A fault ride-through method and apparatus

Abstract

The application relates to the technical field of new energy, and discloses a fault ride-through method and device. The method is applied to a new energy grid-connected system through flexible direct-current power transmission, and comprises the following steps: in the case that a fault occurs in a receiving-end power grid, a flexible direct-current power transmission system controls a sending-end converter station and a sending-end new energy unit to indicate that a fault has occurred in the receiving-end power grid; a direct-current voltage value of a sending-end flexible direct-current converter valve at a current time is acquired; a first difference between the direct-current voltage value and a rated direct-current voltage value is determined; and according to the first difference, the sending-end new energy unit and the sending-end flexible direct-current converter valve are controlled, so that the direct-current voltage value is reduced to below a preset voltage threshold. Through the application, in the case that a fault occurs in the receiving end, surplus power can be consumed by controlling the sending-end new energy unit and the sending-end flexible direct-current converter valve without configuring a centralized energy consumption device, and the receiving-end power grid fault ride-through is realized.

Description

Technical Field

[0001] This invention relates to the field of new energy technology, specifically to a fault ride-through method and apparatus. Background Technology

[0002] Currently, in offshore wind power flexible DC transmission systems, when a fault occurs in the onshore AC grid, the power from offshore wind power cannot be transmitted to the receiving-end grid via the flexible DC system, resulting in a rise in the DC voltage of the flexible DC transmission system due to the surplus power from the wind power. To avoid equipment damage caused by overvoltage, the surplus power during the fault period needs to be dissipated to achieve fault ride-through. Existing technology achieves fault ride-through by configuring centralized energy dissipation devices at onshore converter stations to dissipate the surplus power during grid faults. However, configuring centralized energy dissipation devices is costly; for example, the cost of centralized energy dissipation devices configured in a 3GW offshore wind power flexible DC transmission project under construction is close to 100 million yuan. Therefore, how to achieve fault ride-through at a low cost in the event of an onshore AC grid fault is a current focus. Summary of the Invention

[0003] In view of this, the present invention provides a fault ride-through method and apparatus to solve the problem of fault ride-through when the receiving end power grid is faulty.

[0004] In a first aspect, the present invention provides a fault ride-through method applied to a new energy grid-connected system via flexible DC transmission. The system includes a sending-end new energy power station, a sending-end AC line, a flexible DC transmission system, and a receiving-end power grid. The sending-end new energy power station, the sending-end AC line, the flexible DC transmission system, and the receiving-end power grid are connected sequentially. The sending-end new energy power station includes at least one sending-end new energy generating unit. The flexible DC transmission system includes a sending-end converter station, a DC line, and a receiving-end converter station. The sending-end converter station includes a sending-end flexible DC converter valve and a sending-end AC bus. The sending-end new energy generating unit is connected to the sending-end converter station via the sending-end AC line and the sending-end AC bus. The method includes:

[0005] In the event of a fault in the receiving-end power grid, the control system for flexible DC transmission indicates that a fault has occurred in the receiving-end power grid at the sending-end converter station and the sending-end renewable energy unit.

[0006] Obtain the DC voltage value of the sending-end flexible DC converter valve at the current moment;

[0007] Determine the first difference between the DC voltage value and the rated DC voltage value;

[0008] Based on the first difference, control the sending-end new energy unit and the sending-end flexible DC converter valve to reduce the DC voltage value to below the preset voltage threshold.

[0009] The method provided in this embodiment, compared to the related technology that uses centralized energy dissipation devices to dissipate surplus power during a fault in the receiving-end grid, dissipates surplus power by controlling the sending-end renewable energy units and the sending-end flexible DC converter valve. This eliminates the need for energy dissipation devices, allowing the DC voltage of the flexible DC transmission system to drop below a preset voltage threshold, reducing equipment costs for fault ride-through, and ensuring reliable system operation.

[0010] In one optional implementation, the system includes a distributed energy consumption device, the receiving-end converter station includes a receiving-end flexible DC converter valve, and the distributed energy consumption device is configured in the sending-end flexible DC converter valve or the receiving-end flexible DC converter valve; in the event of a fault in the receiving-end power grid, after indicating that a fault has occurred in the sending-end converter station and the sending-end renewable energy unit, the method further includes:

[0011] Obtain the average voltage value of each submodule in the flexible DC converter valve configured with distributed energy consumption device;

[0012] When the average voltage value is greater than the average voltage threshold, the distributed energy consumption device is controlled to keep the average voltage value below the average voltage threshold for a first preset time period.

[0013] In one optional implementation, in the event of a fault in the receiving-end power grid, the control system for the flexible DC transmission line indicates that a fault has occurred in the receiving-end power grid of the sending-end renewable energy unit, including:

[0014] The sending-end flexible DC converter valve is controlled by AC voltage amplitude and frequency control (V / F control) to increase the angular frequency of the sending-end AC bus to a preset angular frequency, so as to indicate that the sending-end new energy unit has experienced a receiving-end grid fault.

[0015] or;

[0016] Obtain the current three-phase AC voltage reference command of the sending-end flexible DC converter valve; based on the current three-phase AC voltage reference command, superimpose a three-phase AC voltage reference command of a preset frequency to obtain the superimposed three-phase AC voltage reference command; according to the superimposed three-phase AC voltage reference command, control the sending-end flexible DC converter valve to indicate that a receiving-end grid fault has occurred in the sending-end new energy unit.

[0017] In one alternative implementation, the new energy unit includes a grid-side converter;

[0018] When the phase-locked loop of the grid-side converter tracks to the preset angular frequency and continues to run for a second preset time, the control unit of the new energy unit determines that a fault has occurred in the receiving-end grid.

[0019] or,

[0020] When the current content of the three-phase AC current output by the grid-side converter exceeds the preset threshold at a preset frequency, and continues to operate for a third preset duration, the control unit determines that a fault has occurred in the receiving-end grid.

[0021] In one optional implementation, the system further includes communication equipment; in the event of a fault in the receiving-end power grid, it instructs the sending-end renewable energy generating units to experience a fault in the receiving-end power grid, including:

[0022] The communication equipment indicates that a fault has occurred in the receiving-end power grid of the sending-end renewable energy unit.

[0023] In one optional implementation, based on the first difference, the sending-end renewable energy unit and the sending-end flexible DC converter valve are controlled to reduce the DC voltage value below a preset voltage threshold, including:

[0024] Based on the first difference, determine the change value of the reference command amplitude of the three-phase AC base frequency voltage corresponding to the sending-end flexible DC converter valve;

[0025] The sending-end flexible DC converter valve is controlled based on the amplitude change value of the three-phase AC base frequency voltage reference command.

[0026] Obtain the amplitude of the three-phase AC base frequency voltage at the grid connection point corresponding to the sending-end new energy unit;

[0027] The active current reference command change value is determined based on the second difference between the amplitude of the three-phase AC base frequency voltage at the grid connection point and the rated value of the three-phase AC base frequency voltage at the grid connection point.

[0028] Control the sending-end renewable energy units based on the changes in the active current reference command value.

[0029] In one optional implementation, the change in the amplitude of the three-phase AC base frequency voltage reference command corresponding to the sending-end flexible DC converter valve is determined based on the first difference, including:

[0030] Based on the first difference and the preset mapping relationship between the first difference and the amplitude change value of the reference command for the three-phase AC base frequency voltage, the amplitude change value of the reference command for the three-phase AC base frequency voltage is determined for the sending-end flexible DC converter valve.

[0031] In one optional implementation, the active current reference command change value is determined based on a second difference between the amplitude of the three-phase AC base frequency voltage at the grid connection point and the rated value of the three-phase AC base frequency voltage at the grid connection point, including:

[0032] The active current reference command change value is determined based on the second difference between the amplitude of the three-phase AC base frequency voltage at the grid connection point and the rated value of the three-phase AC base frequency voltage at the grid connection point, and the preset mapping relationship between the second difference and the active current reference command change value.

[0033] In one optional implementation, controlling the sending-end renewable energy unit based on the change in active current reference command includes:

[0034] Turn off the DC voltage outer loop control of the grid-side converter of the sending-end new energy unit;

[0035] Obtain the active current reference command from the grid-side converter of the new energy unit before the fault occurs;

[0036] The sending-end renewable energy units are controlled based on the changes in the active current reference command and the active current reference command.

[0037] Secondly, this invention provides a fault ride-through device applied to a new energy grid-connected system via flexible DC transmission. The system includes a sending-end new energy power station, a sending-end AC line, a flexible DC transmission system, and a receiving-end power grid. The sending-end new energy power station, the sending-end AC line, the flexible DC transmission system, and the receiving-end power grid are connected sequentially. The sending-end new energy power station includes at least one sending-end new energy generating unit. The flexible DC transmission system includes a sending-end converter station, a DC line, and a receiving-end converter station. The sending-end converter station includes a sending-end flexible DC converter valve and a sending-end AC bus. The sending-end new energy generating unit is connected to the sending-end converter station via the sending-end AC line and the sending-end AC bus. The device includes:

[0038] The indicator module is used to control the flexible DC transmission system to indicate that a fault has occurred in the receiving-end converter station and the sending-end renewable energy unit in the event of a fault in the receiving-end power grid.

[0039] The acquisition module is used to acquire the DC voltage value of the sending-end flexible DC converter valve at the current moment;

[0040] The determination module is used to determine the first difference between the DC voltage value and the rated DC voltage value;

[0041] The control module is used to control the sending-end new energy unit and the sending-end flexible DC converter valve according to the first difference, so that the DC voltage value drops below the preset voltage threshold.

[0042] Thirdly, the present invention provides a computer device, comprising: a memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the computer instructions to perform the fault-traversal method of the first aspect or any corresponding embodiment described above.

[0043] Fourthly, the present invention provides a computer-readable storage medium storing computer instructions for causing a computer to perform the fault-traversal method of the first aspect or any corresponding embodiment thereof.

[0044] Fifthly, the present invention provides a computer program product, including computer instructions for causing a computer to execute the fault-traversal method of the first aspect or any corresponding embodiment thereof. Attached Figure Description

[0045] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0046] Figure 1 This is a schematic diagram of the structure of a new energy flexible DC transmission system according to an embodiment of the present invention;

[0047] Figure 2 This is a flowchart of a fault-crossing method according to an embodiment of the present invention;

[0048] Figure 3 This is a schematic diagram of the structure of a new energy generator unit at the sending end according to an embodiment of the present invention;

[0049] Figure 4 This is a schematic diagram of a new energy grid-connected system via flexible DC transmission according to an embodiment of the present invention;

[0050] Figure 5 This is a schematic diagram of a submodule circuit with a power-consuming branch according to an embodiment of the present invention;

[0051] Figure 6 This is a control block diagram of the sending-end flexible DC converter valve when a fault occurs in the receiving-end power grid of the sending-end renewable energy unit, according to an embodiment of the present invention.

[0052] Figure 7 This is a control block diagram according to an embodiment of the present invention, which uses a flexible DC converter valve at the sending end to increase the angular frequency of the AC bus at the sending end to a preset angular frequency in order to indicate that a fault has occurred in the receiving end power grid of the sending end new energy unit.

[0053] Figure 8 This is a control block diagram of an embodiment of the present invention, which uses superimposed three-phase AC voltage reference commands to indicate a fault in the receiving-end power grid of the sending-end new energy unit;

[0054] Figure 9 This is a control block diagram of the new energy unit (grid-side converter) when a fault occurs in the receiving-end power grid according to an embodiment of the present invention;

[0055] Figure 10 This is a schematic diagram illustrating the determination of the active current reference command change value according to an embodiment of the present invention;

[0056] Figure 11 This is a structural block diagram of a fault-crossing device according to an embodiment of the present invention;

[0057] Figure 12 This is a schematic diagram of the structure of a computer device according to an embodiment of the present invention. Detailed Implementation

[0058] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0059] Figure 1 This is a schematic diagram of a flexible DC power transmission system for a new energy source. Figure 1 In this system, the sending-end renewable energy power plant, the sending-end converter station (including the sending-end flexible DC converter valve), the receiving-end converter station, and the receiving-end power grid are connected sequentially. The receiving-end converter station, in addition to containing the receiving-end flexible DC converter valve, also has a centralized energy dissipation device on the DC side. This energy dissipation device dissipates surplus power generated during a fault in the receiving-end power grid, thus enabling fault ride-through. However, configuring this energy dissipation device is costly; for example, the centralized energy dissipation device configured for a 3GW offshore wind power flexible DC transmission project costs nearly 100 million yuan. Therefore, how to achieve fault ride-through at low cost in the event of a fault in the onshore AC power grid is a current focus.

[0060] In view of this, embodiments of this application provide a fault-crossing method to achieve fault-crossing at low cost.

[0061] It should be noted that the fault-traversal method provided in this embodiment of the invention can be executed by a fault-traversal device. This device can be implemented as part or all of an electronic device through software, hardware, or a combination of both. The electronic device can be a server or a terminal. In this embodiment, the server can be a single server or a server cluster composed of multiple servers. The terminal can be a smartphone, personal computer, tablet computer, wearable device, or other intelligent hardware device such as an intelligent robot. The following method embodiments will use an electronic device as an example for explanation.

[0062] According to an embodiment of the present invention, a fault-crossing method embodiment is provided. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than that shown here.

[0063] This embodiment provides a fault-crossing method that can be used in the aforementioned electronic devices, such as servers. Figure 2 This is a flowchart of a fault ride-through method according to an embodiment of the present invention. The method is applied to a new energy grid-connected system via flexible DC transmission. The system includes a sending-end new energy power station, a sending-end AC line, a flexible DC transmission system, and a receiving-end power grid. The sending-end new energy power station, the sending-end AC line, the flexible DC transmission system, and the receiving-end power grid are connected sequentially. The sending-end new energy power station includes at least one sending-end new energy generating unit. The flexible DC transmission system includes a sending-end converter station, a DC line, and a receiving-end converter station. The sending-end converter station includes a sending-end flexible DC converter valve and a sending-end AC bus. The sending-end new energy generating unit is connected to the sending-end converter station through the sending-end AC line and the sending-end AC bus.

[0064] Specifically, the receiving-end power grid refers to the target power grid that receives and consumes renewable energy power. The receiving-end power grid includes, but is not limited to, substations, transmission lines, etc.

[0065] Sending-end renewable energy power stations refer to renewable energy power stations on the sending side, such as offshore wind farms and photovoltaic power stations. This application does not specifically limit the sending-end renewable energy; taking an offshore wind farm as an example, the renewable energy units in the sending-end renewable energy power station are wind turbine units. In the following embodiments, taking an offshore wind farm as an example, the fault ride-through method provided in the embodiments of this application will be illustrated by way of example.

[0066] Receiving-end converter stations are used to convert DC power into AC power and connect it to the receiving-end power grid. Examples of receiving-end converter stations include, but are not limited to, flexible DC converter valves.

[0067] The sending-end converter station is a converter device that connects the sending-end renewable energy power plant to the DC line. Taking offshore wind power as an example, the sending-end converter station is an offshore converter station, which is connected to the sending-end converter station via a DC submarine cable.

[0068] like Figure 2 As shown, the process includes the following steps:

[0069] S101, in the event of a fault in the receiving-end power grid, the control system of the flexible DC transmission system indicates that a fault has occurred in the receiving-end power grid at the sending-end converter station and the sending-end renewable energy unit.

[0070] In one possible implementation, when a fault occurs in the receiving-end grid, the receiving-end converter station is controlled to indicate to the sending-end converter station that a fault has occurred in the receiving-end grid.

[0071] In one possible implementation, when a fault occurs in the receiving-end grid, the control system of the flexible DC transmission line indicates that a fault has occurred in the receiving-end grid of the sending-end renewable energy unit.

[0072] S102, obtain the DC voltage value of the current sending-end flexible DC converter valve.

[0073] S103, determine the first difference between the DC voltage value and the DC voltage rating.

[0074] Specifically, the first difference is obtained by subtracting the current DC voltage value from the rated DC voltage value. The severity of the voltage overshoot is determined by the first difference, providing a "quantitative basis" for subsequent control (the larger the difference, the more severe the fault impact, and the stronger the control measures required).

[0075] S104, based on the first difference, controls the sending-end new energy unit and the sending-end flexible DC converter valve to reduce the DC voltage value to below the preset voltage threshold.

[0076] The preset voltage threshold and DC voltage rating can be set according to actual conditions, and are not limited here.

[0077] In one possible implementation, such as Figure 3 As shown, each sending-end renewable energy unit includes a power generation unit, a turbine-side converter, a grid-side converter, and a wind turbine-integrated energy dissipation device. In S104 above, the surplus power dissipation during onshore AC grid faults is completed by utilizing the energy dissipation device configured on the wind turbine itself in each sending-end renewable energy unit.

[0078] The method provided in this application embodiment, compared to the related technology that dissipates surplus power during a fault by configuring a centralized energy dissipation device in the event of a power grid fault at the receiving end, dissipates surplus power by controlling the sending-end renewable energy unit and the sending-end flexible DC converter valve. This eliminates the need for additional centralized energy dissipation devices to reduce the DC voltage value of the sending-end flexible DC converter valve to below a preset voltage threshold, thereby reducing the equipment cost for fault ride-through and ensuring reliable system operation.

[0079] In some embodiments, the system further includes a distributed energy dissipation device, wherein the receiving-end converter station includes a receiving-end flexible DC converter valve, and the distributed energy dissipation device is configured in the sending-end flexible DC converter valve or the receiving-end flexible DC converter valve.

[0080] Figure 4This is a schematic diagram of a new energy power transmission and grid connection system via flexible DC transmission. In this system, the sending-end new energy power plant, the sending-end AC line, the sending-end converter station (including the sending-end AC bus and the sending-end flexible DC converter valve), the DC submarine cable, the receiving-end converter station (including the receiving-end flexible DC converter valve), and the receiving-end power grid are connected sequentially. Distributed energy consumption devices are configured in the receiving-end flexible DC converter valve. The receiving-end flexible DC converter valve containing distributed energy consumption devices includes multiple sub-modules with energy consumption branches (such as…). Figure 4 SM1 in the middle). Figure 5 This is a circuit diagram of a submodule with a power-consuming branch. For example... Figure 5 As shown, each submodule with a power dissipation branch includes fully controlled power semiconductor devices (T1, T2, T3), anti-parallel diodes (D1, D2), and a submodule capacitor C. T3 and the resistor connected to it constitute the power dissipation branch of the submodule.

[0081] In the event of a fault in the receiving-end power grid, after instructing the sending-end converter station and the sending-end renewable energy units to experience a fault in the receiving-end power grid, the method provided in this application embodiment further includes the following:

[0082] First, obtain the average voltage value of each submodule in the flexible DC converter valve configured with distributed energy consumption device.

[0083] Specifically, the average voltage value of each submodule in the flexible DC converter valve can reflect the voltage balance of the submodule and the operating status of the converter valve. When the receiving end of the power grid fails, the power transmission of the converter valve is obstructed, and the voltage of the submodule rises due to overcharging.

[0084] Then, when the average voltage value is greater than the average voltage threshold, the distributed energy consumption device is controlled to keep the average voltage value below the average voltage threshold for a first preset time period.

[0085] Specifically, the average voltage threshold refers to the pre-set safe upper limit of the average voltage of the submodule to prevent damage due to excessive voltage in the flexible DC converter valve submodule. The average voltage threshold can be determined based on the rated withstand voltage of the submodule, etc., and this application embodiment does not specifically limit it.

[0086] The first preset duration can be determined based on the characteristics of the distributed energy consumption device. For example, the first preset duration can be determined based on the longest duration for which the distributed energy consumption device can keep the average voltage value at the average voltage threshold.

[0087] In this embodiment, since it takes a certain amount of time for the sending-end renewable energy unit to experience a fault in the receiving-end power grid, and considering that the distributed energy dissipation device in the flexible DC converter valve can achieve fault ride-through in a short time (approximately 100ms~200ms) (the fault ride-through time of the receiving-end power grid is typically 1500ms), the distributed energy dissipation device in the flexible DC converter valve simultaneously dissipates surplus power while the sending-end renewable energy unit experiences a fault in the receiving-end power grid, achieving a seamless connection between short-term and long-term fault ride-through. This leverages both the "fast response" advantage of the distributed device and the "long duration" characteristic of the sending-end renewable energy unit, perfectly matching the fault ride-through requirements of the receiving-end power grid.

[0088] In some embodiments, in S101 above, a receiving-end grid fault is indicated to the sending-end renewable energy unit in the following manner:

[0089] The sending-end flexible DC converter valve is controlled by AC voltage amplitude and frequency control (V / F control) to increase the angular frequency of the sending-end AC bus to a preset angular frequency, so as to indicate that the sending-end new energy unit has experienced a receiving-end grid fault.

[0090] Furthermore, the new energy generating unit includes a grid-side converter. The grid-side converter is the "core component of the power interface" between the new energy generating unit (such as wind turbines and photovoltaic power generation systems) and the sending-end AC bus. It is responsible for converting the electrical energy generated by the unit (such as the frequency-converted AC power on the wind turbine rotor side and the DC power from the photovoltaic modules) into AC power that matches the AC bus voltage and frequency, while also undertaking functions such as "voltage regulation, reactive power compensation, and frequency tracking." The method provided in this application embodiment also includes the following:

[0091] When the phase-locked loop of the grid-side converter tracks to the preset angular frequency and continues to run for a second preset duration, the control unit determines that a fault has occurred in the receiving-end grid.

[0092] Specifically, the phase-locked loop is a "frequency and phase tracking module" integrated into the grid-side converter control unit. By acquiring the voltage signal at the grid connection point in real time, it calculates and tracks the angular frequency of the AC bus at the offshore sending end, and outputs a reference signal synchronized with the bus frequency to ensure that the AC power output by the grid-side converter is "synchronized" with the bus, thus avoiding power surges caused by frequency asynchrony.

[0093] The preset angular frequency can be set according to the actual situation, and this application embodiment does not make specific limitations on it.

[0094] In this embodiment of the application, the angular frequency of the sending-end AC bus is used as a signal to indicate that a fault has occurred in the receiving-end power grid of the sending-end renewable energy unit. When the sending-end renewable energy unit receives the signal, that is, when the sending-end renewable energy unit tracks to the preset angular frequency through the phase-locked loop in the grid-side converter, it is determined that a fault has occurred in the receiving-end power grid.

[0095] In other embodiments, in S101 above, the sending-end renewable energy unit is indicated to have a receiving-end grid fault in the following manner:

[0096] First, obtain the current three-phase AC voltage reference command for the sending-end flexible DC converter valve.

[0097] Specifically, the current three-phase AC voltage reference command is the "reference control command" output by the control unit of the sending-end flexible DC converter valve during normal operation. It is used to adjust the three-phase voltage of the sending-end AC bus and includes parameters such as voltage amplitude, fundamental frequency, and phase, which directly determine the output voltage characteristics of the converter valve.

[0098] Then, based on the current three-phase AC voltage reference command, a three-phase AC voltage reference command of a preset frequency is superimposed to obtain the superimposed three-phase AC voltage reference command.

[0099] Finally, based on the superimposed three-phase AC voltage reference command, the sending-end flexible DC converter valve is controlled to indicate that a receiving-end grid fault has occurred in the sending-end renewable energy unit.

[0100] Furthermore, the new energy unit includes a grid-side converter; the method provided in this application embodiment also includes the following:

[0101] When the current content of the three-phase AC current output by the grid-side converter exceeds the preset threshold at a preset frequency, and continues to operate for a third preset duration, the control unit determines that a fault has occurred in the receiving-end grid.

[0102] The preset frequency can be set according to the actual situation, and no specific limit is made here.

[0103] In this embodiment of the application, a three-phase AC voltage reference command of a preset frequency is superimposed on the current three-phase AC voltage reference command. The superimposed three-phase AC voltage reference command of the preset frequency is used as a signal to indicate that the receiving end grid of the sending-end new energy unit has a fault. When the sending-end new energy unit detects that the current content of the preset frequency exceeds the preset threshold and is maintained for a third preset time, it is determined that the receiving end grid has a fault.

[0104] In some embodiments, the system also includes communication equipment.

[0105] Specifically, in a flexible DC transmission grid-connected system for new energy sources, communication equipment refers to the collective term for hardware devices and communication links specifically designed to achieve "rapid transmission of fault signals from the receiving-end power grid." It must possess low latency, high reliability, and anti-interference characteristics, directly connecting the receiving-end converter station, the sending-end flexible DC converter valve, and the sending-end new energy power station. It is the core carrier for "point-to-point" transmission of fault signals. For example, hardware devices include, but are not limited to, fiber optic transceivers and signal transceivers, while communication links can be single-mode fiber, multi-mode fiber, etc.

[0106] In the event of a fault in the receiving-end power grid, the sending-end renewable energy generating units are instructed to indicate a fault in the receiving-end power grid. The specific steps include the following:

[0107] The communication equipment indicates that a fault has occurred in the receiving-end power grid of the sending-end renewable energy unit.

[0108] Compared to the aforementioned indirect indication methods (such as using the angular frequency of the sending-end AC bus and a three-phase AC voltage reference command with a preset frequency), in this embodiment of the application, the fault signal of the receiving-end grid is transmitted directly to the sending-end renewable energy power station through communication equipment, which can significantly shorten the transmission time of the fault signal.

[0109] In some embodiments, based on the first difference, the sending-end renewable energy unit and the sending-end flexible DC converter valve are controlled to reduce the DC voltage value below a preset voltage threshold, specifically including the following steps:

[0110] a1. Based on the first difference, determine the change value of the reference command amplitude of the three-phase AC base frequency voltage corresponding to the sending-end flexible DC converter valve.

[0111] In one possible implementation, the three-phase AC base frequency voltage reference command amplitude change value corresponding to the sending-end flexible DC converter valve is determined based on the first difference and a preset mapping relationship between the first difference and the three-phase AC base frequency voltage reference command amplitude change value.

[0112] a2 controls the sending-end flexible DC converter valve based on the amplitude change value of the three-phase AC base frequency voltage reference command.

[0113] In one possible implementation, the feed-end flexible DC converter valve is controlled in the following manner:

[0114] When the amplitude change of the three-phase AC base frequency voltage reference command is within the preset AC voltage change range, the sending end flexible DC converter valve is controlled according to the amplitude change of the three-phase AC base frequency voltage reference command.

[0115] or,

[0116] When the amplitude change of the three-phase AC base frequency voltage reference command is greater than the maximum value within the preset AC voltage change range, the sending end flexible DC converter valve is controlled according to the maximum value within the preset AC voltage change range.

[0117] or,

[0118] When the amplitude change of the three-phase AC base frequency voltage reference command is less than the minimum value within the preset AC voltage change range, the sending end flexible DC converter valve is controlled according to the minimum value within the preset AC voltage change range.

[0119] The preset AC voltage variation range can be set according to actual conditions, and is not limited here.

[0120] In this way, by using the preset AC voltage change value as a constraint, a safety boundary is provided for the system while enabling refined control.

[0121] a3, obtain the amplitude of the three-phase AC base frequency voltage at the grid connection point corresponding to the sending-end new energy unit.

[0122] a4. Based on the second difference between the amplitude of the three-phase AC base frequency voltage at the grid connection point and the rated value of the three-phase AC base frequency voltage at the grid connection point, determine the change value of the active current reference command.

[0123] In one possible implementation, the active current reference command change value is determined based on a second difference between the amplitude of the three-phase AC base frequency voltage at the grid connection point and the rated value of the three-phase AC base frequency voltage at the grid connection point, and a preset mapping relationship between the second difference and the active current reference command change value.

[0124] a5 controls the sending-end renewable energy units based on the changes in the active current reference command value.

[0125] In one possible implementation, the sending-end renewable energy generating unit is controlled based on the change in the active current reference command, specifically including the following steps:

[0126] First, shut down the DC voltage outer loop control of the grid-side converter of the sending-end new energy unit.

[0127] Specifically, the outer loop control of the DC voltage of the grid-side converter for the sending-end renewable energy units refers to the "outer regulation loop" in the grid-side converter control system, which takes the "DC-side voltage of the renewable energy units (such as the DC bus voltage of photovoltaic inverters and the DC voltage of wind turbine converters)" as the control target. This loop maintains DC-side voltage stability by dynamically adjusting the active current output of the converter. In scenarios involving grid faults at the receiving end, during the process of consuming energy from renewable energy units, this control loop may experience amplitude saturation, affecting recovery after fault clearance; therefore, it must be shut down first.

[0128] Then, obtain the active current reference command of the grid-side converter of the new energy unit before the fault.

[0129] Finally, based on the change in the active current reference command and the active current reference command, the sending-end renewable energy units are controlled.

[0130] In one possible implementation, the sending-end renewable energy generating unit is controlled based on the change in the active current reference command, specifically including the following steps:

[0131] When the change value of the active current reference command is within the preset range of active current change, the sending-end renewable energy is controlled according to the change value of the active current reference command.

[0132] or,

[0133] When the change in active current reference command is greater than the maximum value in the preset active current change range, the sending-end renewable energy is controlled according to the maximum value in the preset active current change range.

[0134] or,

[0135] When the change in active current reference command is less than the minimum value in the preset active current change range, the sending-end renewable energy is controlled according to the minimum value in the preset active current change range.

[0136] In this way, by using the preset active current change value as a constraint, a safety boundary is provided for the system while achieving refined control.

[0137] The following example, using a flexible offshore DC transmission system, illustrates a fault ride-through method when no communication equipment is used to indicate a fault in the receiving-end power grid. The method includes the following steps:

[0138] b1. When a fault occurs in the onshore power grid (i.e., the receiving-end power grid), the average voltage value corresponding to the offshore or onshore flexible DC converter valve submodule rises above the average voltage threshold, triggering the activation of the distributed energy consumption device in the corresponding flexible DC converter valve.

[0139] b2, while the distributed energy dissipation device dissipates the surplus power, controls the offshore flexible DC converter valve to indicate that the offshore wind farm has experienced a receiving-end grid fault.

[0140] b3, When an offshore wind farm senses a fault in the receiving-end power grid, it enters "onshore AC fault ride-through mode," such as... Figure 7 As shown.

[0141] It should be noted that there are multiple ways to control the offshore flexible DC converter valve to indicate a receiving-end grid fault at the offshore wind farm while the distributed energy dissipation device dissipates surplus power. The following examples illustrate these methods one and two.

[0142] Method 1: While the distributed energy dissipation device dissipates the surplus power, the offshore flexible DC converter valve increases the angular frequency of the offshore AC bus to a preset angular frequency through V / F control to indicate that a receiving-end grid fault has occurred in the offshore wind farm.

[0143] When the angular frequency of the offshore AC bus changes, the frequency of the wind turbine grid connection point in the offshore wind farm will also change accordingly. The phase-locked loop of the grid-side converter of the wind turbine will automatically track the grid connection point frequency. When the output angular frequency of the grid-side converter stabilizes at the preset angular frequency and continues to run for a second preset time, the offshore wind farm senses the grid fault at the receiving end and triggers the wind turbine to enter the "onshore AC fault ride-through mode".

[0144] Method 2: While the distributed energy dissipation device dissipates the surplus power, the current three-phase AC voltage reference command of the offshore flexible DC converter valve is obtained; based on the current three-phase AC voltage reference command, a three-phase AC voltage reference command of a preset frequency is superimposed to obtain the superimposed three-phase AC voltage reference command; according to the superimposed three-phase AC voltage reference command, the offshore flexible DC converter valve is controlled to indicate that a receiving-end grid fault has occurred in the offshore wind farm.

[0145] When the current content of the three-phase AC current output by the grid-side converter exceeds the preset threshold at a preset frequency, and continues to operate for a third preset duration, the offshore wind farm is controlled to determine that a receiving-end grid fault has occurred.

[0146] b4. After the short-term energy consumption ends, the surplus power will cause the DC voltage value of the sending-end flexible DC converter valve to rise again. Based on the increase of the actual DC voltage value compared with the rated value (i.e., the first difference), the amplitude of the reference command value of the three-phase AC base frequency voltage of the offshore flexible DC converter valve will be actively and proportionally reduced (i.e., based on the first difference and the preset mapping relationship between the first difference and the change value of the reference command value of the three-phase AC base frequency voltage, the change value of the reference command value of the three-phase AC base frequency voltage is determined, and the sending-end flexible DC converter valve is controlled based on the change value of the reference command value of the three-phase AC base frequency voltage).

[0147] b5. A decrease in the three-phase AC base frequency voltage output from the offshore flexible DC converter valve will inevitably lead to a decrease in the offshore AC bus voltage, which in turn will reduce the grid connection voltage of the wind turbine (i.e., the sending-end renewable energy unit) grid-side converter. Since the wind turbine grid-side converter has already entered the "onshore AC fault ride-through mode," when the amplitude of the three-phase AC base frequency voltage at the wind turbine grid connection point drops beyond the first AC voltage threshold... U acset1 Subsequently, based on the decrease in the amplitude of the three-phase AC base frequency voltage at the grid connection point compared to its rated value, the active current of the wind turbine is reduced proportionally (i.e., the change in the active current reference command is determined based on the second difference between the amplitude of the three-phase AC base frequency voltage at the grid connection point and its rated value, and the preset mapping relationship between the second difference and the change in the active current reference command; the sending-end renewable energy unit is controlled based on the change in the active current reference command). As the active power output of the wind turbine decreases, the wind turbine energy consumption device will be automatically triggered to engage, thereby achieving onshore AC fault ride-through under the coordination of the wind turbine and flexible DC.

[0148] b6, When the onshore fault is cleared and the onshore flexible DC converter valve output power is restored, the DC voltage of the offshore flexible DC converter valve and the system decreases. When it decreases to the second DC voltage threshold... U dc_set2 After that, the preset mapping relationship between the first difference and the amplitude change value of the three-phase AC base frequency voltage reference command is terminated, and the offshore AC bus voltage will be restored to the rated value.

[0149] b7. As the offshore AC bus voltage recovers, the wind turbine grid connection voltage will also recover. When the grid connection voltage rises above the second AC voltage threshold... U acset2 Then, the preset mapping relationship between the second difference and the change value of the active current reference command is terminated, and the active current command of the wind turbine is restored to the value before the fault. At this point, both the offshore flexible DC converter valve and the wind turbine of the system have exited the fault ride-through mode and returned to normal operation mode.

[0150] It should be noted that when the system includes communication equipment, when the receiving-end grid fails, the offshore wind farm can be directly instructed to experience a receiving-end grid failure through the communication equipment. The subsequent fault ride-through steps are the same as those described in b4-b7 above, and will not be repeated here.

[0151] Figure 6 , Figure 7 , Figure 8 These are control block diagrams for the sending-end flexible DC converter valves, corresponding to the three methods used to indicate grid faults at the receiving end and sending-end renewable energy generating units. Specifically, Figure 6 This is a control block diagram of the sending-end flexible DC converter valve when a fault occurs in the receiving-end power grid of the sending-end renewable energy unit, which relies on communication equipment for indication. Figure 7 This is a control block diagram for increasing the angular frequency of the sending-end AC bus to a preset angular frequency through the sending-end flexible DC converter valve to indicate a fault in the receiving-end power grid of the sending-end renewable energy unit. Figure 8 This is a control block diagram for instructing sending-end renewable energy generating units to indicate faults in the receiving-end power grid using a superimposed three-phase AC voltage reference command. Figure 6 , Figure 7 , Figure 8 When a fault is detected in the receiving-end power grid, the preset first fault flag (Fault) is set to 1; when no fault occurs in the receiving-end power grid, the first fault flag (Fault) is set to 0.

[0152] When no receiving-end grid fault occurs (i.e., Fault=0), the sending-end flexible DC converter valve is controlled based on the block diagram where Fault=0 to determine the d-axis and q-axis components of the AC voltage reference value output by the sending-end flexible DC converter valve. e cdref , e cqref. Figure 6 , Figure 7 , Figure 8 The control method for the feed-end flexible DC converter valve is the same in the block diagram where Fault=0. V dref , V qref These are the reference values ​​for the d-axis and q-axis components of the AC bus voltage at the sending end, respectively. V gd , V gq These are the measured values ​​of the d-axis and q-axis components of the AC bus voltage at the sending end, respectively. I dref , I qref These are the reference values ​​for the d-axis and q-axis components of the AC side current of the feed-end flexible DC converter valve, respectively. I vd , I vq These are the measured values ​​of the d-axis and q-axis components of the AC side current of the feed-end flexible DC converter valve; all PI controllers are proportional-integral controllers.

[0153] When the receiving-end power grid fails (i.e., Fault=1), the d-axis and q-axis components of the AC voltage reference value at the sending-end flexible DC converter valve are determined based on the block diagram containing Fault=1. e cdref , e cqref . Figure 6 , Figure 7 , Figure 8 The control formula for the feed-end flexible DC converter valve is the same in the block diagram where Fault=1 is located. U dc , U dcN These are the DC voltage value and rated DC voltage value of the sending-end flexible DC converter valve at the current moment, respectively. K ac_FRT This is used to determine the amplitude change value Δ of the three-phase AC base frequency voltage reference command based on a preset mapping relationship between the first difference and the amplitude change value of the three-phase AC base frequency voltage reference command. e cdref .exist Figure 6 , Figure 7 , Figure 8 In China, based on K ac_FRT Δ e cdref Subsequently, the limiting step was also used to adjust Δ e cdref Limit the amplitude to ensure Δ e cdref Within the preset range of variation; K 1 represents the proportionality coefficient.U acN This refers to the rated amplitude of the three-phase fundamental frequency voltage of the sending-end AC bus.

[0154] exist Figure 6 , Figure 7 , Figure 8 middle, e cdref , e cqref These are the d-axis and q-axis components of the AC voltage reference value output from the feed-end flexible DC converter valve, respectively. Regardless of whether it is obtained after current inner loop control... e cdref , e cqref Or obtained through the fault-crossing method provided in the embodiments of this application. e cdref , e cqref All will be used as inverse Park transformation P Input 1. Additionally, e aref , e bref , e cref These are the reference values ​​for the three-phase AC voltage output from the feed-end flexible DC converter valve; e cira , e cirb , e circ It is the reference value of the three-phase double-frequency AC voltage output of the flexible DC converter valve at the sending end, controlled by circulating current suppression. N ap , N an , N bp , N bn , N cp , N cn These are reference values ​​for the number of submodules required for the three-phase 6-arm flexible DC converter valve at the sending end, which are output via Nearest Level Modulation (NLM).

[0155] exist Figure 6 In this system, since the fault in the receiving-end power grid is directly indicated to the sending-end renewable energy unit via communication equipment, it is not necessary to control the sending-end flexible DC converter valve to increase the angular frequency of the sending-end AC bus to a preset angular frequency, nor is it necessary to control the sending-end flexible DC converter valve based on the superimposed three-phase AC voltage reference command. Figure 6 and Figure 8In the middle, the inverse Park transformation angle of the fundamental frequency electrical quantity on the transformer valve side controlled by the flexible DC converter valve at the sending end. θ 1. All are through the rated angular frequency ω N After the integration module 1 / s Obtained. And in Figure 7 In the middle, the inverse Park transformation angle of the fundamental frequency electrical quantity on the transformer valve side controlled by the flexible DC converter valve at the sending end. θ 2 is achieved through the rated angular frequency ω N Based on the superposition of Δ ω Then, it goes through the integration module 1 / s The result is that by increasing the angular frequency of the sending-end AC bus to a preset angular frequency, a fault in the receiving-end grid is indicated by the sending-end renewable energy unit. Figure 8 In, with Figure 6 The difference is that, in NLM input, besides e aref , e bref , e cref , e cira , e cirb , e circ When a fault occurs in the receiving-end power grid (i.e., Fault=1), a three-phase AC voltage reference command at a preset frequency is also applied. e aref-h , e bref-h , e cref-h This is to indicate a fault in the receiving-end power grid of the sending-end renewable energy generating unit.

[0156] Figure 9 This is a control block diagram of the renewable energy unit (grid-side converter) when a fault occurs in the receiving-end power grid. Among them, U dc , U dcref These represent the DC voltage value and DC voltage reference command value of the new energy unit (grid-side converter), respectively; Ctrl is a preset control switch indicator. When Ctrl is 0, it indicates that the DC voltage outer loop control is engaged; when Ctrl is 1, it indicates that the DC voltage outer loop control is disengaged; FRT is a preset second fault indicator. When FRT is 1, it indicates that the wind turbine has entered the onshore AC fault ride-through mode; when FRT is 0, it indicates that the wind turbine has exited the onshore AC fault ride-through mode. Δ I dref This is the change in the active current reference command value; I dref , Iqref These are the reference commands for the d-axis and q-axis of the grid-side converter inductor current, respectively. I vd , I vq These are the measured values ​​of the d-axis and q-axis components of the grid-side converter inductor current, respectively. u cdref , u cqref These are the d-axis and q-axis components of the AC voltage reference value of the grid-side converter output after the output of the inner current loop control loop. u aref , u bref , u cref These are the reference values ​​for the three-phase AC voltage output from the grid-side converter; G 1. G 2. G 3. G 4. G 5. G 6 are the trigger pulse signals of the three-phase 6-arm bridge of the grid-side converter, which are output by pulse width modulation (PWM). P 1 is the inverse Park transform; U gq These are the measured values ​​of the q-axis component of the AC side voltage at the grid connection point of the grid-side converter; all PI controllers are proportional-integral controllers. ω N It is the rated angular frequency; ω PLL The angular frequency of the phase-locked loop output; 1 / s For integration modules; θ 3 is the inverse Park transformation angle of the fundamental frequency electrical quantity of the grid-side converter.

[0157] Figure 10 A schematic diagram for determining the change in the active current reference command. Figure 10 middle, U ac The amplitude of the three-phase AC fundamental frequency voltage at the grid connection point. U acset1 The threshold value for the first AC voltage amplitude. U acset2 The threshold value for the second AC voltage amplitude is denoted as FRT, which is the aforementioned second fault identifier. K p _FRT This is used to determine the active current reference command change value Δ based on the second difference between the amplitude of the three-phase AC base frequency voltage at the grid connection point and the rated value of the three-phase AC base frequency voltage at the grid connection point, and the preset mapping relationship between the second difference and the active current reference command change value. I dref .exist Figure 10 In China, based on K p _FRT Δ I dref Subsequently, the limiting step was also used to adjust Δ I dref Limit the amplitude to ensure Δ I dref Within the preset range of variation.

[0158] The above mainly describes the solution provided by the embodiments of this application from a methodological perspective.

[0159] This application also provides a fault-crossing device for implementing the above embodiments and preferred embodiments, which will not be repeated hereafter. As used below, the term "module" can be a combination of software and / or hardware that implements a predetermined function. Although the device described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0160] This embodiment provides a fault ride-through device applied to a new energy grid-connected system via flexible DC transmission. The system includes a sending-end new energy power station, a sending-end AC line, a flexible DC transmission system, and a receiving-end power grid. The sending-end new energy power station, the sending-end AC line, the flexible DC transmission system, and the receiving-end power grid are connected sequentially. The sending-end new energy power station includes at least one sending-end new energy generating unit. The flexible DC transmission system includes a sending-end converter station, a DC line, and a receiving-end converter station. The sending-end converter station includes a sending-end flexible DC converter valve and a sending-end AC bus. The sending-end new energy generating unit is connected to the sending-end converter station via the sending-end AC line and the sending-end AC bus. Figure 11 As shown, the device includes:

[0161] Indication module 1101 is used to control the flexible DC transmission system to indicate that a fault has occurred in the receiving-end converter station and the sending-end new energy generating unit in the event of a fault in the receiving-end power grid.

[0162] The acquisition module 1102 is used to acquire the DC voltage value of the sending-end flexible DC converter valve at the current moment;

[0163] Module 1103 is used to determine a first difference between the DC voltage value and the rated DC voltage value;

[0164] The control module 1104 is used to control the sending-end new energy unit and the sending-end flexible DC converter valve according to the first difference, so that the DC voltage value drops below the preset voltage threshold.

[0165] In one possible implementation, the system includes a distributed energy dissipation device, and the receiving-end converter station includes a receiving-end flexible DC converter valve. The distributed energy dissipation device is configured in the sending-end flexible DC converter valve or the receiving-end flexible DC converter valve. The control module 1104 is further configured to, in the event of a fault in the receiving-end power grid, instruct the sending-end converter station and the sending-end renewable energy unit to experience a fault in the receiving-end power grid, and after such a fault occurs, obtain the average voltage value corresponding to each sub-module in the flexible DC converter valve equipped with the distributed energy dissipation device. When the average voltage value is greater than the average voltage threshold, control the distributed energy dissipation device to keep the average voltage value below the average voltage threshold for a first preset time period.

[0166] In one possible implementation, the control module 1104 is specifically used to control the sending-end flexible DC converter valve to increase the angular frequency of the sending-end AC bus to a preset angular frequency through AC voltage amplitude and frequency control, so as to indicate that the sending-end new energy unit has experienced a receiving-end grid fault.

[0167] or;

[0168] Obtain the current three-phase AC voltage reference command of the sending-end flexible DC converter valve; based on the current three-phase AC voltage reference command, superimpose a three-phase AC voltage reference command of a preset frequency to obtain the superimposed three-phase AC voltage reference command; according to the superimposed three-phase AC voltage reference command, control the sending-end flexible DC converter valve to indicate that a receiving-end grid fault has occurred in the sending-end new energy unit.

[0169] In one possible implementation, the new energy unit includes a grid-side converter; the control module 1104 is also used to control the new energy unit to determine that a fault has occurred in the receiving-end grid after the phase-locked loop of the grid-side converter tracks to a preset angular frequency and continues to run for a second preset time.

[0170] or,

[0171] When the current content of the three-phase AC current output by the grid-side converter exceeds the preset threshold at a preset frequency, and continues to operate for a third preset duration, the control unit determines that a fault has occurred in the receiving-end grid.

[0172] In one possible implementation, the system also includes a communication device; an indication module 1101 is specifically used to indicate, via the communication device, that a receiving-end grid fault has occurred in the sending-end renewable energy unit.

[0173] In one possible implementation, the control module 1104 is specifically used to determine the amplitude change value of the three-phase AC base frequency voltage reference command corresponding to the sending-end flexible DC converter valve based on the first difference.

[0174] The sending-end flexible DC converter valve is controlled based on the amplitude change value of the three-phase AC base frequency voltage reference command.

[0175] Obtain the amplitude of the three-phase AC base frequency voltage at the grid connection point corresponding to the sending-end new energy unit;

[0176] The active current reference command change value is determined based on the second difference between the amplitude of the three-phase AC base frequency voltage at the grid connection point and the rated value of the three-phase AC base frequency voltage at the grid connection point.

[0177] Control the sending-end renewable energy units based on the changes in the active current reference command value.

[0178] In one possible implementation, the control module 1104 is specifically used to determine the three-phase AC base frequency voltage reference command amplitude change value corresponding to the sending-end flexible DC converter valve based on the first difference and a preset mapping relationship between the first difference and the three-phase AC base frequency voltage reference command amplitude change value.

[0179] In one possible implementation, the control module 1104 is specifically used to determine the active current reference command change value based on a second difference between the amplitude of the three-phase AC base frequency voltage at the grid connection point and the rated value of the three-phase AC base frequency voltage at the grid connection point, and a preset mapping relationship between the second difference and the active current reference command change value.

[0180] In one possible implementation, the control module 1104 is specifically used to shut down the outer loop control of the DC voltage of the grid-side converter of the sending-end new energy generator unit;

[0181] Obtain the active current reference command from the grid-side converter of the new energy unit before the fault occurs;

[0182] The sending-end renewable energy units are controlled based on the changes in the active current reference command and the active current reference command.

[0183] Further functional descriptions of the above modules and units are the same as those in the corresponding embodiments described above, and will not be repeated here.

[0184] In this embodiment, the fault-crossing device is presented in the form of a functional unit. Here, a unit refers to an ASIC (Application Specific Integrated Circuit) circuit, a processor and memory that execute one or more software or fixed programs, and / or other devices that can provide the above functions.

[0185] This invention also provides a computer device having the above-described features. Figure 11 The fault-crossing device shown.

[0186] Please see Figure 12 , Figure 12 This is a schematic diagram of the structure of a computer device provided in an optional embodiment of the present invention, such as... Figure 12As shown, the computer device includes one or more processors 10, memory 20, and interfaces for connecting the components, including high-speed interfaces and low-speed interfaces. The components communicate with each other via different buses and can be mounted on a common motherboard or otherwise installed as needed. The processors can process instructions executed within the computer device, including instructions stored in or on memory to display graphical information of a GUI on external input / output devices (such as display devices coupled to the interfaces). In some alternative implementations, multiple processors and / or multiple buses can be used with multiple memories, if desired. Similarly, multiple computer devices can be connected, each providing some of the necessary operations (e.g., as a server array, a group of blade servers, or a multiprocessor system). Figure 12 Take a processor 10 as an example.

[0187] Processor 10 may be a central processing unit, a network processor, or a combination thereof. Processor 10 may further include a hardware chip. The hardware chip may be an application-specific integrated circuit (ASIC), a programmable logic device (PLD), or a combination thereof. The programmable logic device may be a complex programmable logic device (CAMP), a field-programmable gate array (FPGA), a general-purpose array logic (GDA), or any combination thereof.

[0188] The memory 20 stores instructions executable by at least one processor 10 to cause at least one processor 10 to perform the method shown in the above embodiments.

[0189] The memory 20 may include a program storage area and a data storage area. The program storage area may store the operating system and applications required for at least one function; the data storage area may store data created based on the use of the computer device. Furthermore, the memory 20 may include high-speed random access memory and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some alternative embodiments, the memory 20 may optionally include memory remotely located relative to the processor 10, and these remote memories may be connected to the computer device via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

[0190] The memory 20 may include volatile memory, such as random access memory; the memory may also include non-volatile memory, such as flash memory, hard disk or solid-state drive; the memory 20 may also include a combination of the above types of memory.

[0191] The computer device also includes a communication interface 30 for communicating with other devices or communication networks.

[0192] This invention also provides a computer-readable storage medium. The methods described above according to embodiments of the invention can be implemented in hardware or firmware, or implemented as computer code that can be recorded on a storage medium, or implemented as computer code downloaded via a network and originally stored on a remote storage medium or a non-transitory machine-readable storage medium and then stored on a local storage medium. Thus, the methods described herein can be processed by software stored on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. The storage medium can be a magnetic disk, optical disk, read-only memory, random access memory, flash memory, hard disk, or solid-state drive, etc.; further, the storage medium can also include combinations of the above types of memory. It is understood that computers, processors, microprocessor controllers, or programmable hardware include storage components capable of storing or receiving software or computer code, which, when accessed and executed by the computer, processor, or hardware, implements the methods shown in the above embodiments.

[0193] A portion of this invention can be applied to computer program products, such as computer program instructions, which, when executed by a computer, can invoke or provide the methods and / or technical solutions according to the invention through the operation of the computer. Those skilled in the art will understand that the forms in which computer program instructions exist in a computer-readable medium include, but are not limited to, source files, executable files, installation package files, etc. Correspondingly, the ways in which computer program instructions are executed by a computer include, but are not limited to: the computer directly executing the instructions, or the computer compiling the instructions and then executing the corresponding compiled program, or the computer reading and executing the instructions, or the computer reading and installing the instructions and then executing the corresponding installation program. Here, the computer-readable medium can be any available computer-readable storage medium or communication medium accessible to a computer.

[0194] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A method of fault ride-through, characterized by, The application is applied to a new energy grid-connected system through flexible DC power transmission, and the system comprises a sending-end new energy station, a sending-end AC line, a flexible DC power transmission system and a receiving-end power grid, the sending-end new energy station, the sending-end AC line, the flexible DC power transmission system and the receiving-end power grid are sequentially connected, the sending-end new energy station comprises at least one sending-end new energy unit, the flexible DC power transmission system comprises a sending-end converter station, a DC line and a receiving-end converter station, the sending-end converter station comprises a sending-end flexible DC converter valve and a sending-end AC bus, the sending-end new energy unit is connected with the sending-end converter station through the sending-end AC line and the sending-end AC bus, and the method comprises the following steps: In the case that the receiving-end power grid fails, the flexible DC power transmission system is controlled to indicate that the sending-end converter station and the sending-end new energy unit have failed in the receiving-end power grid; A DC voltage value of the sending-end flexible DC converter valve at a current time is obtained; A first difference between the DC voltage value and a DC voltage rated value is determined; According to the first difference, the sending-end new energy unit and the sending-end flexible DC converter valve are controlled so that the DC voltage value is decreased to below a preset voltage threshold value; According to the first difference, a three-phase AC fundamental frequency voltage reference instruction amplitude change value corresponding to the sending-end flexible DC converter valve is determined; According to the three-phase AC fundamental frequency voltage reference instruction amplitude change value, the sending-end flexible DC converter valve is controlled; A grid-connected point three-phase AC fundamental frequency voltage amplitude corresponding to the sending-end new energy unit is obtained; According to a second difference between the grid-connected point three-phase AC fundamental frequency voltage amplitude and a grid-connected point three-phase AC fundamental frequency voltage rated value, an active current reference instruction change value is determined; According to the active current reference instruction change value, the sending-end new energy unit is controlled. The system comprises a distributed energy consumption device, the receiving-end converter station comprises a receiving-end flexible DC converter valve, the distributed energy consumption device is arranged in the sending-end flexible DC converter valve or the receiving-end flexible DC converter valve, and the method further comprises the following steps after the flexible DC power transmission system is controlled to indicate that the sending-end converter station and the sending-end new energy unit have failed in the receiving-end power grid in the case that the receiving-end power grid fails:

2. The method of claim 1, wherein, An average voltage value corresponding to each sub-module in the flexible DC converter valve provided with the distributed energy consumption device is obtained; When the average voltage value is greater than an average voltage threshold value, the distributed energy consumption device is controlled so that the average voltage value is maintained below the average voltage threshold value within a first preset time length. In the case that the receiving-end power grid fails, the flexible DC power transmission system is controlled to indicate that the sending-end converter station and the sending-end new energy unit have failed in the receiving-end power grid, which comprises the following steps:

3. The method of claim 2, wherein, The sending-end flexible DC converter valve is controlled to increase an angular frequency of the sending-end AC bus to a preset angular frequency through AC voltage amplitude and frequency control, so as to indicate that the sending-end new energy unit has failed in the receiving-end power grid; Or ​ Obtaining a current three-phase alternating current voltage reference instruction of the sending end HVDC valve; superimposing a three-phase alternating current voltage reference instruction of a preset frequency on the basis of the current three-phase alternating current voltage reference instruction to obtain a superimposed three-phase alternating current voltage reference instruction; and controlling the sending end HVDC valve according to the superimposed three-phase alternating current voltage reference instruction to instruct the sending end new energy unit to occur a receiving end power grid fault.

4. The method of claim 3, wherein, The sending end new energy unit comprises a grid-side converter; and the method further comprises: controlling the sending end new energy unit to determine that the receiving end power grid occurs a fault when a phase-locked loop of the grid-side converter tracks to the preset angular frequency and continuously operates for a second preset time length; or controlling the sending end new energy unit to determine that the receiving end power grid occurs a fault when a current content of the preset frequency in a three-phase alternating current output by the grid-side converter exceeds a preset threshold and continuously operates for a third preset time length.

5. The method of claim 1, wherein, The system further comprises a communication device; and in the case that the receiving end power grid occurs a fault, the flexible DC power transmission system controls the sending end HVDC station and the sending end new energy unit to occur a receiving end power grid fault, comprising: indicating the sending end new energy unit to occur a receiving end power grid fault through the communication device.

6. The method of claim 1, wherein, The determination of the three-phase alternating current base frequency voltage reference instruction amplitude change value corresponding to the sending end HVDC valve according to the first difference value comprises: determining the three-phase alternating current base frequency voltage reference instruction amplitude change value corresponding to the sending end HVDC valve according to the first difference value and a preset mapping relationship between the first difference value and the three-phase alternating current base frequency voltage reference instruction amplitude change value.

7. The method of claim 1, wherein, The determination of the active current reference instruction change value according to a second difference value between the three-phase alternating current base frequency voltage amplitude of the grid connection point and a three-phase alternating current base frequency voltage rated value of the grid connection point comprises: determining the active current reference instruction change value according to the second difference value between the three-phase alternating current base frequency voltage amplitude of the grid connection point and the three-phase alternating current base frequency voltage rated value of the grid connection point and a preset mapping relationship between the second difference value and the active current reference instruction change value.

8. The method of claim 1, wherein, The control of the sending end new energy unit according to the active current reference instruction change value comprises: closing a DC voltage outer loop control of a grid-side converter in the sending end new energy unit; obtaining an active current reference instruction of the grid-side converter in the sending end new energy unit before a fault; controlling the sending end new energy unit according to the active current reference instruction change value and the active current reference instruction.

9. A fault ride-through device, characterized by The application is applied to a new energy grid-connected system through flexible DC power transmission, and the system comprises a sending terminal new energy station, a sending terminal AC line, a flexible DC power transmission system and a receiving terminal power grid, the sending terminal new energy station, the sending terminal AC line, the flexible DC power transmission system and the receiving terminal power grid are sequentially connected, the sending terminal new energy station comprises at least one sending terminal new energy unit, the flexible DC power transmission system comprises a sending terminal converter station, a DC line and a receiving terminal converter station, the sending terminal converter station comprises a sending terminal flexible DC converter valve and a sending terminal AC bus, and the sending terminal new energy unit is connected with the sending terminal converter station through the sending terminal AC line and the sending terminal AC bus. The indication module is configured to control the flexible DC power transmission system to indicate that the sending terminal converter station and the sending terminal new energy unit have a receiving terminal power grid fault in the case that the receiving terminal power grid has a fault. The acquisition module is configured to acquire a DC voltage value of the sending terminal flexible DC converter valve at a current time. The determination module is configured to determine a first difference between the DC voltage value and a DC voltage rated value. The control module is configured to control the sending terminal new energy unit and the sending terminal flexible DC converter valve according to the first difference, so that the DC voltage value is decreased to below a preset voltage threshold. The control of the sending terminal new energy unit and the sending terminal flexible DC converter valve according to the first difference, so that the DC voltage value is decreased to below a preset voltage threshold, comprises: determining a three-phase AC fundamental frequency voltage reference instruction amplitude change value corresponding to the sending terminal flexible DC converter valve according to the first difference; controlling the sending terminal flexible DC converter valve according to the three-phase AC fundamental frequency voltage reference instruction amplitude change value; acquiring a three-phase AC fundamental frequency voltage amplitude of a grid-connected point corresponding to the sending terminal new energy unit; determining an active current reference instruction change value according to a second difference between the three-phase AC fundamental frequency voltage amplitude of the grid-connected point and a three-phase AC fundamental frequency voltage rated value of the grid-connected point; and controlling the sending terminal new energy unit according to the active current reference instruction change value.

10. A computer device, comprising: The application further provides a computer readable storage medium having computer instructions stored thereon, and the computer instructions are used to make a computer execute the fault ride-through method. The computer readable storage medium has computer instructions stored thereon, and the computer instructions are used to make a computer execute the fault ride-through method.

11. A computer readable storage medium, characterized in that, ​

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