Fault control method, device and electronic equipment for flexible DC grid-connected wind power system

Abstract

The present application discloses a fault control method, device and electronic equipment for a flexible DC grid-connected wind power system. The method of the present application, when detecting that a short-circuit fault occurs in the outgoing line, determines a first current command value of the sending-end converter station during the short-circuit fault according to a preset current limit amplitude value; determines the current limit amplitude value of the wind farm during the short-circuit fault according to the first current command value; determines a second current command value of the wind farm during the short-circuit fault according to the current limit amplitude value of the wind farm during the short-circuit fault, the amplitude of the grid connection point voltage, the rated value of the grid connection point voltage and the equivalent active power; controls the operation of the sending-end converter station according to the first current command value, and controls the operation of the wind farm according to the second current command value. The coordinated control of the wind farm and the sending-end converter station during the short-circuit fault is realized, the phenomenon of refusal to operate of the differential protection device configured on the outgoing line is avoided, and the safe and stable operation ability of the flexible DC grid-connected wind power under the short-circuit fault of the sending-end power grid is improved.

Description

Technical Field

[0001] The present application relates to the technical field of relay protection, and particularly to a fault control method, device and electronic equipment for a flexible HVDC grid-connected wind power system. Background Art

[0002] In the prior art, when a grid short-circuit fault occurs in the outgoing line between the wind farm and the sending converter station in the flexible HVDC grid-connected wind power system, usually the adjustment of the current command value from the single-station perspective of the sending converter station or the wind farm is adopted. However, during the short-circuit fault of the outgoing line, affected by the combined control actions of the wind farm and the sending converter station, the short-circuit current of the outgoing line shows complex controlled characteristics. Adjusting the current command value only from the single-station perspective without comprehensively considering the coordination between the wind farm and the sending converter station may lead to a decrease in the sensitivity of the differential protection configured on the sending AC line and result in a refusal-to-operate phenomenon, which will have an adverse impact on the safety and stability of the flexible HVDC grid-connected wind power system. Summary of the Invention

[0003] In view of this, the present application provides a fault control method, device and electronic equipment for a flexible HVDC grid-connected wind power system, mainly aiming to solve the technical problem that in the prior art, if a short-circuit fault occurs in the outgoing line, adjusting the current command value only from the single-station perspective without comprehensively considering the coordination between the wind farm and the sending converter station may lead to a decrease in the sensitivity of the differential protection configured on the sending AC line and result in a refusal-to-operate phenomenon.

[0004] According to the first aspect of the present application, a fault control method for a flexible HVDC grid-connected wind power system is provided, which is applicable to a flexible HVDC grid-connected wind power system. The flexible HVDC grid-connected wind power system includes a wind farm, a sending converter station and an outgoing line. One end of the outgoing line is connected to the wind farm, and the other end of the outgoing line is connected to the sending converter station. The method includes:

[0005] When detecting that a short-circuit fault occurs in the outgoing line, obtaining a preset current limit value of the sending converter station during the short-circuit fault, an equivalent active power of the wind farm during the short-circuit fault, a grid connection point voltage amplitude, and a rated grid connection point voltage;

[0006] Determining a first current command value of the sending converter station during the short-circuit fault according to the preset current limit value;

[0007] Determining a current limit value of the wind farm during the short-circuit fault according to the first current command value;

[0008] Determining a second current command value of the wind farm during the short-circuit fault according to the current limit value of the wind farm during the short-circuit fault, the grid connection point voltage amplitude, the rated grid connection point voltage, and the equivalent active power;

[0009] Control the operation of the sending converter station according to the first current command value, and control the operation of the wind farm according to the second current command value.

[0010] Optionally, before obtaining the preset current limit value of the sending converter station during the short-circuit fault, the equivalent active power of the wind farm during the short-circuit fault, the grid connection point voltage amplitude, and the grid connection point rated voltage when it is detected that a short-circuit fault occurs in the outgoing line, it further includes:

[0011] Obtain the positive-sequence voltage of the grid connection point of the wind farm;

[0012] If the positive-sequence voltage is less than the preset voltage threshold, determine that a short-circuit fault has occurred in the outgoing line between the wind farm and the sending converter station.

[0013] Optionally, the preset current limit value includes a preset d-axis current limit value and a preset q-axis current limit value, and the first current command value includes a first d-axis current command value and a first q-axis current command value. The step of determining the first current command value of the sending converter station during the short-circuit fault according to the preset current limit value specifically includes:

[0014] Use the preset d-axis current limit value as the first d-axis current command value of the sending converter during the short-circuit fault;

[0015] Use the preset q-axis current limit value as the first q-axis current command value of the sending converter during the short-circuit fault.

[0016] Optionally, the step of determining the current limit value of the wind farm during the short-circuit fault according to the first current command value specifically includes:

[0017] Input the first current command value of the sending converter station during the short-circuit fault into the first mapping relationship to obtain the output current amplitude of the sending converter station during the short-circuit fault, where the first mapping relationship is used to represent the corresponding relationship between the first current command value and the output current amplitude;

[0018] The first mapping relationship is:

[0019]

[0020] where the above is the output current amplitude; the above is the first q-axis current command value; the above is the first d-axis current command value;

[0021] Input the output current amplitude of the sending converter station during the short-circuit fault and the braking coefficient of the differential protection into the second mapping relationship to obtain the current limit value of the wind farm during the short-circuit fault;

[0022] The second mapping relationship is:

[0023]

[0024] Among them, the above-mentioned I wlim is the current limit value of the wind farm during the short-circuit fault; the above-mentioned k is the braking coefficient of the differential protection.

[0025] Optionally, the steps of determining the second current command value of the wind farm during the short-circuit fault according to the current limit value of the wind farm during the short-circuit fault, the grid connection point voltage amplitude, the grid connection point rated voltage, and the equivalent active power specifically include:

[0026] Dividing the grid connection point rated voltage by the grid connection point voltage amplitude to obtain the grid connection point voltage drop depth coefficient of the wind farm grid connection point;

[0027] Using the grid connection point rated voltage, the grid connection point voltage drop depth coefficient, and the equivalent active power to determine the rated current command value of the wind farm during the short-circuit fault;

[0028] According to the current limit value and the rated current command value of the wind farm during the short-circuit fault, determine the second current command value of the wind farm during the short-circuit fault.

[0029] Optionally, the rated current command value includes the rated d-axis current command value and the rated q-axis current command value. The steps of determining the rated current command value of the wind farm during the short-circuit fault by using the grid connection point rated voltage, the grid connection point voltage drop depth coefficient, and the rated equivalent active power specifically include:

[0030] Input the grid connection point voltage amplitude into the third mapping relationship to obtain the rated q-axis current command value of the wind farm during the short-circuit fault, where the third mapping relationship is used to represent the corresponding relationship between the rated q-axis current command value and the grid connection point voltage amplitude;

[0031] The third mapping relationship is:

[0032]

[0033] Among them, the above-mentioned is the rated q-axis current command value; the above-mentioned U wf is the grid connection point voltage amplitude;

[0034] Input the grid connection point voltage drop depth coefficient and the equivalent effective power into the fourth mapping relationship to obtain the rated d-axis current command value of the wind farm during the short-circuit fault, where the fourth mapping relationship is used to represent the corresponding relationship between the rated d-axis current command value, the grid connection point voltage drop depth coefficient, and the equivalent effective power;

[0035] The fourth mapping relationship is:

[0036]

[0037] Among them, the above is the rated d-axis current command value; the above k vf is the depth coefficient of the grid connection point voltage dip; the above is the rated equivalent effective power.

[0038] Optionally, the second current command value includes a second d-axis current command value and a second q-axis current command value. The steps to determine the second current command value of the wind farm during the short-circuit fault according to the current limit value and the rated current command value during the short-circuit fault of the wind farm are specifically as follows:

[0039] Import the rated current command value and the current limit value into the fifth mapping relationship to obtain the amplitude of the second current command value that the wind farm can output during the short-circuit fault, where the fifth mapping relationship is used to represent the corresponding relationship between the amplitude of the second current command value that the wind farm can output during the short-circuit fault, the rated current command value, and the current limit value;

[0040] The fifth mapping relationship is:

[0041]

[0042] Among them, the above is the amplitude of the second current command value that the wind farm can output during the short-circuit fault, the above is the rated q-axis current command value of the wind farm during the short-circuit fault; the above is the rated d-axis current command value of the wind farm during the short-circuit fault; the above I wlim is the current limit value of the wind farm during the short-circuit fault;

[0043] Import the rated current command value into the sixth mapping relationship to calculate the phase angle of the second current command value that the wind farm can output during the short-circuit fault, where the sixth mapping relationship is used to represent the corresponding relationship between the phase angle of the second current command value that the wind farm can output during the short-circuit fault and the rated current command value;

[0044] The sixth mapping relationship is:

[0045]

[0046] Among them, the above is the phase angle of the second current command value that the wind farm can output during the short-circuit fault;

[0047] Import the amplitude and phase angle of the second current command value that the wind farm can output during a short-circuit fault into the seventh mapping relationship to obtain the second q-axis current command value of the wind farm during the short-circuit fault, where the seventh mapping relationship is used to represent the corresponding relationship between the second q-axis current command value, the amplitude, and the phase angle;

[0048] The seventh mapping relationship is:

[0049]

[0050] Among them, the above is the second q-axis current command value of the wind farm during the short-circuit fault;

[0051] Import the amplitude and phase angle of the second current command value that the wind farm can output during a short-circuit fault into the eighth mapping relationship to obtain the second d-axis current command value of the wind farm during the short-circuit fault, where the eighth mapping relationship is used to represent the corresponding relationship between the second d-axis current command value, the amplitude, and the phase angle;

[0052] The eighth mapping relationship is:

[0053]

[0054] Among them, the above is the second d-axis current command value of the wind farm during the short-circuit fault.

[0055] According to the second aspect of the present application, a fault control device for a flexible HVDC grid-connected wind power system is provided, which is applicable to a flexible HVDC grid-connected wind power system. The flexible HVDC grid-connected wind power system includes a wind farm, a sending-end converter station, and a transmission line. One end of the transmission line is connected to the wind farm, and the other end of the transmission line is connected to the sending-end converter station. The device includes:

[0056] An acquisition module, configured to acquire a preset current limit value of the sending-end converter station during a short-circuit fault, an equivalent active power of the wind farm during the short-circuit fault, a grid connection point voltage amplitude, and a grid connection point voltage rated value when it is detected that a short-circuit fault occurs in the transmission line;

[0057] A first determination module, configured to determine a first current command value of the sending-end converter station during a short-circuit fault according to the preset current limit value;

[0058] A second determination module, configured to determine a current limit value of the wind farm during a short-circuit fault according to the first current command value;

[0059] A third determination module, configured to determine a second current command value of the wind farm during a short-circuit fault according to the current limit value of the wind farm during the short-circuit fault, the grid connection point voltage amplitude, the grid connection point voltage rated value, and the equivalent active power;

[0060] A control module, configured to control the operation of the sending-end converter station according to a first current command value and control the operation of the wind farm according to a second current command value.

[0061] According to a third aspect of the present application, there is provided an electronic device, including a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the steps of the method according to any one of the first aspects are implemented.

[0062] According to a fourth aspect of the present application, there is provided a readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the method according to any one of the first aspects are implemented.

[0063] By means of the above technical solutions, a fault control method, device and electronic device for a flexible HVDC grid-connected wind power system provided by the present application first determine a first current command value that the sending-end converter station can output during a short-circuit fault of the sending-end power grid based on the current limit value of the sending-end converter station. Subsequently, based on the first current command value of the sending-end converter station and the output current command value of the wind farm under real-time conditions during the short-circuit fault, the final second current command value of the wind farm during the short-circuit fault is calculated. During the occurrence of the short-circuit fault, the grid-side converters of the wind turbines in the wind farm and the sending-end converter station are switched from outer-loop controls such as a DC voltage outer loop / AC voltage outer loop to a single current loop control, the operation of the sending-end converter station is controlled according to the first current command value, and the operation of the wind farm is controlled according to the second current command value. Compared with the prior art in which when a short-circuit fault is detected in the outgoing line, the fault control scheme only adjusts the current command value from the perspective of a single power station, the present application realizes the coordinated control of the wind farm and the sending-end converter station during the short-circuit fault by simultaneously changing the current command values of the wind farm and the sending-end converter station, avoids the phenomenon of refusal to operate of the differential protection device configured on the outgoing line, effectively improves the reliability of the differential protection configured on the outgoing line of the flexible HVDC grid-connected wind power system, and further improves the safe and stable operation ability of the flexible HVDC grid-connected wind power under the short-circuit fault of the sending-end power grid.

[0064] The above description is only an overview of the technical solutions of the present application. In order to be able to understand the technical means of the present application more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features and advantages of the present application more obvious and understandable, the following specifically illustrates the specific embodiments of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] By reading the detailed description of the preferred embodiments below, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of illustrating the preferred embodiments and are not considered to be a limitation of the present application. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0066] Figure 1 It shows a schematic flow chart of a fault control method for a flexible HVDC grid-connected wind power system provided by an embodiment of the present application;

[0067] Figure 2 It shows a schematic flow chart of another fault control method for a flexible HVDC grid-connected wind power system provided by an embodiment of the present application;

[0068] Figure 3 It shows a schematic structural diagram of a flexible HVDC grid-connected wind power system provided by an embodiment of the present application;

[0069] Figure 4 It shows a schematic diagram of fault control of a sending-end converter station provided by an embodiment of the present application;

[0070] Figure 5 It shows a schematic diagram of fault control of the grid-side converter of an inverter-type wind turbine group in a wind farm provided by an embodiment of the present application;

[0071] Figure 6 It shows a comparative schematic diagram of the differential protection sensitivity simulation waveforms of a flexible HVDC grid-connected wind power system when using a traditional fault control method and the fault control method provided by the present application respectively in the case of a short-circuit fault occurring in the outgoing line provided by an embodiment of the present application;

[0072] Figure 7 It shows a schematic structural diagram of a fault control device for a flexible HVDC grid-connected wind power system provided by an embodiment of the present application. Detailed implementation manners

[0073] Hereinafter, exemplary embodiments of the present application will be described in more detail with reference to the accompanying drawings. Although the exemplary embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present application can be more thoroughly understood and the scope of the present application can be completely conveyed to those skilled in the art.

[0074] An embodiment of the present application provides a fault control method for a flexible HVDC grid-connected wind power system. As Figure 1 shown, the method includes:

[0075] S101. When detecting that a short-circuit fault occurs in the outgoing line, obtain the preset current limit value of the sending-end converter station during the short-circuit fault, the equivalent active power of the wind farm during the short-circuit fault, the amplitude of the grid connection point voltage, and the rated value of the grid connection point voltage.

[0076] The fault control method for the flexible DC grid-connected wind power system provided by the embodiments of the present application is mainly applied to the scenario of control and protection during the occurrence of a grid short-circuit fault on the outgoing line between the wind farm and the sending converter station in the flexible DC grid-connected wind power system. The execution subject of the embodiments of the present application is a device or equipment capable of controlling the current command value during the short-circuit fault of the outgoing grid in the flexible DC grid-connected wind power system, and can be specifically set on the server side. The server can automatically detect the short-circuit fault of the outgoing line in the flexible DC grid-connected wind power system. When detecting that a grid short-circuit fault occurs on the outgoing line, it adjusts the current command values of the sending converter station and the wind farm to achieve coordinated control of the sending converter station and the wind farm, so as to improve the reliability of the differential protection at the sending end of the flexible DC grid-connected wind power system, and further improve the safe and stable operation ability of the flexible DC grid-connected wind power system under the sending-end grid fault.

[0077] As Figure 3 shown, it is a schematic structural diagram of the flexible DC grid-connected wind power system. Specifically, the flexible DC grid-connected wind power system is a system that directly connects a wind farm to the grid through flexible DC transmission technology. Since the flexible DC transmission technology of the modular multilevel converter (MMC) has the advantages of strong controllability and the ability to supply power to passive networks, it is suitable for large-scale wind power grid-connected transmission applications. The flexible DC grid-connected wind power system includes a wind farm, a sending converter station, and an outgoing line. Among them, the wind farm refers to a power generation site composed of multiple wind turbines, which is responsible for converting wind energy into electrical energy; the sending converter station is used to convert the alternating current of the wind farm into direct current and transmit it to the grid-side converter station through a DC line; the outgoing line is located between the wind farm and the sending converter station and is used to transmit the alternating electrical energy generated by the wind farm to the sending converter station to prepare for further conversion into direct current. In addition, the flexible DC grid-connected wind power system also includes a collector bus and a receiving heat exchange station.

[0078] A differential protector is configured on the outgoing line. When detecting that a grid short-circuit fault occurs on the outgoing line, the differential protector triggers a protection action to prevent system faults. Compared with the general wind power grid-connected system, under the combined action of the wind farm and the sending converter station in the flexible DC grid-connected wind power system, the short-circuit current characteristics of the system have changed fundamentally, which may lead to a decrease in the sensitivity of the differential protector configured on the outgoing line, and even the sensitivity may be less than 1 and a refusal-to-operate phenomenon may occur, seriously affecting the safety of the system. Based on the above problems, the present application proposes that when detecting that a grid short-circuit fault occurs on the outgoing line, the current command values of the sending converter station and the wind farm are adjusted to achieve coordinated control of the sending converter station and the wind farm, so as to improve the reliability of the differential protection at the sending end of the flexible DC grid-connected wind power system, and further improve the safe and stable operation ability of the flexible DC grid-connected wind power system under the sending-end grid fault.

[0079] Specifically, when a short-circuit fault occurs in the outgoing line, first obtain the preset current limit value of the sending-end converter station during the short-circuit fault of the sending-end power grid, and the rated grid connection point voltage value of the wind farm grid connection point during the short-circuit fault of the sending-end power grid. Herein, the wind farm grid connection point is the point of common coupling (PCC point) on the wind farm side. Further, when a short-circuit fault occurs in the outgoing line, the equivalent active power of the wind farm and the grid connection point voltage amplitude of the wind farm grid connection point are collected in real time.

[0080] Optionally, the preset current limit value of the sending-end converter station and the rated grid connection point voltage value of the wind farm grid connection point can be set according to the design and specification requirements of the flexible HVDC grid-connected wind power system during the fault. This application does not make specific limitations here.

[0081] S102. Determine the first current command value of the sending-end converter station during the short-circuit fault according to the preset current limit value.

[0082] In this step, when a short-circuit fault occurs in the outgoing line, according to the preset current limit value, determine the first current command value that the sending-end converter station can output during the short-circuit fault. Use the preset current limit value to limit the magnitude of the current command value of the sending-end converter station during the short-circuit fault to ensure that the differential protection device configured on the outgoing line can operate reliably.

[0083] S103. Determine the current limit value of the wind farm during the short-circuit fault according to the first current command value.

[0084] In this step, during the short-circuit fault, affected by the combined control actions of the wind farm and the sending-end converter station, the short-circuit current of the outgoing line will exhibit complex controlled characteristics, which will affect the sensitivity of the differential protection device. To improve the operation performance of the differential protection device on the outgoing line of the flexible HVDC grid-connected wind power system, use the current command value that the sending-end converter station can output during the short-circuit fault to calculate the current limit value that the wind farm can output during the short-circuit fault of the sending-end power grid, ensure that the differential protection device configured on the outgoing line can operate reliably, and improve the safe and stable operation ability of the flexible HVDC grid-connected wind power system under the short-circuit fault of the sending-end power grid.

[0085] S104. Determine the second current command value of the wind farm during the short-circuit fault according to the current limit value of the wind farm during the short-circuit fault, the grid connection point voltage amplitude, the rated grid connection point voltage value, and the equivalent active power.

[0086] In this step, based on the grid connection point voltage amplitude, equivalent active power, and grid connection point voltage rated value collected in real time during the short-circuit fault of the wind farm, the output current command value output to the wind farm under the real-time conditions of the short-circuit fault is calculated. Further, in order to meet the coordinated control of the sending-end converter station and the wind farm, it is also necessary to use the current limit value that the wind farm can output during the short-circuit fault of the sending-end power grid, combined with the output current command value of the wind farm under real-time conditions, to calculate the final second current command value of the wind farm.

[0087] In the above manner, according to the output current command value that can be output to the wind farm under real-time conditions and the current limit value of the wind farm, the final second current command value of the wind farm is calculated, ensuring that the current of the wind farm during the short-circuit fault of the sending-end power grid does not exceed the safety limit, while fully considering the coordinated control between the wind farm and the sending-end converter station, and improving the reliability of the differential protection configured on the outgoing line.

[0088] S105. Control the operation of the sending-end converter station according to the first current command value, and control the operation of the wind farm according to the second current command value.

[0089] In this step, after calculating the first current command value of the sending-end converter station and the second current command value of the wind farm during the short-circuit fault of the sending-end power grid, the current loop command value of the sending-end converter station is switched to the first current command value, and the current loop command value of the grid-side converter of the wind turbines in the wind farm is switched to the second current command value.

[0090] In an actual application scenario, as Figure 4 shown, it is a schematic diagram of the fault control of the sending-end converter station. When a short-circuit fault occurs in the outgoing line is detected, the flexible HVDC grid-connected wind power system switches to the fault ride-through control mode. At this time, the fault ride-through control module sends a fault control switching command to the sending-end converter station, disconnects the outer-loop controls such as the DC voltage outer loop / AC voltage outer loop, switches to the single current loop control (that is, the control command switching module receives the switching command and switches from 1 to 2), and switches the current loop command value of the sending-end converter station to the calculated first current command value. As Figure 5 shown, it is a schematic diagram of the fault control of the grid-side converter of the inverter-type wind turbines in the wind farm. The wind farm includes the grid-side converter of the wind turbines. When a short-circuit fault occurs in the outgoing line is detected, the flexible HVDC grid-connected wind power system switches to the fault ride-through control mode. At this time, the fault ride-through control module sends a fault control switching command to the wind farm, disconnects the outer-loop controls such as the DC voltage outer loop / AC voltage outer loop, switches to the single current loop control (that is, the control command switching module receives the switching command and switches from 1 to 2), and switches the current loop command value of the grid-side converter of the wind turbines to the calculated second current command value.

[0091] The fault control method for the flexible DC grid-connected wind power system provided by the embodiment of the present application first determines the first current command value that the sending converter station can output during the short-circuit fault of the sending power grid based on the current limit value of the sending converter station. Subsequently, based on the first current command value of the sending converter station and the wind farm output current command value under real-time conditions during the short-circuit fault, the final second current command value of the wind farm during the short-circuit fault is calculated. During the occurrence of the short-circuit fault, the grid-side converters of the wind turbines in the wind farm and the sending converter station are switched from outer-loop controls such as DC voltage outer-loop / AC voltage outer-loop to single current-loop control. The sending converter station is controlled to operate according to the first current command value, and the wind farm is controlled to operate according to the second current command value. Compared with the existing technology, when a short-circuit fault is detected in the outgoing line, the fault control scheme only adjusts the current command value from the perspective of a single substation. In the present application, by simultaneously changing the current command values of the wind farm and the sending converter station, the coordinated control of the wind farm and the sending converter station during the short-circuit fault is realized, avoiding the phenomenon of refusal to operate of the differential protection device configured on the outgoing line, effectively improving the reliability of the differential protection configured on the outgoing line of the flexible DC grid-connected wind power system, and further improving the safe and stable operation ability of the flexible DC grid-connected wind power under the short-circuit fault of the sending power grid.

[0092] Further, as Figure 2 shown, as a refinement and extension of the specific implementation manner of the above embodiment, in order to fully illustrate the specific implementation process of this embodiment, the embodiment of the present application provides another fault control method for the flexible DC grid-connected wind power system, and this method includes:

[0093] S201. Obtain the positive-sequence voltage of the grid connection point of the wind farm.

[0094] S202. Determine whether the positive-sequence voltage is less than a preset voltage threshold. If so, enter step S203; if not, enter step S204.

[0095] In steps S201 and S202, by detecting the positive-sequence voltage of the grid connection point at the sending end of the wind farm in the system in real time and comparing it with the preset voltage threshold, it is possible to timely detect whether there is an abnormal short-circuit fault in the outgoing line and ensure the safe and stable operation of the system.

[0096] Optionally, the value range of the preset voltage threshold can be set according to the normal operating voltage of the system and the allowable voltage deviation. For example, the preset voltage threshold can be set to 0.9 p.u. If it is detected that the positive-sequence voltage at the grid connection point at the sending end of the wind farm drops below 0.9 p.u., it is determined that a short-circuit fault has occurred in the sending AC line (i.e., the outgoing line) between the wind farm and the sending converter station.

[0097] S203. Determine that a short-circuit fault has occurred in the outgoing line between the wind farm and the sending converter station.

[0098] S204. Confirm the normal operation of the transmission line between the wind farm and the sending-end converter station, and continuously detect the positive-sequence voltage at the grid connection point of the wind farm.

[0099] In steps S203 and S204, if the positive-sequence voltage at the grid connection point of the wind farm is less than the preset voltage threshold, it means that there is a problem with the grid connection or the voltage load increases resulting in a voltage drop, and it can be determined that a symmetrical short-circuit fault has occurred in the transmission line. At this time, the wind power flexible DC grid-connected system is switched to the fault ride-through control mode to ensure the safety of the system. Further, if the positive-sequence voltage at the grid connection point of the wind farm is greater than or equal to the preset voltage threshold, it means that there is no problem with the grid connection, that is, the transmission line is normal and no symmetrical short-circuit fault has occurred. At this time, continuously detect the positive-sequence voltage at the grid connection point of the wind farm to ensure the stability of the system operation.

[0100] S205. Obtain the preset current limit value of the sending-end converter station during the short-circuit fault, the equivalent active power of the wind farm during the short-circuit fault, the amplitude of the grid connection point voltage, and the rated value of the grid connection point voltage.

[0101] This step is the same as Figure 1 the method of step S101 shown, and will not be elaborated here.

[0102] S206. Use the preset d-axis current limit value as the first d-axis current command value of the sending-end converter during the short-circuit fault.

[0103] S207. Use the preset q-axis current limit value as the first q-axis current command value of the sending-end converter during the short-circuit fault.

[0104] In steps S206 and S207, the preset current limit value of the sending-end converter station includes the preset d-axis current limit value and the preset q-axis current limit value. Use the preset d-axis current limit value as the first d-axis current command value of the sending-end converter station during the short-circuit fault of the sending-end power grid, and use the preset q-axis current limit value as the first q-axis current command value of the sending-end converter station during the short-circuit fault of the sending-end power grid.

[0105] In the above way, use the current limit value to limit the maximum value of the current of the sending-end converter station during the short-circuit fault of the sending-end power grid, ensure that the system can still maintain a relatively stable operating state during the short-circuit fault of the sending-end power grid, and reduce the impact of instability and volatility on the system.

[0106] S208. Determine the current limit value of the wind farm during the short-circuit fault according to the first current command value.

[0107] This step is the same as Figure 1 the method of step S103 shown, and will not be elaborated here.

[0108] In an embodiment of the present application, optionally, in order to accurately calculate the current limit value of the wind farm during a short-circuit fault, in step S208, according to the first current command value, determining the current limit value of the wind farm during the short-circuit fault specifically includes: importing the first current command value of the sending converter station during the short-circuit fault into the first mapping relationship to obtain the output current amplitude of the sending converter station during the short-circuit fault, where the first mapping relationship is used to represent the corresponding relationship between the first current command value and the output current amplitude;

[0109] The first mapping relationship is:

[0110]

[0111] wherein, the above is the output current amplitude; the above is the first q-axis current command value; the above is the first d-axis current command value.

[0112] Further, importing the output current amplitude of the sending converter station during the short-circuit fault and the braking coefficient of the differential protection into the second mapping relationship to obtain the current limit value of the wind farm during the short-circuit fault;

[0113] The second mapping relationship is:

[0114]

[0115] wherein, the above I wlim is the current limit value of the wind farm during the short-circuit fault; the above k is the braking coefficient of the differential protection.

[0116] In this embodiment, importing the d-axis current command value and the q-axis current command value of the sending converter station during the short-circuit fault into the first mapping relationship, calculating the output current amplitude of the sending converter station during the short-circuit fault, and obtaining the actual magnitude of the output current of the sending converter station during the short-circuit fault. Subsequently, importing the output current amplitude that the sending converter station can output during the short-circuit fault and the braking coefficient of the differential protection into the second mapping relationship to calculate the current limit value of the wind farm during the short-circuit fault.

[0117] By the above method, calculating the wind farm current limit value according to the actual output current amplitude can more accurately protect the operating state of the wind power flexible DC grid-connected system during a short-circuit fault, rather than relying on preset values, realizing the coordinated control of the wind farm and the sending converter station, and improving the reliability of the sending-end differential protection of the wind power flexible DC grid-connected system.

[0118] Optionally, the value range of the braking coefficient of the differential protection can be 0.5 - 0.85.

[0119] S209. Divide the rated value of the grid connection point voltage by the amplitude of the grid connection point voltage to obtain the grid connection point voltage dip depth coefficient of the wind farm at the grid connection point.

[0120] S210. Determine the rated current command value of the wind farm during the short-circuit fault by using the rated value of the grid connection point voltage, the grid connection point voltage dip depth coefficient, and the equivalent active power;

[0121] In this step, divide the rated value of the grid connection point voltage by the amplitude of the grid connection point voltage to obtain the grid connection point voltage dip depth coefficient of the wind farm. Further, when a short-circuit fault occurs in the power grid, the wind power flexible DC grid-connected system enters the fault ride-through control mode and adopts corresponding control strategies to protect the system equipment from damage. This control mode is achieved by adjusting the parameters of the current controller. Therefore, when a short-circuit fault of the sending-end power grid is detected, the wind power flexible DC grid-connected system is switched to the fault ride-through control mode. At this time, use the rated value of the grid connection point voltage, the grid connection point voltage dip depth coefficient, and the equivalent active power to calculate the rated current command value that can be output to the wind farm under real-time conditions.

[0122] In the embodiment of the present application, optionally, in step S210, determining the rated current command value of the wind farm during the short-circuit fault by using the rated value of the grid connection point voltage, the grid connection point voltage dip depth coefficient, and the equivalent active power specifically includes: importing the amplitude of the grid connection point voltage into the third mapping relationship to obtain the rated q-axis current command value of the wind farm during the short-circuit fault, where the third mapping relationship is used to represent the corresponding relationship between the rated q-axis current command value and the amplitude of the grid connection point voltage;

[0123] The third mapping relationship is:

[0124]

[0125] where, the above is the rated q-axis current command value; the above U wf is the amplitude of the grid connection point voltage.

[0126] Further, import the grid connection point voltage dip depth coefficient and the equivalent active power into the fourth mapping relationship to obtain the rated d-axis current command value of the wind farm during the short-circuit fault, where the fourth mapping relationship is used to represent the corresponding relationship between the rated d-axis current command value, the grid connection point voltage dip depth coefficient, and the equivalent active power;

[0127] The fourth mapping relationship is:

[0128]

[0129] where, the above is the rated d-axis current command value; the above k vfis the depth coefficient of the grid connection point voltage dip; the above is the rated equivalent effective power.

[0130] In this embodiment, the rated current command values of the wind farm during the short-circuit fault include the rated d-axis current command value and the rated q-axis current command value. First, the grid connection point voltage amplitude is introduced into the third mapping relationship to calculate the rated q-axis current command value of the wind farm during the short-circuit fault. Subsequently, the depth coefficient of the grid connection point voltage dip and the equivalent effective power are introduced into the fourth mapping relationship to calculate the rated d-axis current command value of the wind farm during the short-circuit fault.

[0131] S211. Determine the second current command value of the wind farm during the short-circuit fault according to the current limit value and the rated current command value of the wind farm during the short-circuit fault.

[0132] In this step, in order to coordinate the current control commands of the wind farm and the sending-end converter station during the short-circuit fault of the sending-end power grid and avoid affecting the sensitivity of the differential protection device configured on the outgoing line, the output current limit value and the rated current command value of the wind farm during the short-circuit fault are used to calculate the final second current command value of the wind farm during the short-circuit fault.

[0133] In the embodiment of the present application, optionally, in step S211, determining the second current command value of the wind farm during the short-circuit fault according to the current limit value and the rated current command value of the wind farm during the short-circuit fault specifically includes:

[0134] Introduce the rated current command value and the current limit value into the fifth mapping relationship to obtain the amplitude of the second current command value that the wind farm can output during the short-circuit fault, where the fifth mapping relationship is used to represent the corresponding relationship between the amplitude of the second current command value that the wind farm can output during the short-circuit fault, the rated current command value, and the current limit value;

[0135] The fifth mapping relationship is:

[0136]

[0137] where the above is the amplitude of the second current command value that the wind farm can output during the short-circuit fault, the above is the rated q-axis current command value of the wind farm during the short-circuit fault; the above is the rated d-axis current command value of the wind farm during the short-circuit fault; the above I wlim is the current limit value of the wind farm during the short-circuit fault.

[0138] Further, import the rated current command value into the sixth mapping relationship to calculate the phase angle of the second current command value that the wind farm can output during the short-circuit fault, where the sixth mapping relationship is used to represent the corresponding relationship between the phase angle of the second current command value that the wind farm can output during the short-circuit fault and the rated current command value;

[0139] The sixth mapping relationship is as follows:

[0140]

[0141] where the above is the phase angle of the second current command value that the wind farm can output during the short-circuit fault.

[0142] Further, import the amplitude and phase angle of the second current command value that the wind farm can output during the short-circuit fault into the seventh mapping relationship to obtain the second q-axis current command value of the wind farm during the short-circuit fault, where the seventh mapping relationship is used to represent the corresponding relationship between the second q-axis current command value, the amplitude, and the phase angle;

[0143] The seventh mapping relationship is as follows:

[0144]

[0145] where the above is the second q-axis current command value of the wind farm during the short-circuit fault.

[0146] Further, import the amplitude and phase angle of the second current command value that the wind farm can output during the short-circuit fault into the eighth mapping relationship to obtain the second d-axis current command value of the wind farm during the short-circuit fault, where the eighth mapping relationship is used to represent the corresponding relationship between the second d-axis current command value, the amplitude, and the phase angle;

[0147] The eighth mapping relationship is as follows:

[0148]

[0149] where the above is the second d-axis current command value of the wind farm during the short-circuit fault.

[0150] In this embodiment, after calculating the current limit value and the rated current command value of the wind farm during the short-circuit fault, the rated current command value and the output current limit value are imported into the fifth mapping relationship to calculate the amplitude of the current command value that the wind farm can output during the short-circuit fault. Further, the rated d-axis current command value and the rated q-axis current command value are imported into the sixth mapping relationship to calculate the phase angle of the current command value that the wind farm can output during the short-circuit fault. Then, the amplitude and phase angle of the current command value that the wind turbine can output during the short-circuit fault are imported into the seventh mapping relationship to calculate the second q-axis current command value of the wind farm during the short-circuit fault. Finally, the amplitude and phase angle of the current command value of the wind farm during the short-circuit fault are imported into the seventh mapping relationship to calculate the second d-axis current command value of the wind farm during the short-circuit fault.

[0151] S212. Control the operation of the sending-end converter station according to the first current command value, and control the operation of the wind farm according to the second current command value.

[0152] This step is the same as the method of step S105 shown in Figure 1 and will not be elaborated here.

[0153] In an embodiment of the present application, the fault control method of the flexible HVDC grid-connected wind power system of the present application embodiment includes the following five steps:

[0154] S1: The flexible HVDC grid-connected wind power system adopts the motor convention, and it is stipulated that the q-axis of the dq-axis rotating coordinate system leads the d-axis. When it is detected that the positive-sequence voltage at the grid connection point of the wind farm drops below 0.9 p.u., both the grid-side converters of the wind turbines in the wind farm and the sending-end converter station are switched to single current-loop control, that is, during the short-circuit fault, the outer-loop controls such as the DC voltage outer loop / AC voltage outer loop are disconnected, and the current-loop command value is switched to the current command value during the fault ride-through control.

[0155] S2: During the short-circuit fault of the outgoing line, the first current command value of the sending-end converter station is given according to the following formula:

[0156]

[0157] where the above is the preset d-axis current limit value of the sending-end converter station; the above is the preset q-axis current limit value of the sending-end converter station; the above is the first d-axis current command value of the sending-end converter station; the above is the first q-axis current command value of the sending-end converter station.

[0158] S3: Calculate the output current amplitude of the sending-end converter station and the output current command value sent by the fault ride-through control module to the wind farm after the wind power HVDC grid-connected system switches to the fault ride-through control mode according to the following formula:

[0159]

[0160] where, the above is the rated q-axis current command value; the above U wf is the grid connection point voltage amplitude; the above is the rated d-axis current command value; the above k vf is the grid connection point voltage dip depth coefficient; the above is the rated equivalent active power; the above U wN is the grid connection point voltage rated value.

[0161] S4: Coordinate the current control of the sending-end converter station and the wind farm, and calculate the current limit value of the wind farm according to the following formula:

[0162]

[0163] where, the above is the output current amplitude; the above is the first q-axis current command value; the above is the first d-axis current command value; the above I wlim is the current limit value of the wind farm during the short-circuit fault; the above k is the braking coefficient of the differential protection.

[0164] S5: Calculate the final second current command value of the wind farm according to the following formula based on the output current command value and the current limit value of the wind farm:

[0165]

[0166] where, the above is the amplitude of the current command value of the wind turbine during the short-circuit fault, the above is the rated q-axis current command value of the wind farm during the short-circuit fault; the above is the rated d-axis current command value of the wind farm during the short-circuit fault; the above I wlim is the output current limit value of the wind farm during the short-circuit fault; the above is the phase angle of the current command value of the wind turbine during the short-circuit fault; the above is the second q-axis current command value of the wind turbine during the short-circuit fault; the above is the second d-axis current command value of the wind turbine during the short-circuit fault.

[0167] In actual application scenarios, such as Figure 6As shown in the figure, it is a comparative schematic diagram of the differential protection sensitivity simulation waveforms of the wind power flexible DC grid-connected system using the traditional fault control method and the fault control method provided in this application when a short-circuit fault occurs in the outgoing line. It is detected that the fault point is located at the midpoint of the outgoing line, and the transition resistance R G is 40 Ω, the braking coefficient k is 0.5, and the fault duration is 1.29 s - 1.9 s. When using the traditional fault control strategy, the sending-end converter station still maintains the constant AC voltage control, and the wind farm issues the q-axis inductive reactive current according to the grid connection guidelines. Figure 6 (a) to (d) in (1) respectively show the dq-axis voltages at the grid connection point of the wind farm, the differential protection sensitivity, the dq-axis currents of the wind farm, and the dq-axis currents of the sending-end converter station when the wind power flexible DC grid-connected system adopts the traditional single-station fault control strategy in the case of a short-circuit fault in the outgoing line. Among them, after using the traditional single-station fault control method, the wind farm outputs a q-axis current command value of 0.8 p.u., and the dq-axis current command values of the sending-end converter station are -1.1 p.u. and 0 p.u. respectively. At this time, the differential protection sensitivity is only 0.7, and the differential protection will fail to operate. Figure 6 (a) to (d) in (2) respectively show the dq-axis voltages at the grid connection point of the wind farm, the differential protection sensitivity, the dq-axis currents of the wind farm, and the dq-axis currents of the sending-end converter station when the wind power flexible DC grid-connected system adopts the traditional single-station fault control strategy in the case of a short-circuit fault in the outgoing line. It can be clearly seen that after adopting the coordinated fault control of the control and protection for the wind farm and the sending-end converter station provided in this application, the differential protection sensitivity is increased to 1.49, and the differential protection can operate correctly.

[0168] Furthermore, as Figure 1 a specific implementation of the method, an embodiment of this application provides a fault control device 300 for a wind power flexible DC grid-connected system, which is applicable to a wind power flexible DC grid-connected system. Among them, the wind power flexible DC grid-connected system includes a wind farm, a sending-end converter station, and an outgoing line. One end of the outgoing line is connected to the wind farm, and the other end of the outgoing line is connected to the sending-end converter station. As Figure 7 shown, the device includes: an acquisition module 301, a first determination module 302, a second determination module 303, a third determination module 304, and a control module 305.

[0169] The acquisition module 301 is configured to, when detecting that a short-circuit fault occurs in the outgoing line, acquire the preset current limit value of the sending-end converter station during the short-circuit fault, the equivalent active power of the wind farm during the short-circuit fault, the amplitude of the grid connection point voltage, and the rated value of the grid connection point voltage;

[0170] The first determination module 302 is configured to determine a first current command value of the sending-end converter station during the short-circuit fault according to the preset current limit value;

[0171] The second determination module 303 is configured to determine the current limit value of the wind farm during a short-circuit fault according to the first current command value;

[0172] The third determination module 304 is configured to determine a second current command value of the wind farm during a short-circuit fault according to the current limit value of the wind farm during the short-circuit fault, the grid connection point voltage amplitude, the rated grid connection point voltage, and the equivalent active power;

[0173] The control module 305 is configured to control the operation of the sending-end converter station according to the first current command value and control the operation of the wind farm according to the second current command value.

[0174] In a specific application scenario, the acquisition module 301 is further configured to acquire the positive-sequence voltage of the grid connection point of the wind farm.

[0175] In a specific application scenario, as Figure 7 shown, the device further includes: a judgment module 306 and a fourth determination module 307.

[0176] The judgment module 306 is configured to compare the positive-sequence voltage with a preset voltage threshold;

[0177] The fourth determination module 307 is configured to determine that a short-circuit fault has occurred in the outgoing line between the wind farm and the sending-end converter station if the positive-sequence voltage is less than the preset voltage threshold.

[0178] In a specific application scenario, the preset current limit value includes a preset d-axis current limit value and a preset q-axis current limit value, and the first current command value includes a first d-axis current command value and a first q-axis current command value. For the first current command value of the sending-end converter station during a short-circuit fault, the first determination module 302 is specifically configured to:

[0179] Use the preset d-axis current limit value as the first d-axis current command value of the sending-end converter during the short-circuit fault;

[0180] Use the preset q-axis current limit value as the first q-axis current command value of the sending-end converter during the short-circuit fault.

[0181] In a specific application scenario, for determining the current limit value of the wind farm during a short-circuit fault, the second determination module 303 is specifically configured to:

[0182] Import the first current command value of the sending-end converter station during the short-circuit fault into a first mapping relationship to obtain the output current amplitude of the sending-end converter station during the short-circuit fault, where the first mapping relationship is used to represent the corresponding relationship between the first current command value and the output current amplitude;

[0183] The first mapping relationship is:

[0184]

[0185] Among them, the above-mentioned is the output current amplitude; the above-mentioned is the first q-axis current command value; the above-mentioned is the first d-axis current command value;

[0186] Introduce the output current amplitude of the sending-end converter station during the short-circuit fault and the braking coefficient of the differential protection into the second mapping relationship to obtain the current limit value of the wind farm during the short-circuit fault;

[0187] The second mapping relationship is:

[0188]

[0189] Among them, the above-mentioned I wlim is the current limit value of the wind farm during the short-circuit fault; the above-mentioned k is the braking coefficient of the differential protection.

[0190] In a specific application scenario, in order to obtain the second current command value of the wind farm during the short-circuit fault, the third determination module 304 is specifically used for:

[0191] Divide the rated value of the grid connection point voltage by the amplitude of the grid connection point voltage to obtain the voltage dip depth coefficient of the grid connection point of the wind farm;

[0192] Use the rated value of the grid connection point voltage, the voltage dip depth coefficient of the grid connection point, and the equivalent active power to determine the rated current command value of the wind farm during the short-circuit fault;

[0193] According to the current limit value and the rated current command value of the wind farm during the short-circuit fault, determine the second current command value of the wind farm during the short-circuit fault.

[0194] In a specific application scenario, the rated current command value includes the rated d-axis current command value and the rated q-axis current command value. In order to determine the rated current command value of the wind farm during the short-circuit fault, the third determination module 304 is specifically further used for:

[0195] Introduce the amplitude of the grid connection point voltage into the third mapping relationship to obtain the rated q-axis current command value of the wind farm during the short-circuit fault, where the third mapping relationship is used to represent the corresponding relationship between the rated q-axis current command value and the amplitude of the grid connection point voltage;

[0196] The third mapping relationship is:

[0197]

[0198] Among them, the above-mentioned is the rated q-axis current command value; the above-mentioned U wf is the amplitude of the grid connection point voltage;

[0199] The depth coefficient of the grid connection point voltage dip and the equivalent effective power are imported into the fourth mapping relationship to obtain the rated d-axis current command value of the wind farm during the short-circuit fault. The fourth mapping relationship is used to represent the corresponding relationship between the rated d-axis current command value, the depth coefficient of the grid connection point voltage dip, and the equivalent effective power;

[0200] The fourth mapping relationship is:

[0201]

[0202] Among them, the above is the rated d-axis current command value; the above k vf is the depth coefficient of the grid connection point voltage dip; the above is the rated equivalent effective power.

[0203] In a specific application scenario, the second current command value includes a second d-axis current command value and a second q-axis current command value. To determine the second current command value of the wind farm during the short-circuit fault, the third determination module 304 is specifically further configured to:

[0204] The rated current command value and the current limit value are imported into the fifth mapping relationship to obtain the amplitude of the second current command value that the wind farm can output during the short-circuit fault. The fifth mapping relationship is used to represent the corresponding relationship between the amplitude of the second current command value that the wind farm can output during the short-circuit fault, the rated current command value, and the current limit value;

[0205] The fifth mapping relationship is:

[0206]

[0207] Among them, the above is the amplitude of the second current command value that the wind farm can output during the short-circuit fault, the above is the rated q-axis current command value of the wind farm during the short-circuit fault; the above is the rated d-axis current command value of the wind farm during the short-circuit fault; the above I wlim is the current limit value of the wind farm during the short-circuit fault;

[0208] The rated current command value is imported into the sixth mapping relationship to calculate the phase angle of the second current command value that the wind farm can output during the short-circuit fault. The sixth mapping relationship is used to represent the corresponding relationship between the phase angle of the second current command value that the wind farm can output during the short-circuit fault and the rated current command value;

[0209] The sixth mapping relationship is:

[0210]

[0211] Among them, the above is the phase angle of the second current command value that the wind farm can output during the short-circuit fault;

[0212] Import the amplitude and phase angle of the second current command value that the wind farm can output during the short-circuit fault into the seventh mapping relationship to obtain the second q-axis current command value of the wind farm during the short-circuit fault, where the seventh mapping relationship is used to represent the corresponding relationship between the second q-axis current command value, amplitude, and phase angle;

[0213] The seventh mapping relationship is:

[0214]

[0215] Among them, the above is the second q-axis current command value of the wind farm during the short-circuit fault;

[0216] Import the amplitude and phase angle of the second current command value that the wind farm can output during the short-circuit fault into the eighth mapping relationship to obtain the second d-axis current command value of the wind farm during the short-circuit fault, where the eighth mapping relationship is used to represent the corresponding relationship between the second d-axis current command value, amplitude, and phase angle;

[0217] The eighth mapping relationship is:

[0218]

[0219] Among them, the above is the second d-axis current command value of the wind farm during the short-circuit fault.

[0220] The fault control device 300 of the flexible DC grid-connected wind power system provided by the embodiment of the present application first determines the first current command value that the sending converter station can output during the short-circuit fault of the sending power grid based on the current limit value of the sending converter station. Subsequently, based on the first current command value of the sending converter station and the wind farm output current command value under real-time conditions during the short-circuit fault, the final second current command value of the wind farm during the short-circuit fault is calculated. During the occurrence of the short-circuit fault, the grid-side converters of the wind turbines in the wind farm and the sending converter station are switched from the outer-loop control such as the DC voltage outer loop / AC voltage outer loop to the single current loop control. The sending converter station is controlled to operate according to the first current command value, and the wind farm is controlled to operate according to the second current command value. Compared with the prior art in which only the current command value is adjusted from the perspective of a single substation when a short-circuit fault is detected in the outgoing line, the present application realizes the coordinated control of the wind farm and the sending converter station during the short-circuit fault by simultaneously changing the current command values of the wind farm and the sending converter station, avoiding the phenomenon of refusal to operate of the differential protection device configured on the outgoing line, effectively improving the reliability of the differential protection configured on the outgoing line of the flexible DC grid-connected wind power system, and further improving the safe and stable operation ability of the flexible DC grid-connected wind power under the short-circuit fault of the sending power grid.

[0221] In an exemplary embodiment, the present application also provides an electronic device, including a memory and a processor. The memory stores a computer program, and the processor is configured to execute the program stored on the memory to execute the fault control method of the flexible DC grid-connected wind power system in the above embodiment.

[0222] In an exemplary embodiment, the present application also provides a readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the fault control method of the flexible DC grid-connected wind power system are realized.

[0223] Through the description of the above embodiments, those skilled in the art can clearly understand that the present application can be implemented by hardware or by means of software plus a necessary general hardware platform. Based on such an understanding, the technical solution of the present application can be embodied in the form of a software product, and the software product can be stored in a non-volatile readable storage medium (which can be a CD-ROM, a USB flash drive, a mobile hard disk, etc.), including several instructions for causing an electronic device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in various implementation scenarios of the present application.

[0224] Those skilled in the art can understand that the drawings are only schematic diagrams of a preferred implementation scenario, and the modules or processes in the drawings are not necessarily essential for implementing the present application.

[0225] Those skilled in the art can understand that the modules in the devices in the implementation scenarios can be distributed in the devices in the implementation scenarios according to the description of the implementation scenarios, or can be correspondingly changed to be located in one or more devices different from this implementation scenario. The modules in the above implementation scenarios can be combined into one module, or can be further split into multiple units.

[0226] The above serial numbers of the present application are only for description and do not represent the advantages or disadvantages of the implementation scenarios.

[0227] The above-disclosed are only several specific implementation scenarios of the present application. However, the present application is not limited thereto, and any changes that can be conceived by those skilled in the art should fall within the protection scope of the present application.

Claims

1. A fault control method for a wind power flexible direct current grid-connected system, characterized in that: Applicable to a wind power flexible direct current grid-connected system, wherein the wind power flexible direct current grid-connected system comprises a wind farm, a sending-end converter station and a sending line, one end of the sending line is connected to the wind farm, and the other end of the sending line is connected to the sending-end converter station, and the method comprises: When a short circuit fault is detected in the transmission line, a preset current limit value of the transmission end converter station during the short circuit fault, an equivalent active power of the wind farm during the short circuit fault, a grid connection point voltage amplitude, and a grid connection point voltage rated value are obtained; Determining a first current command value of the sending-end converter station during a short-circuit fault according to the preset current limit value; determining a current limit value of the wind farm during a short circuit fault according to the first current command value; Determining a second current command value of the wind farm during the short circuit fault period according to the current limit value, the grid connection point voltage amplitude, the grid connection point voltage rated value and the equivalent active power of the wind farm during the short circuit fault period; Controlling the operation of the sending-end converter station according to the first current command value, and controlling the operation of the wind farm according to the second current command value; Determining the first current command value of the sending-end converter station during the short-circuit fault according to the preset current limit value specifically includes: During the short-circuit fault of the transmission line, the first current command value of the transmission-end converter station is given according to the following formula: Among them, the above is the preset d-axis current limit value of the sending-end converter station; is the preset q-axis current limit value of the sending-end converter station; is the first d-axis current command value of the sending-end converter station; is the first q-axis current command value of the sending-end converter station; The step of determining the current limit value of the wind farm during the short circuit fault period according to the first current command value specifically includes: Importing the first current command value of the sending-end converter station during the short-circuit fault into a first mapping relationship to obtain the output current amplitude of the sending-end converter station during the short-circuit fault, wherein the first mapping relationship is used to represent the corresponding relationship between the first current command value and the output current amplitude; Importing the output current amplitude of the sending-end converter station during the short-circuit fault and the braking coefficient of the differential protection into a second mapping relationship to obtain the current amplitude limit value of the wind farm during the short-circuit fault; The step of determining the second current command value of the wind farm during the short circuit fault according to the current limit value, the grid connection point voltage amplitude, the grid connection point voltage rated value and the equivalent active power of the wind farm during the short circuit fault specifically includes: The grid connection point voltage drop depth coefficient of the wind farm grid connection point is obtained by dividing the grid connection point voltage rated value by the grid connection point voltage amplitude; Determining a rated current command value of the wind farm during a short circuit fault by using the grid connection point voltage rated value, the grid connection point voltage drop depth coefficient and the equivalent active power; The second current command value of the wind farm during the short circuit fault period is determined according to the current amplitude limit value and the rated current command value of the wind farm during the short circuit fault period.

2. The method according to claim 1, characterized in that Before obtaining the preset current limit value of the sending-end converter station during the short-circuit fault, the equivalent active power of the wind farm during the short-circuit fault, the grid connection point voltage amplitude and the grid connection point voltage rated value when a short-circuit fault occurs on the sending line, the method further includes: Obtain the positive sequence voltage of the wind farm grid connection point; If the positive sequence voltage is less than a preset voltage threshold, it is determined that a short circuit fault occurs in the transmission line between the wind farm and the sending-end converter station.

3. The method according to claim 1, characterized in that: The preset current limit value includes a preset d-axis current limit value and a preset q-axis current limit value, the first current command value includes a first d-axis current command value and a first q-axis current command value, and the step of determining the first current command value of the sending-end converter station during a short-circuit fault according to the preset current limit value specifically includes: Using the preset d-axis current limit value as the first d-axis current command value of the sending-end converter during a short-circuit fault; The preset q-axis current limit value is used as the first q-axis current command value of the sending-end converter during a short-circuit fault.

4. The method according to claim 3, characterized in that The first mapping relationship is: Among them, the above is the output current amplitude; is the first q-axis current command value; is the first d-axis current command value; The second mapping relationship is: Among them, the above I wlim is the current limiting value of the wind farm during a short circuit fault; and the above k is the braking coefficient of the differential protection.

5. The method according to claim 1, characterized in that: The rated current command value includes a rated d-axis current command value and a rated q-axis current command value. The step of determining the rated current command value of the wind farm during a short-circuit fault by using the grid connection point voltage rated value, the grid connection point voltage drop depth coefficient, and the rated equivalent active power specifically includes: Importing the grid connection point voltage amplitude into a third mapping relationship to obtain a rated q-axis current command value of the wind farm during a short circuit fault, wherein the third mapping relationship is used to represent a corresponding relationship between the rated q-axis current command value and the grid connection point voltage amplitude; The third mapping relationship is: Among them, the above is the rated q-axis current command value; the above U wf is the voltage amplitude of the grid connection point; Importing the grid connection point voltage drop depth coefficient and the equivalent active power into a fourth mapping relationship to obtain a rated d-axis current command value of the wind farm during a short circuit fault, wherein the fourth mapping relationship is used to represent a corresponding relationship between the rated d-axis current command value, the grid connection point voltage drop depth coefficient and the equivalent active power; The fourth mapping relationship is: Among them, the above is the rated d-axis current command value; the above k vf is the voltage drop depth coefficient of the grid connection point; is the rated equivalent active power.

6. The method according to claim 1, characterized in that The second current command value includes a second d-axis current command value and a second q-axis current command value, and the step of determining the second current command value of the wind farm during the short-circuit fault according to the current limit value and the rated current command value of the wind farm during the short-circuit fault specifically includes: Importing the rated current command value and the current amplitude limit value into a fifth mapping relationship to obtain an amplitude of a second current command value that can be output by the wind farm during a short circuit fault, wherein the fifth mapping relationship is used to represent a correspondence between the amplitude of the second current command value that can be output by the wind farm during a short circuit fault, the rated current command value, and the current amplitude limit value; The fifth mapping relationship is: Among them, the above is the amplitude of the second current command value that can be output by the wind farm during a short circuit fault. is the rated q-axis current command value of the wind farm during a short-circuit fault; is the rated d-axis current command value of the wind farm during a short-circuit fault; the above I wlim is the current limit value of the wind farm during a short circuit fault; Importing the rated current command value into a sixth mapping relationship, and calculating a phase angle of a second current command value that can be output by the wind farm during a short circuit fault, wherein the sixth mapping relationship is used to represent a correspondence between the phase angle of the second current command value that can be output by the wind farm during a short circuit fault and the rated current command value; The sixth mapping relationship is: Among them, the above is the phase angle of the second current command value that can be output by the wind farm during a short circuit fault; Importing the amplitude and the phase angle of the second current command value that can be output by the wind farm during the short circuit fault into a seventh mapping relationship to obtain a second q-axis current command value of the wind farm during the short circuit fault, wherein the seventh mapping relationship is used to represent the corresponding relationship between the second q-axis current command value, the amplitude and the phase angle; The seventh mapping relationship is: Among them, the above is the second q-axis current command value of the wind farm during a short circuit fault; Importing the amplitude and the phase angle of the second current command value that can be output by the wind farm during the short circuit fault into an eighth mapping relationship to obtain the second d-axis current command value of the wind farm during the short circuit fault, wherein the eighth mapping relationship is used to represent the corresponding relationship between the second d-axis current command value, the amplitude and the phase angle; The eighth mapping relationship is: Among them, the above is the second d-axis current command value of the wind farm during a short circuit fault.

7. A fault control device for a wind power flexible direct current grid-connected system, characterized in that: Applicable to a wind power flexible direct current grid-connected system, wherein the wind power flexible direct current grid-connected system comprises a wind farm, a sending-end converter station and a sending line, one end of the sending line is connected to the wind farm, and the other end of the sending line is connected to the sending-end converter station, and the device comprises: An acquisition module, used for acquiring, when a short-circuit fault occurs in the transmission line, a preset current limit value of the transmission-end converter station during the short-circuit fault, an equivalent active power of the wind farm during the short-circuit fault, a grid-connection point voltage amplitude, and a grid-connection point voltage rated value; A first determining module, configured to determine a first current command value of the sending-end converter station during a short-circuit fault according to the preset current limit value; A second determination module, configured to determine a current limit value of the wind farm during a short circuit fault according to the first current command value; a third determination module, configured to determine a second current command value of the wind farm during the short circuit fault period according to the current limit value, the grid connection point voltage amplitude, the grid connection point voltage rated value and the equivalent active power of the wind farm during the short circuit fault period; a control module, configured to control the operation of the sending-end converter station according to the first current command value, and control the operation of the wind farm according to the second current command value; The first determination module is specifically used for: During the short-circuit fault of the transmission line, the first current command value of the transmission-end converter station is given according to the following formula: Among them, the above is the preset d-axis current limit value of the sending-end converter station; is the preset q-axis current limit value of the sending-end converter station; is the first d-axis current command value of the sending-end converter station; is the first q-axis current command value of the sending-end converter station; The second determination module is specifically used for: Importing the first current command value of the sending-end converter station during the short-circuit fault into a first mapping relationship to obtain the output current amplitude of the sending-end converter station during the short-circuit fault, wherein the first mapping relationship is used to represent the corresponding relationship between the first current command value and the output current amplitude; Importing the output current amplitude of the sending-end converter station during the short-circuit fault and the braking coefficient of the differential protection into a second mapping relationship to obtain the current amplitude limit value of the wind farm during the short-circuit fault; The third determination module is specifically used for: The grid connection point voltage drop depth coefficient of the wind farm grid connection point is obtained by dividing the grid connection point voltage rated value by the grid connection point voltage amplitude; Determining a rated current command value of the wind farm during a short circuit fault by using the grid connection point voltage rated value, the grid connection point voltage drop depth coefficient and the equivalent active power; The second current command value of the wind farm during the short circuit fault period is determined according to the current amplitude limit value and the rated current command value of the wind farm during the short circuit fault period.

8. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When a processor executes the computer program, the steps of the method according to any one of claims 1 to 6 are implemented.

9. A readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

Images