Online input method, device and equipment of multi-terminal flexible direct current system and storage medium

Abstract

The invention discloses an online input method, device and equipment for a multi-terminal flexible direct current system and a storage medium, and the method comprises the steps: carrying out the uncontrollable charging of an in-terminal converter valve through an alternating current power supply, so as to enable the voltage of a bridge arm sub-module to be increased, and carrying out the controllable charging of the in-terminal converter valve when the voltage of the bridge arm sub-module is increased to an uncontrollable charging voltage, and when the voltage of the bridge arm sub-module rises to a controllable charging voltage not lower than a preset value, the in-end converter valve is locked, and all the direct-current isolation switches in the end are closed in a target time window after locking, so that the voltage of the bridge arm sub-module continues to rise, and when the voltage of the bridge arm capacitor of the in-end converter valve rises to a controllable charging voltage not lower than the preset value, the in-end converter valve is closed. The target time window is a time window when the voltage of the sub-module of the bridge arm is reduced from the controllable charging voltage to the target voltage. The operation of closing the direct-current switch is completed in the target time window, and the direct-current switch does not need to flow through current, so that only a common direct-current switch can be adopted, an HSS or a direct-current circuit breaker does not need to be adopted, and the occupied area and cost of equipment are saved.

Description

Technical Field

[0001] This application relates to the field of DC power transmission technology, and more specifically, to a method, apparatus, equipment, and storage medium for online connection of a multi-terminal flexible DC system. Background Technology

[0002] With the development of DC transmission technology, existing multi-terminal flexible DC systems typically install high-speed DC parallel switches (HSS) or DC circuit breakers to enable online connection and disconnection of the converter terminals.

[0003] Currently, some multi-terminal DC projects use high-speed DC parallel switches to achieve online deparallel operation and rapid isolation after DC line faults. For example, by installing DC circuit breakers, fault current interruption and converter terminal switching operations during normal operation can be achieved.

[0004] However, enabling the switching on and off of the converter during normal operation using HSS or DC circuit breakers requires additional equipment, resulting in a large footprint and increased costs.

[0005] How to enable the converter end of a multi-terminal flexible DC system to be put into operation under non-DC fault conditions and using only ordinary DC disconnect switches is an issue that needs attention. Summary of the Invention

[0006] In view of the above problems, this application provides an online connection method, apparatus, equipment and storage medium for a multi-terminal flexible DC system, so as to realize the connection of the converter end of the multi-terminal flexible DC system using only ordinary DC disconnect switches under non-DC fault conditions.

[0007] To achieve the above objectives, the following specific solutions are proposed:

[0008] A method for online commissioning of a multi-terminal flexible DC system, wherein the multi-terminal flexible DC system includes at least two continuously operating converter terminals and a target converter terminal to be commissioned, wherein the AC side of the target converter terminal is connected to a corresponding AC power supply through an AC circuit breaker, and the positive and negative lines of the DC side of the target converter terminal are connected in parallel with the DC sides of other converter terminals through corresponding DC disconnect switches, and the method is applied to the target converter terminal.

[0009] The method includes:

[0010] The AC power supply of the target converter terminal is used to uncontrollably charge the in-terminal converter valve of the target converter terminal, so as to increase the voltage of the sub-module of the bridge arm of the in-terminal converter valve.

[0011] When the voltage of the sub-module of the bridge arm of the internal converter valve rises to the uncontrolled charging voltage, the internal converter valve is controlled to charge so that the voltage of the sub-module of the bridge arm of the internal converter valve continues to rise.

[0012] When the capacitor voltage of the bridge arm of the internal converter valve rises to a controllable charging voltage not lower than a preset value, the internal converter valve is locked.

[0013] Within the target time window after the lockout, all DC disconnect switches in the target converter terminal are closed to put the target converter terminal into operation. The target time window is the time window during which the voltage of the sub-module of the bridge arm drops from the controllable charging voltage to the target voltage.

[0014] Optionally, the method further includes:

[0015] When the capacitor voltage of the bridge arm of the internal converter valve rises to a controllable charging voltage not lower than a preset value, a command to close all DC isolation switches is issued.

[0016] Within the target time window, in response to the command to close all DC disconnect switches, all DC disconnect switches are closed, and during the process of closing all DC disconnect switches, the intra-terminal converter valve is locked.

[0017] Optionally, the target voltage is:

[0018]

[0019] in, This is the DC terminal voltage to ground at the normal operating terminal. The peak value of the AC side voltage relative to ground at the target converter terminal is denoted as .

[0020] Optionally, the target time window is:

[0021]

[0022] in, The duration of the target time window. The bridge arm discharge time constant of the in-terminal converter valve is given. This is the preset value of the controllable charging voltage. This is the DC inter-electrode voltage at the normal operating terminal.

[0023] Optionally, the target time window is:

[0024]

[0025] in, The duration of the target time window. The bridge arm discharge time constant of the in-terminal converter valve is given. This is the preset value of the controllable charging voltage. This is the DC inter-electrode voltage at the normal operating terminal. The bridge arm voltage withstand value in minutes for the internal converter valve is specified.

[0026] Optionally, the method further includes:

[0027] When the target time window is greater than the first time window threshold, all DC disconnect switches are closed after the intra-terminal converter valve is locked within the target time window. The first time window threshold is:

[0028]

[0029] in, The time from the issuance of the closing command for the DC disconnect switch until the DC disconnect switch is fully closed. The time from issuing the lockout command for the internal converter valve to issuing the closing command for the DC disconnect switch.

[0030] Optionally, the method further includes:

[0031] When the target time window is greater than the second time window threshold, all DC disconnect switches are closed within the target time window, and during the process of closing all DC disconnect switches, the in-terminal converter valve is locked. The second time window threshold is:

[0032]

[0033] in, The time from the issuance of the closing command for the DC disconnect switch until the DC disconnect switch is fully closed. The time from the issuance of the closing command of the DC disconnect switch until the internal converter valve is locked.

[0034] An online connection device for a multi-terminal flexible DC system, the multi-terminal flexible DC system including at least two continuously operating converter terminals and a target converter terminal to be connected, the AC side of the target converter terminal is connected to the corresponding AC power supply through an AC circuit breaker, and the positive and negative lines of the DC side of the target converter terminal are connected in parallel with the DC sides of other converter terminals through corresponding DC disconnect switches, and the device is applied to the target converter terminal;

[0035] The device includes:

[0036] An uncontrollable charging unit is used to uncontrollably charge the in-terminal converter valve of the target converter terminal through the AC power supply of the target converter terminal, so as to increase the voltage of the sub-module of the bridge arm of the in-terminal converter valve.

[0037] A controllable charging unit is used to controllably charge the internal converter valve when the voltage of the sub-module of the bridge arm of the internal converter valve rises to the uncontrolled charging voltage, so that the voltage of the sub-module of the bridge arm of the internal converter valve continues to rise.

[0038] The locking unit locks the internal converter valve when the capacitor voltage of the bridge arm of the internal converter valve rises to a controllable charging voltage not lower than a preset value.

[0039] The DC disconnect switch closing unit is used to close all DC disconnect switches in the target converter terminal within the target time window after locking, so as to put the target converter terminal into operation. The target time window is the time window during which the voltage of the sub-module of the bridge arm drops from the controllable charging voltage to the target voltage.

[0040] Optionally, the device may also include:

[0041] The DC disconnect switch closing command issuing unit is used to issue a command to close all DC disconnect switches when the capacitor voltage of the bridge arm of the internal converter valve rises to a controllable charging voltage not lower than a preset value.

[0042] An in-terminal converter valve locking unit is used to close all DC disconnect switches in response to the command to close all DC disconnect switches within the target time window, and to lock the in-terminal converter valve during the process of closing all DC disconnect switches.

[0043] Optionally, the device may also include:

[0044] The post-closing switch unit is used to close all DC disconnect switches after locking the in-terminal converter valve within the target time window when the target time window is greater than a first time window threshold. The first time window threshold is:

[0045]

[0046] in, The time from the issuance of the closing command for the DC disconnect switch until the DC disconnect switch is fully closed. The time from issuing the lockout command for the internal converter valve to issuing the closing command for the DC disconnect switch.

[0047] Optionally, the device may also include:

[0048] The post-locking converter valve unit is used to close all DC disconnect switches within the target time window when the target time window is greater than a second time window threshold, and to lock the in-terminal converter valve during the closing of all DC disconnect switches. The second time window threshold is:

[0049]

[0050] in, The time from the issuance of the closing command for the DC disconnect switch until the DC disconnect switch is fully closed. The time from the issuance of the closing command of the DC disconnect switch until the internal converter valve is locked.

[0051] An online connection device for a multi-terminal flexible DC system includes a memory and a processor;

[0052] The memory is used to store programs;

[0053] The processor is used to execute the program to implement the various steps of the online commissioning method for the multi-terminal flexible DC system as described above.

[0054] A storage medium storing a computer program, which, when executed by a processor, implements the various steps of the online connection method for a multi-terminal flexible DC system as described above.

[0055] Using the above technical solution, this application uses the AC power supply of the target converter terminal to uncontrollably charge the internal converter valve of the target converter terminal, thereby increasing the voltage of the sub-module of the bridge arm of the internal converter valve. When the voltage of the sub-module of the bridge arm of the internal converter valve reaches the uncontrollable charging voltage, the internal converter valve is controlled to continue charging, so that the voltage of the sub-module of the bridge arm of the internal converter valve continues to increase. When the capacitor voltage of the bridge arm of the internal converter valve rises to a controllable charging voltage not lower than a preset rated value, the internal converter valve is locked. Within the target time window after locking, all DC disconnect switches in the target converter terminal are closed to put the target converter terminal into operation. The target time window is the time window during which the voltage of the sub-module of the bridge arm drops from the controllable charging voltage to the target voltage. The operation of closing the DC switches is completed within the target time window, and the DC switches do not need to carry current. Therefore, only ordinary DC switches can be used, without the need for HSS or DC circuit breakers, saving equipment space and cost. Attached Figure Description

[0056] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0057] Figure 1 A topology diagram of a multi-terminal flexible DC system provided in an embodiment of this application;

[0058] Figure 2 A topology circuit diagram of the converter terminal of a multi-terminal flexible DC system provided in an embodiment of this application;

[0059] Figure 3 A schematic diagram illustrating the process of online commissioning of the converter terminal of a multi-terminal flexible DC system provided in an embodiment of this application;

[0060] Figure 4 A schematic diagram of an online connection device for realizing a multi-terminal flexible DC system is provided in an embodiment of this application;

[0061] Figure 5 This is a schematic diagram of a device for online commissioning of a multi-terminal flexible DC system, provided as an embodiment of this application. Detailed Implementation

[0062] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0063] This application provides a circuit topology for realizing online commissioning of a multi-terminal flexible DC system. The topology may include at least two continuously operating converter terminals and at least one target converter terminal to be commissioned.

[0064] The AC side of the target converter is connected to the corresponding AC power supply through an AC circuit breaker, and the positive and negative lines of the DC side of the target converter are connected in parallel with the DC side of other converters through corresponding DC disconnect switches.

[0065] like Figure 1As shown in the figure, the topology includes two continuously operating converter terminals and one converter terminal to be put into operation. The two continuously operating converter terminals are designated as Terminal 1 and Terminal 2, respectively, and the converter terminal to be put into operation is designated as Terminal 3. The AC sides of all three converter terminals are connected to their respective AC power supplies via AC circuit breakers. The positive and negative DC lines of the three converter terminals are connected in parallel with the DC sides of the other converter terminals via their respective DC disconnect switches.

[0066] The circuit topology of each converter terminal can be as follows: Figure 2 As shown, the converter terminal may include a flexible DC converter valve, a transformer, an AC circuit breaker, and two DC disconnect switches. Each arm of the flexible DC converter valve contains multiple power submodules, each containing capacitors and resistors. Each capacitor in each arm can be considered equivalent to the equivalent capacitance of that arm, and each resistor in each arm can be considered equivalent to the equivalent resistance of that arm. The DC disconnect switches are used for online connection of the converter terminal. The two DC disconnect switches at the converter terminal are located on the positive and negative lines, respectively.

[0067] Figure 2 U in d U represents the DC inter-electrode voltage, BR represents the bridge arm reactor, C represents the equivalent capacitance of the bridge arm submodule, R represents the equivalent resistance of the bridge arm, and U represents the DC inter-electrode voltage. c This represents the capacitance value of the equivalent capacitance of the bridge arm.

[0068] Based on this Figure 3 This paper illustrates a flowchart of a method for online commissioning of a target converter terminal in a multi-terminal flexible DC system according to an embodiment of this application. (Refer to...) Figure 3 The process may include:

[0069] Step S110: Uncontrollably charge the in-terminal converter valve of the target converter terminal using the AC power supply of the target converter terminal, so as to increase the voltage of the sub-module of the bridge arm of the in-terminal converter valve.

[0070] Understandably, when the DC disconnect switch is in the open position, the voltage of the target converter side pole bus depends on the AC voltage. When the converter is locked, the DC pole bus voltage is lower than the operating end pole-to-ground voltage (rated DC voltage). When the disconnect switch is in the closed position, the target converter end pole-to-ground voltage is equal to the operating end pole-to-ground voltage, i.e., 0.5U. d and -0.5U dAfter closing the two DC disconnect switches, whether the intra-terminal converter valve at the target converter end can be charged depends on the bridge arm capacitor voltage. When the voltage difference between the positive terminal to ground and the AC side to ground voltage of the flexible DC converter valve is greater than the bridge arm capacitor voltage, the upper bridge arm capacitor is ready to be charged. When the voltage difference between the AC side to ground voltage of the flexible DC converter valve and the negative terminal to ground voltage is greater than the bridge arm capacitor voltage, the lower bridge arm capacitor is ready to be charged.

[0071] The target voltage can be the sum of the voltage between the operating terminal line and ground and the peak value of the voltage between the valve's AC side and ground. Specifically, it can be:

[0072]

[0073] in, This represents the DC voltage to ground at the normal operation terminal, which indicates whether the converter terminal is currently in operation or continuously operating. The peak value of the AC side voltage relative to ground at the target converter terminal valve.

[0074] It is understandable that when the capacitor voltage of the bridge arm of the converter valve at the target converter end is not less than At this time, the internal converter valve cannot be charged. If the target converter terminal can be connected in parallel within this time (DC disconnect switch closed), no significant current will flow through the DC disconnect switch. When the capacitor voltage of the bridge arm is greater than At this time, the internal converter valve will be charged, and after the two DC disconnect switches on the pole line are closed, current will flow through the DC disconnect switches. Therefore, as long as the capacitor voltage U of the bridge arm is locked after the internal converter valve is closed... c Controllable charging voltage U cx Down to If the DC disconnect switch on the pole line is closed within the specified time window, no current will flow through the DC disconnect switch.

[0075] Furthermore, when uncontrolled charging is complete, the peak voltage relative to ground on the AC side of the target commutator can be... The DC pole-to-ground voltage of the target converter terminal is 0.5. The DC inter-electrode voltage at the target commutator is The capacitor voltage of the bridge arm at the target commutator is .

[0076] Step S120: When the voltage of the sub-module of the bridge arm of the internal converter valve rises to the uncontrolled charging voltage, the internal converter valve is controlled to continue to rise.

[0077] Specifically, the uncontrolled charging voltage can represent the voltage at which uncontrolled charging is completed, and it is a fixed value.

[0078] When controlled charging is complete, the peak voltage relative to ground on the AC side of the valve at the target converter terminal can be... The DC pole-to-ground voltage of the target converter terminal is 0.5. The DC inter-electrode voltage at the target commutator is The capacitor voltage of the bridge arm at the target converter terminal is greater than Controllable charging voltage U cx The DC voltage to ground at the operating terminal is 0.5U. d The DC inter-electrode voltage at the operating terminal is U. d .

[0079] Step S130: When the capacitor voltage of the bridge arm of the internal converter valve rises to a controllable charging voltage not lower than a preset value, the internal converter valve is locked.

[0080] Specifically, when the flexible DC converter valve in the target converter terminal is locked, the peak voltage relative to ground on the AC side of the valve at the target converter terminal can be... The DC pole-to-ground voltage of the target converter terminal is 0.5. The DC inter-electrode voltage at the target commutator is The capacitor voltage of the bridge arm at the target converter terminal is greater than Controllable charging voltage U cx The voltage gradually decreases, and the DC terminal voltage to ground at the operating end is 0.5U. d The DC inter-electrode voltage at the operating terminal is U. d .

[0081] Step S140: Within the target time window after the lockout, complete the closing of all DC disconnect switches in the target converter terminal so that the target converter terminal can be put into operation.

[0082] The target time window can represent the time window during which the voltage of the submodule of the bridge arm drops from the controllable charging voltage to the target voltage.

[0083] Specifically, when both DC disconnect switches are closed, the peak voltage relative to ground on the AC side of the valve at the target converter terminal can be... The DC pole-to-ground voltage of the target converter terminal is 0.5U. d The DC inter-electrode voltage at the target commutator is U. d The capacitor voltage of the bridge arm at the target converter terminal continues to decrease, and the DC-to-ground voltage at the operating terminal is 0.5U. d The DC inter-electrode voltage at the operating terminal is U. d .

[0084] It is understandable that the DC disconnect switch can be a regular DC disconnect switch. If the operation of closing the DC disconnect switch is completed within the target time window, then a regular DC disconnect switch can be used for the online connection operation of the converter terminal. However, after the target time window, it may not be possible to disconnect the target converter terminal using only a regular DC disconnect switch.

[0085] In addition, the online commissioning method for the multi-terminal flexible DC system provided in this application may also include another scheme for locking the internal converter valve. Specifically, after the capacitor voltage of the bridge arm of the internal converter valve rises to a controllable charging voltage not lower than a preset value, a command to close all DC disconnect switches can be issued. Within the target time window, in response to the command, all DC disconnect switches are closed, and the internal converter valve is locked during the process of closing all DC disconnect switches.

[0086] The online commissioning method for a multi-terminal flexible DC system provided in this application involves uncontrolled charging of the internal converter valve at the target converter terminal by the AC power supply, thereby increasing the voltage of the sub-modules of the bridge arm of the internal converter valve. When the voltage of the sub-modules of the bridge arm reaches the uncontrolled charging voltage, controlled charging is then applied to the internal converter valve to further increase the voltage of the sub-modules. When the capacitor voltage of the bridge arm reaches a controlled charging voltage not lower than a preset value, the internal converter valve is locked. Within a target time window after locking, all DC disconnect switches within the target converter terminal are closed to put the target converter terminal into operation. The target time window is the time window during which the voltage of the sub-modules of the bridge arm drops from the controlled charging voltage to the target voltage. Since the DC switch closing operation is completed within the target time window, no current flows through the DC switch. Therefore, only ordinary DC switches can be used, eliminating the need for HSS or DC circuit breakers, thus saving equipment space and cost.

[0087] In some embodiments of this application, the target time window mentioned in the above embodiments is described. The target time window may include the following two cases.

[0088] The first target time window is:

[0089]

[0090] in, The duration of the target time window. The discharge time constant of the bridge arm of the internal converter valve is [value]. This is the preset value for the controllable charging voltage. This is the DC inter-electrode voltage at the normal operating terminal.

[0091] The second target time window is:

[0092]

[0093] in, The duration of the target time window. The discharge time constant of the bridge arm of the internal converter valve is [value]. This is the preset value for the controllable charging voltage. This is the DC inter-electrode voltage at the normal operating terminal. This refers to the minute-level withstand value of the bridge arm voltage of the internal converter valve.

[0094] Understandably, when The larger the time window The longer it is, the easier it is to complete the operation of closing the switch.

[0095] In some embodiments of this application, the constraints of the target time window mentioned in the above embodiments are described, wherein the target time window may be greater than the first time window threshold.

[0096] Specifically, the threshold for the first time window can be:

[0097]

[0098] in, This refers to the time from issuing the closing command for the DC disconnect switch until the DC disconnect switch is fully closed. The time from issuing the lockout command for the flexible DC converter valve to issuing the closing command for the DC disconnect switch is defined as follows: It can be in the millisecond range or equal to 0.

[0099] Understandably, when the target time window exceeds the first time window threshold, all DC disconnect switches can be closed after locking the in-terminal converter valve at the target converter end within the target time window. When the value equals 0, the internal converter valve at the target converter terminal is locked, and all DC disconnect switches are closed simultaneously. When the value is greater than 0, all DC disconnect switches are closed after the in-terminal converter valve of the target converter terminal is locked.

[0100] In addition, the target time window mentioned in the above embodiments can also be larger than the second time window threshold. Specifically, the second time window threshold can be:

[0101]

[0102] in, This refers to the time from issuing the closing command for the DC disconnect switch until the DC disconnect switch is fully closed. This refers to the time from issuing the closing command of the DC disconnect switch to the time until the internal converter valve is locked.

[0103] in, The maximum value calculation method is as follows: Calculate the voltage between the closed and open ends of the DC disconnect switch (0.5). -0.5 Calculate the corresponding insulation gap size D. Based on the DC disconnect switch's break length and travel time, calculate the time required for the DC disconnect switch to transition from the open state to a break gap of D. This time is the insulation gap size D. The maximum value.

[0104] It is understandable that when the target time window is greater than the second time window threshold, all DC disconnect switches of the target converter end can be closed within the target time window, and the in-terminal converter valve of the target converter end can be locked during the process of closing all DC disconnect switches.

[0105] The following describes the online connection device for realizing a multi-terminal flexible DC system provided in the embodiments of this application. The online connection device for realizing a multi-terminal flexible DC system described below can be referred to in correspondence with the online connection method for realizing a multi-terminal flexible DC system described above.

[0106] See Figure 4 , Figure 4 This is a schematic diagram of a device structure for realizing the online commissioning of a multi-terminal flexible DC system, as disclosed in an embodiment of this application.

[0107] like Figure 4 As shown, the device may include:

[0108] An uncontrollable charging unit is used to uncontrollably charge the in-terminal converter valve of the target converter terminal through the AC power supply of the target converter terminal, so as to increase the voltage of the sub-module of the bridge arm of the in-terminal converter valve.

[0109] A controllable charging unit is used to controllably charge the internal converter valve when the voltage of the sub-module of the bridge arm of the internal converter valve rises to the uncontrolled charging voltage, so that the voltage of the sub-module of the bridge arm of the internal converter valve continues to rise.

[0110] The locking unit locks the internal converter valve when the capacitor voltage of the bridge arm of the internal converter valve rises to a controllable charging voltage not lower than a preset value.

[0111] The DC disconnect switch closing unit is used to close all DC disconnect switches in the target converter terminal within the target time window after locking, so as to put the target converter terminal into operation. The target time window is the time window during which the voltage of the sub-module of the bridge arm drops from the controllable charging voltage to the target voltage.

[0112] Optionally, the device may also include:

[0113] The DC disconnect switch closing command issuing unit is used to issue a command to close all DC disconnect switches when the capacitor voltage of the bridge arm of the internal converter valve rises to a controllable charging voltage not lower than a preset value.

[0114] An in-terminal converter valve locking unit is used to close all DC disconnect switches in response to the command to close all DC disconnect switches within the target time window, and to lock the in-terminal converter valve during the process of closing all DC disconnect switches.

[0115] Optionally, the target voltage is:

[0116]

[0117] in, This is the DC terminal voltage to ground at the normal operating terminal. The peak value of the AC side voltage relative to ground at the target converter terminal is denoted as .

[0118] Optionally, the target time window is:

[0119]

[0120] in, The duration of the target time window. The bridge arm discharge time constant of the in-terminal converter valve is given. This is the preset value of the controllable charging voltage. This is the DC inter-electrode voltage at the normal operating terminal.

[0121] Optionally, the target time window is:

[0122]

[0123] in, The duration of the target time window. The bridge arm discharge time constant of the in-terminal converter valve is given. This is the preset value of the controllable charging voltage. This is the DC inter-electrode voltage at the normal operating terminal. The bridge arm voltage withstand value in minutes for the internal converter valve is specified.

[0124] Optionally, the device may also include:

[0125] The post-closing switch unit is used to close all DC disconnect switches after locking the in-terminal converter valve within the target time window when the target time window is greater than a first time window threshold. The first time window threshold is:

[0126]

[0127] in, The time from the issuance of the closing command for the DC disconnect switch until the DC disconnect switch is fully closed. The time from issuing the lockout command for the internal converter valve to issuing the closing command for the DC disconnect switch.

[0128] Optionally, the device may also include:

[0129] The post-locking converter valve unit is used to close all DC disconnect switches within the target time window when the target time window is greater than a second time window threshold, and to lock the in-terminal converter valve during the closing of all DC disconnect switches. The second time window threshold is:

[0130]

[0131] in, The time from the issuance of the closing command for the DC disconnect switch until the DC disconnect switch is fully closed. The time from the issuance of the closing command of the DC disconnect switch until the internal converter valve is locked.

[0132] The online connection device for multi-terminal flexible DC systems provided in this application embodiment can be applied to online connection equipment for multi-terminal flexible DC systems, such as terminals like mobile phones and computers. Optionally, Figure 5 The hardware structure block diagram of the online connection equipment for a multi-terminal flexible DC system is shown. (Refer to...) Figure 5 The hardware structure of the online input device for a multi-terminal flexible DC system may include: at least one processor 1, at least one communication interface 2, at least one memory 3, and at least one communication bus 4.

[0133] In this embodiment of the application, the number of processor 1, communication interface 2, memory 3, and communication bus 4 is at least one, and processor 1, communication interface 2, and memory 3 communicate with each other through communication bus 4;

[0134] Processor 1 may be a central processing unit (CPU), an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement embodiments of the present invention.

[0135] Memory 3 may include high-speed RAM, and may also include non-volatile memory, such as at least one disk storage device;

[0136] The memory stores a program, which the processor can call. The program is used for:

[0137] The AC power supply of the target converter terminal is used to uncontrollably charge the in-terminal converter valve of the target converter terminal, so as to increase the voltage of the sub-module of the bridge arm of the in-terminal converter valve.

[0138] When the voltage of the sub-module of the bridge arm of the internal converter valve rises to the uncontrolled charging voltage, the internal converter valve is controlled to charge so that the voltage of the sub-module of the bridge arm of the internal converter valve continues to rise.

[0139] When the capacitor voltage of the bridge arm of the internal converter valve rises to a controllable charging voltage not lower than a preset value, the internal converter valve is locked.

[0140] Within the target time window after the lockout, all DC disconnect switches in the target converter terminal are closed to put the target converter terminal into operation. The target time window is the time window during which the voltage of the sub-module of the bridge arm drops from the controllable charging voltage to the target voltage.

[0141] Optionally, the refined and extended functions of the program can be found in the description above.

[0142] This application embodiment also provides a storage medium that can store a program suitable for execution by a processor, the program being used for:

[0143] The AC power supply of the target converter terminal is used to uncontrollably charge the in-terminal converter valve of the target converter terminal, so as to increase the voltage of the sub-module of the bridge arm of the in-terminal converter valve.

[0144] When the voltage of the sub-module of the bridge arm of the internal converter valve rises to the uncontrolled charging voltage, the internal converter valve is controlled to charge so that the voltage of the sub-module of the bridge arm of the internal converter valve continues to rise.

[0145] When the capacitor voltage of the bridge arm of the internal converter valve rises to a controllable charging voltage not lower than a preset value, the internal converter valve is locked.

[0146] Within the target time window after the lockout, all DC disconnect switches in the target converter terminal are closed to put the target converter terminal into operation. The target time window is the time window during which the voltage of the sub-module of the bridge arm drops from the controllable charging voltage to the target voltage.

[0147] Optionally, the refined and extended functions of the program can be found in the description above.

[0148] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0149] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The various embodiments can be combined as needed, and the same or similar parts can be referred to each other.

[0150] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for online connection of a multi-terminal flexible DC system, characterized in that, The multi-terminal flexible DC system includes at least two continuously operating converter terminals and a target converter terminal to be put into operation. The AC side of the target converter terminal is connected to the corresponding AC power supply through an AC circuit breaker. The positive and negative lines of the DC side of the target converter terminal are connected in parallel with the DC sides of other converter terminals through corresponding DC isolation switches. The method is applied to the target converter terminal. The method includes: The AC power supply of the target converter terminal is used to uncontrollably charge the in-terminal converter valve of the target converter terminal, so as to increase the voltage of the sub-module of the bridge arm of the in-terminal converter valve. When the voltage of the sub-module of the bridge arm of the internal converter valve rises to the uncontrolled charging voltage, the internal converter valve is controlled to charge so that the voltage of the sub-module of the bridge arm of the internal converter valve continues to rise. When the capacitor voltage of the bridge arm of the internal converter valve rises to a controllable charging voltage not lower than a preset value, the internal converter valve is locked. Within the target time window after the lockout, all DC disconnect switches in the target converter terminal are closed to put the target converter terminal into operation. The target time window is the time window during which the voltage of the sub-module of the bridge arm drops from the controllable charging voltage to the target voltage.

2. The method according to claim 1, characterized in that, Also includes: When the capacitor voltage of the bridge arm of the internal converter valve rises to a controllable charging voltage not lower than a preset value, a command to close all DC isolation switches is issued. Within the target time window, in response to the command to close all DC disconnect switches, all DC disconnect switches are closed, and during the process of closing all DC disconnect switches, the intra-terminal converter valve is locked.

3. The method according to claim 1, characterized in that, The target voltage is: in, This is the DC terminal voltage to ground at the normal operating terminal. The peak value of the AC side voltage relative to ground at the target converter terminal is denoted as .

4. The method according to claim 3, characterized in that, The target time window is: in, The duration of the target time window. The bridge arm discharge time constant of the in-terminal converter valve is given. This is the preset value of the controllable charging voltage. This is the DC inter-electrode voltage at the normal operating terminal.

5. The method according to claim 3, characterized in that, The target time window is: in, The duration of the target time window. The bridge arm discharge time constant of the in-terminal converter valve is given. This is the preset value of the controllable charging voltage. This is the DC inter-electrode voltage at the normal operating terminal. The bridge arm voltage withstand value in minutes for the internal converter valve is specified.

6. The method according to claim 1, characterized in that, Also includes: When the target time window is greater than the first time window threshold, all DC disconnect switches are closed after the intra-terminal converter valve is locked within the target time window. The first time window threshold is: in, The time from the issuance of the closing command for the DC disconnect switch until the DC disconnect switch is fully closed. The time from issuing the lockout command for the internal converter valve to issuing the closing command for the DC disconnect switch.

7. The method according to claim 2, characterized in that, Also includes: When the target time window is greater than the second time window threshold, all DC disconnect switches are closed within the target time window, and during the process of closing all DC disconnect switches, the in-terminal converter valve is locked. The second time window threshold is: in, The time from the issuance of the closing command for the DC disconnect switch until the DC disconnect switch is fully closed. The time from the issuance of the closing command of the DC disconnect switch until the internal converter valve is locked.

8. An online connection device for a multi-terminal flexible DC system, characterized in that, The multi-terminal flexible DC system includes at least two continuously operating converter terminals and a target converter terminal to be put into operation. The AC side of the target converter terminal is connected to the corresponding AC power supply through an AC circuit breaker. The positive and negative lines of the DC side of the target converter terminal are connected in parallel with the DC sides of other converter terminals through corresponding DC disconnect switches. The device is applied to the target converter terminal. The device includes: An uncontrollable charging unit is used to uncontrollably charge the in-terminal converter valve of the target converter terminal through the AC power supply of the target converter terminal, so as to increase the voltage of the sub-module of the bridge arm of the in-terminal converter valve. A controllable charging unit is used to controllably charge the internal converter valve when the voltage of the sub-module of the bridge arm of the internal converter valve rises to the uncontrolled charging voltage, so that the voltage of the sub-module of the bridge arm of the internal converter valve continues to rise. The locking unit locks the internal converter valve when the capacitor voltage of the bridge arm of the internal converter valve rises to a controllable charging voltage that is not lower than a preset rated value. The DC disconnect switch closing unit is used to close all DC disconnect switches in the target converter terminal within the target time window after locking, so as to put the target converter terminal into operation. The target time window is the time window during which the voltage of the sub-module of the bridge arm drops from the controllable charging voltage to the target voltage.

9. An online connection device for a multi-terminal flexible DC system, characterized in that, Including memory and processor; The memory is used to store programs; The processor is used to execute the program to implement the various steps of the online commissioning method for a multi-terminal flexible DC system as described in any one of claims 1-7.

10. A storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements each step of the online connection method for a multi-terminal flexible DC system as described in any one of claims 1-7.

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