Modular multilevel converter control method and device

Abstract

The embodiment of the application provides a control method and device of a modular multilevel converter, and relates to the technical field of the modular multilevel converter. The target bridge arm of the converter valve has power modules with multiple rated working voltages. The method comprises the following steps: according to the different rated working voltages, all the power modules of the target bridge arm are divided into M groups; the bridge arm current of the target bridge arm is acquired, and the current direction of the bridge arm current is determined; according to the positive and negative of the first reference voltage of the target bridge arm, the target module is determined in each first module of the M groups respectively, and the statistical quantity of the capacitor voltage of each target module of the M groups is acquired; according to the first reference voltage, the current direction, the number of modules of each target module of the M groups, the statistical quantity and the rated working voltage, the number of power modules needed to be put into by the M groups respectively is determined. Thus, the power modules with different voltage levels in the bridge arm of the converter valve can be stably operated at the respective rated working voltages.

Description

Technical Field

[0001] This application relates to the field of modular multilevel converter technology, and more particularly to control methods and apparatus for modular multilevel converters. Background Technology

[0002] Modular multilevel converter systems are widely used in flexible DC transmission projects, ultra-high voltage hybrid DC, flexible low-frequency transmission, reactive power compensation, AC / DC energy storage, and other DC power electronic system fields. The converter valve control and protection system is the link between the converter control and protection system and the converter valve equipment. It receives commands from the converter control and protection system, modulates them to obtain control commands for each power module in each arm, and simultaneously receives status information from each power module, participating in the control of the entire converter valve.

[0003] With technological advancements, there is a growing demand for cascaded power modules of varying power levels and types. Depending on the devices or voltage levels used, the characteristic differences resulting from varying rated operating voltages must be considered. Currently, in applications such as flexible DC transmission projects employing modular multilevel converter topologies, the nearest-level approximation method is typically used for modulation. The converter valve control and protection system calculates the number of power modules required for each bridge arm based on the reference voltage issued by the converter control and protection system and the module's rated operating voltage.

[0004] The relevant technology divides all sub-modules of each bridge arm of the converter valve into multiple groups and dynamically adjusts the number of power modules put into each group to achieve voltage equalization control of the entire bridge arm. However, since there are multiple rated operating voltage power modules cascaded in a bridge arm, the relevant technology cannot ensure that power modules of different voltage levels in the bridge arm of the converter valve operate stably at their respective rated operating voltages. Summary of the Invention

[0005] This application provides a control method and apparatus for a modular multilevel converter, so that power modules of different voltage levels in the bridge arm of the converter valve can operate stably at their respective rated operating voltages.

[0006] In a first aspect, embodiments of this application provide a control method for a modular multilevel converter, wherein the target arm of the converter valve has power modules with multiple rated operating voltages, and the method includes:

[0007] Based on their rated operating voltages, all power modules of the target bridge arm are divided into M groups, with different rated operating voltages for each group.

[0008] Obtain the bridge arm current of the target bridge arm and determine the current direction of the bridge arm current;

[0009] Based on the sign of the first reference voltage of the target bridge arm, the target module is determined in each of the first modules of each of the M groups, and the statistical values ​​of the capacitor voltage of each target module in each of the M groups are obtained; wherein, the first module is the power module that has not experienced a fault.

[0010] Based on the first reference voltage, the aforementioned current direction, the number of target modules in each of the M groups, the aforementioned statistics, and the rated operating voltage, the number of power modules that need to be put into each of the M groups is determined; wherein, the sum of the first values ​​corresponding to each of the M groups is equal to the first reference voltage, and the first value corresponding to any group in the M groups is the product of the number of power modules that need to be put into that group and the rated operating voltage.

[0011] In one embodiment, the control method further includes:

[0012] The first reference voltage is compared with zero to obtain the comparison result;

[0013] Obtain the bridge arm current of the target bridge arm, including:

[0014] In response to the above comparison result that the first reference voltage is not equal to zero, the bridge arm current of the target bridge arm is obtained.

[0015] In one implementation, the target module is determined in each of the first modules of the M groups based on the sign of the first reference voltage of the target bridge arm, including:

[0016] In response to a positive first reference voltage, each of the first modules in each of the M groups is identified as the target module.

[0017] In one implementation, at least a portion of the first module of the target bridge arm has a topology type of full bridge;

[0018] Based on the sign of the first reference voltage of the target bridge arm, the target module is determined in each of the first modules of group M, including:

[0019] In response to the first reference voltage being negative, each of the first modules in the M groups, whose respective topology type is full bridge, is determined as the target module.

[0020] In one implementation, the number of power modules required for each of the M groups is determined based on the first reference voltage, the current direction, the number of modules in each target module of the M groups, the statistics, and the rated operating voltage, including:

[0021] In the M groups, identify M-1 first groups and one second group;

[0022] Based on the first reference voltage, the current direction, the number of each target module in each of the M groups, the statistics, and the rated operating voltage of each of the M-1 first groups, determine the number of power modules that need to be put into each of the M-1 first groups.

[0023] Based on the first reference voltage, the number of power modules required for each of the M-1 first groups and their rated operating voltages, as well as the rated operating voltage of the second group, the number of power modules required for the second group is determined.

[0024] In one implementation, the first reference voltage is positive;

[0025] Based on the first reference voltage, the aforementioned current direction, the number of target modules in each of the M groups, the aforementioned statistics, and the rated operating voltages of the M-1 first groups, determine the number of power modules required for each of the M-1 first groups, including:

[0026] Based on the first reference voltage, the aforementioned current direction, the number of each target module in each of the M groups, the aforementioned statistics, and the rated operating voltage of each of the M-1 first groups, determine the number of initial modules that need to be deployed in each of the M-1 first groups; wherein, the product of the number of initial modules that need to be deployed in any first group and the rated operating voltage is in a first proportional relationship with the aforementioned statistics of each target module in that first group, the first proportional relationship is a direct proportional relationship when the aforementioned current direction is the discharge direction, and an inverse proportional relationship when the aforementioned current direction is the charging direction;

[0027] Based on the initial number of modules required for each of the M-1 first groups, determine the number of power modules required for each of the M-1 first groups.

[0028] In one implementation, the first reference voltage is negative;

[0029] Based on the first reference voltage, the aforementioned current direction, the number of target modules in each of the M groups, the aforementioned statistics, and the rated operating voltages of the M-1 first groups, determine the number of power modules required for each of the M-1 first groups, including:

[0030] Based on the first reference voltage, the aforementioned current direction, the number of each target module in each of the M groups, the aforementioned statistics, and the rated operating voltage of each of the M-1 first groups, determine the number of initial modules that need to be put into each of the M-1 first groups; wherein, the product of the number of initial modules that need to be put into any first group and the rated operating voltage is in a second proportional relationship with the aforementioned statistics of each target module in that first group, the second proportional relationship is inversely proportional when the aforementioned current direction is the discharge direction, and directly proportional when the aforementioned current direction is the charging direction;

[0031] Based on the initial number of modules required for each of the M-1 first groups, determine the number of power modules required for each of the M-1 first groups.

[0032] In one implementation, the M-1 first groups include at least one target group, and the number of initial modules required for any target group is greater than the number of modules in each target module of that target group.

[0033] Based on the initial number of modules required for each of the M-1 first groups, determine the number of power modules required for each of the M-1 first groups, including:

[0034] The number of power modules required for each target group in at least one of the above target groups is determined to be equal to the number of modules in each target module of that target group.

[0035] In one embodiment, after determining that the number of power modules required for each target group in the at least one target group is equal to the number of modules in each target module of that target group, the method further includes:

[0036] Determine the second reference voltage for each group in group M other than at least one of the target groups mentioned above. The second reference voltage is the difference between the first reference voltage and the second value. The second value is the sum of the third values ​​corresponding to each of the at least one target group. The third value corresponding to any target group is the product of the number of target modules in that target group and the rated operating voltage.

[0037] In one implementation, the above statistics include any one of the following: mean capacitor voltage, sum of capacitor voltage, minimum capacitor voltage, maximum capacitor voltage, sum of squares of capacitor voltage, target power, and target energy;

[0038] Both the target power and the target energy are determined based on the capacitor voltage, the arm current, or the arm resistance of the target arm.

[0039] In one embodiment, the control method further includes:

[0040] In response to the above comparison result that the first reference voltage is equal to zero, it is determined that the number of power modules that need to be put into each of the M groups is zero.

[0041] Secondly, embodiments of this application provide a control device for a modular multilevel converter, wherein the target arm of the converter valve has power modules with multiple rated operating voltages. The device includes:

[0042] The grouping unit is configured to divide all power modules of the target arm into M groups based on their rated operating voltages, where the rated operating voltages of the different groups are different;

[0043] The acquisition unit is configured to acquire the arm current of the target arm and determine the current direction of the arm current;

[0044] The first determining unit is configured to determine the target module in each of the first modules of each of the M groups based on the sign of the first reference voltage of the target bridge arm, and to obtain the statistics of the capacitor voltage of each of the target modules in each of the M groups; wherein, the first module is the power module that has not experienced a fault.

[0045] The second determining unit is configured to determine the number of power modules that need to be put into each of the M groups based on the first reference voltage, the current direction, the number of modules of each target module in each of the M groups, the statistics and the rated operating voltage; wherein, the sum of the first values ​​corresponding to each of the M groups is equal to the first reference voltage, and the first value corresponding to any group in the M groups is the product of the number of power modules and the rated operating voltage of any group.

[0046] Thirdly, embodiments of this application provide a computer device including a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, it implements a control method for a modular multilevel converter as described in any implementation of the first aspect.

[0047] Fourthly, embodiments of this application provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements a control method for a modular multilevel converter as described in any implementation of the first aspect.

[0048] Fifthly, embodiments of this application provide a computer program product, including a computer program / instruction, which, when executed by a processor, implements a control method for a modular multilevel converter as described in any implementation of the first aspect.

[0049] The solution provided in this application can divide all power modules of a target bridge arm into M groups based on their rated operating voltages, with different rated operating voltages in different groups. Furthermore, the solution acquires the bridge arm current of the target bridge arm and determines its current direction. Based on the sign of the first reference voltage of the target bridge arm, it identifies target modules within each of the first modules in each of the M groups and acquires statistical values ​​of the capacitor voltage of each target module in each of the M groups; wherein the first module is a power module that has not experienced a fault. Then, based on the first reference voltage of the target bridge arm, the aforementioned current direction, the number of target modules in each of the M groups, the aforementioned statistical values, and the rated operating voltage, the solution determines the number of power modules required to be deployed in each of the M groups. The sum of the first values ​​corresponding to each of the M groups equals the first reference voltage, and the first value corresponding to any group in the M groups is the product of the number of power modules required to be deployed in that group and the rated operating voltage. Therefore, compared with related technologies, this solution can take into account the situation where multiple rated operating voltage power modules are cascaded in a bridge arm, realize voltage balance within the group and capacitor voltage balance between groups, ensure that power modules of different voltage levels can operate stably under their respective rated operating voltages, and achieve long-term stable and reliable operation of the converter valve. Attached Figure Description

[0050] The technical solution and other beneficial effects of this application will become apparent from the following detailed description of specific embodiments in conjunction with the accompanying drawings.

[0051] Figure 1 This is a schematic diagram of one bridge arm of the converter valve in an embodiment of this application;

[0052] Figure 2 This is a flowchart of a control method for a modular multilevel converter in an embodiment of this application;

[0053] Figure 3 This is a schematic diagram of the grouping of the target bridge arms in the embodiments of this application;

[0054] Figure 4 This is a flowchart of the process for determining the number of power modules in the embodiments of this application;

[0055] Figure 5 This is a schematic diagram of a control method for a modular multilevel converter in an embodiment of this application;

[0056] Figure 6 This is a schematic diagram of the control device for the modular multilevel converter in the embodiments of this application.

[0057] Reference numerals: 601-Grouping unit, 602-Acquisition unit, 603-First determination unit, 604-Second determination unit. Detailed Implementation

[0058] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0059] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the term "and / or" in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Furthermore, the character " / " in this document, unless otherwise specified, generally indicates that the preceding and following related objects have an "or" relationship.

[0060] Figure 1 This is a schematic diagram of one arm of the converter valve in an embodiment of this application. Figure 1 As shown, power modules 1, 2, 3, ..., N are connected in series to form one arm of the converter valve. Each power module can be a half-bridge, full-bridge, or near-full-bridge topology. The specific configuration of a half-bridge power module is as follows... Figure 1 The enlarged schematic diagram of power module N shows that it specifically includes a DC capacitor and multiple fully controlled devices (such as...) connected in parallel with the DC capacitor. Figure 1 The circuit shown is composed of IGCT1 and IGCT2 connected in series, where each fully controlled device is connected in parallel with a reverse diode. Figure 1 The IGBTs (Insulated Gate Bipolar Transistors) and IGCTs (Integrated Gate-Commutated Thyristors) shown are both fully controllable devices. The N power modules have different voltage levels, such as 4500VIGBTs, 6500VIGBTs, and 6500VIGCTs.

[0061] Below, the bridge arm of the power module with multiple rated operating voltages will be referred to as the target bridge arm, and the control method of the modular multilevel converter will be introduced.

[0062] Figure 2 This is a flowchart of a control method for a modular multilevel converter in an embodiment of this application. The target arm of the converter valve in this converter has power modules with various rated operating voltages. The control method can be executed, for example, by a converter valve control protection system. The control method includes the following steps:

[0063] S201: Based on the different rated operating voltages, all power modules of the target bridge arm are divided into M groups, where the rated operating voltages of different groups are different;

[0064] S203: Obtain the bridge arm current of the target bridge arm and determine the current direction of the bridge arm current;

[0065] S205: Based on the sign of the first reference voltage of the target bridge arm, determine the target module in each of the first modules of each of the M groups, and obtain the statistical values ​​of the capacitor voltage of each target module in each of the M groups; wherein, the first module is the power module that has not experienced a fault.

[0066] S207: Based on the first reference voltage, the current direction, the number of each target module in each of the M groups, the statistics, and the rated operating voltage, determine the number of power modules that need to be put into each of the M groups; wherein, the sum of the first values ​​corresponding to each of the M groups is equal to the first reference voltage, and the first value corresponding to any group in the M groups is the product of the number of power modules that need to be put into any group and the rated operating voltage.

[0067] Figure 2 The corresponding embodiment provides a solution that divides all power modules of the target bridge arm into M groups based on their rated operating voltages, with different rated operating voltages in different groups. Furthermore, the solution acquires the bridge arm current of the target bridge arm and determines its current direction. Based on the sign of the first reference voltage of the target bridge arm, it identifies the target module within each of the first modules in each of the M groups and acquires statistical values ​​of the capacitor voltage of each target module in each of the M groups; wherein the first module is a power module that has not experienced a fault. Then, based on the first reference voltage of the target bridge arm, the aforementioned current direction, the number of target modules in each of the M groups, the aforementioned statistical values, and the rated operating voltage, the solution determines the number of power modules required to be deployed in each of the M groups. The sum of the first values ​​corresponding to each of the M groups equals the first reference voltage, and the first value corresponding to any group in the M groups is the product of the number of power modules required to be deployed in that group and the rated operating voltage. Therefore, compared with related technologies, this solution can take into account the situation where multiple rated operating voltage power modules are cascaded in a bridge arm, realize voltage balance within the group and capacitor voltage balance between groups, ensure that power modules of different voltage levels can operate stably under their respective rated operating voltages, and achieve long-term stable and reliable operation of the converter valve.

[0068] Steps S201 to S207 will be explained below.

[0069] In step S201, all power modules of the target bridge arm are divided into M groups based on their rated operating voltages, where M is a natural number greater than 1. The rated operating voltages of different groups are different, while the rated operating voltages of all power modules within the same group are the same. Furthermore, the number of power modules in any two groups within the M groups may be equal or unequal.

[0070] It should be noted that all power modules in the target bridge arm include the first module and the second module. The first module is the power module that has not experienced a fault and can be referred to as the normal power module. The second module is the power module that has experienced a fault and can be referred to as the faulty power module. The topology type of any power module in the target bridge arm can be any of the following: half-bridge, full-bridge, and quasi-full-bridge.

[0071] Taking a target bridge arm comprising power modules 1, 2, ..., i, (i+1), ..., j, (j+1), ..., N, where power modules 1 and 2 have the same rated operating voltage, power modules i and (i+1) have the same rated operating voltage, and power modules j, (j+1), ..., N have the same rated operating voltage, the grouping of all power modules in the target bridge arm can be as follows: Figure 3 As shown. Among them, Figure 3 This is a schematic diagram of the grouping of the target bridge arms in an embodiment of this application. For example... Figure 3 As shown, based on their rated operating voltages, all power modules of the target bridge arm are divided into M groups, where M is a natural number greater than 1. For example, power modules 1 and 2 are assigned to group 1, power modules i and (i+1) are assigned to group 2, and so on, and power modules j, (j+1), ..., N are assigned to group M. The rated operating voltage of the power modules in each group is... i = 1 to M. It should be understood that i = 1 to M means that i is a natural number in the range [1, M].

[0072] In step S203, the bridge arm current I of the target bridge arm is obtained. arm And determine the bridge arm current I arm The direction of the current. The target bridge arm current I can be acquired using a designated bridge arm current acquisition device. arm Bridge arm current I arm The direction of the current can be determined, for example, based on the bridge arm current I. arm The sign is determined. For example, when the bridge arm current I... arm When positive, the bridge arm current I arm The direction of the current is the charging direction; when the bridge arm current I arm When it is negative, the bridge arm current I arm The direction of the current is the direction of discharge.

[0073] In step S205, according to the first reference voltage U arm The sign of the target module is determined in each of the first modules of each of the M groups, and the statistical value of the capacitor voltage of each target module in each of the M groups is obtained.

[0074] Specifically, at the first reference voltage U arm When the voltage is positive, the first module of each of the M groups can be activated, and each first module of the M groups can be identified as the target module. At the first reference voltage U... arm When the value is negative, the first module of each of the M groups with a full-bridge topology can be put into operation, and each first module of each of the M groups with a full-bridge topology can be identified as the target module. In one example, the first module with a full-bridge topology can be called the normal full-bridge power module.

[0075] For any group in M, the statistics of the capacitor voltage of each target module in that group can include any of the following: mean capacitor voltage, sum of capacitor voltages, minimum capacitor voltage, maximum capacitor voltage, sum of squares of capacitor voltages, target power, target energy, etc. Target power and target energy can both be determined based on capacitor voltage, bridge arm current, or bridge arm resistance of the target bridge arm, etc.

[0076] In step S207, based on the first reference voltage U of the target bridge arm arm Bridge arm current I arm Based on the current direction, the number of target modules in each of the M groups, the aforementioned statistics, and the rated operating voltage, the number of power modules required for each of the M groups is determined; wherein, the sum of the first values ​​corresponding to each of the M groups is equal to the first reference voltage U. arm The first value corresponding to any group in group M is the product of the number of power modules required for that group and the rated operating voltage. This represents the number of power modules that need to be deployed in the i-th group. Taking the rated operating voltage of group i as an example, U arm and The following relationship must be satisfied:

[0077]

[0078] Specifically, this can be achieved by executing, such as Figure 4 The process for determining the number of power modules shown determines the number of power modules needed for each of the M groups. Among these, Figure 4 This is a flowchart illustrating the process of determining the number of power modules in an embodiment of this application. For example... Figure 4 As shown, the process of determining the number of power modules includes the following steps:

[0079] S2071: Identify M-1 first groups and one second group from the M groups;

[0080] S2073: Based on the first reference voltage, the current direction of the bridge arm current, the number of each target module in each of the M groups, the statistical value of the capacitor voltage, and the rated operating voltage of each of the M-1 first groups, determine the number of power modules that need to be put into each of the M-1 first groups.

[0081] S2075: Based on the first reference voltage, the number of power modules that need to be put into the first group M-1 and their rated operating voltages, and the rated operating voltage of the second group, determine the number of power modules that need to be put into the second group.

[0082] It should be noted that by determining the number of power modules required for each of the M-1 first groups based on the first reference voltage, the current direction of the bridge arm current, the number of target modules in each of the M groups, the statistical values ​​of capacitor voltage, and the rated operating voltage of each of the M-1 first groups, and then determining the number of power modules for the second group based on the first reference voltage, the number of power modules required for each of the M-1 first groups, their rated operating voltage, and the rated operating voltage of the second group, the effectiveness of determining the number of power modules required for each of the M groups can be further improved. This achieves voltage balance within the groups and capacitor voltage balance between the groups, ensuring that power modules of different voltage levels can operate stably under their respective rated operating voltages, and achieving long-term stable and reliable operation of the converter valve.

[0083] Steps S2071 to S2075 will be explained below.

[0084] In step S2071, M-1 first groups and one second group are determined from the M groups. In one example, M-1 groups can be randomly selected from the M groups as the first group, and the remaining group can be designated as the second group. In another example, groups 1 through M-1 of the M groups can be designated as the first group, and the last group (i.e., the M group) can be designated as the second group. It should be understood that the embodiments of this application do not specifically limit the method for determining the first and second groups.

[0085] In step S2073, according to the first reference voltage U arm Bridge arm current I arm The current direction, the number of target modules in each of the M groups, the statistical values ​​of capacitor voltage, and the rated operating voltage of each of the M-1 first groups are used to determine the number of power modules that need to be put into each of the M-1 first groups.

[0086] Specifically, it can be based on the first reference voltage U. arm Bridge arm current I armBased on the current direction, the number of target modules in each of the M groups, the statistical values ​​of capacitor voltage, and the rated operating voltage of each of the M-1 first groups, the initial number of modules to be put into each of the M-1 first groups is determined. Then, based on the initial number of modules to be put into each of the M-1 first groups, the number of power modules to be put into each of the M-1 first groups is determined. Wherein, at the first reference voltage U... arm When the value is positive, the product of the initial number of modules and the rated operating voltage of any given first group is proportional to the aforementioned statistic of that first group. This first proportionality is related to the bridge arm current I. arm The relationship is directly proportional when the current direction is the discharge direction, and when the bridge arm current I... arm When the current direction is the same as the charging direction, the relationship is inversely proportional. At the first reference voltage U... arm When the value is negative, the product of the initial number of modules and the rated operating voltage of any given first group is proportional to the aforementioned statistics of that first group in a second proportional relationship. This second proportional relationship is expressed in the bridge arm current I. arm When the current direction is the same as the discharge direction, the relationship is inversely proportional. This applies to the bridge arm current I. arm The relationship is directly proportional when the direction of the current is the same as the direction of charging.

[0087] Next, let's take the first reference voltage U as an example. arm Taking a positive value and the first module as the normal power module as an example, the method for determining the initial number of modules to be put into each of the M-1 first groups will be illustrated. According to the description above, at the first reference voltage U... arm When positive, each normal power module in each of the M groups is a target module, and the number of modules in each of the M groups' normal power modules is... The calculation involves determining the number of initial modules required for each of the M-1 first groups.

[0088] Figure 5 This is a schematic diagram of a control method for a modular multilevel converter in an embodiment of this application.

[0089] in, Figure 5 First reference voltage U arm A positive value indicates the number of normal power modules in each of the M groups.

[0090] First reference voltage U arm When it is positive, it can be like this Figure 5 As shown, for the bridge arm current I arm Perform direction determination and obtain the determination result (e.g.) Figure 5 The selector switch shown is used to determine the bridge arm current I. arm When the direction of the current is the direction of discharge, such as Figure 5As shown in the following formula (1), the number of initial modules required for each of the M-1 first groups is... and rated operating voltage U i * The product of the product and the statistical quantity S of the capacitor voltage of each normal power module in the first group. i They are directly proportional:

[0091]

[0092] Where i = 1 to N, N = M-1.

[0093] Furthermore, the number of initial modules required for each of the M-1 first groups. It can be determined by the following formula (2):

[0094]

[0095] In formula (2), round is the rounding function, and i = 1 to (M-1) are constraints on the subscripts i other than the i used in the summation symbol ∑.

[0096] In addition, after determining the bridge arm current I arm When the direction of the current is the charging direction, such as Figure 5 As shown in the following formula (3), the number of initial modules required for each of the M-1 first groups is... and rated operating voltage The product of the product and the statistical quantity S of the capacitor voltage of each normal power module in the first group. i Inversely proportional:

[0097]

[0098] Furthermore, the number of initial modules required for each of the M-1 first groups. It can be determined by the following formula (4):

[0099]

[0100] Based on the formula (2) or formula (4) as described above, determine Afterwards, it can be based on Determine the number of power modules required for each of the M-1 first groups. This is used for modulation calculations to achieve amplitude limiting. For example, when the i-th initial group needs to deploy a certain number of modules... The number of modules greater than the number of normal power modules in the i-th group of the first group season when season

[0101] Next, let's take the first reference voltage U as an example. arm Taking a negative value, where the first module is called the normal power module, as an example, the method for determining the initial number of modules to be put into each of the M-1 first groups will be illustrated. According to the description above, at the first reference voltage U... arm When the value is negative, each normal full-bridge power module in each of the M groups is a target module, and the number of modules in each of the M groups' normal full-bridge power modules is... The calculation involves determining the number of initial modules required for each of the M-1 first groups.

[0102] First reference voltage U arm It is negative, and the bridge arm current I arm When the current direction is the discharge direction, as shown in the following formula (5), the number of initial modules that need to be put into each of the M-1 first groups is... and rated operating voltage The product of the product and the statistical quantity S of the capacitor voltage of each normal full-bridge power module in the first group. FBi Inversely proportional:

[0103]

[0104] Furthermore, the number of initial modules required for each of the M-1 first groups. It can be determined by the following formula (6):

[0105]

[0106] In addition, the first reference voltage U arm It is negative, and the bridge arm current I arm When the current direction is the charging direction, as shown in the following formula (7), the number of initial modules that need to be put into each of the M-1 first groups is... and rated operating voltage The product of the product and the statistical quantity S of the capacitor voltage of each normal full-bridge power module in the first group. FBi They are directly proportional:

[0107]

[0108] Furthermore, the number of initial modules required for each of the M-1 first groups. It can be determined by the following formula (8):

[0109]

[0110] For the explanation of the subscript N in formulas (3), (5), and (7), and i = 1 to (M-1) in formulas (4), (6), and (8), please refer to the relevant explanations of formulas (1) and (2) above. They will not be repeated here.

[0111] Based on the formula (6) or formula (8) as described above, determine Afterwards, it can be based on Determine the number of power modules required for each of the M-1 first groups. For example, when the i-th first group needs to invest the initial number of modules The number of modules greater than the number of normal full-bridge power modules in the i-th group of the first group season when season

[0112] In step S2075, according to the first reference voltage U arm The number of power modules required for the first group (M-1) and their rated operating voltages, as well as the rated operating voltages of the second group, are used to determine the number of power modules required for the second group.

[0113] Specifically, taking M-1 as the first group (groups 1 to M-1) of group M, and the second group (group M) as the third group of group M, considering that the initial number of modules required for groups 1 to M-1 are rounded, the reference voltage of group M needs to be corrected, and the number of power modules required for group M is... It can be determined using the following formula (9):

[0114]

[0115] In one implementation, after determining the number of power modules required for each of the M-1 first groups based on the initial number of modules required for each of the M-1 first groups, reference voltage modulation can also be performed. For example, if the M-1 first groups include at least one target group, and the number of initial modules required for any target group is greater than the number of modules in each target module of that target group, after determining that the number of power modules required for each target group in the at least one target group is equal to the number of modules in each target module of that target group, the second reference voltage U' corresponding to each of the other groups in the M groups besides the at least one target group can also be determined. arm Second reference voltage U' arm The first reference voltage U arm The difference between the second value and the third value is the sum of the third values ​​corresponding to the at least one target group. The third value corresponding to any target group is the product of the number of target modules in the target group and the rated operating voltage.

[0116] Continuing with the example of M-1 groups, where the first group represents groups 1 to M-1 within group M, and the second group represents group M within group M, the following applies. Under the first reference voltage U... arm If the value is positive, assuming that at least one of the target groups mentioned above is the j-th group in group M, let... Then, the second reference voltage U' corresponding to the other groups mentioned above can be... arm Adjusted to And satisfy the following relationship:

[0117] And i≠j.

[0118] Further assume that at least one of the target groups mentioned above is the j-th group, the k-th group, ... in group M, and let After that, it can be like Figure 5 As shown, the second reference voltage U' corresponding to the other groups mentioned above arm Adjusted to And satisfy the following relationship:

[0119] And i≠j, k...

[0120] In addition, such as Figure 5 As shown, the number of power modules required for each of the M groups is... and rated operating voltage The following relationship must be satisfied:

[0121]

[0122] In one embodiment, all power modules of the target bridge arm can be divided into M groups based on their rated operating voltages, where different groups have different rated operating voltages. Then, a first reference voltage of the target bridge arm can be compared with zero to obtain a comparison result. If the comparison result indicates that the first reference voltage is not equal to zero, the following steps are performed:

[0123] Obtain the bridge arm current of the target bridge arm and determine the current direction of the bridge arm current;

[0124] Based on the sign of the first reference voltage of the target bridge arm, the target module is determined in each of the first modules of each of the M groups, and the statistical values ​​of the capacitor voltage of each target module in each of the M groups are obtained; wherein, the first module is the power module that has not experienced a fault.

[0125] Based on the first reference voltage, the aforementioned current direction, the number of target modules in each of the M groups, the aforementioned statistics, and the rated operating voltage, the number of power modules that need to be put into each of the M groups is determined; wherein, the sum of the first values ​​corresponding to each of the M groups is equal to the first reference voltage, and the first value corresponding to any group in the M groups is the product of the number of power modules that need to be put into that group and the rated operating voltage.

[0126] Alternatively, if the comparison result indicates that the first reference voltage is equal to zero, the following steps can be performed:

[0127] Determine that the number of power modules required for each of groups M is zero; or,

[0128] Divide the M groups into at least two sets and assign a corresponding third reference voltage to each set, such that the sum of the third reference voltages corresponding to the at least two sets is equal to zero.

[0129] Wherein, the aforementioned at least two sets comprise different groups from the M groups. Any two sets comprise either the same or different numbers of groups. Taking sets M1 and M2 as examples, a third reference voltage +U can be assigned to set M1, and a third reference voltage -U can be assigned to set M2; where U>0. In practice, a target strategy can be configured according to actual needs. The target strategy describes the method for dividing the M groups into sets and the method for assigning a corresponding third reference voltage to each of the divided sets. According to the target strategy, the M groups can be divided into at least two sets, and a corresponding third reference voltage can be assigned to each set, such that the sum of the third reference voltages corresponding to the at least two sets is equal to zero.

[0130] It should be noted that by determining that the number of power modules needed for each of the M groups is zero when the first reference voltage is zero, it is possible to quickly determine the number of power modules needed for each of the M groups under the special condition that the first reference voltage is zero.

[0131] In addition, by dividing the M groups into at least two sets when the first reference voltage is equal to zero, and assigning a corresponding third reference voltage to each set, such that the sum of the third reference voltages corresponding to the at least two sets is equal to zero, it is possible to quickly determine the third reference voltage corresponding to each set divided from the M groups in the special case where the first reference voltage is equal to zero.

[0132] Figure 6 This is a schematic diagram of the control device for a modular multilevel converter in an embodiment of this application. The target arm of the converter valve in this converter has power modules with various rated operating voltages. This device can be applied, for example, to a converter valve control and protection system. The device includes:

[0133] Grouping unit 601 is configured to divide all power modules of the target arm into M groups according to their rated operating voltages, wherein the rated operating voltages of the different groups are different;

[0134] The acquisition unit 602 is configured to acquire the arm current of the target arm and determine the current direction of the arm current;

[0135] The first determining unit 603 is configured to determine the target module in each of the first modules of each of the M groups based on the sign of the first reference voltage of the target bridge arm, and to obtain the statistics of the capacitor voltage of each of the target modules in each of the M groups; wherein, the first module is the power module that has not experienced a fault.

[0136] The second determining unit 604 is configured to determine the number of power modules that need to be put into each of the M groups based on the first reference voltage of the target bridge arm, the current direction of the target bridge arm, the number of each target module in each of the M groups, the aforementioned statistics and the rated operating voltage; wherein, the sum of the first values ​​corresponding to each of the M groups is equal to the first reference voltage, and the first value corresponding to any group in the M groups is the product of the number of power modules that need to be put into that group and the rated operating voltage.

[0137] In one embodiment, the control device further includes:

[0138] A comparison unit (not shown in the figure) is configured to compare a first reference voltage with zero to obtain a comparison result;

[0139] The acquisition unit 602 is configured to acquire the arm current of the target arm, including:

[0140] The acquisition unit 602 is configured to acquire the arm current of the target arm in response to the comparison result of the first reference voltage being equal to zero.

[0141] In one implementation, the first determining unit 603 is configured to determine a target module in each of the M groups of first modules based on the sign of the first reference voltage of the target bridge arm, including:

[0142] The first determining unit 603 is configured to determine each of the first modules of each of the M groups as the target module in response to a positive first reference voltage.

[0143] In one implementation, at least a portion of the first module of the target bridge arm has a topology type of full bridge;

[0144] The first determining unit 603 is configured to determine the target module in each of the M groups of first modules based on the sign of the first reference voltage of the target bridge arm, including:

[0145] The first determining unit 603 is configured to determine each of the first modules of the M groups, each with a full-bridge topology, as the target module in response to a negative first reference voltage.

[0146] In one embodiment, the second determining unit 604 is configured to determine the number of power modules that need to be put into operation in each of the M groups based on the first reference voltage, the current direction, the number of modules of each target module in each of the M groups, the statistics, and the rated operating voltage, including:

[0147] In the M groups, identify M-1 first groups and one second group;

[0148] Based on the first reference voltage, the current direction of the bridge arm current, the number of each target module in each of the M groups, the above statistics, and the rated operating voltage of each of the M-1 first groups, determine the number of power modules that need to be put into each of the M-1 first groups.

[0149] Based on the first reference voltage, the number of power modules required for each of the M-1 first groups and their rated operating voltages, as well as the rated operating voltage of the second group, the number of power modules required for the second group is determined.

[0150] In one implementation, the first reference voltage is positive;

[0151] The second determining unit 604 is configured to determine the number of power modules that need to be put into each of the M-1 first groups based on the first reference voltage, the current direction of the bridge arm current, the number of each target module in each of the M groups, the aforementioned statistics, and the rated operating voltage of each of the M-1 first groups, including:

[0152] Based on the first reference voltage, the current direction of the bridge arm current, the number of each target module in each of the M groups, the above statistics, and the rated operating voltage of each of the M-1 first groups, determine the number of initial modules that need to be put into each of the M-1 first groups; wherein, the product of the number of initial modules that need to be put into any first group and the rated operating voltage is in a first proportional relationship with the above statistics of each target module in that first group. The first proportional relationship is a direct proportional relationship when the current direction of the bridge arm current is the discharge direction, and an inverse proportional relationship when the current direction of the bridge arm current is the charging direction.

[0153] Based on the initial number of modules required for each of the M-1 first groups, determine the number of power modules required for each of the M-1 first groups.

[0154] In one implementation, the first reference voltage is negative;

[0155] The second determining unit 604 is configured to determine the number of power modules that need to be put into each of the M-1 first groups based on the first reference voltage, the current direction of the bridge arm current, the number of each target module in each of the M groups, the aforementioned statistics, and the rated operating voltage of each of the M-1 first groups, including:

[0156] Based on the first reference voltage, the current direction of the bridge arm current, the number of each target module in each of the M groups, the above statistics, and the rated operating voltage of each of the M-1 first groups, determine the number of initial modules that need to be put into each of the M-1 first groups; wherein, the product of the number of initial modules that need to be put into any first group and the rated operating voltage is in a second proportional relationship with the above statistics of each target module in that first group. The second proportional relationship is inversely proportional when the current direction of the bridge arm current is the discharge direction, and directly proportional when the current direction of the bridge arm current is the charging direction.

[0157] Based on the initial number of modules required for each of the M-1 first groups, determine the number of power modules required for each of the M-1 first groups.

[0158] In one implementation, the M-1 first groups include at least one target group, and the number of initial modules required for any target group is greater than the number of modules in each target module of that target group.

[0159] The second determining unit 604 is configured to determine the number of power modules that need to be put into each of the M-1 first groups based on the initial number of modules that each of the first groups needs to put into operation, including:

[0160] The second determining unit 604 is configured to determine that the number of power modules required for each target group in the at least one target group is equal to the number of modules in each target module of that target group.

[0161] In one implementation, the second determining unit 604 is further configured to:

[0162] After determining that the number of power modules required for each target group in the above at least one target group is equal to the number of modules of each target module in that target group, the second reference voltage corresponding to each group in M ​​other than the above at least one target group is determined. The second reference voltage is the difference between the first reference voltage and the second value. The second value is the sum of the third values ​​corresponding to the above at least one target group respectively. The third value corresponding to any target group is the product of the number of modules of each target module in that target group and the rated operating voltage.

[0163] In one implementation, the above statistics include any one of the following: mean capacitor voltage, sum of capacitor voltage, minimum capacitor voltage, maximum capacitor voltage, sum of squares of capacitor voltage, target power, and target energy;

[0164] Both the target power and the target energy are determined based on the capacitor voltage, the arm current, or the arm resistance of the target arm.

[0165] In one implementation, the second determining unit 604 is further configured to:

[0166] In response to the above comparison result that the first reference voltage is equal to zero, it is determined that the number of power modules that need to be put into each of the M groups is zero.

[0167] In one implementation, the second determining unit 604 is further configured to:

[0168] In response to the comparison result that the first reference voltage is equal to zero, the M groups are divided into at least two sets, and a corresponding third reference voltage is assigned to each set, such that the sum of the third reference voltages corresponding to the at least two sets is equal to zero.

[0169] It should be noted that other aspects and implementation details of the signal acquisition device provided in this application embodiment are the same as or similar to the signal acquisition method described above, and will not be repeated here.

[0170] This application embodiment also provides a computer device, which includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, it implements, for example, […]. Figure 2 The control method for a modular multilevel converter is described.

[0171] This application embodiment also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the following... Figure 2 The control method for a modular multilevel converter is described.

[0172] This application also provides a computer program product, including a computer program / instructions, which, when executed by a processor, implements the following: Figure 2 The control method for a modular multilevel converter is described.

[0173] The above description is only a partial implementation of the embodiments of this application and is not intended to limit the application in any way. The protection scope of the embodiments of this application is not limited thereto. Any simple modifications, equivalent changes and alterations that can be easily conceived by those skilled in the art within the technical scope disclosed in the embodiments of this application should be included within the protection scope of the embodiments of this application.

Claims

1. A control method for a modular multilevel converter, characterized in that, The target bridge arm of the converter valve in the converter has power modules with multiple rated operating voltages, and the method includes: Based on the different rated operating voltages, all power modules of the target bridge arm are divided into M groups, where the rated operating voltages of different groups are different, and M is a natural number greater than 1. Obtain the bridge arm current of the target bridge arm and determine the current direction of the bridge arm current; Based on the sign of the first reference voltage of the target bridge arm, the target module is determined in each of the first modules of each of the M groups, and the statistical value of the capacitor voltage of each of the target modules in each of the M groups is obtained; wherein, the first module is a power module that has not experienced a fault. Based on the first reference voltage, the current direction, the number of target modules in each of the M groups, the statistics, and the rated operating voltage, the number of power modules that need to be put into each of the M groups is determined; wherein, the sum of the first values ​​corresponding to each of the M groups is equal to the first reference voltage, and the first value corresponding to any group in the M groups is the product of the number of power modules and the rated operating voltage of that group.

2. The method according to claim 1, characterized in that, Also includes: The first reference voltage is compared with zero to obtain the comparison result; Obtaining the bridge arm current of the target bridge arm includes: In response to the comparison result that the first reference voltage is not equal to zero, the bridge arm current of the target bridge arm is obtained.

3. The method according to claim 1, characterized in that, Based on the sign of the first reference voltage of the target bridge arm, the target module is determined in each of the first modules of the M groups, including: In response to the first reference voltage being positive, each of the first modules in each of the M groups is determined as the target module.

4. The method according to claim 1, characterized in that, At least a portion of the first module of the target bridge arm has a topology type of full bridge; Based on the sign of the first reference voltage of the target bridge arm, the target module is determined in each of the first modules of the M groups, including: In response to the first reference voltage being negative, each of the first modules in the M groups, whose respective topology type is full bridge, is determined as the target module.

5. The method according to any one of claims 1-4, characterized in that, Based on the first reference voltage, the current direction, the number of target modules in each of the M groups, the statistics, and the rated operating voltage, the number of power modules required for each of the M groups is determined, including: From the M groups, M-1 first groups and one second group are identified; The number of power modules in each of the M-1 first groups is determined based on the first reference voltage, the current direction, the number of modules in each of the target modules in each of the M groups, the statistics, and the rated operating voltage of each of the M-1 first groups. Based on the first reference voltage, the number of power modules and rated operating voltage of each of the M-1 first groups, and the rated operating voltage of the second group, the number of power modules in the second group is determined.

6. The method according to claim 5, characterized in that, The first reference voltage is positive; Based on the first reference voltage, the current direction, the number of target modules in each of the M groups, the statistics, and the rated operating voltage of each of the M-1 first groups, the number of power modules in each of the M-1 first groups is determined, including: Based on the first reference voltage, the current direction, the number of target modules in each of the M groups, the statistical value, and the rated operating voltage of each of the M-1 first groups, the initial number of modules to be put into each of the M-1 first groups is determined; wherein, the product of the initial number of modules and the rated operating voltage of any first group is proportional to the statistical value of each target module in the first group, the first proportional relationship is a direct proportional relationship when the current direction is the discharge direction, and an inverse proportional relationship when the current direction is the charging direction; The number of power modules in each of the M-1 first groups is determined based on the initial number of modules in each of the first groups.

7. The method according to claim 5, characterized in that, The first reference voltage is negative; Based on the first reference voltage, the current direction, the number of target modules in each of the M groups, the statistics, and the rated operating voltage of each of the M-1 first groups, the number of power modules in each of the M-1 first groups is determined, including: Based on the first reference voltage, the current direction, the number of target modules in each of the M groups, the statistical value, and the rated operating voltage of each of the M-1 first groups, the initial number of modules to be put into each of the M-1 first groups is determined; wherein, the product of the initial number of modules and the rated operating voltage of any first group is in a second proportional relationship with the statistical value of each target module in the first group, the second proportional relationship being inversely proportional when the current direction is the discharge direction and directly proportional when the current direction is the charging direction; The number of power modules in each of the M-1 first groups is determined based on the initial number of modules in each of the first groups.

8. The method according to claim 6 or 7, characterized in that, The M-1 first groups include at least one target group, and the number of initial modules in any target group is greater than the number of modules in each target module of the target group; Determining the number of power modules in each of the M-1 first groups based on the initial module number of each of the M-1 first groups includes: The number of power modules in each target group of the at least one target group is determined to be equal to the number of modules in each target module of the target group.

9. The method according to claim 8, characterized in that, After determining that the number of power modules in each target group in the at least one target group is equal to the number of modules in each target module of the target group, the method further includes: Determine the second reference voltage for each group in the M groups other than the at least one target group. The second reference voltage is the difference between the first reference voltage and the second value. The second value is the sum of the third values ​​corresponding to the at least one target group. The third value corresponding to any one of the target groups is the product of the number of modules of each target module in the target group and the rated operating voltage.

10. The method according to claim 1, characterized in that, The statistics include any of the following: mean capacitor voltage, sum of capacitor voltage, minimum capacitor voltage, maximum capacitor voltage, sum of squares of capacitor voltage, target power, and target energy. Both the target power and the target energy are determined based on the capacitor voltage, the bridge arm current, or the bridge arm resistance of the target bridge arm.

11. The method according to claim 2, characterized in that, Also includes: In response to the comparison result that the first reference voltage is equal to zero, it is determined that the number of power modules in each of the M groups is zero.

12. A control device for a modular multilevel converter, characterized in that, The target arm of the converter valve in the converter has power modules with various rated operating voltages, and the device includes: The grouping unit is configured to divide all power modules of the target bridge arm into M groups according to their rated operating voltages, wherein the rated operating voltages of the different groups are different, and M is a natural number greater than 1; The acquisition unit is configured to acquire the arm current of the target arm and determine the current direction of the arm current; The first determining unit is configured to determine the target module in each of the M groups of first modules based on the sign of the first reference voltage of the target bridge arm, and to obtain statistics on the capacitor voltage of each of the M groups of target modules; wherein the first module is a power module that has not experienced a fault. The second determining unit is configured to determine the number of power modules that need to be put into each of the M groups based on the first reference voltage, the current direction, the number of each target module in each of the M groups, the statistics, and the rated operating voltage; wherein the sum of the first values ​​corresponding to each of the M groups is equal to the first reference voltage, and the first value corresponding to any group in the M groups is the product of the number of power modules and the rated operating voltage of that group.

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