Method for evaluating stability margin of continuous low voltage ride through of wind turbine generator system and related device

Abstract

The application provides a wind turbine continuous low voltage ride through stability margin evaluation method, device, equipment and readable storage medium. When it is necessary to evaluate the continuous low voltage ride through phenomenon of the wind turbine in the wind and fire bundled delivery system, the method provided by the embodiment of the application can effectively explain and describe the mechanism of the continuous low voltage ride through phenomenon of the wind turbine in the high-power wind turbine and low-power synchronous unit scene of the wind and fire bundled delivery system, and determines the stability margin evaluation index of the wind turbine continuous low voltage ride through phenomenon. The stability margin quantitative evaluation of the wind turbine continuous low voltage ride through is completed by using the evaluation index, which is helpful to understand the fault cause and processing mode of the continuous low voltage ride through phenomenon of the wind turbine in the high-power wind turbine and low-power synchronous unit scene of the wind and fire bundled delivery system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power facility management, and in particular to a wind turbine continuous low-voltage ride-through stability margin evaluation method, device, equipment and readable storage medium. BACKGROUND

[0002] With the development of science and technology, in some coastal areas rich in wind energy resources, the power grid structure is stable, and the wind power grid connection conditions are good, so a large-capacity wind farm can be planned. By the end of 2030, the planned offshore wind power installation in a certain region reaches 30 million kilowatts, and in the future, large-scale offshore wind power and adjacent conventional power sources will be jointly concentrated in the receiving end of the power grid in multiple regions, and will supply power to the load center. The concentrated access of new energy and the use of transmission channels by conventional power sources may affect the transient stability characteristics of the regional system and the transmission capacity of the transmission channel. Unlike traditional power systems dominated by synchronous machines, new energy dominates the new type of power system, and there is interaction between new energy units and alternating current systems. In the fault transient process, both will jointly affect the stability of the regional system. Because wind turbine generators themselves do not have dynamic reactive power support capability, after a large number of wind turbine generators are connected, the opening of synchronous machines will be correspondingly reduced, which may lead to a decrease in the strength of the alternating current system and a more prominent voltage stability problem of the regional system. Large-scale wind power collection systems will experience repeated voltage fluctuations in actual transient processes, with large fluctuation amplitudes and fast switching rates between peak and valley values. This is significantly different from voltage fluctuations caused by wind energy randomness and reactive power compensation device operation. Repeated wind turbine generator off-grid due to continuous ride-through failure may occur multiple times during regional system operation, seriously threatening the safe and stable operation of the power grid. In addition, large-scale photovoltaic collection stations also have voltage stability problems of repeated fluctuations, leading to large-area photovoltaic off-grid and restricting the regional power transmission capacity.

[0003] In view of the repeated voltage fluctuations of large-scale new energy collection systems in actual operation, existing research mainly focuses on the influence of active power and reactive power control strategies in wind turbine low-voltage ride-through on the transient voltage at the generator end and the influence of the reactive power recovery rate of direct-drive wind turbine generators on the repeated voltage fluctuations at the wind turbine end during the transient process. However, none of the existing research schemes considers the interaction between new energy units and alternating current grids, resulting in repeated voltage fluctuations at the wind turbine end in wind and fire bundled concentrated sending-out systems, and no evaluation method for the continuous low-voltage ride-through margin of wind turbines has been formed, making it impossible to evaluate the stability margin of the continuous low-voltage ride-through of wind turbines in wind and fire bundled sending-out systems. SUMMARY

[0004] The application aims to solve at least one of the above technical defects, and provides a wind turbine continuous low voltage ride through stability margin evaluation method, device, equipment and readable storage medium, which are used to solve the technical defect that the stability margin of the wind turbine continuous low voltage ride through phenomenon in the wind-fire bundled sending system cannot be evaluated in the prior art.

[0005] A wind turbine continuous low voltage ride through stability margin evaluation method, comprising:

[0006] The output information of the wind turbine and the output information of the synchronous unit of the wind-fire bundled sending system are analyzed by using a preset equivalent model of the wind-fire bundled sending system.

[0007] Based on the output information of the synchronous unit and the output information of the wind turbine of the wind-fire bundled sending system, a preset evaluation index is used to evaluate the stability margin of the wind turbine continuous low voltage ride through phenomenon of the wind-fire bundled sending system.

[0008] Preferably, the preset equivalent model of the wind-fire bundled sending system creation process comprises:

[0009] The dynamic characteristics of the wind turbine of the wind-fire bundled sending system are simulated by using a controlled current source.

[0010] The thermal power unit of the wind-fire bundled sending system is equivalent to a voltage source with internal resistance.

[0011] The excitation dynamic process of the thermal power unit of the wind-fire bundled sending system is ignored.

[0012] The resistance and susceptance in the transmission line of the wind-fire bundled sending system are ignored.

[0013] The receiving end network connected to the wind-fire bundled sending system is replaced by an infinite power source, so as to obtain an equivalent model of the wind-fire bundled sending system as the equivalent model of the wind-fire bundled sending system.

[0014] Preferably, the node equation of the preset equivalent model of the wind-fire bundled sending system comprises the following:

[0015]

[0016] Wherein,

[0017] E G represents the internal potential of the synchronous machine of the wind-fire bundled sending system;

[0018] U0represents the infinite bus voltage amplitude;

[0019] U L represents the bus voltage of the wind-fire bundled sending system;

[0020] U W represents a wind power port voltage of the wind-thermal bundled generation system;

[0021] I0represents an infinite source bus node injection current;

[0022] I L represents a collection bus injection current of the wind-thermal bundled generation system;

[0023] I G represents a synchronous machine node injection current of the wind-thermal bundled generation system;

[0024] I W represents a wind power node injection current of the wind-thermal bundled generation system;

[0025] Y 00 represents a self-admittance of an infinite source bus node;

[0026] Y L0 represents a mutual admittance between an infinite source bus node and a collection bus node of the wind-thermal bundled generation system;

[0027] Y G0 represents a mutual admittance between an infinite source bus node and a synchronous machine node of the wind-thermal bundled generation system;

[0028] Y W0 represents a mutual admittance between an infinite source bus node and a wind power port node of the wind-thermal bundled generation system;

[0029] Y 0L represents a mutual admittance between an infinite source bus node and a collection bus node of the wind-thermal bundled generation system, wherein Y 0L = Y L0 ;

[0030] Y LL represents a self-admittance of a collection bus node of the wind-thermal bundled generation system;

[0031] Y GL represents a mutual admittance between a collection bus node of the wind-thermal bundled generation system and a synchronous machine node of the wind-thermal bundled generation system;

[0032] Y WL represents a mutual admittance between a collection bus node of the wind-thermal bundled generation system and a wind power port node of the wind-thermal bundled generation system;

[0033] Y 0G represents a mutual admittance between an infinite source bus node and a synchronous machine node of the wind-thermal bundled generation system, wherein Y 0G = Y G0 ;

[0034] Y LG represents mutual admittance between the wind-thermal bundled sending-out system's collection bus node and the wind-thermal bundled sending-out system's synchronous machine node, wherein Y LG = Y GL ;

[0035] Y GG represents self-admittance of the wind-thermal bundled sending-out system's synchronous machine node;

[0036] Y WG represents mutual admittance between the wind-thermal bundled sending-out system's synchronous machine node and the wind-thermal bundled sending-out system's wind power port node;

[0037] Y 0W represents mutual admittance between the infinite power supply bus node and the wind-thermal bundled sending-out system's wind power port node, wherein Y 0W = Y W0 ;

[0038] Y LW represents mutual admittance between the wind-thermal bundled sending-out system's collection bus node and wind power port node, wherein Y LW = Y WL ;

[0039] Y GW represents mutual admittance between the wind-thermal bundled sending-out system's synchronous machine node and the wind-thermal bundled sending-out system's wind power port node, wherein Y GW = Y WG ;

[0040] Y WW represents self-admittance of the wind-thermal bundled sending-out system's wind power port node.

[0041] Preferably, the preset evaluation index is set as a difference between a minimum voltage limit value of the wind-thermal bundled sending-out system when the wind-thermal bundled sending-out system's wind turbine is normally operated and a maximum synchronous machine power angle swing value of the wind-thermal bundled sending-out system during the fault recovery process;

[0042] wherein,

[0043] The maximum synchronous machine power angle swing value of the wind-thermal bundled sending-out system is determined according to the synchronous machine power angle characteristic curve and the synchronous machine active power output of the wind-thermal bundled sending-out system.

[0044] Preferably, the evaluation of the stability margin of the continuous low-voltage ride-through of the wind-thermal bundled sending-out system's wind turbine by using the preset evaluation index comprises:

[0045] If the difference between the minimum voltage limit value of the wind turbine in normal operation of the wind-thermal bundled sending-out system and the maximum synchronous machine power angle swing value of the wind-thermal bundled sending-out system is greater than zero, the minimum voltage limit value of the wind turbine in normal operation of the wind-thermal bundled sending-out system is greater than the maximum synchronous machine power angle swing value of the wind-thermal bundled sending-out system, the maximum synchronous machine power angle swing value of the wind-thermal bundled sending-out system in the fault recovery process will not exceed the minimum voltage limit value of the wind turbine in normal operation of the wind-thermal bundled sending-out system, the wind turbine port voltage of the wind-thermal bundled sending-out system will not be lower than the minimum voltage limit value of the wind turbine in normal operation of the wind-thermal bundled sending-out system, and the wind turbine of the wind-thermal bundled sending-out system will not have continuous low voltage ride-through phenomenon;

[0046] If the difference between the minimum voltage limit value of the wind turbine in normal operation of the wind-thermal bundled sending-out system and the maximum synchronous machine power angle swing value of the wind-thermal bundled sending-out system is less than zero, the minimum voltage limit value of the wind turbine in normal operation of the wind-thermal bundled sending-out system is less than the maximum synchronous machine power angle swing value of the wind-thermal bundled sending-out system, the maximum synchronous machine power angle swing value of the wind-thermal bundled sending-out system in the fault recovery process will exceed the minimum voltage limit value of the wind turbine in normal operation of the wind-thermal bundled sending-out system more than once, the wind turbine port voltage of the wind-thermal bundled sending-out system will be lower than the minimum voltage limit value of the wind turbine in normal operation of the wind-thermal bundled sending-out system more than once, and the wind turbine of the wind-thermal bundled sending-out system will have continuous low voltage ride-through phenomenon.

[0047] Preferably, the calculation formula of the synchronous machine power angle characteristic curve of the wind-thermal bundled sending-out system comprises:

[0048]

[0049] Wherein,

[0050] P represents the output power of the synchronous machine of the wind-thermal bundled sending-out system;

[0051] E G represents the internal potential of the synchronous machine of the wind-thermal bundled sending-out system;

[0052] U0 represents the voltage amplitude of the infinite bus;

[0053] X l1 represents the impedance of the line Line1 in the equivalent model of the wind-thermal bundled sending-out system;

[0054] X l2 = X g + X T + X' d , X l2represents the sum of the internal impedance of the synchronous machine transformer and the transient reactance of the synchronous machine of the wind-thermal bundled sending-out system, wherein X g represents the impedance of line Line2; X T represents the internal impedance of the synchronous machine transformer of the wind-thermal bundled sending-out system; X' d represents the transient reactance of the synchronous machine of the wind-thermal bundled sending-out system;

[0055] δ g represents the power angle of the synchronous machine of the wind-thermal bundled sending-out system;

[0056] K1represents the ratio between the impedance of line Line1 in the equivalent model of the wind-thermal bundled sending-out system and the sum of the impedance of line Line1 and the impedance of line Line2;

[0057] P W represents the active power output of the wind power of the wind-thermal bundled sending-out system;

[0058] U W represents the amplitude of the voltage at the wind power port of the wind-thermal bundled sending-out system;

[0059] wherein,

[0060]

[0061] wherein,

[0062] A = (K1EG) 2 +(K2EG) 2 +2K1K2E G U0cos(δ g )

[0063] wherein,

[0064] u d represents the d-axis component of the grid-side converter voltage of the wind-thermal bundled sending-out system;

[0065] u q represents the d-axis component of the grid-side converter voltage of the wind-thermal bundled sending-out system;

[0066] K2represents the ratio between the impedance of line Line2 in the equivalent model of the wind-thermal bundled sending-out system and the sum of the impedance of line Line1 and the impedance of line Line2;

[0067] X l5 =X l3 +X l4 , X l5 represents X l3 and Xl4 X l3 represents the sum of the internal impedance of the transformer T2 connected to the wind power in the equivalent model of the wind-thermal bundled sending-out system and the impedance of the line Line3 and the impedance of the line Line4;

[0068] I W represents the amplitude of the output current of the wind power of the wind-thermal bundled sending-out system;

[0069] δ W represents the phase angle of the wind power port of the wind-thermal bundled sending-out system;

[0070] wherein,

[0071]

[0072] wherein,

[0073]

[0074] Preferably, the determination process of the maximum swing of the power angle of the synchronous machine of the wind-thermal bundled sending-out system comprises:

[0075] determining the power angle characteristic curve of the synchronous machine of the wind-thermal bundled sending-out system and the active power output of the synchronous machine;

[0076] determining the maximum swing of the power angle of the synchronous machine of the wind-thermal bundled sending-out system by the equal-area rule according to the power angle characteristic curve of the synchronous machine of the wind-thermal bundled sending-out system and the active power output of the synchronous machine.

[0077] A device for evaluating the stability margin of continuous low voltage ride through of a wind turbine, comprising:

[0078] an analysis unit configured to analyze the output information of the wind turbine and the output information of the synchronous machine of the wind-thermal bundled sending-out system by using a preset equivalent model of the wind-thermal bundled sending-out system;

[0079] an evaluation unit configured to evaluate the stability margin of continuous low voltage ride through of the wind turbine of the wind-thermal bundled sending-out system by using a preset evaluation index based on the output information of the wind turbine and the output information of the synchronous machine of the wind-thermal bundled sending-out system.

[0080] A device for evaluating the stability margin of continuous low voltage ride through of a wind turbine, comprising: one or more processors, and a memory;

[0081] The memory stores computer readable instructions, which, when executed by the one or more processors, implement the steps of the method for evaluating the stability margin of continuous low voltage ride through of a wind turbine as described in any of the foregoing.

[0082] A readable storage medium, in which computer readable instructions are stored, when executed by one or more processors, cause the one or more processors to implement the steps of the stability margin evaluation method of the wind turbine continuous low voltage ride through as described in any of the foregoing.

[0083] As can be seen from the technical solutions described above, the stability margin of the continuous low voltage ride through of the wind turbine in the wind-thermal bundled delivery system is related to the output of the synchronous unit and the output of the wind turbine in the wind-thermal bundled delivery system. Therefore, when it is necessary to evaluate the stability margin of the continuous low voltage ride through of the wind turbine in the wind-thermal bundled delivery system, the method provided in the embodiments of the present application can use a preset equivalent model of the wind-thermal bundled delivery system to analyze the output information of the wind turbine and the output information of the synchronous unit in the wind-thermal bundled delivery system. The preset equivalent model of the wind-thermal bundled delivery system is created according to each node of the wind-thermal bundled delivery system. Therefore, the output information of the wind turbine and the output information of the synchronous unit in the wind-thermal bundled delivery system can be effectively determined through the equivalent model of the wind-thermal bundled delivery system, so that the stability margin of the continuous low voltage ride through of the wind turbine in the wind-thermal bundled delivery system can be evaluated based on the output information of the synchronous unit and the output information of the wind turbine in the wind-thermal bundled delivery system and using a preset evaluation index.

[0084] As can be seen from the above description, the method provided in the embodiments of the present application can effectively explain and describe the mechanism of the continuous low voltage ride through of the wind turbine in the wind-thermal bundled delivery system under the scenario of high output of the wind turbine and low output of the synchronous unit, and determine the stability margin evaluation index of the continuous low voltage ride through of the wind turbine, so as to complete the quantitative evaluation of the stability margin of the continuous low voltage ride through of the wind turbine, which is helpful to understand the fault cause and processing mode of the continuous low voltage ride through of the wind turbine in the wind-thermal bundled delivery system under the scenario of high output of the wind turbine and low output of the synchronous unit. BRIEF DESCRIPTION OF DRAWINGS

[0085] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed in the embodiments or the prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0086] Figure 1 A flowchart of a method for evaluating the stability margin of the continuous low voltage ride through of the wind turbine provided in the embodiments of the present application;

[0087] Figure 2A simplified model structure schematic diagram of a wind-fire bundled sending-out system provided by an embodiment of the present application;

[0088] Figure 3 An equivalent model structure schematic diagram of a wind-fire bundled sending-out system provided by an embodiment of the present application;

[0089] Figure 4 A synchronous machine power angle curve and a wind power terminal voltage curve of a wind-fire bundled sending-out system provided by an embodiment of the present application;

[0090] Figure 5 A wind power generator terminal voltage and output, a synchronous machine power angle and output simulation result schematic diagram of a wind-fire bundled sending-out system under a working condition provided by an embodiment of the present application;

[0091] Figure 6 A wind power generator terminal voltage and output, a synchronous machine power angle and output simulation result schematic diagram of a wind-fire bundled sending-out system under another working condition provided by an embodiment of the present application;

[0092] Figure 7 A stability margin evaluation device structure schematic diagram of a wind power generator continuous low voltage ride through provided by an embodiment of the present application;

[0093] Figure 8 A hardware structure block diagram of a stability margin evaluation device of a wind power generator continuous low voltage ride through disclosed by an embodiment of the present application. DETAILED DESCRIPTION

[0094] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0095] In view of the fact that most of the stability margin evaluation schemes of wind power generator continuous low voltage ride through are difficult to adapt to complex and changeable business requirements, the present applicant has researched a stability margin evaluation scheme of wind power generator continuous low voltage ride through. The method provided by the embodiments of the present application can effectively explain the mechanism of the continuous low voltage ride through phenomenon of the wind power generator under the high output of the wind power generator and the low output of the synchronous generator in the wind-fire bundled sending-out system, and determine the stability margin evaluation index of the wind power continuous low voltage ride through phenomenon. The stability margin of the wind power continuous low voltage ride through is quantitatively evaluated by using the evaluation index, which is helpful to understand the fault causes and processing methods of the continuous low voltage ride through phenomenon of the wind power generator under the high output of the wind power generator and the low output of the synchronous generator in the wind-fire bundled sending-out system.

[0096] The methods provided by the embodiments of the present application can be used in numerous general purpose or special purpose computing device environments or configurations. For example: personal computer, server computer, handheld or portable device, tablet device, multiprocessor system, distributed computing environment that includes any of the above systems or devices, and the like.

[0097] The embodiments of the present application provide a stability margin evaluation method for continuous low voltage ride through of a wind turbine generator set. The method can be applied in various wind turbine generator set management systems or wind-thermal bundled sending out systems, and can also be applied in various computer terminals or intelligent terminals. The execution subject can be a processor or server of the computer terminal or the intelligent terminal.

[0098] The flow of the stability margin evaluation method for continuous low voltage ride through of a wind turbine generator set provided by the embodiments of the present application will be described below with reference to Figure 1 The flow can include the following steps as shown in Figure 1

[0099] In step S101, the output information of the wind turbine generator set and the output information of the synchronous unit of the wind-thermal bundled sending out system are analyzed by using a preset equivalent model of the wind-thermal bundled sending out system.

[0100] Specifically, in actual application, the continuous low voltage ride through phenomenon of the wind turbine generator set of the wind-thermal bundled sending out system is related to the output of the synchronous unit of the wind-thermal bundled sending out system and the output of the wind turbine generator set.

[0101] Therefore, in order to better analyze the output of the synchronous unit of the wind-thermal bundled sending out system and the output of the wind turbine generator set, the wind-thermal bundled sending out system can be equivalent to a simplified model for analysis.

[0102] The preset equivalent model of the wind-thermal bundled sending out system can include the following:

[0103] The preset equivalent model of the wind-thermal bundled sending out system can include the following:

[0104] The dynamic characteristics of the wind turbine generator set of the wind-thermal bundled sending out system are simulated by a controlled current source; the thermal power unit of the wind-thermal bundled sending out system is equivalent to a voltage source with internal resistance; the excitation dynamic process of the thermal power unit of the wind-thermal bundled sending out system is ignored; the resistance and susceptance in the transmission line of the wind-thermal bundled sending out system are ignored; the receiving network connected to the wind-thermal bundled sending out system is replaced by an infinite power source, so that the equivalent model of the wind-thermal bundled sending out system can be obtained as the equivalent model of the wind-thermal bundled sending out system.

[0105] For example,

[0106] For example, the wind-thermal bundled sending out system can be simplified as a wind-thermal bundled sending out system simplified model as shown in Figure 2 .​

[0107] wherein,

[0108] As Figure 2 shown, in the wind-fire bundled sending-out system, the regional wind farm and the thermal power unit are replaced by the single-machine aggregation equivalent model.

[0109] In the simplified model of the wind-fire bundled sending-out system, the dynamic characteristics of the wind power unit can be simulated by a controlled current source, and the excitation dynamic process of the thermal power unit can be ignored, and the thermal power unit is equivalent to a voltage source with internal impedance; and in the analysis, the resistance and susceptance in the transmission line are ignored, and the receiving network connected to the sending-out system is replaced by an infinite power source, and the equivalent model of the sea wind sending-out system obtained in this way is shown in FIG. 2. Figure 3

[0110] As Figure 3 shown, the physical meanings of the parameters of the equivalent model of the wind-fire bundled sending-out system can be shown in Table 1 as follows:

[0111] Table 1: Parameters and physical meanings of the equivalent model of the wind-fire bundled sending-out system

[0112]

[0113]

[0114] Based on the equivalent model of the wind-fire bundled sending-out system introduced above, the node equation of the equivalent model of the wind-fire bundled sending-out system can be obtained as follows:

[0115]

[0116] wherein,

[0117] E G may represent the internal potential of the synchronous machine of the wind-fire bundled sending-out system;

[0118] U0may represent the voltage amplitude of the bus of the infinite power source;

[0119] U L may represent the voltage of the collection bus of the wind-fire bundled sending-out system;

[0120] U W may represent the voltage of the wind power port of the wind-fire bundled sending-out system;

[0121] I0may represent the injected current of the bus of the infinite power source;

[0122] I L may represent the injected current of the collection bus of the wind-fire bundled sending-out system;

[0123] I G ​This can represent the current injected into the synchronous node of the wind-fire bundling and power transmission system;

[0124] I W This can represent the wind power node injection current in a wind-fire bundled power transmission system;

[0125] Y 00 It can represent the self-admittance of an infinite power supply bus node;

[0126] Y L0 It can represent the mutual admittance between the infinite power supply bus node and the wind and fire bundled transmission system collection bus node;

[0127] Y G0 It can represent the mutual admittance between the infinite power bus node and the synchronous machine node of the wind-fire bundled power transmission system;

[0128] Y W0 It can represent the mutual admittance between the infinite power bus node and the wind power port node of the wind-thermal bundled transmission system;

[0129] Y 0L Y can represent the mutual admittance between the infinite power supply bus node and the combined wind and thermal power transmission system receiving bus node, where Y 0L =Y L0 ;

[0130] Y LL It can represent the self-admittance of the bus node of the wind and fire bundled power transmission system;

[0131] Y GL It can represent the mutual admittance between the bus node of the wind and fire bundled power transmission system and the synchronous machine node of the wind and fire bundled power transmission system;

[0132] Y WL It can represent the mutual admittance between the bus node of the wind-thermal bundled power transmission system and the wind power port node of the wind-thermal bundled power transmission system;

[0133] Y 0G Y can represent the mutual admittance between the infinite power bus node and the synchronous machine node of the combined wind and thermal power transmission system, where Y 0G =Y G0 ;

[0134] Y LG Y can represent the mutual admittance between the bus node of the combined wind and fire power transmission system and the synchronous machine node of the combined wind and fire power transmission system, where Y LG =Y GL ;

[0135] Y GG It can represent the self-admittance of the synchronous machine node in the wind-fire bundled delivery system;

[0136] Y WG may represent the mutual admittance between the synchronous machine node of the wind-thermal bundled delivery system and the wind power port node of the wind-thermal bundled delivery system;

[0137] Y 0W may represent the mutual admittance between the infinite bus node and the wind power port node of the wind-thermal bundled delivery system, wherein Y 0W = Y W0 ;

[0138] Y LW may represent the mutual admittance between the wind-thermal bundled delivery system bus node and the wind power port node, wherein Y LW = Y WL ;

[0139] Y GW may represent the mutual admittance between the synchronous machine node of the wind-thermal bundled delivery system and the wind power port node of the wind-thermal bundled delivery system, wherein Y GW = Y WG ;

[0140] Y WW may represent the self-admittance of the wind power port node of the wind-thermal bundled delivery system.

[0141] In actual application, since the bus L injects current I L = 0, I L = 0, the bus L voltage expression as shown in formula (2) and the wind power port voltage expression as shown in formula (3) can be derived by substituting the above formula (1) with I L = 0, I L = 0.

[0142]

[0143]

[0144] wherein,

[0145] X l2 = X g + X T + X d ’;

[0146]

[0147] X l5 = X l3 + X l4

[0148]

[0149]

[0150] wherein,

[0151] Exponential notation for bus L voltage complex of a wind-thermal bundled transmission system can be represented as

[0152] δ p Phase angle of bus L voltage of a wind-thermal bundled transmission system can be represented as

[0153] K1 can represent the ratio between line Line1 impedance and the sum of line Line1 impedance and line Line2 impedance in an equivalent model of a wind-thermal bundled transmission system

[0154] Exponential notation for synchronous machine internal voltage complex of a wind-thermal bundled transmission system can be represented as

[0155] δ g Power angle of a synchronous machine of a wind-thermal bundled transmission system can be represented as

[0156] K2 can represent the ratio between line Line2 impedance and the sum of line Line1 impedance and line Line2 impedance in an equivalent model of a wind-thermal bundled transmission system

[0157] Exponential notation for bus voltage complex of an infinite source can be represented as

[0158] j can represent imaginary unit

[0159] δ w Phase angle of wind power port voltage of a wind-thermal bundled transmission system can be represented as

[0160] X l4 Line Line4 impedance of a wind-thermal bundled transmission system equivalent model can be represented as

[0161] φ i Wind power factor angle of a wind-thermal bundled transmission system can be represented as

[0162] Exponential notation for wind power port injection current complex can be represented as

[0163] Exponential notation for wind power port voltage complex can be represented as

[0164] X l2 Line Line2 impedance of a wind-thermal bundled transmission system can be represented as

[0165] X g Line Line2 impedance of a wind-thermal bundled transmission system can be represented as

[0166] X TThis can represent the internal impedance of the synchronous transformer in a wind-fire bundling and power delivery system;

[0167] X d 'Can represent the transient reactance of the synchronous machine in a wind-fire bundled power transmission system;

[0168] X l4 X can represent l1 With X l2 product divided by X l1 With X l2 sum;

[0169] X l5 X can represent l3 With X l4 sum;

[0170] X l3 It can represent the sum of the internal impedance of transformer T2 connected to the wind power plant in the wind-fire bundled power transmission system, the impedance of line Line3, and the impedance of line Line4.

[0171] X l1 This can represent the impedance of Line 1 in the wind and fire bundled power transmission system;

[0172] When the wind-fire bundling and delivery system is operating normally, the output power characteristic of the synchronous machine of the wind-fire bundling and delivery system can be expressed as shown in the following formula (4):

[0173]

[0174] in,

[0175] P can represent the active power output of the synchronous machine in the wind-fire bundling and power transmission system (equal to the electromagnetic power of the synchronous machine);

[0176] Q can represent the reactive power output of the synchronous machine in the wind-fire bundled power supply system;

[0177] Substituting equation (1) into equation (4), we can obtain the following expression for the electromagnetic power output of the synchronous machine of the wind and fire bundling system:

[0178]

[0179] in,

[0180] δ g This can represent the power angle of the synchronizing machine in a wind-fire bundling and delivery system;

[0181] I W It can represent the amplitude of the wind power output current in a wind-baling power transmission system;

[0182] δ w It can represent the phase angle of the wind power port in a combined wind and thermal power transmission system;

[0183] φ i may represent the wind power factor angle of the wind-thermal bundled sending-out system;

[0184] In the non-fault working condition, the wind turbine of the wind-thermal bundled sending-out system does not emit reactive power, its power factor angle φ i = 0, and the output current amplitude is

[0185] Substituting φ i = 0 and into the above formula (5), the calculation formula of the synchronous machine power angle characteristic curve of the wind-thermal bundled sending-out system is as shown in the following formula (6), including:

[0186]

[0187] wherein,

[0188] P can represent the synchronous machine output power (equal to the synchronous machine output active power) of the wind-thermal bundled sending-out system;

[0189] P W may represent the wind power active output of the wind-thermal bundled sending-out system;

[0190] U W may represent the wind power port voltage amplitude of the wind-thermal bundled sending-out system;

[0191] As can be seen from formula (6), the synchronous machine power angle characteristic of the wind-thermal bundled sending-out system is related to the wind power port voltage amplitude U W , the phase angle δ w , and the wind power active output P W .

[0192] In the wind-thermal bundled sending-out system, the wind turbine adopts the directional phase-locked control mode based on the grid-side converter d-axis voltage, the voltage d-axis component u d = U W , the q-axis component u q = 0, the current d-axis component i d = I W , and the q-axis component i q = 0, which are substituted into formula (3) to obtain:

[0193] u d = K1E G cos(δ g - δ w ) + K2U0cosδ w = U W (7)

[0194] u q = K1EG sin(δ g -δ w )-K2U0sinδ w +X l5 I W =0 (8)

[0195] wherein, formula (7) and (8),

[0196] u d represents the d-axis component of the grid-side converter voltage of the wind-thermal bundled sending-out system;

[0197] u q represents the d-axis component of the grid-side converter voltage of the wind-thermal bundled sending-out system;

[0198] By combining the above formula (7), formula (8), the wind power port voltage amplitude U of the wind-thermal bundled sending-out system can be obtained W The expression is shown in the following formula (9):

[0199]

[0200] wherein,

[0201] A=(K1E G ) 2 +(K2E G ) 2 +2K1K2E G U0cos(δ g ) (10)

[0202] wherein, since the wind power factor angle φ of the wind-thermal bundled sending-out system i =0, Therefore, formula (3) can be transformed into:

[0203]

[0204] wherein,

[0205] By combining formula (9), formula (11), the wind power port voltage phase angle δ of the wind-thermal bundled sending-out system w The expression is shown in the following formula (12):

[0206]

[0207] wherein,

[0208]

[0209] In summary, when the wind-thermal bundled sending-out system is normally operated, the mathematical expression of the synchronous machine output electromagnetic power is shown in formula (6).

[0210] When the operation parameters of the wind-thermal bundled sending-out system are determined, the electromagnetic power P of the synchronous machine can be a function of the power angle δ of the synchronous machine. g

[0211] The mathematical expression of the wind turbine terminal voltage of the wind-thermal bundled sending-out system is shown in equation (9), which is affected by the change of the power angle δ of the synchronous machine. g

[0212] In step S102, based on the output information of the synchronous machine group and the output information of the wind turbine of the wind-thermal bundled sending-out system, the preset evaluation index is used to evaluate the stability margin of the continuous low-voltage ride-through of the wind turbine of the wind-thermal bundled sending-out system.

[0213] Specifically, as known from the above description, the method provided in the embodiments of the present application can determine the output information of the synchronous machine group and the output information of the wind turbine of the wind-thermal bundled sending-out system by using the preset equivalent model of the wind-thermal bundled sending-out system.

[0214] As known from the above description, the continuous low-voltage ride-through of the wind turbine of the wind-thermal bundled sending-out system is related to the output information of the synchronous machine group and the output information of the wind turbine of the wind-thermal bundled sending-out system.

[0215] For example,

[0216] According to the above-mentioned electromagnetic power expression of the synchronous machine and the wind turbine port voltage expression, the synchronous machine power angle curve and the wind turbine terminal voltage curve of the wind-thermal bundled sending-out system under different output ratios of the wind turbine can be obtained, as shown in the following Figure 4

[0217] Among them,

[0218] Figure 4 (a) is the schematic diagram of the synchronous machine power angle curve of the wind-thermal bundled sending-out system, and (b) is the schematic diagram of the wind turbine terminal voltage curve of the wind-thermal bundled sending-out system.

[0219] As known from Figure 4 Compared with the case where the output ratio of the wind turbine is low and the output ratio of the synchronous machine is high, when the output ratio of the wind turbine is high, the synchronous machine power angle characteristic curve and the wind turbine terminal voltage curve of the wind-thermal bundled sending-out system are both moved downward, the wind turbine terminal voltage decreases with the increase of the synchronous machine power angle, and the minimum voltage limit value U LVRT of the normal operation of the wind turbine corresponds to the synchronous machine power angle δ LVRT , and accordingly decreases, i.e. δ LVRT < δ LVRT When the output of the wind turbine is higher than a certain level, after the fault is removed, the maximum value δ cr of the synchronous machine power angle swing is greater than δ LVRT ​​​In the process of synchronous machine power angle recovery, the synchronous machine power angle swing will cause δ g to be greater than δ LVRT , so that the voltage U W at the end of the wind power is repeatedly lower than the minimum voltage limit U LVRT for normal operation of the wind power during the recovery process, and the continuous low voltage ride-through process of the wind turbine generator set of the wind-fire bundled sending-out system is caused, which can cause the voltage at the end of the wind power to repeatedly fluctuate.

[0220] For the scenario in which the proportion of wind power output is low and the proportion of synchronous machine output is high, the minimum voltage limit U LVRT for normal operation of the wind power corresponds to a large synchronous machine power angle δ LVRT , and after the fault is removed, the maximum value δ cr ' of the synchronous machine power angle swing is not greater than δ LVRT ', so that the continuous low voltage ride-through of the wind turbine generator set is not caused.

[0221] Therefore, after the output information of the synchronous machine set of the wind-fire bundled sending-out system and the output information of the wind turbine generator set are determined, the preset evaluation index can be used to evaluate the stability margin of the continuous low voltage ride-through of the wind turbine generator set of the wind-fire bundled sending-out system.

[0222] wherein,

[0223] The preset evaluation index can be set as the difference between the minimum voltage limit value of the wind turbine generator set of the wind-fire bundled sending-out system during normal operation of the wind turbine generator set of the wind-fire bundled sending-out system during the fault recovery process and the maximum value of the synchronous machine power angle swing of the wind-fire bundled sending-out system.

[0224] wherein,

[0225] The maximum value of the synchronous machine power angle swing of the wind-fire bundled sending-out system can be determined according to the synchronous machine power angle characteristic curve of the wind-fire bundled sending-out system and the active power output of the synchronous machine.

[0226] wherein,

[0227] δ LVRT is determined by the voltage amplitude U W at the end of the wind turbine generator set and the minimum voltage limit U LVRT for normal operation of the wind power.

[0228] As can be known from the above introduction, the voltage amplitude U W at the end of the wind turbine generator set is affected by the size of the wind power active power P W , so that when the wind power output is determined, the size of δ W can be determined by U LVRT and U LVRT .

[0229] As can be seen from the above introduction, the power angle characteristic curve of the synchronous machine is also affected by the active power output P of the wind power. W The influence of the synchronous machine and wind power output of the combined wind and thermal power transmission system is determined by the synchronous machine's power angle characteristic curve and the synchronous machine's active power output P. m The maximum value δ of the synchronous machine's power angle oscillation can be calculated using the equal area rule. cr .

[0230] For example,

[0231] First, the power angle characteristic curve and active power output of the synchronous machine of the wind-fire bundling and delivery system can be determined. Then, based on the power angle characteristic curve and active power output of the synchronous machine of the wind-fire bundling and delivery system, the maximum value of the power angle swing of the synchronous machine of the wind-fire bundling and delivery system can be determined by the equal area rule.

[0232] in,

[0233] The difference between the minimum voltage limit of the wind turbine generator during normal operation and the maximum value of the synchronous motor power angle swing of the wind-fire bundled power transmission system can be expressed as follows (14):

[0234] VS = δ LVRT -δ cr (14)

[0235] For example,

[0236] If the minimum voltage limit U of the wind turbine unit in the wind-fire bundled power supply system is normally operating... LVRT The maximum value of the synchronous machine power angle swing δ of the wind and fire bundling and delivery system cr If the difference is greater than zero, then the minimum voltage limit U of the wind turbine generator set in the wind-fire bundled power transmission system during normal operation is... LVRT The maximum synchronous power angle swing value δ of the wind-fire bundling and sending system is greater than that of the wind-fire bundling and sending system. cr During the fault recovery process of the wind-fire bundling and power transmission system, the maximum value of the synchronous motor power angle swing δ was observed. cr It will not exceed the minimum voltage limit U of the wind turbine generator set during normal operation of the wind-fire bundled power transmission system. LVRT The wind turbine terminal voltage U of the wind-fire bundled power transmission system is... W The voltage will not be lower than the minimum voltage limit U of the wind turbine generator set during normal operation of the wind-fired power transmission system. LVRT In this way, the wind turbine units in the wind-fire bundled power transmission system will not experience continuous low voltage ride-through.

[0237] If the minimum voltage limit U of the wind turbine unit in the wind-fire bundled power supply system is normally operating... LVRT The maximum value of the synchronous machine power angle swing δ of the wind and fire bundling and delivery system crthe minimum voltage limit of the wind turbine in normal operation of the wind-thermal bundled sending-out system U LVRT the maximum synchronous power angle swing of the wind-thermal bundled sending-out system δ cr the maximum synchronous power angle swing of the synchronous machine in the fault recovery process of the wind-thermal bundled sending-out system δ cr more than once the minimum voltage limit of the wind turbine in normal operation of the wind-thermal bundled sending-out system U LVRT the port voltage of the wind turbine of the wind-thermal bundled sending-out system U W more than once the minimum voltage limit of the wind turbine in normal operation of the wind-thermal bundled sending-out system U LVRT the wind turbine of the wind-thermal bundled sending-out system will appear continuous low voltage ride through phenomenon.

[0238] For example,

[0239] For the wind-thermal bundled sending-out system framework shown in FIG. 1, for example, certain wind-thermal bundled sending-out system parameter settings are shown in Table 2: Figure 2

[0240] Table 2 wind-thermal bundled sending-out system parameter values

[0241] Parameter Value Parameter Value Synchronous machine capacity S G ]]> 2756 MVA Transformer T1 ratio 27 kV / 550 kV Synchronous machine internal impedance X d ']]> 0.275 pu Transformer T2 ratio 35 kV / 550 kV Transformer T1 capacity S T1 ]]> 2880 MVA Line 1 impedance X l1 ]]> 0.018 pu Transformer T1 impedance X T1 ]] 0.15 pu Line 2 impedance X g ]]> 0.00384 pu Transformer T2 capacity S T2 ]]> 2000 MVA X l3 Parameter values 0.0039 pu Transformer T2 impedance X T2 ]]> 0.1 pu X l4 Parameter values 0.0006 pu

[0242] As can be seen from Table 2, when 7s, a three-phase short-circuit ground fault occurs at the near-bus L of a line of the line Line1 of the wind-thermal bundled sending-out system, and at 7.1s, the line is cut off, the minimum voltage limit of the wind turbine in normal operation of the wind-thermal bundled sending-out system U LVRT = 0.9pu.

[0243] Then the wind-thermal bundled sending-out system can have the following cases:

[0244] (1) Case 1: the synchronous machine output P m = 1200MW, and the wind power output P W = 1350MW.

[0245] According to the above formula, it can be calculated that at this time, the maximum synchronous power angle swing of the wind-thermal bundled sending-out system δ cr = 61.4°, δ LVRT = 48.6°, VS = δ LVRT - δ cr < 0, and the wind turbine of the wind-thermal bundled sending-out system will appear continuous low voltage ride through phenomenon in the recovery process.

[0246] In this scenario, the simulation results of the wind turbine port voltage, wind turbine output, synchronous machine power angle, and synchronous machine output of the wind-thermal bundled sending-out system are as shown in FIG. 2. Figure 5 ​As shown, in the time range from fault removal to t = 12.0s, the wind turbine of the wind-fire bundled sending-out system continuously appears low penetration phenomenon, at this time, the swing amplitude of the power angle of the synchronous machine of the wind-fire bundled sending-out system is large. With the recovery of the power angle of the synchronous machine of the wind-fire bundled sending-out system, the voltage of the wind turbine of the wind-fire bundled sending-out system is also recovered to be higher than U LVRT The wind power of the wind-fire bundled sending-out system will not enter the low voltage penetration state again, and the voltage, synchronous machine and wind power output of the wind-fire bundled sending-out system will gradually recover.

[0247] (2) Case 2: the output P m of the synchronous machine is set to be 900MW, and the output P W of the wind power is set to be 1350MW.

[0248] According to the calculation of the above formula, at this time, the maximum swing of the power angle of the synchronous machine δ cr = 48.0°, δ LVRT = 48.6°, VS = δ LVRT - δ cr > 0, and the wind power of the wind-fire bundled sending-out system will not appear continuous low voltage penetration phenomenon in the recovery process. In this scenario, the simulation results of the wind power port voltage, wind turbine output, power angle of the synchronous machine, and output of the synchronous machine of the wind-fire bundled sending-out system are as follows Figure 6 As shown by the simulation results, after the fault is removed, the wind turbine does not appear continuous low penetration, and the wind power output and the power angle of the synchronous machine gradually recover to the normal working state after the fault.

[0249] As can be seen from the above technical solutions, when the continuous low voltage penetration phenomenon of the wind turbine of the wind-fire bundled sending-out system needs to be evaluated, the method provided by the embodiments of the present application can effectively explain and illustrate the mechanism of the continuous low voltage penetration phenomenon of the wind turbine in the high output of the wind turbine and the low output of the synchronous machine of the wind-fire bundled sending-out system, and determine the stability margin evaluation index of the continuous low voltage penetration phenomenon of the wind turbine, so as to complete the quantitative evaluation of the stability margin of the continuous low voltage penetration of the wind turbine, which is helpful to understand the fault reason and processing mode of the continuous low voltage penetration phenomenon of the wind turbine in the high output of the wind turbine and the low output of the synchronous machine of the wind-fire bundled sending-out system.

[0250] The stability margin evaluation device of the continuous low voltage penetration of the wind turbine provided by the embodiments of the present application is described below, and the stability margin evaluation device of the continuous low voltage penetration of the wind turbine described below can be correspondingly referred to the stability margin evaluation method of the continuous low voltage penetration of the wind turbine described above.

[0251] Referring to Figure 7 , Figure 7A structural schematic diagram of a stability margin evaluation device for continuous low voltage ride through of a wind turbine generator set disclosed in an embodiment of the present application.

[0252] As shown in the drawings, the stability margin evaluation device for continuous low voltage ride through of the wind turbine generator set can comprise: Figure 7

[0253] An analysis unit 101 is configured to analyze output information of the wind turbine generator set and output information of the synchronous generator set of the wind-thermal bundled sending-out system by using a preset equivalent model of the wind-thermal bundled sending-out system.

[0254] An evaluation unit 102 is configured to evaluate the stability margin of the continuous low voltage ride through of the wind turbine generator set of the wind-thermal bundled sending-out system by using a preset evaluation index based on the output information of the synchronous generator set and the output information of the wind turbine generator set of the wind-thermal bundled sending-out system.

[0255] As can be seen from the above technical solutions, the stability margin of the continuous low voltage ride through of the wind turbine generator set of the wind-thermal bundled sending-out system is related to the output of the synchronous generator set and the output of the wind turbine generator set, and therefore, when the stability margin of the continuous low voltage ride through of the wind turbine generator set of the wind-thermal bundled sending-out system needs to be evaluated, the device provided in the embodiment of the present application can analyze the output information of the wind turbine generator set and the output information of the synchronous generator set by using a preset equivalent model of the wind-thermal bundled sending-out system. The preset equivalent model of the wind-thermal bundled sending-out system is created according to each node of the wind-thermal bundled sending-out system, and therefore, the output information of the wind turbine generator set and the output information of the synchronous generator set can be effectively determined by using the equivalent model of the wind-thermal bundled sending-out system, so that the stability margin of the continuous low voltage ride through of the wind turbine generator set of the wind-thermal bundled sending-out system can be evaluated based on the output information of the synchronous generator set and the output information of the wind turbine generator set and by using a preset evaluation index.

[0256] As can be seen from the above description, the device provided in the embodiment of the present application can effectively explain and describe the mechanism of the continuous low voltage ride through of the wind turbine generator set under the scenario of high output of the wind turbine generator set and low output of the synchronous generator set in the wind-thermal bundled sending-out system, and determine the stability margin evaluation index of the continuous low voltage ride through of the wind turbine generator set, so as to complete the quantitative evaluation of the stability margin of the continuous low voltage ride through of the wind turbine generator set by using the evaluation index, which is helpful to understand the failure cause and processing mode of the continuous low voltage ride through of the wind turbine generator set under the scenario of high output of the wind turbine generator set and low output of the synchronous generator set in the wind-thermal bundled sending-out system.

[0257] ​The specific processing procedure of each unit included in the stability margin evaluation device for continuous low voltage ride through of the wind turbine can refer to the related description in the stability margin evaluation method for continuous low voltage ride through of the wind turbine, and will not be described here.

[0258] The stability margin evaluation device for continuous low voltage ride through of the wind turbine provided in the embodiments of the present application can be applied to a stability margin evaluation device for continuous low voltage ride through of the wind turbine, such as a terminal, a mobile phone, a computer, and the like. Optionally, Figure 8 The hardware structure block diagram of the stability margin evaluation device for continuous low voltage ride through of the wind turbine is shown, and the hardware structure of the stability margin evaluation device for continuous low voltage ride through of the wind turbine can include at least one processor 1, at least one communication interface 2, at least one memory 3, and at least one communication bus 4. Figure 8

[0259] In the embodiments of the present application, the number of the processor 1, the communication interface 2, the memory 3, and the communication bus 4 is at least one, and the processor 1, the communication interface 2, and the memory 3 complete the communication with each other through the communication bus 4.

[0260] The processor 1 can be a central processing unit CPU, or a specific integrated circuit ASIC (Application Specific Integrated Circuit), or one or more integrated circuits configured to implement the embodiments of the present application, etc.

[0261] The memory 3 can include a high-speed RAM memory, and can also include a non-volatile memory, such as at least one disk memory.

[0262] The memory stores a program, and the processor can call the program stored in the memory, and the program is used to implement each processing procedure in the aforementioned terminal stability margin evaluation scheme for continuous low voltage ride through of the wind turbine.

[0263] The embodiments of the present application also provide a readable storage medium, which can store a program suitable for the processor to execute, and the program is used to implement each processing procedure in the aforementioned terminal stability margin evaluation scheme for continuous low voltage ride through of the wind turbine.

[0264] ​Finally, it should be noted that the terms "first", "second", and the like, herein do not denote any order, quantity, combination, or importance, but rather are used to distinguish one element from another, and are not intended to denote the presence of any such actual relationship or order. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the presence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0265] The various embodiments in the specification are described with progression in this order of description. Embodiments of each order of description can be combined with embodiments of the other orders of description.

[0266] The above description of disclosed embodiments is intended to be illustrative, and not restrictive. Many embodiments will be apparent to those of skill in the art upon reading the above description. The scope of the application should, therefore, be determined not with reference to the above description, but instead with reference to the appended claims, along with their full scope of equivalents. Various modifications to these embodiments can be made by those skilled in the art without departing from the scope of the application as defined by the appended claims. Each feature disclosed in this specification, and / or the claims, can be provided independently of all other disclosed features. The disclosure covers each independent disclosure. The disclosure encompasses all possible combinations between such features. The application can be implemented by means of both hardware and software, but implementation by software is preferred. Various features and steps are described which can be implemented in software. The disclosure covers combinations of means of both software and hardware.

Claims

1. A method for evaluating the stability margin of a wind turbine continuous low voltage ride through, characterized in that, The application relates to a wind-fire-bundling sending-out system equivalent model, a wind-fire-bundling sending-out system stability margin evaluation method and a wind-fire-bundling sending-out system stability margin evaluation device. The wind-fire-bundling sending-out system equivalent model comprises the following steps: The output information of a wind turbine and the output information of a synchronous unit of the wind-fire-bundling sending-out system are analyzed by using the preset wind-fire-bundling sending-out system equivalent model; The stability margin of continuous low-voltage penetration of the wind turbine of the wind-fire-bundling sending-out system is evaluated by using a preset evaluation index based on the output information of the synchronous unit and the output information of the wind turbine of the wind-fire-bundling sending-out system; The preset evaluation index is set as the difference between the minimum voltage limit value of the wind turbine of the wind-fire-bundling sending-out system in a fault recovery process and the maximum swing value of the power angle of the synchronous unit of the wind-fire-bundling sending-out system when the wind turbine normally operates; The maximum swing value of the power angle of the synchronous unit of the wind-fire-bundling sending-out system is determined according to the power angle characteristic curve of the synchronous unit and the active power output of the synchronous unit.

2. The method of claim 1, wherein, The preset wind-fire-bundling sending-out system equivalent model creation process comprises the following steps: The dynamic characteristics of the wind turbine of the wind-fire-bundling sending-out system are simulated by using a controlled current source; The thermal power unit of the wind-fire-bundling sending-out system is equivalent to a voltage source containing internal impedance; The excitation dynamic process of the thermal power unit of the wind-fire-bundling sending-out system is ignored; The resistance and susceptance in the power transmission line of the wind-fire-bundling sending-out system are ignored; The receiving end network connected to the wind-fire-bundling sending-out system is replaced by an infinite power source, so that the wind-fire-bundling sending-out system equivalent model is obtained as the wind-fire-bundling sending-out system equivalent model.

3. The method of claim 2, wherein, The node equation of the preset wind-fire-bundling sending-out system equivalent model comprises the following steps: ； The stability margin of continuous low-voltage penetration of the wind turbine of the wind-fire-bundling sending-out system is evaluated by using a preset evaluation index based on the output information of the synchronous unit and the output information of the wind turbine of the wind-fire-bundling sending-out system; represents the internal potential of the synchronous machine of the wind-fire baling and feeding system; represents an infinite bus voltage magnitude; represents the bus voltage of the wind and thermal bundled delivery system; represents the wind power port voltage of the wind-fire bundled delivery system; represents the infinite bus node injection current; represents the injection current of the collection bus of the wind and thermal bundled sending-out system; representing the synchronous machine node of the wind-fire bundled delivery system injecting current; represents the wind power node injection current of the wind-fire bundled delivery system; This represents the self-admittance of the node of the infinite power supply bus. represents the mutual admittance between the infinite bus node and the wind-thermal bundled delivery system collection bus node; represents the mutual admittance between the infinite bus node and the synchronous machine node of the wind-thermal bundled delivery system; represents the mutual admittance between the infinite bus node and the wind port node of the wind-thermal bundled delivery system; represents mutual admittance between the infinite bus node and the wind-thermal bundled sending system collecting bus node, wherein, = 1 - jωC ; Y represents the self-admittance of the wind and fire bundled delivery system collection bus node; represents mutual admittance between the wind-thermal bundled sending system collecting bus node and the synchronous machine node of the wind-thermal bundled sending system; represents mutual admittance between the wind-thermal bundled delivery system aggregated bus node and the wind-thermal bundled delivery system wind port node; represents mutual admittance between the infinite bus node and the synchronous machine node of the wind-thermal bundled delivery system, wherein, = 1 - jωT ; represents mutual admittance between the wind-thermal bundled sending system collecting bus node and the synchronous machine node of the wind-thermal bundled sending system, wherein, = -jωC1 ; representing the self-impedance of the synchronous machine node of the wind-fire baling and feeding system; representing mutual admittance between a synchronous machine node of the wind-thermal bundled delivery system and a wind power port node of the wind-thermal bundled delivery system; represents mutual admittance between the infinite bus node and the wind power port node of the wind-thermal bundled delivery system, wherein, = 1 - jωC ; represents mutual admittance between the wind-fire bundled sending system collection bus node and the wind power port node, wherein, = 1 + jωC1 ; representing mutual admittance between a synchronous machine node of the wind-thermal bundled delivery system and a wind power port node of the wind-thermal bundled delivery system, wherein, = 0 ; represents the self-admittance of the wind port node of the wind-fire bundled delivery system.

4. The method of claim 1, wherein, If the difference between the minimum voltage limit value of the wind turbine of the wind-fire-bundling sending-out system in a fault recovery process and the maximum swing value of the power angle of the synchronous unit of the wind-fire-bundling sending-out system when the wind turbine normally operates is greater than zero, the minimum voltage limit value of the wind turbine of the wind-fire-bundling sending-out system when the wind turbine normally operates is greater than the maximum swing value of the power angle of the synchronous unit of the wind-fire-bundling sending-out system, the maximum swing value of the power angle of the synchronous unit of the wind-fire-bundling sending-out system in the fault recovery process will not exceed the minimum voltage limit value of the wind turbine of the wind-fire-bundling sending-out system when the wind turbine normally operates, the port voltage of the wind turbine of the wind-fire-bundling sending-out system will not be lower than the minimum voltage limit value of the wind turbine of the wind-fire-bundling sending-out system when the wind turbine normally operates, and the wind turbine of the wind-fire-bundling sending-out system will not appear continuous low-voltage penetration phenomenon. ​ If the difference between the minimum voltage limit value of the wind turbine in normal operation of the wind-thermal bundled sending-out system and the maximum synchronous machine power angle swing value of the wind-thermal bundled sending-out system is less than zero, the minimum voltage limit value of the wind turbine in normal operation of the wind-thermal bundled sending-out system is less than the maximum synchronous machine power angle swing value of the wind-thermal bundled sending-out system, the maximum synchronous machine power angle swing value of the wind-thermal bundled sending-out system appears more than once during the fault recovery process of the wind-thermal bundled sending-out system, the port voltage of the wind turbine of the wind-thermal bundled sending-out system appears more than once below the minimum voltage limit value of the wind turbine in normal operation of the wind-thermal bundled sending-out system, and the wind turbine of the wind-thermal bundled sending-out system appears continuous low voltage ride through phenomenon.

5. The method of claim 1, wherein, The calculation formula of the synchronous machine power angle characteristic curve of the wind-thermal bundled sending-out system comprises: ； wherein, Pwind represents the output power of the wind turbine; Pfire represents the output power of the gas turbine; and Pbind represents the output power of the wind-fire bundled system. represents the internal potential of the synchronous machine of the wind-fire baling and feeding system; represents an infinite bus voltage magnitude; Line1 represents the line impedance in the equivalent model of the wind-fire bundled delivery system; , ZLine2= ZLine2+ Zsynchronous machine transformer internal impedance + Zsynchronous machine transient reactance ZLine2= ZLine2+ Zsynchronous machine transformer internal impedance + Zsynchronous machine transient reactance ZLine2= ZLine2+ Zsynchronous machine transformer internal impedance + Zsynchronous machine transient reactance ZLine2= ZLine2+ Zsynchronous machine transformer internal impedance + Zsynchronous machine transient reactance a power angle of a synchronous machine representing the wind and fire bundled delivery system; , Z1 / (Z1+ Z2) represents the ratio between the line Line1 impedance in the equivalent model of the wind-fire baling and feeding system and the sum of the line Line1 impedance and the line Line2 impedance. Pw represents the wind power active output of the wind-fire bundled delivery system; represents the wind power port voltage amplitude of the wind-fire bundled delivery system; wherein, ； wherein, ； wherein, Vd represents the d-axis component of the grid-side converter voltage of the wind-fire bundled sending-out system; represents the d-axis component of the grid-side converter voltage of the wind-fire bundled sending-out system; , represents the ratio between the line Line2 impedance in the equivalent model of the wind-fire baling and sending-out system and the sum of the line Line1 impedance and the line Line2 impedance. , represents and , wherein, represents the sum of the internal impedance of the transformer T2 connected to the wind power and the impedance of the line Line3 and the impedance of the line Line4 in the equivalent model of the wind-fire bundled delivery system; ; represents the wind power output current amplitude of the wind-fire bundled delivery system; representing a phase angle of a wind power port of the wind-fire bundle sending-out system; wherein, ； wherein, 。 6. The method of claim 5, wherein, The determination process of the maximum synchronous machine power angle swing value of the wind-thermal bundled sending-out system comprises: determining the synchronous machine power angle characteristic curve and the active power output of the synchronous machine of the wind-thermal bundled sending-out system; determining the maximum synchronous machine power angle swing value of the wind-thermal bundled sending-out system by the equal-area rule according to the synchronous machine power angle characteristic curve and the active power output of the synchronous machine of the wind-thermal bundled sending-out system.

7. A device for evaluating stability margin of continuous low voltage ride through of a wind turbine generator unit, characterized by, comprise: an analysis unit configured to analyze the output information of the wind turbine and the output information of the synchronous machine group of the wind-thermal bundled sending-out system by using a preset equivalent model of the wind-thermal bundled sending-out system; an evaluation unit configured to evaluate the stability margin of the continuous low voltage ride through of the wind turbine of the wind-thermal bundled sending-out system by using a preset evaluation index based on the output information of the wind turbine and the output information of the synchronous machine group of the wind-thermal bundled sending-out system; the preset evaluation index is set as the difference between the minimum voltage limit value of the wind turbine in normal operation of the wind-thermal bundled sending-out system and the maximum synchronous machine power angle swing value of the wind-thermal bundled sending-out system during the fault recovery process of the wind-thermal bundled sending-out system; wherein, the maximum synchronous machine power angle swing value of the wind-thermal bundled sending-out system is determined according to the synchronous machine power angle characteristic curve and the active power output of the synchronous machine of the wind-thermal bundled sending-out system.

8. A device for assessing the stability margin of a wind turbine continuous low voltage ride through, characterized by comprise: one or more processors, and a memory; the memory stores computer readable instructions, and the computer readable instructions are executed by the one or more processors to realize the steps of the stability margin evaluation method of the continuous low voltage ride through of the wind turbine according to any one of claims 1 to 6.

9. A readable storage medium characterized by: the readable storage medium stores computer readable instructions, and the computer readable instructions are executed by one or more processors to make the one or more processors realize the steps of the stability margin evaluation method of the continuous low voltage ride through of the wind turbine according to any one of claims 1 to 6.

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