Method and device for operating a current source converter, and current source converter

Abstract

The application relates to a current source converter operation method and device and a current source converter. The number of IGCT devices to be turned off to meet the active commutation demand of a single active commutation task of a same bridge arm is acquired. In the case that the current source converter has an active commutation demand, the turned-off IGCT devices are turned off in turns every time the same bridge arm performs an active commutation task. Finally, after a rotation cycle is completed, the number of times of turning off all the IGCT devices in the same bridge arm is consistent. In this way, the commutation function can be realized by turning off a small number of IGCT devices every time the bridge arm of the current source converter performs an active commutation task. Moreover, the turned-off IGCT devices are rotated every time the commutation task is performed, and all the IGCT devices do not need to be turned off every time the commutation is performed, so that the heat of the turned-off IGCT devices can be shared. The number of times of actively turning off the bridge arm of the current source converter is increased, and the ability of the current source converter to resist commutation failure is improved.

Description

Technical Field

[0001] This application relates to the field of power technology, and in particular to a current source converter operation method, apparatus and current source converter. Background Technology

[0002] The converter is a key component of HVDC (High Voltage Direct Current) transmission systems, enabling the conversion between AC and DC power. Under normal operating conditions, the IGCT (Integrated Gate-Commutated Thyristor) within the converter operates in a naturally off state. However, in situations such as external AC faults, the converter cannot achieve natural commutation, requiring the IGCT to be actively turned off to achieve active commutation.

[0003] Unlike other converters that operate in frequent switching states, the current generated by an external AC fault during active commutation in a current source converter can reach twice the normal current carrying capacity of the device. Therefore, under this condition, the active turn-off of the IGCT exhibits a heat accumulation effect; each active turn-off leads to a rise in its own temperature. If this temperature exceeds a certain threshold, the IGCT device will be damaged, limiting the number of times the converter valve arm can be actively turned off and reducing the converter valve's ability to withstand commutation failures. Summary of the Invention

[0004] Therefore, it is necessary to provide a current source converter operation method, device and current source converter to increase the number of times the bridge arm of the current source converter is actively turned off and improve the current source converter's ability to resist commutation failure.

[0005] A method for operating a current source converter includes: obtaining the number of IGCT devices to be turned off in the same bridge arm of the current source converter to meet the active commutation requirements during a single active commutation task; wherein each bridge arm includes multiple IGCT units connected in series, each IGCT unit includes one IGCT device and a protection circuit connected in parallel across the IGCT device, and the number of devices turned off is less than the total number of IGCT devices in the bridge arm; each time an active commutation task is performed in the same bridge arm, the number of IGCT devices to be turned off is controlled in turn to ensure that the number of times each IGCT device in the same bridge arm is turned off is consistent within a commutation cycle; wherein the IGCT devices turned off in each active commutation task are not exactly the same.

[0006] In one embodiment, the step of obtaining the number of IGCT devices to be turned off when the same arm of the current source converter meets the active commutation requirements in a single active commutation task includes: obtaining the peak value of the AC line voltage of the current source converter under normal operating conditions and the clamping voltage of the protection circuit; and determining the number of IGCT devices to be turned off when the same arm meets the active commutation requirements in a single active commutation task based on the peak value of the AC line voltage and the clamping voltage.

[0007] In one embodiment, determining the number of IGCT devices to be turned off in a single active commutation task for the same bridge arm, based on the peak AC line voltage and the clamping voltage, includes: determining the turn-off voltage corresponding to different pre-turn-off numbers based on the pre-turn-off number and the clamping voltage; and when the turn-off voltage is greater than the peak AC line voltage, using the corresponding pre-turn-off number as the number of IGCT devices to be turned off in a single active commutation task for the same bridge arm.

[0008] In one embodiment, the step of obtaining the number of IGCT devices to be turned off when the same bridge arm of the current source converter meets the active commutation requirements in a single active commutation task includes: obtaining the bridge arm withstand voltage required for the same bridge arm to perform a single active commutation task; and determining the number of IGCT devices to be turned off when meeting the active commutation requirements based on the total bridge arm withstand voltage that the same bridge arm can provide and the required bridge arm withstand voltage.

[0009] In one embodiment, determining the number of IGCT devices to be turned off to meet the active commutation requirement based on the total withstand voltage provided by the same bridge arm and the required bridge arm withstand voltage includes: determining the bridge arm withstand voltage corresponding to different pre-turn-off numbers based on the total withstand voltage provided by the same bridge arm and the pre-turn-off number; and when the bridge arm withstand voltage is greater than the required bridge arm withstand voltage, using the corresponding pre-turn-off number as the number of IGCT devices to be turned off to meet the active commutation requirement in a single active commutation task for the same bridge arm.

[0010] In one embodiment, the current source converter operation method further includes: acquiring the operating status parameters of the current source converter; and, if it is determined that an external AC fault has occurred based on the operating status parameters, entering an active commutation operation state.

[0011] In one embodiment, the method for determining the rotation cycle includes: determining a shutdown ratio parameter based on the number of shutdowns and the total number of IGCT devices in the bridge arm; and determining the rotation cycle based on the shutdown ratio parameter.

[0012] A current source converter operation device includes: a shutdown quantity acquisition module, used to acquire the number of IGCT devices to be shut down in the same bridge arm of the current source converter to meet the active commutation requirements in a single active commutation task; wherein each bridge arm includes multiple IGCT units connected in series, each IGCT unit includes one IGCT device, and a protection circuit connected in parallel across the IGCT device, and the shutdown quantity is less than the total number of IGCT devices in the bridge arm; and a rotation shutdown module, used to control the shutdown quantity of IGCT devices in turn each time the same bridge arm performs an active commutation task, so that the shutdown number of each IGCT device in the same bridge arm is consistent within a rotation cycle; wherein the IGCT devices shut down in each active commutation task are not exactly the same.

[0013] A current source converter includes a bridge arm power unit, a DC smoothing reactor, a converter transformer, and a controller. The bridge arm power unit is connected to a DC power supply through the DC smoothing reactor and to an AC power supply through the converter transformer. The bridge arm power unit includes multiple bridge arms, each bridge arm including multiple IGCT units connected in series, each IGCT unit including an IGCT device and a protection circuit connected in parallel across the IGCT device. The IGCT device is connected to the controller, which is used to execute the steps of the above-described current source converter operation method.

[0014] In one embodiment, the protection circuit includes a buffer circuit and a surge arrester connected in parallel.

[0015] The aforementioned current source converter operation method, apparatus, and current source converter can determine the number of IGCT devices that need to be turned off to meet the active commutation requirements for the same bridge arm during a single active commutation task. When the current source converter has an active commutation requirement, the number of IGCT devices turned off is controlled in turn each time the same bridge arm performs an active commutation task. After completing one rotation cycle, the number of times all IGCT devices in the same bridge arm are turned off is consistent. Thus, commutation can be achieved with a smaller number of IGCT devices turned off each time the bridge arm of the current source converter performs an active commutation task. Furthermore, the IGCT devices are rotated each time a commutation task is performed, eliminating the need for all IGCT devices to be turned off every time commutation occurs, thereby achieving a more even distribution of the IGCT device turn-off heat. The above scheme can reduce the heat accumulation of each IGCT device during active commutation, increase the service life of the IGCT, increase the number of active turn-offs of the current source converter bridge arm, and improve the current source converter's ability to resist commutation failure. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the current source converter topology in one embodiment of this application;

[0018] Figure 2 This is a schematic diagram of the IGCT unit structure in one embodiment of this application;

[0019] Figure 3 This is a schematic diagram of the operation method of a current source converter according to an embodiment of this application;

[0020] Figure 4 This is a schematic diagram of the operation method of a current source converter according to another embodiment of this application;

[0021] Figure 5 This is a schematic diagram of the operation method of a current source converter according to another embodiment of this application;

[0022] Figure 6 This is a schematic diagram of the operation method of a current source converter according to another embodiment of this application;

[0023] Figure 7 This is a schematic diagram of the operation method of a current source converter according to another embodiment of this application;

[0024] Figure 8 This is a schematic diagram of the operating device structure of a current source converter according to an embodiment of this application;

[0025] Figure 9 This is a schematic diagram of the operating device of a current source converter according to another embodiment of this application. Detailed Implementation

[0026] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0028] It is understood that the term "connection" in the following embodiments should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have electrical signal or data transmission with each other.

[0029] It is understandable that "at least one" refers to one or more, and "multiple" refers to two or more. "At least a part of an element" refers to part or all of an element.

[0030] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0031] The current source converter operation method provided in this application is applied to current source converters, specifically to current source converters where power units are constructed using IGCT devices. Under normal operating conditions, the current source converter of this application can achieve natural commutation, with the power units operating in a naturally off state without requiring active shutdown. However, when the current source converter experiences external AC faults or other conditions that prevent natural commutation, active commutation will be activated. That is, through the scheme of this application, the IGCT devices of each arm in the power unit are controlled to switch on and off, thus achieving the commutation function.

[0032] It should be noted that the specific type of power unit in a current source converter is not unique. In one embodiment, for easier understanding of the technical solution of this application, please refer to [link to relevant documentation]. Figure 1 Taking a three-phase six-arm bridge power unit as an example, the explanation is as follows: the bridge power unit 10 includes six arms, three upper arms and three lower arms. Each upper arm is connected to one lower arm, and the common terminal of both serves as a single-phase AC terminal, connected to the converter transformer (not shown in the figure; L in the figure represents the leakage inductance of the converter transformer). Each arm has a similar structure, including multiple IGCT units 20 connected in series. Please refer to the relevant documentation. Figure 2 Each IGCT unit 20 includes an IGCT device 22G and a protection circuit 21 connected in parallel across the IGCT device 22. Thus, in practical scenarios, the commutation function can be achieved by controlling the on / off state of the IGCT device 22 in the bridge arm.

[0033] Please see Figure 3This application provides a current source converter operation method, including steps 302 and 304.

[0034] Step 302: Obtain the number of IGCT devices that need to be turned off to meet the active commutation requirements in the same bridge arm of the current source converter during a single active commutation task.

[0035] Each bridge arm includes multiple IGCT units connected in series. Each IGCT unit includes an IGCT device and a protection circuit connected in parallel across the IGCT device. The number of IGCT devices that are turned off is less than the total number of IGCT devices in the bridge arm.

[0036] Specifically, commutation refers to the transfer of current from one path to another through the switching on and off operations of a current source converter. Active commutation, on the other hand, refers to the commutation process achieved by controlling parameters such as the switching time and sequence of the current source converter when external AC faults occur. Meeting the requirements for active commutation means that the current source converter can normally perform active commutation function. IGCT devices, or Integrated Gate Commutated Thyristors, are connected in series in the same bridge arm, and the control terminals of the IGCT devices are connected to the controller.

[0037] In active commutation operation of a current source converter, each turn-off of the IGCT (Inductively Coupled Transformer) leads to a temperature rise, i.e., heat accumulation. When the heat accumulation reaches a certain threshold, the IGCT will be damaged and unable to continue commutation. Reducing heat accumulation in the IGCT is crucial for ensuring a longer service life, and heat accumulation is directly related to the number of turn-offs. Therefore, by reasonably reducing the number of turn-offs, the service life of the IGCT can be extended to a certain extent, increasing the number of active commutations that the current source converter can achieve, and improving the current source converter's ability to withstand commutation failures.

[0038] Based on the above considerations, the solution in this application determines the number of IGCT devices that need to be turned off to meet the active commutation requirements when the same bridge arm of the current source converter performs a commutation task, based on relevant parameter information of each bridge arm. During the active turn-off task, only the IGCT devices corresponding to the number of turns-off devices need to be turned off; it is not necessary to turn off all IGCT devices in the bridge arm, thereby reducing the number of IGCT device turn-offs. It is understood that in actual scenarios, all bridge arms in the current source converter are identical, and the corresponding number of turns-off devices for each bridge arm is also identical.

[0039] It should be noted that, considering that after the current source converter design is completed, the number of shut-off valves required for the same bridge arm under a single active commutation task remains basically unchanged, the number of shut-off valves can be calculated after the current source converter design is completed and pre-stored in the controller. This data can then be directly retrieved when the current source converter requires active commutation.

[0040] In another embodiment, to ensure the accuracy of the number of shutdowns, the number of shutdowns can be calculated based on relevant parameters each time an active shutdown is detected, and the specific number can be selected according to actual needs.

[0041] Step 304: When performing active commutation task in the same bridge arm, the number of IGCT devices turned off is controlled in turn to ensure that the number of times each IGCT device in the same bridge arm is turned off is consistent within a commutation cycle.

[0042] Specifically, the IGCT devices turned off in each active commutation task are not exactly the same. A commutation cycle is the cumulative number of active commutations performed when the accumulated heat of all IGCT devices in the same current source converter is consistent. In one embodiment, the same arm of the current source converter includes 5 IGCT devices, numbered 1, 2, 3, 4, and 5, with a turn-off configuration of 3. That is, each time an active commutation task is performed, 3 IGCT devices need to be turned off. For example, the IGCT device numbers turned off in each active commutation are: first time: 1, 2, 3; second time: 2, 3, 4; third time: 3, 4, 5; fourth time: 4, 5, 1; fifth time: 5, 1, 2. Thus, after completing 5 active commutation tasks, each IGCT device has been turned off three times, and the accumulated heat has reached 3Q (Q is the heat generated by one turn-off). At this point, 5 is considered a commutation cycle.

[0043] In this embodiment, after determining the number of IGCT devices that need to be turned off to meet the active commutation requirements in a single active shutdown task for the same bridge arm, the active shutdown control of the bridge arm will be based on this number. Specifically, in each active shutdown task, only a specified number of IGCT devices are turned off, while the remaining IGCT devices remain on. Furthermore, to achieve heat distribution and prevent some IGCTs from accumulating heat, it is necessary to ensure that the IGCT devices turned off each time are not exactly the same, so that after completing one cycle of active commutation, the accumulated heat of each IGCT device is consistent.

[0044] The aforementioned current source converter operation method can determine the number of IGCT devices that need to be turned off to meet the active commutation requirements for the same bridge arm in a single active commutation task. When the current source converter has an active commutation requirement, the number of IGCT devices turned off is controlled in turn each time the same bridge arm performs an active commutation task. After completing one rotation cycle, the number of times all IGCT devices in the same bridge arm are turned off is consistent. Thus, commutation can be achieved with a smaller number of IGCT devices turned off each time the bridge arm of the current source converter performs an active commutation task. Furthermore, the IGCT devices are rotated each time a commutation task is performed, eliminating the need for all IGCT devices to be turned off in every commutation, thereby distributing the heat generated by the IGCT devices during turn-off. Through this scheme, the heat accumulation of each IGCT device during turn-off can be reduced when the bridge arm performs an active commutation task, increasing the lifespan of the IGCTs, increasing the number of times the current source converter bridge arm can be actively turned off, and improving the current source converter's ability to withstand commutation failures.

[0045] Please see Figure 4 In one embodiment, step 302 includes steps 402 and 404.

[0046] Step 402: Obtain the peak value of the AC line voltage under normal operating conditions of the current source converter, as well as the clamping voltage of the protection circuit.

[0047] Step 404: Based on the peak AC line voltage and clamping voltage, determine the number of IGCT devices that need to be turned off to meet the active commutation requirements in a single active commutation task for the same bridge arm.

[0048] Specifically, the peak AC line voltage refers to the maximum value reached by the AC side line voltage during normal operation of the current source converter (e.g., natural commutation). In practical scenarios, the peak AC line voltage can be obtained through measurement and calculation, or pre-stored in the controller; the specific method is not limited. The clamping voltage of the protection circuit is the maximum voltage that the device used for voltage clamping in the protection circuit (e.g., overvoltage protection device, specifically a surge arrester) can withstand. This voltage can also be pre-stored in the controller and directly recalled when needed.

[0049] When the IGCT devices are turned off, the current will be transmitted through the protection circuit connected in parallel. The commutation voltage that each turned-off IGCT device can provide is determined by the clamping voltage of the protection circuit. Therefore, this embodiment analyzes the AC line voltage peak and the clamping voltage to determine the number of IGCT devices that need to be turned off to meet the active commutation requirements for the same bridge arm in a single active commutation task. This ensures the accuracy of the obtained number of turned-off devices.

[0050] It should be noted that, in one embodiment, after the current source converter design is completed, the required number of shutdowns is obtained and stored by combining the peak AC line voltage under normal operating conditions of the current source converter and the clamping voltage of the protection circuit. When the current source converter has an active commutation requirement in the future, the stored number of shutdowns can be directly called without repeated analysis and calculation.

[0051] Please see Figure 5 In one embodiment, step 404 includes steps 502 and 504.

[0052] Step 502: Determine the turn-off voltage corresponding to different pre-turn-off quantities based on the number of pre-turn-off quantities and the clamping voltage.

[0053] Step 504: When the turn-off voltage is greater than the peak value of the AC line voltage, the corresponding number of pre-turn-off devices is used as the number of IGCT devices to be turned off when the active commutation requirement is met in a single active commutation task for the same bridge arm.

[0054] Specifically, the pre-turn-off quantity is the number of IGCT devices expected to be turned off when calculating the turn-off voltage. Within the same bridge arm, all IGCT cells are identical, therefore the clamping voltage of each IGCT cell is also the same. The relationship between the turn-off voltage, the pre-turn-off quantity, and the clamping voltage can be expressed as: U com =NV mov , where V mov Indicates the clamping voltage, N represents the number of pre-shutdowns, and U... com This represents the turn-off voltage; the larger the number of pre-turn-off cycles, the higher the corresponding turn-off voltage. To meet the requirements of active commutation, the turn-off voltage needs to be greater than the peak value of the AC line voltage, i.e., U. com =NV mov >U L-L , among which, U L-L This represents the peak AC line voltage under normal operating conditions. Based on the above relationship, when both the peak AC line voltage and the clamping voltage are determined, the required number of pre-shutdown devices when the turn-off voltage is greater than the peak AC line voltage can be analyzed. This number can then be used as the number of IGCT devices that need to be turned off to meet the active commutation requirements in a single active commutation task for the same bridge arm.

[0055] It is understood that, in one embodiment, the number of pre-shutdowns when the first turn-off voltage exceeds the peak value of the AC line voltage can be used as the number of turn-offs, or the number of pre-shutdowns when the turn-off voltage exceeds the peak value of the AC line voltage can be used as the number of turn-offs, as long as the number of turn-offs is less than the total number of IGCT devices in the bridge arm.

[0056] For example, in one embodiment, the number of bridge arm IGCT devices is 5, and the pre-shutdown number when the first turn-off voltage exceeds the peak AC line voltage is 3. In this case, 3 can be used as the turn-off number. In another embodiment, the turn-off voltage exceeding the peak AC line voltage is also satisfied when the pre-shutdown number is 4. In this case, 4 can also be used as the turn-off number. The specific selection can be made according to the actual needs.

[0057] The above scheme uses the number of pre-turn-off devices corresponding to a turn-off voltage greater than the peak value of the AC line voltage as the number of IGCT devices to be turned off when the active commutation requirement is met in a single active commutation task for the same bridge arm. In this way, the precise number of turn-off devices can be obtained while effectively ensuring the active commutation requirement.

[0058] Please see Figure 6 In one embodiment, step 302 includes steps 602 and 604.

[0059] Step 602: Obtain the bridge arm withstand pressure required for the same bridge arm to perform a single active commutation task.

[0060] Step 604: Based on the total withstand voltage that the same bridge arm can provide and the required bridge arm withstand voltage, determine the number of IGCT devices that need to be turned off to meet the active commutation requirements.

[0061] Specifically, the bridge arm withstand voltage refers to the maximum voltage or voltage stress that the bridge arm can withstand under specific conditions. This embodiment analyzes the issue from the perspective of bridge arm withstand voltage to determine the number of IGCT devices that need to be turned off to meet commutation requirements. Specifically, it first obtains the bridge arm withstand voltage required for a single active commutation task, i.e., the bridge arm withstand voltage required to meet commutation voltage requirements. Then, it analyzes the total bridge arm withstand voltage that the bridge arm can provide to determine the number of IGCT devices that need to be turned off.

[0062] The above scheme determines the number of IGCT devices to be turned off when meeting the active commutation requirements by using the total withstand voltage that the same bridge arm can provide and the required bridge arm withstand voltage. This ensures normal commutation, saves on the number of device operations, and also benefits the overall withstand voltage level of the current source converter, thereby improving the performance and economy of the current source converter.

[0063] Similarly, in one embodiment, after the current source converter design is completed, the required arm withstand voltage and the total arm withstand voltage are analyzed to obtain the corresponding required number of shutdowns and store them. When the current source converter has an active commutation requirement in the future, the stored number of shutdowns can be directly called without repeated analysis and calculation.

[0064] Please see Figure 7 In one embodiment, step 604 includes steps 702 and 704.

[0065] Step 702: Determine the bridge arm withstand pressure corresponding to different pre-shutdown quantities based on the total bridge arm withstand pressure that the same bridge arm can provide and the number of pre-shutdown quantities.

[0066] Step 704: When the bridge arm withstand voltage is greater than the required bridge arm withstand voltage, the corresponding pre-shutdown number is taken as the number of IGCT devices to be shut down when the same bridge arm meets the active commutation requirements in a single active commutation task.

[0067] Specifically, the pre-turn-off number is the expected number of IGCT devices to be turned off when calculating the turn-off voltage. Given a fixed total bridge arm withstand voltage, and each IGCT device providing the same bridge arm withstand voltage, the bridge arm withstand voltage provided by each IGCT device when turned off is also determined. Based on the pre-turn-off number, the actual bridge arm withstand voltage provided by the bridge arm under different turn-off numbers can be obtained. The controller compares and analyzes each bridge arm withstand voltage with the required bridge arm withstand voltage to obtain the pre-turn-off number when the bridge arm withstand voltage is greater than the required bridge arm withstand voltage. This pre-turn-off number is used as the number of IGCT devices to be turned off to meet the active commutation requirements.

[0068] Similar to the above analysis based on clamping voltage, the number of pre-shutdowns when the bridge arm withstand voltage first exceeds the required bridge arm withstand voltage can be used as the number of shutdowns, or the number of pre-shutdowns when the bridge arm withstand voltage exceeds the required bridge arm withstand voltage can be used as the number of shutdowns. As long as the number of shutdowns is less than the total number of IGCT devices in the bridge arm, it is acceptable. This will not be elaborated further here.

[0069] In a more detailed embodiment, the voltage at which the converter performs commutation using the AC grid under normal operating conditions is approximately 0.45 times the arm withstand voltage. However, when all IGCT devices in the arm are actively turned off for commutation, the voltage provided is 0.825 times the arm withstand voltage. Therefore, controlling only 3 / 5 of the IGCT devices to actively turn off is sufficient to provide 0.495 times the arm withstand voltage, which is greater than the commutation voltage under normal operating conditions, thus meeting the commutation requirements. Correspondingly, in other embodiments, controlling 4 / 5 of the IGCT devices to actively turn off can also meet the commutation requirements.

[0070] The above scheme uses the number of pre-shutdown devices corresponding to a bridge arm withstand voltage greater than the required bridge arm withstand voltage as the number of IGCT devices to be turned off when the active commutation requirement is met in a single active commutation task for the same bridge arm. In this way, the precise number of shutdown devices can be obtained while effectively ensuring the active commutation requirement.

[0071] In one embodiment, the current source converter operation method further includes: acquiring the operating status parameters of the current source converter; and, if it is determined from the operating status parameters that an external AC fault has occurred, entering an active commutation operation state.

[0072] Specifically, in this embodiment, the controller acquires the operating status parameters of the current source converter in real time and performs AC fault analysis based on these parameters. In the event of an external AC fault, it quickly enters active commutation operation. Afterward, the controller performs active shutdown control on each bridge arm according to the method provided in the above embodiment, thus realizing the active commutation function.

[0073] The above scheme can monitor the operating status of the current source converter and switch to active commutation in a timely manner when an external AC fault occurs, which can greatly reduce the risk of commutation failure of the current source converter and improve the operating reliability of the current source converter.

[0074] As shown in the above embodiment, the rotation cycle is the cumulative number of active commutations performed when the accumulated heat of each IGCT device in the same current source converter is consistent. In practical scenarios, the total number of IGCT devices in the bridge arm can be directly used as the rotation cycle. For example, in one embodiment, the total number of IGCT devices in the bridge arm is 10, and the number of IGCT devices to be turned off when the active commutation requirement is met in a single active commutation task in the same bridge arm is 6. Correspondingly, the rotation cycle can be set to 10, that is, after 10 active commutations, 6 not completely identical IGCT devices are turned off each time, so that the accumulated heat of each IGCT device is 6Q.

[0075] In other embodiments, two or more IGCT devices can be grouped together, with all IGCT devices in the same group either turned off or turned on during each active commutation task, thereby reducing the number of rotation cycles. For ease of understanding, let's take an example with a total of 10 IGCT devices in the bridge arm and 6 devices turned off. In this case, the 10 IGCT devices are grouped in pairs, resulting in 5 groups of IGCT devices. The rotation cycle can then be set to 5. In this case, 3 groups (i.e., 6 distinct IGCT devices) are turned off each time. After 5 active commutations, each group of IGCT devices is turned off three times, ensuring that the accumulated heat of each IGCT device is 3Q.

[0076] In one embodiment, the method for determining the rotation cycle includes: determining a shutdown ratio parameter based on the number of shutdowns and the total number of IGCT devices in the bridge arm; and determining the rotation cycle based on the shutdown ratio parameter.

[0077] When there is no common divisor other than 1 between the number of IGCT devices turned off and the total number of IGCT devices in the bridge arm, the numerator of the turn-off ratio parameter is the number of devices turned off, and the denominator is the total number of IGCT devices. The corresponding rotation period setting is consistent with the total number of IGCT devices. However, when there is a common divisor other than 1 between the number of IGCT devices turned off and the total number of IGCT devices in the bridge arm, the numerator of the turn-off ratio parameter is the value obtained by dividing the number of devices turned off by the common divisor, and the denominator is the value obtained by dividing the total number of IGCT devices by the common divisor. In this case, the denominator can be used as the rotation period, but the IGCT devices in the bridge arm need to be grouped. Each group of IGCT devices must be turned off or turned on simultaneously, and the number of devices in each group must be consistent with the common divisor.

[0078] For ease of understanding, the following explanation assumes a total of 10 IGCT devices. In one embodiment, if the number of devices turned off is 7, then the turn-off ratio parameter is 7 / 10, corresponding to a rotation cycle of 10. Each time an active commutation task is performed, 7 not entirely identical IGCT devices need to be turned off. After 10 rotations, each IGCT device can accumulate 7Q of heat.

[0079] In another embodiment, if the number of shutdowns is 6, then the corresponding shutdown ratio parameter is 3 / 5, and the corresponding rotation cycle is 5. In this case, the 10 IGCT devices need to be grouped into pairs. Each time an active commutation task is performed, 3 groups of not completely identical IGCT devices need to be shut down. Finally, after 5 rotations, each group of IGCT devices has been shut down three times. At this time, each IGCT device accumulates 3Q of heat.

[0080] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0081] Based on the same inventive concept, this application also provides a current source converter operation device for implementing the aforementioned current source converter operation method. The solution provided by this device is similar to the solution described in the above method; therefore, the specific limitations in one or more current source converter operation device embodiments provided below can be found in the limitations of the current source converter operation method described above, and will not be repeated here.

[0082] Please see Figure 8 A current source converter operating device includes a shutdown quantity acquisition module 802 and a rotation shutdown module 804.

[0083] The shutdown quantity acquisition module 802 is used to acquire the number of IGCT devices that need to be turned off in the same bridge arm of the current source converter to meet the active commutation requirements in a single active commutation task. The rotating shutdown module 804 is used to control the number of IGCT devices turned off in turn each time an active commutation task is performed in the same bridge arm, so that the number of shutdowns of each IGCT device in the same bridge arm is consistent within a rotation cycle.

[0084] In one embodiment, the shutdown quantity acquisition module 802 is further used to acquire the peak value of the AC line voltage under normal operating conditions of the current source converter and the clamping voltage of the protection circuit; based on the peak value of the AC line voltage and the clamping voltage, determine the number of IGCT devices to be shut down when the active commutation requirement is met in a single active commutation task for the same bridge arm.

[0085] In one embodiment, the shutdown quantity acquisition module 802 is further configured to determine the shutdown voltage corresponding to different pre-shutdown quantities based on the pre-shutdown quantity and the clamping voltage; when the shutdown voltage is greater than the peak value of the AC line voltage, the corresponding pre-shutdown quantity is used as the number of IGCT devices to be shut down when the same bridge arm meets the active commutation requirements in a single active commutation task.

[0086] In one embodiment, the shutdown quantity acquisition module 802 is further configured to acquire the required bridge arm withstand voltage for the same bridge arm to perform a single active commutation task; and determine the number of IGCT devices to be shut down when the active commutation requirement is met based on the total bridge arm withstand voltage that the same bridge arm can provide and the required bridge arm withstand voltage.

[0087] In one embodiment, the shutdown quantity acquisition module 802 is further configured to determine the bridge arm withstand voltage corresponding to different pre-shutdown quantities based on the total bridge arm withstand voltage that the same bridge arm can provide and the pre-shutdown quantity; when the bridge arm withstand voltage is greater than the required bridge arm withstand voltage, the corresponding pre-shutdown quantity is used as the number of IGCT devices to be shut down when the same bridge arm meets the active commutation requirements in a single active commutation task.

[0088] Please see Figure 9 In one embodiment, the current source converter operating device further includes a fault monitoring module 902.

[0089] The fault monitoring module 902 is used to acquire the operating status parameters of the current source converter; when it is determined that an external AC fault has occurred based on the operating status parameters, it enters the active commutation operation state.

[0090] Each module in the aforementioned current source converter operating device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in the processor of a computer device in hardware form or independent of it, or stored in the memory of a computer device in software form, so that the processor can call and execute the operations corresponding to each module.

[0091] The aforementioned current source converter operating device can determine the number of IGCT devices that need to be turned off to meet the active commutation requirements for the same bridge arm during a single active commutation task. When the current source converter has an active commutation requirement, the number of IGCT devices turned off is controlled in turn each time the same bridge arm performs an active commutation task. After completing one rotation cycle, the number of times all IGCT devices in the same bridge arm are turned off is consistent. In this way, commutation can be achieved with a smaller number of IGCT devices turned off each time the bridge arm of the current source converter performs an active commutation task. Furthermore, the IGCT devices are rotated each time a commutation task is performed, eliminating the need for all IGCT devices to be turned off in every commutation, thus achieving a more even distribution of IGCT device turn-off heat. Through this scheme, the heat accumulation of each IGCT device during active commutation tasks can be reduced, increasing the lifespan of the IGCTs, increasing the number of times the current source converter bridge arm can be actively turned off, and improving the current source converter's ability to withstand commutation failures.

[0092] Please refer to the following: Figure 1 This application provides a current source converter, including a bridge arm power unit 10, a DC smoothing reactor Ldc, a converter transformer, and a controller (not shown). The bridge arm power unit 10 is connected to a DC power supply (not shown) through the DC smoothing reactor Ldc, and the bridge arm power unit 10 is connected to an AC power supply (not shown) through the converter transformer. The bridge arm power unit 10 includes multiple bridge arms, each bridge arm including multiple IGCT units 20 connected in series, each IGCT unit 20 including an IGCT device 22, and a protection circuit 21 connected in parallel across the IGCT device 22. The IGCT device 22 is connected to the controller, and the controller is used to execute the steps of the above-described current source converter operation method.

[0093] Specifically, the operation method of the current source converter is as described in the above embodiments and accompanying drawings, and will not be repeated here. This current source converter can determine the number of IGCT devices 22 that need to be turned off to meet the active commutation requirements for the same bridge arm in a single active commutation task. When the current source converter has an active commutation requirement, the number of IGCT devices 22 turned off is controlled in turn each time the same bridge arm performs an active commutation task. Finally, after completing one rotation cycle, the number of times all IGCT devices 22 in the same bridge arm are turned off is consistent. Thus, commutation can be achieved by turning off a smaller number of IGCT devices 22 each time the bridge arm of the current source converter performs an active commutation task. Furthermore, the turned-off IGCT devices 22 are rotated each time a commutation task is performed, eliminating the need for all IGCT devices 22 to be turned off in every commutation, thereby achieving a more even distribution of the heat generated by the IGCT devices 22 during commutation. The above solution can reduce the heat accumulation of each IGCT device 22 during active commutation of the bridge arm, increase the service life of the IGCT, increase the number of active turn-offs of the current source converter bridge arm, and improve the current source converter's ability to resist commutation failure.

[0094] Please refer to the following: Figure 2 In one embodiment, the protection circuit 21 includes a buffer circuit 211 and a surge arrester RS ​​connected in parallel.

[0095] Specifically, in this embodiment, the protection circuit 21 includes a parallel buffer circuit 211 and a surge arrester RS. This effectively prevents overvoltage from occurring across the IGCT device 22 during the operation of the current source converter, thus improving the operational safety of the IGCT device 22. It is understood that the specific structure of the buffer circuit 211 is not unique. In one embodiment, the buffer circuit 211 includes a resistor and a capacitor connected in series. The buffer circuit 211 can suppress the supplementation of turn-off overvoltage.

[0096] In the description of this specification, references to terms such as "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0097] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0098] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for operating a current source converter, characterized in that, include: The number of IGCT devices to be turned off in the same bridge arm of the current source converter to meet the active commutation requirements in a single active commutation task is obtained; wherein each bridge arm includes multiple IGCT units connected in series, each IGCT unit includes one IGCT device and a protection circuit connected in parallel across the IGCT device, and the number of devices to be turned off is less than the total number of IGCT devices in the bridge arm. Each time an active commutation task is performed in the same bridge arm, the number of IGCT devices to be turned off is controlled in turn to ensure that the number of times each IGCT device in the same bridge arm is turned off is consistent within a commutation cycle; wherein, the IGCT devices turned off in each active commutation task are not exactly the same.

2. The current source converter operation method according to claim 1, characterized in that, The number of IGCT devices to be turned off in the same bridge arm of the current source converter to meet the active commutation requirements in a single active commutation task includes: Obtain the peak AC line voltage of the current source converter under normal operating conditions, as well as the clamping voltage of the protection circuit; Based on the peak AC line voltage and the clamping voltage, determine the number of IGCT devices that need to be turned off to meet the active commutation requirements in a single active commutation task for the same bridge arm.

3. The current source converter operation method according to claim 2, characterized in that, The step of determining the number of IGCT devices to be turned off in the same bridge arm to meet the active commutation requirements under a single active commutation task, based on the peak AC line voltage and the clamping voltage, includes: Based on the number of pre-turn-offs and the clamping voltage, determine the turn-off voltage corresponding to different numbers of pre-turn-offs; When the turn-off voltage is greater than the peak value of the AC line voltage, the corresponding number of pre-turn-off devices is taken as the number of IGCT devices to be turned off when the active commutation requirement is met in a single active commutation task for the same bridge arm.

4. The current source converter operation method according to claim 1, characterized in that, The number of IGCT devices to be turned off in the same bridge arm of the current source converter to meet the active commutation requirements in a single active commutation task includes: Obtain the bridge arm withstand pressure required for the same bridge arm to perform a single active commutation task; Based on the total withstand voltage that the same bridge arm can provide and the required bridge arm withstand voltage, determine the number of IGCT devices that need to be turned off to meet the active commutation requirements.

5. The current source converter operation method according to claim 4, characterized in that, The determination of the number of IGCT devices to be turned off to meet the active commutation requirements, based on the total withstand voltage provided by the same bridge arm and the required bridge arm withstand voltage, includes: Based on the total bridge arm withstand pressure that the same bridge arm can provide and the number of pre-shutdowns, determine the bridge arm withstand pressure corresponding to different pre-shutdown numbers; When the withstand voltage of the bridge arm is greater than the required withstand voltage of the bridge arm, the corresponding number of pre-shutdown devices is taken as the number of IGCT devices to be shut down when the active commutation requirement is met in a single active commutation task for the same bridge arm.

6. The method for operating a current source converter according to any one of claims 1-5, characterized in that, The current source converter operation method further includes: Obtain the operating status parameters of the current source converter; If an external AC fault is determined based on the aforementioned operating status parameters, the system enters active commutation operation mode.

7. The method for operating a current source converter according to any one of claims 1-5, characterized in that, The method for determining the rotation cycle includes: The shutdown ratio parameter is determined based on the number of devices turned off and the total number of IGCT devices in the bridge arm. The rotation cycle is determined based on the shutdown ratio parameter.

8. A current source converter operating device, characterized in that, include: The shutdown quantity acquisition module is used to acquire the number of IGCT devices that need to be turned off in the same bridge arm of the current source converter to meet the active commutation requirements in a single active commutation task; wherein, each bridge arm includes multiple IGCT units connected in series, each IGCT unit includes one IGCT device and a protection circuit connected in parallel across the IGCT device, and the shutdown quantity is less than the total number of IGCT devices in the bridge arm. The rotating shutdown module is used to control the shutdown of the specified number of IGCT devices in turn each time an active commutation task is performed in the same bridge arm, so that the number of shutdowns of each IGCT device in the same bridge arm is consistent within a rotation cycle; wherein the IGCT devices shut down in each active commutation task are not exactly the same.

9. A current source converter, characterized in that, It includes a bridge arm power unit, a DC smoothing reactor, a converter transformer, and a controller. The bridge arm power unit is connected to a DC power supply through the DC smoothing reactor, and the bridge arm power unit is connected to an AC power supply through the converter transformer. The bridge arm power unit includes multiple bridge arms, each bridge arm includes multiple IGCT units connected in series, each IGCT unit includes an IGCT device and a protection circuit connected in parallel across the IGCT device, the IGCT device is connected to the controller, and the controller is used to execute the steps of the current source converter operation method according to any one of claims 1-7.

10. The current source converter according to claim 9, characterized in that, The protection circuit includes a buffer circuit and a surge arrester connected in parallel.

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