and the frequency safety index is obtained by substituting it into the model for simulation. If the safety threshold is not met and the carrying capacity ≥ 200 MW, with the minimum equivalent inertia as the objective function, combined with the double lower limit constraints of inertia and power increment, secondary optimization is carried out to dynamically update the starting mode and parameters, and the loop verification is performed until the frequency safety reaches the standard. It can obtain the frequency safety index more accurately; compared with the method of optimizing the starting by increasing the system equivalent inertia constant, it considers the index representing the change of the frequency extreme value, can stably reduce the frequency extreme value, has a better starting optimization effect, and a faster evaluation speed.

Description

Technical Field

[0001] The present application relates to the field of electrical engineering, and specifically to the field of new energy power systems. Background Art

[0002] Asynchronous power sources such as direct current, wind power, and photovoltaic power are entering a period of rapid development. However, due to the relatively scattered distribution of the above-mentioned asynchronous energy sources, the main energy bases are generally located in remote areas with few people or a small number of people, which are far away from the actual and core power consumption areas. Therefore, high-voltage direct current is required for long-distance power transmission. However, due to the non-dispatchability, weak grid-related performance, and low inertia of asynchronous power sources, as well as multiple factors such as grid security constraints, the power system faces severe challenges in carrying large-scale asynchronous energy. Therefore, it is urgent to propose an evaluation method for the carrying capacity of asynchronous power sources that takes frequency safety into consideration, so as to reasonably plan the power feed-in power of asynchronous power sources in the grid and reduce the risk of system frequency instability when a high proportion of asynchronous power sources are connected.

[0003] However, the current methods for evaluating the carrying capacity of non-synchronous power sources mostly use time domain simulation methods to obtain high-precision frequency safety indicators, but the solution time is too long; or the equivalent model method is used, because the nonlinear links in the synchronous machine frequency response model are not considered, and simplified models are often used, the solution time is short, but the obtained frequency safety indicators are of low accuracy. In addition, many studies are based on the original startup method, and the non-synchronous power supply replaces the synchronous machine to evaluate the carrying capacity of non-synchronous power sources. In actual operation, the non-starting units can be considered, and the startup method can be optimized to obtain the optimal solution. Therefore, the existing non-synchronous power supply carrying capacity evaluation method cannot accurately describe the limit of the non-synchronous power supply carrying capacity of the power system. Summary of the invention

[0004] In order to overcome the above technical defects, the present application provides a method for evaluating the carrying capacity of an asynchronous power supply, comprising:

[0005] Step S101: Acquire power system frequency response data;

[0006] Based on the power system frequency response data, construct a frequency response model of multiple machines of the whole unit;

[0007] Step S102: Initially optimize the asynchronous power supply carrying capacity in the multi-machine frequency response model of the whole unit to obtain the expected value of the maximum asynchronous power supply carrying capacity and the sum of the current first startup mode, the first equivalent inertia constant of the current startup unit and the first mechanical power of the current startup unit;

[0008] Determine the lower limit of the first equivalent inertia constant of the currently powered-on unit and the lower limit of the sum of the first mechanical power increment of the currently powered-on unit according to the sum of the first equivalent inertia constant of the currently powered-on unit and the first mechanical power of the currently powered-on unit;

[0009] Step S103: Set the anticipated fault;

[0010] Step S104, Substitute the current first startup mode into the multi - machine frequency response model of the whole unit for simulation to obtain the current first frequency safety index;

[0011] Step S105: Determine whether the current first frequency safety index meets the first preset condition;

[0012] If so, take the expected value of the maximum asynchronous power - carrying capacity as the asynchronous power - carrying capacity under the anticipated fault of the power system;

[0013] If not, and when the current expected value of the maximum asynchronous power - carrying capacity is greater than or equal to 200 MW, then execute the next step S106;

[0014] Step S106: Take the first minimum equivalent inertia constant as the first objective function, and the constraint conditions of the first objective function include the lower limit of the first equivalent inertia constant of the currently - started units and the lower limit of the sum of the first mechanical power increments of the currently - started units;

[0015] Step S107: Determine whether the first objective function has a solution;

[0016] Step S108: If the first objective function has a solution, update the current startup mode to obtain the current second startup mode, the sum of the second mechanical powers of the currently - started units, and the second equivalent inertia constant of the currently - started units;

[0017] Update the current first startup mode according to the current second startup mode;

[0018] Update the lower limit of the first equivalent inertia constant and the lower limit of the sum of the first mechanical power increments according to the sum of the second mechanical powers of the currently - started units and the second equivalent inertia constant of the currently - started units, and return to step S104.

[0019] Optionally, when the judgment result of step S107 is that there is no solution, it includes:

[0020] Step S201: Based on the secant method, update the current first expected value of the asynchronous power - carrying capacity and the change amount of the current first expected value of the asynchronous power - carrying capacity;

[0021] Step S202: Take the second minimum equivalent inertia constant as the second objective function, and the constraint conditions of the second objective function are the same as the constraint conditions for the initial optimization of the asynchronous power - carrying capacity in the multi - machine frequency response model of the whole unit;

[0022] Step S203: Determine whether the second objective function has a solution;

[0023] Step S204: If the second objective function has a solution, update the current startup mode to obtain the current third startup mode, the sum of the third mechanical powers of the currently started units, and the third equivalent inertia constant of the currently started units;

[0024] Determine the lower limit of the second equivalent inertia constant of the currently started units and the lower limit of the sum of the second mechanical power increments of the currently started units according to the sum of the third mechanical powers of the currently started units and the third equivalent inertia constant of the currently started units, and perform the next step S205;

[0025] If the second objective function has no solution, after adding 1 to the iteration count, return to step S201.

[0026] Step S205: Substitute the current third startup mode into the full-unit multi-machine frequency response model for simulation to obtain the current second frequency security index;

[0027] Step S206: Determine whether the current second frequency security index meets the first preset condition;

[0028] If so, and the change amount of the current expected value of the first asynchronous power supply carrying capacity is less than or equal to at this time, then use the current expected value of the first asynchronous power supply carrying capacity as the asynchronous power supply carrying capacity under the pre-fault of the power system;

[0029] If not, and the current expected value of the first asynchronous power supply carrying capacity is greater than or equal to 200 MW, then perform the next step S207;

[0030] Step S207: Use the third minimum equivalent inertia constant as the third objective function, and the constraint conditions of the third objective function include the lower limit of the second equivalent inertia constant of the started units and the lower limit of the sum of the second mechanical power increments of the started units;

[0031] Step S208: Determine whether the third objective function has a solution;

[0032] Step S209: If the third objective function has a solution, update the current startup mode to obtain the updated current fourth startup mode, the sum of the fourth mechanical powers of the currently started units, and the fourth equivalent inertia constant of the currently started units;

[0033] Update the current third startup mode according to the current fourth startup mode;

[0034] Update the lower limit of the second equivalent inertia constant and the lower limit of the sum of the second mechanical power increments according to the sum of the fourth mechanical powers of the currently started units and the fourth equivalent inertia constant of the currently started units, and return to step 205;

[0035] If the third objective function has no solution, after adding 1 to the number of iterations, return to step S201.

[0036] Optionally, the power system frequency response data includes: the rotational kinetic energy of all startable units, governor-prime mover parameters, maximum active power; the equivalent damping coefficient and total load power of the power system.

[0037] Optionally, between step S102 and step S103, it further includes:

[0038] Simulate the full-unit multi-machine frequency response model to obtain the mechanical power increments of each unit at the moment corresponding to the frequency extreme value.

[0039] Optionally, when initially optimizing the asynchronous power supply carrying capacity in the full-unit multi-machine frequency response model, the constraint conditions to be satisfied include the following: active power balance constraint, system equivalent inertia constant constraint, unit output limit constraint, unit primary frequency regulation reserve constraint, fault reserve constraint, maximum frequency change rate constraint.

[0040] Optionally, the constraint conditions of the first objective function or the third objective function further include the following: active power balance constraint, unit output limit constraint, maximum frequency change rate constraint, unit primary frequency regulation reserve constraint, fault reserve constraint.

[0041] Optionally, the judgment result of step S105 further includes:

[0042] If not, and when the current expected value of the first asynchronous power supply carrying capacity is less than 200 MW, then set the 200 MW as the maximum accuracy value of the current power system asynchronous power supply carrying capacity, and end the evaluation.

[0043] Optionally, the judgment result of step S206 further includes:

[0044] If so, and when the change amount of the current expected value of the first asynchronous power supply carrying capacity is greater than halve the change amount of the current expected value of the first asynchronous power supply carrying capacity, and reset the system frequency extreme value deviation at the current iteration to the corresponding value of the previous secant method iteration, and execute step S202.

[0045] Optionally, the judgment result of step S206 further includes:

[0046] If not, and when the current expected value of the first asynchronous power supply carrying capacity is less than 200 MW, then set the 200 MW as the maximum accuracy value of the current power system asynchronous power supply carrying capacity, and end the evaluation.

[0047] This application has the following beneficial effects:

[0048] In the method provided in the embodiment of the present application, startup optimization and frequency safety simulation are considered, and frequency safety indicators can be obtained more accurately. Compared with the method of optimizing startup by increasing the equivalent inertia constant of the system, the method considers the indicators representing the change of frequency extreme values, can stably reduce the frequency extreme values, has better startup optimization effect and faster evaluation speed. The above method for determining the asynchronous power supply carrying capacity considering frequency safety constraints has higher efficiency and accuracy.

[0049] In addition to the purposes, features and advantages described above, the present application has other purposes, features and advantages. The following will refer to the accompanying drawings to make a more detailed description of the present application. Description of the Drawings

[0050] The accompanying drawings constituting a part of the present application are used to provide a further understanding of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation to the present application. In the drawings:

[0051] Figure 1 is a schematic flow chart of a method for evaluating the asynchronous power supply carrying capacity provided by an embodiment of the present application;

[0052] Figure 2 is a schematic diagram of a full-unit multi-machine frequency response model provided by an embodiment of the present application;

[0053] Figure 3 is a schematic diagram of the verification result of the accuracy of the multi-machine frequency response model provided by an embodiment of the present application; Figure 3 (a) is a schematic diagram of the verification result of the accuracy when the load shedding is 1200 MW, Figure 3 (b) is a schematic diagram of the verification result of the accuracy when the load shedding is 1751 MW, Figure 3 (c) is a schematic diagram of the verification result of the accuracy when a 250 MW unit is removed, Figure 3 (d) is a schematic diagram of the verification result of the accuracy when the DC bipolar blocking causes an active power deficit of 1720 MW;

[0054] Figure 4 is a schematic diagram of the verification result of the sum of the lower limit of the equivalent inertia constant and the lower limit of the first mechanical power increment of the startup units provided by an embodiment of the present application; Detailed Embodiments

[0055] The following will make a detailed description of the embodiments of the present application in conjunction with the accompanying drawings. However, the present application can be implemented in many different ways defined and covered by the claims.

[0056] It should be noted that the variable prefixes such as "first" and "second" added to some formulas in this article (such as the lower limit of the first equivalent inertia constant and the lower limit of the second equivalent inertia constant) are essentially used to distinguish similar objects and are not used to describe a specific order or sequence. This naming difference is only to enable readers to quickly correspond to the application scenarios of the "old strategy - new strategy". In fact, the physical meanings of the two variables in the formula are exactly the same (both represent the dynamic support ability of the power supply for asynchronous loads), and the calculation logic (such as the transient stability equation based on the phasor method) and boundary conditions are also exactly the same. Therefore, in the actual formula, no modification is made to them.

[0057] The carrying capacity of asynchronous power supplies (such as power supplies connected through power electronic interfaces like photovoltaic, wind power, and energy storage) refers to the maximum capacity of asynchronous power supplies that the power grid can accommodate under the premise of ensuring safe and stable operation. Its magnitude affects the frequency stability of the power system when certain faults occur in the power system. Therefore, the importance of confirming the carrying capacity limit of asynchronous power supplies is self-evident. However, in the existing technologies, when confirming the carrying capacity limit of asynchronous power supplies, the time-domain simulation method is mostly used to obtain high-precision frequency safety indicators, but its solution time is too long; or the equivalent model method is used. Since the nonlinear links in the synchronous machine frequency response model are not considered and simplified models are often used, the solution time is short, but the accuracy of the obtained frequency safety indicators is low. In addition, many studies are based on the original startup mode, and the carrying capacity of asynchronous power supplies is evaluated by replacing synchronous machines with asynchronous power supplies. In actual operation, unstarted units can be considered to optimize the startup mode to obtain the optimal solution.

[0058] Therefore, to avoid the above problems, as Figure 1 shown, this application proposes a method for determining the carrying capacity of asynchronous power supplies, including:

[0059] Step S101: Obtain the power system frequency response data;

[0060] Based on the power system frequency response data, construct a full-unit multi-machine frequency response model;

[0061] Among them, the power system frequency response data includes: the rotational kinetic energy of all startable units, governor-prime mover parameters, maximum active power; the equivalent damping coefficient of the power system and the total load power.

[0062] The full-unit multi-machine frequency response model includes synchronous power supplies and asynchronous power supplies. The specific structure of the full-unit multi-stage frequency response model is as Figure 2As shown in the figure, only a common governor-prime mover model is shown. In the figure, 'GI', 'GJ', 'GA', 'GM' are electronic governor models, 'GS', 'GW' are hydraulic governor models, and 'TA', 'TB', 'TC', 'TW', 'TV' are prime mover models; K is the reference conversion coefficient, that is, the ratio of the generator reference capacity to the system reference capacity; a to i represent the number of each type of unit; H is the system equivalent inertia constant; D is the system equivalent damping coefficient; is the active power disturbance.

[0063] The multi-machine frequency response model of the whole unit retains the frequency regulation characteristics of each unit, as well as non-linear links such as the frequency regulation dead zone, the upper and lower limits of the speed deviation, the amplification factor of the speed deviation, various time constants inside the system, and power limiting, so it can maintain high-precision results.

[0064] In addition, after determining the multi-machine frequency response model of the whole unit, under the condition that the output of all units is not limited, the model is simulated and tested to obtain the mechanical power increment of each unit at the moment corresponding to the extreme frequency value , and sort them in descending order to quantify the magnitude in descending order The magnitude of each unit The quantification value can be expressed by the following formula:

[0065] (1)

[0066] In the formula, is the quantification value of the mechanical power increment of the th unit; is the test value of the mechanical power increment of the th unit.

[0067] Step S102: Initially optimize the asynchronous power supply carrying capacity in the multi-machine frequency response model of the whole unit to obtain the expected value of the maximum asynchronous power supply carrying capacity, the current first starting mode, the sum of the first mechanical powers of the currently started units, and the first equivalent inertia constant of the currently started units;

[0068] According to the sum of the first mechanical powers of the currently started units and the first equivalent inertia constant of the currently started units, determine the lower limit of the first equivalent inertia constant of the currently started units and the lower limit of the sum of the first mechanical power increments of the currently started units;

[0069] After the initial optimization, obtain the current first starting mode and the expected value of the maximum asynchronous power supply carrying capacity, that is, taking the maximum asynchronous power feeding power (i.e., the asynchronous power supply carrying capacity) as the objective function:

[0070] (2)

[0071] When solving this objective function, the objective function needs to satisfy the following constraints:

[0072] 1) Active power balance constraint

[0073] Active power balance means that at any moment, the sum of the active power generated by all generators in the power system and the DC input power must be equal to the sum of the active power consumed by all loads and transmission lines. During the process of optimizing the unit startup mode, the active power balance constraint can be regarded as the sum of the active power of the generators after optimization plus the power fed in by the asynchronous power sources being equal to the sum of the active power of the generators before optimization, that is:

[0074] (3)

[0075] 2) System equivalent inertia constant constraint

[0076] The system equivalent inertia constant is expressed by Equation (6) and should be less than or equal to the system equivalent inertia constant when all units are started up :

[0077] (4)

[0078] (5)

[0079] (6)

[0080] (7)

[0081] In the formula, is the unit startup mode matrix, is the startup state of the th generator, which is a binary variable, 0 means the unit is shut down, and 1 means the unit is started up; is the generator rotational kinetic energy matrix, is the rotational kinetic energy of the th generator; is the equivalent inertia constant of the system startup units; is the system base capacity.

[0082] 3) Rate of change of frequency , which refers to the rate of change of the system frequency and is determined by the unbalanced power and the system inertia. Its value is usually the largest at the moment when the disturbance starts. Currently, there is no unified constraint standard for the rate of change of frequency in power grid operation. A large It may trigger the pole-slip phenomenon of synchronous units, causing structural damage. The operation of gas units is greatly affected by the rate of frequency change. Distributed generation uses the rate of frequency change as the basis for island detection, and the existing wind power and photovoltaic converter controls also have corresponding constraint settings for the rate of frequency change. From the perspective of power grid operation, the high proportion of new energy access to the system will inevitably lead to scenarios with large rates of frequency change in the power grid operation. For example, in some areas, the power grid requires that the system can withstand a rate of frequency change of 1 Hz / s under large disturbances. With the increase in the new energy penetration rate, this tolerance value will even be increased to 2 Hz / s in the future. Therefore, the rate of frequency change will become an important constraint index for a high-proportion new energy power system, and its constraint can be expressed as:

[0083] (8)

[0084] (9)

[0085] (10)

[0086] In the formula, is the maximum rate of frequency change at the initial moment of the disturbance, which can be expressed by formula (10); is the limit value of the maximum rate of frequency change; is the rate of frequency change at 200 ms; is the limit value of the rate of frequency change at 200 ms. Formula (8) is the constraint of the maximum rate of frequency change, and formula (9) is the rate of frequency change at 200 ms.

[0087] 4) Constraint on the output limit of the unit

[0088] The constraint on the output limit of the unit means that the active power generated by the unit is not less than its minimum stable output and not greater than its maximum active power:

[0089] (11)

[0090] In the formula, are the minimum stable output and the maximum active power of the unit respectively.

[0091] 5) Constraint on the primary frequency regulation reserve of the unit

[0092] According to the power grid operation criterion, it is set that the primary frequency regulation reserve capacity of the generator set is not less than 6% of the rated capacity of the unit:

[0093] (12)

[0094] 6) Constraint on the fault reserve

[0095] The primary frequency regulation reserve capacity of the system should not be less than the active power disturbance amount:

[0096] (13)

[0097] Wherein, is the active power disturbance of the system.

[0098] When all the above-mentioned constraint conditions except formula (9) are satisfied, the objective function is solved to obtain the expected value of the maximum asynchronous power source carrying capacity , as well as the current first starting mode corresponding to the expected value of the maximum asynchronous power source carrying capacity, the first equivalent inertia constant of the currently started units, and the sum of the first mechanical powers of the currently started units.

[0099] Since in this application, it is necessary to calculate the equivalent inertia constant and the sum of the first mechanical powers of the currently started units many times, therefore, the derivation and calculation process thereof will be described in detail herein:

[0100] When only considering the inertia response and primary frequency modulation measures of synchronous generator units, the system frequency response can be obtained from the rotor motion equation of the equivalent generator set:

[0101] (14)

[0102] Wherein, is the system frequency; is the mechanical power increment of the generator; is the active power disturbance of the system; is the system equivalent inertia constant; is the system equivalent damping coefficient. Generally, it is considered that the system equivalent damping coefficient is a fixed value and does not change with the starting mode, and it can be considered that has no influence on the change of the frequency extreme deviation. Based on this, in order to derive the index characterizing the change of the frequency extreme deviation, the equivalent rotor motion equation can be rewritten as the following formula:

[0103] (15)

[0104] Integrating both sides of formula (16) gives:

[0105] (16)

[0106] Let , then its derivative is:

[0107] (17)

[0108] Before the frequency drops to the lowest point, the frequency decreases monotonically, then is always less than 0, formula (18) is always greater than 0, then It always holds. Before the frequency drops to the lowest point, the mechanical power generated by the generator continuously increases, that is is monotonically increasing. And and are both normal constants and , then is monotonically decreasing.

[0109] In summary, before the frequency drops to the lowest point, the larger is, the smaller is, and the larger is. Therefore, as long as the startup is optimized by controlling to continuously decrease, the frequency extreme value can be stably increased. Based on this, at the moment corresponding to the frequency extreme value, assuming is a variable that changes with the startup method, as shown in equations (18 - 22):

[0110] (18)

[0111] (19)

[0112] (20)

[0113] (21)

[0114] (22)

[0115] In the equations, is the startup method matrix, is the startup state of the th generator, which is a binary variable, 0 means shutdown, 1 means startup; is the matrix of the mechanical power increment of the generator at the moment corresponding to the frequency extreme value, is the mechanical power increment of the th generator at the moment corresponding to the frequency extreme value; is the matrix of the rotational kinetic energy of the generator, is the rotational kinetic energy of the th generator; is the sum of the mechanical power increments of the startup units; is the equivalent inertia constant of the system startup units; is the system base capacity.

[0116] From equation (21), it is not difficult to see that after each update of the current startup method, according to the current startup method and the mechanical power increments of each unit, the sum of the mechanical powers of the startup units of the current power system can be obtained.

[0117] For easy understanding, Regarded as , then Suppose , when, equation (23) always holds,

[0118] (23)

[0119] (24)

[0120] Expand the brackets of equation (24) and transpose the terms, it can be deduced that:

[0121] (25)

[0122] Obviously, the left side of equation (25) is always less than 0, which is contradictory. By reductio ad absurdum, equation (26) always holds:

[0123] (26)

[0124] It is easy to know by analysis that when, equation (26) still always holds.

[0125] In summary, , and when, equation (26) always holds, indicating that ensuring the equivalent inertia constant of the generating units at system startup increases continuously, and the sum of the mechanical power increments of the generating units at system startup does not decrease, then will continue to decrease, thus continuously increasing the frequency extreme value, that is can characterize the change of the frequency extreme value deviation. For the convenience of description, hereinafter is used to replace to characterize the change of the frequency extreme value deviation, that is, the proposed index is .

[0126] According to equation (1), can be expressed by the following formula:

[0127] (27)

[0128] In the formula, is the startup state of the th generating unit, 0 means shutdown, and 1 means startup. When all generating units are fully started,

[0129] (28)

[0130] When some generating units are started, , which conforms to the characteristics.

[0131] According to the above derivation process, it can be clearly seen that every time after updating the current startup mode, the sum of the corresponding equivalent inertia constant of the current startup unit and the first mechanical power of the current startup unit will also change accordingly, thus having a certain impact on the current power system frequency difference.

[0132] Since in the follow-up of this application, it is necessary to continuously optimize the inertia, the specific process of optimizing the inertia is as follows:

[0133] Taking the minimum equivalent inertia constant as the objective function:

[0134] (29)

[0135] The constraint conditions of this objective function are as follows:

[0136] (30)

[0137] (31)

[0138] In the formula, is the lower limit of the equivalent inertia constant for inertia optimization, is the equivalent inertia constant of the current startup unit, is the upper limit of the equivalent inertia constant for inertia optimization, is the sum of the first mechanical powers, is the lower limit of the sum of the mechanical power increments of the startup units, and its value is equal to the sum of the mechanical powers corresponding to the startup mode obtained from the previous inertia optimization.

[0139] In addition to formulas (30) and (31), the above objective function also includes the constraint conditions of formulas (3)-(6), (8), (10)-(13). That is to say, only when the constraint conditions corresponding to formulas (3)-(6), (8), (10)-(13), and formulas (30) and (31) are simultaneously satisfied can the above objective function be solved to obtain the corresponding results.

[0140] Here, when performing the initial optimization, it is necessary to determine the lower limit value of the equivalent inertia constant and the lower limit of the sum of the mechanical power increments of the startup units. Therefore, after the initial optimization is completed, the sum of the first mechanical powers of the current startup units is directly used as the lower limit of the first power sum of the current startup units, and the first equivalent inertia constant of the current startup units is used as the lower limit of the first equivalent inertia constant of the current startup units. After the first determination, the specific process of updating the above two values is as follows:

[0141] (32)

[0142] In the formula; is the equivalent inertia constant increment. During the evaluation process, multiple inertia optimizations are required. In order to reduce the number of iterations, It is determined by the method of "variable step length + fixed step length", that is:

[0143] ① When larger,

[0144] (33)

[0145] In the formula, The value should be set to a larger value to quickly increase the frequency extreme deviation and reduce the number of iterations.

[0146] ② When smaller,

[0147] (34)

[0148] In the formula, is a constant value and should be set to a smaller value to reduce the probability of missing the optimal solution. However, in order to reduce the number of iterations, it is better to set .

[0149] It can be seen that when a new round of solving the objective function is performed, the lower limit value of the equivalent inertia constant in the constraint condition is determined based on the sum of the equivalent inertia constant corresponding to the previous startup mode and the equivalent inertia constant increment.

[0150] The update method is as follows:

[0151] As shown in the following formula, The number of iterations for the current inertia optimization. hour, The value is the corresponding boot mode obtained by initial optimization .in other words, Its value is equal to the sum of the first mechanical powers corresponding to the start-up mode obtained by the last inertia optimization. In other words, the constraint condition of formula (31) is that the sum of the first mechanical powers corresponding to the current start-up mode is compared with the sum of the first mechanical powers corresponding to the previous start-up mode, and the sum of the first mechanical powers corresponding to the current start-up mode must be greater than or equal to the sum of the first mechanical powers corresponding to the previous start-up mode.

[0152] .

[0153] It should be noted that when solving the objective function later, the constraint conditions (30) and (31) mentioned above have the same optimization process as here, so they will not be described in detail later.

[0154] Step S103: setting expected faults;

[0155] In power system stability analysis and control strategy design (such as optimizing the carrying capacity of asynchronous power sources), a contingency refers to a predefined typical fault scenario that may trigger system disturbances, used to simulate the system response under extreme conditions and verify the effectiveness of control strategies.

[0156] Step S104: Substitute the current first starting mode into the full-unit multi-machine frequency response model for simulation to obtain the current first frequency security index.

[0157] After setting the contingency, substitute the above first starting mode into the previously obtained full-unit multi-frequency response model for simulation, so as to obtain the first frequency security index, and the first frequency security index includes the frequency extreme deviation and the frequency change rate at 200 ms. . The frequency extreme deviation refers to the difference between the minimum value reached by the system frequency during the frequency drop process and the frequency reference value after the system has an active power deficit. The low inertia characteristics of a high-proportion new energy power system will lead to a large frequency drop amplitude. Once the frequency touches the starting value of the under-frequency load shedding protection , it will trigger a large-scale power outage of the system.

[0158] Step S105: Determine whether the first frequency security index meets the first preset condition;

[0159] If so, take the maximum expected value of the carrying capacity of asynchronous power sources as the carrying capacity of asynchronous power sources under the contingency of the power system;

[0160] If not, and the current first expected value of the carrying capacity of asynchronous power sources is not less than 200 MW, then execute the next step S105;

[0161] After obtaining the first frequency security index, check this first frequency security index, that is, determine whether it meets the first preset condition, and the first preset condition is that the constraint conditions of formula (9) and (36) need to be met simultaneously. The frequency extreme deviation needs to meet the following constraint conditions:

[0162] (36)

[0163] The specific results of the judgment are divided into the following three types:

[0164] 1. If the constraint conditions of formula (9) and (36) hold simultaneously, then the maximum expected value of the carrying capacity of asynchronous power sources corresponding to the first starting mode is taken as the carrying capacity of asynchronous power sources under the contingency of this system.

[0165] 2. If the constraint conditions of formulas (9) and (36) do not hold simultaneously, and the expected value of the first asynchronous power - carrying capacity corresponding to the currently updated second startup mode is less than 200 MW, then set 200 MW as the maximum accuracy value of the asynchronous power - carrying capacity of the current power system, end the determination, and consider that the asynchronous power - carrying capacity under this contingency fault is zero. That is to say, if at this time it is simply confirmed that the expected value of the asynchronous power - carrying capacity under this contingency fault is δ MW, then its specific accurate value should be δ MW to δ + 200 MW.

[0166] 3. If the constraint conditions of formulas (9) and (36) do not hold simultaneously, and the expected value of the first asynchronous power - carrying capacity corresponding to the currently updated first startup mode is greater than or equal to 200 MW, then perform the next step S106.

[0167] Step S106: Take the first minimum equivalent inertia constant as the first objective function. The constraint conditions of the first objective function include the lower limit of the first equivalent inertia constant of the currently - operating units and the lower limit of the sum of the first mechanical power increments of the currently - operating units.

[0168] At this time, take the first minimum inertia constant as the first objective function, as shown in formula (29). Its corresponding constraint conditions include formulas (30) and (31), as well as the constraint conditions of formulas (3)-(6), (8), (10)-(13). Since the above has detailed the objective function and each formula here, no further elaboration will be made here.

[0169] Step S107: Determine whether the first objective function has a solution.

[0170] After establishing the objective function, it is necessary to determine whether the objective function has a solution, and based on the specific conditions after the determination, determine the subsequent processing operations.

[0171] Step S108: If the first objective function has a solution, then update the current startup mode to obtain the current second startup mode, the sum of the second mechanical powers of the currently - operating units, and the second equivalent inertia constant of the currently - operating units.

[0172] Update the current first startup mode according to the current second startup mode.

[0173] Update the lower limit of the first equivalent inertia constant and the lower limit of the sum of the first mechanical power increments according to the sum of the second mechanical powers of the currently - operating units and the second equivalent inertia constant of the currently - operating units, and return to step S104.

[0174] On the basis of satisfying the constraint conditions, solve the first objective function. If the first objective function has a solution, update the current starting method to obtain the current second starting method. After obtaining the current second starting method, the sum of the second mechanical powers of the currently started units and the second equivalent inertia constant of the currently started units corresponding to the current second starting method can be calculated according to formulas (21) and (22).

[0175] After obtaining the current second starting method, it can be updated as the current first starting method. Since iterative calculations are still required, the sum of the second mechanical powers of the currently started units is substituted into formula (35) as the lower limit of the sum of the mechanical power increments of the starting units in the constraint conditions when the objective function is solved next time. The equivalent inertia constant of the current second starting units is substituted into formula (32) as the lower limit of the equivalent inertia constant in the constraint conditions when the objective function is solved next time.

[0176] After the above operations are completed, since the expected value of the maximum non-synchronous power supply carrying capacity has been determined, there is no need to perform operations such as optimization. It is directly returned to step 104, and the updated current first starting method is substituted into the full-unit frequency response model again for simulation calculation, and then continue to judge and perform subsequent operations.

[0177] The above method can effectively improve the frequency extreme value and verify the frequency safety index. If the frequency indexes obtained by simulating all starting methods corresponding to the current expected value of the non-synchronous power supply carrying capacity do not meet the frequency safety constraints, it is necessary to reduce the expected value of the non-synchronous power supply carrying capacity and re-optimize and evaluate until it is satisfied.

[0178] That is to say, if the first objective function has no solution, other methods can be used to obtain the expected value of the non-synchronous power supply carrying capacity under the assumed fault. This application also proposes other methods to obtain the expected value of the non-synchronous power supply carrying capacity.

[0179] Step S201: Update the current first expected value of the non-synchronous power supply carrying capacity and the change amount of the current first expected value of the non-synchronous power supply carrying capacity based on the secant method;

[0180] First of all, based on the secant method, the expected value of the non-synchronous power supply carrying capacity is updated to obtain the current first expected value of the non-synchronous power supply carrying capacity and the change amount of the current first expected value of the non-synchronous power supply carrying capacity. It should be noted that the non-synchronous power supply carrying capacity can be equivalent to the non-synchronous power supply limit feeding power. Therefore, the expected value of the non-synchronous power supply carrying capacity is the feeding power of a certain non-synchronous power supply. The following details this process:

[0181] The asynchronous power feed-in essentially replaces the synchronous units. In a certain starting mode, when shutting down units to increase the asynchronous power feed-in, the system frequency support ability weakens. Under the same disturbance, the extreme value of the system frequency will decrease. Similarly, when the asynchronous power feed-in decreases, the extreme value of the system frequency will increase. Regarding the asynchronous power feed-in as a function of the deviation of the extreme frequency value, it is shown as follows:

[0182] (37)

[0183] In the formula, is the asynchronous power feed-in, is the maximum frequency extreme value deviation obtained by simulation.

[0184] Then this function is a monotonically decreasing function, and the secant method can be used to iteratively approximate the optimal solution. Assuming it is a monotonically decreasing linear function, the secant equation can be written as:

[0185] (38)

[0186] In the formula, is the asynchronous power feed-in during the th iteration of the secant method; is the system frequency extreme value deviation during the th iteration of the secant method, is the asynchronous power feed-in during the th iteration of the secant method; is the system frequency extreme value deviation during the th iteration of the secant method. Since the final product obtained by simulation is the maximum frequency extreme value deviation corresponding to the current expected value of the asynchronous power carrying capacity, then should be the maximum frequency extreme value deviation obtained by simulation. That is to say, the above steps are iteratively optimized multiple times, and each optimization can obtain a frequency extreme value deviation. Select a maximum frequency extreme value deviation from them and substitute it into the above formula (38) for calculation.

[0187] Let in formula (38), and obtain:

[0188] (39)

[0189] (40)

[0190] In the formula, is the minimum frequency extreme value deviation, that is, the lower limit of the frequency extreme value constraint. According to the iterative equations of formulas (39)-(40), continuously iterate to reduce the expected value of the asynchronous power carrying capacity, and combine the above steps S101-S108 for frequency verification, then the asynchronous power carrying capacity of the system can be accurately evaluated.

[0191] Let be the number of iterations of the secant method. If , then set the initial reduction amount of the expected value of the asynchronous power carrying capacity to . Then, in the active power balance constraint of the initial inertia optimization model ; if , then reduce the expected value of the asynchronous power carrying capacity according to Eqs. (39)-(40) to obtain the updated current first expected value of the asynchronous power carrying capacity and the change amount of the current first expected value of the asynchronous power carrying capacity.

[0192] It should be noted that in the initial iteration, the reduction amount of the initial expected value of the asynchronous power carrying capacity can be set by oneself, but generally the range should not be too large.

[0193] Step S202: Use the second smallest equivalent inertia constant as the second objective function. The constraint conditions of the second objective function are the same as those for initially optimizing the asynchronous power carrying capacity in the multi-machine frequency response model of the entire unit; after obtaining the updated current second expected value of the asynchronous power carrying capacity and the change amount of the current first expected value of the asynchronous power carrying capacity, simple initialization needs to be performed again. Specifically as follows:

[0194] At this time, use the second smallest inertia constant as the second objective function, as shown in Eq. (29), and its corresponding constraint conditions include the constraint conditions of (3)-(8), (10)-(13). Since the above has elaborated on the objective function and each formula here in detail, therefore, no more detailed description will be given here.

[0195] Step S203: Determine whether the second objective function has a solution;

[0196] After establishing the objective function, it is necessary to determine whether the objective function has a solution, and determine the subsequent processing operations according to the specific conditions after the judgment.

[0197] Step S204: If the second objective function has a solution, obtain the current third unit starting mode, the sum of the third mechanical powers of the currently operating units, and the third equivalent inertia constant of the currently operating units;

[0198] If the second objective function has a solution, obtain the current third unit starting mode, the sum of the third mechanical powers of the currently operating units, and the third equivalent inertia constant of the currently operating units;

[0199] According to the sum of the third mechanical powers of the currently operating units and the third equivalent inertia constant of the currently operating units, determine the lower limit of the second equivalent inertia constant of the currently operating units and the lower limit of the sum of the second mechanical power increments of the currently operating units, and execute the next step S205;

[0200] If the second objective function has no solution, after adding 1 to the iteration count, return to step S201.

[0201] At this time, on the basis of satisfying the constraint conditions, solve the second objective function. If the second objective function has a solution, update the current startup method to obtain the current third startup method, and then the sum of the third mechanical powers of the currently started units and the third equivalent inertia constant of the currently started units corresponding to the current second startup method can be calculated according to formulas (21) and (22).

[0202] After obtaining the current third startup method, since iterative calculations may still be required, substitute the sum of the third mechanical powers of the currently started units into formula (35) as the lower limit of the sum of the mechanical power increments of the second startup units in the constraint conditions when the objective function is solved subsequently, and substitute the current third equivalent inertia constant of the startup units into formula (32) as the lower limit of the second equivalent inertia constant in the constraint conditions when the objective function is solved subsequently.

[0203] After updating the constraint conditions of the second objective function, directly proceed to the next step S205;

[0204] If the second objective function has no solution, add 1 to the current iteration count and return to step S201.

[0205] Step S205: Substitute the current third startup method into the full-unit multi-machine frequency response model for simulation to obtain the current second frequency security index;

[0206] After obtaining the updated current third startup method, it is necessary to judge the frequency security of the full-unit multi-machine frequency response model under this third startup method. Then substitute the current third startup method into the full-unit multi-machine frequency response model for simulation to obtain the current second frequency security index, and the second frequency security index includes the frequency extreme deviation and the frequency change rate at 200 ms .

[0207] Step S206: Judge whether the current second frequency security index meets the first preset condition;

[0208] If so, and the change amount of the current expected value of the first asynchronous power supply carrying capacity is less than or equal to then take the current expected value of the first asynchronous power supply carrying capacity as the asynchronous power supply carrying capacity under the pre-fault condition of the power system;

[0209] If not, and the current expected value of the first asynchronous power supply carrying capacity is greater than or equal to 200 MW, then execute the next step S207;

[0210] Here, after obtaining the second frequency safety index, the second frequency safety index is checked, that is, it is judged whether it meets the first preset condition. The first preset condition is that the constraint conditions of formula (9) and (36) need to be met simultaneously. The judgment results are specifically divided into the following four types:

[0211] If the constraint conditions of formula (9) and (36) hold simultaneously, and the current change amount of the expected value of the first asynchronous power supply carrying capacity is less than or equal to At this time, the current expected value of the first asynchronous power supply carrying capacity is used as the asynchronous power supply carrying capacity of the system under this contingency.

[0212] If the constraint conditions of formula (9) and (36) hold simultaneously, and the current change amount of the expected value of the first asynchronous power supply carrying capacity is greater than It indicates that the reduction amount of the current expected value of the first asynchronous power supply carrying capacity is too large. At this time, the change amount of the current expected value of the first asynchronous power supply carrying capacity is halved, and the extreme deviation of the system frequency at the current iteration is set to the corresponding value of the previous secant method iteration, and step S202 is executed. This is because the relationship between the power fed into the asynchronous power supply and the extreme deviation of the frequency is not a linear function, which may be too large, resulting in being much higher than , thus causing the evaluation result to be on the small side. For this case, this application will halve it, and reset the remaining parameters (the extreme deviation of the system frequency) to the corresponding value of the th secant method iteration, and perform iterative calculation again. This method effectively prevents the problem that it may be too large.

[0213] 3. If the constraint conditions of formula (9) and (36) do not hold simultaneously, and the current expected value of the first asynchronous power supply carrying capacity is less than 200 MW, then 200 MW is set as the maximum accuracy value of the asynchronous power supply carrying capacity of the current power system, and the determination ends, and it is considered that the asynchronous power supply carrying capacity under this contingency is zero. That is to say, if the expected value of the asynchronous power supply carrying capacity under this contingency is simply confirmed as δ MW at this time, then its specific accurate value should be δ MW to δ + 200 MW.

[0214] 4. If the constraint conditions of formula (9) and (36) do not hold simultaneously, and the current expected value of the first asynchronous power supply carrying capacity is greater than or equal to 200 MW, then step S207 is executed at this time.

[0215] Step S207: Use the third minimum equivalent inertia constant as the third objective function, and the constraint conditions of the third objective function include the lower limit of the second equivalent inertia constant of the on - line units and the lower limit of the sum of the second mechanical power increments of the on - line units;

[0216] At this time, the third smallest inertia constant is used as the second objective function, as shown in Equation (29). Its corresponding constraint conditions include Equations (30) and (31), as well as the constraint conditions of Formulas (3)-(6), (8), (10)-(13). Since the above has elaborated on the objective function and each formula here, no further explanation will be given here.

[0217] It should be noted that when establishing the objective function here, since the initial optimization was carried out in Step S204 to obtain the lower limit of the second equivalent inertia constant of the on-line units and the lower limit of the sum of the second mechanical power increments of the on-line units. Therefore, when directly using them as the lower limit of the second equivalent inertia constant and the lower limit of the sum of the second mechanical power increments of the on-line units in the constraint conditions during the first solution of the third objective function.

[0218] Step S208: Determine whether the third objective function has a solution;

[0219] After establishing the objective function, it is necessary to determine whether the objective function has a solution, and based on the specific conditions after the determination, to determine the subsequent processing operations.

[0220] Step S209: If the third objective function has a solution, update the current on-line mode to obtain the updated current fourth on-line mode, the sum of the fourth mechanical powers of the current on-line units, and the fourth equivalent inertia constant of the current on-line units;

[0221] Update the current third on-line mode according to the current fourth on-line mode;

[0222] Update the lower limit of the second equivalent inertia constant and the lower limit of the sum of the second mechanical power increments according to the sum of the fourth mechanical powers of the current on-line units and the fourth equivalent inertia constant of the current on-line units, and return to Step 205;

[0223] If the third objective function has no solution, after adding 1 to the iteration count, return to Step S201.

[0224] At this time, on the basis of satisfying the constraint conditions, solve the third objective function. If the third objective function has a solution, update the current on-line mode to obtain the current fourth on-line mode. Then, according to Formulas (21) and (22), the sum of the fourth mechanical powers of the current on-line units and the fourth equivalent inertia constant corresponding to the current fourth on-line mode can be calculated.

[0225] After obtaining the current fourth starting mode, update the current third starting mode according to it. Since iterative calculations may still be required, substitute the sum of the mechanical powers of the current fourth starting units into formula (35) as the lower limit of the sum of the mechanical power increments of the second starting units in the constraint conditions when the objective function is solved subsequently. Substitute the equivalent inertia constant of the current fourth starting units into formula (32) as the lower limit of the second equivalent inertia constant in the constraint conditions when the objective function is solved subsequently.

[0226] That is to say, subsequently, update the lower limit of the sum of the mechanical power increments and the lower limit of the equivalent inertia constant of the constraint conditions of the objective function for the next iterative calculation through the sum of the mechanical powers of the current fourth starting units and the equivalent inertia constant of the current fourth starting units corresponding to the current fourth starting mode.

[0227] If there is no solution to the third objective function when solving it at this time, then increment the iteration count by 1 and return to step S201 to perform iterative calculations again.

[0228] Experimental verification

[0229] In the embodiment of the present application, a full-unit multi-machine frequency response model is built in MATLAB / Simulink for simulation verification. The verification results of the accuracy of the full-unit multi-machine frequency response model are as Figure 3 shown in (a)- Figure 3 shown in (d). In the legend, DSP refers to the simulation result of the DSP software, and ML refers to the simulation result of the multi-machine frequency response model. The verification results of the proposed inertia optimization index, the lower limit of the equivalent inertia constant, and the lower limit of the sum of the mechanical power increments of the starting units are as Figure 4 shown.

[0230] From Figure 3 shown in (a)- Figure 3 shown in (d), it can be seen that whether it is the high-frequency response of load shedding or the low-frequency response of generator tripping and DC blocking, the frequency response curve of the multi-machine frequency response model is always highly fitted with the DSP software, indicating that the multi-machine frequency response model can accurately simulate and obtain the frequency safety index and , thus ensuring the accuracy of the frequency index check and the assessment of the non-synchronous power supply carrying capacity.

[0231] From Figure 4 it can be seen that as continually decreases, the frequency extreme value deviation steadily increases, verifying the nature of the proposed index.

[0232] In a possible implementation manner, denoted as implementation manner 1, consider the inertia optimization of optimizing the starting by increasing the system equivalent inertia constant;

[0233] According to the embodiments and implementation manners 1 of the present application, the asynchronous power supply carrying capacity determination results are shown in Table 1.

[0234] Table 1 Determination results of the asynchronous power supply limit penetration rate

[0235] ,

[0236] It can be seen that by using the iterative evaluation method for the asynchronous power supply carrying capacity based on frequency constraint and secant method provided in this embodiment, the asynchronous power supply carrying capacity can be obtained quickly and accurately.

[0237] In summary, the method proposed in the embodiments of the present application takes into account the startup optimization and frequency safety simulation, and can obtain the frequency safety index more accurately; compared with the method of optimizing the startup by increasing the system equivalent inertia constant, it takes into account the index characterizing the change of the frequency extreme value, can stably reduce the frequency extreme value, has a better startup optimization effect and a faster evaluation speed. The above method for determining the asynchronous power supply carrying capacity considering the frequency safety constraint has higher efficiency and accuracy.

[0238] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, the present application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A method for evaluating the carrying capacity of an asynchronous power supply, characterized in that: include: Step S101: Acquire power system frequency response data; Based on the power system frequency response data, construct a frequency response model of all units and multiple machines; Step S102: Initially optimize the asynchronous power supply carrying capacity in the multi-machine frequency response model of the whole unit to obtain the expected value of the maximum asynchronous power supply carrying capacity and the sum of the current first startup mode, the first equivalent inertia constant of the current startup unit and the first mechanical power of the current startup unit; Determine the lower limit of the first equivalent inertia constant of the currently powered-on unit and the lower limit of the sum of the first mechanical power increment of the currently powered-on unit according to the sum of the first equivalent inertia constant of the currently powered-on unit and the first mechanical power of the currently powered-on unit; Step S103: setting expected faults; Step S104, substituting the current first startup mode into the multi-machine frequency response model of the whole unit to perform simulation to obtain the current first frequency safety index; Step S105: determining whether the current first frequency safety index meets a first preset condition; If yes, then the expected value of the maximum asynchronous power supply carrying capacity is used as the asynchronous power supply carrying capacity under the expected fault of the power system; If not, and the expected value of the current maximum asynchronous power source carrying capacity is greater than or equal to 200MW, the next step S106 is executed; Step S106: taking the first minimum equivalent inertia constant as the first objective function, wherein the first objective function constraint condition includes the lower limit of the first equivalent inertia constant of the currently powered-on unit and the lower limit of the sum of the first mechanical power increment of the currently powered-on unit; Step S107: Determine whether the first objective function has a solution; Step S108: If the first objective function has a solution, the current startup mode is updated to obtain the current second startup mode, the sum of the second mechanical power of the currently started unit, and the second equivalent inertia constant of the currently started unit; According to the current second startup mode, updating the current first startup mode; According to the sum of the second mechanical power of the currently powered-on unit and the second equivalent inertia constant of the currently powered-on unit, the lower limit of the first equivalent inertia constant and the lower limit of the sum of the first mechanical power increment are updated, and the process returns to step S104.

2. The method according to claim 1, characterized in that: When the judgment result of step S107 is that there is no solution, the following steps are performed: Step S201: Based on the secant method, update the expected value of the current first asynchronous power supply carrying capacity and the change in the expected value of the current first asynchronous power supply carrying capacity; Step S202: taking the second minimum equivalent inertia constant as the second objective function, wherein the constraint condition of the second objective function is the same as the constraint condition for initially optimizing the non-synchronous power supply carrying capacity in the multi-machine frequency response model of the whole unit; Step S203: Determine whether the second objective function has a solution; Step S204: if the second objective function has a solution, the current startup mode is updated to obtain the current third startup mode, the sum of the third mechanical power of the current startup unit, and the third equivalent inertia constant of the current startup unit; According to the sum of the third mechanical power of the currently powered-on unit and the third equivalent inertia constant of the currently powered-on unit, determine the lower limit of the second equivalent inertia constant of the currently powered-on unit and the lower limit of the sum of the second mechanical power increment of the currently powered-on unit, and execute the next step S205; If the second objective function has no solution, the number of iterations is increased by 1, and the process returns to step S201; Step S205: Substituting the current third startup mode into the multi-machine frequency response model of the whole unit to perform simulation to obtain the current second frequency safety index; Step S206: Determine whether the current second frequency safety index meets a first preset condition; If yes, and the expected value change of the current first asynchronous power supply carrying capacity is less than or equal to , then the expected value of the current first asynchronous power supply carrying capacity is used as the asynchronous power supply carrying capacity under the expected fault of the power system; If not, and the expected value of the current first asynchronous power supply carrying capacity is greater than or equal to 200MW, the next step S207 is executed; Step S207: taking the third minimum equivalent inertia constant as the third objective function, wherein the constraint conditions of the third objective function include the lower limit of the second equivalent inertia constant of the startup unit and the lower limit of the sum of the second mechanical power increment of the startup unit; Step S208: Determine whether the third objective function has a solution; Step S209: if the third objective function has a solution, the current startup mode is updated to obtain the updated current fourth startup mode, the sum of the fourth mechanical power of the current startup unit, and the fourth equivalent inertia constant of the current startup unit; According to the current fourth startup mode; updating the current third startup mode; According to the sum of the fourth mechanical power of the currently powered-on units and the fourth equivalent inertia constant of the currently powered-on units, update the lower limit of the second equivalent inertia constant and the lower limit of the sum of the second mechanical power increment, and return to step 205; If the third objective function has no solution, the number of iterations is increased by 1 and the process returns to step S201.

3. The method according to claim 1, characterized in that The power system frequency response data includes: the rotational kinetic energy, governor-prime mover parameters, and maximum active power of all start-up units; and the equivalent damping coefficient and total load power of the power system.

4. The method according to claim 2, characterized in that: The steps S102 and S103 further include: The multi-machine frequency response model of the whole unit is simulated to obtain the mechanical power increment of each unit at the time corresponding to the frequency extreme value.

5. The method according to claim 1, characterized in that When the non-synchronous power supply carrying capacity in the multi-machine frequency response model of the whole unit is initially optimized, the constraints that need to be met include the following: active power balance constraint, system equivalent inertia constant constraint, unit output limit constraint, unit primary frequency regulation standby constraint, fault standby constraint, and maximum frequency change rate constraint.

6. The method according to claim 4, characterized in that The first objective function constraint condition or the third objective function constraint condition also includes the following: active power balance constraint, unit output limit constraint, maximum frequency change rate constraint, unit primary frequency regulation standby constraint, and fault standby constraint.

7. The method according to claim 1, characterized in that The judgment result of step S105 also includes: If not, and the expected value of the current first asynchronous power source carrying capacity is less than 200MW, the 200MW is set as the maximum accuracy of the current power system asynchronous power source carrying capacity, and the evaluation is terminated.

8. The method according to claim 2, characterized in that: The judgment result of step S206 also includes: If so, and the expected value change of the current first asynchronous power supply carrying capacity is greater than When the expected value change of the current first asynchronous power supply carrying capacity is halved, the system frequency extreme value deviation at the current iteration is reset to the corresponding value of the previous secant method iteration, and step S202 is executed.

9. The method according to claim 2, characterized in that: The judgment result of step S206 also includes: If not, and the expected value of the current first asynchronous power source carrying capacity is less than 200MW, 200MW is set as the maximum accuracy of the current power system asynchronous power source carrying capacity, and the evaluation is terminated.

Images