Transient stability control method and apparatus for wind-thermal-bundled system

Abstract

A transient stability control method and apparatus for a wind-thermal-bundled system. The method comprises: acquiring in real time terminal voltage of a doubly-fed induction generator when the wind-thermal-bundled system experiences a fault (S1); in response to the terminal voltage of the doubly-fed induction generator being within a first voltage sag interval, increasing a reactive current injection coefficient of the doubly-fed induction generator on the basis of a preset adjustment rule, to reduce the swing amplitude of a synchronous generator during an acceleration phase under fault conditions (S2); in response to the terminal voltage of the doubly-fed induction generator being within a second voltage sag interval, increasing the reactive current injection coefficient of the doubly-fed induction generator on the basis of the adjustment rule, to reduce the swing amplitude of the synchronous generator during the acceleration phase and the swing amplitude thereof during a deceleration phase under fault conditions (S3); and in response to the terminal voltage of the doubly-fed induction generator being within a third voltage sag interval, decreasing the reactive current injection coefficient of the doubly-fed induction generator on the basis of the adjustment rule, to reduce the swing amplitude of the synchronous generator during the deceleration phase under fault conditions (S4).

Description

Transient stability control method and device for wind-fire bundling system

[0001] The present application claims priority to the Chinese patent application No. 202411033542.9, filed on July 30, 2024, with the Chinese Patent Office, the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the technical field of wind-fire bundling system, for example, to a transient stability control method and device for wind-fire bundling system. BACKGROUND

[0003] In recent years, with the large-scale development of wind power generation, doubly-fed wind turbines gradually become a supplement to synchronous machines and become an important power generation unit on the power generation side of the power system. However, the physical structure and working principle of the doubly-fed wind turbine are obviously different from those of the traditional synchronous machine, and its transient characteristics are more complex and flexible, which leads to significant changes in the transient behavior of the wind power grid-connected system and may cause new transient stability problems.

[0004] At present, the research on the transient problems of the doubly-fed wind turbine grid-connected power system is mostly based on numerical simulation methods to study the transient stability of specific power systems. The numerical simulation method can consider the complex transient model of the doubly-fed wind turbine with normal control, transient control, hardware protection and other links, and can restore and intuitively reflect the transient process of each variable in each complex system as much as possible, but there is still a gap in the influence of transient control parameters (such as reactive current injection coefficient) on the transient stability of the system.

[0005] Specifically, for example, the conventional method obtains the fault analysis parameters of the wind farm, calculates the voltage division parameters of the grid-connected point of the wind farm, creates a reactive power injection proportion coefficient test array and a grid-connected point voltage test array, calculates the reactive power / current and terminal voltage of the wind farm, determines the output active power of each test value in the reactive power injection proportion coefficient test array, and determines the reactive power injection proportion coefficient test value corresponding to the maximum output active power as the optimization parameter for the wind farm fault ride-through. The purpose of this method is to improve the transient stability of the wind farm after fault recovery, but it cannot improve the transient stability during and after the fault recovery of the system, and this method requires a large amount of data calculation and processing, the control effect is not good, the control efficiency is not high and the practicality is low. SUMMARY

[0006] The embodiments of the present application provide a transient stability control method and device for wind-fire bundling system, which improves the efficiency and practicality of the transient stability control of the wind-fire bundling system.

[0007] The embodiments of the present application provide a transient stability control method for wind-fire bundling system, which comprises:

[0008] Real-time acquisition of the terminal voltage of the doubly-fed wind turbine during the fault of the wind-thermal bundled system;

[0009] In response to the terminal voltage of the doubly-fed wind turbine being in the first voltage drop interval, the reactive current injection coefficient of the doubly-fed wind turbine is increased according to a preset adjustment rule, so as to reduce the swing of the acceleration stage of the synchronous generator during the fault;

[0010] In response to the terminal voltage of the doubly-fed wind turbine being in the second voltage drop interval, the reactive current injection coefficient of the doubly-fed wind turbine is increased according to the adjustment rule, so as to reduce the swing of the acceleration stage of the synchronous generator and the swing of the deceleration stage of the synchronous generator during the fault;

[0011] In response to the terminal voltage of the doubly-fed wind turbine being in the third voltage drop interval, the reactive current injection coefficient of the doubly-fed wind turbine is reduced according to the adjustment rule, so as to reduce the swing of the deceleration stage of the synchronous generator during the fault.

[0012] In an embodiment, the first voltage drop interval is less than a first critical value; the second voltage drop interval is greater than a second critical value and less than a preset upper voltage limit value; and the third voltage drop interval is greater than the first critical value and less than the second critical value.

[0013] In an embodiment, the method further comprises:

[0014] Acquiring the historical terminal voltage and the historical reactive current injection coefficient of the doubly-fed wind turbine during the fault of the wind-thermal bundled system, and determining the reactive injection current value according to the historical terminal voltage and the historical reactive current injection coefficient;

[0015] Obtaining the reactive current value according to the preset maximum capacity of the converter and the reactive injection current value;

[0016] Determining the first critical value according to the maximum capacity of the converter, the reactive injection current value and the reactive current value.

[0017] In an embodiment, the method further comprises:

[0018] Acquiring the historical terminal voltage of the doubly-fed wind turbine during the fault of the wind-thermal bundled system, and determining the amplitude limiting value of the low-voltage active limiting logic according to the historical terminal voltage;

[0019] Obtaining the active current value according to the preset maximum capacity of the converter and the amplitude limiting value of the low-voltage active limiting logic;

[0020] Determining the second critical value according to the maximum capacity of the converter, the amplitude limiting value of the low-voltage active limiting logic and the active current value.

[0021] The embodiments of the application also provide a wind-thermal bundled system transient stability control device, which comprises:

[0022] terminal voltage module, configured to obtain terminal voltage of the doubly-fed wind turbine in real time when the wind-thermal bundled system fails;

[0023] the first voltage drop interval module is configured to increase the reactive current injection coefficient of the doubly-fed wind turbine according to a preset adjustment rule to reduce the swing of the acceleration stage of the synchronous generator during the failure, in response to the terminal voltage of the doubly-fed wind turbine being in the first voltage drop interval;

[0024] the second voltage drop interval module is configured to increase the reactive current injection coefficient of the doubly-fed wind turbine according to the adjustment rule to reduce the swing of the acceleration stage of the synchronous generator and the swing of the deceleration stage of the synchronous generator during the failure, in response to the terminal voltage of the doubly-fed wind turbine being in the second voltage drop interval;

[0025] the third voltage drop interval module is configured to decrease the reactive current injection coefficient of the doubly-fed wind turbine according to the adjustment rule to reduce the swing of the deceleration stage of the synchronous generator during the failure, in response to the terminal voltage of the doubly-fed wind turbine being in the third voltage drop interval.

[0026] In an embodiment, the first voltage drop interval is less than a first critical value; the second voltage drop interval is greater than a second critical value and less than a preset upper voltage limit value; and the third voltage drop interval is greater than the first critical value and less than the second critical value.

[0027] In an embodiment, the device further comprises:

[0028] the reactive injection module is configured to obtain historical terminal voltage and historical reactive current injection coefficient of the doubly-fed wind turbine when the wind-thermal bundled system fails, and determine a reactive injection current value according to the historical terminal voltage and the historical reactive current injection coefficient;

[0029] the reactive current value module is configured to obtain a reactive current value according to a preset maximum capacity of the converter and the reactive injection current value;

[0030] the first critical value module is configured to determine a first critical value according to the maximum capacity of the converter, the reactive injection current value and the reactive current value.

[0031] In an embodiment, the device further comprises:

[0032] the amplitude limiting value module is configured to obtain historical terminal voltage of the doubly-fed wind turbine when the wind-thermal bundled system fails, and determine an amplitude limiting value of low-voltage active limiting logic according to the historical terminal voltage;

[0033] the active current value module is configured to obtain an active current value according to a preset maximum capacity of the converter and the amplitude limiting value of the low-voltage active limiting logic;

[0034] the second critical value module is configured to determine a second critical value according to the maximum capacity of the converter, the amplitude limiting value of the low-voltage active limiting logic and the active current value.

[0035] The application further provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the above method when executing the program.

[0036] The application further provides a computer readable storage medium, which stores a computer program for executing the above method by a computer.

[0037] The application further provides a computer program product, which comprises computer programs / instructions, and the computer programs / instructions implement the steps of the above method when executed by a processor. BRIEF DESCRIPTION OF DRAWINGS

[0038] Fig. 1 is a flow chart of a transient stability control method of a wind-thermal bundled system according to an embodiment of the application;

[0039] Fig. 2 is a flow chart of determining a first critical value according to an embodiment of the application;

[0040] Fig. 3 is a flow chart of determining a second critical value according to an embodiment of the application;

[0041] Fig. 4 is a schematic diagram of a rotor converter transient current instruction control according to an embodiment of the application;

[0042] Fig. 5A and Fig. 5B are schematic diagrams of the relationship between active / reactive current and terminal voltage of a doubly-fed wind turbine during a fault according to an embodiment of the application;

[0043] Fig. 6 is a topology diagram of a wind-thermal bundled system according to an embodiment of the application;

[0044] Fig. 7 is a schematic diagram of terminal voltage of a doubly-fed wind turbine under different reactive current injection coefficients of 50% of a wind power connected at fault position 2 according to an embodiment of the application;

[0045] Fig. 8A-8C are schematic diagrams of power angle variation of a synchronous unit under different reactive current injection coefficients of a metal ground at fault position 1 according to an embodiment of the application;

[0046] Fig. 9A-9C are schematic diagrams of power angle variation of a synchronous unit under different reactive current injection coefficients of a metal ground at fault position 2 according to an embodiment of the application;

[0047] Fig. 10A-10C are schematic diagrams of terminal voltage of a doubly-fed wind turbine, active current and power angle variation of a synchronous unit under different reactive current injection coefficients of a metal ground at fault position 1 according to an embodiment of the application;

[0048] Fig. 11A-11C are schematic diagrams of terminal voltage of a doubly-fed wind turbine, active current and power angle variation of a synchronous unit under different reactive current injection coefficients of a metal ground at fault position 2 according to an embodiment of the application;

[0049] FIGS. 12A-12C are schematic diagrams of the terminal voltage of the doubly-fed wind turbine, active current and power angle variation of the synchronous unit under different reactive current injection coefficients of the non-metallic ground fault position 1 in the embodiment of the present application;

[0050] FIG. 13 is a schematic diagram of the structure of the transient stability control device of the wind-fire bundled system in an embodiment of the present application;

[0051] FIG. 14 is a schematic diagram of the structure of the transient stability control device of the wind-fire bundled system in another embodiment of the present application;

[0052] FIG. 15 is a schematic diagram of the structure of the transient stability control device of the wind-fire bundled system in still another embodiment of the present application;

[0053] FIG. 16 is a schematic diagram of the structure of the electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0054] The embodiment of the present application provides a wind-fire bundled system transient stability control method and device.

[0055] The embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application, and the described embodiments are part of the embodiments of the present application, rather than all the embodiments.

[0056] As shown in FIG. 1, it is a flow chart of the wind-fire bundled system transient stability control method in an embodiment of the present application, and the execution subject of the wind-fire bundled system transient stability control method provided in the embodiment of the present application includes a computer. The present application determines the influence law of the reactive current injection coefficient on the transient stability of the wind-fire bundled system, and performs fast and effective transient stability control on the wind-fire bundled system with the reactive current injection coefficient of the doubly-fed wind turbine, thereby improving the wind-fire bundled system transient stability control effect, improving the control efficiency and practicality, and providing a basis for the adjustment of the transient control parameters of the doubly-fed wind turbine. The method shown in the figure includes:

[0057] In step S1, the terminal voltage of the doubly-fed wind turbine during the fault of the wind-fire bundled system is acquired in real time;

[0058] In step S2, in response to that the terminal voltage of the doubly-fed wind turbine is in the first voltage drop interval, the reactive current injection coefficient of the doubly-fed wind turbine is increased according to the preset adjustment rule, so as to reduce the swing of the acceleration stage of the synchronous generator during the fault;

[0059] In step S3, in response to that the terminal voltage of the doubly-fed wind turbine is in the second voltage drop interval, the reactive current injection coefficient of the doubly-fed wind turbine is increased according to the adjustment rule, so as to reduce the swing of the acceleration stage of the synchronous generator and the swing of the deceleration stage of the synchronous generator during the fault;

[0060] Step S4, in response to the doubly-fed wind turbine terminal voltage being in the third voltage drop interval, the doubly-fed wind turbine reactive current injection coefficient is reduced according to the adjustment rule, so as to reduce the swing of the synchronous generator deceleration stage during the fault.

[0061] wherein the reactive current injection coefficient is a proportional parameter of the doubly-fed wind turbine injecting reactive current into the power grid according to the grid voltage drop degree. During the fault of the wind-fire bundled system, the active current and the reactive current of the doubly-fed wind turbine in the wind-fire bundled system change with the change of the terminal voltage of the doubly-fed wind turbine. Specifically, according to the different dominant transient control links of the active current and the reactive current, the terminal voltage drop degree can be divided into three cases.

[0062] In some embodiments, when the terminal voltage of the doubly-fed wind turbine is in the second voltage drop interval, the reactive current is dominated by the reactive proportional injection link and increases with the decrease of the terminal voltage, the active current is dominated by the low voltage active power limiting logic (LVPL) limiting link and decreases with the decrease of the terminal voltage, and the converter still has a margin.

[0063] In some embodiments, when the terminal voltage of the doubly-fed wind turbine is in the third voltage drop interval, the reactive current is still dominated by the reactive proportional injection link, but the active current is limited by the reactive current and the maximum capacity and decreases with the decrease of the terminal voltage. When the terminal voltage of the doubly-fed wind turbine is in the first voltage drop interval, the reactive current reaches the maximum capacity of the converter and no longer changes with the decrease of the terminal voltage, and the active current is 0.

[0064] wherein in different voltage drop intervals, the doubly-fed wind turbine reactive current injection coefficient is adjusted differently, so as to realize accurate control of the transient stability of the wind-fire bundled system during the fault. In some embodiments, the preset adjustment rule can be set according to the actual working condition, for example, the value of the doubly-fed wind turbine reactive current injection coefficient is increased each time, the value of the doubly-fed wind turbine reactive current injection coefficient is decreased each time, the number of adjustments, etc.

[0065] In some embodiments, when the first swing of the synchronous generator in the wind-fire bundled system is concerned (the synchronous generator acceleration stage during the fault), it can be seen through the analysis of the relevant historical data that the first swing of the synchronous generator decreases and the transient stability of the wind-fire bundled system is enhanced with the increase of the doubly-fed wind turbine reactive current injection coefficient. In addition, when the second swing of the synchronous generator in the wind-fire bundled system is concerned (the synchronous generator deceleration stage during the fault clearance), the initial value of the active current ramping during the fault recovery needs to be considered, and thus the initial value of the active current ramping changes differently with the change of the doubly-fed wind turbine reactive current injection coefficient for different voltage drop intervals, i.e., the first, second and third voltage drop intervals.

[0066] For example, in the first voltage drop interval, the active current starts to ramp up from 0 in the initial stage of fault recovery, and the initial value of the active current ramping up does not change with the DFIG reactive current injection coefficient, and is 0. The DFIG reactive current injection coefficient has little effect on the transient stability of the wind-thermal bundled system. In the second voltage drop interval, as the DFIG reactive current injection coefficient increases, the swing amplitude of the second swing decreases, which is beneficial to the transient stability of the wind-thermal bundled system. In the third voltage drop interval, the swing amplitude of the second swing decreases as the DFIG reactive current injection coefficient increases, but when the DFIG reactive current injection coefficient increases to a value (generally 5) or above, the swing amplitude of the second swing actually increases as the DFIG reactive current injection coefficient increases, which is not conducive to the transient stability of the wind-thermal bundled system.

[0067] Therefore, when the DFIG reactive current injection coefficient is used to control the transient stability of the wind-thermal bundled system, the swing amplitude of the second swing needs to be mainly concerned. This is because the swing amplitude of the first swing decreases as the DFIG reactive current injection coefficient increases, so when the DFIG reactive current injection coefficient is controlled to decrease, it needs to be decreased as slowly as possible, so as to ensure that the swing amplitude of the first swing does not increase significantly while the swing amplitude of the second swing is decreased.

[0068] In some embodiments, in the first and second voltage drop intervals, the DFIG reactive current injection coefficient is increased to improve the transient stability of the wind-thermal bundled system, and as the DFIG reactive current injection coefficient increases, the swing amplitude of the first swing also decreases. Therefore, when setting the adjustment rule, the value of the DFIG reactive current injection coefficient that is increased each time can be set to 0.5 or 1, which can significantly improve the efficiency of the transient stability control of the wind-thermal bundled system. In addition, the value of the DFIG reactive current injection coefficient that is increased each time can be set according to actual conditions.

[0069] In some embodiments, as the DFIG reactive current injection coefficient decreases, the swing amplitude of the first swing increases, so in the third voltage drop interval, the value of the DFIG reactive current injection coefficient that is decreased in the adjustment rule is less than the value that is increased. For example, the value that is decreased each time is 0.2, so as to appropriately decrease the DFIG reactive current injection coefficient, ensure that the swing amplitude of the first swing is not too large, and decrease the swing amplitude of the second swing, thereby improving the transient stability of the wind-thermal bundled system.

[0070] In some embodiments, the first voltage drop interval is less than a first critical value; the second voltage drop interval is greater than a second critical value and less than a preset upper voltage limit value; and the third voltage drop interval is greater than the first critical value and less than the second critical value.

[0071] When setting the first, second, and third voltage drop intervals, the upper and lower limits of each interval need to be determined. For example, the first critical value U t1U1 is a preset upper limit value of the second voltage drop interval. The upper limit value of voltage can be adjusted and set according to actual working conditions. t2 U1 is a preset upper limit value of the second voltage drop interval. The upper limit value of voltage can be adjusted and set according to actual working conditions.

[0072] In the embodiment, as shown in FIG. 2, the method further comprises:

[0073] In step S21, the historical terminal voltage and the historical reactive current injection coefficient of the doubly-fed wind turbine when the wind-thermal bundling system fails are obtained, and the reactive injection current value is determined according to the historical terminal voltage and the historical reactive current injection coefficient;

[0074] In step S22, the reactive current value is obtained according to the preset maximum capacity of the converter and the reactive injection current value.

[0075] In step S23, the first critical value is determined according to the maximum capacity of the converter, the reactive injection current value and the reactive current value.

[0076] In some embodiments, the demarcation values of each voltage drop interval can be determined according to historical data when the wind-thermal bundling system fails. For example, as shown in FIG. 4, a rotor converter transient current instruction control diagram can be seen, in which the reactive injection current is obtained from the terminal voltage and the reactive current injection coefficient of the doubly-fed wind turbine. Thus, the reactive injection current value is determined by using the historical terminal voltage and the historical reactive current injection coefficient. In addition, the reactive current value can be obtained from the reactive injection current value and the preset maximum capacity of the converter, and the process of obtaining the reactive injection current value and the reactive current value can be performed in a conventional manner.

[0077] In some embodiments, according to different historical terminal voltage and historical reactive current injection coefficient, the determined reactive injection current value is i p rq_inj +i p rq_ctrl_10, and the reactive current value is i p rq As shown in FIG. 5A, in combination with the maximum capacity of the converter I rmax The intersection of the three lines is the first critical value U t1 .

[0078] In the embodiment, as shown in FIG. 3, the method further comprises:

[0079] In step S31, the historical terminal voltage of the doubly-fed wind turbine when the wind-thermal bundling system fails is obtained, and the amplitude limiting value of the low-voltage active limiting logic is determined according to the historical terminal voltage.

[0080] In step S32, the active current value is obtained according to the preset maximum capacity of the converter and the amplitude limiting value of the low-voltage active limiting logic.

[0081] Step S33, according to the maximum capacity of the converter, the amplitude limit value of the low-voltage active power limiting logic and the active current value, a second critical value is determined.

[0082] As shown in FIG. 4, similar to the determination method of the first critical value, the amplitude limit value of the low-voltage active power limiting logic, i.e., the LVPL amplitude, can be determined by using the historical terminal voltage of the doubly-fed wind turbine during the failure of the wind-thermal bundled system. The active current value can be determined by using the amplitude limit value of the low-voltage active power limiting logic and the preset maximum capacity of the converter. The process of determining the active current value and the amplitude limit value of the low-voltage active power limiting logic can adopt a conventional manner.

[0083] In some embodiments, according to different historical terminal voltages, the amplitude limit values of the low-voltage active power limiting logic determined are different. p rdmax2 The active current value is i p rd As shown in FIG. 5B, in combination with the maximum capacity of the converter I rmax The intersection of the three lines is the second critical value U t2 .

[0084] The present application determines the influence law of the reactive current injection coefficient on the transient stability of the wind-thermal bundled system, and performs fast and effective transient stability control on the wind-thermal bundled system of the doubly-fed wind turbine with the reactive injection coefficient of the doubly-fed wind turbine, thereby improving the transient stability control effect of the wind-thermal bundled system, enhancing the control efficiency and practicality, and providing a basis for the adjustment of the transient control parameters of the doubly-fed wind turbine.

[0085] In some embodiments, the transient control strategy of the rotor-side converter of the doubly-fed wind turbine is shown in FIG. 4. During the transient control action, all the integrators of the normal control are frozen to maintain the steady-state value before the failure. is the steady-state value before the failure, is the active current output by the normal control.

[0086] In the reactive branch, the steady-state value before the failure is is the injection current obtained by the reactive injection link After the converter capacity limitation i rmax , the actual reactive current instruction is obtained U t is the voltage amplitude at the terminal voltage, U tref is the terminal voltage reference value, k qv is the reactive injection coefficient.

[0087] In the active branch, the steady-state value before the failure is After the converter capacity limitation i and the LVPL amplitude The actual active current command is obtained after joint constraint Among them, the LVPL limiting link is based on the terminal voltage U t During the voltage dip, calculate the limited value of the active current of the doubly-fed wind turbine When U t >U1, there is no limit to the active current. When U0 < U t <U1, the limited value of the active current is linearly related to the voltage. The lower the voltage, the smaller the limited value of the active current. When U t <U0, the limited value of the active current is 0

[0088] Under transient control, the reactive current of the doubly-fed wind turbine Is composed of the pre-fault steady-state value And the reactive current injection The minimum value of the sum and the converter capacity limit i rmax Together determine Among them, the pre-fault steady-state value And the converter capacity limit i rmax Has nothing to do with the fault degree. Only the reactive current injection Is related to the terminal voltage amplitude U during the fault t And the reactive current injection coefficient k qv So, for a system with the same structure and operating conditions, the reactive current during the fault Depends on the terminal voltage U t And the reactive current injection coefficient k qv That is The active current Is composed of LVPL limiting And the converter capacity limit constraint Together constitute Among them, LVPL limiting Is related to the terminal voltage amplitude U t And the LVPL limiting curve slope k d The converter capacity limit constraint Is related to the reactive current And the reactive current Depends on the terminal voltage amplitude U t So, the active current Depends on the terminal voltage amplitude U t [[ID=**69**]]、LVPL limiting curve slope k d And the reactive current injection coefficient k qv That is[[ID=**74**]]

[0089] Among them, Figure 5A and Figure 5B respectively show F irq (U t ,k Note: There seems to be a formatting issue in the original text where "" is used at the beginning and end. Also, the "**69**" and "**74**" are added in the translation to indicate where there might be a potential error in the original text numbering or formatting. If these are not errors in the original, please adjust the translation accordingly. Also, the " " tags should be at the end of each line in the original text for proper translation.qv ) and F ird (U t , k d , k qv ) with terminal voltage U t . According to the dominant transient control link of active current and reactive current, the terminal voltage drop degree can be divided into three cases. The second voltage drop interval: U t2 < U t < U1, the reactive current is dominated by the reactive proportion injection link and increases with the decrease of terminal voltage, the active current is dominated by the LVPL limiting link and decreases with the decrease of terminal voltage, and the converter still has margin. The third voltage drop interval: U t1 < U t < U t2 , the reactive current is still dominated by the reactive proportion injection link, but the active current is limited by the reactive current and the maximum capacity and decreases with the decrease of terminal voltage. The first voltage drop interval: U t < U t1 , the reactive current reaches the maximum capacity of the converter and no longer changes with the decrease of terminal voltage, and the active current is 0.

[0090] In this embodiment, the influence of different wind power penetration and different fault on the transient stability of the system is determined by using relevant historical data.

[0091] Among them, the reactive current injection coefficient dominates the transient characteristics of the doubly-fed wind turbine during the fault. Taking the wind-fire bundled export system as the research object, the power angle of the synchronous generator set is used to reflect the transient stability of the system, the influence of the reactive current injection coefficient on the transient stability of the system is studied, and the machine interpretation is given.

[0092] In some embodiments, the topology of the wind-fire bundled system is shown in Figure 6, the doubly-fed wind turbine and the synchronous generator set are connected to the infinite grid through three double-circuit transmission lines, the capacity of the synchronous generator set is 4000MW, the doubly-fed wind turbine is connected according to different wind power penetration of 50%, 30% and 10%, and the corresponding capacity is set to 4000MW, 1714.29MW and 444.44MW. The fault is set as a three-phase ground fault, the fault duration is 0.1s, and the fault position includes: (1) Fault_1 at the busbar; (2) Fault_2, Fault_3 and Fault_4 in the middle of one circuit of the double-circuit line. In the figure, DFIG is a doubly-fed wind turbine, and SG is a synchronous generator.

[0093] Under the wind power penetration of 50%, 30% and 10% and different fault positions, the reactive current injection coefficient k qv, and the power angle waveform of the synchronous generator (reference phase is the voltage phase of the infinite source 1) is obtained, and the power angle of the synchronous generator is taken as a standard for measuring the transient stability of the system.

[0094] In the first swing amplitude, the first swing amplitude of the synchronous generator decreases with the increase of the reactive current injection coefficient k qv of the doubly-fed wind turbine, and the transient stability of the system is enhanced, as shown in FIGS. 8A-8C and 9A-9C, wherein FIGS. 8A and 9A are for a wind power access ratio of 50%, FIGS. 8B and 9B are for a wind power access ratio of 30%, and FIGS. 8C and 9C are for a wind power access ratio of 10%. This is because, with the increase of k qv , the doubly-fed wind turbine can output more reactive power during the fault, the voltage support capability is stronger, the voltage drop at the fault point is smaller (as shown in FIG. 7), the active power output of the synchronous machine is increased, the imbalance power (the difference between the input mechanical power and the output electromagnetic power) received by the synchronous machine is reduced, and the transient stability is improved.

[0095] In some embodiments, when the second swing amplitude is concerned (the synchronous generator deceleration stage after the fault is cleared), the initial value of the active current ramping during the fault recovery needs to be considered, and the following three cases are divided:

[0096] 1) During the fault, U t <U t1 As shown in FIG. 10A, the active current limiting value obtained by the LVPL is 0 (three-phase metallic ground fault occurs at the busbar). The active current starts to ramp from 0 in the initial stage of the fault recovery, as shown in FIG. 10B. At this time, the initial value of the active current ramping does not change with k qv , and is 0. k qv has little effect on the transient stability of the system. The power angle of the synchronous machine is shown in FIG. 10C.

[0097] 2) During the fault, U t2 <U t <U1, as shown in FIG. 11A is a schematic diagram of the terminal voltage of the doubly-fed wind turbine under different reactive current injection coefficients of the metal grounding at fault position 2, and as shown in FIG. 11B is a schematic diagram of the active current under different reactive current injection coefficients of the metal grounding at fault position 2. The active current limiting value has a linear relationship with the voltage, but is not limited by the capacity of the converter (three-phase metallic ground fault occurs in the middle of one of the two lines of the double-circuit line). At this time, the larger k qv , the stronger the voltage support capability, the higher the terminal voltage of the doubly-fed wind turbine, the larger the active current limiting value obtained by the LVPL, and the larger the initial value of the active current ramping in the initial stage of the fault recovery, and the easier the recovery. As shown in FIG. 11C is a schematic diagram of the power angle change of the synchronous generator under different reactive current injection coefficients of the metal grounding at fault position 2. It can be seen that, with the increase of k qvThe swing of the second pendulum is reduced, which is beneficial to the transient stability of the system.

[0098] 3) During the fault t1 <U t <U t2 As shown in FIG. 12A, it is a schematic diagram of terminal voltage under different reactive current injection coefficients of non-metallic ground fault at fault position 1, which is limited by the converter capacity (three-phase non-metallic ground fault occurs at the busbar).

[0099] wherein, when k qv When the active current limiting value is reduced to a certain extent or even becomes 0 due to the converter capacity limitation, the active current ramping initial value is reduced or even becomes 0. As shown in FIG. 12B, it is a schematic diagram of active current under different reactive current injection coefficients of non-metallic ground fault at fault position 1. Because the ramping initial value is reduced or even becomes 0, although the ramping coefficient is the same, the starting point is lower, so the recovery after the fault is slow, the swing of the second pendulum is large, which is not conducive to the transient stability of the system. As shown in FIG. 12C, it is the power angle change of the synchronous generator under different reactive current injection coefficients of non-metallic ground fault at fault position 1. It can be seen that when k qv is small, the swing of the second pendulum is reduced with the increase of k qv ; but when k qv is increased to 5 or more, the swing of the second pendulum is increased with the increase of k qv , which is not conducive to the transient stability of the system.

[0100] In this embodiment, taking the power system shown in FIG. 6 as an example, a method for improving the transient stability of the system by adjusting the reactive current injection coefficient of the doubly-fed wind turbine is described.

[0101] When a deep fault occurs in the power grid, the terminal voltage of the doubly-fed wind turbine during the fault is monitored in real time, and the size of the reactive current injection coefficient is determined according to the drop degree of the terminal voltage of the doubly-fed wind turbine:

[0102] 1) When U t <U t1 , that is, the terminal voltage of the doubly-fed wind turbine is in the first voltage drop interval, the reactive current injection coefficient k qv of the doubly-fed wind turbine is increased, so as to reduce the swing of the first pendulum of the synchronous generator, while the swing of the second pendulum is almost not affected, thereby enhancing the transient stability of the system.

[0103] 2) When U t2 <U t <U1, that is, the terminal voltage of the doubly-fed wind turbine is in the second voltage drop interval, the reactive current injection coefficient k qv of the doubly-fed wind turbine is increased, so as to reduce the swings of the first and second pendulums of the synchronous generator, thereby enhancing the transient stability of the system.

[0104] 3) When Ut1 <U t <U t2 , that is, the terminal voltage of the doubly-fed wind turbine is in the third voltage drop interval, the reactive current injection coefficient k of the doubly-fed wind turbine is appropriately reduced qv , so as to reduce the second swing amplitude of the synchronous generator while not making the first swing amplitude too large, thereby enhancing the transient stability of the system.

[0105] The adjustment of the reactive current injection coefficient of the doubly-fed wind turbine can be performed according to a pre-set rule.

[0106] The influence of the acceleration stage (first swing amplitude) of the synchronous generator during the fault and the deceleration stage (second swing amplitude) of the generator during the fault clearing on the transient stability of the system is simultaneously considered.

[0107] According to theoretical and simulation analysis, it is known that, at the initial stage of the fault recovery, the second swing amplitude is affected by the initial value of the active current ramping when the active ramping coefficient is the same. According to the terminal voltage amplitude during the fault, the initial value of the active current ramping is divided into three cases, as shown in the following formula:

[0108] In particular, when the terminal voltage during the fault U t1 <U t <U t2 , the active current is limited by the capacity of the converter, and the initial value of the active current ramping decreases with the increase of k qv , which may lead to the increase of the second swing amplitude, which is not conducive to the transient stability of the system. This is contrary to the conclusion that "increasing k qv is beneficial" when only the first swing amplitude is considered, and therefore the influence of the acceleration of the synchronous generator during the fault and the deceleration of the generator during the fault clearing needs to be considered comprehensively.

[0109] In addition, according to theoretical and simulation analysis, it is known that, when not limited by the capacity of the wind turbine, increasing the reactive current injection coefficient is beneficial to the transient stability of the system; when limited by the capacity of the wind turbine, appropriately reducing the reactive current injection coefficient is beneficial to the transient stability of the system. The higher the proportion of wind power, the greater the influence.

[0110] The present application determines the influence law of the reactive current injection coefficient on the transient stability of the wind-thermal bundled system, performs fast and effective transient stability control on the wind-thermal bundled system of the doubly-fed wind turbine, improves the transient stability control effect of the wind-thermal bundled system, improves the control efficiency and practicality, and provides a basis for the adjustment of the transient control parameters of the doubly-fed wind turbine.

[0111] As shown in FIG. 13, it is a structure schematic diagram of a wind-thermal bundled system transient stability control device according to an embodiment of the present application. The device shown in the figure comprises:

[0112] Terminal voltage module 10, configured to obtain terminal voltage of the doubly-fed wind turbine in real time when the wind-thermal bundled system fails;

[0113] First drop interval module 20, configured to increase the reactive current injection coefficient of the doubly-fed wind turbine according to a preset adjustment rule to reduce the swing of the acceleration stage of the synchronous generator during the fault, in response to the terminal voltage of the doubly-fed wind turbine being in a first voltage drop interval;

[0114] Second drop interval module 30, configured to increase the reactive current injection coefficient of the doubly-fed wind turbine according to the adjustment rule to reduce the swing of the acceleration stage of the synchronous generator and the swing of the deceleration stage of the synchronous generator during the fault, in response to the terminal voltage of the doubly-fed wind turbine being in a second voltage drop interval;

[0115] Third drop interval module 40, configured to decrease the reactive current injection coefficient of the doubly-fed wind turbine according to the adjustment rule to reduce the swing of the deceleration stage of the synchronous generator during the fault, in response to the terminal voltage of the doubly-fed wind turbine being in a third voltage drop interval.

[0116] In some embodiments, the first voltage drop interval is less than a first threshold value; the second voltage drop interval is greater than a second threshold value and less than a preset upper voltage limit value; and the third voltage drop interval is greater than the first threshold value and less than the second threshold value.

[0117] In this embodiment, as shown in FIG. 14, the device further comprises:

[0118] Reactive injection module 21, configured to obtain historical terminal voltage and historical reactive current injection coefficient of the doubly-fed wind turbine when the wind-thermal bundled system fails, and determine a reactive injection current value according to the historical terminal voltage and the historical reactive current injection coefficient;

[0119] Reactive current value module 22, configured to obtain a reactive current value according to a preset maximum capacity of the converter and the reactive injection current value;

[0120] First threshold value module 23, configured to determine a first threshold value according to the maximum capacity of the converter, the reactive injection current value and the reactive current value.

[0121] In this embodiment, as shown in FIG. 15, the device further comprises:

[0122] Amplitude limiting value module 31, configured to obtain historical terminal voltage of the doubly-fed wind turbine when the wind-thermal bundled system fails, and determine an amplitude limiting value of low-voltage active limiting logic according to the historical terminal voltage;

[0123] Active current value module 32, configured to obtain an active current value according to a preset maximum capacity of the converter and the amplitude limiting value of the low-voltage active limiting logic;

[0124] The second threshold value module 33 is configured to determine the second threshold value according to the maximum capacity of the converter, the limiting value of the low-voltage active power limiting logic and the active current value.

[0125] Based on the same application concept as the above-mentioned wind-fire bundled system transient stability control method, the application further provides the above-mentioned wind-fire bundled system transient stability control device. Since the principle of solving problems of the wind-fire bundled system transient stability control device is similar to that of the wind-fire bundled system transient stability control method, the implementation of the wind-fire bundled system transient stability control device can be referred to the implementation of the wind-fire bundled system transient stability control method, and the repeated parts will not be described here.

[0126] The application determines the influence law of the reactive current injection coefficient on the transient stability of the wind-fire bundled system, and performs fast and effective transient stability control on the wind-fire bundled system with the reactive current injection coefficient of the double-fed wind turbine, thereby improving the transient stability control effect of the wind-fire bundled system, improving the control efficiency and practicality, and providing a basis for adjustment of the transient control parameters of the double-fed wind turbine.

[0127] The application further provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the above-mentioned method when executing the program.

[0128] The application further provides a computer program product, including computer programs / instructions, which are executed by the processor to implement the steps of the above-mentioned method.

[0129] The application further provides a computer-readable storage medium, which stores a computer program for executing the above-mentioned method by a computer.

[0130] As shown in FIG. 16, the electronic device 600 can further include a communication module 110, an input unit 120, an audio processor 130, a display 160, a power supply 170, and the like. The electronic device 600 can include the partial components shown in FIG. 16, or can include components not shown in FIG. 16.

[0131] As shown in FIG. 16, the central processor 100, also known as a controller or a processor at times, can include a microprocessor, other processor devices, and / or logic devices, which receives inputs and controls the operations of various components of the electronic device 600.

[0132] The memory 140 can be one or more of a buffer, a flash memory, a hard drive, a removable media, a volatile memory, a non-volatile memory, or other suitable device. The above-mentioned information related to the failure can be stored, and in addition, a program for executing the related information can be stored. The central processing unit 100 can execute the program stored in the memory 140 to implement information storage or processing, etc.

[0133] The input unit 120 provides an input to the central processing unit 100. The input unit 120 can be a key or a touch input device. The power supply 170 is used to supply power to the electronic device 600. The display 160 is used to display a display object such as an image and a text. The display can be a liquid crystal display (LCD).

[0134] The memory 140 can be a solid state memory such as a read-only memory (ROM), a random access memory (RAM), a U disk, etc. It can also be a memory that saves information even when power is off, can be selectively erased, and is provided with more data, such as an erasable programmable read-only memory (EPROM), etc. The memory 140 can also be other types of devices. The memory 140 includes a buffer memory 141 (sometimes referred to as a buffer). The memory 140 can include an application / function storage section 142 for storing application programs and function programs or for executing an operation flow of the electronic device 600 by the central processing unit 100.

[0135] The memory 140 can also include a data storage section 143 for storing data such as contacts, digital data, pictures, sounds, and / or any other data used by the electronic device. A driver storage section 144 of the memory 140 can include various drivers of the electronic device for a communication function and / or for executing other functions of the electronic device such as a messaging application, an address book application, etc.

[0136] The communication module 110 is a transmitter / receiver 110 that transmits and receives a signal via an antenna 111. The communication module (transmitter / receiver) 110 is connected to the central processing unit 100 to provide an input signal and receive an output signal, which can be the same as in the case of a conventional mobile communication terminal.

[0137] Based on different communication technologies, multiple communication modules 110, such as a cellular network module, a Bluetooth module, and / or a wireless local area network module, etc., can be provided in the same electronic device. The communication module (transmitter / receiver) 110 is also coupled to a speaker 131 and a microphone 132 via an audio processor 130 to provide audio output via the speaker 131 and to receive audio input from the microphone 132 to implement the usual telecommunication functions. The audio processor 130 can include any suitable buffers, decoders, amplifiers, etc. In addition, the audio processor 130 is also connected to the central processor 100 so that a local recording can be made through the microphone 132 and so that a locally stored sound can be played through the speaker 131.

[0138] Those skilled in the art will appreciate that embodiments of the present application can be readily used as a method, a system or a computer program product. Accordingly, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application can take the form of a computer program product on one or more computer-usable storage media (including magnetic disks, compact discs, optical storage, and the like) embodying computer readable program code.

[0139] The present application is described in reference to the flowchart illustrations and / or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processor or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart illustrations and / or block diagrams block or blocks.

[0140] These computer program instructions can also be stored in a computer- readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instructions which implement the function specified in the flowchart illustrations and / or block diagrams block or blocks.

[0141] These computer program instructions can also be loaded into a computer or other programmable data processing devices, so that a series of operational steps are generated to realize the computer-implemented processes, and the instructions executed on the computer or other programmable devices provide steps for realizing the functions specified in one or more flows of the flowchart and / or one or more blocks of the block diagram.

Claims

1. A method for controlling transient stability of a wind-thermal bundled system, comprising: acquiring a terminal voltage of a doubly-fed wind turbine in real time when the wind-thermal bundled system is in a fault state; in response to the terminal voltage of the doubly-fed wind turbine being in a first voltage drop interval, increasing an injection coefficient of a reactive current of the doubly-fed wind turbine according to a preset adjustment rule, so as to reduce a swing range of an acceleration stage of a synchronous generator during the fault state; in response to the terminal voltage of the doubly-fed wind turbine being in a second voltage drop interval, increasing the injection coefficient of the reactive current of the doubly-fed wind turbine according to the adjustment rule, so as to reduce the swing range of the acceleration stage of the synchronous generator and a swing range of a deceleration stage of the synchronous generator during the fault state; in response to the terminal voltage of the doubly-fed wind turbine being in a third voltage drop interval, decreasing the injection coefficient of the reactive current of the doubly-fed wind turbine according to the adjustment rule, so as to reduce the swing range of the deceleration stage of the synchronous generator during the fault state.

2. The method of claim 1, wherein, The first voltage drop interval is less than a first critical value; the second voltage drop interval is greater than a second critical value and less than a preset upper voltage limit value; and the third voltage drop interval is greater than the first critical value and less than the second critical value. 3.The method of claim 2, further comprising: acquiring a historical terminal voltage and a historical injection coefficient of the reactive current of the doubly-fed wind turbine when the wind-thermal bundled system is in the fault state, and determining a reactive injection current value according to the historical terminal voltage and the historical injection coefficient of the reactive current; obtaining a reactive current value according to a preset maximum capacity of a converter and the reactive injection current value; determining the first critical value according to the maximum capacity of the converter, the reactive injection current value and the reactive current value. 4.The method of claim 2, further comprising: acquiring a historical terminal voltage of the doubly-fed wind turbine when the wind-thermal bundled system is in the fault state, and determining an amplitude limiting value of a low-voltage active power limiting logic according to the historical terminal voltage; obtaining an active current value according to a preset maximum capacity of a converter and the amplitude limiting value of the low-voltage active power limiting logic; determining the second critical value according to the maximum capacity of the converter, the amplitude limiting value of the low-voltage active power limiting logic and the active current value. 5.A device for controlling transient stability of a wind-thermal bundled system, comprising: a terminal voltage module configured to acquire a terminal voltage of a doubly-fed wind turbine in real time when the wind-thermal bundled system is in a fault state; a first drop interval module configured to, in response to the terminal voltage of the doubly-fed wind turbine being in a first voltage drop interval, increase an injection coefficient of a reactive current of the doubly-fed wind turbine according to a preset adjustment rule, so as to reduce a swing range of an acceleration stage of a synchronous generator during the fault state; a second drop interval module configured to, in response to the terminal voltage of the doubly-fed wind turbine being in a second voltage drop interval, increase the injection coefficient of the reactive current of the doubly-fed wind turbine according to the adjustment rule, so as to reduce the swing range of the acceleration stage of the synchronous generator and a swing range of a deceleration stage of the synchronous generator during the fault state; a third drop interval module configured to, in response to the terminal voltage of the doubly-fed wind turbine being in a third voltage drop interval, decrease the injection coefficient of the reactive current of the doubly-fed wind turbine according to the adjustment rule, so as to reduce the swing range of the deceleration stage of the synchronous generator during the fault state.

6. The apparatus of claim 5, wherein, The first voltage drop interval is less than a first threshold value; the second voltage drop interval is greater than a second threshold value and less than a preset upper voltage limit value; and the third voltage drop interval is greater than the first threshold value and less than the second threshold value.

7. The apparatus of claim 6, further comprising: a reactive power injection module configured to obtain historical terminal voltage and historical reactive current injection coefficient of the doubly-fed wind turbine when the wind-thermal bundled system fails, and determine a reactive power injection current value according to the historical terminal voltage and the historical reactive current injection coefficient; a reactive current value module configured to obtain a reactive current value according to a preset maximum capacity of the converter and the reactive power injection current value; a first threshold value module configured to determine a first threshold value according to the maximum capacity of the converter, the reactive power injection current value and the reactive current value.

8. The apparatus of claim 6, further comprising: a limiting value module configured to obtain historical terminal voltage of the doubly-fed wind turbine when the wind-thermal bundled system fails, and determine a limiting value of low-voltage active power limiting logic according to the historical terminal voltage; an active current value module configured to obtain an active current value according to a preset maximum capacity of the converter and the limiting value of the low-voltage active power limiting logic; a second threshold value module configured to determine a second threshold value according to the maximum capacity of the converter, the limiting value of the low-voltage active power limiting logic and the active current value.

9. An electronic device, comprising a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the method of any one of claims 1 to 4.

10. A computer readable storage medium, storing a computer program for executing the method of any one of claims 1 to 4.

11. A computer program product, comprising a computer program executable on a processor to implement the steps of the method of any one of claims 1 to 4.

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