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 wire switch, a bypass switch, a metal loop switch and a ground loop switch are controlled, and the wire switch, the bypass switch, the metal loop switch and the ground loop switch are switched on and switched off. Each converter valve group and the direct current line form a series loop; when the flexible direct-current power transmission system is in an ice melting mode, the wire switch, the bypass switch, the metal loop switch and the ground loop switch are controlled, so that a bus positive electrode and a bus negative electrode in the sending end converter station form a parallel loop, and the parallel loop is connected with the direct-current line. The switch is added, pole parallel connection is carried out on the valve group, the current of the direct current side is improved, and line ice melting is achieved on the basis of the flexible direct current power transmission system under the condition that power failure is not needed.

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 switches and related controls.

[0005] In one aspect, an embodiment of the present application provides a flexible direct current (DC) 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, and conductor switches are provided at both ends of the DC line. The sending-end converter station and the receiving-end converter station each comprise a busbar positive pole and a busbar negative pole, each comprising at least one converter valve group at the busbar positive pole and at least one converter valve group at the busbar negative pole, each converter valve group being connected in parallel with a bypass switch, a metal return line switch being connected between a pole line and a neutral line of the same pole, and an earth return line switch being connected between the neutral line and a grounding pole line;

[0006] When the flexible direct current transmission system is in a normal operating mode, the conductor switch, 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 conductor switch, the bypass switch, the metal return line switch, and the earth return line switch are controlled so that the bus positive electrode and the bus negative electrode in the sending-end converter station form a parallel circuit, and the parallel circuit is connected to the direct current line.

[0007] In some embodiments of the present application, when the flexible direct current transmission system is in normal operating mode, each bypass switch and metal return line switch is disconnected, each earth return line switch and the conductor switch are closed, each converter valve group in the sending-end converter station is connected in series, and each converter valve group in the receiving-end converter station is connected in series.

[0008] In some embodiments of the present application, the DC line connected between the sending-end converter station and the receiving-end converter station includes a first DC line and a second DC line, the conductor switches located at both ends of the first DC line include a first conductor switch and a second conductor switch, and the conductor switches located at both ends of the second DC line include a third conductor switch and a fourth conductor switch;

[0009] When the flexible direct current transmission system is in the ice-melting mode, the first conductor switch and the second conductor switch are closed, or the third conductor switch and the fourth conductor switch are closed; each metal return line switch is closed, each earth return line switch is closed, and the bus positive electrode and the bus negative electrode in the sending-end converter station form a parallel circuit.

[0010] In some embodiments of the present application, when there are two converter valve groups at the positive pole of the busbar and the negative pole of the busbar, respectively, the two converter valve groups at the positive pole of the busbar are connected in parallel with the first bypass switch and the second bypass switch, respectively, and the two converter valve groups at the negative pole of the busbar are connected in parallel with the third bypass switch and the fourth bypass switch, respectively.

[0011] When the flexible direct current power transmission system is in an ice-melting mode, the first bypass switch and the second bypass switch, or the third bypass switch and the fourth bypass switch are closed.

[0012] 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;

[0013] Furthermore, after the parallel loop formed by the bus positive electrode and the bus negative electrode in the sending-end converter station is connected to the DC line, the converter valve group of the flexible DC transmission system is opened.

[0014] In some embodiments of the present application, when there are two converter valve groups at the positive pole of the busbar and the negative pole of the busbar respectively, in one of the converter stations of the sending-end converter station or the receiving-end converter station, there is a line selection switch group between the two converter valve groups located at the same pole; wherein, in the sending-end converter station or the receiving-end converter station, there is a line selection switch group for the first converter valve group and the second converter valve group located at the positive pole of the busbar, and there is a line selection switch group for the third converter valve group and the fourth converter valve group located at the negative pole of the busbar.

[0015] 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.

[0016] 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 the 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, each earth return line switch and the conductor switch are 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.

[0017] In some embodiments of the present application, the DC line connected between the sending-end converter station and the receiving-end converter station includes a first DC line and a second DC line, the conductor switches at both ends of the first DC line include a first conductor switch and a second conductor switch, and the conductor switches at both ends of the second DC line include a third conductor switch and a fourth conductor switch;

[0018] The two converter valve groups located at the positive pole of the busbar are respectively connected in parallel with the first bypass switch and the second bypass switch, and the two converter valve groups located at the negative pole of the busbar are respectively connected in parallel with the third bypass switch and the fourth bypass switch;

[0019] When the flexible direct current transmission system is in the ice-melting mode, the first switch and the fourth switch of each line selection switch group are opened, and the second switch, the third switch, and the fifth switch are closed. The first converter valve group and the second converter valve group located at the positive pole of the busbar in the sending-end converter station are connected in parallel, and the third converter valve group and the fourth converter valve group located at the negative pole of the busbar in the sending-end converter station are connected in parallel. Each metal return line switch in the sending-end converter station is closed, and the positive pole of the busbar and the negative pole of the busbar in the sending-end converter station form a parallel circuit.

[0020] The first bypass switch and the second bypass switch in the receiving-end converter station, or the third bypass switch and the fourth bypass switch in the receiving-end converter station are closed; the first conductor switch and the second conductor switch, or the third conductor switch and the fourth conductor switch are closed, and each earth return line switch is closed.

[0021] 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, wherein the flexible direct current transmission system adopts a full-bridge structure or a half-bridge structure, and the method includes:

[0022] Controlling the lower transistor in the half-bridge structure to be turned on; after the lower transistor is turned on, the half-bridge structure is bypassed;

[0023] The full-bridge structure is controlled at the bus positive pole according to an external positive voltage, and the full-bridge structure is controlled at the bus negative pole according to an external negative voltage, so that the operating voltages of the bus positive pole and the bus negative pole are the same after the bus positive pole and the bus negative pole in the sending-end converter station form a parallel circuit.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] The flexible direct current transmission system, line de-icing method and related products provided in the embodiments of the present application include a sending-end converter station and a receiving-end converter station. A direct current line is connected between the sending-end converter station and the receiving-end converter station. There are conductor switches at both ends of the direct current line. The sending-end converter station and the receiving-end converter station respectively include a bus positive pole and a bus negative pole. There is at least one converter valve group at the bus positive pole and the bus negative pole respectively. 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 grounding pole line. Specifically, when the flexible direct current transmission system is in normal operation mode, the conductor switch, bypass switch, metal return switch and earth return switch are controlled so that each converter valve group forms a series loop with the DC line; when the flexible direct current transmission system is in de-icing mode, the conductor switch, bypass switch, metal return switch and earth return switch are controlled so that the bus positive pole and the bus negative pole in the sending-end converter station form a parallel loop, and the parallel loop is connected to the DC line. By adding switches, the valve groups are connected in parallel when the flexible direct current transmission system is in de-icing mode, thereby increasing the current on the DC side, realizing power transmission and de-icing of the DC transmission line at the same time, and achieving the purpose of de-icing the line based on the flexible direct current transmission system itself without the need for power outage. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a wiring diagram of a single-valve group DC power transmission system provided in an embodiment of the present application;

[0029] Figure 2 This is a wiring diagram of a dual-valve group DC power transmission system provided in an embodiment of the present application;

[0030] Figure 3 This is a wiring diagram of a single-valve group DC power transmission system provided in an embodiment of the present application after a conductor switch is added;

[0031] Figure 4 This is a wiring diagram of a dual-valve group DC power transmission system provided in an embodiment of the present application after a conductor switch is added;

[0032] Figure 5 This 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;

[0033] Figure 6 This is a flowchart of the steps of a line de-icing method provided in an embodiment of the present application;

[0034] Figure 7 This is a schematic diagram of a half-bridge structure provided by an embodiment of the present application;

[0035] Figure 8 This is a schematic diagram of the full-bridge structure provided by an embodiment of the present application;

[0036] Figure 9 This is a control block diagram of the flexible direct current transmission system provided by an embodiment of the present application;

[0037] Figure 10 This is a structural block diagram of an electronic device provided in an embodiment of the present application;

[0038] Figure 11 This is a structural block diagram of a computer-readable storage medium provided in an embodiment of the present application. DETAILED DESCRIPTION

[0039] 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.

[0040] In the embodiments of the present application, by adding switches and connecting the valve groups in parallel, the flexible DC transmission system itself can achieve line de-icing without the need for power outages, which has the advantages of small footprint and low development cost. On the one hand, for single-valve-group DC transmission systems and dual-valve-group DC transmission systems, by adding conductor switches at both ends of the DC line, the valve groups are connected in parallel, increasing the DC side current and achieving de-icing on the DC line. On the other hand, for dual-valve-group DC transmission systems, by adding line selection switches to both valve groups located at the same pole in one of the converter stations, the multiple valve groups are connected in parallel, further increasing the DC side current and achieving de-icing on the DC line. On the other hand, by controlling all half-bridge structures in the flexible DC transmission system to use the upper transistors to conduct, and controlling all full-bridge modules at the positive bus pole to control the external positive voltage, and controlling all full-bridge modules at the negative bus pole to control the external negative voltage, the flexible DC transmission system can ensure that the operating voltage of the two poles in parallel is the same during operation, meeting the operating conditions of the two poles in parallel.

[0041] Specifically, 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.

[0042] 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 1In 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 group 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 2 In 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.

[0043] 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.

[0044] 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).

[0045] 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.

[0046] 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.

[0047] 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:

[0048]

[0049] 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.

[0050] In the embodiment of the present application, switches can be added to achieve parallel connection of the poles of the valve group.

[0051] Optionally, conductor switches can be added at both ends of the DC line, the valve groups can be connected in parallel, and the current on the DC side can be increased, so that the flexible DC transmission system can achieve ice melting on the DC transmission line while transmitting power.

[0052] Among them, the wiring of the single valve group DC transmission system after adding the conductor switch can be as follows Figure 3 As shown, the wiring of the double valve group DC transmission system after adding the conductor switch can be as follows Figure 4 As shown. For example, Figure 3 and Figure 4 As shown, the DC line connected between the sending-end converter station and the receiving-end converter station may include a first DC line and a second DC line. The conductor switches located at both ends of the first DC line may include a first conductor switch and a second conductor switch, that is, the first conductor switch and the second conductor switch are respectively located at the beginning and the end of the first DC line, and the first conductor switch and the second conductor switch are connected in series with the first DC line. The conductor switches located at both ends of the second DC line may include a third conductor switch and a fourth conductor switch, that is, the third conductor switch and the fourth conductor switch are respectively located at the beginning and the end of the second DC line, and the third conductor switch and the fourth conductor switch are connected in series with the second DC line.

[0053] In an embodiment of the present application, when the HVDC Flexible system is in normal operating mode, the conductor switches, bypass switches, metallic return switches, and earth return switches can be controlled so that each converter valve group forms a series circuit with the DC line. Specifically, when the HVDC Flexible system is in normal operating mode, each bypass switch and metallic return switch is opened, and each earth return switch and conductor switch is closed, so that each converter valve group in the sending-end converter station is connected in series, and each converter valve group in the receiving-end converter station is connected in series.

[0054] When the HVDC Flexible system is in de-icing mode, the conductor switch, bypass switch, metal return switch, and earth return switch can be controlled so that the positive and negative busbars in the sending-end converter station form a parallel circuit, and are connected to the DC line via the parallel circuit formed by the positive and negative busbars in the sending-end converter station. Specifically, when the HVDC Flexible system is in de-icing mode, each metal return switch is closed, the first and second conductor switches, or the third and fourth conductor switches, are closed, and each earth return switch is closed, so that the positive and negative busbars in the sending-end converter station form a parallel circuit.

[0055] In some embodiments of the present application, for a dual-valve group DC transmission system, that is, when there are two converter valve groups at the positive pole of the bus and the negative pole of the bus respectively, the two converter valve groups located at the positive pole of the bus can be connected in parallel with the first bypass switch and the second bypass switch respectively, and the two converter valve groups located at the negative pole of the bus can be connected in parallel with the third bypass switch and the fourth bypass switch respectively. When the flexible DC transmission system is in the ice melting mode, in order to achieve bipolar parallel connection in the sending-end converter station, the first bypass switch and the second bypass switch, or the third bypass switch and the fourth bypass switch can be controlled to be closed.

[0056] 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 bus positive pole and the bus negative pole in the sending-end converter station is connected to the DC line, the converter valve group of the flexible direct current transmission system is opened.

[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 and Figure 4 The individual conductor switches shown, such as conductor switches 1, 2, 3, and 4, and as shown in FIG. Figure 3 and Figure 4 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, you can follow the steps below to Figure 3 and Figure 4 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 the metal return switches 1 and 2 of the sending-end converter station to connect the positive and negative busbars in the sending-end converter station in parallel.

[0061] S3: Close bypass switches 1 and 2, or bypass switches 3 and 4 at the receiving converter station.

[0062] S4: Close conductor switches 1 and 2, or conductor switches 3 and 4.

[0063] S5: Close the earth return line switches in the sending-end converter station and the receiving-end converter station.

[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 3 and Figure 4 Based on the modified flexible DC transmission system shown in the figure, after following the above steps, by adding a conductor switch, the positive and negative busbars in the sending-end converter station are connected in parallel. The parallel circuit formed can be connected to the DC line, thereby achieving a DC line current of twice the original rated current, that is, 2I dcN , achieving the effect of increasing the current on the DC side.

[0066] Optionally, for a dual-valve group DC transmission system, the valve group wiring can be further modified.

[0067] In some embodiments of the present application, Figure 4 Based on the flexible DC transmission system wiring shown, line selection switches are added to the two valve groups located at the same pole in one of the sending-end converter station or the receiving-end converter station to achieve valve group wiring transformation, so as to connect multiple valve groups in parallel and further increase the current on the DC side. This allows the flexible DC transmission system to achieve power transmission while also achieving de-icing of the DC transmission line.

[0068] Specifically, a line selection switch group can be added between the first converter valve group and the second converter valve group located at the positive pole of the bus in the sending-end converter station or the receiving-end converter station, and a line selection switch group can be added between the third converter valve group and the fourth converter valve group located at the negative pole of the bus.

[0069] Taking the sending-end converter station as an example, Figure 5As 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) at the positive pole of the busbar in the sending-end converter station, and a line selection switch group is added 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 in the sending-end converter station, while the original connections between the converter valve groups in the receiving-end converter station are maintained.

[0070] 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.

[0071] When the flexible DC transmission system is in normal operating mode, the first switch and the fourth switch of the line selection switch group are opened, the second switch, the third switch and the fifth switch are closed, each bypass switch and the metal return line switch are opened, and each earth return line switch and the conductor switch are 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, and each converter valve group forms a series loop with the DC line.

[0072] When the flexible DC transmission system is in de-icing mode, the first and fourth switches of each line selection switch group are opened, and the second, third, and fifth switches are closed, so that the first and second converter valve groups located at the positive pole of the busbar in the sending-end converter station are connected in parallel, and the third and fourth converter valve groups located at the negative pole of the busbar in the sending-end converter station are connected in parallel. Furthermore, each metal return line switch in the sending-end converter station is closed, so that the positive and negative poles of the busbar in the sending-end converter station form a parallel circuit. Furthermore, the first and second bypass switches, or the third and fourth bypass switches, in the receiving-end converter station are closed; each earth return line switch is closed; and the first and second conductor switches, or the third and fourth conductor switches, are closed, to achieve bipolar parallel connection.

[0073] For example, when the flexible DC transmission system is in normal operation mode, that is, bipolar operation, the following can be closed: Figure 5 The switches 2, 3, and 5 in each line selection switch group shown are disconnected. Figure 5 The switches 1 and 4 in each line selection switch group shown in FIG. Figure 5 As shown, each bypass switch and each metal return switch are disconnected, and each conductor switch and each earth return switch are closed, so that each converter valve group and the DC line form a series loop, realizing the circuit connection in the normal operating mode.

[0074] As another example, when the flexible DC transmission system is in ice melting mode, the following steps can be followed to Figure 5 The circuit hardware control of the flexible DC transmission system shown in FIG. 1 may specifically include the following steps:

[0075] 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.

[0076] S2: Close switches 1 and 4 of the line selection switch group located at pole 1 (i.e., the positive pole of the busbar) 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 the converter valve groups 1 and 2 located at pole 1 in the sending-end converter station are connected in parallel.

[0077] S3: Close switches 1 and 4 of the line selection switch group located at pole 2 (i.e., the negative pole of the busbar) 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 the converter valve groups 3 and 4 located at pole 2 in the sending-end converter station are connected in parallel.

[0078] S4: Close the metallic return switches 1 and 2 of the sending-end converter station, so that poles 1 and 2 in the sending-end converter station are connected in parallel.

[0079] S5: Close bypass switches 1 and 2, or bypass switches 3 and 4 at the receiving converter station.

[0080] S6: Close conductor switches 1 and 2, or conductor switches 3 and 4.

[0081] S7: Close the earth return line switches at the sending-end converter station and the receiving-end converter station.

[0082] S8: The flexible DC 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.

[0083] In such Figure 5 Based on the modified flexible DC transmission system shown in the figure, after following the above steps, by adding a line selection switch, the positive and negative busbars in the sending-end converter station are connected in parallel. The parallel circuit formed can be connected to the DC line, thereby achieving a DC line current of 4 times the original rated current, that is, 4I dcN , achieving the effect of increasing the current on the DC side.

[0084] Furthermore, the embodiments of the present application can achieve pole paralleling through the aforementioned switches. However, during operation, the bipolar parallel connection of the flexible DC transmission system requires that its operating voltages be the same. According to the existing control, the voltages of poles 1 and 2 are one positive and one negative, respectively, and these are the result of independent control. This state is not conducive to the coordinated operation of the flexible DC transmission system when bipolar parallel connection is in place. The embodiments of the present application can modify the control of the flexible DC transmission system to ensure the same voltage during bipolar parallel operation.

[0085] Specifically, refer to Figure 6 , 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:

[0086] Step S601, controlling the lower transistor in the half-bridge structure to be turned on; after the lower transistor is turned on, the half-bridge structure is bypassed;

[0087] In step S602, the full-bridge structure is controlled at the bus positive pole according to an external positive voltage, and the full-bridge structure is controlled at the bus negative pole according to an external negative voltage, so that the operating voltages of the bus positive pole and the bus negative pole are the same after the bus positive pole and the bus negative pole in the sending-end converter station form a parallel circuit.

[0088] In the embodiment of the present application, each converter valve group in the flexible DC transmission system adopts a full-bridge structure and a half-bridge structure. Specifically, each converter valve group in the flexible DC transmission system is composed of multiple full-bridge structures and multiple half-bridge structures connected in series.

[0089] Among them, such as Figure 7 As shown, a half-bridge structure can be composed of two power switches (T1 and T2) and related auxiliary components (such as diodes D1 and D2, and possibly capacitors). T1 can be called the upper transistor, and T2 can be called the lower transistor. The half-bridge structure has different characteristics depending on the combination of different switch transistors. The system characteristics of the half-bridge structure can be shown in Table 1 below:

[0090] Table 1 System characteristics of half-bridge structure

[0091]

[0092] As can be seen from Table 1 above, the half-bridge structure can only show +Ud characteristics and 0 voltage characteristics to the outside, and cannot show negative voltage characteristics.

[0093] like Figure 8As shown, a full-bridge structure can be formed by four power switches (T1, T2, T3, and T4) to form a bridge, and may also include auxiliary components such as freewheeling diodes (which can be integrated inside the switches). The full-bridge structure has different characteristics when different switch combinations are used. The system characteristics of the full-bridge structure can be shown in Table 2 below:

[0094] Table 2 System characteristics of half-bridge structure

[0095]

[0096] As can be seen from Table 2 above, the full-bridge structure can externally reflect the +Ud characteristic, 0 voltage characteristic, and -Ud characteristic.

[0097] It should be noted that there is at least one converter valve group at the positive pole of the bus and at the negative pole of the bus, and each converter valve group is composed of multiple full-bridge structures and multiple half-bridge structures connected in series. It can be understood that the full-bridge structure and the half-bridge structure are connected in series between the positive and negative busbars to form a converter valve group.

[0098] From the above, it can be seen that the current flexible DC usually adopts a full half-bridge structure, and the half-bridge structure can only output positive voltage. In order to ensure that the operating voltage is the same when the two poles are connected in parallel, the embodiment of the present application can control all half-bridge structures to use the lower transistor, that is, the T2 tube is turned on, and the entire half-bridge structure is forced to be bypassed to eliminate the interference of the output characteristics of the half-bridge structure itself (can only output positive voltage) on the overall voltage consistency control, so that the half-bridge structure no longer participates in the normal voltage output process, creating conditions for the subsequent control of the full-bridge module.

[0099] Full-bridge modules are capable of outputting both positive and negative voltages. To ensure that Pole 1 (the positive busbar) achieves the required positive voltage output in a bipolar parallel system, coordinating it with the voltage at Pole 2 (the negative busbar) to achieve overall voltage consistency, the full-bridge module can be configured to output a positive voltage in Pole 1 to meet system operating requirements and provide appropriate positive voltage support for bipolar parallel operation. Similarly, to ensure that a negative voltage output corresponds to the positive voltage at Pole 1, the full-bridge module can be configured to output a negative voltage at Pole 2. By coordinating the positive voltage at Pole 1 with the negative voltage at Pole 2, the bipolar voltages can be numerically aligned with system operating requirements, meeting the voltage requirements for flexible DC bipolar parallel operation.

[0100] Optionally, the modified flexible direct current transmission system in the embodiment of the present application may be subjected to software logic control, and the operation requirements may be met by the modified control strategy.

[0101] Specifically, refer to Figure 9 , shows a 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 Specifically, for a half-bridge structure, the voltage reference value can be given as a positive voltage reference value; for a full-bridge structure, pole 1 can be given as a positive voltage reference value, and before pole 2 enters the valve control module, the voltage reference of pole 2 can be multiplied by -1 to ensure that the operating voltage of the flexible DC transmission system is the same when two poles are connected in parallel.

[0102] like Figure 9 As shown in the figure, the modified control strategy is mainly reflected in achieving the same voltage during bipolar parallel operation by controlling the full-bridge module and combining the bypass operation of the half-bridge structure.

[0103] For example, in the half-bridge valve control, the half-bridge structure realizes bypass by turning on the T2 tube. Specifically, it can be expressed as setting the reference voltage U ref And phase angle information is input to the voltage conversion module, where U ref =0; the voltage conversion module can convert the voltage according to the requirements of the flexible DC transmission system and output the three-phase reference wave U aref 、U bref 、U cref The transformed three-phase reference wave can be used to generate a modulation signal, which can be input to the pole 1 half-bridge valve control module and the pole 2 half-bridge valve control module to realize the control of the half-bridge structure, that is, to make the half-bridge structure perform a bypass operation and no longer participate in the normal voltage conversion core process.

[0104] In full-bridge valve control, the reference current I ref and the measured current I m Input to PI (Proportional-Integral Control, a control algorithm based on proportional P and integral I) controller, the output is the reference voltage U ref , the reference voltage U ref The phase angle information is input to the voltage conversion module, which can convert the voltage according to the requirements of the flexible DC transmission system and output the three-phase reference wave U aref 、U bref 、U cref The transformed three-phase reference wave can be used to generate a modulation signal, which is then input to the full-bridge valve-controlled module of Pole 1 and the full-bridge valve-controlled module of Pole 2. After the transformation, the full-bridge valve-controlled module of Pole 1 controls the output of all full-bridge modules to a positive external voltage, while the full-bridge valve-controlled module of Pole 2 controls the output of all full-bridge modules to a negative external voltage. To achieve negative voltage output control, the signal of Pole 2 can be multiplied by -1 to achieve bipolar voltage consistency.

[0105] It should be noted that the same operating voltage mentioned in the embodiments of the present application does not mean that the voltage values and polarities of poles 1 and 2 are the same. The voltage consistency after the transformation may be reflected in the stability of the potential relationship. For example, in a bipolar system, with the earth or a reference point as the reference, pole 1 is at a positive potential relative to the reference point, and pole 2 is at a negative potential, which can form a stable potential difference, providing suitable voltage support for the flexible direct current transmission system, ensuring the normal flow of current and power transmission; it may also be reflected in voltage amplitude matching. For example, during power transmission, according to the system transmission power size, line parameters, etc., the positive voltage amplitude of pole 1 and the negative voltage amplitude of pole 2 can change synergistically to ensure that the voltage between the two poles meets operating conditions such as power transmission, thereby realizing stable operation of the flexible direct current transmission system.

[0106] In the embodiments of the present application, by adding switches and connecting the valve groups in parallel, the flexible DC transmission system itself can achieve line de-icing without the need for power outages, which has the advantages of small footprint and low development cost. On the one hand, for single-valve-group DC transmission systems and dual-valve-group DC transmission systems, by adding conductor switches at both ends of the DC line, the valve groups are connected in parallel, increasing the DC side current and achieving de-icing on the DC line. On the other hand, for dual-valve-group DC transmission systems, by adding line selection switches to both valve groups located at the same pole in one of the converter stations, the multiple valve groups are connected in parallel, further increasing the DC side current and achieving de-icing on the DC line. On the other hand, by controlling all half-bridge structures in the flexible DC transmission system to use the upper transistors to conduct, and controlling all full-bridge modules at the positive bus pole to control the external positive voltage, and controlling all full-bridge modules at the negative bus pole to control the external negative voltage, the flexible DC transmission system can ensure that the operating voltage of the two poles in parallel is the same during operation, meeting the operating conditions of the two poles in parallel.

[0107] 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.

[0108] The present application also provides an electronic device, Figure 10The provided electronic device 1000 includes a memory 1010, a processor 1020, and a computer program 1010 stored in the memory 1010 and capable of running on the processor 1020. When the computer program 1010 is executed by the processor, the various processes of the above-mentioned line de-icing method embodiment are implemented and the same technical effects can be achieved. To avoid repetition, they are not described here.

[0109] The present application also provides a computer-readable storage medium. Figure 11 The computer readable storage medium 1100 provided stores a computer program 1010. When the computer program 1010 is executed by the processor, the various processes of the above-mentioned line de-icing method embodiment are implemented and the same technical effect can be achieved. To avoid repetition, it will not be described here.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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)).

[0119] 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.

[0120] 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 A step that specifies a function in one or more boxes.

[0121] 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.

[0122] 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.

[0123] 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, conductor switches are provided at both ends of the DC line, the sending-end converter station and the receiving-end converter station respectively include a busbar positive pole and a busbar negative pole, the busbar positive pole and the busbar negative pole respectively have at least one 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 grounding pole line; When the flexible direct current transmission system is in a normal operating mode, the conductor switch, 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 conductor switch, the bypass switch, the metal return line switch, and the earth return line switch are controlled so that the bus positive electrode and the bus negative electrode in the sending-end converter station form a parallel circuit, and the parallel circuit is connected to the direct current line.

2. The system according to claim 1, wherein: When the flexible direct current transmission system is in normal operating mode, each bypass switch and metal return line switch is disconnected, each earth return line switch and the conductor switch is closed, each converter valve group in the sending-end converter station is connected in series, and each converter valve group in the receiving-end converter station is connected in series.

3. The system according to claim 1, wherein: The DC line connected between the sending-end converter station and the receiving-end converter station includes a first DC line and a second DC line, the conductor switches located at both ends of the first DC line include a first conductor switch and a second conductor switch, and the conductor switches located at both ends of the second DC line include a third conductor switch and a fourth conductor switch; When the flexible direct current transmission system is in the ice-melting mode, the first conductor switch and the second conductor switch are closed, or the third conductor switch and the fourth conductor switch are closed; each metal return line switch is closed, each earth return line switch is closed, and the bus positive electrode and the bus negative electrode in the sending-end converter station form a parallel circuit.

4. The system according to claim 3, characterized in that When there are two converter valve groups at the positive pole of the busbar and the negative pole of the busbar respectively, the two converter valve groups at the positive pole of the busbar are connected in parallel with the first bypass switch and the second bypass switch respectively, and the two converter valve groups at the negative pole of the busbar are connected in parallel with the third bypass switch and the fourth bypass switch respectively; When the flexible direct current power transmission system is in an ice-melting mode, the first bypass switch and the second bypass switch, or the third bypass switch and the fourth bypass switch are closed.

5. The system according to claim 3, wherein: 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; Furthermore, after the parallel loop formed by the bus positive electrode and the bus negative electrode in the sending-end converter station 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: When there are two converter valve groups at the positive pole of the busbar and the negative pole of the busbar respectively, in one of the converter stations of the sending-end converter station or the receiving-end converter station, there is a line selection switch group between the two converter valve groups located at the same pole; wherein, in the sending-end converter station or the receiving-end converter station, there is a line selection switch group for the first converter valve group and the second converter valve group located at the positive pole of the busbar, and there is a line selection switch group for the third converter valve group and the fourth converter valve group located at the negative pole of the busbar.

7. The system according to claim 6, characterized in that 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.

8. The system according to claim 7, characterized in that When the flexible direct current transmission system is in a normal operating mode, the first switch and the fourth switch of the 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, each earth return line switch and the conductor switch are 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.

9. The system according to claim 7, wherein: The DC line connected between the sending-end converter station and the receiving-end converter station includes a first DC line and a second DC line, the conductor switches at both ends of the first DC line include a first conductor switch and a second conductor switch, and the conductor switches at both ends of the second DC line include a third conductor switch and a fourth conductor switch; The two converter valve groups located at the positive pole of the busbar are respectively connected in parallel with the first bypass switch and the second bypass switch, and the two converter valve groups located at the negative pole of the busbar are respectively connected in parallel with the third bypass switch and the fourth bypass switch; When the flexible direct current transmission system is in the ice-melting mode, the first switch and the fourth switch of each line selection switch group are opened, and the second switch, the third switch, and the fifth switch are closed. The first converter valve group and the second converter valve group located at the positive pole of the busbar in the sending-end converter station are connected in parallel, and the third converter valve group and the fourth converter valve group located at the negative pole of the busbar in the sending-end converter station are connected in parallel. Each metal return line switch in the sending-end converter station is closed, and the positive pole of the busbar and the negative pole of the busbar in the sending-end converter station form a parallel circuit. The first bypass switch and the second bypass switch in the receiving-end converter station, or the third bypass switch and the fourth bypass switch in the receiving-end converter station are closed; The first conductor switch and the second conductor switch, or the third conductor switch and the fourth conductor switch are closed, and each earth return line switch is closed.

10. A line deicing method, characterized in that: Applied to the flexible direct current transmission system according to any one of claims 1 to 9, wherein each converter valve group in the flexible direct current transmission system adopts a full-bridge structure or a half-bridge structure, the method comprises: Controlling the lower transistor in the half-bridge structure to be turned on; after the lower transistor is turned on, the half-bridge structure is bypassed; The full-bridge structure is controlled at the bus positive pole according to an external positive voltage, and the full-bridge structure is controlled at the bus negative pole according to an external negative voltage, so that the operating voltages of the bus positive pole and the bus negative pole are the same after the bus positive pole and the bus negative pole in the sending-end converter station form a parallel circuit.

11. 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 the computer program implements the line ice melting method according to claim 10 when executed by the processor.

12. 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 10 is implemented.

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