Fault control method and device of wind power flexible direct current grid-connected system and electronic equipment

Abstract

The invention discloses a fault control method and device for a wind power flexible direct current grid-connected system and electronic equipment. The method comprises the steps of determining a first current instruction value of a sending-end converter station during a short-circuit fault period according to a preset current amplitude limiting value under the condition that the short-circuit fault of a sending-out line is detected; according to the first current instruction value, determining a current amplitude limiting value of the wind power plant during the short-circuit fault period; determining a second current instruction value of the wind power plant during the short-circuit fault period according to the current amplitude limiting value, the grid-connected point voltage amplitude value, the grid-connected point voltage rated value and the equivalent active power of the wind power plant during the short-circuit fault period; and controlling the sending-end converter station to operate according to the first current instruction value, and controlling the wind power plant to operate according to the second current instruction value. Cooperative control over the wind power plant and the sending-end converter station during the short-circuit fault period is achieved, the phenomenon that a differential protector arranged on a sending-out line fails to operate is avoided, and the safe and stable operation capacity of wind power flexible direct current grid connection under the short-circuit fault of a sending-end power grid is improved.

Description

Technical Field

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

[0002] In the prior art, when a short-circuit fault occurs in the transmission line between the wind farm and the sending-end converter station in the wind power flexible direct current grid-connected system, the current command value of the sending-end converter station or the wind farm is usually adjusted from the perspective of a single station. However, during the short-circuit fault of the transmission line, under the joint influence of the control of the wind farm and the sending-end converter station, the short-circuit current of the transmission line presents a complex controlled characteristic. The current command value is adjusted only from the perspective of a single station without comprehensively considering the coordination between the wind farm and the sending-end converter station. This may cause the sensitivity of the differential protection configured on the sending-end AC line to decrease and cause a refusal to operate, which will have an adverse impact on the safety and stability of the wind power flexible direct current grid-connected system. Summary of the invention

[0003] In view of this, the present application provides a fault control method, device and electronic equipment for a wind power flexible direct current grid-connected system. The main purpose is to solve the technical problem in the prior art that if a short circuit fault occurs in the transmission line, the current command value is adjusted only from the perspective of a single station, without comprehensively considering the coordination between the wind farm and the sending-end converter station, which may cause the sensitivity of the differential protection configured on the sending-end AC line to decrease and cause a refusal to operate.

[0004] According to the first aspect of the present application, a fault control method for a wind power flexible direct current grid-connected system is provided, which is applicable to the 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:

[0005] When a short-circuit fault is detected on 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 voltage amplitude of the grid connection point, and a voltage rating of the grid connection point are obtained;

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

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

[0008] 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 rating and the equivalent active power of the wind farm during the short circuit fault period;

[0009] 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.

[0010] Optionally, in the case where a short circuit fault occurs in the transmission line, before obtaining 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, the method further includes:

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

[0012] If the positive sequence voltage is less than the 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.

[0013] Optionally, 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 the short-circuit fault according to the preset current limit value specifically includes:

[0014] Using 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;

[0015] The preset q-axis current limit value is used as the first q-axis current command value of the sending-end 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] Importing the first current command value of the sending-end converter station during the short-circuit fault into the 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;

[0018] The first mapping relationship is:

[0019]

[0020] 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;

[0021] The output current amplitude of the sending-end converter station during the short-circuit fault and the braking coefficient of the differential protection are introduced 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 I wlim is the current limit value of the wind farm during a short circuit fault; the above k is the braking coefficient of the differential protection.

[0025] Optionally, the step of determining a 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 rating and the equivalent active power of the wind farm during the short circuit fault specifically includes:

[0026] 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;

[0027] Determine the rated current command value of the wind farm during the short-circuit fault period by using the grid connection point voltage rating, grid connection point voltage drop depth coefficient and equivalent active power;

[0028] A second current command value of the wind farm during the short circuit fault period is determined according to the current limit value and the rated current command value of the wind farm during the short circuit fault period.

[0029] Optionally, the rated current command value includes a rated d-axis current command value and a rated q-axis current command value, and the step of determining the rated current command value of the wind farm during the short-circuit fault period 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:

[0030] Importing 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, wherein 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 is the rated q-axis current command value; the above U wf is the voltage amplitude at the grid connection point;

[0034] Importing 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, wherein 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 voltage drop depth coefficient at the grid connection point; 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, 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:

[0039] Importing the rated current command value and the current amplitude limit value into a fifth mapping relationship to obtain the amplitude of the second current command value that can be output by the wind farm during the short circuit fault, wherein the fifth mapping relationship is used to represent the correspondence between the amplitude of the second current command value that can be output by the wind farm during the short circuit fault, the rated current command value, and the current amplitude 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 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;

[0043] Importing the rated current command value into the sixth mapping relationship, calculating the phase angle of the second current command value that the wind farm can output during the short circuit fault, wherein the sixth mapping relationship is used to represent the correspondence 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 a short circuit fault;

[0047] The amplitude and phase angle of the second current command value that can be output by the wind farm during the short circuit fault are introduced into the seventh mapping relationship to obtain the 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;

[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] Importing the amplitude and phase angle of the second current command value that can be output by the wind farm 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, wherein the eighth mapping relationship is used to represent the correspondence 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 a short circuit fault.

[0055] According to the second aspect of the present application, a fault control device for a wind power flexible direct current grid-connected system is provided, which is applicable to the 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:

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

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

[0058] A second determination module is used 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 is used 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;

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

[0061] According to a third aspect of the present application, an electronic device is provided, comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of any one of the methods described in the first aspect when executing the computer program.

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

[0063] By means of the above technical scheme, the present application provides a fault control method, device and electronic device for a wind power flexible direct current grid-connected system, which first determines the first current command value that the sending-end converter station can output during the short-circuit fault of the sending-end power grid based on the current limit value of the sending-end converter station. Thereafter, based on the first current command value of the sending-end 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 short-circuit fault, the wind turbine grid-side converter and the sending-end converter station in the wind farm are switched from external loop control such as DC voltage external loop / AC voltage external loop to single current loop control, and 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, when a short-circuit fault is detected in the transmission line, the fault control scheme only adjusts the current command value from the perspective of a single 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, thereby avoiding the refusal to operate of the differential protector configured on the transmission line, effectively improving the reliability of the differential protection configured on the transmission line of the wind power flexible direct current grid-connected system, and thereby improving the safe and stable operation capability of the wind power flexible direct current grid-connected system under a short-circuit fault in the sending-end power grid.

[0064] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Also, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0066] Figure 1 A schematic diagram of a fault control method for a wind power flexible direct current grid-connected system provided in an embodiment of the present application is shown;

[0067] Figure 2 A schematic flow chart of another fault control method for a wind power flexible direct current grid-connected system provided in an embodiment of the present application is shown;

[0068] Figure 3 A schematic diagram of the structure of a wind power flexible direct current grid-connected system provided in an embodiment of the present application is shown;

[0069] Figure 4 A schematic diagram of fault control of a sending-end converter station provided in an embodiment of the present application is shown;

[0070] Figure 5 A schematic diagram of fault control of a grid-side converter of an inverter-type wind turbine generator system in a wind farm provided by an embodiment of the present application is shown;

[0071] Figure 6 A schematic diagram showing the comparison of differential protection sensitivity simulation waveforms of the wind power flexible direct current grid-connected system using the traditional fault control method and the fault control method provided by the present application respectively when a short circuit fault occurs in the transmission line provided by the embodiment of the present application;

[0072] Figure 7 A structural schematic diagram of a fault control device for a wind power flexible direct current grid-connected system provided in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0073] The exemplary embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present application are shown in the accompanying 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 in order to enable a more thorough understanding of the present application and to fully convey the scope of the present application to those skilled in the art.

[0074] The present application provides a fault control method for a wind power flexible direct current grid-connected system. Figure 1 As shown, the method includes:

[0075] S101. When a short circuit fault is detected in a transmission line, a preset current limit value of a transmission-end converter station during the short circuit fault, an equivalent active power of a wind farm during the short circuit fault, a grid connection point voltage amplitude, and a grid connection point voltage rated value are obtained.

[0076] The fault control method of the wind power flexible direct current grid-connected system provided in the embodiment of the present application is mainly used for the control and protection scenario during the period of grid short-circuit fault of the transmission line between the wind farm and the sending-end converter station in the wind power flexible direct current grid-connected system. The execution subject of the embodiment of the present application is a device or equipment that can control the current command value of the wind power flexible direct current grid-connected system under the short-circuit fault of the transmission grid, which can be specifically set on the server side. The server can automatically detect the short-circuit fault of the transmission line in the wind power flexible direct current grid-connected system, and adjust the current command value of the sending-end converter station and the wind farm when a grid short-circuit fault is detected in the transmission line, so as to realize the coordinated control of the sending-end converter station and the wind farm, so as to improve the reliability of the differential protection of the sending end of the wind power flexible direct current grid-connected system, and further improve the safe and stable operation capability of the wind power flexible direct current grid-connected system under the fault of the sending-end grid.

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

[0078] A differential protector is configured on the transmission line. When a grid short-circuit fault is detected in the transmission line, the differential protector triggers a protective action to prevent system failure. Compared with general wind power grid-connected systems, the short-circuit current characteristics of the wind power flexible direct-current grid-connected system have undergone fundamental changes under the joint action of the wind farm and the sending-end converter station, which may cause the sensitivity of the differential protector configured on the transmission line to decrease, and may even cause a refusal to operate when the sensitivity is less than 1, seriously affecting the safety of the system. Based on the above problems, the present application proposes to adjust the current command values ​​of the sending-end converter station and the wind farm when a grid short-circuit fault is detected in the transmission line, so as to achieve coordinated control of the sending-end converter station and the wind farm, so as to improve the reliability of the differential protection at the sending end of the wind power flexible direct-current grid-connected system, thereby improving the safe and stable operation capability of the wind power flexible direct-current grid-connected system under a sending-end grid fault.

[0079] Specifically, when a short-circuit fault is detected in the transmission line, the preset current limit value of the sending-end converter station during the short-circuit fault of the sending-end power grid and the preset grid connection point rated voltage value of the wind farm grid connection point during the short-circuit fault of the sending-end power grid are first obtained, wherein the wind farm grid connection point is the common connection point (PCC point) on the wind farm side. Further, when a short-circuit fault occurs in the transmission 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 grid connection point voltage rating of the wind farm grid connection point can be set according to the design and specification requirements of the wind power flexible direct current grid connection system during a fault period, and this application does not make specific limitations here.

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

[0082] In this step, when a short circuit fault occurs in the transmission line, the first current command value that can be output by the transmission end converter station during the short circuit fault is determined according to the preset current limit value. The preset current limit value is used to limit the magnitude of the current command value of the transmission end converter station during the short circuit fault to ensure that the differential protector configured on the transmission line can operate reliably.

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

[0084] In this step, during the short-circuit fault, under the joint influence of the wind farm and the control action of the sending-end converter station, the short-circuit current of the transmission line will show complex controlled characteristics, thereby affecting the sensitivity of the differential protector. In order to improve the action performance of the differential protector on the transmission line of the wind power flexible direct current grid-connected system, the current command value that can be output by the sending-end converter station during the short-circuit fault is used to calculate the current limit value that the wind farm can output during the short-circuit fault of the sending-end power grid, to ensure that the differential protector configured on the transmission line can operate reliably, and improve the safe and stable operation capability of the wind power flexible direct current grid-connected system under the short-circuit fault of the sending-end power grid.

[0085] S104, 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.

[0086] In this step, the output current command value output to the wind farm under the real-time condition of the short-circuit fault is calculated based on the grid connection point voltage amplitude, equivalent active power, and grid connection point voltage rating collected in real time during the short-circuit fault of the wind farm. Furthermore, 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 can be output by the wind farm 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] Through the above method, the final second current command value of the wind farm is calculated 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, ensuring that the current of the wind farm will not exceed the safety limit during the short-circuit fault of the sending-end power grid. At the same time, the coordinated control between the wind farm and the sending-end converter station is fully considered to improve the reliability of the differential protection configured on the sending 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 wind turbine grid-side converter in the wind farm is switched to the second current command value.

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

[0091] The fault control method of the wind power flexible direct current grid-connected system provided in the embodiment of the present application first determines the first current command value that the sending-end converter station can output during the short-circuit fault of the sending-end power grid based on the current limit value of the sending-end converter station. Thereafter, based on the first current command value of the sending-end 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 short-circuit fault, the wind turbine network-side converter and the sending-end converter station in the wind farm are switched from the external loop control such as the DC voltage external loop / AC voltage external loop to the 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, when a short-circuit fault is detected in the transmission line, the fault control scheme only adjusts the current command value from the perspective of a single 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, thereby avoiding the refusal to operate of the differential protector configured on the transmission line, effectively improving the reliability of the differential protection configured on the transmission line of the wind power flexible direct current grid-connected system, and thereby improving the safe and stable operation capability of the wind power flexible direct current grid-connected system under a short-circuit fault in the sending-end power grid.

[0092] Further, such as Figure 2 As shown, as a refinement and expansion of the specific implementation 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 a wind power flexible direct current grid-connected system, the method comprising:

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

[0094] S202, determine whether the positive sequence voltage is less than a preset voltage threshold, if so, proceed to step S203, if not, proceed to step S204.

[0095] In steps S201 and S202, by real-time detection of the positive sequence voltage of the wind farm sending-end grid connection point in the system and comparing it with the preset voltage threshold, it is possible to promptly detect whether there is a short circuit fault abnormality in the transmission line, thereby ensuring 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 0.9pu. If it is detected that the positive sequence voltage of the wind farm sending-end grid connection point drops below 0.9pu, it is determined that a short circuit fault occurs in the sending-end AC line (i.e., the sending line) between the wind farm and the sending-end converter station.

[0097] S203: Determine that a short circuit fault occurs in the transmission line between the wind farm and the sending-end converter station.

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

[0099] In steps S203 and S204, if the positive sequence voltage at the wind farm grid connection point 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 direct current grid connection system is switched to the fault ride-through control mode to ensure the safety of the system. Furthermore, if the positive sequence voltage at the wind farm grid connection point 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, the positive sequence voltage at the wind farm grid connection point is continuously detected to ensure the stability of the system operation.

[0100] S205, obtaining 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.

[0101] This step and Figure 1 The method of step S101 shown is the same and will not be repeated 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 period.

[0103] S207: Using 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 period.

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

[0105] Through the above method, the current limit value is used to limit the maximum current of the sending-end converter station during the short-circuit fault of the sending-end power grid, ensuring that the system can still maintain a relatively stable operating state during the short-circuit fault of the sending-end power grid, reducing the impact of instability and volatility on the system.

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

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

[0108] In the embodiment of the present application, optionally, in order to accurately calculate the current limit value of the wind farm during the short circuit fault, in step S208, according to the first current command value, the current limit value of the wind farm during the short circuit fault is determined, specifically including: importing the first current command value of the sending-end converter station during the short circuit fault into the first mapping relationship, and obtaining 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;

[0109] The first mapping relationship is:

[0110]

[0111] 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.

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

[0113] The second mapping relationship is:

[0114]

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

[0116] In this embodiment, the d-axis current command value and the q-axis current command value of the sending-end converter station during the short-circuit fault are introduced into the first mapping relationship, the output current amplitude of the sending-end converter station during the short-circuit fault is calculated, and the actual magnitude of the output current of the sending-end converter station during the short-circuit fault is obtained. Thereafter, the output current amplitude that can be output by the sending-end converter station during the short-circuit fault and the braking coefficient of the differential protection are introduced into the second mapping relationship, and the current limit value of the wind farm during the short-circuit fault is calculated.

[0117] Through the above method, the wind farm current limit value is calculated according to the actual output current amplitude, which can more accurately protect the operating status of the wind power flexible direct current grid-connected system during short-circuit faults, instead of relying on preset values, thereby realizing coordinated regulation of the wind farm and the sending-end converter station, and improving the reliability of the sending-end differential protection of the wind power flexible direct current grid-connected system.

[0118] Optionally, the braking coefficient of the differential protection may range from 0.5 to 0.85.

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

[0120] S210, determining a rated current command value of the wind farm during a short circuit fault by using the grid connection point voltage rating, the grid connection point voltage drop depth coefficient, and the equivalent active power;

[0121] In this step, the grid connection point voltage rating is divided by the grid connection point voltage amplitude to obtain the grid connection point voltage drop depth coefficient of the wind farm. Furthermore, when a short circuit fault occurs in the power grid, the wind power flexible direct current grid connection 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 is detected in the sending-end power grid, the wind power flexible direct current grid connection system is switched to the fault ride-through control mode. At this time, the grid connection point voltage rating, the grid connection point voltage drop depth coefficient and the equivalent active power are used to calculate the rated current command value that meets the real-time conditions and can be output to the wind farm.

[0122] In the embodiment of the present application, optionally, in step S210, the rated current command value of the wind farm during the short circuit fault is determined by using the grid connection point voltage rated value, the grid connection point voltage drop depth coefficient and the equivalent active power, specifically including: importing 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, wherein 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;

[0123] The third mapping relationship is:

[0124]

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

[0126] Further, the grid connection point voltage drop depth coefficient and the equivalent effective power are introduced into the fourth mapping relationship to obtain the rated d-axis current command value of the wind farm during the short circuit fault, wherein 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;

[0127] The fourth mapping relationship is:

[0128]

[0129] Among them, the above is the rated d-axis current command value; the above k vfis the voltage drop depth coefficient at the grid connection point; is the rated equivalent effective power.

[0130] In this embodiment, the rated current command value of the wind farm during the short circuit fault includes a rated d-axis current command value and a rated q-axis current command value. First, the grid connection point voltage amplitude is imported into the third mapping relationship to calculate the rated q-axis current command value of the wind farm during the short circuit fault. Thereafter, the grid connection point voltage drop depth coefficient and the equivalent effective power are imported 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 a second current command value of the wind farm during the short circuit fault period according to the current limit value and the rated current command value of the wind farm during the short circuit fault period.

[0132] In this step, in order to coordinate the current control instructions 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 protector configured on the sending line, the output current limit value and the rated current instruction value of the wind farm during the short-circuit fault are used to calculate the final second current instruction value of the wind farm during the short-circuit fault.

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

[0134] Importing the rated current command value and the current amplitude limit value into a fifth mapping relationship to obtain the amplitude of the second current command value that can be output by the wind farm during the short circuit fault, wherein the fifth mapping relationship is used to represent the correspondence between the amplitude of the second current command value that can be output by the wind farm during the short circuit fault, the rated current command value, and the current amplitude limit value;

[0135] The fifth mapping relationship is:

[0136]

[0137] Among them, the above is the amplitude of the second current command value that the wind farm can output 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.

[0138] Further, the rated current command value is introduced 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, wherein the sixth mapping relationship is used to represent the correspondence 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:

[0140]

[0141] Among them, the above It is the phase angle of the second current command value that the wind farm can output during a short circuit fault.

[0142] Further, the amplitude and phase angle of the second current command value that can be output by the wind farm during the short circuit fault are introduced into the seventh mapping relationship to obtain the 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 correspondence between the second q-axis current command value, the amplitude and the phase angle;

[0143] The seventh mapping relationship is:

[0144]

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

[0146] Further, the amplitude and phase angle of the second current command value that can be output by the wind farm during the short circuit fault are introduced into the 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;

[0147] The eighth mapping relationship is:

[0148]

[0149] Among them, the above is the second d-axis current command value of the wind farm during a 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 introduced into the fifth mapping relationship, and the amplitude of the current command value that the wind farm can output during the short circuit fault is calculated. Further, the rated d-axis current command value and the rated q-axis current command value are introduced into the sixth mapping relationship, and the phase angle of the current command value that the wind farm can output during the short circuit fault is calculated. Thereafter, the amplitude and phase angle of the current command value that the wind turbine can output during the short circuit fault are introduced into the seventh mapping relationship, and the second q-axis current command value of the wind farm during the short circuit fault is calculated. Finally, the amplitude and phase angle of the current command value of the wind farm during the short circuit fault are introduced into the seventh mapping relationship, and the second d-axis current command value of the wind farm during the short circuit fault is calculated.

[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 and Figure 1 The method of step S105 shown is the same and will not be repeated here.

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

[0154] S1: The wind power flexible direct current grid-connected system adopts the motor convention, which stipulates that the q-axis of the dq-axis rotating coordinate system is ahead of the d-axis. When the positive sequence voltage at the wind farm grid-connected point is detected to drop below 0.9pu, the wind turbine grid-side converter and the sending-end converter station in the wind farm are switched to single current loop control, that is, during the short-circuit fault, the DC voltage outer loop / AC voltage outer loop and other outer loop controls are disconnected, and the current loop command value is switched to the current command value during the fault ride-through control period.

[0155] S2: 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:

[0156]

[0157] 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.

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

[0159]

[0160] Among them, the above is the rated q-axis current command value; the above U wf is the voltage amplitude at the grid connection point; is the rated d-axis current command value; the above k vf is the voltage drop depth coefficient at the grid connection point; is the rated equivalent effective power; the above U wN It is the grid connection point voltage rating.

[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] 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 above I wlim is the current limit value of the wind farm during a 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 based on the output current command value and the current limit value of the wind farm according to the following formula:

[0165]

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

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

[0168] Further, as Figure 1 The specific implementation of the method, the embodiment of the present application provides a fault control device 300 of a wind power flexible direct current grid-connected system, which is applicable to the wind power flexible direct current grid-connected system, wherein the wind power flexible direct current grid-connected system includes 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, such as Figure 7 As 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 used to 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 grid-connection point voltage amplitude and the grid-connection point voltage rated value when a short-circuit fault is detected on the transmission line;

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

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

[0172] The third determination module 304 is used to determine the 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;

[0173] The control module 305 is used to control the operation of the sending-end converter station according to the first current command value, and to 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 also used to acquire the positive sequence voltage of the wind farm grid connection point.

[0175] In specific application scenarios, such as Figure 7 As shown, the device further includes: a judging module 306 and a fourth determining module 307 .

[0176] A judgment module 306, used for comparing the positive sequence voltage with a preset voltage threshold;

[0177] The fourth determination module 307 is used to determine that a short circuit fault occurs in the transmission line between the wind farm and the sending-end converter station if the positive sequence voltage is less than a 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, the first current command value includes a first d-axis current command value and a first q-axis current command value, and the first current command value of the sending-end converter station during a short-circuit fault, the first determination module 302 is specifically used to:

[0179] Using 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] The preset q-axis current limit value is used as the first q-axis current command value of the sending-end converter during the short-circuit fault.

[0181] In a specific application scenario, in order to determine the current limit value of the wind farm during a short circuit fault, the second determination module 303 is specifically used to:

[0182] Importing the first current command value of the sending-end converter station during the short-circuit fault into the 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;

[0183] The first mapping relationship is:

[0184]

[0185] 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;

[0186] The output current amplitude of the sending-end converter station during the short-circuit fault and the braking coefficient of the differential protection are introduced 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 I wlim is the current limit value of the wind farm during a short circuit fault; the above k is the braking coefficient of the differential protection.

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

[0191] 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;

[0192] Determine the rated current command value of the wind farm during the short-circuit fault period by using the grid connection point voltage rating, grid connection point voltage drop depth coefficient and equivalent active power;

[0193] A second current command value of the wind farm during the short circuit fault period is determined according to the current limit value and the rated current command value of the wind farm during the short circuit fault period.

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

[0195] Importing 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, wherein 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;

[0196] The third mapping relationship is:

[0197]

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

[0199] Importing 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, wherein 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;

[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 voltage drop depth coefficient at the grid connection point; 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. In order to determine the second current command value of the wind farm during a short circuit fault, the third determination module 304 is further specifically used to:

[0204] Importing the rated current command value and the current amplitude limit value into a fifth mapping relationship to obtain the amplitude of the second current command value that can be output by the wind farm during the short circuit fault, wherein the fifth mapping relationship is used to represent the correspondence between the amplitude of the second current command value that can be output by the wind farm during the short circuit fault, the rated current command value, and the current amplitude 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 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;

[0208] Importing the rated current command value into the sixth mapping relationship, calculating the phase angle of the second current command value that the wind farm can output during the short circuit fault, wherein the sixth mapping relationship is used to represent the correspondence 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 a short circuit fault;

[0212] The amplitude and phase angle of the second current command value that can be output by the wind farm during the short circuit fault are introduced into the seventh mapping relationship to obtain the 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;

[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] Importing the amplitude and phase angle of the second current command value that can be output by the wind farm 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, wherein the eighth mapping relationship is used to represent the correspondence between the second d-axis current command value, the amplitude and the 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 a short circuit fault.

[0220] The fault control device 300 of the wind power flexible direct current grid-connected system provided in the embodiment of the present application first determines the first current command value that the sending-end converter station can output during the short-circuit fault of the sending-end power grid based on the current limit value of the sending-end converter station. Thereafter, based on the first current command value of the sending-end 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 short-circuit fault, the wind turbine network-side converter and the sending-end converter station in the wind farm are switched from the external loop control such as the DC voltage external loop / AC voltage external loop to the single current loop control, and 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, when a short-circuit fault is detected in the transmission line, the fault control scheme only adjusts the current command value from the perspective of a single 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, thereby avoiding the refusal to operate of the differential protector configured on the transmission line, effectively improving the reliability of the differential protection configured on the transmission line of the wind power flexible direct current grid-connected system, and thereby improving the safe and stable operation capability of the wind power flexible direct current grid-connected system under a short-circuit fault in the sending-end power grid.

[0221] In an exemplary embodiment, the present application further provides an electronic device, including a memory and a processor. The memory stores a computer program, and the processor is used to execute the program stored in the memory and execute the fault control method of the wind power flexible direct current grid-connected 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. When the computer program is executed by a processor, the steps of the fault control method of the wind power flexible direct current grid-connected system are implemented.

[0223] Through the description of the above implementation methods, 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, which 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 a number of instructions for enabling an electronic device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each implementation scenario of the present application.

[0224] Those skilled in the art will appreciate that the accompanying drawings are merely schematic diagrams of a preferred implementation scenario, and the modules or processes in the accompanying drawings are not necessarily required for implementing the present application.

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

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

[0227] The above disclosure only discloses several specific implementation scenarios of the present application. However, the present application is not limited thereto, and any changes that can be conceived by technicians in this field should fall within the scope of protection 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; The sending-end 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.

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 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; 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; 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 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 4, characterized in that 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.

6. The method according to claim 5, 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 effective 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 effective 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 effective power.

7. The method according to claim 5, 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.

8. 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 is used to control the operation of the sending-end converter station according to the first current command value, and to control the operation of the wind farm according to the second current command value.

9. 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 7 are implemented.

10. 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 7 are implemented.

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