Line ice melting method based on flexible direct current power transmission system and related product

Abstract

The embodiment of the invention relates to the technical field of line control, and provides a line ice melting method based on a flexible direct current power transmission system and a related product, when the flexible direct current power transmission system is in a normal operation mode, a line selection switch group and a bypass switch are controlled, and each converter valve group and a direct current line form a series loop; when the flexible direct-current power transmission system is in an ice melting mode, the line selection switch group and the bypass switch are controlled, the two converter valve groups located at the same pole form a parallel loop, and the parallel loop is connected with a direct-current line; the method comprises the following steps: when a DC line is iced, obtaining a valve side current reference value, obtaining a three-phase reference wave based on the valve side current reference value, and superposing the three-phase reference wave to an original three-phase reference wave to obtain a valve side voltage; the valve side voltage is used for indicating power distribution of the alternating current side and the direct current side. According to the embodiment of the invention, by adding the line selection switch and related control, line ice melting is realized on the basis of the flexible direct-current power transmission system without power failure.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of line control technology, and in particular to a line de-icing method based on a flexible direct current transmission system 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 line de-icing method and related products based on a flexible direct current transmission system. By adding a line selection switch and related controls, line de-icing can be achieved based on the flexible direct current transmission system itself without the need for power outages.

[0005] In one aspect, an embodiment of the present application provides a line de-icing method based on a flexible direct current (HVDC) transmission system, the flexible direct current (HVDC) transmission system including a sending-end converter station and a receiving-end converter station, a DC 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, two converter valve groups each at the bus positive pole and the bus negative pole, each converter valve group being connected in parallel with a bypass switch, a line selection switch group being present between two converter valve groups located at the same pole in the sending-end converter station, and a line selection switch group being present between two converter valve groups located at the same pole in the receiving-end converter station;

[0006] When the flexible DC power transmission system is in a normal operating mode, the line selection switch group and the bypass switch are controlled, and each converter valve group forms a series circuit with the DC line; when the flexible DC power transmission system is in an ice-melting mode, the line selection switch group and the bypass switch are controlled, and two converter valve groups located at the same pole form a parallel circuit, and the parallel circuit is connected to the DC line;

[0007] The method comprises:

[0008] When the DC line is covered with ice, a valve-side current reference value is obtained, a three-phase reference wave is obtained based on the valve-side current reference value, and the three-phase reference wave is superimposed on the original three-phase reference wave to obtain a valve-side voltage; the valve-side voltage is used to indicate the power distribution between the AC side and the DC side.

[0009] 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.

[0010] In some embodiments of the present application, when the flexible direct current transmission system is in normal operating mode, the first switch and the fourth switch of each line selection switch group are disconnected, the second switch, the third switch and the fifth switch are closed, and each bypass switch is disconnected. The two converter valve groups located at the same pole in the sending-end converter station are connected in series, and the two converter valve groups located at the same pole in the receiving-end converter station are connected in series, and each converter valve group forms a series loop with the direct current line.

[0011] In some embodiments of the present application, when the flexible direct current transmission system is in the ice-melting mode, the second switch, the third switch, and the fifth switch of each line selection switch group are disconnected, the first switch and the fourth switch are closed, and each bypass switch is closed. The two converter valve groups located at the same pole in the sending-end converter station are connected in parallel, and the two converter valve groups located at the same pole in the receiving-end converter station are connected in parallel, and are connected to the DC line via the parallel loop formed by the converter valve groups.

[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] And, after the parallel loop formed by the converter valve group 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, obtaining the valve-side current reference value includes:

[0015] Obtaining a DC current reference value, as well as a DC current and an AC current of the flexible DC transmission system during normal operation;

[0016] The valve-side current reference value is calculated using the DC current reference value, the DC current during normal operation, and the AC current.

[0017] In some embodiments of the present application, obtaining a three-phase reference wave based on the valve-side current reference value includes:

[0018] Obtaining a valve-side current measurement value, inputting the valve-side current reference value and the valve-side current measurement value into a proportional-integral controller, and outputting a DC voltage reference value;

[0019] The valve-side rated voltage is obtained, and the three-phase reference wave is calculated using the DC voltage reference value and the valve-side rated voltage.

[0020] On the other hand, an embodiment of the present application provides a line de-icing device based on a flexible direct current (HVDC) transmission system, the flexible direct current (HVDC) transmission system including a sending-end converter station and a receiving-end converter station, a DC 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, two converter valve groups each at the bus positive pole and the bus negative pole, each converter valve group being connected in parallel with a bypass switch, a line selection switch group being present between two converter valve groups located at the same pole in the sending-end converter station, and a line selection switch group being present between two converter valve groups located at the same pole in the receiving-end converter station;

[0021] When the flexible DC power transmission system is in a normal operating mode, the line selection switch group and the bypass switch are controlled, and each converter valve group forms a series circuit with the DC line; when the flexible DC power transmission system is in an ice-melting mode, the line selection switch group and the bypass switch are controlled, and two converter valve groups located at the same pole form a parallel circuit, and the parallel circuit is connected to the DC line;

[0022] The device comprises:

[0023] A power distribution module is used to obtain a valve-side current reference value when the DC line is covered with ice, obtain a three-phase reference wave based on the valve-side current reference value, and superimpose the three-phase reference wave on the original three-phase reference wave to obtain a valve-side voltage; the valve-side voltage is used to indicate the power distribution between the AC side and the DC side.

[0024] In some embodiments of the present application, the power distribution module includes:

[0025] The valve-side current reference value calculation submodule is used to obtain a DC current reference value, as well as the DC current and AC current of the flexible DC transmission system during normal operation; and calculate the valve-side current reference value using the DC current reference value, the DC current and AC current during normal operation.

[0026] In some embodiments of the present application, the power distribution module includes:

[0027] The three-phase reference wave calculation submodule is used to obtain the valve side current measurement value, input the valve side current reference value and the valve side current measurement value into the proportional integral controller, and output a DC voltage reference value; obtain the valve side rated voltage, and use the DC voltage reference value and the valve side rated voltage to calculate the three-phase reference wave.

[0028] 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 when the computer program is executed by the processor, any one of the line de-icing methods based on a flexible direct current transmission system is implemented.

[0029] 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 based on a flexible direct current transmission system is implemented.

[0030] 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 based on a flexible direct current transmission system as described in the above aspects.

[0031] The embodiments of the present application provide a line de-icing method, device, equipment and storage medium based on a flexible direct current transmission system. The flexible direct current 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. There are two converter valve groups at the bus positive pole and the bus negative pole respectively. Each converter valve group is connected in parallel with a bypass switch. There is a line selection switch group between the two converter valve groups located at the same pole in the sending-end converter station. There is a line selection switch group between the two converter valve groups located at the same pole in the end converter station. Specifically, when the flexible DC transmission system is in normal operating mode, the line selection switch group and the bypass switch are controlled, and each converter valve group forms a series circuit with the DC line. Moreover, when the flexible DC transmission system is in de-icing mode, the line selection switch group and the bypass switch are controlled, and the two converter valve groups located at the same pole form a parallel circuit. The parallel circuit is connected to the DC line. By adding the line selection switch, the added The line selector switches perform circuit hardware control, making the flexible DC transmission system compatible with both normal operating mode and de-icing mode. De-icing mode can be used before or when icing is mild. In this de-icing mode, DC current continues to flow through the DC line. In normal operation, the DC line maintains bipolar operation, maximizing power transmission, ensuring both transmission power and de-icing. Furthermore, when the DC line is already iced, a valve-side current reference value can be obtained. A three-phase reference wave is derived based on the valve-side current reference value, and the three-phase reference wave is superimposed on the original three-phase reference wave to obtain the valve-side voltage. The resulting valve-side voltage can be used to indicate power distribution between the AC and DC sides. Because the reference wave is included in the calculation of the valve-side voltage, the valve-side voltage is increased to reduce the AC side current, thereby increasing the DC side current. This allows the DC line to maintain a high DC current when icing is severe, allowing for de-icing of severely iced DC lines. This achieves line de-icing within the flexible DC transmission system itself without requiring a power outage. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the original wiring diagram of the flexible direct current transmission system provided in the embodiment of the present application;

[0033] 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;

[0034] Figure 3 This is a basic control block diagram of the flexible DC transmission system provided in an embodiment of the present application;

[0035] Figure 4 This is a control block diagram of the flexible direct current transmission system provided by the embodiment of the present application after additional control is added;

[0036] Figure 5 This is a flowchart of the steps of a line de-icing method based on a flexible direct current transmission system according to an embodiment of the present application;

[0037] Figure 6 This is a structural block diagram of a line de-icing device based on a flexible direct current transmission system according to an embodiment of the present application;

[0038] Figure 7 This is a structural block diagram of an electronic device provided in an embodiment of the present application;

[0039] Figure 8 This is a structural block diagram of a computer-readable storage medium provided in an embodiment of the present application. DETAILED DESCRIPTION

[0040] 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.

[0041] In the embodiment of the present application, by adding a line selection switch and related controls, line de-icing is achieved based on the flexible direct current transmission system itself without the need for power outages, which has the advantages of small footprint and low development cost.

[0042] 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.

[0043] Optionally, in each converter station, such as Figure 1 As shown, it can be connected to the grounding pole line to form a DC loop. In some preferred embodiments of the present application, in each converter station, 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. This embodiment of the present application is not limited to this.

[0044] Optionally, each converter station usually contains a busbar positive pole and a busbar negative pole. If it is UHV DC, such as Figure 1As shown, each pole can have two converter valve groups respectively. For example, there are two converter valve groups at the positive pole of the busbar in the sending-end converter station or the receiving-end converter station, such as converter valve groups 1 and 2; there are two converter valve groups at the negative pole of the busbar in the sending-end converter station or the receiving-end converter station, such as converter valve groups 3 and 4.

[0045] Optional, in UHVDC, e.g. Figure 1 As shown, each valve group can be connected in parallel with a bypass switch, for example, converter valve group 1 is connected in parallel with bypass switch 1, converter valve group 2 is connected in parallel with bypass switch 2, converter valve group 3 is connected in parallel with bypass switch 3, and converter valve group 4 is connected in parallel with bypass switch 4.

[0046] 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.

[0047] 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.

[0048] 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:

[0049]

[0050] 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.

[0051] In the embodiment of the present application, Figure 1 The wiring of the flexible DC transmission system shown in the figure is modified through hardware circuit modification. Specifically, a line selection switch can be added. Before the DC line is covered with ice, the circuit hardware control of the added line selection switch is performed. This makes the flexible DC transmission system compatible with both normal operation mode and de-icing mode. Before de-icing or when de-icing is not severe, the de-icing mode can be used. In this de-icing mode, DC current will continue to flow through the DC line. In the normal operation mode, the DC still maintains bipolar operation, which can maximize the power transmission, thereby ensuring transmission power while taking into account de-icing.

[0052] 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.

[0053] Optionally, you can Figure 1 Based on the flexible DC transmission system wiring shown in FIG, a line selection switch group is added between the two valve groups located at the same pole in the sending end converter station and the receiving end converter station to realize the transformation of the converter valve group wiring. Figure 2 As shown, in the sending-end converter station and the receiving-end converter station, converter valve groups 1 and 2 are located at the positive pole of the busbar (assuming pole 1), and a line selection switch group is added between converter valve groups 1 and 2; converter valve groups 3 and 4 are located at the negative pole of the busbar (assuming pole 2), and a line selection switch group is added between converter valve groups 3 and 4. In this way, there is a line selection switch group between the two converter valve groups located at the same pole (including poles 1 and 2) in the sending-end converter station, and there is a line selection switch group between the two converter valve groups located at the same pole (including poles 1 and 2) in the receiving-end converter station.

[0054] 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.

[0055] When the HVDC Flexible system is in normal operating mode, the line selection switch groups and bypass 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, the first and fourth switches of each line selection switch group are open, the second, third, and fifth switches are closed, and each bypass switch is open. This allows two converter valve groups located on the same pole in a sending-end converter station to be connected in series, and two converter valve groups located on the same pole in a receiving-end converter station to be connected in series, so that each converter valve group forms a series circuit with the DC line.

[0056] When the HVDC Flexible system is in de-icing mode, the line selection switch groups and bypass switches can be controlled so that two converter valve groups located on the same pole form a parallel circuit, and this parallel circuit is connected to the DC line. Specifically, when the HVDC Flexible system is in de-icing mode, the second, third, and fifth switches of each line selection switch group are opened, the first and fourth switches are closed, and each bypass switch is closed. This connects the two converter valve groups located on the same pole in the sending-end converter station in parallel, and the two converter valve groups located on the same pole in the receiving-end converter station in parallel. The parallel circuit formed by the converter valve groups is then connected to the DC line.

[0057] 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 converter valve group is connected to the DC line, the converter valve group of the flexible direct current transmission system is opened.

[0058] It should be noted that the second DC current generated when the DC line is connected to the parallel circuit formed by two converter valve groups located at the same pole is greater than the first DC current generated when the DC line forms a series circuit with each converter valve group. That is, the DC current generated when the flexible DC transmission system is in the de-icing mode is greater than the DC current generated when the flexible DC transmission system is in the normal operation mode. Figure 2 The circuit wiring structure shown can increase the line current of the DC line to reduce the probability of line icing while ensuring normal power transmission.

[0059] 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 Switches 1 and 4 in each line selection switch group shown are disconnected as shown in FIG. Figure 2 As shown, each bypass switch is disconnected, forming a series circuit between each converter valve group and the DC line, achieving circuit connection in normal operating mode. Optionally, if 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, then the metal return line switches in both the sending-end converter station and the receiving-end converter station are disconnected, and the earth return line switches are closed. This embodiment of the present application is not limited to this.

[0060] 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:

[0061] 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.

[0062] S2: Close switches 1 and 4 at poles 1 and 2 in the sending-end converter station, and open switches 2, 3, and 5 at poles 1 and 2 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, and converter valve group 3 and converter valve group 4 are connected in parallel.

[0063] S3: Close switches 1 and 4 located at poles 2 and 2 in the receiving-end converter station, and open switches 2, 3, and 5 located at poles 1 and 2 in the receiving-end converter station, so that converter valve group 1 and converter valve group 2 in the receiving-end converter station are connected in parallel, and converter valve group 3 and converter valve group 4 are connected in parallel.

[0064] S4: 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.

[0065] In such Figure 2 Based on the modified flexible DC transmission system shown, after operating according to the above steps, the parallel circuit formed by the two converter valve groups located at the same pole can be connected to the DC line.

[0066] Optionally, PI (Proportional-Integral Control, a control algorithm based on proportional P and integral I) control can be used. Figure 2 The flexible DC transmission system shown is controlled by software logic.

[0067] Specifically, refer to Figure 3 , shows the basic control block diagram of the flexible DC transmission system provided by the embodiment of the present application. After the flexible DC transmission system is unlocked, the converter valve group can be operated as follows Figure 3 The operation mode shown is as follows: the actual value is collected and compared with the set value, and then adjusted by the proportional integral controller (i.e., PI controller). Then, the modulation signal is obtained after the coordinate transformation, and the modulation signal is input into the valve control module of the converter valve to realize the control of the converter valve.

[0068] For example, the active power reference value P ref and active power measurement value P m Input to the PI controller, and output the DC current reference value I dcref , then the DC current reference value I dcref and the DC current measurement value I dcm Input to the PI controller and output the direct axis voltage reference value U dref ; The reactive power reference value Q ref and reactive power measurement Q m Input to the PI controller, and output the quadrature axis current reference value I qref , then the quadrature-axis current reference value I qref and the quadrature axis current measurement value I qm Input to PI controller, output is quadrature axis voltage reference value U qref Then, the direct axis voltage reference value U can be obtained by the output dref and the quadrature axis voltage reference value U qref Perform the inverse Parker transform, i.e., dq→abc transform, where the direct axis refers to the d axis and the quadrature axis refers to the q axis. At this time, the signal in the rotating coordinate system (dq axis) can be converted back to the three-phase stationary coordinate system (abc) to obtain the three-phase reference wave U aref 、U bref 、U crefThe three-phase reference wave obtained by the transformation can be used to generate a modulation signal, which can be input into the converter valve control module to control the converter valve. At this time, the DC current flowing through each valve group is still I dcN , the AC side current is I acN , but when the DC transmission system is running, the DC voltage of the DC line is 0.5U dcN , the DC current is 2I dcN , thereby enabling the transmission system to provide a higher DC current to the DC line in the ice-melting mode, thereby enabling the transmission system to provide a higher DC current to the DC line in the ice-melting mode.

[0069] It should be noted that, in Figure 2 When controlling the wiring structure shown in the figure, the Figure 3 The logic algorithm shown in the figure increases the DC current of the ice-melting line by 2 times, which can reduce the probability of line icing while ensuring normal power transmission.

[0070] Furthermore, when the DC line is already iced or severely iced, even if the 2I dcN Even if the DC current is too low, it cannot guarantee that the line can melt the ice. At this time, the control and regulation method can be used to increase the AC side voltage of the converter valve, reduce the AC side current, and thus increase the DC side current. In this way, the DC line can maintain a high DC current when the ice is severely covered, and the severely iced DC line can be melted.

[0071] In the embodiment of the present application, Figure 3 Add additional control links based on the basic control block diagram shown in Figure 3 The original control framework shown in the figure is improved to obtain Figure 4 The control block diagram shown in FIG. Figure 4 The control block diagram shown controls the converter valve to increase the valve side voltage.

[0072] Optional, such as Figure 4 As shown, the added additional control link can be specifically manifested as calculating the valve side current based on the valve side current calculation module, and then calculating the reference wave. When calculating the valve side voltage, the reference wave obtained by the above calculation is added, and the valve side voltage is increased to reduce the AC side current, thereby increasing the DC side current.

[0073] Specifically, refer to Figure 5 , shows a flowchart of the steps of a line de-icing method based on a flexible DC transmission system provided in an embodiment of the present application, which may specifically include the following steps:

[0074] Step S501: When the DC line is iced, a valve-side current reference value is obtained, a three-phase reference wave is obtained based on the valve-side current reference value, and the three-phase reference wave is superimposed on the original three-phase reference wave to obtain a valve-side voltage.

[0075] The valve-side current may refer to the current flowing through the converter valve group; the valve-side voltage may refer to the voltage on both sides of the converter valve group.

[0076] In some embodiments of the present application, when a DC line is iced, the valve-side voltage can be increased to reduce the AC-side current, thereby increasing the DC-side current. The increase in the valve-side voltage can be achieved by superimposing a three-phase reference wave onto an original three-phase reference wave when calculating the valve-side voltage.

[0077] Alternatively, the original three-phase reference wave may refer to Figure 3 The U shown aref 、U bref 、U cref ; The three-phase reference wave used to be superimposed on the original three-phase reference wave can be calculated based on the valve side current reference value.

[0078] Specifically, the calculation of the valve side current reference value can be achieved through the valve side current calculation module. Figure 4 As shown, the DC current reference value I can be obtained through the valve side current calculation module dcref , active power reference value P ref and reactive power reference value Q ref Calculate the valve side current reference value I vref Specifically, the valve side current reference value can be calculated by using the DC current reference value, the DC current during normal operation, and the AC current.

[0079] For example, the calculation formula of the valve-side current calculation module may be as follows:

[0080]

[0081] Where, I dcN is the DC current of the flexible DC transmission system during normal operation; I acN It is the AC current of the flexible DC transmission system during normal operation.

[0082] The calculation of the three-phase reference wave can be expressed as obtaining the valve side current measurement value I vm , set the valve side current reference value I vm and the valve side current measurement value I vref Input to the proportional integral controller (PI controller), the output is the DC voltage reference value U vref ; Then, obtain the valve side rated voltage U vN , using the DC voltage reference value Uvref and valve side rated voltage U vN , calculate the three-phase reference wave U aref2 、U bref2 、U cref2 .

[0083] For example, the calculation formula of the reference wave can be as follows:

[0084]

[0085]

[0086]

[0087] In the formula, n can usually be taken as 2, indicating the superposition of 2-fold frequency harmonics.

[0088] After the three-phase reference wave is superimposed on the original three-phase reference wave, the valve side voltage can be obtained. The obtained valve side voltage can be used to indicate the power distribution between the AC side and the DC side. At this time, the AC side voltage of the converter valve can be increased to reduce the AC current of the converter valve, thereby increasing the current on the DC side while ensuring that the current tolerance value of the converter valve is not exceeded. It should be noted that, if Figure 4 The control framework shown can increase the DC side current by a maximum of 1.414 times, that is, the DC side current can reach a maximum of 2.828 times, thereby enabling the DC transmission system to maintain a higher DC current and achieve the effect of line de-icing.

[0089] In an embodiment of the present application, by adding a line selection switch and performing circuit hardware control of the added line selection switch before the DC line is covered with ice, the flexible DC transmission system is compatible with both a normal operating mode and an ice-melting mode. The ice-melting mode can be used before ice is formed or when ice is not severely formed. In this ice-melting mode, DC current will continue to flow into the DC line, and the DC will still maintain bipolar operation in the normal operating mode, thereby maintaining the power transmission to the greatest extent possible, thereby ensuring transmission power while taking into account ice melting. Furthermore, when the DC line is covered with ice, a reference wave is added to the calculation of the valve-side voltage to increase the valve-side voltage, thereby reducing the AC-side current and thereby increasing the DC-side current. This allows the DC line to maintain a high DC current when ice is severely formed, and the severely iced DC line can be melted, thereby achieving the purpose of line ice melting based on the flexible DC transmission system itself without the need for power outages.

[0090] 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.

[0091] Reference Figure 6 , showing a structural block diagram of a line de-icing device based on a flexible direct current transmission system provided by an embodiment of the present application, the flexible direct current 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, two converter valve groups are respectively present at the bus positive pole and the bus negative pole, each converter valve group is connected in parallel with a bypass switch, a line selection switch group is present between the two converter valve groups located at the same pole in the sending-end converter station, and a line selection switch group is present between the two converter valve groups located at the same pole in the receiving-end converter station;

[0092] When the HVDC Flexible system is in normal operation mode, the line selection switch group and bypass switches are controlled, and 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 and bypass switches are controlled, and two converter valve groups located at the same pole form a parallel circuit, which is connected to the DC line.

[0093] like Figure 6 The circuit de-icing device shown may specifically include the following modules:

[0094] The power distribution module 601 is used to obtain a valve-side current reference value when the DC line is covered with ice, obtain a three-phase reference wave based on the valve-side current reference value, and superimpose the three-phase reference wave on the original three-phase reference wave to obtain a valve-side voltage; the valve-side voltage is used to indicate the power distribution between the AC side and the DC side.

[0095] In some embodiments of the present application, the power distribution module 601 may include the following submodules:

[0096] The valve-side current reference value calculation submodule is used to obtain the DC current reference value, as well as the DC current and AC current of the flexible DC transmission system during normal operation; the valve-side current reference value is calculated using the DC current reference value, the DC current and AC current during normal operation.

[0097] In some embodiments of the present application, the power distribution module 601 may include the following submodules:

[0098] The three-phase reference wave calculation submodule is used to obtain the valve side current measurement value, input the valve side current reference value and the valve side current measurement value into the proportional integral controller, and output a DC voltage reference value; obtain the valve side rated voltage, and use the DC voltage reference value and the valve side rated voltage to calculate the three-phase reference wave.

[0099] In an embodiment of the present application, by adding a line selection switch and performing circuit hardware control of the added line selection switch before the DC line is covered with ice, the flexible DC transmission system is compatible with both a normal operating mode and an ice-melting mode. The ice-melting mode can be used before ice is formed or when ice is not severely formed. In this ice-melting mode, DC current will continue to flow into the DC line, and the DC will still maintain bipolar operation in the normal operating mode, thereby maintaining the power transmission to the greatest extent possible, thereby ensuring transmission power while taking into account ice melting. Furthermore, when the DC line is covered with ice, a reference wave is added to the calculation of the valve-side voltage to increase the valve-side voltage, thereby reducing the AC-side current and thereby increasing the DC-side current. This allows the DC line to maintain a high DC current when ice is severely formed, and the severely iced DC line can be melted, thereby achieving the purpose of line ice melting based on the flexible DC transmission system itself without the need for power outages.

[0100] 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.

[0101] The present application also provides an electronic device, Figure 7 The provided electronic device 700 includes a memory 710, a processor 720, and a computer program 711 stored in the memory 710 and capable of running on the processor 720. When the computer program 711 is executed by the processor, the various processes of the above-mentioned embodiment of the line de-icing method based on the flexible direct current transmission system are implemented, and the same technical effects can be achieved. To avoid repetition, they are not described here.

[0102] The present application also provides a computer-readable storage medium. Figure 8 The computer-readable storage medium 800 provided stores a computer program 711. When the computer program 711 is executed by the processor, each process of the above-mentioned embodiment of the line de-icing method based on the flexible direct current transmission system is implemented, and the same technical effect can be achieved. To avoid repetition, it will not be described here.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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)).

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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 line de-icing method based on a flexible direct current transmission system, characterized in that: The flexible DC power 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 and the bus negative pole are respectively provided with two converter valve groups, each converter valve group is connected in parallel with a bypass switch, a line selection switch group is provided between the two converter valve groups located at the same pole in the sending-end converter station, and a line selection switch group is provided between the two converter valve groups located at the same pole in the receiving-end converter station; When the flexible DC power transmission system is in a normal operating mode, the line selection switch group and the bypass switch are controlled, and each converter valve group forms a series circuit with the DC line; when the flexible DC power transmission system is in an ice-melting mode, the line selection switch group and the bypass switch are controlled, and two converter valve groups located at the same pole form a parallel circuit, and the parallel circuit is connected to the DC line; The method comprises: When the DC line is covered with ice, a valve-side current reference value is obtained, a three-phase reference wave is obtained based on the valve-side current reference value, and the three-phase reference wave is superimposed on the original three-phase reference wave to obtain a valve-side voltage; the valve-side voltage is used to indicate the power distribution between the AC side and the DC side.

2. The method according to claim 1, 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.

3. The method 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 each line selection switch group are disconnected, the second switch, the third switch and the fifth switch are closed, and each bypass switch is disconnected. The two converter valve groups located at the same pole in the sending-end converter station are connected in series, and the two converter valve groups located at the same pole in the receiving-end converter station are connected in series. Each converter valve group forms a series loop with the direct current line.

4. The method according to claim 2, characterized in that When the flexible direct current transmission system is in the ice-melting mode, the second switch, the third switch, and the fifth switch of each line selection switch group are opened, the first switch and the fourth switch are closed, and each bypass switch is closed. The two converter valve groups located at the same pole in the sending-end converter station are connected in parallel, and the two converter valve groups located at the same pole in the receiving-end converter station are connected in parallel, and the parallel loop formed by the converter valve groups is connected to the direct current line.

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

6. The method according to claim 1, characterized in that The obtaining of the valve side current reference value includes: Obtaining a DC current reference value, as well as a DC current and an AC current of the flexible DC transmission system during normal operation; The valve-side current reference value is calculated using the DC current reference value, the DC current during normal operation, and the AC current.

7. The method according to claim 1 or 6, characterized in that The obtaining of a three-phase reference wave based on the valve-side current reference value includes: Obtaining a valve-side current measurement value, inputting the valve-side current reference value and the valve-side current measurement value into a proportional-integral controller, and outputting a DC voltage reference value; The valve-side rated voltage is obtained, and the three-phase reference wave is calculated using the DC voltage reference value and the valve-side rated voltage.

8. A conductor ice melting device based on a flexible direct current transmission system, characterized in that: The flexible DC power 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 and the bus negative pole are respectively provided with two converter valve groups, each converter valve group is connected in parallel with a bypass switch, a line selection switch group is provided between the two converter valve groups located at the same pole in the sending-end converter station, and a line selection switch group is provided between the two converter valve groups located at the same pole in the receiving-end converter station; When the flexible DC power transmission system is in a normal operating mode, the line selection switch group and the bypass switch are controlled, and each converter valve group forms a series circuit with the DC line; when the flexible DC power transmission system is in an ice-melting mode, the line selection switch group and the bypass switch are controlled, and two converter valve groups located at the same pole form a parallel circuit, and the parallel circuit is connected to the DC line; The device comprises: A power distribution module is used to obtain a valve-side current reference value when the DC line is covered with ice, obtain a three-phase reference wave based on the valve-side current reference value, and superimpose the three-phase reference wave on the original three-phase reference wave to obtain a valve-side voltage; the valve-side voltage is used to indicate the power distribution between the AC side and the DC side.

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 de-icing method based on a flexible direct current transmission system according to any one of claims 1 to 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 based on a flexible direct current transmission system according to any one of claims 1 to 7 is implemented.

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