Bipolar control right switching method for bipolar multi-terminal DC transmission system

Abstract

The present invention provides a method for switching bipolar control rights in a bipolar multi-terminal direct current (HVDC) transmission system, comprising: step 1) obtaining operating status data of the bipolar multi-terminal direct current (HVDC) transmission system; step 2) determining a master station, a control pole switching mode control word, and a pole status word based on the operating status data; step 3) for the master station, executing step 5) based on the pole status words of the two poles to determine the control pole of the master station; step 4) for non-master stations, determining whether to follow the control pole of the master station or independently determine the control pole based on the control pole switching mode control word; and step 5) comparing the pole status words of the two poles and determining the control pole based on the magnitude of the pole status words. The present invention can achieve coordinated switching of bipolar control rights in the bipolar multi-terminal direct current transmission system, always ensuring that the pole control system that is more suitable for controlling the system realizes the bipolar layer control function, thereby ensuring the safe and stable operation of the bipolar multi-terminal direct current transmission system.

Description

Technical Field

[0001] The present invention belongs to the field of direct current (DC) power transmission, and in particular relates to a bipolar control right switching method for a bipolar multi-terminal DC power transmission system. Background Art

[0002] In recent years, bipolar multi-terminal DC transmission has been a hot research topic in the DC transmission field. Compared to unipolar DC, bipolar DC offers wider applications, doubles transmission capacity, and achieves zero ground current during balanced operation. Compared to two-terminal DC, multi-terminal DC allows for multiple power sources and multiple receiving points. The disconnection of one terminal does not affect power transmission at other terminals, making it more economical, flexible, and well-suited for DC grid interconnection and the integration of renewable energy sources.

[0003] Similar to bipolar two-terminal DC, the bipolar multi-terminal DC control system can be divided into the following layers: AC / DC system layer, regional layer, HVDC bipolar control layer (referred to as the bipolar layer), HVDC pole control layer (referred to as the pole layer), and converter control layer. The bipolar layer's main control functions include bipolar power coordination control, bipolar current balancing control, and station-wide reactive power control. The pole layer's main control functions include pole current / power control, pole start-up and shutdown control, and pole fault handling control.

[0004] There are currently two solutions for implementing the control functions of the bipolar layer and the pole layer: one is an integrated design solution, in which no independent bipolar control host is set up. The bipolar layer and the pole layer share the pole layer control host, and the bipolar layer control functions are integrated into the pole control hosts of the two poles respectively; the other is an independent design solution, in which the bipolar layer and the pole layer control hosts are configured separately, that is, an independent bipolar control host and pole control host are set up, each of which implements the control function of each layer.

[0005] In the integrated design, the bipolar layer control function is implemented in the pole control host. When both poles are in operation, poles 1 and 2 can assume control of the bipolar layer function, which obviously presents a control switching issue. The pole that holds the bipolar layer control function is called the control pole (or dominant pole, master pole), and the other pole is called the non-control pole (or non-dominant pole, non-master pole, follower pole, slave pole). The bipolar layer control function of the non-control pole follows the control pole, and the control pole can switch between the two poles in real time.

[0006] For independent design solutions, it is necessary to consider the practical requirement that "under the special working conditions where both bipolar control host redundant systems are lost, the DC system can still maintain normal operation for a period of time", and there is also the problem of switching bipolar control rights.

[0007] Compared to two-terminal DC transmission systems, multi-terminal DC transmission systems involve more stations, making bipolar control transfer more critical and complex. If not handled properly, this can lead to control conflicts, impacting the safe and stable operation of the entire DC system. Currently, no experts or scholars, both domestically and internationally, have conducted in-depth research on how to achieve bipolar control transfer in bipolar multi-terminal DC transmission systems. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a method for switching bipolar control rights in a bipolar multi-terminal direct current (HVDC) transmission system, which can always ensure that the pole control system that is more suitable for controlling the power system can realize the bipolar layer control function, thereby ensuring the safe and stable operation of the bipolar multi-terminal direct current transmission system. The method has the advantages of convenience, feasibility, safety and reliability.

[0009] The present invention adopts the following technical solutions to solve the above technical problems:

[0010] The present invention provides a method for switching bipolar control rights in a bipolar multi-terminal direct current (DC) transmission system. In the bipolar multi-terminal DC transmission system, one pole is a control pole (or a dominant pole, a master control pole) and the other pole is a non-control pole (or a non-dominant pole, a non-master control pole, a follower pole, or a slave control pole). The bipolar layer control function of the control pole is effective, and the bipolar layer control function of the non-control pole follows the control pole. The bipolar control right switching is switching between the control pole and the non-control pole, and includes:

[0011] Step 1) obtaining operating status data of a bipolar multi-terminal direct current transmission system;

[0012] Step 2) determining the leading station / non-leading station based on the bipolar multi-terminal direct current transmission system operation status data, and generating a control word for a control pole switching mode of each station and a bipolar state word for each station;

[0013] Step 3) For the master station, execute step 5) according to the pole status words of the two poles to determine the control pole of the master station;

[0014] Step 4) For the non-dominant station, determine the control pole switching mode control word: if the joint switching mode is used, the control pole of the non-dominant station follows the control pole of the dominant station; if the independent switching mode is used, the control pole of the non-dominant station is determined independently. Based on the pole state words of the two poles, execute step 5) to determine the control pole of the non-dominant station;

[0015] Step 5) Compare the pole status words of the two poles. If the pole status words are equal, one of the poles is assumed to be the control pole and the other is the non-control pole, or the current control pole state is maintained unchanged. At the same time, the manual switching control pole logic is opened to allow manual switching. If the pole status words are not equal, the pole with the larger pole status word is automatically switched to the control pole, and the pole with the smaller pole status word is automatically switched to the non-control pole. At the same time, the manual switching control pole logic is locked to prohibit manual switching, and an alarm prompt message of "interlocking not satisfied" is provided.

[0016] Furthermore, in step 1), the bipolar multi-terminal direct current transmission system operation status data includes: direct current operation mode, pole operation status, pole operation mode, communication status and pole control host status.

[0017] Furthermore, in step 2), the master station refers to the converter station that dominates the power / current control function of the entire bipolar multi-terminal DC transmission system. In the multi-terminal DC transmission system, there is only one station that serves as the master station, and the other converter stations serve as non-master stations. The rectifier station in operation is selected as the master station. If there are multiple rectifier stations in operation, the converter station with the largest capacity or the one with a compromise electrical distance from other converter stations can be selected to dominate the power / current control function of the entire multi-terminal DC transmission system as the master station.

[0018] Furthermore, in step 2), the control pole switching mode control word has only two modes: a joint switching mode and an independent switching mode, which can be manually selected or automatically generated based on the DC operating mode, pole operating state, pole operating mode and communication state in the bipolar multi-terminal direct current transmission system operating state data.

[0019] Furthermore, in step 2), the pole status word is automatically generated based on the weighted DC operation mode, pole operation state, pole operation mode, communication state and pole control host state in the bipolar multi-terminal DC transmission system operation state data.

[0020] Furthermore, in step 1), the DC operation mode in the bipolar multi-terminal direct current transmission system operation status data includes rectification / inversion, station maintenance, and pole maintenance; the pole operation status includes pole connection / isolation, pole charging / uncharging, and pole unlocking / locking; the pole operation mode includes unipolar current / unipolar power / bipolar power; the communication status includes inter-station communication normal / communication fault and inter-pole communication normal / communication fault; and the pole control host status includes master and standby hosts normal / faulty.

[0021] By adopting the above scheme, the present invention can achieve coordinated switching of bipolar control rights in a bipolar multi-terminal DC transmission system, ensuring that the most suitable control pole control system always performs bipolar layer control functions, thereby ensuring the safe and stable operation of the bipolar multi-terminal DC transmission system. This scheme is applicable not only to bipolar three-terminal, four-terminal, or even multi-terminal bipolar systems, but also to the coordinated switching of bipolar control rights in bipolar two-terminal DC transmission systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a flow chart of the bipolar control right switching method of the present invention;

[0023] Figure 2 This is a flow chart of the status word comparison logic;

[0024] Figure 3 Schematic diagram of a three-terminal DC circuit in Example 1 of the present invention;

[0025] Figure 4 This is a schematic diagram of a two-terminal direct current in Example 2 of the present invention. DETAILED DESCRIPTION

[0026] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.

[0027] The present invention provides a method for switching bipolar control rights of a bipolar multi-terminal direct current transmission system, such as Figure 1 As shown, the method includes: step 1) acquiring operating status data of a bipolar multi-terminal direct current transmission system; step 2) determining a master station, a control pole switching mode control word, and a pole status word according to the operating status data; step 3) for the master station, executing step 5) according to the pole status words of the two poles to determine the control pole of the master station; step 4) for the non-master station, determining whether to follow the control pole of the master station or independently determine the control pole according to the control pole switching mode control word; step 5) comparing the pole status words of the two poles and determining the control pole according to the size of the pole status words.

[0028] Example 1

[0029] This embodiment is a method for switching bipolar control rights during bipolar three-terminal hybrid DC three-terminal operation.

[0030] like Figure 3 As shown, station 1 (S1) and station 2 (S2) are normal DC converter stations, station 3 (S3) is a flexible DC converter station. When the bipolar three-terminal hybrid DC system operates normally, S1 is a rectifier station, and S2 and S3 are inverter stations.

[0031] The present invention provides a method for switching bipolar control rights in a bipolar three-terminal direct current transmission system, comprising:

[0032] Step 1) obtaining operating status data of a bipolar three-terminal direct current transmission system;

[0033] Step 2) determining the leading station / non-leading station based on the bipolar three-terminal direct current transmission system operation status data, and generating a control word for a control pole switching mode of each station and a bipolar state word for each station;

[0034] Step 3) For the master station, execute step 5) according to the pole status words of the two poles to determine the control pole of the master station;

[0035] Step 4) For the non-dominant station, determine the control pole switching mode control word: if the joint switching mode is used, the control pole of the non-dominant station follows the control pole of the dominant station; if the independent switching mode is used, the control pole of the non-dominant station is determined independently. Based on the pole state words of the two poles, execute step 5) to determine the control pole of the non-dominant station;

[0036] Step 5) Figure 2 As shown, the pole status words of the two poles are compared. If the pole status words are equal, one of the poles is defaulted to be the control pole and the other is the non-control pole, or the current control pole state is maintained unchanged. At the same time, the manual switching control pole logic is opened to allow manual switching; if the pole status words are not equal, the pole with the larger pole status word is automatically switched to the control pole, and the pole with the smaller pole status word is automatically switched to the non-control pole. At the same time, the manual switching control pole logic is locked, manual switching is prohibited, and an interlocking failure alarm prompt message is provided.

[0037] Furthermore, in step 1), the operating status data of the bipolar three-terminal direct current transmission system includes: direct current operating mode, pole operating state, pole operating mode, communication state and pole control host state.

[0038] Furthermore, in step 2), when the bipolar three-terminal hybrid DC system operates normally, the rectifier station S1 is selected as the main station.

[0039] Furthermore, in step 2), the control pole switching mode control word has only two modes: combined switching mode and independent switching mode. These can be selected manually or automatically generated based on the DC operating mode, pole operating state, pole operating mode, and communication state in the bipolar three-terminal DC transmission system operating status data. Generally speaking, during normal bipolar three-terminal operation, the control pole switching mode is selected as combined switching mode. If a station is undergoing maintenance, the control pole switching mode can be automatically generated as independent switching mode.

[0040] Furthermore, in the step 2), the pole status word is automatically generated based on the weighted DC operation mode, pole operation state, pole operation mode and communication state and pole control host state in the bipolar three-terminal DC transmission system operation state data.

[0041] Furthermore, in step 1), the DC operation mode in the bipolar three-terminal DC transmission system operation status data includes rectification / inversion, station maintenance, and pole maintenance; the pole operation status includes pole connection / isolation, pole charging / uncharging, and pole unlocking / locking; the pole operation mode includes unipolar current / unipolar power / bipolar power; the communication status includes inter-station communication normal / communication fault and inter-pole communication normal / communication fault; and the pole control host status includes master and standby hosts normal / faulty.

[0042] After adopting the above solution, the present invention can realize the coordinated switching of bipolar control rights of the bipolar three-terminal direct current transmission system, and always ensure that the pole control system that is more suitable for controlling the function realizes the bipolar layer control function.

[0043] Example 2

[0044] This embodiment is a method for switching bipolar control rights of a bipolar DC at both ends of a bipolar region.

[0045] like Figure 4As shown in the figure, during normal operation of a bipolar two-terminal DC transmission, S1 is the rectifier station and S2 is the inverter station. In a two-terminal DC transmission, the rectifier station is generally the dominant station, and the control pole switching mode control word is manually set to joint switching mode.

[0046] The present invention provides a method for switching bipolar control rights in a bipolar two-terminal direct current transmission system, comprising:

[0047] Step 1) obtaining operating status data of a bipolar two-terminal DC transmission system;

[0048] Step 2) determining the two-pole status words of the two stations according to the operating status data of the bipolar two-terminal DC transmission system;

[0049] Step 3) For the master station S1, execute step 5) according to the pole status words of the two poles to determine the control pole of the master station;

[0050] Step 4) For the non-leading station S2, the control pole switching mode control word is the joint switching mode, and the control pole of S2 follows the control pole of S1;

[0051] Step 5) Figure 2 As shown, the pole status words of the two poles are compared. If the pole status words are equal, one of the poles is defaulted to be the control pole and the other is the non-control pole, or the current control pole state is maintained unchanged. At the same time, the manual switching control pole logic is opened to allow manual switching; if the pole status words are not equal, the pole with the larger pole status word is automatically switched to the control pole, and the pole with the smaller pole status word is automatically switched to the non-control pole. At the same time, the manual switching control pole logic is locked, manual switching is prohibited, and an interlocking failure alarm prompt message is provided.

[0052] Furthermore, in step 1), the operating status data of the bipolar two-terminal DC transmission system includes: DC operating mode, pole operating state, pole operating mode, communication state and pole control host state.

[0053] Furthermore, in the step 2), the pole status word is automatically generated based on the weighted DC operation mode, pole operation state, pole operation mode and communication state and pole control host state in the bipolar two-terminal DC transmission system operation state data.

[0054] Furthermore, in step 1), the DC operation mode in the operation status data of the bipolar two-terminal DC transmission system includes pole maintenance, the pole operation status includes pole connection / isolation, pole charging / uncharging, and pole unlocking / locking, the pole operation mode includes unipolar current / unipolar power / bipolar power, the communication status includes inter-station communication normal / communication fault, and inter-pole communication normal / communication fault, and the pole control host status includes master and standby hosts normal / faulty.

[0055] The above embodiments are only for illustrating the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for switching bipolar control rights in a bipolar multi-terminal direct current (HVDC) system, wherein one pole in the bipolar multi-terminal direct current (HVDC) system is a control pole and the other pole is a non-control pole, the bipolar layer control function of the control pole is effective, and the bipolar layer control function of the non-control pole follows the control pole, and the switching of bipolar control rights is switching between the control pole and the non-control pole, characterized in that: The switching method includes the following steps: Step 1) obtaining operating status data of a bipolar multi-terminal direct current transmission system; Step 2) determining the leading station and non-leading station in all converter stations according to the operating status data of the bipolar multi-terminal direct current transmission system, and generating a control word for a control pole switching mode of each station and a two-pole state word of each station; Step 3) For the master station, execute step 5) according to its two-pole status word to determine the control pole of the master station; Step 4) For the non-leading station, if its gate switching mode control word is the joint switching mode, the gate of the non-leading station follows the gate of the leading station; If it is an independent switching mode, the control pole of the non-leading station is determined independently, and according to its two-pole state word, step 5) is executed to determine the control pole of the non-leading station; Step 5) Compare the two pole status words. If the pole status words are equal, one of the poles is selected as the control pole and the other as the non-control pole, or the current control pole state is maintained unchanged. At the same time, the manual switching control pole logic is enabled to allow manual switching. If the pole status words are not equal, the pole with the larger pole status word is automatically switched to the control pole, and the pole with the smaller pole status word is automatically switched to the non-control pole. At the same time, the manual switching control pole logic is locked to prohibit manual switching, and an "interlocking failure" alarm prompt message is provided.

2. The method for switching bipolar control rights in a bipolar multi-terminal direct current transmission system according to claim 1, wherein: In the step 1), the operating status data of the bipolar multi-terminal direct current transmission system includes: direct current operating mode, pole operating state, pole operating mode, communication state and pole control host state.

3. The method for switching bipolar control rights in a bipolar multi-terminal direct current transmission system according to claim 1, wherein: In step 2), the master station refers to the converter station that controls the power / current control function of the entire bipolar multi-terminal direct current transmission system. In the multi-terminal direct current transmission system, there is only one converter station that serves as the master station, and the other converter stations serve as non-master stations.

4. The method for switching bipolar control rights in a bipolar multi-terminal direct current transmission system according to claim 3, wherein: Select the rectifier station in operation as the leading station. If there are multiple rectifier stations in operation, select the rectifier station with the largest capacity as the leading station. If the capacities of the rectifier stations in operation are equal, the rectifier station with the best electrical distance from other converter stations is selected as the lead station.

5. The method for switching bipolar control rights in a bipolar multi-terminal direct current transmission system according to claim 1, wherein: In the step 2), the gate switching mode control word has only two modes: a joint switching mode and an independent switching mode.

6. The method for switching bipolar control rights in a bipolar multi-terminal direct current transmission system according to claim 5, wherein: The two modes are selected manually or automatically generated according to the DC operation mode, pole operation state, pole operation mode and communication state in the operation state data of the bipolar multi-terminal DC transmission system.

7. The method for switching bipolar control rights in a bipolar multi-terminal direct current transmission system according to claim 1, wherein: In the step 2), the pole status word is automatically generated based on the weighted DC operation mode, pole operation state, pole operation mode, communication state and pole control host state in the bipolar multi-terminal DC transmission system operation state data.

8. The method for switching bipolar control rights in a bipolar multi-terminal direct current transmission system according to claim 2, wherein: The DC operation mode includes rectification / inversion, station maintenance, and pole maintenance; the pole operation status includes pole connection / isolation, pole charging / uncharging, and pole unlocking / locking; the pole operation mode includes unipolar current / unipolar power / bipolar power; the communication status includes inter-station communication normal / communication fault, inter-pole communication normal / communication fault; and the pole control host status includes main and standby hosts normal / faulty.

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