Precharging method and computer equipment for hybrid MMC passive power supply system

Abstract

The present invention relates to a precharging method and computer equipment for a hybrid MMC passive power supply system. The method comprises: performing uncontrolled charging on the AC side of the hybrid MMC passive power supply system until the capacitor voltage of each half-bridge submodule in a first MMC reaches a first voltage threshold and the capacitor voltage of each full-bridge submodule reaches a second voltage threshold; turning on the electronic switches of each full-bridge submodule in the first MMC to perform active charging on the AC side until the DC voltage reaches a third voltage threshold; unlocking a second hybrid MMC to perform a first stage of active DC side charging on the second hybrid MMC; locking the second hybrid MMC to perform voltage balancing on the first hybrid MMC until the DC voltage reaches a rated starting voltage; and performing a second stage of active DC side charging on the second hybrid MMC. The present invention can shorten the charging time of the hybrid MMC passive power supply system, effectively avoid the generation of "black modules" and bypass submodules during the charging process, and reduce the control difficulty of the hybrid MMC.

Description

Technical Field

[0001] The present invention relates to flexible direct current (DC) power transmission and distribution technology, in particular to a precharging method for a hybrid MMC passive power supply system, and also to a computer device, a readable storage medium and a computer program product. Background Art

[0002] Hybrid modular multilevel converters (MMCs), based on a mix of half-bridge and full-bridge submodules, are key converters for building self-clearing DC grids. Due to the presence of full-bridge submodules in each arm, the pre-charging strategy for hybrid MMCs is more complex than that of traditional half-bridge submodules. Consequently, researchers have conducted specialized research on hybrid MMC startup strategies. However, to date, most studies have focused on hybrid MMC AC-side charging strategies, while the DC-side charging strategy has adopted the traditional MMC "module-by-module" approach. While this approach effectively charges the hybrid MMC's DC side in most cases, in some cases, the prolonged pre-charging process can lead to "black modules" that are unable to draw power and bypass submodules due to overvoltage, complicating control and increasing power transmission efficiency. Summary of the Invention

[0003] Based on this, it is necessary to provide a pre-charging method for a hybrid MMC passive power supply system that can avoid the generation of "black modules" and bypass sub-modules during the charging process.

[0004] A pre-charging method for a hybrid MMC passive power supply system, the hybrid MMC passive power supply system comprising a first hybrid MMC on an AC side and a second hybrid MMC on a DC side, an auxiliary resistor connected between the first hybrid MMC and the second hybrid MMC, and an auxiliary isolating switch for controlling the connection of the auxiliary resistor; the first hybrid MMC and the second hybrid MMC each comprising a plurality of submodules, some of which are full-bridge submodules and some of which are half-bridge submodules; the method comprising: in a state where the first hybrid MMC and the second hybrid MMC are locked and the auxiliary isolating switch connects the auxiliary resistor between the first hybrid MMC and the second hybrid MMC, performing uncontrolled AC-side charging on the hybrid MMC passive power supply system until the first hybrid MMC is fully charged. The capacitor voltage of each half-bridge sub-module in an MMC reaches a first voltage threshold, and the capacitor voltage of each full-bridge sub-module reaches a second voltage threshold; after the uncontrolled charging on the AC side is completed, the electronic switches of each full-bridge sub-module in the first MMC are turned on to perform active charging on the AC side until the DC voltage reaches a third voltage threshold; after the active charging on the AC side is completed, the second hybrid MMC is unlocked, and the first stage of active charging on the DC side is performed on the second hybrid MMC; after the first stage of active charging on the DC side is completed, the second hybrid MMC is locked, and voltage balancing is performed on the first hybrid MMC until the DC voltage reaches the rated starting voltage; and the second stage of active charging on the DC side is performed on the second hybrid MMC.

[0005] The pre-charging method of the hybrid MMC passive power supply system is based on the auxiliary resistors on the AC and DC sides of the hybrid MMC, fully utilizes the hybrid MMC's blocking ability for the DC side current, effectively realizes the coordination between the auxiliary isolating switch and the hybrid MMC, ensures that the capacitor voltages of the same sub-modules are basically consistent during the pre-charging period, suppresses the current impact on the AC and DC sides during the charging process, and quickly completes the charging of the two-terminal passive power supply system based on the hybrid MMC. It can shorten the charging time of the hybrid MMC passive power supply system, especially the hybrid MMC charging time of the DC side charging, effectively avoids the generation of "black modules" and bypass sub-modules during the charging process, and reduces the control difficulty of the hybrid MMC.

[0006] In one embodiment, the method further includes: after the second stage of active charging on the DC side is completed, locking the second hybrid MMC, and controlling the auxiliary isolation switch to short-circuit the auxiliary resistor while maintaining connectivity between the first hybrid MMC and the second hybrid MMC.

[0007] In one embodiment, the first stage of unlocking the second hybrid MMC and actively charging the second hybrid MMC on the DC side includes: first charging half of the sub-modules of the second hybrid MMC, and then charging the other half of the sub-modules; the second stage of actively charging the second hybrid MMC on the DC side includes: unlocking the second hybrid MMC, first charging half of the sub-modules of the second hybrid MMC, and then charging the other half of the sub-modules.

[0008] In one embodiment, the first voltage threshold and the second voltage threshold are calculated by the following formula:

[0009]

[0010] Where V H_unc1 is the first voltage threshold, V F_unc1 is the second voltage threshold, U line is the effective value of the AC line voltage of the active network to which the first MMC is connected; N H is the number of half-bridge submodules in each bridge arm of the first hybrid MMC, N F is the number of full-bridge sub-modules in each bridge arm of the first hybrid MMC.

[0011] In one embodiment, the third voltage threshold is 0.6 to 0.8 times the rated starting voltage.

[0012] In one embodiment, the third voltage threshold is 0.7 times the rated starting voltage.

[0013] In one embodiment, in the first hybrid MMC, the number of full-bridge sub-modules and half-bridge sub-modules is equal; in the second hybrid MMC, the number of full-bridge sub-modules and half-bridge sub-modules is equal.

[0014] In one embodiment, the hybrid MMC passive power supply system further includes an AC side pre-charging circuit connected between the first hybrid MMC and the AC equivalent power supply of the active network, the AC side pre-charging circuit including a starting resistor, an AC circuit breaker, and an AC side bypass switch; before the step of performing uncontrolled charging on the AC side of the hybrid MMC passive power supply system, the step also includes closing the AC circuit breaker and connecting the starting resistor to the hybrid MMC passive power supply system; the step of performing voltage balancing on the first hybrid MMC includes: bypassing each full-bridge sub-module in the first hybrid MMC, and when the voltage of each half-bridge sub-module in the first hybrid MMC rises to the same level as the voltage of each full-bridge sub-module in the first hybrid MMC, locking the first hybrid MMC; closing the AC side bypass switch; and unlocking the first hybrid MMC until the DC voltage reaches the rated starting voltage.

[0015] It is also necessary to provide a computer device comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the method described in any of the above embodiments when executing the computer program.

[0016] It is also necessary to provide a readable storage medium having a computer program stored thereon, which implements the steps of the method described in any of the above embodiments when the computer program is executed by a processor.

[0017] It is also necessary to provide a computer program product, comprising a computer program, which implements the steps of the method described in any of the above embodiments when the computer program is executed by a processor. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to better describe and illustrate the embodiments and / or examples of the inventions disclosed herein, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the accompanying drawings should not be considered to limit the scope of the disclosed inventions, the presently described embodiments and / or examples, and any of the best modes currently understood for these inventions.

[0019] Figure 1 This is a flow chart of a pre-charging method for a hybrid MMC passive power supply system in one embodiment of the present application;

[0020] Figure 2 is a block diagram of an exemplary hybrid MMC passive power supply system;

[0021] Figure 3 FIG. 4 is a topological diagram of an exemplary first hybrid MMC. DETAILED DESCRIPTION

[0022] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive disclosure of the present invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0024] It should be understood that when an element or layer is referred to as being "on," "adjacent to," "connected to," or "coupled to" another element or layer, it can be directly on, adjacent to, connected to, or coupled to the other element or layer, or there can be intervening elements or layers. Conversely, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are merely used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Thus, a first element, component, region, layer, or part discussed below may be represented as a second element, component, region, layer, or part without departing from the teachings of the present invention.

[0025] The purpose of the terms used herein is only to describe specific embodiments and is not intended to limit the present invention. When used herein, the singular forms "a", "an", and "the" are intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "comprising" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0026] In view of the shortcomings of the "one-by-one exit method", this application proposes a new pre-charging strategy for a hybrid MMC passive power supply system. Figure 1 This is a flow chart of a pre-charging method for a hybrid MMC passive power supply system in one embodiment of the present application. Figure 2FIG2 is a block diagram of an exemplary hybrid MMC passive power supply system. The hybrid MMC passive power supply system includes a first hybrid MMC on the AC side and a second hybrid MMC on the DC side. Figure 3 is an exemplary topological structure diagram of a first hybrid MMC. The hybrid MMC passive power supply system further includes an auxiliary resistor R connected between the first hybrid MMC and the second hybrid MMC, and an auxiliary isolation switch for controlling the connection of the auxiliary resistor. Figure 3 In the embodiment shown, the auxiliary isolating switch includes an auxiliary isolating switch S2 connected in series with the auxiliary resistor R and an auxiliary isolating switch S1 connected in parallel with the auxiliary resistor R. In one embodiment of the present application, the hybrid MMC passive power supply system also includes an AC side pre-charging circuit connected between the first hybrid MMC and the AC equivalent power supply Ug of the active network. The AC side pre-charging circuit includes a starting resistor R1, an AC circuit breaker B2 and an AC side bypass switch B1. The AC side bypass switch B1 is connected in parallel with the starting resistor R1, and the AC circuit breaker B2 is connected in series with the starting resistor R1. The first hybrid MMC and the second hybrid MMC both include multiple sub-modules, some of which are full-bridge sub-modules and the other part are half-bridge sub-modules. In one embodiment of the present application, the number of full-bridge sub-modules and half-bridge sub-modules in the first hybrid MMC is equal, and the number of full-bridge sub-modules and half-bridge sub-modules in the second hybrid MMC is also equal. Figure 1 In the embodiment shown, the pre-charging method of the hybrid MMC passive power supply system includes the following steps:

[0027] S110 , performing uncontrolled AC-side charging on the hybrid MMC passive power supply system.

[0028] Before performing uncontrolled AC-side charging of the hybrid MMC passive power supply system, the first and second hybrid MMCs are locked, and the auxiliary disconnector S2 on the DC side between the first and second hybrid MMCs is closed, connecting the two MMC systems via an auxiliary resistor R. Next, AC circuit breaker B2 in the AC-side pre-charging circuit of the first hybrid MMC is closed, causing the entire system to enter the uncontrolled AC-side charging phase. Uncontrolled AC-side charging is considered complete when the capacitor voltages of each half-bridge submodule in the first MMC reach a first voltage threshold and the capacitor voltages of each full-bridge submodule reach a second voltage threshold.

[0029] In one embodiment of the present application, the first voltage threshold and the second voltage threshold are calculated using the following formula:

[0030]

[0031] Where V H_unc1 is the first voltage threshold, V F_unc1 is the second voltage threshold, U lineN is the effective value of the AC line voltage of the active network to which the first MMC is connected; H is the number of half-bridge submodules in each bridge arm of the first hybrid MMC, N F is the number of full-bridge sub-modules in each bridge arm of the first hybrid MMC.

[0032] S120, performing active charging on the AC side.

[0033] After the AC side uncontrolled charging is completed, the electronic switches of each full-bridge submodule in the first MMC are turned on (ie, the first MMC is unlocked) to perform active charging on the AC side. Figure 3 When the Udc in the DAC reaches a third voltage threshold, active charging of the AC side is determined to be complete. In one embodiment of the present application, the third voltage threshold is approximately 0.7 times the rated startup voltage, for example, 0.6 to 0.8 times the rated startup voltage. The electronic switches in each full-bridge submodule and half-bridge submodule can be IGBTs (insulated gate bipolar transistors).

[0034] S130, performing the first stage of active DC side charging on the second hybrid MMC.

[0035] After the AC side active charging is completed, the second hybrid MMC is unlocked and the first stage of DC side active charging begins. In one embodiment of the present application, the first stage of DC side active charging includes two parts: the first part charges half of the submodules in the second hybrid MMC bridge arm, and the second part charges the other half of the submodules in the second hybrid MMC bridge arm.

[0036] S140 , performing voltage balancing on the first hybrid MMC.

[0037] When the first stage of active charging on the DC side is completed, the second hybrid MMC is locked and the voltage balancing stage of the first hybrid MMC is entered.

[0038] In one embodiment of the present application, the voltage balancing phase of the first hybrid MMC is divided into three parts. The first part involves bypassing the full-bridge submodule in each bridge arm. When the voltage of the half-bridge submodule rises to the same level as the full-bridge submodule, the first hybrid MMC is locked. The second part involves closing the AC-side bypass switch B1 of the first hybrid MMC. The third part involves unlocking the first hybrid MMC and actively controlling the DC voltage Udc to the rated startup voltage.

[0039] S150, performing the second stage of active DC side charging on the second hybrid MMC.

[0040] When the DC voltage Udc reaches the rated starting voltage (in actual application, this can be when the difference between the DC voltage Udc and the rated starting voltage is less than a preset error range), the voltage balancing phase of the first hybrid MMC is completed. At this time, the second hybrid MMC is unlocked, and the second hybrid MMC enters the second phase of active DC side charging. In one embodiment of the present application, the second phase of active DC side charging also includes two parts. The first part charges half of the submodules in the second hybrid MMC bridge arm, and the second part charges the other half of the submodules in the second hybrid MMC bridge arm. After the second phase of active DC side charging is completed, both the first hybrid MMC and the second hybrid MMC have completed pre-charging.

[0041] In one embodiment of the present application, step S150 further includes locking the second hybrid MMC (the first hybrid MMC may or may not be locked), opening the auxiliary isolating switch S2, and closing the auxiliary isolating switch S1 to complete pre-charging of the entire system.

[0042] The pre-charging method of the hybrid MMC passive power supply system is based on the auxiliary resistors R on the AC and DC sides of the hybrid MMC, fully utilizing the hybrid MMC's blocking capability for DC side current, effectively realizing the coordination between the auxiliary isolating switches S1 and S2 and the hybrid MMC, ensuring that the capacitor voltages of similar sub-modules remain basically consistent during the pre-charging period, suppressing the current impact on the AC and DC sides during the charging process, and quickly completing the charging of the two-terminal passive power supply system based on the hybrid MMC. This can shorten the charging time of the hybrid MMC passive power supply system, especially the hybrid MMC charging time for DC side charging, effectively avoiding the generation of "black modules" and bypass sub-modules during the charging process, and reducing the control difficulty of the hybrid MMC.

[0043] It should be understood that, although the various steps in the flowchart of the present application are shown in sequence as indicated by the arrows, these steps are not necessarily executed 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 flowchart of the present application may 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. 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.

[0044] The present application also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the following steps:

[0045] In a state where the first hybrid MMC and the second hybrid MMC are locked and the auxiliary isolating switch connects the auxiliary resistor between the first hybrid MMC and the second hybrid MMC, performing uncontrolled AC-side charging on the hybrid MMC passive power supply system until the capacitor voltage of each half-bridge sub-module in the first MMC reaches a first voltage threshold and the capacitor voltage of each full-bridge sub-module reaches a second voltage threshold;

[0046] After the AC side uncontrolled charging is completed, turning on the electronic switches of each of the full-bridge sub-modules in the first MMC to perform active AC side charging until the DC voltage reaches a third voltage threshold;

[0047] After the AC side active charging is completed, unlocking the second hybrid MMC and performing the first stage of DC side active charging on the second hybrid MMC;

[0048] After the first stage of active charging on the DC side is completed, the second hybrid MMC is locked and the voltage of the first hybrid MMC is balanced until the DC voltage reaches the rated starting voltage;

[0049] The second hybrid MMC is unlocked, and the second hybrid MMC is subjected to the second stage of active DC side charging.

[0050] In one embodiment of the present application, when the computer program is executed by a processor, the following steps are further implemented:

[0051] After the second stage of active charging on the DC side is completed, the second hybrid MMC is locked, and the auxiliary isolation switch is controlled to short-circuit the auxiliary resistor while maintaining connectivity between the first hybrid MMC and the second hybrid MMC.

[0052] In one embodiment of the present application, the first stage of active charging on the DC side includes: first charging half of the sub-modules of the second hybrid MMC, and then charging the other half of the sub-modules.

[0053] In one embodiment of the present application, the second stage of active charging on the DC side includes: first charging half of the sub-modules of the second hybrid MMC, and then charging the other half of the sub-modules.

[0054] In one embodiment of the present application, the first voltage threshold and the second voltage threshold are calculated using the following formula:

[0055]

[0056] Where V H_unc1 is the first voltage threshold, V F_unc1 is the second voltage threshold, U lineis the effective value of the AC line voltage of the active network to which the first MMC is connected; N H is the number of half-bridge submodules in each bridge arm of the first hybrid MMC, N F is the number of full-bridge sub-modules in each bridge arm of the first hybrid MMC.

[0057] In one embodiment of the present application, the third voltage threshold is 0.6 to 0.8 times the rated starting voltage.

[0058] In one embodiment of the present application, in the first hybrid MMC, the number of full-bridge sub-modules and half-bridge sub-modules is equal; in the second hybrid MMC, the number of full-bridge sub-modules and half-bridge sub-modules is equal.

[0059] In one embodiment of the present application, the step of performing voltage balancing on the first hybrid MMC includes:

[0060] Bypassing each full-bridge sub-module in the first hybrid MMC, and locking the first hybrid MMC when the voltage of each half-bridge sub-module in the first hybrid MMC rises to a voltage close to that of each full-bridge sub-module in the first hybrid MMC;

[0061] Closing the AC side bypass switch;

[0062] The first hybrid MMC is unlocked until the DC voltage reaches a rated starting voltage.

[0063] The present application also provides a computer device, comprising a memory and a processor, wherein a computer program is stored in the memory, and when the processor executes the computer program, the following steps are implemented:

[0064] In a state where the first hybrid MMC and the second hybrid MMC are locked and the auxiliary isolating switch connects the auxiliary resistor between the first hybrid MMC and the second hybrid MMC, performing uncontrolled AC-side charging on the hybrid MMC passive power supply system until the capacitor voltage of each half-bridge sub-module in the first MMC reaches a first voltage threshold and the capacitor voltage of each full-bridge sub-module reaches a second voltage threshold;

[0065] After the AC side uncontrolled charging is completed, turning on the electronic switches of each of the full-bridge sub-modules in the first MMC to perform active AC side charging until the DC voltage reaches a third voltage threshold;

[0066] After the AC side active charging is completed, unlocking the second hybrid MMC and performing the first stage of DC side active charging on the second hybrid MMC;

[0067] After the first stage of active charging on the DC side is completed, the second hybrid MMC is locked and the voltage of the first hybrid MMC is balanced until the DC voltage reaches the rated starting voltage;

[0068] The second hybrid MMC is unlocked, and the second hybrid MMC is subjected to the second stage of active DC side charging.

[0069] In one embodiment of the present application, when the processor executes the computer program, the processor further implements the following steps:

[0070] After the second stage of active charging on the DC side is completed, the second hybrid MMC is locked, and the auxiliary isolation switch is controlled to short-circuit the auxiliary resistor while maintaining connectivity between the first hybrid MMC and the second hybrid MMC.

[0071] In one embodiment of the present application, the first stage of active charging on the DC side includes: first charging half of the sub-modules of the second hybrid MMC, and then charging the other half of the sub-modules.

[0072] In one embodiment of the present application, the second stage of active charging on the DC side includes: first charging half of the sub-modules of the second hybrid MMC, and then charging the other half of the sub-modules.

[0073] In one embodiment of the present application, the first voltage threshold and the second voltage threshold are calculated using the following formula:

[0074]

[0075] Where V H_unc1 is the first voltage threshold, V F_unc1 is the second voltage threshold, U line is the effective value of the AC line voltage of the active network to which the first MMC is connected; N H is the number of half-bridge submodules in each bridge arm of the first hybrid MMC, N F is the number of full-bridge sub-modules in each bridge arm of the first hybrid MMC.

[0076] In one embodiment of the present application, the third voltage threshold is 0.6 to 0.8 times the rated starting voltage.

[0077] In one embodiment of the present application, in the first hybrid MMC, the number of full-bridge sub-modules and half-bridge sub-modules is equal; in the second hybrid MMC, the number of full-bridge sub-modules and half-bridge sub-modules is equal.

[0078] In one embodiment of the present application, the step of performing voltage balancing on the first hybrid MMC includes:

[0079] Bypassing each full-bridge sub-module in the first hybrid MMC, and locking the first hybrid MMC when the voltage of each half-bridge sub-module in the first hybrid MMC rises to a voltage close to that of each full-bridge sub-module in the first hybrid MMC;

[0080] Closing the AC side bypass switch;

[0081] The first hybrid MMC is unlocked until the DC voltage reaches a rated starting voltage.

[0082] The present application also provides a computer program product, comprising a computer program, which, when executed by a processor, implements the following steps:

[0083] In a state where the first hybrid MMC and the second hybrid MMC are locked and the auxiliary isolating switch connects the auxiliary resistor between the first hybrid MMC and the second hybrid MMC, performing uncontrolled AC-side charging on the hybrid MMC passive power supply system until the capacitor voltage of each half-bridge sub-module in the first MMC reaches a first voltage threshold and the capacitor voltage of each full-bridge sub-module reaches a second voltage threshold;

[0084] After the AC side uncontrolled charging is completed, turning on the electronic switches of each of the full-bridge sub-modules in the first MMC to perform active AC side charging until the DC voltage reaches a third voltage threshold;

[0085] After the AC side active charging is completed, unlocking the second hybrid MMC and performing the first stage of DC side active charging on the second hybrid MMC;

[0086] After the first stage of active charging on the DC side is completed, the second hybrid MMC is locked and the voltage of the first hybrid MMC is balanced until the DC voltage reaches the rated starting voltage;

[0087] The second hybrid MMC is unlocked, and the second hybrid MMC is subjected to the second stage of active DC side charging.

[0088] In one embodiment of the present application, when the computer program is executed by a processor, the following steps are further implemented:

[0089] After the second stage of active charging on the DC side is completed, the second hybrid MMC is locked, and the auxiliary isolation switch is controlled to short-circuit the auxiliary resistor while maintaining connectivity between the first hybrid MMC and the second hybrid MMC.

[0090] In one embodiment of the present application, the first stage of active charging on the DC side includes: first charging half of the sub-modules of the second hybrid MMC, and then charging the other half of the sub-modules.

[0091] In one embodiment of the present application, the second stage of active charging on the DC side includes: first charging half of the sub-modules of the second hybrid MMC, and then charging the other half of the sub-modules.

[0092] In one embodiment of the present application, the first voltage threshold and the second voltage threshold are calculated using the following formula:

[0093]

[0094] Where V H_unc1 is the first voltage threshold, V F_unc1 is the second voltage threshold, U line is the effective value of the AC line voltage of the active network to which the first MMC is connected; N H is the number of half-bridge submodules in each bridge arm of the first hybrid MMC, N F is the number of full-bridge sub-modules in each bridge arm of the first hybrid MMC.

[0095] In one embodiment of the present application, the third voltage threshold is 0.6 to 0.8 times the rated starting voltage.

[0096] In one embodiment of the present application, in the first hybrid MMC, the number of full-bridge sub-modules and half-bridge sub-modules is equal; in the second hybrid MMC, the number of full-bridge sub-modules and half-bridge sub-modules is equal.

[0097] In one embodiment of the present application, the step of performing voltage balancing on the first hybrid MMC includes:

[0098] Bypassing each full-bridge sub-module in the first hybrid MMC, and locking the first hybrid MMC when the voltage of each half-bridge sub-module in the first hybrid MMC rises to a voltage close to that of each full-bridge sub-module in the first hybrid MMC;

[0099] Closing the AC side bypass switch;

[0100] The first hybrid MMC is unlocked until the DC voltage reaches a rated starting voltage.

[0101] 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, storage, 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 or optical memory, etc. Volatile memory may include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0102] Throughout this specification, references to terms such as "some embodiments," "other embodiments," and "desired embodiments" indicate that a particular feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. Although these terms are used interchangeably throughout this specification, they do not necessarily refer to the same embodiment or example.

[0103] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A precharging method for a hybrid MMC passive power supply system, the hybrid MMC passive power supply system comprising a first hybrid MMC on the AC side and a second hybrid MMC on the DC side, an auxiliary resistor connected between the first hybrid MMC and the second hybrid MMC, and an auxiliary isolating switch for controlling the connection of the auxiliary resistor; The first hybrid MMC and the second hybrid MMC each include a plurality of submodules, some of which are full-bridge submodules and some of which are half-bridge submodules; characterized in that: The method comprises: In a state where the first hybrid MMC and the second hybrid MMC are locked and the auxiliary isolating switch connects the auxiliary resistor between the first hybrid MMC and the second hybrid MMC, performing uncontrolled AC-side charging on the hybrid MMC passive power supply system until the capacitor voltage of each half-bridge sub-module in the first hybrid MMC reaches a first voltage threshold and the capacitor voltage of each full-bridge sub-module reaches a second voltage threshold; After the AC side uncontrolled charging is completed, turning on the electronic switches of each of the full-bridge sub-modules in the first hybrid MMC to perform active AC side charging until the DC voltage reaches a third voltage threshold; After the AC side active charging is completed, the second hybrid MMC is unlocked, and the first stage of DC side active charging of the second hybrid MMC is performed, including: first charging half of the submodules of the second hybrid MMC, and then charging the other half of the submodules; After the first stage of active charging on the DC side is completed, the second hybrid MMC is locked and the voltage of the first hybrid MMC is balanced until the DC voltage reaches the rated starting voltage; The second stage of actively charging the second hybrid MMC on the DC side includes: unlocking the second hybrid MMC, first charging half of the submodules of the second hybrid MMC, and then charging the other half of the submodules.

2. The pre-charging method of the hybrid MMC passive power supply system according to claim 1, wherein Also includes: After the second stage of active charging on the DC side is completed, the second hybrid MMC is locked, and the auxiliary isolation switch is controlled to short-circuit the auxiliary resistor while maintaining connectivity between the first hybrid MMC and the second hybrid MMC.

3. The pre-charging method of the hybrid MMC passive power supply system according to claim 1, wherein The first voltage threshold and the second voltage threshold are calculated by the following formula: Where V H_unc1 is the first voltage threshold, V F_unc1 is the second voltage threshold, U line is the effective value of the AC line voltage of the active network to which the first hybrid MMC is connected; N H is the number of half-bridge submodules in each bridge arm of the first hybrid MMC, N F is the number of full-bridge sub-modules in each bridge arm of the first hybrid MMC.

4. The pre-charging method of the hybrid MMC passive power supply system according to claim 1, wherein The third voltage threshold is 0.6 to 0.8 times the rated starting voltage.

5. The pre-charging method of the hybrid MMC passive power supply system according to claim 1, wherein In the first hybrid MMC, the number of full-bridge sub-modules and half-bridge sub-modules is equal; in the second hybrid MMC, the number of full-bridge sub-modules and half-bridge sub-modules is equal.

6. The pre-charging method of the hybrid MMC passive power supply system according to any one of claims 1-5, characterized in that, The hybrid MMC passive power supply system further includes an AC side pre-charging circuit connected between the first hybrid MMC and the AC equivalent power supply of the active network, wherein the AC side pre-charging circuit includes a starting resistor, an AC circuit breaker, and an AC side bypass switch; Before the step of performing uncontrolled charging on the AC side of the hybrid MMC passive power supply system, the method further includes closing the AC circuit breaker and connecting the starting resistor to the hybrid MMC passive power supply system; The step of performing voltage balancing on the first hybrid MMC comprises: Bypassing each full-bridge sub-module in the first hybrid MMC, and locking the first hybrid MMC when the voltage of each half-bridge sub-module in the first hybrid MMC rises to a voltage close to that of each full-bridge sub-module in the first hybrid MMC; Closing the AC side bypass switch; The first hybrid MMC is unlocked until the DC voltage reaches a rated starting voltage.

7. 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.

8. A 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.

9. 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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