A method and system for determining the frequency stability of a system

Abstract

The present invention discloses a method and system for determining the frequency stability of a system, including: determining the unbalanced power based on the operating data of the generator sets in the system; determining the type of disturbance based on the unbalanced power and a preset power start threshold; when the type of disturbance is a step disturbance, respectively determining the maximum disturbance power that the system can withstand under the steady-state frequency deviation constraint, the transient frequency deviation constraint, and the generator primary frequency regulation amplitude limit constraint; and determining the stability of the system based on the maximum disturbance power and the unbalanced power. The present invention can accurately discriminate the type of disturbance, and when the type of disturbance is a step disturbance, based on the maximum disturbance power and the unbalanced power under different constraints, it discriminates the stability of the system, achieving accurate discrimination of the system stability; at the same time, the present invention can also calculate the disturbance power during over-limit when the type of disturbance is a second-level ramp disturbance and a minute-level ramp disturbance, based on the frequency over-limit time and the disturbance power change rate.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and more particularly, to a method and system for determining the frequency stability of a system. Background Art

[0002] In the context of global resource constraints and the urgent need to address carbon emissions, building a new power system with an increasing proportion of new energy is an important means to achieve the carbon neutrality goal.

[0003] In a high-proportion power electronic system, the large-scale access of new energy and high-capacity DC transmission will replace some synchronous units, posing a serious challenge to the frequency stability of the power system. The switching frequency of power electronic devices is much higher than the operating frequency of 50 Hz of the traditional power grid, and it has characteristics such as low inertia, scarce active frequency modulation resources, and insufficient dispatchability. Compared with the traditional synchronous machine system, the frequency indexes of the high-proportion power electronic system will tend to deteriorate after being disturbed.

[0004] In addition to the profound changes on the power supply side, with the increase in the scale of the power system, disturbances also have the characteristics of increasing intensity and gradually diversified disturbance forms. At present, frequency prevention and control mainly targets step disturbances caused by faults such as DC blocking and generator tripping. The method is to predict the frequency response after the disturbance and check whether the frequency exceeds the limit. If it exceeds the limit, the three defense lines are activated to take control measures. In addition to step disturbances, time-varying ramp disturbances have occurred in several power outage accidents at home and abroad in recent years, causing the system frequency to continuously decline until it exceeds the limit, and the existing control means can no longer meet the requirements of frequency stability control.

[0005] Therefore, it is necessary to study the characteristics of frequency response under different disturbances and design a method that can quickly determine the stability of the system. Summary of the Invention

[0006] The present invention proposes a method and system for determining the frequency stability of a system to solve the problem of how to efficiently determine the stable state of the system.

[0007] To solve the above problems, according to one aspect of the present invention, a method for determining the frequency stability of a system is provided. The method includes:

[0008] Determining the unbalanced power based on the operation data of the generating units in the system;

[0009] Determining the disturbance type based on the unbalanced power and a preset power start threshold;

[0010] When the disturbance type is a step disturbance, respectively determining the maximum disturbance power that the system can withstand under the steady-state frequency deviation constraint, the transient frequency deviation constraint, and the generator primary frequency modulation amplitude limit constraint;

[0011] Determine the stability of the system based on the maximum disturbance power and the unbalanced power.

[0012] Preferably, determining the unbalanced power based on the operating data of the generator sets in the system includes:

[0013] ,

[0014] where, is the unbalanced power; E i is the terminal voltage of the i-th generator; U p is the voltage at the disturbance point; is the power angle difference between the i-th generator and the disturbance point; B ip is the conductance between the i-th generator and the disturbance point; is the change in the power angle difference between the i-th generator and the disturbance point; n is the number of generators.

[0015] Preferably, determining the disturbance type based on the unbalanced power and the preset power start threshold includes:

[0016] If > and is a fixed value, determine that the disturbance type is a step disturbance;

[0017] If > and is not a fixed value, determine that the disturbance type is a second-level ramp disturbance;

[0018] If < and > , determine that the disturbance type is a minute-level ramp disturbance;

[0019] where, is the unbalanced power; is the preset power start threshold, , k1 is the maximum power change rate of the minute-level ramp disturbance, T is the power distribution time; is the total frequency deviation generated by the system during primary frequency modulation limiting; , , is the steady-state frequency deviation brought by the generator participating in primary frequency modulation; is the dead-band frequency of the generator's primary frequency modulation; is the measured frequency deviation value at the current moment; h is the ratio of the generator's primary frequency modulation capacity to the generator's on-line capacity; K G is the generator's unit regulation power; P GN is the generator's on-line capacity.

[0020] Preferably, when the perturbation type is a step perturbation, the maximum perturbation power that the system can withstand under the steady-state frequency deviation constraint, transient frequency deviation constraint, and primary frequency regulation amplitude constraint of the generator is determined respectively, including:

[0021] The maximum perturbation power that the system can withstand under the steady-state frequency deviation constraint is determined by the following method, including:

[0022] ,

[0023] The maximum perturbation power that the system can withstand under the transient frequency deviation constraint is determined by the following method, including:

[0024] ,

[0025] The maximum perturbation power that the system can withstand under the primary frequency regulation amplitude constraint of the generator is determined by the following method, including:

[0026] ,

[0027] ,

[0028] ,

[0029] ,

[0030] Wherein, is the maximum perturbation power that the system can withstand under the steady-state frequency deviation constraint; is the load unit regulation power; P L0 is the load level before perturbation; is the steady-state frequency constraint value; f N is the frequency base value; K G is the generator unit regulation power, P GN is the generator on-line capacity; is the maximum perturbation power that the system can withstand under the transient frequency deviation constraint; m is the ratio of the primary frequency regulation capacity of the generator to the generator on-line capacity; is the maximum perturbation power that the system can withstand under the primary frequency regulation amplitude constraint of the generator; is the given maximum frequency deviation constraint; R is the governor speed regulation gain after the units are equivalent; is the system base capacity; is the damping ratio; is the natural oscillation angular frequency; α, is the intermediate variable; t m is the time when the maximum value of the system frequency deviation appears; R, H, T R and FH They are the governor speed regulation gain, inertia time constant, reheater time constant, and high-pressure cylinder power ratio after the unit is equivalent, respectively.

[0031] Preferably, determining the stability of the system based on the maximum disturbance power and unbalanced power includes:

[0032] If > min{ , , }, it is determined that the system stability is unstable, and the magnitude of the disturbance power is ;

[0033] If ≤ min{ , , }, it is determined that the system stability is stable;

[0034] Wherein, is the unbalanced power; is the maximum disturbance power that the system can withstand under the steady-state frequency deviation constraint; is the maximum disturbance power that the system can withstand under the transient frequency deviation constraint; is the maximum disturbance power that the system can withstand under the primary frequency regulation amplitude limit constraint of the generator.

[0035] Preferably, the method further includes:

[0036] When the disturbance type is a second-level ramp disturbance, it is determined that the system stability is unstable;

[0037] Determining the first disturbance power change rate, determining the first frequency over-limit time based on the first disturbance power change rate and a preset frequency deviation constraint value, and determining the first over-limit disturbance power based on the first over-limit time and the first disturbance power change rate, includes:

[0038] Using the following formula to determine the first disturbance power change rate, includes:

[0039] ,

[0040] Using the following formula to solve the first frequency over-limit time, includes:

[0041] ,

[0042] ,

[0043] ,

[0044] ,

[0045] ,

[0046] Determine the first over-limit disturbance power using the following formula, including:

[0047] 1 = k m ×t m1 ,

[0048] where k m is the first disturbance power change rate; E i is the terminal voltage of the i-th generator; U p is the disturbance point voltage; is the power angle difference between the i-th generator and the disturbance point; B ip is the conductance between the i-th generator and the disturbance point; is the change in the power angle difference between the i-th generator and the disturbance point; n is the number of generators; t is the sampling time; is the maximum value of the frequency deviation; is the load unit regulation power; R and T R are the governor speed regulation gain and the reheater time constant after the unit equivalence respectively; T1, T2, k1 and k2 are all intermediate variables; t m1 is the first frequency over-limit time; is the damping ratio; is the natural oscillation angular frequency; 1 is the first over-limit disturbance power.

[0049] Preferably, the method further includes:

[0050] When the disturbance type is a minute-level ramp disturbance, determine that the system stability is unstable;

[0051] Determine the second disturbance power change rate, determine the second frequency over-limit time based on the second disturbance power change rate and a preset frequency deviation constraint value, and determine the second over-limit disturbance power based on the second over-limit time and the second disturbance power change rate, including:

[0052] Determine the second disturbance power change rate using the following formula, including:

[0053] ,

[0054] Solve for the second frequency over-limit time using the following formula, including:

[0055] ,

[0056] Determine the second over-limit disturbance power using the following formula, including:

[0057] =k f ×t m2 ,

[0058] where k f is the second perturbation power change rate; is the primary frequency regulation capacity of the load; h is the ratio of the primary frequency regulation capacity of the generator to the generator's on-line capacity; P GN is the generator's on-line capacity; t1 is the moment when the primary frequency regulation capacity of the generator is just completely exhausted; is the maximum frequency deviation; is the frequency startup threshold; is the load unit regulation power; T J is the inertia time constant of the generator set; t m2 is the second frequency over-limit time; is the second over-limit perturbation power.

[0059] According to another aspect of the present invention, there is provided a system for determining the frequency stability of a system, the system comprising:

[0060] An unbalanced power determination unit for determining unbalanced power based on the operation data of the generator sets in the system;

[0061] A perturbation type determination unit for determining the perturbation type based on the unbalanced power and a preset power startup threshold;

[0062] A maximum perturbation power determination unit for, when the perturbation type is a step perturbation, respectively determining the maximum perturbation power that the system can withstand under steady-state frequency deviation constraints, transient frequency deviation constraints, and generator primary frequency regulation amplitude constraints;

[0063] A stability determination unit for determining the stability of the system based on the maximum perturbation power and the unbalanced power.

[0064] Preferably, the unbalanced power determination unit determines the unbalanced power based on the operation data of the generator sets in the system, including:

[0065] ,

[0066] where, is the unbalanced power; E i is the terminal voltage of the i-th generator; U p is the voltage at the perturbation point; is the power angle difference between the i-th generator and the perturbation point; B ip is the conductance between the i-th generator and the perturbation point; is the change in the power angle difference between the i-th generator and the perturbation point; n is the number of generators.

[0067] Preferably, the disturbance type determination unit determines the disturbance type based on the unbalanced power and a preset power start threshold, including:

[0068] If it satisfies > and is a fixed value, then determine that the disturbance type is a step disturbance;

[0069] If it satisfies > and is not a fixed value, then determine that the disturbance type is a second-level ramp disturbance;

[0070] If it satisfies < and > , then determine that the disturbance type is a minute-level ramp disturbance;

[0071] Wherein, is the unbalanced power; is the preset power start threshold, , k1 is the maximum power change rate of the minute-level ramp disturbance, and T is the power distribution time; is the total frequency deviation generated by the system during primary frequency modulation limiting, , , is the steady-state frequency deviation brought by the generator participating in primary frequency modulation, is the dead-band frequency of the generator's primary frequency modulation; is the measured frequency deviation value at the current moment; h is the ratio of the generator's primary frequency modulation capacity to the generator's on-line capacity; K G is the unit regulation power of the generator; P GN is the generator's on-line capacity.

[0072] Preferably, the maximum disturbance power determination unit, when the disturbance type is a step disturbance, determines the maximum disturbance power that the system can withstand under steady-state frequency deviation constraints, transient frequency deviation constraints, and generator primary frequency modulation limiting constraints, including:

[0073] Determine the maximum disturbance power that the system can withstand under steady-state frequency deviation constraints by using the following method, including:

[0074] ,

[0075] Determine the maximum disturbance power that the system can withstand under transient frequency deviation constraints by using the following method, including:

[0076] ,

[0077] Determine the maximum disturbance power that the system can withstand under the primary frequency regulation amplitude constraint of the generator by the following method, including:

[0078] ,

[0079] ,

[0080] ,

[0081] ,

[0082] wherein, is the maximum disturbance power that the system can withstand under the steady-state frequency deviation constraint; is the load unit regulation power; P L0 is the load level before the disturbance; is the steady-state frequency constraint value; f N is the frequency base value; K G is the generator unit regulation power, P GN is the generator on-line capacity; is the maximum disturbance power that the system can withstand under the transient frequency deviation constraint; m is the ratio of the primary frequency regulation capacity of the generator to the generator on-line capacity; is the maximum disturbance power that the system can withstand under the primary frequency regulation amplitude constraint of the generator; is the given maximum frequency deviation constraint; R is the governor speed regulation gain after the units are equivalent; is the system base capacity; is the damping ratio; is the natural oscillation angular frequency; α, is an intermediate variable; t m is the time when the maximum value of the system frequency deviation appears; R, H, T R and F H are respectively the governor speed regulation gain, the inertia time constant, the reheater time constant and the high-pressure cylinder power ratio after the units are equivalent.

[0083] Preferably, the stability determination unit determines the stability of the system based on the maximum disturbance power and the unbalanced power, including:

[0084] If > min{ , , }, it is determined that the system stability is unstable, and the magnitude of the disturbance power is ;

[0085] If ≤ min{ , , }, the system stability is determined to be stable;

[0086] Among them, is the unbalanced power; is the maximum disturbance power that the system can withstand under the steady-state frequency deviation constraint; is the maximum disturbance power that the system can withstand under the transient frequency deviation constraint; is the maximum disturbance power that the system can withstand under the primary frequency regulation amplitude constraint of the generator.

[0087] Preferably, the system further includes: a first over-limit disturbance power determination unit, configured to:

[0088] When the disturbance type is a second-level ramp disturbance, determine that the system stability is unstable;

[0089] Determine the first disturbance power change rate, determine the first frequency over-limit time based on the first disturbance power change rate and a preset frequency deviation constraint value, and determine the first over-limit disturbance power based on the first over-limit time and the first disturbance power change rate, including:

[0090] Use the following formula to determine the first disturbance power change rate, including:

[0091] ,

[0092] Use the following formula to solve for the first frequency over-limit time, including:

[0093] ,

[0094] ,

[0095] ,

[0096] ,

[0097] ,

[0098] Use the following formula to determine the first over-limit disturbance power, including:

[0099] 1=k m ×t m1 ,

[0100] Among them, k m is the first disturbance power change rate; E i is the terminal voltage of the i-th generator; U p is the disturbance point voltage; is the power angle difference between the i-th generator and the disturbance point; B ip is the conductance between the i-th generator and the disturbance point; is the change in the power angle difference between the i-th generator and the disturbance point; n is the number of generators; t is the sampling time; is the maximum value of the frequency deviation; is the load unit regulation power; R and T R are the governor speed regulation gain and the reheater time constant after the unit is equivalent, respectively; T1, T2, k1, and k2 are all intermediate variables; t m1 is the first frequency over-limit time; is the damping ratio; is the natural oscillation angular frequency; 1 is the first over-limit disturbance power.

[0101] Preferably, the system further includes: a first over-limit disturbance power determination unit, configured to:

[0102] When the disturbance type is a minute-level ramp disturbance, determine that the system stability is unstable;

[0103] Determine the second disturbance power change rate, determine the second frequency over-limit time based on the second disturbance power change rate and a preset frequency deviation constraint value, and determine the second over-limit disturbance power based on the second over-limit time and the second disturbance power change rate, including:

[0104] Use the following formula to determine the second disturbance power change rate, including:

[0105] ,

[0106] Use the following formula to solve for the second frequency over-limit time, including:

[0107] ,

[0108] Use the following formula to determine the second over-limit disturbance power, including:

[0109] =k f ×t m2 ,

[0110] where k f is the second disturbance power change rate; is the load primary frequency regulation capacity; h is the ratio of the generator primary frequency regulation capacity to the generator on-line capacity; P GN is the generator on-line capacity; t1 is the moment when the generator primary frequency regulation capacity is just completely exhausted; is the maximum value of the frequency deviation; is the frequency start threshold; is the power adjusted by the load unit; T J is the inertia time constant of the generator set; t m2 is the second frequency over-limit time; is the second over-limit disturbance power.

[0111] Based on another aspect of the present invention, the present invention provides a computer-readable storage medium, on which a computer program is stored, and when the program is executed by a processor, it implements the steps of any one of the methods for determining the frequency stability of a system.

[0112] Based on another aspect of the present invention, the present invention provides an electronic device, including:

[0113] the above-mentioned computer-readable storage medium; and

[0114] one or more processors for executing the program in the computer-readable storage medium.

[0115] The present invention provides a method and a system for determining the frequency stability of a system, including: determining the unbalanced power based on the operation data of the generator sets in the system; determining the disturbance type based on the unbalanced power and a preset power start threshold; when the disturbance type is a step disturbance, respectively determining the maximum disturbance power that the system can withstand under the steady-state frequency deviation constraint, the transient frequency deviation constraint, and the generator primary frequency regulation amplitude constraint; determining the stability of the system based on the maximum disturbance power and the unbalanced power. The present invention can accurately discriminate the disturbance type, and when the disturbance type is a step disturbance, based on the maximum disturbance power and the unbalanced power under different constraints, it discriminates the system stability, realizing the accurate discrimination of the system stability; at the same time, the present invention can also calculate the disturbance power during over-limit based on the frequency over-limit time and the disturbance power change rate when the disturbance type is a second-level ramp disturbance and a minute-level ramp disturbance. The present invention can intuitively display the frequency safety and stability margin of the system, providing a theoretical basis for taking frequency safety control measures. BRIEF DESCRIPTION OF THE DRAWINGS

[0116] By referring to the following drawings, the exemplary embodiments of the present invention can be more completely understood:

[0117] Figure 1 is a flowchart of a method 100 for determining the frequency stability of a system according to an embodiment of the present invention;

[0118] Figure 2 is a schematic diagram of the frequency deviation when the primary frequency regulation capacity of the generator is exhausted according to an embodiment of the present invention;

[0119] Figure 3 is a schematic structural diagram of a system 300 for determining the frequency stability of a system according to an embodiment of the present invention. Detailed Implementation Modes

[0120] Now, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to disclose the present invention in detail and completely, and to fully convey the scope of the present invention to those skilled in the art. The terms in the exemplary embodiments shown in the drawings are not limitations on the present invention. In the drawings, the same units / components are denoted by the same reference numerals.

[0121] Unless otherwise specified, the terms used herein (including scientific and technical terms) have the ordinary meaning understood by those skilled in the art. Additionally, it can be understood that the terms defined in a commonly used dictionary should be construed to have a meaning consistent with the context of their relevant fields, and should not be construed as having an idealized or overly formal meaning.

[0122] Figure 1 is a flowchart of a method 100 for determining the frequency stability of a system according to an embodiment of the present invention. As Figure 1 shown, the method for determining the frequency stability of a system provided by the embodiments of the present invention can accurately distinguish the type of disturbance, and when the type of disturbance is a step disturbance, it can determine the system stability based on the maximum disturbance power and unbalanced power under different constraints, realizing the accurate determination of system stability; at the same time, the present invention can also calculate the disturbance power during frequency limit when the type of disturbance is a second-level ramp disturbance and a minute-level ramp disturbance based on the frequency limit time and the change rate of disturbance power. The present invention can intuitively display the frequency safety and stability margin of the system, providing a theoretical basis for taking frequency safety control measures. The method 100 for determining the frequency stability of a system provided by the embodiments of the present invention starts from step 101, and determines the unbalanced power based on the operation data of the generating units in the system at step 101.

[0123] Preferably, the determining the unbalanced power based on the operation data of the generating units in the system includes:

[0124] ,

[0125] where, is the unbalanced power; E i is the terminal voltage of the i-th generator; U p is the voltage at the disturbance point; is the power angle difference between the i-th generator and the disturbance point; B ip is the conductance between the i-th generator and the disturbance point; is the change amount of the power angle difference between the i-th generator and the disturbance point; n is the number of generators.

[0126] In the present invention, given a fault scenario, based on measurement data, the unbalanced power is calculated, and the current disturbance form is judged based on the unbalanced power. Specifically, it includes:

[0127] (1) Set the power and frequency startup thresholds. Calculate the maximum disturbance power that a minute-level ramp disturbance can generate within the unbalanced power distribution time, and use this value as the power startup threshold. Assume that the maximum power change rate of the minute-level ramp disturbance is k 1, within the power distribution time T The maximum disturbance power that can be generated is k 1 T Therefore, the power startup threshold is:

[0128] ,

[0129] The frequency startup threshold is taken as the frequency deviation generated when the primary frequency regulation capacity of the generator is exactly exhausted. The frequency deviation when the primary frequency regulation capacity of the generator is exhausted is as Figure 2 shown. When the generator reaches the primary frequency regulation limit, the frequency deviation generated after the generator frequency regulation process starts and the total frequency deviation generated by the system are:

[0130] ,

[0131] ,

[0132] In the formula, f d is the dead-band frequency of the generator's primary frequency regulation, and its typical value for thermal power units is 0.033Hz. is the steady-state frequency deviation brought about after the generator participates in primary frequency regulation. The sum of the two is the total frequency deviation generated by the system when reaching the primary frequency regulation limit , K G is the unit regulation power of the generator. P GN is the generator's on-line capacity. h is the ratio of the generator's primary frequency regulation capacity to the generator's on-line capacity.

[0133] (2) Utilize the response characteristics of the first stage after the disturbance, and calculate the total unbalanced power of the system according to the change in electromagnetic power of each unit. Assume that at p a power disturbance occurs, and the unbalanced power is jointly borne by the electromagnetic powers of each generator within the region:

[0134] ,

[0135] After linearizing the change in electromagnetic power of each generator, the expression is:

[0136] ,

[0137] In the formula, E i , E j is the generator terminal voltage, U p is the voltage at the disturbance point, is the power angle difference between generators, is the power angle difference between the generator and the disturbance point, is the conductance between generators, is the conductance between the generator and the disturbance point; is the change in the power angle difference between the ith generator and the disturbance point.

[0138] Since each generator remains synchronized at the initial stage of the disturbance, there is = 0. Therefore, the unbalanced power calculation formula is:

[0139] ,

[0140] where, is the unbalanced power; E i is the terminal voltage of the ith generator; U p is the voltage at the disturbance point; is the power angle difference between the ith generator and the disturbance point; B ip is the conductance between the ith generator and the disturbance point; is the change in the power angle difference between the ith generator and the disturbance point; n is the number of generators.

[0141] In step 102, determine the disturbance type based on the unbalanced power and a preset power start threshold.

[0142] Preferably, the determining the disturbance type based on the unbalanced power and a preset power start threshold includes:

[0143] If > and is a constant value, determine that the disturbance type is a step disturbance;

[0144] If > and is not a constant value, determine that the disturbance type is a second-level ramp disturbance;

[0145] If < and > , determine that the disturbance type is a minute-level ramp disturbance;

[0146] wherein, is the unbalanced power; is the preset power start threshold, , k1 is the maximum power change rate of the minute-level ramp disturbance, and T is the power distribution time; is the total frequency deviation generated by the system during the primary frequency regulation amplitude limit, , , is the steady-state frequency deviation brought about after the generator participates in the primary frequency regulation, is the dead-band frequency of the generator's primary frequency regulation; is the measured frequency deviation value at the current moment; h is the ratio of the generator's primary frequency regulation capacity to the generator's on-line capacity; K G is the unit regulation power of the generator; P GN is the generator's on-line capacity.

[0147] In step 103, when the disturbance type is a step disturbance, the maximum disturbance power that the system can withstand under the steady-state frequency deviation constraint, the transient frequency deviation constraint, and the generator primary frequency regulation amplitude limit constraint is determined respectively.

[0148] Preferably, when the disturbance type is a step disturbance, the maximum disturbance power that the system can withstand under the steady-state frequency deviation constraint, the transient frequency deviation constraint, and the generator primary frequency regulation amplitude limit constraint is determined respectively, including:

[0149] Determining the maximum disturbance power that the system can withstand under the steady-state frequency deviation constraint by using the following method, including:

[0150] ,

[0151] Determining the maximum disturbance power that the system can withstand under the transient frequency deviation constraint by using the following method, including:

[0152] ,

[0153] Determining the maximum disturbance power that the system can withstand under the generator primary frequency regulation amplitude limit constraint by using the following method, including:

[0154] ,

[0155] ,

[0156] ,

[0157] ,

[0158] wherein, is the maximum disturbance power that the system can withstand under the steady-state frequency deviation constraint; is the power regulation per unit of load; P L0 is the load level before the disturbance; is the steady-state frequency constraint value; f N is the frequency base value; K G is the power regulation per unit of generator, P GN is the installed capacity of the generator; is the maximum disturbance power that the system can withstand under the transient frequency deviation constraint; m is the ratio of the primary frequency regulation capacity of the generator to the installed capacity of the generator; is the maximum disturbance power that the system can withstand under the primary frequency regulation amplitude constraint of the generator; is the given maximum frequency deviation constraint; R is the governor speed regulation gain after the unit equivalence; is the system base capacity; is the damping ratio; is the natural oscillation angular frequency; α, is an intermediate variable; t m is the time when the maximum value of the system frequency deviation appears; R, H, T R and F H are respectively the governor speed regulation gain, the inertia time constant, the reheater time constant and the high-pressure cylinder power ratio after the unit equivalence.

[0159] In step 104, the stability of the system is determined based on the maximum disturbance power and the unbalanced power.

[0160] Preferably, the determining the stability of the system based on the maximum disturbance power and the unbalanced power includes:

[0161] If > min{ , , }, then it is determined that the system stability is unstable, and the magnitude of the disturbance power is ;

[0162] If ≤ min{ , , }, then it is determined that the system stability is stable;

[0163] Wherein, is the unbalanced power; is the maximum disturbance power that the system can withstand under the steady-state frequency deviation constraint; is the maximum disturbance power that the system can withstand under the transient frequency deviation constraint; is the maximum disturbance power that the system can withstand under the primary frequency regulation amplitude constraint of the generator.

[0164] In the present invention, when > and is a fixed value, it is determined that a step disturbance occurs, and the magnitude of the step disturbance at this time is the magnitude of the unbalanced power; when > and is not a fixed value, it is determined that a second-level ramp disturbance occurs; when < and > it is determined that a minute-level ramp disturbance occurs; where is the unbalanced power; is the preset power start threshold, , k1 is the maximum power change rate of the minute-level ramp disturbance, and T is the power distribution time; is the total frequency deviation generated by the system during primary frequency modulation limiting, , , is the steady-state frequency deviation brought by the generator participating in primary frequency modulation, is the dead-band frequency of the generator's primary frequency modulation; is the measured frequency deviation value at the current moment; h is the ratio of the generator's primary frequency modulation capacity to the generator's on-line capacity; K G is the unit regulation power of the generator; P GN is the generator's on-line capacity.

[0165] In the present invention, when a step disturbance occurs, the maximum disturbance power that the system can withstand is obtained respectively through the steady-state frequency deviation constraint, the transient frequency deviation constraint, and the generator primary frequency modulation limiting constraint, and the smaller value of the three is taken as the maximum disturbance power that the system can withstand under the step disturbance . Compare the magnitude of the current disturbance and to determine whether the system is unstable, which mainly includes:

[0166] (1) Calculation of the maximum disturbance power that the system can withstand under the steady-state frequency deviation constraint. When the frequency reaches the steady-state value, the unbalanced power is equal to the load regulation power plus the generator regulation power:

[0167] ,

[0168] In the formula, P L0 is the load level before the disturbance, is the critical value of the disturbance power under the steady-state frequency deviation constraint, is the steady-state frequency constraint value, f N is the frequency base value, taken as 50Hz.

[0169] (2) Consider the calculation of the maximum disturbance power that the system can withstand under the constraint of the primary frequency regulation amplitude limit of the generator. After the frequency regulation capacity of the conventional unit reaches the amplitude limit, the remaining unbalanced power is all borne by the load frequency regulation. According to the power balance, there is:

[0170] ,

[0171] (3) Consider the calculation of the maximum disturbance power that the system can withstand under the constraint of the transient frequency deviation. According to the frequency response model, the maximum value and the occurrence time of the system frequency deviation can be obtained as:

[0172] ,

[0173] ,

[0174] In the formula, , .

[0175] Given the maximum frequency deviation constraint , the maximum disturbance power that the system can withstand under the transient frequency constraint can be obtained:

[0176] ,

[0177] (4) Take = min{ , , } as the maximum unbalanced power that the system can withstand under the step disturbance. If > , the system will become unstable; otherwise, the system is stable.

[0178] Preferably, the method further includes:

[0179] When the disturbance type is a second-level ramp disturbance, determine that the system stability is unstable;

[0180] Determine the first disturbance power change rate, determine the first frequency over-limit time based on the first disturbance power change rate and the preset frequency deviation constraint value, and determine the first over-limit disturbance power based on the first over-limit time and the first disturbance power change rate, including:

[0181] Use the following formula to determine the first disturbance power change rate, including:

[0182] ,

[0183] Use the following formula to solve the first frequency over-limit time, including:

[0184] ,

[0185] ,

[0186] ,

[0187] ,

[0188] ,

[0189] The first out-of-limit disturbance power is determined using the following formula, including:

[0190] =k m ×t m1 ,

[0191] where k m is the first disturbance power change rate; E i is the terminal voltage of the i-th generator; U p is the disturbance point voltage; is the power angle difference between the i-th generator and the disturbance point; B ip is the conductance between the i-th generator and the disturbance point; is the change in the power angle difference between the i-th generator and the disturbance point; n is the number of generators; t is the sampling time; is the maximum frequency deviation; is the load unit regulation power; R and T R are the governor speed regulation gain and the reheater time constant after the unit is equivalent, respectively; T1, T2, k1, and k2 are all intermediate variables; t m1 is the first frequency out-of-limit time; is the damping ratio; is the natural oscillation angular frequency; is the first out-of-limit disturbance power.

[0192] Preferably, the method further includes:

[0193] When the disturbance type is a minute-level ramp disturbance, it is determined that the system stability is unstable;

[0194] Determine the second disturbance power change rate, determine the second frequency out-of-limit time based on the second disturbance power change rate and a preset frequency deviation constraint value, and determine the second out-of-limit disturbance power based on the second out-of-limit time and the second disturbance power change rate, including:

[0195] The second disturbance power change rate is determined using the following formula, including:

[0196] ,

[0197] The second frequency out-of-limit time is solved using the following formula, including:

[0198] ,

[0199] The second over-limit disturbance power is determined using the following formula, including:

[0200] =k f ×t m2 ,

[0201] where k f is the second disturbance power change rate; is the primary frequency regulation capacity of the load; h is the ratio of the primary frequency regulation capacity of the generator to the generator's on-line capacity; P GN is the generator's on-line capacity; t1 is the moment when the primary frequency regulation capacity of the generator is just completely exhausted; is the maximum frequency deviation; is the frequency start threshold; is the load unit regulation power; T J is the inertia time constant of the generator set; t m2 is the second frequency over-limit time; is the second over-limit disturbance power.

[0202] In the present invention, when it is determined that a second-level ramp disturbance has occurred, it can be directly determined that the system is in an unstable state. Let = kt , then the disturbance power change rate is:

[0203] ,

[0204] When a second-level ramp disturbance occurs. According to the second-level ramp disturbance frequency response model and the frequency deviation constraint, the frequency deviation over-limit moment is calculated, and according to the disturbance power magnitude corresponding to the ramp function slope (i.e., the disturbance power change rate) over-limit moment, it mainly includes:

[0205] (1) Obtain the frequency response expression corresponding to the ramp disturbance in the complex frequency domain:

[0206] ,

[0207] In the formula, , .

[0208] (2) Perform the inverse Laplace transform on equation (15) to obtain the frequency response time-domain expression:

[0209] ,

[0210] In the formula, , .

[0211] (3) Suppose that t m1 the frequency deviation constraint value is reached at moment. From the above formula, we can get:

[0212] ,

[0213] The time when the frequency exceeds the limit can be solved by numerical algorithm t m1 . At this time, the magnitude of the disturbance power at the first time when the frequency exceeds the limit is = k m × t m1 ; where k m is the first disturbance power change rate; E i is the terminal voltage of the i-th generator; U p is the voltage at the disturbance point; is the power angle difference between the i-th generator and the disturbance point; B ip is the conductance between the i-th generator and the disturbance point; is the change in the power angle difference between the i-th generator and the disturbance point; n is the number of generators; t is the sampling time; is the maximum frequency deviation; is the load unit regulation power; R and T R are the governor speed regulation gain and the reheater time constant after the unit is equivalent, respectively; T1, T2, k1, and k2 are all intermediate variables; t m1 is the first frequency over-limit time; is the damping ratio; is the natural oscillation angular frequency; is the first over-limit disturbance power.

[0214] In the present invention, when it is determined that a minute-level ramp disturbance occurs, it can be determined that the system is in an unstable state. The frequency change rate of the minute-level ramp disturbance is extremely small. When the frequency deviation starts to reach the threshold, it can be considered that the transient frequency response process caused by the unbalanced power has ended. At this time, the unbalanced power is completely offset by the primary frequency regulation of the generator and the primary frequency regulation of the load. Suppose t 1 is the moment when the frequency deviation reaches the start threshold. At this time, the frequency deviation is, and the load regulation power is:

[0215] ,

[0216] In the formula, K L is the load unit regulation power.

[0217] t At the moment 1, the primary frequency regulation capacity of the generator is just completely exhausted. From the power balance:

[0218] ,

[0219] From the above two formulas, the power change rate of the minute-level ramp disturbance can be obtained. :

[0220] .

[0221] When a minute-level ramp disturbance occurs, the frequency response process after reaching the frequency deviation threshold can be solved at this time, and then the system frequency over-limit time can be obtained. According to the slope of the ramp function (i.e., the disturbance power change rate), the disturbance power magnitude at the over-limit moment can be calculated, mainly including:

[0222] (1) Solve the frequency response expression of the minute-level ramp disturbance after reaching the frequency threshold. The generator rotor motion equation is shown as the following formula:

[0223] ,

[0224] In the formula, T J represents the inertia time constant of the generator set, represents the rotor of the generator set q axis and the included angle between the real axis of the synchronous coordinate, is the change in mechanical power, is the change in electromagnetic power, , represents the angular velocity, is the rated angular velocity.

[0225] When the primary frequency regulation capacity of the generator is exhausted, only the primary frequency regulation of the load compensates for the unbalanced power:

[0226] ,

[0227] Combining the above two formulas, we can get:

[0228] ,

[0229] t The unbalanced power expression after 1 is, = ( t-t 1), solve the differential equation and substitute the initial value conditions. At this time, the generated frequency deviation is , and the frequency response expression is obtained as:

[0230] ,

[0231] (2) Suppose at t m2 the moment reaches the frequency deviation constraint value , from the above formula, we can get:

[0232] ,

[0233] At this time, the time exceeding the frequency limit can be solved by the numerical algorithm. t m2 , so the magnitude of the disturbance power during the over-limit period is 2 = k f ×t m2 ; where k f is the second disturbance power change rate; is the primary frequency regulation capacity of the load; h is the ratio of the primary frequency regulation capacity of the generator to the generator's on-line capacity; P GN is the generator's on-line capacity; t1 is the moment when the primary frequency regulation capacity of the generator is just completely exhausted; is the maximum value of the frequency deviation; is the load unit regulation power; T J is the inertia time constant of the generator set; t m2 is the second frequency over-limit time; is the second over-limit disturbance power.

[0234] Figure 3 is a schematic structural diagram of a system 300 for determining system frequency stability according to an embodiment of the present invention. As Figure 3 shown, the system 300 for determining system frequency stability provided by the embodiment of the present invention includes: an unbalanced power determination unit 301, a disturbance type determination unit 302, a maximum disturbance power determination unit 303, and a stability determination unit 304.

[0235] Preferably, the unbalanced power determination unit 301 is configured to determine unbalanced power based on the operation data of the generator sets in the system.

[0236] Preferably, the unbalanced power determination unit 301 determines unbalanced power based on the operation data of the generator sets in the system, including:

[0237] ,

[0238] where, is the unbalanced power; E i is the terminal voltage of the i-th generator; U p is the voltage at the disturbance point; is the power angle difference between the i-th generator and the disturbance point; B ip is the conductance between the i-th generator and the disturbance point; is the change amount of the power angle difference between the i-th generator and the disturbance point; n is the number of generators.

[0239] Preferably, the disturbance type determination unit 302 is configured to determine the disturbance type based on the unbalanced power and a preset power start threshold.

[0240] Preferably, the disturbance type determination unit 302 determines the disturbance type based on the unbalanced power and a preset power start threshold, including:

[0241] If > and is a fixed value, it is determined that the disturbance type is a step disturbance;

[0242] If > and is not a fixed value, it is determined that the disturbance type is a second-level ramp disturbance;

[0243] If < and > , it is determined that the disturbance type is a minute-level ramp disturbance;

[0244] Wherein, is the unbalanced power; is the preset power start threshold, , k1 is the maximum power change rate of the minute-level ramp disturbance, and T is the power distribution time; is the total frequency deviation generated by the system during primary frequency regulation with amplitude limit, , , is the steady-state frequency deviation brought about after the generator participates in primary frequency regulation, is the dead-band frequency of the generator's primary frequency regulation; is the measured frequency deviation value at the current moment; h is the ratio of the generator's primary frequency regulation capacity to the generator's on-line capacity; K G is the unit regulation power of the generator; P GN is the generator's on-line capacity.

[0245] Preferably, the maximum disturbance power determination unit 303 is configured to, when the disturbance type is a step disturbance, determine the maximum disturbance power that the system can withstand under the steady-state frequency deviation constraint, the transient frequency deviation constraint, and the generator primary frequency regulation amplitude limit constraint, respectively.

[0246] Preferably, the maximum disturbance power determination unit 303, when the disturbance type is a step disturbance, determines the maximum disturbance power that the system can withstand under the steady-state frequency deviation constraint, the transient frequency deviation constraint, and the generator primary frequency regulation amplitude limit constraint, respectively, including:

[0247] The maximum disturbance power that the system can withstand under the steady-state frequency deviation constraint is determined in the following manner, including:

[0248] ,

[0249] The maximum disturbance power that the system can withstand under the transient frequency deviation constraint is determined in the following manner, including:

[0250] ,

[0251] The maximum disturbance power that the system can withstand under the primary frequency regulation amplitude limit constraint of the generator is determined in the following manner, including:

[0252] ,

[0253] ,

[0254] ,

[0255] ,

[0256] Among them, is the maximum disturbance power that the system can withstand under the steady-state frequency deviation constraint; is the load unit regulation power; P L0 is the load level before the disturbance; is the steady-state frequency constraint value; f N is the frequency base value; K G is the generator unit regulation power, P GN is the generator on-line capacity; is the maximum disturbance power that the system can withstand under the transient frequency deviation constraint; m is the ratio of the primary frequency regulation capacity of the generator to the generator on-line capacity; is the maximum disturbance power that the system can withstand under the primary frequency regulation amplitude limit constraint of the generator; is the given maximum frequency deviation constraint; R is the governor speed regulation gain after the unit equivalence; is the system base capacity; is the damping ratio; is the natural oscillation angular frequency; α, is the intermediate variable; t m is the time when the maximum value of the system frequency deviation appears; R, H, T R and F H are the governor speed regulation gain, inertia time constant, reheater time constant and high-pressure cylinder power ratio after the unit equivalence, respectively.

[0257] Preferably, the stability determination unit 304 is configured to determine the stability of the system based on the maximum disturbance power and the unbalanced power.

[0258] Preferably, the stability determination unit 304 determines the stability of the system based on the maximum disturbance power and the unbalanced power, including:

[0259] If > min{ , , }, it is determined that the system stability is unstable, and the magnitude of the disturbance power is ;

[0260] If ≤ min{ , , }, it is determined that the system stability is stable;

[0261] Wherein, is the unbalanced power; is the maximum disturbance power that the system can withstand under the steady-state frequency deviation constraint; is the maximum disturbance power that the system can withstand under the transient frequency deviation constraint; is the maximum disturbance power that the system can withstand under the primary frequency regulation amplitude constraint of the generator.

[0262] Preferably, the system further includes: a first over-limit disturbance power determination unit, configured to:

[0263] When the disturbance type is a second-level ramp disturbance, it is determined that the system stability is unstable;

[0264] Determine the first disturbance power change rate, determine the first frequency over-limit time based on the first disturbance power change rate and a preset frequency deviation constraint value, and determine the first over-limit disturbance power based on the first over-limit time and the first disturbance power change rate, including:

[0265] Use the following formula to determine the first disturbance power change rate, including:

[0266] ,

[0267] Use the following formula to solve for the first frequency over-limit time, including:

[0268] ,

[0269] ,

[0270] ,

[0271] ,

[0272] ,

[0273] The first over-limit disturbance power is determined using the following formula, including:

[0274] 1 = k m × t m1 ,

[0275] where k m is the first disturbance power change rate; E i is the terminal voltage of the i-th generator; U p is the disturbance point voltage; is the power angle difference between the i-th generator and the disturbance point; B ip is the conductance between the i-th generator and the disturbance point; is the change in the power angle difference between the i-th generator and the disturbance point; n is the number of generators; t is the sampling time; is the maximum frequency deviation; is the load unit regulation power; R and T R are the governor speed regulation gain and the reheater time constant after the unit equivalence respectively; T1, T2, k1 and k2 are all intermediate variables; t m1 is the first frequency over-limit time; is the damping ratio; is the natural oscillation angular frequency; 1 is the first over-limit disturbance power.

[0276] Preferably, the system further includes: a first over-limit disturbance power determination unit, configured to:

[0277] When the disturbance type is a minute-level ramp disturbance, determine that the system stability is unstable;

[0278] Determine the second disturbance power change rate, determine the second frequency over-limit time based on the second disturbance power change rate and a preset frequency deviation constraint value, and determine the second over-limit disturbance power based on the second over-limit time and the second disturbance power change rate, including:

[0279] Use the following formula to determine the second disturbance power change rate, including:

[0280] ,

[0281] Use the following formula to solve for the second frequency over-limit time, including:

[0282] ,

[0283] Use the following formula to determine the second over-limit disturbance power, including:

[0284] 2 = kf ×t m2 ,

[0285] where k f is the second disturbance power change rate; L is the primary frequency regulation capacity of the load; h is the ratio of the primary frequency regulation capacity of the generator to the generator's on-line capacity; P GN is the generator's on-line capacity; t1 is the moment when the primary frequency regulation capacity of the generator is just completely exhausted; is the maximum value of the frequency deviation; is the frequency startup threshold; is the load unit regulation power; T J is the inertia time constant of the generator set; t m2 is the second frequency over-limit time; 2 is the second over-limit disturbance power.

[0286] The system 300 for determining the system frequency stability in the embodiment of the present invention corresponds to the method 100 for determining the system frequency stability in another embodiment of the present invention, which will not be elaborated here.

[0287] Based on another aspect of the present invention, the present invention provides a computer-readable storage medium, on which a computer program is stored, and when the program is executed by a processor, it implements the steps of any one of the methods for determining the system frequency stability.

[0288] Based on another aspect of the present invention, the present invention provides an electronic device, including:

[0289] The above-mentioned computer-readable storage medium; and

[0290] One or more processors for executing the program in the computer-readable storage medium.

[0291] The present invention has been described by referring to a few embodiments. However, as is well known to those skilled in the art, as defined by the appended patent claims, other embodiments equivalent to those disclosed above of the present invention equally fall within the scope of the present invention.

[0292] Generally, all terms used in the claims are construed according to their ordinary meanings in the technical field, unless otherwise clearly defined therein. All references to "a / the [device, component, etc.]" are to be construed openly as at least one instance of the device, component, etc., unless otherwise clearly stated. The steps of any method disclosed herein need not be run in the exact order disclosed, unless clearly stated.

[0293] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. 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. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0294] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, and the combination of flows and / or blocks in the flowchart and / or block diagram, can be realized by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the functions specified in Figure 1 one or more of the flows Figure 1 or blocks or the combination of blocks.

[0295] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including instruction means that implement the functions specified in Figure 1 one or more of the flows Figure 1 or blocks or the combination of blocks.

[0296] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in Figure 1 one or more of the flows Figure 1 or blocks or the combination of blocks.

[0297] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: still can modify the specific implementation manners of the present invention or make equivalent replacements, and any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the protection scope of the claims of the present invention.

Claims

1. A method for determining the frequency stability of a system, characterized in that, The method includes: Determining the unbalanced power based on the operating data of the generator sets within the system; Determining the type of disturbance based on the unbalanced power and a preset power start threshold; When the type of disturbance is a step disturbance, respectively determining the maximum disturbance power that the system can withstand under steady-state frequency deviation constraints, transient frequency deviation constraints, and generator primary frequency regulation amplitude constraints; Determining the stability of the system based on the maximum disturbance power and the unbalanced power; Among them, the determining the unbalanced power based on the operating data of the generator sets within the system includes: where, ΔP is the unbalanced power; E i is the terminal voltage of the i-th generator; U p is the voltage at the disturbance point; δ ip is the power angle difference between the i-th generator and the disturbance point; B ip is the conductance between the i-th generator and the disturbance point; Δδ ip is the change in the power angle difference between the i-th generator and the disturbance point; n is the number of generators; Among them, the determining the type of disturbance based on the unbalanced power and a preset power start threshold includes: If ΔP > ΔP is satisfied sh and ΔP is a fixed value, then it is determined that the disturbance type is a step disturbance; If ΔP > ΔP is satisfied sh and ΔP is not a fixed value, then determine that the disturbance type is a second-level ramp disturbance If ΔP < ΔP sh and Δf > Δf sh , then it is determined that the disturbance type is a minute-level ramp disturbance; where ΔP is the unbalanced power; ΔP sh is the preset power start threshold, ΔP sh = k1T, where k1 is the maximum power change rate of the minute-level ramp disturbance and T is the power distribution time; Δf sh is the total frequency deviation generated by the system during the primary frequency modulation limit, Δf sh = Δf G + f d , Δf G is the steady-state frequency deviation brought about after the generator participates in the primary frequency modulation, f d is the dead-band frequency of the generator's primary frequency modulation; Δf is the measured frequency deviation value at the current moment; h is the ratio of the generator's primary frequency modulation capacity to the generator's on-line capacity; K G is the unit regulation power of the generator; P GN is the generator's on-line capacity.

2. The method according to claim 1, wherein When the type of disturbance is a step disturbance, the respectively determining the maximum disturbance power that the system can withstand under steady-state frequency deviation constraints, transient frequency deviation constraints, and generator primary frequency regulation amplitude constraints includes: Determining the maximum disturbance power that the system can withstand under steady-state frequency deviation constraints by using the following method, including: Determining the maximum disturbance power that the system can withstand under transient frequency deviation constraints by using the following method, including: Determining the maximum disturbance power that the system can withstand under generator primary frequency regulation amplitude constraints by using the following method, including: Among them, ΔP max1 is the maximum disturbance power that the system can withstand under the steady-state frequency deviation constraint; K L is the load unit regulation power; P L0 is the load level before the disturbance; Δf ss is the steady-state frequency constraint value; f N is the frequency base value; K G is the generator unit regulation power, P GN is the generator on-line capacity; ΔP max2 is the maximum disturbance power that the system can withstand under the transient frequency deviation constraint; m is the ratio of the generator primary frequency regulation capacity to the generator on-line capacity; ΔP max3 is the maximum disturbance power that the system can withstand under the generator primary frequency regulation amplitude constraint; Δf m is the given maximum frequency deviation constraint; R is the governor speed regulation gain after the unit equivalence; S N is the system base capacity; ζ is the damping ratio; ω n is the natural oscillation angular frequency; α, ω r are intermediate variables; t m is the time when the maximum value of the system frequency deviation appears; R, H, T R and F H are respectively the governor speed regulation gain, inertia time constant, reheater time constant and high-pressure cylinder power ratio after the unit equivalence.

3. The method according to claim 2, characterized in that, The determining the stability of the system based on the maximum disturbance power and the unbalanced power includes: If ΔP > min{ΔP max1 , ΔP max2 , ΔP max3}, then it is determined that the system stability is unstable, and the magnitude of the disturbance power is ΔP; If ΔP ≤ min{ΔP max1 , ΔP max2 , ΔP max3}, then determine that the system stability is stable; Among them, ΔP is the unbalanced power; ΔP max1 is the maximum disturbance power that the system can withstand under the steady-state frequency deviation constraint; ΔP max2 is the maximum disturbance power that the system can withstand under the transient frequency deviation constraint; ΔP max3 is the maximum disturbance power that the system can withstand under the primary frequency regulation amplitude limit constraint of the generator.

4. The method according to claim 1, wherein The method further includes: When the type of disturbance is a second-level ramp disturbance, determining that the system stability is unstable; Determining a first disturbance power change rate, determining a first frequency over-limit time based on the first disturbance power change rate and a preset frequency deviation constraint value, and determining a first over-limit disturbance power based on the first frequency over-limit time and the first disturbance power change rate, including: Determining the first disturbance power change rate by using the following formula, including: Solving for the first frequency over-limit time by using the following formula, including: Determining the first over-limit disturbance power by using the following formula, including: ΔP1 = k m × t m1 , where k m is the first disturbance power change rate; E i is the terminal voltage of the i-th generator; U p is the disturbance point voltage; δ ip is the power angle difference between the i-th generator and the disturbance point; B ip is the conductance between the i-th generator and the disturbance point; Δδ ip is the change in the power angle difference between the i-th generator and the disturbance point; n is the number of generators; t is the sampling time; Δf m is the maximum value of the frequency deviation; K L is the load unit regulation power; R and T R are the governor speed regulation gain and the reheater time constant after the unit equivalence, respectively; T1, T2, k1, and k2 are all intermediate variables; t m1 is the first frequency over-limit time; ζ is the damping ratio; ω n is the natural oscillation angular frequency; ΔP1 is the first over-limit disturbance power.

5. The method according to claim 1, wherein The method further includes: When the type of disturbance is a minute-level ramp disturbance, determining that the system stability is unstable; Determining a second disturbance power change rate, determining a second frequency over-limit time based on the second disturbance power change rate and a preset frequency deviation constraint value, and determining a second over-limit disturbance power based on the second frequency over-limit time and the second disturbance power change rate, including: Determining the second disturbance power change rate by using the following formula, including: Solving for the second frequency over-limit time by using the following formula, including: Determining the second over-limit disturbance power by using the following formula, including: ΔP2 = k f ×t m2 , where k f is the second disturbance power change rate; ΔP L is the primary frequency regulation capacity of the load; h is the ratio of the primary frequency regulation capacity of the generator to the generator's on-line capacity; P GN is the generator's on-line capacity; t1 is the moment when the primary frequency regulation capacity of the generator is exactly exhausted; Δf m is the maximum value of the frequency deviation; Δf1 is the frequency start threshold; K L is the load unit regulation power; T J is the inertia time constant of the generator set; t m2 is the second frequency over-limit time; ΔP2 is the second over-limit disturbance power.

6. A system for determining the frequency stability of a system, characterized in that, The system includes: An unbalanced power determination unit for determining the unbalanced power based on the operating data of the generator sets within the system; A disturbance type determination unit for determining the type of disturbance based on the unbalanced power and a preset power start threshold; A maximum disturbance power determination unit for, when the type of disturbance is a step disturbance, respectively determining the maximum disturbance power that the system can withstand under steady-state frequency deviation constraints, transient frequency deviation constraints, and generator primary frequency regulation amplitude constraints; A stability determination unit for determining the stability of the system based on the maximum disturbance power and the unbalanced power; Among them, the unbalanced power determination unit, which determines the unbalanced power based on the operating data of the generator sets within the system, includes: Among them, ΔP is the unbalanced power; E i is the terminal voltage of the i-th generator; U p is the voltage at the disturbance point; δ ip is the power angle difference between the i-th generator and the disturbance point; B ip is the conductance between the i-th generator and the disturbance point; Δδ ip is the change in the power angle difference between the i-th generator and the disturbance point; n is the number of generators; Among them, the disturbance type determination unit determines the disturbance type based on the unbalanced power and a preset power start threshold, including: If ΔP > ΔP is satisfied sh and ΔP is a fixed value, then determine that the disturbance type is a step disturbance; If ΔP > ΔP is satisfied sh and ΔP is not a fixed value, then determine that the disturbance type is a second-level ramp disturbance If ΔP < ΔP sh and Δf > Δf sh , then it is determined that the disturbance type is a minute-level ramp disturbance; Among them, ΔP is the unbalanced power; ΔP sh is the preset power start threshold, ΔP sh = k1T, where k1 is the maximum power change rate of the minute-level ramp disturbance, and T is the power distribution time; Δf sh is the total frequency deviation generated by the system during primary frequency modulation limiting, Δf sh = Δf G + f d , Δf G is the steady-state frequency deviation brought by the generator participating in primary frequency modulation, f d is the dead-band frequency of the generator's primary frequency modulation; Δf is the measured frequency deviation value at the current moment; h is the ratio of the generator's primary frequency modulation capacity to the generator's on-line capacity; K G is the unit regulation power of the generator; P GN is the generator's on-line capacity.

7. The system according to claim 6, wherein The maximum disturbance power determination unit, when the disturbance type is a step disturbance occurs, respectively determines the maximum disturbance power that the system can withstand under the steady-state frequency deviation constraint, the transient frequency deviation constraint, and the generator primary frequency regulation amplitude constraint, including: Determines the maximum disturbance power that the system can withstand under the steady-state frequency deviation constraint by using the following method, including: Determines the maximum disturbance power that the system can withstand under the transient frequency deviation constraint by using the following method, including: Determines the maximum disturbance power that the system can withstand under the generator primary frequency regulation amplitude constraint by using the following method, including: Among them, ΔP max1 is the maximum disturbance power that the system can withstand under the steady-state frequency deviation constraint; K L is the load unit regulation power; P L0 is the load level before the disturbance; Δf ss is the steady-state frequency constraint value; f N is the frequency base value; K G is the generator unit regulation power, P GN is the generator's on-line capacity; ΔP max2 is the maximum disturbance power that the system can withstand under the transient frequency deviation constraint; m is the ratio of the generator's primary frequency regulation capacity to the generator's on-line capacity; ΔP max3 is the maximum disturbance power that the system can withstand under the generator's primary frequency regulation amplitude constraint; Δf m is the given maximum frequency deviation constraint; R is the governor speed regulation gain after the unit equivalence; S N is the system base capacity; ζ is the damping ratio; ω n is the natural oscillation angular frequency; α, ω r are intermediate variables; t m is the time when the maximum value of the system frequency deviation appears; R, H, T R and F H are respectively the governor speed regulation gain, inertia time constant, reheater time constant and high-pressure cylinder power ratio after the unit equivalence.

8. The system according to claim 7, wherein The stability determination unit determines the stability of the system based on the maximum disturbance power and the unbalanced power, including: If ΔP > min{ΔP max1 , ΔP max2 , ΔP max3}, then it is determined that the system stability is unstable, and the magnitude of the disturbance power is ΔP; If ΔP ≤ min{ΔP max1 , ΔP max2 , ΔP max3}, then the system stability is determined to be stable; Among them, ΔP is the unbalanced power; ΔP max1 is the maximum disturbance power that the system can withstand under the steady-state frequency deviation constraint; ΔP max2 is the maximum disturbance power that the system can withstand under the transient frequency deviation constraint; ΔP max3 is the maximum disturbance power that the system can withstand under the primary frequency regulation amplitude limit constraint of the generator.

9. The system according to claim 6, wherein The system further includes: a first over-limit disturbance power determination unit, for: When the disturbance type is a second-level ramp disturbance occurs, determines that the system stability is unstable; Determines a first disturbance power change rate, determines a first frequency over-limit time based on the first disturbance power change rate and a preset frequency deviation constraint value, and determines a first over-limit disturbance power based on the first frequency over-limit time and the first disturbance power change rate, including: Determines the first disturbance power change rate by using the following formula, including: Solves the first frequency over-limit time by using the following formula, including: Determines the first over-limit disturbance power by using the following formula, including: ΔP1 = k m × t m1 , Among them, k m is the first disturbance power change rate; E i is the terminal voltage of the i-th generator; U p is the disturbance point voltage; δ ip is the power angle difference between the i-th generator and the disturbance point; B ip is the conductance between the i-th generator and the disturbance point; Δδ ip is the change in the power angle difference between the i-th generator and the disturbance point; n is the number of generators; t is the sampling time; Δf m is the maximum value of the frequency deviation; K L is the load unit regulation power; R and T R are respectively the governor speed regulation gain and the reheater time constant after the unit is equivalent; T1, T2, k1, and k2 are all intermediate variables; t m1 is the first frequency over-limit time; ζ is the damping ratio; ω n is the natural oscillation angular frequency; ΔP1 is the first over-limit disturbance power.

10. The system according to claim 6, wherein The system further includes: a first over-limit disturbance power determination unit, for: When the disturbance type is a minute-level ramp disturbance occurs, determines that the system stability is unstable; Determines a second disturbance power change rate, determines a second frequency over-limit time based on the second disturbance power change rate and a preset frequency deviation constraint value, and determines a second over-limit disturbance power based on the second frequency over-limit time and the second disturbance power change rate, including: Determines the second disturbance power change rate by using the following formula, including: Solves the second frequency over-limit time by using the following formula, including: Determines the second over-limit disturbance power by using the following formula, including: ΔP2 = k f × t m2 , where k f is the second disturbance power change rate; ΔP L is the primary frequency regulation capacity of the load; h is the ratio of the primary frequency regulation capacity of the generator to the generator's on-line capacity; P GN is the generator's on-line capacity; t1 is the moment when the primary frequency regulation capacity of the generator is just completely exhausted; Δf m is the maximum value of the frequency deviation; Δf1 is the frequency startup threshold; K L is the load unit regulation power; T J is the inertia time constant of the generator set; t m2 is the second frequency over-limit time; ΔP2 is the second over-limit disturbance power.

11. A computer-readable storage medium having a computer program stored thereon, characterized in that, When this program is executed by a processor, it implements the steps of the method described in any one of claims 1-5.

12. An electronic device, characterized in that, Including: The computer-readable storage medium described in claim 11; And One or more processors for executing the program in the computer-readable storage medium.

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