Flexible direct current power transmission system, line ice melting method and related products

Abstract

The embodiment of the invention relates to the technical field of line control, and provides a flexible direct current power transmission system, a line ice melting method and a related product. When the flexible direct current power transmission system is in a normal operation mode, a line selection switch group, a bypass switch, a metal loop switch and a ground loop switch are controlled; therefore, each converter valve group and the DC line form a series loop. And when the flexible direct-current power transmission system is in an ice melting mode, the line selection switch group, the bypass switch, the metal loop switch and the ground loop switch are controlled, so that the first converter valve group, the second converter valve group and the fourth converter valve group form a parallel loop, and the parallel loop is connected with a direct-current line. According to the embodiment of the invention, the line selection switch is added through a mode of realizing wire ice melting based on the flexible direct current power transmission system, and the current of the direct current side is improved through parallel connection of multiple valve groups and poles, so that line ice melting of the direct current power transmission system is realized.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of line control technology, and in particular to a flexible direct current transmission system, a line de-icing method, and related products. Background Art

[0002] Compared with other natural disasters, ice disasters cause more serious losses to the power system. At the mildest, ice flashes occur, and at the worst, tower collapses and line breaks occur, or even the power grid is paralyzed. There is a need to melt the ice on the conductors.

[0003] In the relevant technologies for conductor de-icing, DC de-icing devices with dedicated rectifier transformers and DC de-icing devices without dedicated rectifier transformers can be used. However, the operating current of the DC transmission system is generally large. When the DC transmission line is covered with ice, its de-icing current is often large. If the above-mentioned DC de-icing device is used for de-icing, the required de-icing device capacity is relatively large, which is often not achievable due to the limitations of current equipment capabilities. Usually, the above-mentioned DC transmission system is used to de-icer before de-icing, but this de-icing method requires maintaining a high DC current in the DC line. However, with the development of large-scale wasteland, the DC transmission system is often unable to maintain a high DC current at night when ice is prone to accumulation, which will greatly increase the risk of conductor de-icing in the DC transmission system. Summary of the Invention

[0004] The embodiments of the present application provide a flexible direct current transmission system, a line de-icing method, and related products, which can achieve line de-icing based on the flexible direct current transmission system itself without the need for power outages by adding a line selection switch.

[0005] In one aspect, an embodiment of the present application provides a flexible direct current (HVDC) power transmission system, comprising a sending-end converter station and a receiving-end converter station, wherein a DC line is connected between the sending-end converter station and the receiving-end converter station, wherein the sending-end converter station and the receiving-end converter station respectively comprise a bus positive pole and a bus negative pole, wherein a first converter valve group and a second converter valve group are provided at the bus positive pole in each converter station, and a third converter valve group and a fourth converter valve group are provided at the bus negative pole in each converter station, wherein each converter valve group is connected in parallel with a bypass switch, a metal return line switch is connected between the pole line and the neutral line of the same pole, an earth return line switch is connected between the neutral line and the grounding pole line, and a line selection switch group is provided between the first converter valve group and the second converter valve group;

[0006] When the flexible direct current transmission system is in a normal operating mode, the line selection switch group, the bypass switch, the metal return line switch, and the earth return line switch are controlled so that each converter valve group forms a series circuit with the direct current line; when the flexible direct current transmission system is in an ice-melting mode, the line selection switch group, the bypass switch, the metal return line switch, and the earth return line switch are controlled so that the first converter valve group, the second converter valve group, and the fourth converter valve group form a parallel circuit, and the parallel circuit is connected to the direct current line.

[0007] In some embodiments of the present application, each line selection switch group includes a first switch, a second switch, a third switch, a fourth switch, and a fifth switch, and the first switch, the second switch, the third switch, the fourth switch, and the fifth switch are connected in parallel.

[0008] In some embodiments of the present application, when the flexible direct current transmission system is in normal operating mode, the first switch and the fourth switch of each line selection switch group are disconnected, the second switch, the third switch and the fifth switch are closed, each bypass switch and the metal return line switch are disconnected, and each earth return line switch is closed; the first converter valve group, the second converter valve group, the third converter valve group and the fourth converter valve group in the sending-end converter station are connected in series, and the first converter valve group, the second converter valve group, the third converter valve group and the fourth converter valve group in the receiving-end converter station are connected in series.

[0009] In some embodiments of the present application, the first converter valve group is connected in parallel with the first bypass switch, the second converter valve group is connected in parallel with the second bypass switch, the third converter valve group is connected in parallel with the third bypass switch, and the fourth converter valve group is connected in parallel with the fourth bypass switch;

[0010] When the flexible direct current transmission system is in the ice-melting mode, the second switch, the third switch and the fifth switch of each line selection switch group are opened, the first switch and the fourth switch are closed, the first converter valve group and the second converter valve group in the sending-end converter station are connected in parallel, and the first converter valve group and the second converter valve group in the receiving-end converter station are connected in parallel; the third bypass switch is closed, and each metallic return line switch is closed, the first converter valve group and the fourth converter valve group in the sending-end converter station are connected in parallel, and the first converter valve group and the fourth converter valve group in the receiving-end converter station are connected in parallel.

[0011] In some embodiments of the present application, when the HVDC flexible power transmission system enters the ice melting mode, the converter valve group of the HVDC flexible power transmission system is closed;

[0012] And, after the parallel loop formed by the first converter valve group, the second converter valve group, and the fourth converter valve group is connected to the DC line, the converter valve group of the flexible DC transmission system is opened.

[0013] In some embodiments of the present application, the second DC current when the DC line is connected to the parallel circuit formed by the first converter valve group, the second converter valve group and the fourth converter valve group is greater than the first DC current when the DC line forms a series circuit with each converter valve group.

[0014] In another aspect, an embodiment of the present application provides a line deicing method, which is applied to any one of the flexible direct current transmission systems described above, and the method includes:

[0015] When the flexible direct current transmission system is in a normal operating mode, by controlling the line selection switch group, the bypass switch, the metallic return switch, and the earth return switch in the flexible direct current transmission system, each converter valve group in the flexible direct current transmission system forms a series circuit with the direct current line, thereby obtaining a first direct current of the direct current line;

[0016] When the flexible direct current transmission system is in an ice melting mode, a line selection switch group, a bypass switch, a metallic return switch, and an earth return switch in the flexible direct current transmission system are controlled so that a first converter valve group, a second converter valve group, and a fourth converter valve group in the flexible direct current transmission system form a parallel circuit, and the parallel circuit is connected to the direct current line, thereby obtaining a second direct current of the direct current line;

[0017] The second direct current is greater than the first direct current.

[0018] In another aspect, an embodiment of the present application provides a line de-icing device, applied to any one of the flexible direct current transmission systems described above, the device comprising:

[0019] a first line control module, configured to, when the flexible DC power transmission system is in a normal operating mode, control a line selection switch group, a bypass switch, a metallic return switch, and an earth return switch in the flexible DC power transmission system so that each converter valve group in the flexible DC power transmission system forms a series circuit with the DC line, thereby obtaining a first DC current of the DC line;

[0020] a second line control module, configured to, when the flexible direct current transmission system is in an ice-melting mode, control a line selection switch group, a bypass switch, a metallic return switch, and an earth return switch in the flexible direct current transmission system so that the first converter valve group, the second converter valve group, and the fourth converter valve group in the flexible direct current transmission system form a parallel circuit, and the parallel circuit is connected to the direct current line, thereby obtaining a second direct current of the direct current line; wherein the second direct current is greater than the first direct current.

[0021] On the other hand, an embodiment of the present application further provides an electronic device, comprising: a processor, a memory, and a computer program stored in the memory and capable of running on the processor, wherein the computer program implements the line de-icing method when executed by the processor.

[0022] On the other hand, an embodiment of the present application further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the line de-icing method is implemented.

[0023] In yet another aspect, an embodiment of the present application further provides a computer program product comprising instructions, which, when executed on a computer, enables the computer to execute the line de-icing method described in the above aspects.

[0024] The embodiments of the present application provide a flexible direct current (DC) transmission system, a line de-icing method, and related products. The flexible DC transmission system includes a sending-end converter station and a receiving-end converter station. A DC line is connected between the sending-end converter station and the receiving-end converter station. The sending-end converter station and the receiving-end converter station respectively include a bus positive pole and a bus negative pole. The bus positive pole in each converter station has a first converter valve group and a second converter valve group, and the bus negative pole in each converter station has a third converter valve group and a fourth converter valve group. Each converter valve group is connected in parallel with a bypass switch. A metal return line switch is connected between the pole line and the neutral line of the same pole, and an earth return line switch is connected between the neutral line and the grounded pole line. A line selection switch group is located between the first converter valve group and the second converter valve group. Specifically, when the flexible direct current transmission system is in a normal operating mode, the line selection switch group, the bypass switch, the metal return switch, and the earth return switch are controlled so that each converter valve group forms a series loop with the direct current line; when the flexible direct current transmission system is in an ice-melting mode, the line selection switch group, the bypass switch, the metal return switch, and the earth return switch are controlled so that the first converter valve group, the second converter valve group, and the fourth converter valve group form a parallel loop, which is connected to the direct current line. By adding line selection switches, multiple valve groups are connected in parallel, and the current on the direct current side is increased, thereby realizing power transmission and ice-melting of the direct current transmission line at the same time, thereby achieving the purpose of ice-melting of the line based on the flexible direct current transmission system itself without the need for power outage. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a wiring diagram of a single-valve group DC power transmission system provided in an embodiment of the present application;

[0026] Figure 2 This is a wiring diagram of a dual-valve group DC power transmission system provided in an embodiment of the present application;

[0027] Figure 3This is a wiring diagram of a dual-valve group DC power transmission system provided in an embodiment of the present application after a line selection switch is added;

[0028] Figure 4 This is a flowchart of the steps of a line de-icing method based on a flexible direct current transmission system according to an embodiment of the present application;

[0029] Figure 5 This is a basic control block diagram of the flexible DC transmission system provided in an embodiment of the present application;

[0030] Figure 6 This is a structural block diagram of a line de-icing device based on a flexible direct current transmission system according to an embodiment of the present application;

[0031] Figure 7 This is a structural block diagram of an electronic device provided in an embodiment of the present application;

[0032] Figure 8 This is a structural block diagram of a computer-readable storage medium provided in an embodiment of the present application. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0034] In the embodiment of the present application, by adding a line selection switch and connecting multiple valve groups in parallel, line de-icing can be achieved based on the flexible direct current transmission system itself without the need for power outage, which has the advantages of small footprint and low development cost.

[0035] The flexible DC transmission system may include a sending-end converter station and a receiving-end converter station. The de-icing object in the embodiment of the present application may be a DC line. Specifically, the DC line may be connected between the sending-end converter station and the receiving-end converter station to de-ice the DC line based on the flexible DC transmission system.

[0036] Optionally, each converter station generally includes a busbar positive pole and a busbar negative pole, and each pole may have at least one converter valve group. Figure 1 In the single-valve-group DC transmission system shown in the figure, each pole may have a converter valve group, specifically, there is a converter valve at the positive pole of the bus in the sending-end converter station or the receiving-end converter station, such as converter valve group 1, and there is a converter valve group at the negative pole of the bus in the sending-end converter station or the receiving-end converter station, such as converter valve group 2. As another example, if it is UHV DC, in the case of Figure 2In the dual-valve-group DC transmission system shown, each pole can have two converter valve groups. Specifically, a first converter valve group (i.e., converter valve group 1) and a second converter valve group (i.e., converter valve group 2) are present at the positive pole of the busbar in the sending-end converter station or the receiving-end converter station, and a third converter valve group (i.e., converter valve group 3) and a fourth converter valve group (i.e., converter valve group 4) are present at the negative pole of the busbar in the sending-end converter station or the receiving-end converter station. That is, the first converter valve group and the second converter valve group are in the same pole, and the third converter valve group and the fourth converter valve group are in the same pole.

[0037] Optional, whether Figure 1 The single valve group DC transmission system shown is also as Figure 2 The dual-valve group DC transmission system shown can be connected to a grounded pole line within each converter station to form a DC loop. Furthermore, within each converter station, a metallic return line switch, such as metallic return line switches 1 and 2, is connected between the pole line and the neutral line of the same pole, and an earth return line switch is connected between the neutral line and the grounded pole line.

[0038] Optional, in UHVDC, e.g. Figure 2 As shown, each valve group can also be connected in parallel with a bypass switch, for example, the first converter valve group (i.e., converter valve group 1) is connected in parallel with the first bypass switch (i.e., bypass switch 1), the second converter valve group (i.e., converter valve group 2) is connected in parallel with the second bypass switch (i.e., bypass switch 2), the third converter valve group (i.e., converter valve group 3) is connected in parallel with the third bypass switch (i.e., bypass switch 3), and the fourth converter valve group (i.e., converter valve group 4) is connected in parallel with the fourth bypass switch (i.e., bypass switch 4).

[0039] It should be noted that if the flexible DC transmission system is a multi-terminal DC system, the multi-terminal DC system may have multiple converter stations, which is not limited in the embodiment of the present application.

[0040] In practical applications, when the flexible DC transmission system is in operation, it can generate DC current by adjusting the DC voltage difference between the sending-end converter station and the receiving-end converter station, and then pass DC current into the DC line to achieve power transmission.

[0041] When the flexible DC transmission system is in normal operation mode, assuming the DC voltage is U dcN , the DC current is I dcN , the AC current is I acN , then according to the operating principle of flexible DC, the current flowing through the converter valve satisfies the following formula:

[0042]

[0043] Where, I vN In order to ensure the maximum value of the safe operation of the converter valve, the DC current generated by the flexible DC transmission system cannot exceed the above current.

[0044] In the embodiment of the present application, Figure 2 The wiring of the dual-valve group DC transmission system shown in the figure is modified through hardware circuits. Specifically, a line selection switch can be added to achieve parallel connection of multiple valve groups through circuit hardware control of the added line selection switch, thereby increasing the current on the DC side. This allows the flexible DC transmission system to achieve ice melting on the DC transmission line while achieving power transmission.

[0045] Specifically, refer to Figure 3 , shows a wiring diagram of the dual-valve group DC transmission system provided in an embodiment of the present application after a line selection switch is added.

[0046] Optionally, you can Figure 2 Based on the flexible DC transmission system wiring shown in the figure, in the sending-end converter station and the receiving-end converter station, a line selection switch group is added between the two valve groups located at one of the poles to realize the transformation of the converter valve group wiring. In the embodiment of the present application, taking the first converter valve group and the second converter valve group at the positive pole of the busbar as an example, for example, Figure 3 As shown, a line selection switch group is added between the first converter valve group (i.e., converter valve group 1) and the second converter valve group (i.e., converter valve group 2) in the sending-end converter station and the receiving-end converter station, while the original connection between the third converter valve group (i.e., converter valve group 3) and the fourth converter valve group (i.e., converter valve group 4) at the negative pole of the busbar is maintained.

[0047] In an embodiment of the present application, when the flexible direct current transmission system is in a normal operating mode, the line selection switch group, the bypass switch, the metal return switch, and the earth return switch can be controlled so that each converter valve group forms a series circuit with the DC line; when the flexible direct current transmission system is in an ice melting mode, the line selection switch group, the bypass switch, the metal return switch, and the earth return switch can be controlled so that the first converter valve group, the second converter valve group, and the fourth converter valve group form a parallel circuit, and are connected to the DC line via the parallel circuit formed by the first converter valve group, the second converter valve group, and the fourth converter valve group.

[0048] It should be noted that the second DC current when the DC line is connected to the parallel circuit formed by the first converter valve group, the second converter valve group, and the fourth converter valve group is greater than the first DC current when the DC line forms a series circuit with each converter valve group. That is, the DC current generated when the flexible DC transmission system is in the de-icing mode is greater than the DC current generated when the flexible DC transmission system is in the normal operating mode. Figure 3 The circuit wiring structure shown can increase the line current of the DC line to reduce the probability of line icing while ensuring normal power transmission.

[0049] Specifically, refer to Figure 4, shows a flowchart of the steps of a line deicing method provided in an embodiment of the present application, which may specifically include the following steps:

[0050] Step S401: When the flexible DC transmission system is in a normal operating mode, the line selection switch group, the bypass switch, the metallic return switch, and the earth return switch in the flexible DC transmission system are controlled so that each converter valve group in the flexible DC transmission system forms a series circuit with the DC line, thereby obtaining a first DC current of the DC line.

[0051] Each line selection switch group may include a first switch, a second switch, a third switch, a fourth switch, and a fifth switch, wherein the first switch, the second switch, the third switch, the fourth switch, and the fifth switch are connected in parallel.

[0052] Specifically, when the flexible direct current transmission system is in normal operating mode, the first switch and the fourth switch of each line selection switch group are disconnected, the second switch, the third switch and the fifth switch are closed, each bypass switch and the metal return line switch are disconnected, and each earth return line switch is closed, so that the first converter valve group, the second converter valve group, the third converter valve group and the fourth converter valve group in the sending-end converter station are connected in series, and the first converter valve group, the second converter valve group, the third converter valve group and the fourth converter valve group in the receiving-end converter station are connected in series.

[0053] Step S402: When the HVDC Flexible system is in the ice-melting mode, the line selection switch group, the bypass switch, the metallic return switch, and the earth return switch in the HVDC Flexible system are controlled so that the first converter valve group, the second converter valve group, and the fourth converter valve group in the HVDC Flexible system form a parallel loop, and the parallel loop is connected to the DC line to obtain a second DC current of the DC line.

[0054] Specifically, when the flexible direct current transmission system is in the ice-melting mode, the second switch, the third switch and the fifth switch of each line selection switch group are disconnected, and the first switch and the fourth switch are closed, so that the first converter valve group and the second converter valve group in the sending-end converter station are connected in parallel, and the first converter valve group and the second converter valve group in the receiving-end converter station are connected in parallel; the third bypass switch is closed, and each metal return line switch is closed, so that the first converter valve group and the fourth converter valve group in the sending-end converter station are connected in parallel, and the first converter valve group and the fourth converter valve group in the receiving-end converter station are connected in parallel, thereby realizing the parallel connection of the first converter valve group, the second converter valve group and the fourth converter valve group in the sending-end converter station and the receiving-end converter station.

[0055] In some embodiments of the present application, when the flexible direct current transmission system enters the ice melting mode, the converter valve group of the flexible direct current transmission system is closed; and after the parallel loop formed by the first converter valve group, the second converter valve group and the fourth converter valve group is connected to the DC line, the converter valve group of the flexible direct current transmission system is opened.

[0056] It should be noted that the execution order of the above-mentioned step S401 and step S402 is a parallel order, and the embodiment of the present application does not limit this.

[0057] For example, when the flexible DC transmission system is in normal operation mode, that is, bipolar operation, the following can be closed: Figure 3 The switches 2, 3, and 5 in each line selection switch group shown are disconnected. Figure 3 The switches 1 and 4 in each line selection switch group shown in FIG. Figure 3 As shown, each bypass switch and each metal return switch are disconnected, and each earth return switch is closed, so that each converter valve group and the DC line form a series loop, realizing the circuit connection in the normal operating mode.

[0058] As another example, when the flexible DC transmission system is in ice melting mode, the following steps can be followed to Figure 3 The circuit hardware control of the flexible DC transmission system shown in FIG. 1 may specifically include the following steps:

[0059] S1: The flexible DC transmission system is locked; wherein, locking means that the converter valve group is closed. In this state, the converter valve group is not conducting, and there is no current and voltage flowing through the converter valve group.

[0060] S2: Close switches 1 and 4 of the line selection switch group in the sending-end converter station, and open switches 2, 3, and 5 of the line selection switch group in the sending-end converter station, so that converter valve group 1 and converter valve group 2 in the sending-end converter station are connected in parallel.

[0061] S3: Close switches 1 and 4 of the line selection switch group in the receiving-end converter station, and open switches 2, 3, and 5 of the line selection switch group in the receiving-end converter station, so that converter valve group 1 and converter valve group 2 in the receiving-end converter station are connected in parallel.

[0062] S4: Close the bypass switch 3 of the sending-end converter station, and close the metal return line switches 1 and 2, so that the converter valve group 1 and the converter valve group 4 in the sending-end converter station are connected in parallel.

[0063] S5: Close the bypass switch 3 of the receiving-end converter station, and close the metallic return line switches 1 and 2, so that the converter valve group 1 and the converter valve group 4 in the receiving-end converter station are connected in parallel.

[0064] S6: The flexible HVDC transmission system is unlocked; unlocking means that the converter valve group is opened. In this state, the converter valve group is conductive and current and voltage flow through the converter valve group.

[0065] In such Figure 3Based on the modified flexible DC transmission system shown, after following the above steps, a line selection switch is added to achieve parallel connection of the first converter valve group and the second converter valve group. Simultaneously, utilizing the existing configuration within the converter station, a switch sequence is used to achieve parallel connection of the fourth converter valve group with the first and second converter valve groups. The parallel circuit formed by the first, second, and third converter valve groups can be connected to the DC line, thereby achieving a DC line current of three times the original rated current, thereby increasing the DC side current. This not only reduces the probability of line icing while ensuring normal power transmission, but also allows the DC line to maintain a relatively high DC current when icing is severe, thereby melting severely iced DC lines.

[0066] It should be noted that, since the flexible DC cannot achieve the reversal of the rated voltage, the third valve group cannot be connected in parallel. The ice melting method provided in the embodiment of the present application has already exerted the most reversible valve group without controlled changes.

[0067] Optionally, PI (Proportional-Integral Control, a control algorithm based on proportional P and integral I) control can be used. Figure 3 The flexible DC transmission system shown is controlled by software logic.

[0068] Specifically, refer to Figure 5 , shows the basic control block diagram of the flexible DC transmission system provided by the embodiment of the present application. After the flexible DC transmission system is unlocked, the converter valve group can be operated as follows Figure 5 The operation mode shown is as follows: the actual value is collected and compared with the set value, and then adjusted by the proportional integral controller (i.e., PI controller). Then, the modulation signal is obtained after the coordinate transformation, and the modulation signal is input to the valve control module of the converter valve to realize the control of the converter valve.

[0069] For example, the active power reference value P ref and active power measurement value P m Input to the PI controller, and output the DC current reference value I dcref , then the DC current reference value I dcref and the DC current measurement value I dcm Input to the PI controller and output the direct axis voltage reference value U dref ; The reactive power reference value Q ref and reactive power measurement Q m Input to the PI controller, and output the quadrature axis current reference value I qref , then the quadrature axis current reference value I qref and the quadrature axis current measurement value I qmInput to PI controller, output is quadrature axis voltage reference value U qref Then, the direct axis voltage reference value U can be obtained by the output dref and the quadrature axis voltage reference value U qref Perform the inverse Parker transform, i.e., dq→abc transform, where the direct axis refers to the d axis and the quadrature axis refers to the q axis. At this time, the signal in the rotating coordinate system (dq axis) can be converted back to the three-phase stationary coordinate system (abc) to obtain the three-phase reference wave U aref 、U bref 、U cref The three-phase reference wave obtained by the transformation can be used to generate a modulation signal, which can be input into the converter valve control module to control the converter valve. At this time, the DC current flowing through each valve group is still I dcN , the AC side current is I acN , but when the DC transmission system is running, the DC voltage of the DC line is 0.5U dcN , the DC current is 2I dcN , and then in the ice melting mode, the transmission system can provide a higher DC current to the DC line. At this time, the DC current flowing through each valve group is still I dcN , the AC side current is I acN , but when the DC transmission system is running, the DC voltage of the DC line is 0.5U dN , the DC current is 3I dN .

[0070] It should be noted that, in Figure 3 When controlling the wiring structure shown in the figure, the Figure 5 The logic algorithm shown in the figure increases the DC current of the de-icing line by three times, achieving a DC line current three times the original rated current. This effectively increases the current on the DC side. This not only reduces the probability of line icing while ensuring normal power transmission, but also allows the DC line to maintain a high DC current when ice is severely accumulated, thus melting severely iced DC lines.

[0071] In an embodiment of the present application, when the flexible DC transmission system is in a normal operating mode, the line selection switch group, the bypass switch, the metallic return switch, and the earth return switch are controlled, and each converter valve group forms a series loop with the DC line; when the flexible DC transmission system is in an ice-melting mode, the line selection switch group, the bypass switch, the metallic return switch, and the earth return switch are controlled, and the first converter valve group, the second converter valve group, and the fourth converter valve group form a parallel loop, which is connected to the DC line. By adding a line selection switch, multiple valve groups are connected in parallel, thereby achieving power transmission and ice melting of the DC transmission line at the same time, thereby achieving the purpose of line ice melting based on the flexible DC transmission system itself without the need for power outage.

[0072] It should be noted that for the method embodiments, for the sake of simplicity, they are all expressed as a series of action combinations, but those skilled in the art should be aware that the embodiments of the present application are not limited by the order of the actions described, because according to the embodiments of the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions involved are not necessarily required by the embodiments of the present application.

[0073] Reference Figure 6 , shows a structural block diagram of a line ice melting device provided by an embodiment of the present application, which is applied to Figure 3 The flexible DC transmission system shown in the figure may specifically include the following modules:

[0074] The first line control module 601 is configured to control the line selection switch group, bypass switch, metallic return switch, and earth return switch in the flexible DC transmission system when the flexible DC transmission system is in a normal operating mode, so that each converter valve group in the flexible DC transmission system forms a series circuit with the DC line, thereby obtaining a first DC current of the DC line;

[0075] The second line control module 602 is configured to, when the HVDC Flexible system is in the ice-melting mode, control the line selection switch group, the bypass switch, the metallic return switch, and the earth return switch in the HVDC Flexible system so that the first converter valve group, the second converter valve group, and the fourth converter valve group in the HVDC Flexible system form a parallel circuit, and the parallel circuit is connected to the DC line to obtain a second DC current in the DC line; wherein the second DC current is greater than the first DC current.

[0076] In some embodiments of the present application, the first line control module 601 may include the following submodules:

[0077] The first line control submodule is used to control, when the flexible direct current transmission system is in normal operating mode, the first switch and the fourth switch of each line selection switch group to be disconnected, the second switch, the third switch and the fifth switch to be closed, the bypass switches and the metallic return switches to be disconnected, and the earth return switches to be closed, so that the first converter valve group, the second converter valve group, the third converter valve group and the fourth converter valve group in the sending-end converter station are connected in series, and the first converter valve group, the second converter valve group, the third converter valve group and the fourth converter valve group in the receiving-end converter station are connected in series.

[0078] In some embodiments of the present application, the second line control module 602 may include the following submodules:

[0079] The second line control submodule is used to, when the flexible direct current transmission system is in the de-icing mode, control the second switch, the third switch and the fifth switch of each line selection switch group to be disconnected and the first switch and the fourth switch to be closed, so that the first converter valve group and the second converter valve group in the sending-end converter station are connected in parallel, and the first converter valve group and the second converter valve group in the receiving-end converter station are connected in parallel; and control the third bypass switch to be closed and each metallic return line switch to be closed, so that the first converter valve group and the fourth converter valve group in the sending-end converter station are connected in parallel, and the first converter valve group and the fourth converter valve group in the receiving-end converter station are connected in parallel.

[0080] In an embodiment of the present application, when the flexible DC transmission system is in a normal operating mode, the line selection switch group, the bypass switch, the metallic return switch, and the earth return switch are controlled, and each converter valve group forms a series loop with the DC line; when the flexible DC transmission system is in an ice-melting mode, the line selection switch group, the bypass switch, the metallic return switch, and the earth return switch are controlled, and the first converter valve group, the second converter valve group, and the fourth converter valve group form a parallel loop, which is connected to the DC line. By adding a line selection switch, multiple valve groups are connected in parallel, thereby achieving power transmission and ice melting of the DC transmission line at the same time, thereby achieving the purpose of line ice melting based on the flexible DC transmission system itself without the need for power outage.

[0081] As for the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0082] The present application also provides an electronic device, Figure 7 The provided electronic device 700 includes a memory 710, a processor 720, and a computer program 711 stored in the memory 710 and capable of running on the processor 720. When the computer program 711 is executed by the processor, the various processes of the above-mentioned embodiment of the line de-icing method based on the flexible direct current transmission system are implemented, and the same technical effects can be achieved. To avoid repetition, they are not described here.

[0083] The present application also provides a computer-readable storage medium. Figure 8 The computer-readable storage medium 800 provided stores a computer program 711. When the computer program 711 is executed by the processor, each process of the above-mentioned embodiment of the line de-icing method based on the flexible direct current transmission system is implemented, and the same technical effect can be achieved. To avoid repetition, it will not be described here.

[0084] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0085] It should be noted that the terms "first", "second", etc. in the description and claims of the embodiments of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate so that the embodiments described herein can be implemented in an order other than that shown or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or modules is not necessarily limited to those steps or modules clearly listed, but may include other steps or modules that are not clearly listed or inherent to these processes, methods, products or devices. The division of modules that appears in the embodiments of the present application is only a logical division. In actual applications, there may be other division methods. For example, multiple modules can be combined into or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between each other shown or discussed can be through some interfaces, and the indirect coupling or communication connection between modules can be electrical or other similar forms, which are not limited in the embodiments of the present application. Moreover, the modules or sub-modules described as separate components may or may not be physically separated, may or may not be physical modules, or may be distributed into multiple circuit modules, and some or all of the modules may be selected according to actual needs to achieve the purpose of the embodiment of the present application.

[0086] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0087] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and modules described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0088] In the several embodiments provided in the embodiments of the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the modules is only a logical function division. There may be other division methods in actual implementation, such as multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or modules, which can be electrical, mechanical or other forms.

[0089] The modules described as separate components may or may not be physically separate, and the components shown as modules may or may not be physical modules, that is, they may be located in one place or distributed across multiple network modules. Some or all of the modules may be selected to achieve the purpose of the present embodiment according to actual needs.

[0090] In addition, the functional modules in each embodiment of the present application can be integrated into a processing module, or each module can exist physically separately, or two or more modules can be integrated into a module. The above-mentioned integrated modules can be implemented in the form of hardware or in the form of software functional modules. If the integrated modules are implemented in the form of software functional modules and sold or used as independent products, they can be stored in a computer-readable storage medium.

[0091] In the above embodiments, all or part of the embodiments may be implemented by software, hardware, firmware, or any combination thereof. When implemented by software, all or part of the embodiments may be implemented in the form of a computer program product.

[0092] The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the processes or functions described in accordance with the embodiments of the present application are generated in whole or in part. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions may be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via a wired (e.g., coaxial cable, optical fiber, Digital Subscriber Line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) method. The computer-readable storage medium may be any available medium that can be stored on a computer or a data storage device such as a server or data center that integrates one or more available media. The available medium may be a magnetic medium (e.g., a floppy disk, hard disk, or magnetic tape), an optical medium (e.g., a DVD), or a semiconductor medium (e.g., a solid-state drive (SSD)).

[0093] The embodiments of the present application are described with reference to the flowcharts and / or block diagrams of the methods, terminal devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing terminal device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing terminal device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0094] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing terminal device to operate in a specific manner, so that the instructions stored in the computer readable memory produce a manufactured product including an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 These computer program instructions can also be loaded into a computer or other programmable data processing terminal device, so that a series of operation steps are executed on the computer or other programmable terminal device to produce a computer-implemented process, thereby providing instructions for implementing the process in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 The steps for the function specified in one or more boxes.

[0095] Although preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they become aware of the basic inventive concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0096] Finally, 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, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with the relevant laws, regulations and standards of relevant countries and regions, and provide corresponding operation entrances for users to choose to authorize or refuse.

[0097] The above is a detailed introduction to the technical solutions provided in the embodiments of the present application. Specific examples are used in the embodiments of the present application to illustrate the principles and implementation methods of the embodiments of the present application. The description of the above embodiments is only used to help understand the methods and core ideas of the embodiments of the present application. At the same time, for those skilled in the art, according to the ideas of the embodiments of the present application, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the embodiments of the present application.

Claims

1. A flexible direct current transmission system, characterized in that: The system includes a sending-end converter station and a receiving-end converter station, a DC line is connected between the sending-end converter station and the receiving-end converter station, the sending-end converter station and the receiving-end converter station respectively include a bus positive pole and a bus negative pole, the bus positive pole in each converter station has a first converter valve group and a second converter valve group, the bus negative pole in each converter station has a third converter valve group and a fourth converter valve group, each converter valve group is connected in parallel with a bypass switch, a metal return line switch is connected between the pole line and the neutral line of the same pole, an earth return line switch is connected between the neutral line and the grounding pole line, wherein a line selection switch group is located between the first converter valve group and the second converter valve group; When the flexible direct current transmission system is in a normal operating mode, the line selection switch group, the bypass switch, the metal return line switch, and the earth return line switch are controlled so that each converter valve group forms a series circuit with the direct current line; when the flexible direct current transmission system is in an ice-melting mode, the line selection switch group, the bypass switch, the metal return line switch, and the earth return line switch are controlled so that the first converter valve group, the second converter valve group, and the fourth converter valve group form a parallel circuit, and the parallel circuit is connected to the direct current line.

2. The system according to claim 1, wherein: Each line selection switch group includes a first switch, a second switch, a third switch, a fourth switch and a fifth switch, and the first switch, the second switch, the third switch, the fourth switch and the fifth switch are connected in parallel.

3. The system according to claim 2, characterized in that When the flexible direct current transmission system is in normal operating mode, the first switch and the fourth switch of each line selection switch group are disconnected, the second switch, the third switch and the fifth switch are closed, each bypass switch and the metal return line switch are disconnected, and each earth return line switch is closed; the first converter valve group, the second converter valve group, the third converter valve group and the fourth converter valve group in the sending-end converter station are connected in series, and the first converter valve group, the second converter valve group, the third converter valve group and the fourth converter valve group in the receiving-end converter station are connected in series.

4. The system according to claim 2, wherein: The first converter valve group is connected in parallel with the first bypass switch, the second converter valve group is connected in parallel with the second bypass switch, the third converter valve group is connected in parallel with the third bypass switch, and the fourth converter valve group is connected in parallel with the fourth bypass switch; When the flexible HVDC transmission system is in ice-melting mode, the second switch, the third switch, and the fifth switch of each line selection switch group are opened, the first switch and the fourth switch are closed, the first converter valve group and the second converter valve group in the sending-end converter station are connected in parallel, and the first converter valve group and the second converter valve group in the receiving-end converter station are connected in parallel; The third bypass switch is closed, each metal return line switch is closed, the first converter valve group and the fourth converter valve group in the sending-end converter station are connected in parallel, and the first converter valve group and the fourth converter valve group in the receiving-end converter station are connected in parallel.

5. The system according to claim 4, characterized in that When the flexible direct current transmission system enters the ice melting mode, the converter valve group of the flexible direct current transmission system is closed; And, after the parallel loop formed by the first converter valve group, the second converter valve group, and the fourth converter valve group is connected to the DC line, the converter valve group of the flexible DC transmission system is opened.

6. The system according to claim 1, wherein: The second DC current when the DC line is connected to the parallel circuit formed by the first converter valve group, the second converter valve group and the fourth converter valve group is greater than the first DC current when the DC line forms a series circuit with each converter valve group.

7. A line deicing method, characterized in that: Applied to the flexible direct current transmission system according to any one of claims 1 to 6, the method comprises: When the flexible direct current transmission system is in a normal operating mode, by controlling the line selection switch group, the bypass switch, the metallic return switch, and the earth return switch in the flexible direct current transmission system, each converter valve group in the flexible direct current transmission system forms a series circuit with the direct current line, thereby obtaining a first direct current of the direct current line; When the flexible direct current transmission system is in an ice melting mode, a line selection switch group, a bypass switch, a metallic return switch, and an earth return switch in the flexible direct current transmission system are controlled so that a first converter valve group, a second converter valve group, and a fourth converter valve group in the flexible direct current transmission system form a parallel circuit, and the parallel circuit is connected to the direct current line, thereby obtaining a second direct current of the direct current line; The second direct current is greater than the first direct current.

8. A line ice melting device, characterized in that: Applied to the flexible direct current transmission system according to any one of claims 1 to 6, the device comprises: a first line control module, configured to, when the flexible DC power transmission system is in a normal operating mode, control a line selection switch group, a bypass switch, a metallic return switch, and an earth return switch in the flexible DC power transmission system so that each converter valve group in the flexible DC power transmission system forms a series circuit with the DC line, thereby obtaining a first DC current of the DC line; a second line control module, configured to, when the flexible direct current transmission system is in an ice-melting mode, control a line selection switch group, a bypass switch, a metallic return switch, and an earth return switch in the flexible direct current transmission system so that the first converter valve group, the second converter valve group, and the fourth converter valve group in the flexible direct current transmission system form a parallel circuit, and the parallel circuit is connected to the direct current line, thereby obtaining a second direct current of the direct current line; wherein the second direct current is greater than the first direct current.

9. An electronic device, characterized in that: include: A processor, a memory, and a computer program stored in the memory and capable of running on the processor, wherein when the computer program is executed by the processor, the line deicing method according to claim 7 is implemented.

10. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the line de-icing method according to claim 7 is implemented.

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