Converter precharging method and device

Abstract

The present application relates to a converter precharging method, apparatus, computer equipment, storage medium, and computer program product. The method comprises: upon completion of the uncontrolled charging phase of the converter, bypassing a first number of full-bridge submodules to enter a first active charging phase; upon completion of the first active charging phase, locking the first number of full-bridge submodules and bypassing a second number of full-bridge submodules to enter a second active charging phase; upon completion of the second active charging phase, bypassing the half-bridge submodules and the second number of full-bridge submodules to enter a third active charging phase; upon completion of the third active charging phase, bypassing the converter AC-side charging resistor to complete precharging. This method can reduce the charging time and charging circuit cost of the entire precharging process.

Description

Technical Field

[0001] The present application relates to the field of power transmission technology, and in particular to a converter pre-charging method and device. Background Art

[0002] Flexible DC technology is an important technical means to solve the problems of long-distance, large-capacity power transmission and large-scale renewable energy access. In the field of flexible DC technology, modular multilevel converters (MMCs) are important devices for achieving AC-DC conversion. Currently, the MMC topology that has been widely used in the power industry is mainly based on half-bridge submodules. However, MMCs based on half-bridge submodules cannot achieve self-clearing of DC fault currents, so DC circuit breakers must be added to the DC grid, which in turn increases the construction cost of the DC grid. In view of this, considering the converter cost and fault clearing capability, hybrid modular multilevel converters (hereinafter referred to as hybrid MMCs) based on a combination of half-bridge and full-bridge bridge arms have become a current research hotspot and have good development prospects.

[0003] Due to the existence of the full-bridge submodule, the pre-charging strategy of the hybrid MMC is more complicated than that of the traditional half-bridge submodule, so there is a problem of increasing the cost of the AC side charging circuit. Summary of the Invention

[0004] Based on this, it is necessary to provide a converter pre-charging method, device, computer equipment, computer-readable storage medium and computer program product to address the above technical problems.

[0005] In a first aspect, the present application provides a method for precharging a converter. The method comprises:

[0006] When the uncontrolled charging phase of the converter is completed, the first number of full-bridge submodules are bypassed and the first active charging phase begins; the first active charging phase includes charging the half-bridge submodules and the second number of full-bridge submodules using an AC side power supply;

[0007] When the first active charging phase is completed, the first number of full-bridge submodules are locked and the second number of full-bridge submodules are bypassed before entering the second active charging phase; the second active charging phase includes charging the half-bridge submodules and the first number of full-bridge submodules using an AC power supply;

[0008] When the second active charging stage is completed, the half-bridge submodule and the second number of full-bridge submodules are bypassed, and then the third active charging stage is entered; the third active charging stage includes charging the first number of full-bridge submodules using an AC side power supply;

[0009] When the third stage of active charging is completed, the charging resistor on the AC side of the converter is bypassed to complete pre-charging.

[0010] In one embodiment, before the step of bypassing the first number of full-bridge sub-modules when the uncontrolled charging phase of the converter is completed, the step includes:

[0011] Obtaining a first per-unit voltage value of the half-bridge submodule in the uncontrolled charging phase, and obtaining a second per-unit voltage value of the full-bridge submodule in the uncontrolled charging phase;

[0012] Whether the uncontrolled charging stage is completed is determined according to a ratio of the first voltage per unit value to the second voltage per unit value.

[0013] In one embodiment, it further includes:

[0014] If the second voltage per unit value is a first multiple of the first voltage per unit value, it is determined that the uncontrolled charging stage is completed; the first multiple includes 2.

[0015] In one embodiment, before the step of locking the first number of full-bridge sub-modules upon completion of the first stage of active charging, the step includes:

[0016] Obtaining a third per-unit voltage value of the half-bridge sub-module in the first active charging stage;

[0017] Whether the first stage of active charging is completed is determined based on a ratio of the third voltage per unit value to the rated value.

[0018] In one embodiment, it further includes:

[0019] If the third voltage per unit value is a second multiple of the rated value, it is determined that the first stage of active charging is completed; the second multiple includes 0.5 times.

[0020] In one embodiment, before the step of bypassing the half-bridge sub-module and the second number of full-bridge sub-modules when the second stage of active charging is completed, the step includes:

[0021] Obtaining a fourth per-unit voltage value of the half-bridge sub-module in the second active charging stage;

[0022] Whether the second stage of active charging is completed is determined based on a comparison relationship between the fourth voltage per unit value and the rated value.

[0023] In one embodiment, it further includes:

[0024] If the fourth voltage per unit value is equal to the rated value, it is determined that the second stage of active charging is completed.

[0025] In one embodiment, when the third stage of active charging is completed, the step of bypassing the charging resistor on the AC side of the converter includes:

[0026] Obtaining a fifth per-unit voltage value of the full-bridge submodule in the third stage of active charging;

[0027] Whether the third stage of active charging is completed is determined based on a comparison relationship between the fifth voltage per unit value and the rated value.

[0028] In one embodiment, it further includes:

[0029] If the fifth voltage per unit value is equal to the rated value, the half-bridge sub-module and the second number of full-bridge sub-modules are locked, and it is determined that the third stage of active charging is completed.

[0030] In a second aspect, the present application further provides a converter pre-charging device. The device comprises:

[0031] A first active charging module is configured to bypass a first number of full-bridge submodules upon completion of the uncontrolled charging phase of the converter, thereby entering a first active charging phase; the first active charging phase includes charging the half-bridge submodules and the second number of full-bridge submodules using an AC power supply;

[0032] a second active charging module, configured to, upon completion of the first active charging phase, lock the first number of full-bridge submodules and bypass the second number of full-bridge submodules, before entering a second active charging phase; the second active charging phase comprising charging the half-bridge submodules and the first number of full-bridge submodules using an AC power supply;

[0033] A third active charging module is configured to, upon completion of the second active charging stage, bypass the half-bridge submodule and the second number of full-bridge submodules to enter a third active charging stage; the third active charging stage includes charging the first number of full-bridge submodules using an AC-side power supply; and is further configured to, upon completion of the third active charging stage, bypass the converter AC-side charging resistor to complete pre-charging.

[0034] In a third aspect, the present application further provides a computer device. The computer device includes a memory and a controller, wherein the memory stores a computer program, and when the controller executes the computer program, the following steps are implemented:

[0035] When the uncontrolled charging phase of the converter is completed, the first number of full-bridge submodules are bypassed and the first active charging phase begins; the first active charging phase includes charging the half-bridge submodules and the second number of full-bridge submodules using an AC side power supply;

[0036] When the first active charging phase is completed, the first number of full-bridge submodules are locked and the second number of full-bridge submodules are bypassed before entering the second active charging phase; the second active charging phase includes charging the half-bridge submodules and the first number of full-bridge submodules using an AC power supply;

[0037] When the second active charging stage is completed, the half-bridge submodule and the second number of full-bridge submodules are bypassed, and then the third active charging stage is entered; the third active charging stage includes charging the first number of full-bridge submodules using an AC side power supply;

[0038] When the third stage of active charging is completed, the charging resistor on the AC side of the converter is bypassed to complete pre-charging.

[0039] In a fourth aspect, the present application further provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the following steps:

[0040] When the uncontrolled charging phase of the converter is completed, the first number of full-bridge submodules are bypassed and the first active charging phase begins; the first active charging phase includes charging the half-bridge submodules and the second number of full-bridge submodules using an AC side power supply;

[0041] When the first active charging phase is completed, the first number of full-bridge submodules are locked and the second number of full-bridge submodules are bypassed before entering the second active charging phase; the second active charging phase includes charging the half-bridge submodules and the first number of full-bridge submodules using an AC power supply;

[0042] When the second active charging stage is completed, the half-bridge submodule and the second number of full-bridge submodules are bypassed, and then the third active charging stage is entered; the third active charging stage includes charging the first number of full-bridge submodules using an AC side power supply;

[0043] When the third stage of active charging is completed, the charging resistor on the AC side of the converter is bypassed to complete pre-charging.

[0044] In a fifth aspect, the present application further provides a computer program product. The computer program product includes a computer program that, when executed by a processor, implements the following steps:

[0045] When the uncontrolled charging phase of the converter is completed, the first number of full-bridge submodules are bypassed and the first active charging phase begins; the first active charging phase includes charging the half-bridge submodules and the second number of full-bridge submodules using an AC side power supply;

[0046] When the first active charging phase is completed, the first number of full-bridge submodules are locked and the second number of full-bridge submodules are bypassed before entering the second active charging phase; the second active charging phase includes charging the half-bridge submodules and the first number of full-bridge submodules using an AC power supply;

[0047] When the second active charging stage is completed, the half-bridge submodule and the second number of full-bridge submodules are bypassed, and then the third active charging stage is entered; the third active charging stage includes charging the first number of full-bridge submodules using an AC side power supply;

[0048] When the third stage of active charging is completed, the charging resistor on the AC side of the converter is bypassed to complete pre-charging.

[0049] The above-mentioned converter precharging method, device, computer equipment, storage medium and computer program product enter the first stage of active charging after bypassing the first number of full-bridge sub-modules when the uncontrolled charging stage of the converter is completed; enter the second stage of active charging after locking the first number of full-bridge sub-modules and bypassing the second number of full-bridge sub-modules when the first stage of active charging is completed; enter the third stage of active charging after bypassing the half-bridge sub-modules and the second number of full-bridge sub-modules when the second stage of active charging is completed; and bypass the AC side charging resistor of the converter when the third stage of active charging is completed, thereby completing precharging; the present application utilizes effective full-bridge sub-module grouping in the active charging stage of the converter, so that the half-bridge sub-module can provide driving energy for the power electronic switch after the first stage of active charging is completed, and effectively reduces the dependence of the half-bridge sub-module on the AC side charging resistor during the active charging stage, thereby reducing the charging time and charging circuit cost of the entire pre-charging process. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Schematic diagram of the topological structure of a hybrid MMC in one embodiment;

[0051] Figure 2 1 is a flow chart of a converter precharging method according to an embodiment;

[0052] Figure 3 Schematic diagram of a specific flow chart of a hybrid MMC pre-charging method according to an embodiment;

[0053] Figure 4 FIG. 1 is a schematic structural diagram of a converter pre-charging device in one embodiment. DETAILED DESCRIPTION

[0054] To facilitate understanding of the present application, the present application will be described more fully below with reference to the accompanying drawings. The accompanying drawings provide embodiments of the present application. However, the present application may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to make the disclosure of the present application more thorough and comprehensive.

[0055] 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 pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0056] Figure 1 The figure shows the topology of a hybrid MMC, wherein the hybrid MMC includes three phase units, each phase unit includes an upper bridge arm and a lower bridge arm with the same structure, and each bridge arm includes a half-bridge submodule, a full-bridge submodule and a bridge arm reactor L; ga Indicates the AC grid phase A voltage, v gb Indicates the AC grid phase B voltage, v gc represents the phase C voltage of the AC grid, B1 represents the AC disconnect switch, B2 represents the switching switch, and R1 represents the AC side charging resistor;

[0057] The conventional pre-charging strategies of hybrid MMCs include uncontrolled charging, active half-controlled charging, and active unlocked charging. Among them, after the uncontrolled charging is completed, due to the low capacitor voltage of the half-bridge sub-module in the hybrid MMC, there is a possibility that the switching devices of the sub-module cannot be provided with driving energy. Therefore, in the conventional active half-controlled charging strategy of the hybrid MMC, it is necessary to bypass all the full-bridge sub-modules in the hybrid MMC and charge the half-bridge sub-module separately so that its voltage is equal to the capacitor voltage of the full-bridge sub-module after uncontrolled charging. However, this operation is more applicable in hybrid MMCs where the proportion of half-bridge sub-modules is relatively high.

[0058] However, in hybrid MMCs where the proportion of half-bridge sub-modules is low, due to the small number of half-bridge sub-modules in each bridge arm, in order to ensure the controllability of the operation and avoid overcharging of the half-bridge sub-modules during the process, it is usually necessary to select a large AC side charging resistor R1, which prolongs the entire charging process and increases the cost of the AC side charging circuit.

[0059] The converter pre-charging method provided in this application can complete the pre-charging of the converter through reasonable group charging, relying only on uncontrolled charging and active semi-controlled charging, and effectively reduce the charging resistance value required for pre-charging of the AC side of the converter, thereby reducing the charging time of the entire pre-charging process and the construction cost of the charging circuit.

[0060] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0061] The converter pre-charging method provided in the embodiment of the present application can be applied to Figure 1 In the application environment shown.

[0062] In one embodiment, Figure 2 As shown, a converter pre-charging method is provided, which is applied to Figure 1 Taking the hybrid MMC in the example as an example, the following steps may be included:

[0063] Step S210: After the uncontrolled charging phase of the converter is completed, the first number of full-bridge submodules are bypassed and the first active charging phase begins. The first active charging phase includes charging the half-bridge submodules and the second number of full-bridge submodules using an AC power supply.

[0064] Step S220: After the first active charging phase is completed, the first number of full-bridge submodules are locked and the second number of full-bridge submodules are bypassed, and then the second active charging phase begins. The second active charging phase includes charging the half-bridge submodules and the first number of full-bridge submodules using an AC power supply.

[0065] Step S230, when the second active charging phase is completed, bypassing the half-bridge submodules and the second number of full-bridge submodules, and then entering the third active charging phase; the third active charging phase includes charging the first number of full-bridge submodules using an AC power supply;

[0066] Step S240: When the third stage of active charging is completed, the charging resistor on the AC side of the converter is bypassed to complete pre-charging.

[0067] Specifically, the converter Figure 1 Taking the hybrid MMC in the example, first put the hybrid MMC AC side charging resistor R1 into the hybrid MMC, that is, close the switch B2, and use the AC side power supply to charge the hybrid MMC uncontrolled. Further, all full-bridge sub-modules and all half-bridge sub-modules in the hybrid MMC are charged uncontrolled. In some examples, N H Indicates the number of half-bridge submodules in each bridge arm of the hybrid MMC, N F Indicates the number of full-bridge submodules in each bridge arm;

[0068] When the uncontrolled charging stage is completed, after the first number of full-bridge submodules are bypassed, the first active charging stage is entered. The first active charging stage may include using the AC side power supply to charge all half-bridge submodules and the second number of full-bridge submodules in the hybrid MMC; in some examples, the full-bridge submodules in each bridge arm can be divided into two groups, the first number being the number of submodules in one group, and the second number being the number of submodules in the other group. Further, N by Represents the first quantity, namely N by The number of full-bridge submodules that need to be bypassed in each bridge arm of the hybrid MMC in the first stage of active charging is (N F -N by ) represents the second quantity, that is, (N F -N by ) is the number of full-bridge submodules that do not need to be operated in each bridge arm during the first phase of active charging;

[0069] When the first stage of active charging is completed, the N by Full-bridge submodules, and bypass (N F -N by ) full-bridge sub-modules, it enters the second stage of active charging, and the AC side power supply can be used to charge all the half-bridge sub-modules and N by A full-bridge submodule is used for charging;

[0070] When the second stage of active charging is completed, all half-bridge submodules and (N F -N by After the full-bridge sub-modules are bypassed, the third stage of active charging is entered, and the AC side power supply can be used to charge N by Full-bridge sub-modules are charged, and further, N by The full-bridge submodules whose voltage value is not the rated value are charged;

[0071] When the third stage of active charging is completed, the AC side charging resistor R1 of the hybrid MMC is bypassed, that is, the AC isolation switch B1 is closed to complete the entire pre-charging process of the hybrid MMC.

[0072] In the above converter precharging method, by rationally charging the hybrid MMCs in groups, the dependence of the hybrid MMC precharging process on the AC side charging resistor is reduced, so that the charging circuit can use a smaller charging resistor, thereby reducing the construction cost of the charging circuit and shortening the precharging time of the hybrid MMC.

[0073] In one embodiment, when the uncontrolled charging phase of the converter is completed, the step of bypassing the first number of full-bridge sub-modules includes:

[0074] Obtaining a first per-unit voltage value of the half-bridge submodule in an uncontrolled charging phase, and obtaining a second per-unit voltage value of the full-bridge submodule in an uncontrolled charging phase;

[0075] Whether the uncontrolled charging phase is completed is determined based on a ratio of the first voltage per unit value to the second voltage per unit value.

[0076] Specifically, the converter Figure 1 Taking the hybrid MMC in the example, in the uncontrolled charging stage of the hybrid MMC, the first voltage per unit value of the half-bridge submodule is obtained, and the second voltage per unit value of the full-bridge submodule is obtained, so as to determine whether the uncontrolled charging stage is completed according to the ratio of the first voltage per unit value to the second voltage per unit value.

[0077] In one embodiment, it further includes:

[0078] If the second voltage per unit value is a first multiple of the first voltage per unit value, it is determined that the uncontrolled charging stage is completed; the first multiple includes 2.

[0079] Specifically, taking the first voltage per unit value being the first voltage per unit value of the hybrid MMC half-bridge submodule and the second voltage per unit value being the second voltage per unit value of the hybrid MMC full-bridge submodule as an example, if the second voltage per unit value is a first multiple of the first voltage per unit value, it is determined that the uncontrolled charging stage is completed, otherwise, the hybrid MMC continues to wait for uncontrolled charging, wherein the first multiple may include 2 times;

[0080] In some examples, the capacitor voltage of the half-bridge submodule in the hybrid MMC can be expressed as V H_unc Indicates that the capacitor voltage of the full-bridge submodule can be expressed as V F_unc Indicates that, further, V H_unc and V F_unc They can be calculated by the following formula (1):

[0081]

[0082] In formula (1), U lineis the effective value of the AC line voltage of the active network connected to the hybrid MMC; Based on formula (1), it can be seen that the capacitor voltage of the full-bridge submodule is twice the capacitor voltage of the half-bridge submodule. At the same time, considering the relationship between the DC voltage of the hybrid MMC and the effective value of the AC line voltage, the first voltage per unit value of the half-bridge submodule can be expressed as V H_unc_p.u. , the second voltage per unit value of the full-bridge submodule can be expressed as V F_unc_p.u. , further, V H_unc_p.u. and V F_unc_p.u. They can be calculated by the following formula (2):

[0083]

[0084] In some examples, the proportion of the half-bridge submodule in the hybrid MMC can be (0, 0.5]. Furthermore, through formula (2), it can be obtained that the second voltage per unit value of the full-bridge submodule in the hybrid MMC is 0.35 to 0.57 times the per unit value, and the first voltage per unit value of the half-bridge submodule is 0.175 to 0.28 times the per unit value. Since in power engineering, the condition for the hybrid MMC to achieve self-energy extraction of the submodule is usually that the capacitor voltage of the submodule is 0.3 times the rated voltage value, therefore, after the uncontrolled charging stage is completed, in the hybrid MMC, only the full-bridge submodule can achieve self-energy extraction of the switching device and realize the unlocking control of the submodule.

[0085] In one embodiment, when the first stage of active charging is completed, before the step of locking the first number of full-bridge sub-modules, the step includes:

[0086] Obtaining a third voltage per unit value of the half-bridge sub-module in the first stage of active charging;

[0087] Whether the first stage of active charging is completed is determined based on a ratio of the third voltage per unit value to the rated value.

[0088] Specifically, the converter Figure 1 Taking the hybrid MMC in FIG as an example, in the first stage of active charging of the hybrid MMC, the third voltage per unit value of the half-bridge submodule is obtained, so as to determine whether the first stage of active charging of the hybrid MMC is completed according to the ratio of the third voltage per unit value to the rated value.

[0089] In one embodiment, it further includes:

[0090] If the third voltage per unit value is a second multiple of the rated value, it is determined that the first stage of active charging is completed; the second multiple includes 0.5 times.

[0091] Specifically, taking the third voltage per unit value of the hybrid MMC half-bridge submodule as an example, further, if the third voltage per unit value of the hybrid MMC half-bridge submodule is a second multiple of the rated value, it is determined that the first stage of active charging of the hybrid MMC is completed, otherwise, the hybrid MMC continues to wait for the first stage of active charging; wherein the second multiple may include 0.5 times;

[0092] In some examples, the third voltage per unit value of the hybrid MMC half-bridge submodule can be represented by V H_主动1_p.u. Indicates that, accordingly, the voltage per unit value of the full-bridge submodule can be expressed as V F_主动1_p.u. express;

[0093] In a specific example, after the first stage of active charging of the hybrid MMC is completed, the third voltage per unit value of the half-bridge submodule is V H_主动1_p.u. , the voltage per unit value of the full bridge module is V F_主动1_p.u. For example, V H_主动1_p.u. and V F_主动1_p.u. It can be calculated by the following formula (3):

[0094]

[0095] If the third voltage per unit value of the half-bridge submodule is V H_主动1_p.u. is 0.5 times the rated value. At this time, the half-bridge sub-module can provide driving energy for the switching device. According to the above formula (3), the capacitor voltage of the full-bridge sub-module that is not bypassed in the hybrid MMC reaches the rated value, that is, V F_主动1_p.u. Satisfies the following formula (4):

[0096]

[0097] From the above formula (4), we can see that the first number N by It can be calculated by the following formula (5):

[0098]

[0099] According to formula (5), the ratio of the number of bypassed full-bridge submodules to the total number of bridge arm submodules in the first stage of active charging is 0.27-0.64, that is, the ratio of the number of unlocked full-bridge submodules to the total number of bridge arm submodules is 0.23-0.36.

[0100] In one embodiment, when the second stage of active charging is completed, the step of bypassing the half-bridge sub-module and the second number of full-bridge sub-modules includes:

[0101] Obtaining a fourth per-unit voltage value of the half-bridge sub-module in the second stage of active charging;

[0102] Whether the second stage of active charging is completed is determined based on a comparison relationship between the fourth voltage per unit value and the rated value.

[0103] Specifically, the converter Figure 1 For example, when the hybrid MMC is charged actively in the first stage, the voltage is set to the rated value (N F -N by ) full-bridge submodules are bypassed, and N by After the full-bridge sub-module is locked, the hybrid MMC enters the second stage of active charging. Further, the fourth voltage per unit value of the half-bridge sub-module is obtained, so as to determine whether the second stage of active charging of the hybrid MMC is completed based on the comparison relationship between the fourth voltage per unit value and the rated value.

[0104] In one embodiment, it further includes:

[0105] If the fourth voltage per unit value is equal to the rated value, it is determined that the second stage of active charging is completed.

[0106] Specifically, taking the fourth voltage per unit value as the fourth voltage per unit value of the hybrid MMC half-bridge sub-module as an example, if the fourth voltage per unit value of the hybrid MMC half-bridge sub-module reaches the rated value, it is determined that the hybrid MMC completes the second stage of active charging; otherwise, the hybrid MMC continues to wait for the second stage of active charging.

[0107] In one embodiment, when the third stage of active charging is completed, the step of bypassing the charging resistor on the AC side of the converter includes:

[0108] Obtaining a fifth per-unit voltage value of the full-bridge submodule in the third stage of active charging;

[0109] Whether the third stage of active charging is completed is determined based on a comparison relationship between the fifth voltage per unit value and the rated value.

[0110] Specifically, the converter Figure 1 For example, when the hybrid MMC completes the second stage of active charging, the voltage is set to the rated value (N F -N by After all full-bridge sub-modules and all half-bridge sub-modules are bypassed, the hybrid MMC enters the third stage of active charging. Further, the fifth voltage per unit value of the full-bridge sub-module is obtained, so as to determine whether the third stage of active charging of the hybrid MMC is completed based on the comparison relationship between the fifth voltage per unit value and the rated value.

[0111] In one embodiment, it further includes:

[0112] If the fifth voltage per unit value is equal to the rated value, the half-bridge sub-module and the second number of full-bridge sub-modules are locked to determine that the third stage of active charging is completed.

[0113] Specifically, taking the fifth voltage per unit value as the fifth voltage per unit value of the hybrid MMC half-bridge submodule as an example, if the fifth voltage per unit value of the hybrid MMC half-bridge submodule reaches the rated value, that is, the capacitor voltages of all full-bridge submodules and all half-bridge submodules in the hybrid MMC reach the rated value, then all half-bridge submodules and (N F -N by ) full-bridge sub-modules are locked, that is, all sub-modules in the hybrid MMC are locked, and it is determined that the hybrid MMC completes the third stage of active charging, otherwise continue to wait for the hybrid MMC to perform the third stage of active charging.

[0114] In order to better illustrate this application, the converter is used as Figure 1 Taking the hybrid MMC in the example, the specific flow chart of the hybrid MMC pre-charging method is as follows Figure 3 shown.

[0115] like Figure 3 As shown, after the hybrid MMC pre-charging starts, the AC side charging resistor is put into use, and the hybrid MMC enters the uncontrolled charging stage. If the uncontrolled charging stage is completed, the first number of full-bridge sub-modules are bypassed, and the hybrid MMC enters the first active charging stage. Otherwise, it waits until the uncontrolled charging stage is completed. In the first active charging stage, if the third voltage per unit value of the half-bridge sub-module is 0.5 times the rated value, where the rated value is 1, that is, the third voltage per unit value is 0.5, the first number of full-bridge sub-modules are locked, and the second number of full-bridge sub-modules are bypassed, the hybrid MMC enters the second active charging stage. The hybrid MMC enters the second stage of active charging, otherwise waits until the first stage of active charging is completed; in the second stage of active charging, if the fourth voltage per unit value of the half-bridge sub-module is equal to the rated value, that is, the fourth voltage per unit value is 1, then the half-bridge sub-module and the second number of full-bridge sub-modules are bypassed, and the hybrid MMC enters the third stage of active charging, otherwise waits until the second stage of active charging is completed; in the third stage of active charging, if the voltage per unit values ​​of all sub-modules reach the rated value, that is, the voltage per unit values ​​are all 1, then the charging resistor is bypassed to end the pre-charging process of the hybrid MMC, otherwise waits until the third stage of active charging is completed.

[0116] In the above-mentioned converter precharging method, by effectively grouping the full-bridge sub-modules during the active charging stage of the hybrid MMC, the voltage of the full-bridge sub-module is increased to the rated value while the half-bridge sub-module is continuously charged, ensuring that the capacitor voltage of the half-bridge sub-module can provide driving energy for the power electronic switch after the first stage of active charging is completed, thereby effectively reducing the dependence of the half-bridge sub-module on the AC side charging resistor during the charging stage, improving the economy of the hybrid MMC charging circuit construction, and reducing the charging time of the entire pre-charging process.

[0117] It should be understood that, although the various steps in the flowcharts involved in the various embodiments described above are displayed in sequence according to the instructions of the arrows, these steps are not necessarily executed in sequence in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the flowcharts involved in the various embodiments described above can include multiple steps or multiple stages, and these steps or stages are not necessarily executed and completed 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 portion of steps or stages in other steps.

[0118] Based on the same inventive concept, an embodiment of the present application further provides a converter pre-charging device for implementing the converter pre-charging method described above. The solution provided by this device is similar to the solution described in the method described above. Therefore, the specific limitations of the converter pre-charging device embodiment provided below can be found in the limitations of the converter pre-charging method described above and will not be repeated here.

[0119] In one embodiment, Figure 4 As shown, a converter pre-charging device is provided, comprising: a first active charging module 410, a second active charging module 420 and a third active charging module 430, wherein:

[0120] A first active charging module 410 is configured to bypass a first number of full-bridge submodules and enter a first active charging phase after the uncontrolled charging phase of the converter is completed. The first active charging phase includes charging the half-bridge submodules and the second number of full-bridge submodules using an AC power supply.

[0121] The second active charging module 420 is configured to lock the first number of full-bridge submodules and bypass the second number of full-bridge submodules upon completion of the first active charging phase, before entering the second active charging phase. The second active charging phase includes charging the half-bridge submodules and the first number of full-bridge submodules using an AC power supply.

[0122] The third active charging module 430 is used to bypass the half-bridge submodule and the second number of full-bridge submodules after the second active charging stage is completed, and then enter the third active charging stage; the third active charging stage includes charging the first number of full-bridge submodules using the AC side power supply; and is also used to bypass the converter AC side charging resistor to complete pre-charging after the third active charging stage is completed.

[0123] In one embodiment, the first active charging module 410 is further configured to:

[0124] Obtaining a first per-unit voltage value of the half-bridge submodule in an uncontrolled charging phase, and obtaining a second per-unit voltage value of the full-bridge submodule in an uncontrolled charging phase;

[0125] Whether the uncontrolled charging phase is completed is determined based on a ratio of the first voltage per unit value to the second voltage per unit value.

[0126] In one embodiment, the first active charging module 410 is further configured to:

[0127] If the second voltage per unit value is a first multiple of the first voltage per unit value, it is determined that the uncontrolled charging stage is completed; the first multiple includes 2.

[0128] In one embodiment, the second active charging module 420 is further configured to:

[0129] Obtaining a third voltage per unit value of the half-bridge sub-module in the first stage of active charging;

[0130] Whether the first stage of active charging is completed is determined based on a ratio of the third voltage per unit value to the rated value.

[0131] In one embodiment, the second active charging module 420 is further configured to:

[0132] If the third voltage per unit value is a second multiple of the rated value, it is determined that the first stage of active charging is completed; the second multiple includes 0.5 times.

[0133] In one embodiment, the third active charging module 430 is further configured to:

[0134] Obtaining a fourth per-unit voltage value of the half-bridge sub-module in the second stage of active charging;

[0135] Whether the second stage of active charging is completed is determined based on a comparison relationship between the fourth voltage per unit value and the rated value.

[0136] In one embodiment, the third active charging module 430 is further configured to:

[0137] If the fourth voltage per unit value is equal to the rated value, it is determined that the second stage of active charging is completed.

[0138] In one embodiment, the third active charging module 430 is further configured to:

[0139] Obtaining a fifth per-unit voltage value of the full-bridge submodule in the third stage of active charging;

[0140] Whether the third stage of active charging is completed is determined based on a comparison relationship between the fifth voltage per unit value and the rated value.

[0141] In one embodiment, the third active charging module 430 is further configured to:

[0142] If the fifth voltage per unit value is equal to the rated value, the half-bridge sub-module and the second number of full-bridge sub-modules are locked to determine that the third stage of active charging is completed.

[0143] Each module in the aforementioned converter pre-charging device may be implemented in whole or in part through software, hardware, or a combination thereof. Each module may be embedded in or independent of a processor in a computer device in hardware form, or may be stored in a computer device memory in software form, so that the processor can call and execute the corresponding operations of each module.

[0144] In one embodiment, a computer device is provided, which may be a server. The computer device includes a processor, a memory, and a network interface connected via a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of the operating system and computer program in the non-volatile storage medium. The database of the computer device is used to store data such as a first voltage per unit value and a second voltage per unit value. The network interface of the computer device is used to communicate with an external terminal via a network connection. When the computer program is executed by the processor, a converter precharging method is implemented.

[0145] In one embodiment, a computer device is provided, which may be a terminal. The computer device includes a processor, memory, a communication interface, a display screen, and an input device connected via a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and computer program in the non-volatile storage medium. The communication interface of the computer device is used to communicate with an external terminal via wired or wireless communication, where the wireless communication may be achieved via Wi-Fi, a mobile cellular network, NFC (near field communication), or other technologies. When executed by the processor, the computer program implements a method for precharging an inverter. The display screen of the computer device may be a liquid crystal display or an electronic ink display screen. The input device of the computer device may be a touch layer covering the display screen, or may be a key, trackball, or touchpad provided on the computer device housing, or may be an external keyboard, touchpad, or mouse.

[0146] In one embodiment, a computer device is provided, including a memory and a controller. The memory stores a computer program, and the controller implements the steps in the above method embodiments when executing the computer program.

[0147] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps in the above-mentioned method embodiments are implemented.

[0148] In one embodiment, a computer program product is provided, including a computer program, which implements the steps in the above method embodiments when executed by a processor.

[0149] Those skilled in the art will appreciate that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, database or other media used in the embodiments provided in this application may include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory may include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in the various embodiments provided herein may include at least one of a relational database and a non-relational database. Non-relational databases may include, but are not limited to, distributed databases based on blockchains. The processor involved in the various embodiments provided herein may be, but are not limited to, a general-purpose processor, a central processing unit, a graphics processing unit, a digital signal processor, a programmable logic unit, a data processing logic unit based on quantum computing, and the like.

[0150] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, 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.

[0151] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A converter pre-charging method, characterized in that: The method comprises: Obtaining a first per-unit voltage value of a half-bridge submodule in a converter during an uncontrolled charging phase, and obtaining a second per-unit voltage value of a full-bridge submodule in the converter during the uncontrolled charging phase; When the uncontrolled charging phase is determined to be complete based on the ratio of the first voltage per unit value to the second voltage per unit value, the first number of full-bridge sub-modules are bypassed before entering a first active charging phase; the first active charging phase includes charging the half-bridge sub-modules and the second number of full-bridge sub-modules using an AC power supply; Obtaining a third per-unit voltage value of the half-bridge sub-module in the first active charging stage; If the first stage of active charging is determined to be complete based on the ratio of the third voltage per unit value to the rated value, the first number of full-bridge sub-modules are locked and the second number of full-bridge sub-modules are bypassed before entering the second stage of active charging; the second stage of active charging includes charging the half-bridge sub-modules and the first number of full-bridge sub-modules using an AC power supply; Obtaining a fourth per-unit voltage value of the half-bridge sub-module in the second active charging stage; If the second stage of active charging is determined to be complete based on the comparison relationship between the fourth voltage per unit value and the rated value, the half-bridge sub-module and the second number of full-bridge sub-modules are bypassed before entering a third stage of active charging; the third stage of active charging includes charging the first number of full-bridge sub-modules using an AC power supply; Obtaining a fifth per-unit voltage value of the full-bridge submodule in the third stage of active charging; When it is determined that the third stage of active charging is completed based on the comparison relationship between the fifth voltage per unit value and the rated value, the charging resistor on the AC side of the converter is bypassed to complete pre-charging.

2. The method according to claim 1, characterized in that Also includes: If the second voltage per unit value is a first multiple of the first voltage per unit value, determining that the uncontrolled charging stage is completed; The first multiple includes 2 times.

3. The method according to claim 1, characterized in that Also includes: If the third voltage per unit value is a second multiple of the rated value, determining that the first stage of active charging is completed; The second multiple includes 0.5 times.

4. The method according to claim 1, wherein Also includes: If the fourth voltage per unit value is equal to the rated value, it is determined that the second stage of active charging is completed.

5. The method according to claim 1, wherein Also includes: If the fifth voltage per unit value is equal to the rated value, the half-bridge sub-module and the second number of full-bridge sub-modules are locked, and it is determined that the third stage of active charging is completed.

6. The method according to claim 1, characterized in that The converter is a modular multi-level converter MMC.

7. A converter pre-charging device, characterized in that: The device comprises: a first active charging module, configured to obtain a first per-unit voltage value of a half-bridge submodule in the converter during an uncontrolled charging phase, and to obtain a second per-unit voltage value of a full-bridge submodule in the converter during the uncontrolled charging phase; and upon determining, based on a ratio of the first per-unit voltage value to the second per-unit voltage value, bypassing a first number of full-bridge submodules and entering a first active charging phase. The first active charging phase includes charging the half-bridge submodule and the second number of full-bridge submodules using an AC power supply; a second active charging module, configured to obtain a third per-unit voltage value of the half-bridge submodule in the first active charging phase; and upon determining, based on a ratio between the third per-unit voltage value and a rated value, locking the first number of full-bridge submodules and bypassing the second number of full-bridge submodules, entering a second active charging phase; the second active charging phase comprising charging the half-bridge submodule and the first number of full-bridge submodules using an AC power supply; The third active charging module is used to obtain the fourth voltage per unit value of the half-bridge sub-module in the second stage of active charging; when it is determined that the second stage of active charging is completed based on the comparison relationship between the fourth voltage per unit value and the rated value, the half-bridge sub-module and the second number of full-bridge sub-modules are bypassed, and then the third stage of active charging is entered; the third stage of active charging includes charging the first number of full-bridge sub-modules using an AC side power supply; and is also used to obtain the fifth voltage per unit value of the full-bridge sub-module in the third stage of active charging; when it is determined that the third stage of active charging is completed based on the comparison relationship between the fifth voltage per unit value and the rated value, the converter AC side charging resistor is bypassed to complete pre-charging.

8. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 6 are implemented.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

10. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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