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 of the sending-end converter station, the second converter valve group of the sending-end converter station and the fourth converter valve group of the sending-end converter station form a parallel loop, and the receiving-end converter station is short-circuited. According to the embodiment of the invention, the line selection switch is added, the receiving end converter station is short-circuited when the flexible DC power transmission system is in the ice melting mode, and line ice melting is realized based on the flexible DC power transmission system.

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 by adding a line selection switch and related controls.

[0005] On the one hand, an embodiment of the present application provides a flexible direct current transmission system, the system including a sending-end converter station and a receiving-end converter station, a direct current line being 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 including a bus positive pole and a bus negative pole, a first converter valve group and a second converter valve group being present at the bus positive pole in each converter station, a third converter valve group and a fourth converter valve group being present at the bus negative pole in each converter station, a bypass switch being connected in parallel to each converter valve group, a metal return line switch being connected between the pole line and the neutral line of the same pole, an earth return line switch being connected between the neutral line and the grounding pole line, wherein a line selection switch group is present between the first converter valve group of the sending-end converter station and the second converter valve group of the sending-end converter station;

[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 and the direct current line form a series circuit; 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 of the sending-end converter station, the second converter valve group of the sending-end converter station and the fourth converter valve group of the sending-end converter station form a parallel circuit, and the receiving-end converter station is short-circuited.

[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 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 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, when the flexible HVDC 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, the first converter valve group of the sending-end converter station and the second converter valve group of the sending-end converter station are connected in parallel, each metallic return line switch in the sending-end converter station is closed, and the first converter valve group of the sending-end converter station and the fourth converter valve group of the sending-end converter station are connected in parallel;

[0010] Each metal return line in the receiving-end converter station is closed, or the two bypass switches respectively connected in parallel with the first converter valve group and the second converter valve group of the receiving-end converter station are closed, or the two bypass switches respectively connected in parallel with the third converter valve group and the fourth converter valve group of the receiving-end converter station are closed, and the receiving-end converter station is short-circuited.

[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 circuit formed by the first converter valve group of the sending-end converter station, the second converter valve group of the sending-end converter station and the fourth converter valve group of the sending-end converter station 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, a ground wire is further connected between the sending-end converter station and the receiving-end converter station, wherein conductor de-icing switches are provided at both ends of the DC line, and ground wire de-icing switches are provided at both ends of the ground wire.

[0014] When the flexible direct current transmission system performs conductor ice melting, the conductor ice melting switch is closed and the ground wire ice melting switch is opened; when the flexible direct current transmission system performs ground wire ice melting, the conductor ice melting switch is opened and the ground wire ice melting switch is closed.

[0015] 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:

[0016] collecting the current and DC current reference value of the receiving-end converter station when it is short-circuited;

[0017] Obtaining an initial voltage reference value based on the current of the receiving-end converter station when it is short-circuited and the DC current reference value;

[0018] Limiting the initial voltage reference value based on a preset voltage limit value to obtain a target voltage reference value;

[0019] The target voltage reference value is subjected to voltage conversion to obtain a three-phase reference wave; the three-phase reference wave is used to generate a modulation signal to control each converter valve group.

[0020] 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:

[0021] A current data acquisition module, used for collecting the current and DC current reference value of the receiving-end converter station when the receiving-end converter station is short-circuited;

[0022] a voltage reference value generating module, configured to obtain an initial voltage reference value based on the current of the receiving-end converter station when it is short-circuited and the DC current reference value;

[0023] a voltage limiting module, configured to limit the initial voltage reference value based on a preset voltage limit value to obtain a target voltage reference value;

[0024] The reference wave generating module is used to perform voltage conversion on the target voltage reference value to obtain a three-phase reference wave; the three-phase reference wave is used to generate a modulation signal to control each converter valve group.

[0025] 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 any one of the line de-icing methods when executed by the processor.

[0026] 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, any one of the line de-icing methods is implemented.

[0027] 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.

[0028] 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 provided between the first converter valve group of the sending-end converter station and the second converter valve group of the sending-end converter station. Specifically, when the HVDC Flexible system is in normal operation, the line selection switch group, bypass switch, metallic return switch, and earth return switch are controlled so that each converter valve group forms a series circuit with the DC line. When the HVDC Flexible system is in de-icing mode, the line selection switch group, bypass switch, metallic return switch, and earth return switch are controlled so that the first converter valve group at the sending-end converter station, the second converter valve group at the sending-end converter station, and the fourth converter valve group at the sending-end converter station form a parallel circuit, short-circuiting the receiving-end converter station. By adding line selection switches, the receiving-end converter station is short-circuited when the HVDC Flexible system is in de-icing mode, increasing the DC current and achieving line de-icing within the HVDC Flexible system itself. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the original wiring diagram of the flexible direct current transmission system provided in the embodiment of the present application;

[0030] Figure 2 This is a wiring diagram of the flexible DC transmission system provided in an embodiment of the present application after a line selection switch is added;

[0031] Figure 3 This is a wiring diagram of a flexible DC power transmission system suitable for ground wire ice melting provided by an embodiment of the present application;

[0032] Figure 4 This is a flowchart of the steps of a line ice melting method according to an embodiment of the present application;

[0033] Figure 5 This is a control block diagram of the flexible direct current transmission system provided by an embodiment of the present application;

[0034] Figure 6 This is a structural block diagram of a line ice melting device according to an embodiment of the present application;

[0035] Figure 7 This is a structural block diagram of an electronic device provided in an embodiment of the present application;

[0036] Figure 8 This is a structural block diagram of a computer-readable storage medium provided in an embodiment of the present application. DETAILED DESCRIPTION

[0037] 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.

[0038] In the embodiments of this application, by adding line selection switches and related controls, line de-icing is achieved within the Flexible DC transmission system itself, offering the advantages of a small footprint and low development costs. On the one hand, by adding a small number of line selection switches, the receiving converter station is short-circuited when the Flexible DC transmission system is in de-icing mode, which is a power outage de-icing method for the Flexible DC transmission system. On the other hand, the voltage reference value used to generate the reference wave is limited by the preset voltage limit value of the voltage limiter, thereby controlling the DC voltage and preventing excessive DC current.

[0039] It should be noted that the line de-icing principle of the flexible DC transmission system in the embodiment of the present application is to increase the valve side voltage to reduce the AC side current, thereby increasing the DC side current to achieve line de-icing. However, in the embodiment of the present application, due to the short circuit of the receiving end converter station, the DC line cannot transmit power normally. At this time, in order to maintain the stability of the DC voltage, the DC current of the sending end converter station tends to increase. The voltage limit value preset by the voltage limiter can be used to limit the DC current to avoid excessive DC current.

[0040] Reference Figure 1, showing the original wiring diagram of the flexible DC transmission system provided by an embodiment of the present application. The flexible DC transmission system may include a sending-end converter station and a receiving-end converter station. In this embodiment of the present application, the de-icing target 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.

[0041] 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. For example, if it is UHVDC, Figure 2 As 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.

[0042] Optionally, each converter station may be connected to a grounded pole line 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.

[0043] Optional, in UHVDC, e.g. Figure 1 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).

[0044] 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.

[0045] 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.

[0046] 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:

[0047]

[0048] 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.

[0049] In the embodiment of the present application, Figure 1 The wiring of the flexible DC transmission system shown in the figure is modified by hardware circuit. Specifically, a line selection switch can be added. By controlling the circuit hardware of the added line selection switch, the receiving end converter station is short-circuited when the flexible DC transmission system is in de-icing mode, thereby increasing the DC current and achieving line de-icing based on the flexible DC transmission system itself.

[0050] Specifically, refer to Figure 2 , shows a wiring diagram of the flexible DC transmission system provided in an embodiment of the present application after a line selection switch is added.

[0051] Optionally, you can Figure 1 Based on the flexible DC transmission system wiring shown in the figure, in one of the converter stations at the sending end and the receiving end, a line selection switch group is selected between the two valve groups at one of the poles to achieve the transformation of the converter valve group wiring. In the embodiment of the present application, the first converter valve group and the second converter valve group at the positive pole of the busbar in the sending end converter station are taken as an 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, 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 in the sending-end converter station is maintained, and the original connection of each converter valve group in the receiving-end converter station is maintained.

[0052] 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.

[0053] When the HVDC Flexible system is in normal operating mode, the line selection switch group, bypass switch, metallic return line switch, and earth return line switch 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, the first and fourth switches of the line selection switch group are opened, the second, third, and fifth switches are closed, each bypass switch and metallic return line switch is opened, and each earth return line switch is closed, so that the first, second, third, and fourth converter valve groups in the sending-end converter station are connected in series, and the first, second, third, and fourth converter valve groups in the receiving-end converter station are connected in series, so that each converter valve group forms a series circuit with the DC line.

[0054] When the flexible direct current transmission system is in ice-melting mode, the line selection switch group, bypass switch, metal return line switch and earth return line switch can be controlled so that the first converter valve group of the sending-end converter station, the second converter valve group of the sending-end converter station and the fourth converter valve group of the sending-end converter station form a parallel circuit, and the receiving-end converter station is short-circuited. Specifically, 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, the first converter valve group of the sending-end converter station and the second converter valve group of the sending-end converter station are connected in parallel, and each metal return line switch in the sending-end converter station is closed, so that the first converter valve group of the sending-end converter station and the fourth converter valve group of the sending-end converter station are connected in parallel; and each metal return line in the receiving-end converter station is closed, or the two bypass switches respectively connected in parallel with the first converter valve group and the second converter valve group of the receiving-end converter station are closed, or the two bypass switches respectively connected in parallel with the third converter valve group and the fourth converter valve group of the receiving-end converter station are closed, so that the receiving-end converter station is short-circuited.

[0055] In some embodiments of the present application, when the flexible direct current transmission system enters the de-icing mode, the converter valve group of the flexible direct current transmission system is closed; and after the parallel circuit formed by the first converter valve group of the sending-end converter station, the second converter valve group of the sending-end converter station and the fourth converter valve group of the sending-end converter station is connected to the DC line and the receiving-end converter station is short-circuited, the converter valve group of the flexible direct current transmission system is opened.

[0056] It should be noted that the second DC current of the DC line when the receiving converter station is short-circuited is greater than the first DC current generated when the DC line and each converter valve group form a series circuit. 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 operation mode. Figure 2 The circuit connection structure shown and the short-circuit control of the receiving-end converter station can increase the line current of the DC line without maintaining DC power transmission.

[0057] For example, when the flexible DC transmission system is in normal operation mode, that is, bipolar operation, the following can be closed: Figure 2 The switches 2, 3, and 5 in each line selection switch group shown are disconnected. Figure 2 The switches 1 and 4 in each line selection switch group shown in FIG. Figure 2 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 2 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 the metallic return switches 1 and 2 in the sending-end converter station, so that the converter valve group 1 and the converter valve group 4 in the sending-end converter station are connected in parallel.

[0062] S4: Close the metallic return switches 1 and 2 in the receiving-end converter station, or close the bypass switches 1 and 2 in the receiving-end converter station, or close the bypass switches 3 and 4 in the receiving-end converter station, so that the receiving-end converter station is short-circuited and enters a short-circuit state. In the short-circuit state, normal power cannot be transmitted to the DC line.

[0063] S5: 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.

[0064] In such Figure 2 Based on the modified HVDC flexible transmission system shown in the figure, after following the above steps, a line selection switch is added to achieve short-circuiting of the receiving converter station when the HVDC flexible transmission system is in de-icing mode, thereby increasing the DC current and achieving line de-icing based on the HVDC flexible transmission system itself.

[0065] In a preferred embodiment of the present application, the embodiment of the present application provides Figure 2 The modified wiring structure of the flexible DC transmission system shown can also be used for ground wire ice melting.

[0066] Optional, in Figure 2 On the basis of the flexible DC transmission system wiring shown in FIG, a ground wire can be connected between the sending-end converter station and the receiving-end converter station, and conductor de-icing switches, such as conductor switches 1, 2, 3, and 4, can be added at both ends of the DC line. In addition, ground wire de-icing switches, such as ground wire switches 1, 2, 3, and 4, can be added at both ends of the ground wire to obtain the following: Figure 3 The flexible DC transmission system suitable for ground line ice melting is shown.

[0067] like Figure 3 As shown, when the flexible DC transmission system performs conductor de-icing, the conductor de-icing switch can be closed and the ground wire de-icing switch can be opened to achieve de-icing of the DC line; when the flexible DC transmission system performs ground wire de-icing, the conductor de-icing switch can be opened and the ground wire de-icing switch can be closed to achieve de-icing of the ground wire. For example, when the flexible DC transmission system performs conductor de-icing, the conductor de-icing switch can be opened and the ground wire de-icing switch can be closed to achieve de-icing of the ground wire. Figure 3 The conductor switches 1, 2, 3, and 4 are closed, and the ground wire switches 1, 2, 3, and 4 are open. When the ground wire of the flexible DC transmission system is de-icing, the following Figure 3 The conductor switches 1, 2, 3, 4 are shown open, and the ground wires 1, 2, 3, 4 are shown closed.

[0068] It should be noted that for Figure 3 The circuit hardware control of the flexible DC transmission system shown in the figure can be referred to Figure 2 Circuit hardware control of the flexible DC transmission system; only the conductor de-icing switch and the ground wire de-icing switch are added on the basis of the above circuit hardware control, and the de-icing object of the current flexible DC transmission system is determined by controlling the corresponding switches. The embodiments of the present application are not described in detail here.

[0069] Furthermore, due to the short circuit of the receiving-end converter station, the DC line cannot transmit power normally. At this time, in order to maintain the stability of the DC voltage at the sending-end converter station, the DC current tends to increase. The embodiment of the present application can limit the voltage through the preset voltage limit value of the voltage limiter to avoid excessive DC current.

[0070] 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:

[0071] Step S401, collecting the current and DC current reference value of the receiving-end converter station when it is short-circuited;

[0072] Step S402, obtaining an initial voltage reference value based on the current of the receiving-end converter station when it is short-circuited and a DC current reference value;

[0073] Step S403, limiting the initial voltage reference value based on a preset voltage limit value to obtain a target voltage reference value;

[0074] Step S404: performing voltage conversion on the target voltage reference value to obtain a three-phase reference wave; the three-phase reference wave is used to generate a modulation signal to control each converter valve group.

[0075] Optionally, PI (Proportional-Integral Control, a control algorithm based on proportional P and integral I) control can be used. Figure 2 As well as Figure 3 The flexible DC transmission system shown is controlled by software logic.

[0076] Specifically, refer to Figure 5 , 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 The operation mode shown in the figure can be specifically manifested as following: after collecting the actual value and comparing it with the set value, it is adjusted by the proportional integral controller (i.e. PI controller), and then the modulation signal is obtained after voltage conversion, and the modulation signal is input to the valve control module of the converter valve to realize the control of the converter valve.

[0077] For example, the current of the receiving converter station when it is short-circuited, that is, the DC current measurement value I m and DC current reference value I ref , the DC current measurement value I m and DC current reference value I ref Input to PI controller, output is the preliminary voltage reference value U dref ', through the voltage limiter to the initial voltage reference value U dref 'Perform amplitude limiting to obtain the target voltage reference value U dref Then, the target voltage reference value U dref Perform voltage conversion 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 to the converter valve control module to control the converter valve. ref The current is 1 / 3 of the line de-icing current. However, the current at the receiving-end converter station tends to increase when it is short-circuited. The voltage limiter can be used to limit the current by setting a preset voltage limit value to avoid excessive DC current while achieving de-icing of the DC line and / or ground wire.

[0078] Among them, the preliminary voltage reference value U drefThe limiting can be achieved by limiting the initial voltage reference value based on a preset voltage limit value. The preset voltage limit value can be determined based on a voltage limiter. For example, the calculation formula of the preset voltage limit value can be as follows:

[0079]

[0080] Where U max is the preset voltage limit value, which refers to the maximum voltage value that the DC line can withstand under icing conditions; I dmax The maximum thermal current that the DC line can withstand under icing conditions, usually three times the rated current; R max is the maximum resistance of the DC line. It should be noted that this is the maximum resistance after correction for the DC line deviation and temperature along the line.

[0081] In the embodiments of this application, by adding line selection switches and related controls, line de-icing is achieved within the Flexible DC transmission system itself, offering the advantages of a small footprint and low development costs. On the one hand, by adding a small number of line selection switches, the receiving converter station is short-circuited when the Flexible DC transmission system is in de-icing mode, which is a power outage de-icing method for the Flexible DC transmission system. On the other hand, the voltage reference value used to generate the reference wave is limited by the preset voltage limit value of the voltage limiter, thereby controlling the DC voltage and preventing excessive DC current.

[0082] 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.

[0083] 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 2 and Figure 3 The flexible DC transmission system shown in the figure may specifically include the following modules:

[0084] The current data acquisition module 601 is used to collect the current and DC current reference value of the receiving-end converter station when it is short-circuited;

[0085] A voltage reference value generating module 602 is configured to obtain an initial voltage reference value based on the current of the receiving-end converter station when the converter station is short-circuited and a DC current reference value;

[0086] The voltage limiting module 603 is used to limit the initial voltage reference value based on a preset voltage limit value to obtain a target voltage reference value;

[0087] The reference wave generating module 604 is used to perform voltage conversion on the target voltage reference value to obtain a three-phase reference wave; the three-phase reference wave is used to generate a modulation signal to control each converter valve group.

[0088] In the embodiments of this application, by adding line selection switches and related controls, line de-icing is achieved within the Flexible DC transmission system itself, offering the advantages of a small footprint and low development costs. On the one hand, by adding a small number of line selection switches, the receiving converter station is short-circuited when the Flexible DC transmission system is in de-icing mode, which is a power outage de-icing method for the Flexible DC transmission system. On the other hand, the voltage reference value used to generate the reference wave is limited by the preset voltage limit value of the voltage limiter, thereby controlling the DC voltage and preventing excessive DC current.

[0089] 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.

[0090] 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 line de-icing method embodiment are implemented and the same technical effects can be achieved. To avoid repetition, they are not described here.

[0091] 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, 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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)).

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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, and 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 of the sending-end converter station and the second converter valve group of the sending-end converter station; 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 and the direct current line form a series circuit; 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 of the sending-end converter station, the second converter valve group of the sending-end converter station and the fourth converter valve group of the sending-end converter station form a parallel circuit, and the receiving-end converter station is short-circuited.

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 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 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: 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 opened, the second switch, the third switch and the fifth switch are closed, the first converter valve group of the sending-end converter station and the second converter valve group of the sending-end converter station are connected in parallel, each metallic return line switch in the sending-end converter station is closed, and the first converter valve group of the sending-end converter station and the fourth converter valve group of the sending-end converter station are connected in parallel; Each metal return line in the receiving-end converter station is closed, or the two bypass switches respectively connected in parallel with the first converter valve group and the second converter valve group of the receiving-end converter station are closed, or the two bypass switches respectively connected in parallel with the third converter valve group and the fourth converter valve group of the receiving-end converter station are closed, and the receiving-end converter station is short-circuited.

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; Furthermore, after the parallel circuit formed by the first converter valve group of the sending-end converter station, the second converter valve group of the sending-end converter station and the fourth converter valve group of the sending-end converter station is connected to the DC line and the receiving-end converter station is short-circuited, the converter valve group of the flexible DC transmission system is opened.

6. The system according to claim 1, wherein: A ground wire is further connected between the sending-end converter station and the receiving-end converter station, wherein conductor de-icing switches are provided at both ends of the DC line, and ground wire de-icing switches are provided at both ends of the ground wire; When the flexible direct current transmission system performs conductor ice melting, the conductor ice melting switch is closed and the ground wire ice melting switch is opened; when the flexible direct current transmission system performs ground wire ice melting, the conductor ice melting switch is opened and the ground wire ice melting switch is closed.

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: collecting the current and DC current reference value of the receiving-end converter station when it is short-circuited; Obtaining an initial voltage reference value based on the current of the receiving-end converter station when it is short-circuited and the DC current reference value; Limiting the initial voltage reference value based on a preset voltage limit value to obtain a target voltage reference value; The target voltage reference value is subjected to voltage conversion to obtain a three-phase reference wave; the three-phase reference wave is used to generate a modulation signal to control each converter valve group.

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 current data acquisition module, used for collecting the current and DC current reference value of the receiving-end converter station when the receiving-end converter station is short-circuited; a voltage reference value generating module, configured to obtain an initial voltage reference value based on the current of the receiving-end converter station when it is short-circuited and the DC current reference value; a voltage limiting module, configured to limit the initial voltage reference value based on a preset voltage limit value to obtain a target voltage reference value; The reference wave generating module is used to perform voltage conversion on the target voltage reference value to obtain a three-phase reference wave; the three-phase reference wave is used to generate a modulation signal to control each converter valve group.

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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