Current source converter operation method and device and current source converter

Abstract

The invention relates to a current source converter operation method and device and a current source converter, and aims to obtain the turn-off number of IGCT devices which need to be turned off when the same bridge arm meets the active commutation requirement under a single active commutation task. And under the condition that the current source converter has an active commutation requirement, when the same bridge arm executes an active commutation task every time, the IGCT devices with the turn-off number are controlled to be turned off in turn. And finally, after one rotation period is completed, the turn-off times of all IGCT devices in the same bridge arm are consistent. Therefore, when the bridge arm of the current source converter executes an active commutation task each time, a commutation function can be realized in a mode that a small number of IGCT devices are turned off. Moreover, when the commutation task is executed every time, the switched-off IGCT devices are switched off, and all the IGCT devices do not need to be switched off every time the commutation task is executed, so that the uniform distribution of the switching-off heat of the IGCT devices is realized. The number of times of active turn-off of the bridge arm of the current source converter is increased, and the commutation failure resistance of the current source converter is improved.

Description

Technical Field

[0001] The present application relates to the field of electric power technology, and in particular to a current source converter operation method, device and current source converter. Background Art

[0002] The converter is a key component of the HVDC (high voltage direct current) transmission system, which can realize the conversion between AC power and DC power. When the converter is working normally, the IGCT (Integrated Gate-Commutated Thyristor) in the converter can work in the natural off state. However, when there is an external AC fault or other working conditions, the converter cannot achieve natural commutation, and the IGCT needs to be actively shut down to achieve the active commutation function.

[0003] Unlike other converters that work in a frequent switching state, when the current source converter is actively commutating, the current generated by the external AC fault will reach twice the normal current of the device. Therefore, under this working condition, the active shutdown of the IGCT has a heat accumulation effect. Each active shutdown will cause its own temperature to rise. When the temperature exceeds a certain level, the IGCT device will be damaged, and the number of active shutdowns of the converter valve bridge arm is limited, reducing the ability of the converter valve to resist commutation failure. Summary of the invention

[0004] Based on this, 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 shut down and improve the ability of the current source converter to resist commutation failure.

[0005] A method for operating a current source converter comprises: obtaining the number of IGCT devices that need to be turned off when the same bridge arm of the current source converter meets the active commutation requirement under a single active commutation task; wherein each of the bridge arms comprises a plurality of IGCT units connected in series, each of the IGCT units comprises an IGCT device, and a protection circuit connected in parallel at both ends of the IGCT device, and the number of IGCT devices that are turned off is less than the total number of IGCT devices in the bridge arm; when the same bridge arm performs an active commutation task each time, the number of IGCT devices that are turned off is controlled to be turned off in turn, so that the number of times the IGCT devices in the same bridge arm are turned off is consistent within a rotation cycle; wherein the IGCT devices turned off for each active commutation task are not completely the same.

[0006] In one of the embodiments, obtaining the number of IGCT devices that need to be turned off to meet the active commutation requirement in the same bridge arm of the current source converter under a single active commutation task includes: obtaining 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; determining the number of IGCT devices that need to be turned off to meet the active commutation requirement in the same bridge arm under a single active commutation task based on the peak value of the AC line voltage and the clamping voltage.

[0007] In one of the embodiments, determining the number of IGCT devices that need to be turned off to meet the active commutation requirement in the same bridge arm under a single active commutation task based on the AC line voltage peak value 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 AC line voltage peak value, using the corresponding pre-turn-off number as the number of IGCT devices that need to be turned off to meet the active commutation requirement in the same bridge arm under a single active commutation task.

[0008] In one of the embodiments, the method of obtaining the number of IGCT devices that need to be turned off to meet the active commutation requirement under a single active commutation task in the same bridge arm of the current source converter includes: obtaining the required bridge arm withstand voltage for the same bridge arm to perform a single active commutation task; determining the number of IGCT devices that need to be turned off to meet the active commutation requirement based on the total bridge arm withstand voltage that can be provided by the same bridge arm and the required bridge arm withstand voltage.

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

[0010] In one of the embodiments, the current source converter operation method further includes: obtaining an operation status parameter of the current source converter; and entering an active commutation operation state when it is determined according to the operation status parameter that an external AC fault occurs.

[0011] In one of the embodiments, the method for determining the rotation period includes: determining a turn-off ratio parameter according to the turn-off quantity and the total number of IGCT devices in the bridge arm; and determining the rotation period according to the turn-off ratio parameter.

[0012] A current source converter operation device comprises: a shutdown number acquisition module, used for acquiring the shutdown number of IGCT devices that need to be shut down when the same bridge arm of the current source converter meets the active commutation requirement under a single active commutation task; wherein each of the bridge arms comprises a plurality of IGCT units connected in series, each of the IGCT units comprises an IGCT device, and a protection circuit connected in parallel at both ends of the IGCT device, and the shutdown number is less than the total number of IGCT devices in the bridge arm; a rotation shutdown module, used for controlling the shutdown of the IGCT devices of the shutdown number in turn when the same bridge arm performs an active commutation task each time, so that the shutdown times of each IGCT device in the same bridge arm within a rotation cycle are consistent; wherein the IGCT devices shut down for each active commutation task are not completely the same.

[0013] A current source converter comprises a bridge arm power unit, a DC smoothing reactor, a converter transformer and a controller, wherein the bridge arm power unit is connected to a DC power supply via the DC smoothing reactor, and the bridge arm power unit is connected to an AC power supply via the converter transformer; the bridge arm power unit comprises a plurality of bridge arms, each of the bridge arms comprises a plurality of IGCT units connected in series, each of the IGCT units comprises an IGCT device, and a protection circuit connected in parallel at both ends of the IGCT device, the IGCT device is connected to the controller, and the controller is used to execute the steps of the above-mentioned current source converter operation method.

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

[0015] The above-mentioned current source converter operation method, device and current source converter can obtain the number of IGCT devices that need to be turned off to meet the active commutation requirements of the same bridge arm under a single active commutation task. When the current source converter has an active commutation requirement, each time the same bridge arm performs an active commutation task, the IGCT devices that are turned off are controlled to be turned off in turn. Finally, after completing a rotation cycle, the number of shutdowns of all IGCT devices in the same bridge arm is consistent. In this way, the commutation function can be achieved by turning off a smaller number of IGCT devices each time the bridge arm of the current source converter performs an active commutation task. In addition, each time a commutation task is performed, the turned-off IGCT devices are rotated, and all IGCT devices do not need to be turned off at each commutation, thereby achieving the even distribution of the heat generated by the IGCT device shutdown. Through the above scheme, when the bridge arm performs active commutation tasks, the shutdown heat accumulation of each IGCT device can be reduced, the service life of the IGCT can be increased, the number of active shutdowns of the current source converter bridge arm can be increased, and the ability of the current source converter to resist commutation failure can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0017] Figure 1 This is a schematic diagram of the topological structure of a current source converter in an embodiment of the present application;

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

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

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

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

[0022] Figure 6 This is a flow chart of a current source converter operation method according to another embodiment of the present application;

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

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

[0025] Fig. 9 This is a schematic structural diagram of a current source converter operating device according to another embodiment of the present application. DETAILED DESCRIPTION

[0026] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0028] It can be understood that the “connection” in the following embodiments should be understood as “electrical connection”, “communication connection”, etc. if the connected circuits, modules, units, etc. have electrical signals or data transmission between each other.

[0029] It can be understood that “at least one” means one or more, “plurality” means two or more, and “at least a portion of an element” means a part or all of an element.

[0030] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like specify the presence of stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. At the same time, the term "and / or" used in this specification includes any and all combinations of the relevant listed items.

[0031] The current source converter operation method provided in the embodiment of the present application is applied to the current source converter, and is specifically applied to the current source converter of this type that forms a power unit through IGCT devices. The current source converter of the present application can realize natural commutation under normal operating conditions, and the power unit operates in a natural shutdown state without active shutdown; and when the current source converter encounters external AC faults and other working conditions, and natural commutation cannot be achieved, active commutation will be turned on, that is, through the solution of the embodiment of the present application, the IGCT devices of each bridge arm in the power unit are controlled to be turned on and off to realize the commutation function.

[0032] It should be noted that the specific type of the power unit in the current source converter is not unique. In one embodiment, in order to facilitate understanding of the technical solution of the present application, please refer to Figure 1 , taking a three-phase six-bridge arm power unit as an example for explanation, the bridge arm power unit 10 includes six bridge arms, including three upper bridge arms and three lower bridge arms, each upper bridge arm is connected to a corresponding lower bridge arm, and the common end of the two is used as a phase AC end and connected to the converter transformer (not shown in the figure, L in the figure is the leakage inductance of the converter transformer). The structure of each bridge arm is similar, and each includes a plurality of IGCT units 20 connected in series. Please refer to Figure 2 Each IGCT unit 20 includes an IGCT device 22G and a protection circuit 21 connected in parallel at both ends of the IGCT device 22. In this way, in an actual scenario, the phase switching function can be achieved by controlling the on and off of the IGCT device 22 in the bridge arm.

[0033] See also Figure 3The present application provides a current source converter operation method, including step 302 and step 304.

[0034] Step 302, obtaining the number of IGCT devices that need to be turned off when the same bridge arm of the current source converter meets the active commutation requirement under a single active commutation task.

[0035] Each bridge arm includes a plurality of IGCT units connected in series, each IGCT unit includes an IGCT device and a protection circuit connected in parallel at both ends of the IGCT device, and the number of shutdown circuits 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 opening and closing operations of the current source converter. Active commutation refers to the process of achieving commutation by controlling the opening and closing time, sequence and other parameters of the current source converter when an external AC fault occurs in the current source converter. Meeting the active commutation requirements means that the current source converter can normally realize the active commutation function. IGCT devices are also called integrated gate commutated thyristors. In the same bridge arm, each IGCT device is connected in series, and the control end of the IGCT device is connected to the controller.

[0037] Under the active commutation condition of the current source converter, each time the IGCT device is turned off, its own temperature will rise, that is, heat accumulation. When the heat accumulation of the IGCT device reaches a certain threshold, the IGCT device will be damaged and unable to continue the commutation operation. Reducing the heat accumulation of the IGCT device is the key to ensuring a long service life of the IGCT, and the heat accumulation of the IGCT device is directly related to the number of times the IGCT device is turned off. Therefore, by reasonably reducing the number of times the IGCT device is turned off, the service life of the IGCT device can be extended to a certain extent, the number of active commutations that can be achieved by the current source converter can be increased, and the ability of the current source converter to resist commutation failure can be improved.

[0038] Based on the above considerations, the solution of the embodiment of the present application determines the number of IGCT devices that need to be turned off when the same bridge arm of the current source converter performs a commutation task to meet the active commutation requirements from the relevant parameter information of each bridge arm in the current source converter. When performing the active shutdown task, it is only necessary to control the shutdown of the IGCT devices corresponding to the shutdown number, without the need to shut down all the IGCT devices in the bridge arm, thereby reducing the number of shutdowns of the IGCT devices. It can be understood that in actual scenarios, the bridge arms in the current source converter are consistent, and the corresponding shutdown numbers of each bridge arm are consistent.

[0039] It should be pointed out that after the design of the current source converter is completed, the number of required shutdowns for the same bridge arm under a single active commutation task is basically unchanged. Therefore, in order to improve the operating efficiency of the current source converter valve, the number of shutdowns can be calculated after the design of the current source converter is completed and stored in the controller in advance, and can be directly called when the current source converter has an active commutation requirement.

[0040] In another embodiment, in order to ensure the accuracy of the shutdown number, each time the need for active shutdown is detected, calculations are performed based on relevant parameters to obtain the shutdown number, and the shutdown number can be selected based on actual needs.

[0041] Step 304, when the same bridge arm performs an active commutation task each time, the IGCT devices with the same number of IGCT devices being turned off are controlled to be turned off in turn, so that the number of times the IGCT devices in the same bridge arm are turned off is consistent within one rotation cycle.

[0042] Specifically, the IGCT devices turned off for each active commutation task are not exactly the same. A 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 one embodiment, the same bridge arm of the current source converter includes 5 IGCT devices, which are numbered 1, 2, 3, 4, and 5, and the number of shutdowns is configured as 3, that is, each time the active commutation task is performed, 3 IGCT devices need to be controlled to be turned off. For example, the numbering of the IGCT devices turned off for each active commutation is: the first time: 1, 2, 3, the second time: 2, 3, 4, the third time: 3, 4, 5, the fourth time: 4, 5, 1, and the fifth time: 5, 1, 2. In this way, after completing 5 active commutation tasks, each IGCT device has been turned off three times, and the accumulated heat has reached 3Q (the heat generated by one shutdown is Q). At this time, 5 is regarded as a rotation cycle.

[0043] In this embodiment, after determining the number of IGCT devices that need to be turned off in the same bridge arm to meet the active commutation requirements under an active shutdown task, the active shutdown control of the bridge arm will be performed based on this. Specifically, each time the active shutdown task is performed, only the IGCT devices with the number of IGCT devices that are turned off are controlled to be turned off, and the remaining IGCT devices remain in the on state. Furthermore, in order to achieve heat sharing and avoid continuous heat accumulation in some IGCTs, it is necessary to control the IGCT devices that are turned off each time to be different, so that after the active commutation of a rotation cycle is finally completed, the accumulated heat of each IGCT device is consistent.

[0044] The above-mentioned current source converter operation method can obtain the number of IGCT devices that need to be turned off when the same bridge arm meets the active commutation requirement under a single active commutation task. When the current source converter has an active commutation requirement, the same bridge arm controls the number of IGCT devices that are turned off to turn off in turn each time the active commutation task is performed. Finally, after completing a rotation cycle, the number of times all IGCT devices in the same bridge arm are turned off is consistent. In this way, the commutation function can be achieved by turning off a smaller number of IGCT devices each time the bridge arm of the current source converter performs an active commutation task. In addition, each time the commutation task is performed, the turned-off IGCT devices are rotated, and all IGCT devices do not need to be turned off each time the commutation is performed, so as to achieve the equalization of the heat of the IGCT device shutdown. Through the above-mentioned scheme, when the bridge arm performs the active commutation task, the accumulation of the shutdown heat of each IGCT device can be reduced, the service life of the IGCT can be increased, the number of times the bridge arm of the current source converter is actively turned off can be increased, and the ability of the current source converter to resist commutation failure can be improved.

[0045] See also Figure 4 In one embodiment, step 302 includes step 402 and step 404.

[0046] Step 402, obtaining 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.

[0047] Step 404, determining the number of IGCT devices that need to be turned off to meet the active commutation requirement in the same bridge arm under a single active commutation task according to the AC line voltage peak value and the clamping voltage.

[0048] Specifically, the peak value of the AC line voltage refers to the maximum value reached by the AC side line voltage during the normal operation of the current source converter (such as natural commutation conditions). In actual scenarios, the peak value of the AC line voltage can be obtained by measurement and calculation, or it can be pre-stored in the controller, and there is no specific limitation. The clamping voltage of the protection circuit is the maximum voltage that the device used for voltage clamping in the protection circuit (such as an overvoltage protection device, which can be a lightning arrester, etc.) can withstand. It can also be pre-stored in the controller and can be directly called when there is a need for use.

[0049] When the IGCT device is turned off, the current will be transmitted through the protection circuit connected in parallel with it. At this time, the commutation voltage that each turned-off IGCT device can provide will be determined by the clamping voltage of the protection circuit. Therefore, the solution of this embodiment combines the AC line voltage peak and the clamping voltage for analysis to determine the number of IGCT devices that need to be turned off in the same bridge arm to meet the active commutation requirements under a single active commutation task. In this way, the accuracy of the obtained shutdown number can be guaranteed.

[0050] It should be pointed out that, in one embodiment, after the design of the current source converter is completed, the corresponding required number of shutdowns is obtained and stored in combination with the AC line voltage peak 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 subsequently, the stored number of shutdowns can be directly called without repeated analysis and calculation.

[0051] See also Figure 5 In one embodiment, step 404 includes step 502 and step 504.

[0052] Step 502: Determine the turn-off voltages corresponding to different pre-turn-off numbers according to the pre-turn-off numbers and the clamping voltage.

[0053] Step 504, when the shutdown voltage is greater than the peak value of the AC line voltage, the corresponding pre-shutdown quantity is used as the shutdown quantity of the IGCT devices that need to be shut down in the same bridge arm to meet the active commutation requirement under a single active commutation task.

[0054] Specifically, the pre-shutdown number is the estimated number of IGCT devices that need to be shut down when calculating the shutdown voltage. In the same bridge arm, each IGCT unit is consistent, so the clamping voltage of each IGCT unit is also the same. The relationship between the shutdown voltage, the pre-shutdown number, and the clamping voltage can be expressed as: U com =NV mov , where V mov represents the clamping voltage, N represents the number of pre-shutdown, U com Indicates the turn-off voltage. The larger the number of pre-turn-offs, the higher the corresponding turn-off voltage. In order to meet the active commutation requirements, the turn-off voltage needs to be greater than the peak value of the AC line voltage, that is, U com =NV mov >U L-L , where U L-L Represents the peak value of the AC line voltage under normal working conditions. According to the above relationship, when the peak value of the AC line voltage and the clamping voltage are determined, the required number of pre-shutdowns can be analyzed when the shutdown voltage is greater than the peak value of the AC line voltage, and it can be used as the number of IGCT devices that need to be shut down in the same bridge arm to meet the active commutation requirements under a single active commutation task.

[0055] It can be understood that in one embodiment, the pre-shutdown number when the shutdown voltage is greater than the peak value of the AC line voltage for the first time can be used as the shutdown number, or the pre-shutdown number when the shutdown voltage is greater than the peak value of the AC line voltage for other times can be used as the shutdown number, as long as the shutdown number is ensured to be 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 shutdown voltage is greater than the peak value of the AC line voltage for the first time is 3, and 3 can be used as the shutdown number at this time. In another embodiment, when the pre-shutdown number is 4, the shutdown voltage is also greater than the peak value of the AC line voltage. In this case, 4 can also be used as the shutdown number, and the selection can be made in combination with actual needs.

[0057] In the above scheme, the shutdown voltage is greater than the pre-shutdown number corresponding to the peak value of the AC line voltage, which is the shutdown number of IGCT devices that need to be shut down in the same bridge arm to meet the active commutation requirement under a single active commutation task. In this way, the accurate shutdown number can be obtained while effectively ensuring the active commutation requirement.

[0058] See also Figure 6 In one embodiment, step 302 includes step 602 and step 604.

[0059] Step 602, obtaining the bridge arm withstand voltage required for the same bridge arm to perform a single active commutation task.

[0060] Step 604, determining the number of IGCT devices that need to be turned off to meet the active commutation requirement according to the total bridge arm withstand voltage that can be provided by the same bridge arm and the required bridge arm withstand voltage.

[0061] Specifically, the bridge arm withstand voltage is the maximum voltage or voltage stress that the bridge arm can withstand under specific conditions. The solution of this embodiment is analyzed from the perspective of the bridge arm withstand voltage to determine the number of IGCT devices that need to be turned off when the commutation requirement is met. Specifically, the bridge arm withstand voltage required for the same bridge arm to perform a single active commutation task is first obtained, that is, the bridge arm withstand voltage required to meet the commutation voltage requirement, and then the number of IGCT devices that need to be turned off is analyzed in combination with the total bridge arm withstand voltage that can be provided by the bridge arm.

[0062] The above scheme determines the number of IGCT devices that need to be turned off to meet 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. This not only ensures normal commutation and saves the number of device actions, but is also beneficial to the overall withstand voltage level of the current source converter and improves the performance and economy of the current source converter.

[0063] Similarly, in one embodiment, after the current source converter is designed, the required bridge arm withstand voltage and the total bridge arm withstand voltage are analyzed to obtain the corresponding required shutdown number and store it. When the current source converter has an active commutation requirement later, the stored shutdown number can be directly called without repeated analysis and calculation.

[0064] See also Figure 7 In one embodiment, step 604 includes step 702 and step 704.

[0065] Step 702: Determine the bridge arm withstand voltages corresponding to different pre-shutdown numbers according to the total bridge arm withstand voltages that can be provided by the same bridge arm and the pre-shutdown numbers.

[0066] Step 704, when the bridge arm withstand voltage is greater than the required bridge arm withstand voltage, the corresponding pre-shutdown quantity is used as the shutdown quantity of IGCT devices that need to be shut down in the same bridge arm to meet the active commutation requirement under a single active commutation task.

[0067] Specifically, the pre-shutdown number is the estimated number of IGCT devices that need to be shut down when calculating the shutdown voltage. When the total bridge arm withstand voltage is determined, the bridge arm withstand voltage that each IGCT device can provide is consistent, so the bridge arm withstand voltage that each IGCT device can provide when shutting down is also determined accordingly. According to the pre-shutdown number, the bridge arm withstand voltage that the bridge arm can actually provide under different shutdown numbers can be obtained. The controller compares and analyzes each bridge arm withstand voltage with the required bridge arm withstand voltage, and obtains the pre-shutdown number when the bridge arm withstand voltage is greater than the required bridge arm withstand voltage, which is used as the shutdown number of IGCT devices required to be shut down when meeting the active commutation requirements.

[0068] Similar to the above analysis in combination with the clamping voltage, the number of pre-shutdowns when the bridge arm withstand voltage is greater than the required bridge arm withstand voltage for the first time can be used as the number of shutdowns, or the number of pre-shutdowns when the bridge arm withstand voltage is greater than the required bridge arm withstand voltage for other times can be used as the number of shutdowns. As long as the number of shutdowns is ensured to be less than the total number of IGCT devices in the bridge arm, it will not be repeated here.

[0069] In a more detailed embodiment, the voltage of the converter when using the AC power grid for commutation under normal working conditions is about 0.45 times the bridge arm withstand voltage, and when all the IGCT devices in the bridge arm are actively turned off for commutation, a bridge arm withstand voltage of 0.825 times can be provided. Therefore, only 3 / 5 of the IGCT devices need to be actively turned off to provide 0.495 times the bridge arm withstand voltage, which is greater than the commutation voltage under normal working conditions and meets the commutation requirements. Correspondingly, in other embodiments, 4 / 5 of the IGCT devices can also be controlled to be actively turned off, which also meets the commutation requirements.

[0070] In the above scheme, the pre-shutdown number corresponding to the bridge arm withstand voltage being greater than the required bridge arm withstand voltage is used as the shutdown number of IGCT devices that need to be shut down when the same bridge arm meets the active commutation requirement under a single active commutation task. In this way, an accurate shutdown number can be obtained while effectively ensuring the active commutation requirement.

[0071] In one of the embodiments, the current source converter operation method further includes: obtaining an operation state parameter of the current source converter; and entering an active commutation operation state when it is determined according to the operation state parameter that an external AC fault has occurred.

[0072] Specifically, in the scheme of this embodiment, the controller obtains the operating state parameters of the current source converter in real time, and performs AC fault analysis in combination with the operating state parameters, and quickly enters the active commutation operating state in the event of an external AC fault. After that, the controller actively shuts down each bridge arm according to the method provided in the above embodiment to realize the active commutation function.

[0073] The above scheme can monitor the operating status of the current source converter and switch to active commutation in time 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 period 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 actual scenarios, the total number of IGCT devices in the bridge arm can be directly used as the rotation period. For example, in one embodiment, the total number of IGCT devices in the bridge arm is 10, and the number of IGCT devices that need to be turned off when the same bridge arm meets the active commutation requirements under a single active commutation task is 6. Correspondingly, the rotation period can be set to 10, that is, after 10 active commutations, 6 non-identical IGCT devices are turned off each time, and finally the accumulated heat of each IGCT device is 6Q.

[0075] In other embodiments, two or more IGCT devices can be used as a group, and the IGCT devices in the same group are all turned off or turned on under each active commutation task, so as to reduce the number of rotation cycles. For ease of understanding, taking the total number of IGCT devices in the bridge arm as 10 and the number of shutdowns as 6 as an example, 10 IGCT devices are used as a group in pairs, and a total of 5 groups of IGCT devices are obtained. At this time, the rotation cycle can also be set to 5. At this time, 3 groups (that is, 6) of non-identical IGCT devices are turned off each time. After 5 active commutations, each group of IGCT devices is turned off three times, so that the accumulated heat of each IGCT device is 3Q.

[0076] In one of the embodiments, the method for determining the rotation period includes: determining a turn-off ratio parameter according to the turn-off quantity and the total number of IGCT devices in the bridge arm; and determining the rotation period according to the turn-off ratio parameter.

[0077] Among them, when there is no common divisor other than 1 between the number of shutdowns and the total number of IGCT devices in the bridge arm, the numerator of the shutdown ratio parameter is the number of shutdowns, and the denominator is the total number of IGCT devices. The corresponding rotation period setting is consistent with the total number of IGCT devices. When there is a common divisor other than 1 between the number of shutdowns and the total number of IGCT devices in the bridge arm, the numerator of the shutdown ratio parameter is the value obtained by dividing the number of shutdowns by the common divisor, and the denominator is the value obtained by dividing the total number of IGCT devices by the common divisor. At this time, the denominator can be used as the rotation period, but the IGCT devices in the bridge arm need to be grouped, and each group of IGCT devices needs to be turned off or turned on at the same time, and the number is consistent with the common divisor.

[0078] For ease of understanding, the following explanation is given with the total number of IGCT devices being 10. In one embodiment, if the number of shutdowns is 7, then the shutdown ratio parameter is 7 / 10, and the corresponding rotation period is 10. Each time an active commutation task is performed, 7 non-identical IGCT devices need to be shut down, and eventually, 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 period is 5. At this time, 10 IGCT devices need to be grouped in pairs. Each time an active commutation task is performed, 3 groups of non-completely identical IGCT devices need to be shut down. Finally, after 5 rotations, each group of IGCT devices is shut down three times, and each IGCT device accumulates 3Q of heat.

[0080] It should be understood that, although the various steps in the flowcharts involved in the above-mentioned embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps does not have a strict order restriction, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-mentioned embodiments can include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0081] Based on the same inventive concept, the embodiment of the present application also provides a current source converter operation device for implementing the current source converter operation method involved above. The implementation scheme for solving the problem provided by the device is similar to the implementation scheme recorded in the above method, so the specific limitations of one or more current source converter operation device embodiments provided below can refer to the limitations of the current source converter operation method above, and will not be repeated here.

[0082] See also Figure 8 , a current source converter operating device, including a shutdown quantity acquisition module 802 and a rotation shutdown module 804.

[0083] The shutdown number acquisition module 802 is used to obtain the shutdown number of IGCT devices that need to be shut down when the same bridge arm of the current source converter meets the active commutation requirement under a single active commutation task. The rotation shutdown module 804 is used to control the shutdown of the IGCT devices of the shutdown number in turn when the same bridge arm performs an active commutation task each time, so that the shutdown times of each IGCT device in the same bridge arm in one rotation cycle are consistent.

[0084] In one of the embodiments, the shutdown quantity acquisition module 802 is also used to obtain the AC line voltage peak value under normal operating conditions of the current source converter and the clamping voltage of the protection circuit; based on the AC line voltage peak value and the clamping voltage, determine the shutdown quantity of IGCT devices that need to be shut down in the same bridge arm to meet the active commutation requirements under a single active commutation task.

[0085] In one of the embodiments, the shutdown number acquisition module 802 is also used to determine the shutdown voltage corresponding to different pre-shutdown numbers based on the pre-shutdown number and the clamping voltage; when the shutdown voltage is greater than the peak value of the AC line voltage, the corresponding pre-shutdown number is used as the shutdown number of IGCT devices that need to be shut down in the same bridge arm to meet the active commutation requirement under a single active commutation task.

[0086] In one of the embodiments, the shutdown quantity acquisition module 802 is also used to obtain the required bridge arm withstand voltage for the same bridge arm to perform a single active commutation task; based on the total bridge arm withstand voltage that can be provided by the same bridge arm and the required bridge arm withstand voltage, the shutdown quantity of the IGCT devices that need to be turned off to meet the active commutation requirements is determined.

[0087] In one of the embodiments, the shutdown number acquisition module 802 is also used to determine the bridge arm withstand voltage corresponding to different pre-shutdown numbers based on the total bridge arm withstand voltage that can be provided by the same bridge arm and the pre-shutdown number; when the bridge arm withstand voltage is greater than the required bridge arm withstand voltage, the corresponding pre-shutdown number is used as the shutdown number of IGCT devices that need to be shut down when the same bridge arm meets the active commutation requirement under a single active commutation task.

[0088] See also Fig. 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 obtain the operating state parameters of the current source converter; when it is determined according to the operating state parameters that an external AC fault has occurred, the active commutation operating state is entered.

[0090] Each module in the above-mentioned current source converter operation device can be implemented in whole or in part by software, hardware and a combination thereof. Each of the above-mentioned modules can be embedded in or independent of a processor in a computer device in the form of hardware, or can be stored in a memory in a computer device in the form of software, so that the processor can call and execute the operations corresponding to each of the above modules.

[0091] The above-mentioned current source converter operation device can obtain the number of IGCT devices that need to be turned off when the same bridge arm meets the active commutation requirement under a single active commutation task. When the current source converter has an active commutation requirement, the same bridge arm controls the number of IGCT devices to be turned off in turn each time the active commutation task is performed. Finally, after completing a rotation cycle, the number of times all IGCT devices in the same bridge arm are turned off is consistent. In this way, the commutation function can be achieved by turning off a smaller number of IGCT devices each time the bridge arm of the current source converter performs an active commutation task. In addition, each time the commutation task is performed, the turned-off IGCT devices are rotated, and all IGCT devices do not need to be turned off each time the commutation is performed, so as to achieve the equalization of the heat of the IGCT device shutdown. Through the above-mentioned scheme, when the bridge arm performs the active commutation task, the accumulation of the shutdown heat of each IGCT device can be reduced, the service life of the IGCT can be increased, the number of times the bridge arm of the current source converter is actively turned off can be increased, and the ability of the current source converter to resist commutation failure can be improved.

[0092] Please refer to Figure 1 The present 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 in the figure), the bridge arm power unit 10 is connected to a DC power supply (not shown in the figure) through the DC smoothing reactor Ldc, and the bridge arm power unit 10 is connected to an AC power supply (not shown in the figure) through a converter transformer; the bridge arm power unit 10 includes multiple bridge arms, each bridge arm includes multiple IGCT units 20 connected in series, each IGCT unit 20 includes an IGCT device 22, and a protection circuit 21 connected in parallel at both ends of 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-mentioned current source converter operation method.

[0093] Specifically, the current source converter operation method is specifically as shown in the above-mentioned embodiments and drawings, and will not be repeated here. Through the current source converter, the number of IGCT devices 22 that need to be turned off when the same bridge arm meets the active commutation requirement under a single active commutation task can be obtained. When the current source converter has an active commutation requirement, each time the same bridge arm performs an active commutation task, the IGCT devices 22 that are turned off are controlled to be turned off in turn. Finally, after completing a rotation cycle, the number of times all IGCT devices 22 in the same bridge arm are turned off is consistent. In this way, the commutation function can be realized 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. In addition, each time the commutation task is performed, the IGCT devices 22 that are turned off are rotated, and it is not necessary for all IGCT devices 22 to be turned off at each commutation, so as to achieve the equalization of the heat of the IGCT devices 22 being turned off. Through the above scheme, when the bridge arm performs active commutation tasks, the shutdown heat accumulation of each IGCT device 22 can be reduced, the service life of the IGCT can be increased, the number of active shutdowns of the current source converter bridge arm can be increased, and the ability of the current source converter to resist commutation failure can be improved.

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

[0095] Specifically, in the solution of this embodiment, the protection circuit 21 includes a buffer circuit 211 and a lightning arrester RS ​​connected in parallel, which can effectively prevent overvoltage from being generated at both ends of the IGCT device 22 during the operation of the current source converter, thereby improving the operation safety of the IGCT device 22. It can be 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, and the buffer circuit 211 can suppress the replenishment of the shutdown overvoltage.

[0096] In the description of this specification, the description with reference to the terms "some embodiments", "other embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic description of the above terms does not necessarily refer to the same embodiment or example.

[0097] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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 above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A method for operating a current source converter, characterized in that: include: Obtaining the number of IGCT devices that need to be turned off to meet the active commutation requirement in the same bridge arm of the current source converter under a single active commutation task; wherein each of the bridge arms includes a plurality of IGCT units connected in series, each of the IGCT units includes an IGCT device, and a protection circuit connected in parallel at both ends of the IGCT device, and the number of IGCT devices that need to be turned off is less than the total number of IGCT devices in the bridge arm; Each time the same bridge arm performs an active commutation task, the IGCT devices of the shut-down number are controlled to be shut down in turn, so that the shut-down times of the IGCT devices in the same bridge arm within one rotation cycle are consistent; wherein the IGCT devices shut down for each active commutation task are not completely the same.

2. The current source converter operation method according to claim 1, characterized in that: The method for obtaining the number of IGCT devices to be turned off when the same bridge arm of the current source converter meets the active commutation requirement under 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; According to the AC line voltage peak value and the clamping voltage, the number of IGCT devices that need to be turned off in the same bridge arm to meet the active commutation requirement under a single active commutation task is determined.

3. The current source converter operation method according to claim 2, characterized in that: The step of determining, according to the AC line voltage peak value and the clamping voltage, the number of IGCT devices to be turned off that need to be turned off when the same bridge arm meets the active commutation requirement under a single active commutation task comprises: Determining the shutdown voltages corresponding to different pre-shutdown numbers according to the pre-shutdown number 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 shutdown quantity of the IGCT devices that need to be shut down in the same bridge arm to meet the active commutation requirement under a single active commutation task.

4. The current source converter operation method according to claim 1, characterized in that: The method for obtaining the number of IGCT devices to be turned off when the same bridge arm of the current source converter meets the active commutation requirement under a single active commutation task includes: Obtain the required bridge arm withstand voltage for the same bridge arm to perform a single active commutation task; The number of IGCT devices that need to be turned off to meet the active commutation requirement is determined according to the total bridge arm withstand voltage that can be provided by the same bridge arm and the required bridge arm withstand voltage.

5. The current source converter operation method according to claim 4, characterized in that: The determining, based on the total bridge arm withstand voltage that can be provided by the same bridge arm and the required bridge arm withstand voltage, the number of IGCT devices that need to be turned off when meeting the active commutation requirement includes: According to the total bridge arm withstand voltage and the number of pre-shutdowns that can be provided by the same bridge arm, the bridge arm withstand voltage corresponding to different pre-shutdown numbers is determined; When the bridge arm withstand voltage is greater than the required bridge arm withstand voltage, the corresponding pre-shutdown quantity is used as the shutdown quantity of IGCT devices that need to be shut down when the same bridge arm meets the active commutation requirement under a single active commutation task.

6. The current source converter operation method according to any one of claims 1 to 5, characterized in that: The current source converter operation method further comprises: Obtaining operating status parameters of the current source converter; When it is determined according to the operating state parameters that an external AC fault occurs, the active commutation operating state is entered.

7. The current source converter operation method according to any one of claims 1 to 5, characterized in that: The method for determining the rotation period includes: Determining a turn-off ratio parameter according to the turn-off quantity and the total number of IGCT devices in the bridge arm; The rotation period is determined according to the shutdown ratio parameter.

8. A current source converter operating device, characterized in that: include: A shutdown number acquisition module, used for acquiring the shutdown number of IGCT devices that need to be shut down when the same bridge arm of the current source converter meets the active commutation requirement under a single active commutation task; wherein each of the bridge arms includes a plurality of IGCT units connected in series, each of the IGCT units includes an IGCT device, and a protection circuit connected in parallel at both ends of the IGCT device, and the shutdown number is less than the total number of IGCT devices in the bridge arm; The rotation shutdown module is used to control the shutdown of the IGCT devices of the number of shutdowns in turn when the same bridge arm performs an active commutation task each time, so that the number of shutdown times of each IGCT device in the same bridge arm within a rotation cycle is consistent; wherein the IGCT devices shut down for 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, wherein 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 of the bridge arms includes multiple IGCT units connected in series, each of the IGCT units includes an IGCT device, and a protection circuit connected in parallel at both ends of 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 described in 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 lightning arrester connected in parallel.

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