Method, system and computer device for ac fault ride through of hvdc receiving end

Abstract

The application relates to a flexible direct-current receiving-end alternating-current fault ride-through method, a system, a computer device, a storage medium and a computer program product. The method comprises the following steps: when a receiving-end alternating-current fault signal of a receiving-end alternating-current system is received, a sending-end converter is controlled to be switched to a capacitor voltage average value control mode; a capacitor voltage average value of the sending-end converter and a capacitor voltage reference value of the sending-end converter are acquired; a target sending-end direct-current voltage reference value of the sending-end converter is determined according to the capacitor voltage average value and the capacitor voltage reference value; the sending-out power of the direct-current side of the sending-end converter is controlled according to the target sending-end direct-current voltage reference value until the capacitor voltage of the sending-end converter is in a stable state, and the capacitor voltage average value control mode is exited. The method can solve the capacitor voltage fluctuation problem of the sending-end converter after the sending-end converter is input into a direct-current energy consumption device, and improves the stability of the sending-end alternating-current system.

Description

Technical Field

[0001] This application relates to the field of power engineering technology, and in particular to a receiving-end AC fault ride-through method, system, computer equipment, storage medium, and computer program product. Background Technology

[0002] The installed capacity of new energy power stations has increased significantly, and their distribution has become increasingly widespread. The use of flexible DC transmission for new energy has become a current research hotspot. In this system, the sending-end AC system is a large-scale photovoltaic system, transmitting power to the receiving-end AC system through the sending-end converter, DC lines, and receiving-end converter.

[0003] Currently, a fault has occurred in the receiving-end AC system. After the receiving-end AC fault is detected by the receiving-end converter, the DC power dissipation device is activated. Once the receiving-end AC system fault is cleared, the DC power dissipation device is deactivated, resulting in large fluctuations in the capacitor voltage of the sending-end converter, which poses a safety hazard. Summary of the Invention

[0004] Based on this, it is necessary to provide a flexible DC receiving-end AC fault ride-through method, system, computer equipment, computer-readable storage medium, and computer program product that can solve the problem of voltage fluctuations in the capacitor of the sending-end converter after the receiving-end converter is connected to a DC energy-consuming device.

[0005] Firstly, this application provides a flexible DC receiving-end AC fault ride-through method. The method includes:

[0006] When a receiving-end AC fault signal is received from the receiving-end AC system, the sending-end converter is controlled to switch to the capacitor voltage average value control mode.

[0007] Obtain the average value of the capacitor voltage of the sending-end converter and the reference value of the capacitor voltage of the sending-end converter;

[0008] The target DC voltage reference value of the sending-end converter is determined based on the average value of the capacitor voltage and the reference value of the capacitor voltage.

[0009] The output power of the DC side of the sending-end converter is controlled according to the target DC voltage reference value until the capacitor voltage of the sending-end converter is in a stable state, and then the capacitor voltage average value control mode is exited.

[0010] In one embodiment, determining the target DC voltage reference value of the sending-end converter based on the average capacitor voltage and the capacitor voltage reference value includes:

[0011] The change in capacitor voltage of the sending-end converter under the condition of a fault in the receiving-end AC system is obtained by the difference between the square of the average value of the capacitor voltage and the square of the reference value of the capacitor voltage.

[0012] By performing proportional-integral control on the capacitor voltage change value, the change in the DC voltage reference value of the sending-end converter is obtained;

[0013] The change in the DC voltage reference value and the DC voltage reference value of the sending-end converter are superimposed to obtain the target DC voltage reference value of the sending-end converter.

[0014] In one embodiment, before the control of the sending-end converter switches to the capacitor voltage average value control mode, the method further includes:

[0015] If the average value of the capacitor voltage is greater than the reference value of the capacitor voltage, the sending-end converter is controlled to switch to the average value control mode of the capacitor voltage.

[0016] In one embodiment, the method further includes:

[0017] When exiting the capacitor voltage average value control mode, the change in the DC voltage reference value of the sending-end converter is obtained;

[0018] The DC voltage reference value is controlled to change linearly to zero at a set rate.

[0019] In one embodiment, the step of controlling the sending-end converter to switch to the capacitor voltage average value control mode when a receiving-end AC fault signal of the receiving-end AC system is received includes:

[0020] When a receiving-end AC fault signal is received from the receiving-end AC system, the sending-end converter is controlled to switch to the average capacitor voltage control mode, and a timer is triggered to start timing, and the steps of obtaining the average capacitor voltage of the sending-end converter and the reference value of the capacitor voltage of the sending-end converter are executed.

[0021] The step of controlling the output power of the DC side of the sending-end converter according to the target sending-end DC voltage reference value until the capacitor voltage of the sending-end converter is in a stable state includes:

[0022] The output power of the DC side of the sending-end converter is controlled according to the target sending-end DC voltage reference value, and the timing duration of the timer is obtained.

[0023] If the timing duration reaches the preset duration and the fault in the receiving-end AC system is cleared, it indicates that the capacitor voltage of the sending-end converter is in a stable state; wherein, the preset duration is longer than the fault clearing duration of the receiving-end AC system.

[0024] In one embodiment, the method further includes:

[0025] If the timing duration reaches the preset duration and the fault in the receiving-end AC system is not cleared, the timer is triggered to restart the timing, and the step of controlling the sending-end converter to switch to the capacitor voltage average value control mode is executed until the capacitor voltage of the sending-end converter is in a stable state, and then the capacitor voltage average value control mode is exited.

[0026] Secondly, this application also provides a flexible DC receiving-end AC fault ride-through system. The system includes:

[0027] The system includes a receiving-end AC system, a receiving-end converter, and a sending-end converter. The receiving-end AC system is connected to the receiving-end converter. The receiving-end converter and the sending-end converter are connected via a DC line. The receiving-end converter includes a first control module, and the sending-end converter includes a second control module, wherein:

[0028] The first control module is used to detect a transmitting fault in the receiving-end AC system, acquire the receiving-end AC fault signal of the receiving-end AC system, and send the receiving-end AC fault signal to the sending-end converter.

[0029] The second control module is used to control the sending-end converter to switch to the capacitor voltage average value control mode when a receiving-end AC fault signal is received from the receiving-end AC system; and to control the output power of the DC side of the sending-end converter based on the capacitor voltage average value control mode until the capacitor voltage of the sending-end converter is in a stable state.

[0030] Thirdly, this application also provides a computer device. The computer device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to perform the following steps:

[0031] When a receiving-end AC fault signal is received from the receiving-end AC system, the sending-end converter is controlled to switch to the capacitor voltage average value control mode.

[0032] Obtain the average value of the capacitor voltage of the sending-end converter and the reference value of the capacitor voltage of the sending-end converter;

[0033] The target DC voltage reference value of the sending-end converter is determined based on the average value of the capacitor voltage and the reference value of the capacitor voltage.

[0034] The output power of the DC side of the sending-end converter is controlled according to the target DC voltage reference value until the capacitor voltage of the sending-end converter is in a stable state, and then the capacitor voltage average value control mode is exited.

[0035] Fourthly, this application also provides a computer-readable storage medium. The computer-readable storage medium stores a computer program thereon, which, when executed by a processor, performs the following steps:

[0036] When a receiving-end AC fault signal is received from the receiving-end AC system, the sending-end converter is controlled to switch to the capacitor voltage average value control mode.

[0037] Obtain the average value of the capacitor voltage of the sending-end converter and the reference value of the capacitor voltage of the sending-end converter;

[0038] The target DC voltage reference value of the sending-end converter is determined based on the average value of the capacitor voltage and the reference value of the capacitor voltage.

[0039] The output power of the DC side of the sending-end converter is controlled according to the target DC voltage reference value until the capacitor voltage of the sending-end converter is in a stable state, and then the capacitor voltage average value control mode is exited.

[0040] Fifthly, this application also provides a computer program product. The computer program product includes a computer program that, when executed by a processor, performs the following steps:

[0041] When a receiving-end AC fault signal is received from the receiving-end AC system, the sending-end converter is controlled to switch to the capacitor voltage average value control mode.

[0042] Obtain the average value of the capacitor voltage of the sending-end converter and the reference value of the capacitor voltage of the sending-end converter;

[0043] The target DC voltage reference value of the sending-end converter is determined based on the average value of the capacitor voltage and the reference value of the capacitor voltage.

[0044] The output power of the DC side of the sending-end converter is controlled according to the target DC voltage reference value until the capacitor voltage of the sending-end converter is in a stable state, and then the capacitor voltage average value control mode is exited.

[0045] The aforementioned flexible DC receiving-end AC fault ride-through method, system, computer equipment, storage medium, and computer program product, when a fault is detected in the receiving-end AC system, transmits a receiving-end AC fault signal from the receiving-end converter to the sending-end converter. Upon receiving the receiving-end AC fault signal, the sending-end converter switches to a capacitor voltage average value control mode. Based on this mode, the output power on the DC side of the sending-end converter is controlled until the capacitor voltage of the sending-end converter stabilizes. By transmitting the receiving-end AC fault signal to the sending-end converter and controlling it to switch to the capacitor voltage average value control mode when a fault occurs in the receiving-end AC system, the capacitor voltage is stabilized, resolving capacitor voltage fluctuations in the sending-end converter after the receiving-end converter is connected to a DC power dissipation device, thus improving the stability of the sending-end AC system. Attached Figure Description

[0046] Figure 1 This is a diagram illustrating the application environment of a flexible DC receiving-end AC fault ride-through method in one embodiment.

[0047] Figure 2 This is a flowchart illustrating a flexible DC receiving-end AC fault ride-through method in one embodiment;

[0048] Figure 3 This is a flowchart illustrating a method for determining a target DC voltage reference value for a sending-end converter in one embodiment.

[0049] Figure 4 This is a schematic diagram of the capacitor voltage average value control block in one embodiment;

[0050] Figure 5 This is a flowchart illustrating the flexible DC receiving-end AC fault ride-through method in another embodiment;

[0051] Figure 6 This is a flowchart illustrating the flexible DC receiving-end AC fault ride-through method in another embodiment;

[0052] Figure 7 This is a schematic diagram of the system structure of a flexible DC receiving-end AC fault ride-through method in one embodiment;

[0053] Figure 8 This is a structural block diagram of a flexible DC receiving-end AC fault ride-through system in one embodiment;

[0054] Figure 9 This is an internal structural diagram of a computer device in one embodiment. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0056] The flexible DC receiving-end AC fault ride-through method provided in this application embodiment can be applied to, for example... Figure 1 The application environment is shown. In this environment, the sending-end converter 102 communicates with the receiving-end converter 104 via a DC line. The sending-end converter 102 is connected to the sending-end AC system, and the receiving-end converter 104 is connected to the receiving-end AC system. A data storage system can store the data that the sending-end converter 102 needs to process. The data storage system can be integrated onto the sending-end converter 102 or placed in the cloud or on another network server. When the receiving-end converter detects a fault in the receiving-end AC system, it sends a receiving-end AC fault signal to the sending-end converter based on the communication established between the sending-end and receiving-end converters. Upon receiving the receiving-end AC fault signal, the sending-end converter switches to the capacitor voltage averaging control mode. It then acquires the average capacitor voltage and reference value of the sending-end converter's capacitor voltage. Based on these values, it determines the target sending-end DC voltage reference value. Finally, it controls the DC power output of the sending-end converter according to this target value until the capacitor voltage stabilizes, at which point it exits the capacitor voltage averaging control mode. The sending-end converter and the receiving-end converter can be of different types.

[0057] In one embodiment, such as Figure 2 As shown, a flexible DC receiving-end AC fault ride-through method is provided, which is applied to... Figure 1 Taking the sending-end converter in the example, the explanation includes the following steps:

[0058] Step 202: When a receiving-end AC fault signal is received from the receiving-end AC system, the sending-end converter is controlled to switch to the capacitor voltage average value control mode.

[0059] There are several ways to detect whether the receiving-end AC system is faulty, including those that can be detected using existing fault detection methods. For example, when detecting whether the receiving-end AC system is faulty, one can check whether the AC voltage of the receiving-end AC system is normal. If the effective value of the AC voltage drops to less than a certain value (e.g., 0.5 pu), then it is determined that the receiving-end AC system is faulty.

[0060] Specifically, the receiving-end converter detects faults in the receiving-end AC system. If a fault occurs in the receiving-end AC system, the receiving-end converter activates a DC power dissipation device to consume the power transmitted from the rectifier side. It also sends a receiving-end AC fault signal to the sending-end converter, controlling the sending-end converter to switch to an average capacitor voltage control mode to stabilize the capacitor voltage of the submodules within the sending-end converter.

[0061] Step 204: Obtain the average value of the capacitor voltage of the sending-end converter and the reference value of the capacitor voltage of the sending-end converter.

[0062] The sending-end converter includes multiple sub-modules, and the capacitor voltage of each sub-module is not exactly the same. When determining the capacitor voltage of the sending-end converter, the capacitor voltage of the sub-modules is averaged to obtain the average capacitor voltage of the sending-end converter.

[0063] Step 206: Determine the target DC voltage reference value of the sending-end converter based on the average capacitor voltage and the capacitor voltage reference value.

[0064] Specifically, when a receiving-end AC fault signal is received from the receiving-end AC system, the sending-end converter is controlled to switch to the capacitor voltage average value control mode. In the capacitor voltage average value control mode, the target sending-end DC voltage reference value of the sending-end converter is determined based on the average capacitor voltage and the capacitor voltage reference value.

[0065] Step 208: Control the output power of the DC side of the sending-end converter according to the target sending-end DC voltage reference value until the capacitor voltage of the sending-end converter is in a stable state, and exit the capacitor voltage average value control mode.

[0066] Specifically, the sending-end converter controls the output power on its DC side based on the target sending-end DC voltage reference value until the capacitor voltage of the sending-end converter reaches a stable state, at which point it exits the capacitor voltage averaging control mode. At this point, the fault in the receiving-end AC system has been cleared, the receiving-end converter disconnects the DC power-consuming device, and the energy transmission between the sending-end and receiving-end AC systems is restored.

[0067] In the aforementioned flexible DC receiving-end AC fault ride-through method, when a fault is detected in the receiving-end AC system, the receiving-end AC fault signal is sent from the receiving-end converter to the sending-end converter. Upon receiving the receiving-end AC fault signal, the sending-end converter switches to a capacitor voltage average value control mode. The DC output power of the sending-end converter is controlled based on this mode until the capacitor voltage of the sending-end converter stabilizes. By sending the receiving-end AC fault signal to the sending-end converter and controlling it to switch to the capacitor voltage average value control mode when a fault occurs in the receiving-end AC system, the capacitor voltage is stabilized, resolving capacitor voltage fluctuations in the sending-end converter after the receiving-end converter is connected to a DC energy-consuming device, thus improving the stability of the sending-end AC system.

[0068] In one embodiment, such as Figure 3 As shown, a capacitor voltage averaging control method is provided, which is applied to... Figure 1 Taking the sending-end converter in the example, the explanation includes the following steps:

[0069] Step 302: Based on the difference between the square of the average capacitor voltage and the square of the reference capacitor voltage, the change in capacitor voltage of the sending-end converter under AC system fault conditions is obtained.

[0070] Step 304: By performing proportional-integral control on the capacitor voltage change value, the change in the DC voltage reference value of the sending-end converter is obtained.

[0071] Specifically, the change in capacitor voltage of the sending-end converter under AC system fault conditions is input to a PI (proportional integral) controller for proportional-integral control, yielding the change in the DC voltage reference value of the sending-end converter. A PI controller is a linear controller that uses the control deviation between the given value and the actual output value as a basis, and combines the proportional and integral components of this deviation linearly to form the control quantity, thereby controlling the controlled object.

[0072] like Figure 4The diagram shown is a schematic block diagram of the capacitor voltage average value control mode in one embodiment. Ucap_ref is the capacitor voltage reference value, Ucap is the capacitor voltage average value, PI is the PI regulator, delta_Eref is the change in the DC voltage reference value, and Eref is the DC voltage reference value. The capacitor voltage change value of the sending-end converter is obtained based on the difference between the square of the average capacitor voltage and the square of the capacitor voltage reference value. This change value is input to the PI regulator, which outputs the change in the DC voltage reference value. The change in the DC voltage reference value is then superimposed with the sending-end DC voltage reference value of the sending-end converter to obtain the target sending-end DC voltage reference value.

[0073] Step 306: The change in the DC voltage reference value is superimposed with the DC voltage reference value of the sending-end converter to obtain the target DC voltage reference value of the sending-end converter.

[0074] In the aforementioned capacitor voltage average value control method, the difference between the square of the average capacitor voltage and the square of the capacitor voltage reference value is fed into a PI controller to generate a change in the sending-end DC voltage reference value. This change is then superimposed on the sending-end DC voltage reference value of the sending-end converter, ultimately changing the sending-end DC voltage reference value. Furthermore, after the sending-end DC voltage reference value changes, the sending-end converter is controlled according to the changed DC voltage reference value, which can change the output power on the DC side of the sending-end converter, thereby achieving the purpose of stabilizing the capacitor voltage.

[0075] In another embodiment, such as Figure 5 As shown, a flexible DC receiving-end AC fault ride-through method is provided, which is applied to... Figure 1 Taking the sending-end converter in the example, the explanation includes the following steps:

[0076] Step 502: When a receiving-end AC fault signal is received from the receiving-end AC system, the average value of the capacitor voltage of the sending-end converter and the reference value of the capacitor voltage of the sending-end converter are obtained.

[0077] Step 504: Check whether the average capacitor voltage is greater than the capacitor voltage reference value. If yes, proceed to step 508; otherwise, proceed to step 506.

[0078] Specifically, detecting whether the average capacitor voltage is greater than the capacitor voltage reference value is used to determine whether the fault in the receiving-end AC system is a temporary, recoverable fault or a temporary, unrecoverable fault. If it is determined to be a temporary, unrecoverable fault, the sending-end converter is switched to the average capacitor voltage control mode to stabilize the capacitor voltage of the sending-end converter and prevent voltage fluctuations in the sending-end flexible DC submodule capacitor after the receiving-end converter is connected to the DC energy dissipation device.

[0079] Step 506: If the average capacitor voltage is less than the capacitor voltage reference value, it indicates that the fault in the receiving-end AC system has been cleared.

[0080] Step 508: Determine the target DC voltage reference value of the sending-end converter based on the average capacitor voltage and the capacitor voltage reference value.

[0081] Step 510: Control the output power of the DC side of the sending-end converter according to the target sending-end DC voltage reference value until the capacitor voltage of the sending-end converter is in a stable state, and exit the capacitor voltage average value control mode.

[0082] Step 512: When exiting the capacitor voltage average value control mode, obtain the change in the DC voltage reference value of the sending-end converter.

[0083] Step 514: Control the DC voltage reference value change linearly to zero at a set rate.

[0084] In the aforementioned flexible DC receiving-end AC fault ride-through method, when a fault is detected in the receiving-end AC system, the receiving-end converter is simultaneously connected to the DC energy dissipation device, and a receiving-end AC fault signal is sent from the receiving-end converter to the sending-end converter. When the sending-end converter receives the receiving-end AC fault signal, it checks whether the average capacitor voltage of the sending-end converter is greater than the capacitor voltage reference value. If the average capacitor voltage is greater than the reference value, the sending-end converter switches to the capacitor voltage average value control mode, thereby changing the output power on the DC side of the sending-end converter to stabilize the capacitor voltage. This solves the problem of capacitor voltage fluctuations in the sending-end converter after the receiving-end converter is connected to the DC energy dissipation device, improving the stability of the sending-end AC system.

[0085] Furthermore, when a fault occurs in the receiving-end AC system, the power balance between the receiving-end and sending-end AC systems is disrupted, causing fluctuations in the capacitor voltage of the sending-end converter. If the fluctuation range of the sending-end converter capacitor voltage is large, it will lead to large fluctuations in the sending-end AC system voltage, preventing stable phase-locking of the photovoltaic system and further amplifying the fluctuations in both the sending-end converter capacitor voltage and the sending-end AC system voltage, ultimately causing instability in the sending-end AC system. To address the problem of fluctuations in the sending-end converter capacitor voltage and the sending-end AC system voltage, and to ensure the stability of the sending-end AC system, it is necessary to minimize the fluctuations in the sending-end converter capacitor voltage during a fault in the receiving-end AC system.

[0086] In another embodiment, such as Figure 6 As shown, a flexible DC receiving-end AC fault ride-through method is provided, which is applied to... Figure 1 Taking the sending-end converter in the example, the explanation includes the following steps:

[0087] Step 602: When a receiving-end AC fault signal is received from the receiving-end AC system, the sending-end converter is controlled to switch to the capacitor voltage average value control mode, and the timer is triggered to start counting.

[0088] Step 604: Obtain the average value of the capacitor voltage of the sending-end converter and the reference value of the capacitor voltage of the sending-end converter.

[0089] Step 606: Determine the target DC voltage reference value of the sending-end converter based on the average capacitor voltage and the capacitor voltage reference value.

[0090] Step 608: Control the output power of the DC side of the sending-end converter according to the target sending-end DC voltage reference value, and obtain the timing duration of the timer.

[0091] Step 610: If the timing duration reaches the preset duration and the fault in the receiving-end AC system is cleared, it indicates that the capacitor voltage of the sending-end converter is in a stable state, and the capacitor voltage average value control mode is exited.

[0092] The preset duration is longer than the fault clearing duration of the receiving end's communication system.

[0093] Step 612: If the timing duration reaches the preset duration and the fault in the receiving-end AC system is not cleared, the timer is triggered to start timing again, and the step of controlling the sending-end converter to switch to the capacitor voltage average value control mode is executed until the capacitor voltage of the sending-end converter is in a stable state, and then the capacitor voltage average value control mode is exited.

[0094] Specifically, if the timing duration reaches the preset duration and the fault in the receiving-end AC system is not cleared, the timer is triggered to restart, and the sending-end converter is controlled to switch to the capacitor voltage average value control mode; the average capacitor voltage and the reference value of the sending-end converter are obtained; based on the average capacitor voltage and the reference value, the target sending-end DC voltage reference value of the sending-end converter is determined; the output power on the DC side of the sending-end converter is controlled according to the target sending-end DC voltage reference value until the capacitor voltage of the sending-end converter is in a stable state, and then the capacitor voltage average value control mode is exited.

[0095] Step 614: Obtain the change in the DC voltage reference value of the sending-end converter.

[0096] Step 616: Control the DC voltage reference value change linearly to zero at a set rate.

[0097] Specifically, when starting or exiting the capacitor voltage average value control, the change in the voltage reference value output by the controller in the sending-end converter at the corresponding time is obtained, and the change in the DC voltage reference value is controlled to change linearly to zero at a set rate.

[0098] like Figure 7The diagram shown illustrates the system architecture of a flexible DC receiving-end AC fault ride-through method in one embodiment. It includes a sending-end AC system, a sending-end flexible DC converter station, a DC line, a receiving-end flexible DC converter station, and a receiving-end AC system. The sending-end AC system includes renewable energy sources but not conventional power sources. The renewable energy power from the sending-end AC system is transmitted to the receiving-end flexible DC converter station via the DC line through the sending-end flexible DC converter station. The receiving-end flexible DC converter station is connected to the receiving-end AC system, which includes conventional power sources. The sending-end flexible DC converter station is equipped with corresponding sending-end converters, and the receiving-end flexible DC converter station is equipped with corresponding receiving-end converters.

[0099] The receiving-end converter detects faults in the receiving-end AC system. If a fault occurs, the receiving-end converter activates a DC power dissipation device to consume the power transmitted from the rectifier side. It also sends a receiving-end AC fault signal to the sending-end converter, controlling it to switch to capacitor voltage average value control mode. The receiving-end converter obtains the average capacitor voltage and a reference capacitor voltage. Based on the difference between the square of the average capacitor voltage and the square of the reference capacitor voltage, it calculates the capacitor voltage change of the sending-end converter. This change is input to a PI controller, which outputs the change in the DC voltage reference value. This change is then superimposed on the sending-end DC voltage reference value to obtain the target sending-end DC voltage reference value. The output power of the DC side of the sending-end converter is controlled according to the target sending-end DC voltage reference value until the capacitor voltage of the sending-end converter reaches a stable state, at which point the capacitor voltage averaging control mode is exited. When exiting the capacitor voltage averaging control mode, the change in the DC voltage reference value of the sending-end converter is acquired, and the change in the DC voltage reference value is controlled to linearly change to zero at a set rate. After the AC fault at the receiving end is cleared, the receiving-end converter disconnects the DC power dissipation device.

[0100] In the aforementioned flexible DC receiving-end AC fault ride-through method, when a fault is detected in the receiving-end AC system, the receiving-end converter is simultaneously connected to the DC energy dissipation device, and a receiving-end AC fault signal is sent from the receiving-end converter to the sending-end converter. Upon receiving the receiving-end AC fault signal, the sending-end converter switches to the capacitor voltage average value control mode, triggering a timer to start. The output power of the sending-end converter on the DC side is controlled based on the capacitor voltage average value control mode until the capacitor voltage of the sending-end converter stabilizes. After the capacitor voltage average value control mode exits, the change in the voltage reference value output by this control returns to zero at a certain rate, stabilizing the capacitor voltage and resolving capacitor voltage fluctuations in the sending-end converter after the receiving-end converter is connected to the DC energy dissipation device, thus improving the stability of the sending-end AC system.

[0101] It should be understood that although the steps in the flowcharts of the above embodiments are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the above embodiments may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0102] Based on the same inventive concept, this application also provides a flexible DC receiving-end AC fault ride-through system for implementing the flexible DC receiving-end AC fault ride-through method described above. The solution provided by this system is similar to the solution described in the above method; therefore, the specific limitations of one or more flexible DC receiving-end AC fault ride-through system embodiments provided below can be found in the limitations of the flexible DC receiving-end AC fault ride-through method described above, and will not be repeated here.

[0103] In one embodiment, such as Figure 8 As shown, a flexible DC receiving-end AC fault ride-through system is provided. The flexible DC receiving-end AC fault ride-through system includes a receiving-end AC system, a receiving-end converter, and a sending-end converter. The receiving-end AC system is connected to the receiving-end converter, and the receiving-end converter and the sending-end converter are connected via a DC line. The receiving-end converter includes a first control module, and the sending-end converter includes a second control module, wherein:

[0104] The first control module is used to acquire the receiving-end AC fault signal of the receiving-end AC system when a transmitting fault is detected in the receiving-end AC system, and send the receiving-end AC fault signal to the sending-end converter.

[0105] The second control module is used to control the sending-end converter to switch to the capacitor voltage average value control mode when a receiving-end AC fault signal is received from the receiving-end AC system; and to control the output power of the DC side of the sending-end converter based on the capacitor voltage average value control mode until the capacitor voltage of the sending-end converter is in a stable state.

[0106] Specifically, when the sending-end converter receives a receiving-end AC fault signal from the receiving-end AC system, the second control module in the second control module controls the sending-end converter to switch to the capacitor voltage average value control mode. The sending-end converter obtains the capacitor voltage average value and the capacitor voltage reference value, and determines the target sending-end DC voltage reference value based on the capacitor voltage average value and the capacitor voltage reference value. The sending-end converter controls the DC power output of the sending-end converter based on the target sending-end DC voltage reference value until the capacitor voltage of the sending-end converter is in a stable state, and then exits the capacitor voltage average value control mode.

[0107] The aforementioned flexible DC receiving-end AC fault ride-through method system, when a fault is detected in the receiving-end AC system, sends a receiving-end AC fault signal from the receiving-end converter to the sending-end converter. Upon receiving the receiving-end AC fault signal, the sending-end converter switches to a capacitor voltage average value control mode. Based on this mode, the power output from the DC side of the sending-end converter is controlled until the capacitor voltage of the sending-end converter stabilizes. By sending the receiving-end AC fault signal to the sending-end converter and controlling it to switch to the capacitor voltage average value control mode when a fault occurs in the receiving-end AC system, the capacitor voltage is stabilized, resolving capacitor voltage fluctuations in the sending-end converter after the receiving-end converter is connected to a DC power dissipation device, thus improving the stability of the sending-end AC system.

[0108] In another embodiment, a flexible DC receiving-end AC fault ride-through system is provided. The flexible DC receiving-end AC fault ride-through system includes a receiving-end AC system, a receiving-end converter, a sending-end converter, and a sending-end AC system. The receiving-end AC system is connected to the receiving-end converter, and the sending-end AC system is connected to the sending-end converter. The receiving-end converter and the sending-end converter are connected via a DC line. The receiving-end converter includes a first control module, and the sending-end converter, in addition to including a second control module, also includes a judgment module and a data acquisition module.

[0109] The second control module is also used to obtain the change value of the capacitor voltage of the sending-end converter under the condition of a fault in the receiving-end AC system, based on the difference between the square of the average value of the capacitor voltage and the square of the reference value of the capacitor voltage.

[0110] By performing proportional-integral control on the capacitor voltage change, the change in the DC voltage reference value of the sending-end converter is obtained;

[0111] The change in the DC voltage reference value is superimposed with the DC voltage reference value of the sending-end converter to obtain the target DC voltage reference value of the sending-end converter.

[0112] The judgment module is used to detect whether the average capacitor voltage is greater than the capacitor voltage reference value. If the average capacitor voltage is less than the capacitor voltage reference value, it indicates that the fault in the receiving end AC system has been cleared.

[0113] The data acquisition module is used to acquire the change in the DC voltage reference value of the sending-end converter when exiting the capacitor voltage average value control mode.

[0114] The DC voltage reference value is controlled to change linearly to zero at a set rate.

[0115] The second control module is also used to control the sending-end converter to switch to the capacitor voltage average value control mode when a receiving-end AC fault signal is received from the receiving-end AC system, and to trigger the timer to start counting.

[0116] The second control module is also used to control the output power of the DC side of the sending-end converter according to the target sending-end DC voltage reference value and to obtain the timing duration of the timer.

[0117] If the timing duration reaches the preset duration and the fault in the receiving-end AC system is cleared, it indicates that the capacitor voltage of the sending-end converter is in a stable state; wherein, the preset duration is longer than the fault clearing duration of the receiving-end AC system.

[0118] The second control module is also used to trigger the timer to start timing again if the timing duration reaches the preset duration and the fault in the receiving-end AC system is not cleared, and to execute the step of controlling the sending-end converter to switch to the capacitor voltage average value control mode until the capacitor voltage of the sending-end converter is in a stable state, and then exit the capacitor voltage average value control mode.

[0119] The modules in the aforementioned flexible DC receiving-end AC fault ride-through system can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device, or stored in the computer device's memory as software, so that the processor can call and execute the corresponding operations of each module.

[0120] In one embodiment, a computer device is provided, which may be a terminal, and its internal structure diagram may be as follows: Figure 9As shown, the computer device includes a processor, memory, communication interface, display screen, and input system connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage media. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, mobile cellular networks, NFC (Near Field Communication), or other technologies. When executed by the processor, the computer program implements a flexible DC receiving-end AC fault ride-through method. The display screen can be an LCD screen or an e-ink screen. The input system can be a touch layer covering the display screen, buttons, a trackball, or a touchpad on the computer device's casing, or an external keyboard, touchpad, or mouse.

[0121] Those skilled in the art will understand that Figure 9 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0122] In one embodiment, a computer device is also provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps in the above method embodiments.

[0123] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon that, when executed by a processor, implements the steps in the above method embodiments.

[0124] In one embodiment, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps in the above method embodiments.

[0125] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties.

[0126] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments of the above methods. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0127] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0128] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A flexible DC receiving-end AC fault ride-through method, characterized in that, The method includes: When a receiving-end AC fault signal is received from the receiving-end AC system, the sending-end converter is controlled to switch to the capacitor voltage average value control mode through the receiving-end AC fault signal, so as to stabilize the capacitor voltage of the sub-module in the sending-end converter. Obtain the average value of the capacitor voltage of the sending-end converter and the reference value of the capacitor voltage of the sending-end converter; The change in capacitor voltage of the sending-end converter under the fault condition of the receiving-end AC system is obtained by the difference between the square of the average capacitor voltage and the square of the reference capacitor voltage. By performing proportional-integral control on the change in capacitor voltage, the change in the reference DC voltage of the sending-end converter is obtained. The change in the reference DC voltage and the reference DC voltage of the sending-end converter are superimposed to obtain the target reference DC voltage of the sending-end converter. The output power of the DC side of the sending-end converter is controlled according to the target DC voltage reference value until the capacitor voltage of the sending-end converter is in a stable state, and then the capacitor voltage average value control mode is exited.

2. The method according to claim 1, characterized in that, Before the control of the sending-end converter to switch the capacitor voltage average value control mode, the method further includes: If the average value of the capacitor voltage is greater than the reference value of the capacitor voltage, the sending-end converter is controlled to switch to the average value control mode of the capacitor voltage.

3. The method according to claim 1, characterized in that, The method further includes: When exiting the capacitor voltage average value control mode, the change in the DC voltage reference value of the sending-end converter is obtained; The DC voltage reference value is controlled to change linearly to zero at a set rate.

4. The method according to claim 1, characterized in that, The step of controlling the sending-end converter to switch to capacitor voltage average value control mode when a receiving-end AC fault signal is received from the receiving-end AC system includes: When a receiving-end AC fault signal is received from the receiving-end AC system, the sending-end converter is controlled to switch to the average capacitor voltage control mode, and a timer is triggered to start timing, and the steps of obtaining the average capacitor voltage of the sending-end converter and the reference value of the capacitor voltage of the sending-end converter are executed. The step of controlling the output power of the DC side of the sending-end converter according to the target sending-end DC voltage reference value until the capacitor voltage of the sending-end converter is in a stable state includes: The output power of the DC side of the sending-end converter is controlled according to the target sending-end DC voltage reference value, and the timing duration of the timer is obtained. If the timing duration reaches the preset duration and the fault in the receiving-end AC system is cleared, it indicates that the capacitor voltage of the sending-end converter is in a stable state; wherein, the preset duration is longer than the fault clearing duration of the receiving-end AC system.

5. The method according to claim 4, characterized in that, The method further includes: If the timing duration reaches the preset duration and the fault in the receiving-end AC system is not cleared, the timer is triggered to restart the timing, and the step of controlling the sending-end converter to switch to the capacitor voltage average value control mode is executed until the capacitor voltage of the sending-end converter is in a stable state, and then the capacitor voltage average value control mode is exited.

6. A flexible DC receiving-end AC fault ride-through system, the system comprising a receiving-end AC system, a receiving-end converter, and a sending-end converter, wherein the receiving-end AC system is connected to the receiving-end converter, the receiving-end converter and the sending-end converter are connected via a DC line, the receiving-end converter includes a first control module, and the sending-end converter includes a second control module, characterized in that, in: The first control module is used to detect a transmitting fault in the receiving-end AC system, acquire the receiving-end AC fault signal of the receiving-end AC system, and send the receiving-end AC fault signal to the sending-end converter. The second control module is used to, upon receiving a receiving-end AC fault signal from the receiving-end AC system, control the sending-end converter to switch to an average capacitor voltage control mode via the receiving-end AC fault signal, so as to stabilize the capacitor voltage of the sub-modules in the sending-end converter; and to obtain the average capacitor voltage and reference value of the capacitor voltage of the sending-end converter. The change in capacitor voltage of the sending-end converter under the condition of a fault in the receiving-end AC system is obtained by the difference between the square of the average capacitor voltage and the square of the reference capacitor voltage. The change in DC voltage reference value of the sending-end converter is obtained by performing proportional-integral control on the change in capacitor voltage. The change in DC voltage reference value and the reference DC voltage of the sending-end converter are superimposed to obtain the target reference DC voltage of the sending-end converter. The output power of the DC side of the sending-end converter is controlled according to the target reference DC voltage until the capacitor voltage of the sending-end converter is in a stable state, at which point the capacitor voltage average value control mode is exited.

7. The system according to claim 6, characterized in that, The receiving-end converter also includes a judgment module; The judgment module detects whether the average value of the capacitor voltage is greater than the reference value of the capacitor voltage. If so, it controls the sending-end converter to switch to the average value control mode of the capacitor voltage.

8. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 5.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 5.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 5.

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