Sending-end flexible direct current converter station, control method and device thereof, and storage medium

Abstract

The application relates to a sending-end flexible DC converter station, a control method and device thereof and a storage medium. The method comprises the following steps: after detecting that a power grid where the sending-end flexible DC converter station is located has a fault, a fault pole of the sending-end flexible DC converter station is controlled by a capacitor voltage average value and an alternating current voltage, so as to perform negative sequence current control, and a non-fault pole of the sending-end flexible DC converter station is kept to perform voltage frequency conversion control, so as to output an alternating current voltage; after a preset time, the sending-end flexible DC converter station is restarted. The application can improve the stability of capacitor voltage in the sending-end flexible DC converter station.

Description

Technical Field

[0001] This application relates to the field of power technology, and in particular to a sending-end flexible DC converter station, its control method, apparatus and storage medium. Background Technology

[0002] In a flexible DC grid, renewable energy sources are connected to the grid in an islanded manner. Due to the difficulty in matching the voltage and current growth rate after a DC grid line fault with the timing of disconnecting renewable energy units through AC safety control devices, especially under the condition of full-power connection of renewable energy sources in islanded mode, any disturbance may cause surplus power in the flexible DC grid, thereby leading to a large-scale paralysis of the flexible DC grid.

[0003] To avoid the aforementioned problems, the current approach involves maintaining VF (volt-frequency control) at the sending-end flexible DC converter station and absorbing surplus power using a power-dissipating resistor in the sending-end AC subsystem. After a certain period, the sending-end flexible DC converter station is restarted, and the power-dissipating resistor is disconnected. However, this method can cause the capacitor voltage of the sending-end flexible DC submodule in the flexible DC grid to rise, posing a risk of overvoltage. Summary of the Invention

[0004] Therefore, it is necessary to provide a flexible DC converter station at the sending end that can maintain stable capacitor voltage, as well as its control method, device, and storage medium, to address the aforementioned technical problems.

[0005] In a first aspect, this application provides a control method for a sending-end flexible DC converter station, the method comprising:

[0006] After a fault is detected in the DC line connected to the sending-end flexible DC converter station, the faulty pole of the sending-end flexible DC converter station is controlled by the average capacitor voltage, AC voltage, and negative sequence current, while the non-faulty pole of the sending-end flexible DC converter station is kept under voltage frequency conversion control to output AC voltage.

[0007] After a preset time, the sending-end flexible DC converter station is restarted.

[0008] In one embodiment, after detecting a fault in the DC line connected to the sending-end flexible DC converter station, the fault pole of the sending-end flexible DC converter station is controlled by capacitor voltage average value control, AC voltage control, and negative sequence current control, including:

[0009] Obtain the actual capacitor voltage of the converter submodule in the sending-end flexible DC converter station, and calculate the difference between the squared difference between the actual capacitor voltage and the preset capacitor reference value.

[0010] The control value of the d-axis component of the AC current is generated based on the squared difference.

[0011] In one embodiment, the step of controlling the fault pole of the sending-end flexible DC converter station through capacitor voltage average value control, AC voltage control, and negative sequence current control after detecting a fault in the DC line connected to the sending-end flexible DC converter station further includes:

[0012] The actual value of the current AC voltage of the sending-end flexible DC converter station is obtained, and the control value of the AC current q-axis component is generated based on the difference between the preset AC voltage reference value and the actual AC voltage value.

[0013] The first modulation wave is generated based on the control values ​​of the d-axis component and the q-axis component of the AC current.

[0014] In one embodiment, the method further includes:

[0015] Detect the voltage of the sending-end AC subsystem in the power grid;

[0016] When the voltage of the AC subsystem at the sending end exceeds a preset voltage, a power-consuming resistor is connected to the AC subsystem at the sending end.

[0017] In one embodiment, the method further includes:

[0018] After the flexible DC converter station at the sending end is restarted, the energy-consuming resistor is disconnected.

[0019] In one embodiment, before the step of controlling the faulty pole of the sending-end flexible DC converter station through capacitor voltage average value control, AC voltage control, and negative sequence current control, and maintaining the non-faulty pole of the sending-end flexible DC converter station under voltage frequency conversion control to perform AC voltage output after detecting a fault in the DC line connected to the sending-end flexible DC converter station, includes:

[0020] Obtain the first current value of the faulty pole of the sending-end flexible DC converter station before the fault occurs, and the second current value of the non-faulty pole.

[0021] The restarting of the sending-end flexible DC converter station includes:

[0022] The actual value of the first current of the faulty pole and the actual value of the second current of the non-faulty pole in the sending-end flexible DC converter station are obtained respectively.

[0023] The difference between the actual value of the first current and the first current value is input to the input of the proportional-integral controller to obtain the first voltage reference change, and the difference between the actual value of the second current and the second current value is input to the input of the proportional-integral controller to obtain the second voltage reference change.

[0024] The first voltage reference change and the preset voltage reference value are superimposed and then input into the modulation module to control the output of the corresponding DC voltage of the faulty pole. The second voltage reference change and the preset voltage reference value are superimposed and then input into the modulation module to control the output of the corresponding DC voltage of the non-faulty pole.

[0025] Secondly, this application also provides a restart device for a sending-end flexible DC converter station, the device comprising:

[0026] The first control module is used to, after detecting a fault in the DC line connected to the sending-end flexible DC converter station, control the faulty pole of the sending-end flexible DC converter station through capacitor voltage average value control, AC voltage control and negative sequence current control, and maintain the non-faulty pole of the sending-end flexible DC converter station to maintain voltage frequency change control, so as to output AC voltage.

[0027] The restart module is used to restart the sending-end flexible DC converter station after a preset time.

[0028] 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:

[0029] After a fault is detected in the DC line connected to the sending-end flexible DC converter station, the faulty pole of the sending-end flexible DC converter station is controlled by the average capacitor voltage, AC voltage, and negative sequence current, while the non-faulty pole of the sending-end flexible DC converter station is kept under voltage frequency conversion control to output AC voltage.

[0030] After a preset time, the sending-end flexible DC converter station is restarted.

[0031] 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:

[0032] After a fault is detected in the DC line connected to the sending-end flexible DC converter station, the faulty pole of the sending-end flexible DC converter station is controlled by the average capacitor voltage, AC voltage, and negative sequence current, while the non-faulty pole of the sending-end flexible DC converter station is kept under voltage frequency conversion control to output AC voltage.

[0033] After a preset time, the sending-end flexible DC converter station is restarted.

[0034] 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:

[0035] After a fault is detected in the DC line connected to the sending-end flexible DC converter station, the faulty pole of the sending-end flexible DC converter station is controlled by the average capacitor voltage, AC voltage, and negative sequence current, while the non-faulty pole of the sending-end flexible DC converter station is kept under voltage frequency conversion control to output AC voltage.

[0036] After a preset time, the sending-end flexible DC converter station is restarted.

[0037] The aforementioned sending-end flexible DC converter station, its control method, apparatus, and storage medium include the following method: after detecting a fault in the DC line connected to the sending-end flexible DC converter station, controlling the faulty pole of the sending-end flexible DC converter station through capacitor voltage averaging control, AC voltage control, and negative sequence current control, while maintaining voltage frequency conversion control on the non-faulty pole of the sending-end flexible DC converter station to output AC voltage; after a preset time, restarting the sending-end flexible DC converter station. Through this method, after detecting a fault in the DC line connected to the sending-end flexible DC converter station, this application controls the faulty pole of the sending-end flexible DC converter station through capacitor voltage averaging control, AC voltage control, and negative sequence current control to change the AC voltage output of the faulty pole. The capacitor voltage averaging control stabilizes the capacitor voltage, preventing it from rising, thereby safely achieving fault ride-through in the power grid system. After fault ride-through, the sending-end flexible DC converter station is restarted normally. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the system structure of the power grid where the sending-end flexible DC converter station is located in one embodiment.

[0039] Figure 2 This is a flowchart illustrating the control method for a sending-end flexible DC converter station in one embodiment;

[0040] Figure 3 This is a schematic diagram of the signal flow controlled by the average capacitor voltage in one embodiment;

[0041] Figure 4 This is a schematic diagram of the signal flow for AC voltage control in one embodiment;

[0042] Figure 5 This is a flowchart illustrating the control method for the sending-end flexible DC converter station in another embodiment;

[0043] Figure 6This is a flowchart illustrating the control method for the sending-end flexible DC converter station in yet another embodiment;

[0044] Figure 7 This is a schematic diagram of the signal flow of the faulty pole portion when restarting the sending-end flexible DC converter station in one embodiment;

[0045] Figure 8 This is a schematic diagram illustrating the signal flow of the non-faulty pole portion of the sending-end flexible DC converter station in one embodiment.

[0046] Figure 9 This is a schematic diagram of the restart device of the sending-end flexible DC converter station in one embodiment;

[0047] Figure 10 This is an internal structural diagram of the sending-end flexible DC converter station in one embodiment. Detailed Implementation

[0048] 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.

[0049] This application applies to, for example Figure 1 The power grid shown includes:

[0050] The sending-end AC subsystem 40, the sending-end flexible DC converter station 10, the DC line 20, the receiving-end flexible DC converter station 30, and the receiving-end AC subsystem 50 are connected in sequence.

[0051] During operation, the receiving-end flexible DC converter station 30 is first charged using an external power source. After charging is complete, the receiving-end flexible DC converter station 30 is unlocked, and then it can output charging voltage to the sending-end flexible DC converter station 10, thereby charging the sending-end flexible DC converter station 10 until its voltage reaches the rated voltage. Once the voltage of the sending-end flexible DC converter station 10 reaches the rated voltage, it can be used as the starting power source for the sending-end AC station.

[0052] It should be noted that both the sending-end flexible DC converter station 10 and the receiving-end flexible DC converter station 30 are in a locked state before charging is completed, meaning that no load current flows through either station. Once charging is complete, the receiving-end flexible DC converter station 30 is unlocked.

[0053] The sending-end AC subsystem 40 includes a new energy generator unit. Because the sending-end AC subsystem 40 does not have a conventional power supply in traditional technology, the new energy generator unit requires voltage from the sending-end flexible DC converter station 10 to start. Therefore, after the sending-end flexible DC converter station 10 reaches its rated voltage, the sending-end flexible DC converter station 10 is unlocked, allowing it to supply power to the sending-end AC subsystem 40 and start it.

[0054] When the system is working normally, the electrical energy output by the sending-end AC subsystem 40 passes through the sending-end flexible DC converter station 10, DC line 20 and receiving-end flexible DC converter station 30 in sequence, and then is output to the corresponding electrical equipment through the receiving-end AC subsystem 50.

[0055] The sending-end flexible DC converter station 10 includes multiple capacitors. In order to avoid overvoltage of the capacitors in the sending-end flexible DC converter station 10 caused by restarting the sending-end flexible DC converter station 10 using conventional technology after a grid fault, this application provides a control method for the sending-end flexible DC converter station.

[0056] In one embodiment, see Figure 2 This paper provides a control method for a sending-end flexible DC converter station, which is applied to applications such as... Figure 1 The image shows a sending-end flexible DC converter station or a control device within a sending-end flexible DC converter station. This application uses the application of this method to a sending-end flexible DC converter station as an example for illustration. The control method for this sending-end flexible DC converter station includes:

[0057] Step 100: After detecting a fault in the DC line connected to the sending-end flexible DC converter station, the faulty pole of the sending-end flexible DC converter station is controlled by the average capacitor voltage, AC voltage, and negative sequence current, while the non-faulty pole of the sending-end flexible DC converter station is kept under voltage frequency conversion control to output AC voltage.

[0058] Specifically, the sending-end flexible DC converter station acquires the DC voltage and DC current of the power grid, and determines whether a fault has occurred in the DC line connected to the sending-end flexible DC converter station based on the grid's DC voltage and DC current. After detecting a fault in the DC line connected to the sending-end flexible DC converter station, the sending-end flexible DC converter station determines the faulty and non-faulty poles within the station. It should be noted that the sending-end flexible DC converter station includes a positive and a negative pole; that is, the positive pole can be either a faulty or non-faulty pole, and the negative pole can also be either a faulty or non-faulty pole.

[0059] The sending-end flexible DC converter station switches the faulty unit from VF control (volt-frequency conversion control) to capacitor voltage average value control, AC voltage control, and negative sequence current control; at the same time, it maintains the non-faulty poles of the sending-end flexible DC converter station under voltage-frequency conversion control to output AC voltage.

[0060] By maintaining voltage frequency conversion control on the non-faulty unit, a stable AC voltage can continue to be supplied to the sending-end AC subsystem. Simultaneously, switching the faulty unit from voltage frequency conversion control to capacitor voltage averaging control, AC voltage control, and negative sequence current control alters the output AC voltage.

[0061] As an example, the fault pole of the sending-end flexible DC converter station is controlled by capacitor voltage average value control, AC voltage control, and negative sequence current control, including:

[0062] Obtain the actual capacitor voltage of the converter submodule in the sending-end flexible DC converter station, and calculate the difference between the squared difference between the actual capacitor voltage and the preset capacitor reference value.

[0063] The control value of the d-axis component of the AC current is generated based on the squared difference.

[0064] Specifically, the process of controlling the average capacitor voltage includes: acquiring the actual capacitor voltage of the converter submodule in the sending-end flexible DC converter station; calculating the squared difference between the actual capacitor voltage and the preset capacitor reference value; and generating the AC current d-axis component control value based on the obtained squared difference. The AC current d-axis component refers to the AC current decomposition component on the d-axis of the coordinate system, with the q-axis perpendicular to the d-axis.

[0065] The above process can also be achieved through, for example... Figure 3 The circuit shown in the diagram uses a subtractor to obtain the square difference between the actual capacitor voltage and the square of the preset capacitor reference value. This square difference is then input into a proportional-integral controller (PI controller) to generate the control value of the AC current d-axis component.

[0066] As an example, the method of controlling the fault pole of the sending-end flexible DC converter station through capacitor voltage average value control, AC voltage control, and negative sequence current control further includes:

[0067] The first modulation wave is generated based on the control values ​​of the d-axis component and the q-axis component of the AC current.

[0068] Specifically, AC voltage control may include: acquiring the actual AC voltage value at the sending-end flexible DC converter station, then subtracting the actual AC voltage value from a preset AC voltage reference value to obtain the difference, and generating an AC current q-axis component control value based on the obtained difference. The AC current q-axis component refers to the AC current decomposition component on the q-axis of the coordinate system.

[0069] The above process can also be achieved through, for example... Figure 4 The circuit shown is implemented by subtracting the preset current reference value and the first actual current value to obtain the difference between the preset current reference value and the first actual current value. The obtained difference is then input into the proportional-integral controller (PI controller) to generate the AC current q-axis component control value.

[0070] Then, a first modulation wave is generated based on the control values ​​of the d-axis component and the q-axis component of the AC current, and a second modulation wave is generated based on the negative sequence current control. Finally, the sending-end flexible DC converter station is turned on or off based on the first and second modulation waves to change the AC voltage output by the sending-end flexible DC converter station.

[0071] Step 200: After a preset time, restart the sending-end flexible DC converter station.

[0072] After controlling the preset time in the above manner, that is, waiting for the sending-end flexible DC converter station to eliminate the fault (this process is referred to in the art as fault ride-through), for example, the preset time is between 400 and 500 milliseconds, and then the sending-end flexible DC converter station can be restarted. The process of restarting the sending-end flexible DC converter station can be the same as the prior art, and will not be described in detail here.

[0073] The control method for the aforementioned sending-end flexible DC converter station includes: after detecting a fault in the DC line connected to the sending-end flexible DC converter station, controlling the faulty pole of the sending-end flexible DC converter station through capacitor voltage averaging control, AC voltage control, and negative sequence current control, while maintaining voltage frequency conversion control on the non-faulty pole of the sending-end flexible DC converter station to output AC voltage; after a preset time, restarting the sending-end flexible DC converter station. Through this method, after detecting a fault in the DC line connected to the sending-end flexible DC converter station, this application controls the faulty pole of the sending-end flexible DC converter station through capacitor voltage averaging control, AC voltage control, and negative sequence current control to change the AC voltage output of the faulty pole. The capacitor voltage averaging control stabilizes the capacitor voltage, preventing it from rising, thereby safely achieving fault ride-through in the power grid system. After fault ride-through, the sending-end flexible DC converter station is restarted normally.

[0074] In one embodiment, based on the above embodiments, such as Figure 5As shown, the method also includes:

[0075] Step 300: Detect the voltage of the sending-end AC subsystem in the power grid;

[0076] Step 400: After the voltage of the AC subsystem at the sending end is greater than the preset voltage, control the connection of the energy-consuming resistor to the AC subsystem at the sending end.

[0077] Step 500: After the flexible DC converter station at the sending end is restarted, the energy-consuming resistor is disconnected.

[0078] Specifically, before restarting the sending-end flexible DC converter station, during the process of controlling the faulty pole of the sending-end flexible DC converter station through capacitor voltage averaging and AC voltage control, the sending-end flexible DC converter station also detects the voltage of the sending-end AC subsystem in the power grid. It determines whether the voltage of the sending-end AC subsystem is greater than a preset voltage. If the voltage of the sending-end AC subsystem is greater than the preset voltage, an energy-dissipating resistor is connected to the sending-end AC subsystem to consume energy. After the sending-end flexible DC converter station restarts, the energy-dissipating resistor is disconnected. The process of connecting and disconnecting the energy-dissipating resistor in the sending-end AC subsystem is the same as in existing technology and will not be described again here.

[0079] In one embodiment, based on the above embodiments, such as Figure 6 As shown, after a fault is detected in the DC line connected to the sending-end flexible DC converter station, before the faulty pole of the sending-end flexible DC converter station is controlled by capacitor voltage average value control, AC voltage control, and negative sequence current control, and the non-faulty pole of the sending-end flexible DC converter station is kept under voltage frequency conversion control for AC voltage output, the following steps are also included:

[0080] Step 600: Obtain the first current value of the faulty pole of the sending-end flexible DC converter station before the fault occurs, and the second current value of the non-faulty pole.

[0081] Specifically, the sending-end flexible DC converter station records its current value in real time. After a fault is detected in the power grid where the sending-end flexible DC converter station is located, the current of the faulty pole and the non-faulty pole before the fault occurred is obtained. For ease of description, the current of the faulty pole is defined as the first current value, and the current of the non-faulty pole is defined as the second current value.

[0082] Correspondingly, the steps for restarting the sending-end flexible DC converter station include:

[0083] Step 210: Obtain the actual value of the first current of the faulty pole and the actual value of the second current of the non-faulty pole in the sending-end flexible DC converter station respectively.

[0084] Step 220: Input the difference between the actual value of the first current and the first current value to the input of the proportional-integral controller to obtain the first voltage reference change, and input the difference between the actual value of the second current and the second current value to the input of the proportional-integral controller to obtain the second voltage reference change;

[0085] Step 230: The first voltage reference change and the preset voltage reference value are superimposed and input into the modulation module to control the faulty pole to output the corresponding DC voltage, and the second voltage reference change and the preset voltage reference value are superimposed and input into the modulation module to control the non-faulty pole to output the corresponding DC voltage.

[0086] During the restart process, this embodiment also obtains the current of the faulty pole in the sending-end flexible DC converter station, which is defined as the first actual current value, and the current of the non-faulty pole, which is defined as the second actual current value.

[0087] The difference between the actual value of the first current and the first current value is input to the input of the proportional-integral controller to obtain the first voltage reference change. Then, the first voltage reference change is superimposed with a preset voltage reference value and input to the modulation module to control the fault electrode to output the corresponding DC voltage in a voltage frequency conversion control manner. Figure 7 As shown.

[0088] Simultaneously, the difference between the actual value of the second current and the value of the second current is input to the input of the proportional-integral controller to obtain the second voltage reference change. Then, the second voltage reference change is superimposed with the preset voltage reference value and input to the modulation module to control the non-faulty pole to output the corresponding DC voltage in a voltage frequency conversion control manner, such as... Figure 8 As shown.

[0089] In this way, the faulty and non-faulty poles in the sending-end flexible DC converter station are modulated separately, restoring them to their pre-fault state, enabling the power grid to quickly return to normal operation. It should be noted that steps 210 to 230 can also be executed after restarting the sending-end flexible DC converter station.

[0090] As explained above, since the faulty pole is connected to both the AC system and the DC line, and the non-faulty pole is the same, both the faulty and non-faulty poles simultaneously output AC and DC voltages. This modulation process can be understood as changing the AC and DC voltages during the restart of the sending-end flexible DC converter station; or changing the AC voltage during the restart of the sending-end flexible DC converter station, and then changing the DC voltage after restarting. In existing technology, the DC voltage of the sending-end flexible DC converter station is output according to a preset value, while this application changes the DC voltage according to a reference value, which can correspondingly adjust the power on the sending-end DC side and accelerate the restoration of the DC current to its pre-fault state.

[0091] Based on the same inventive concept, this application also provides a restart device for implementing the control method of the sending-end flexible DC converter station mentioned above. The solution provided by this restart device is similar to the implementation solution described in the above system. Therefore, the specific limitations of one or more restart device embodiments provided below can be found in the limitations of the control method above, and will not be repeated here.

[0092] In one embodiment, such as Figure 9 As shown, a restart device for a sending-end flexible DC converter station is provided, the restart device comprising:

[0093] The first control module 910 is used to, after detecting a fault in the DC line connected to the sending-end flexible DC converter station, control the faulty pole of the sending-end flexible DC converter station through capacitor voltage average value control, AC voltage control and negative sequence current control, and maintain the non-faulty pole of the sending-end flexible DC converter station to maintain voltage frequency change control, so as to output AC voltage.

[0094] The restart module 920 is used to restart the sending-end flexible DC converter station after a preset time.

[0095] In one embodiment, the first control module 910 is further configured to:

[0096] Obtain the actual capacitor voltage of the converter submodule in the sending-end flexible DC converter station, and calculate the difference between the squared difference between the actual capacitor voltage and the preset capacitor reference value.

[0097] The control value of the d-axis component of the AC current is generated based on the squared difference.

[0098] In one embodiment, the first control module 910 is further configured to:

[0099] The actual value of the current AC voltage of the sending-end flexible DC converter station is obtained, and the control value of the AC current q-axis component is generated based on the difference between the preset AC voltage reference value and the actual AC voltage value.

[0100] The first modulation wave is generated based on the control values ​​of the d-axis component and the q-axis component of the AC current.

[0101] In one embodiment, the device further includes:

[0102] A detection module (not shown) is used to detect the voltage of the sending-end AC subsystem in the power grid;

[0103] The second control module (not shown in the figure) is used to control the connection of a power-consuming resistor to the AC subsystem at the sending end after the voltage of the AC subsystem at the sending end is greater than the preset voltage.

[0104] In one embodiment, the device further includes:

[0105] The third control module (not shown) is used to control the energy-consuming resistor to disconnect after the flexible DC converter station at the sending end is restarted.

[0106] The first control module, the second control module, and the third control module can be the same module or different modules.

[0107] In one embodiment, the device further includes:

[0108] The current acquisition module (not shown in the figure) is used to acquire the first current value of the faulty pole of the sending-end flexible DC converter station before the fault occurs, and the second current value of the non-faulty pole.

[0109] Restart module 920 is also used for:

[0110] The actual value of the first current of the faulty pole and the actual value of the second current of the non-faulty pole in the sending-end flexible DC converter station are obtained respectively.

[0111] The difference between the actual value of the first current and the first current value is input to the input of the proportional-integral controller to obtain the first voltage reference change, and the difference between the actual value of the second current and the second current value is input to the input of the proportional-integral controller to obtain the second voltage reference change.

[0112] The first voltage reference change and the preset voltage reference value are superimposed and then input into the modulation module to control the output of the corresponding DC voltage of the faulty pole. The second voltage reference change and the preset voltage reference value are superimposed and then input into the modulation module to control the output of the corresponding DC voltage of the non-faulty pole.

[0113] It should be understood that although the steps in the flowcharts of the embodiments described above 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 embodiments described above 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.

[0114] In one embodiment, a sending-end flexible DC converter station is provided, the internal structure of which can be shown in the following diagram. Figure 10 As shown, the computer device includes a processor, memory, and network interface 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, computer programs, and a database. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage media. The database can be used to store data such as current and voltage of the sending-end flexible DC converter station. The network interface is used for communication with external terminals via a network connection. When the computer program is executed by the processor, it implements a control method for the sending-end flexible DC converter station.

[0115] Those skilled in the art will understand that Figure 10 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 sending-end flexible DC converter station to which the present application is applied. A specific sending-end flexible DC converter station may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0116] In one embodiment, a sending-end flexible DC converter station is provided, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to perform the following steps:

[0117] After a fault is detected in the DC line connected to the sending-end flexible DC converter station, the faulty pole of the sending-end flexible DC converter station is controlled by the average capacitor voltage, AC voltage, and negative sequence current, while the non-faulty pole of the sending-end flexible DC converter station is kept under voltage frequency conversion control to output AC voltage.

[0118] After a preset time, the sending-end flexible DC converter station is restarted.

[0119] In one embodiment, the processor, when executing a computer program, also performs the following steps:

[0120] Obtain the actual capacitor voltage of the converter submodule in the sending-end flexible DC converter station, and calculate the difference between the squared difference between the actual capacitor voltage and the preset capacitor reference value.

[0121] The control value of the d-axis component of the AC current is generated based on the squared difference.

[0122] In one embodiment, the processor, when executing a computer program, also performs the following steps:

[0123] The actual value of the current AC voltage of the sending-end flexible DC converter station is obtained, and the control value of the AC current q-axis component is generated based on the difference between the preset AC voltage reference value and the actual AC voltage value.

[0124] The first modulation wave is generated based on the control values ​​of the d-axis component and the q-axis component of the AC current.

[0125] In one embodiment, the processor, when executing a computer program, also performs the following steps:

[0126] Detect the voltage of the sending-end AC subsystem in the power grid;

[0127] When the voltage of the AC subsystem at the sending end exceeds a preset voltage, a power-consuming resistor is connected to the AC subsystem at the sending end.

[0128] In one embodiment, the processor, when executing a computer program, also performs the following steps:

[0129] After the flexible DC converter station at the sending end is restarted, the energy-consuming resistor is disconnected.

[0130] In one embodiment, the processor, when executing a computer program, also performs the following steps:

[0131] Obtain the first current value of the faulty pole of the sending-end flexible DC converter station before the fault occurs, and the second current value of the non-faulty pole.

[0132] The restarting of the sending-end flexible DC converter station includes:

[0133] The actual value of the first current of the faulty pole and the actual value of the second current of the non-faulty pole in the sending-end flexible DC converter station are obtained respectively.

[0134] The difference between the actual value of the first current and the first current value is input to the input of the proportional-integral controller to obtain the first voltage reference change, and the difference between the actual value of the second current and the second current value is input to the input of the proportional-integral controller to obtain the second voltage reference change.

[0135] The first voltage reference change and the preset voltage reference value are superimposed and then input into the modulation module to control the output of the corresponding DC voltage of the faulty pole. The second voltage reference change and the preset voltage reference value are superimposed and then input into the modulation module to control the output of the corresponding DC voltage of the non-faulty pole.

[0136] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the steps of the control method for the sending-end flexible DC converter station as described in any of the above embodiments.

[0137] In one embodiment, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps of the control method for a sending-end flexible DC converter station as described in any of the above embodiments.

[0138] 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, and when executed, it 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.

[0139] 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.

[0140] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent 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 control method for a sending-end flexible DC converter station, characterized in that, The method includes: After a fault is detected in the DC line connected to the sending-end flexible DC converter station, the faulty pole of the sending-end flexible DC converter station is controlled by the average capacitor voltage, AC voltage, and negative sequence current, while the non-faulty pole of the sending-end flexible DC converter station is kept under voltage frequency conversion control to output AC voltage. After a preset time, the sending-end flexible DC converter station is restarted; Before the AC voltage output is initiated, after a fault is detected in the DC line connected to the sending-end flexible DC converter station, the faulty pole of the sending-end flexible DC converter station is controlled by capacitor voltage average value control, AC voltage control, and negative sequence current control, while the non-faulty pole of the sending-end flexible DC converter station is kept under voltage frequency conversion control. Obtain the first current value of the faulty pole of the sending-end flexible DC converter station before the fault occurs, and the second current value of the non-faulty pole. The restarting of the sending-end flexible DC converter station includes: The actual value of the first current of the faulty pole and the actual value of the second current of the non-faulty pole in the sending-end flexible DC converter station are obtained respectively. The difference between the actual value of the first current and the first current value is input to the input of the proportional-integral controller to obtain the first voltage reference change, and the difference between the actual value of the second current and the second current value is input to the input of the proportional-integral controller to obtain the second voltage reference change. The first voltage reference change and the preset voltage reference value are superimposed and then input into the modulation module to control the output of the corresponding DC voltage of the faulty pole. The second voltage reference change and the preset voltage reference value are superimposed and then input into the modulation module to control the output of the corresponding DC voltage of the non-faulty pole.

2. The method according to claim 1, characterized in that, The method of controlling the fault pole of the sending-end flexible DC converter station through capacitor voltage average value control, AC voltage control, and negative sequence current control includes: Obtain the actual capacitor voltage of the converter submodule in the sending-end flexible DC converter station, and calculate the difference between the squared difference between the actual capacitor voltage and the preset capacitor reference value. The control value of the d-axis component of the AC current is generated based on the squared difference.

3. The method according to claim 2, characterized in that, The method of controlling the fault pole of the sending-end flexible DC converter station through capacitor voltage average value control, AC voltage control, and negative sequence current control further includes: The actual value of the current AC voltage of the sending-end flexible DC converter station is obtained, and the control value of the AC current q-axis component is generated based on the difference between the preset AC voltage reference value and the actual AC voltage value. The first modulation wave is generated based on the control values ​​of the d-axis component and the q-axis component of the AC current.

4. The method according to claim 1, characterized in that, Before restarting the sending-end flexible DC converter station after a preset time, the process includes: Detecting the voltage of the AC subsystem at the sending end of the power grid; When the voltage of the AC subsystem at the sending end exceeds a preset voltage, a power-consuming resistor is connected to the AC subsystem at the sending end.

5. The method according to claim 4, characterized in that, The method further includes: After the flexible DC converter station at the sending end is restarted, the energy-consuming resistor is disconnected.

6. A restart device for a sending-end flexible DC converter station, characterized in that, The device includes: The first control module is used to, after detecting a fault in the DC line connected to the sending-end flexible DC converter station, control the faulty pole of the sending-end flexible DC converter station through capacitor voltage average value control, AC voltage control and negative sequence current control, and maintain the non-faulty pole of the sending-end flexible DC converter station to maintain voltage frequency change control, so as to output AC voltage. The restart module is used to restart the sending-end flexible DC converter station after a preset time. The current acquisition module is used to acquire the first current value of the faulty pole of the sending-end flexible DC converter station before the fault occurs, and the second current value of the non-faulty pole. The restart module is also used to acquire the first actual current value of the faulty pole and the second actual current value of the non-faulty pole in the sending-end flexible DC converter station; input the difference between the first actual current value and the first current value to the input of the proportional-integral controller to obtain the first voltage reference change, and input the difference between the second actual current value and the second current value to the input of the proportional-integral controller to obtain the second voltage reference change; superimpose the first voltage reference change and a preset voltage reference value and input the result to the modulation module to control the output of the corresponding DC voltage of the faulty pole, and superimpose the second voltage reference change and the preset voltage reference value and input the result to the modulation module to control the output of the corresponding DC voltage of the non-faulty pole.

7. A sending-end flexible DC converter station, 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.

8. 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.

9. 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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