WO2021169120A1

WO2021169120A1 - Sub-module redundancy configuration method and system of modular multilevel converter

Info

Publication number: WO2021169120A1
Application number: PCT/CN2020/099133
Authority: WO
Inventors: 许彬; 李景波; 宁志彦; 王高勇; 周军川
Original assignee: 全球能源互联网研究院有限公司
Priority date: 2020-02-24
Filing date: 2020-06-30
Publication date: 2021-09-02
Also published as: CN111211675A

Abstract

Disclosed are a sub-module redundancy configuration method and system of a modular multilevel converter. The method comprises: determining the number of fault sub-modules in the modular multilevel converter; calculating to obtain a capacitance reference voltage of the sub-modules of the modular multilevel converter on the basis of the number of the fault sub-modules; obtaining a target output voltage of an upper bridge arm and a target output voltage of a lower bridge arm of the modular multilevel converter; and determining, by using the capacitance reference voltage and the target output voltage of the upper bridge arm, the number of sub-modules input by the upper bridge arm, and determining, by using the capacitance reference voltage and the target output voltage of the lower bridge arm, the number of sub-modules input by the lower bridge arm.

Description

Sub-module redundant configuration method and system of modular multilevel converter

This application claims the priority of a Chinese patent application filed with the Chinese Patent Office with an application number of 202010112266.0 on February 24, 2020, and the entire content of the application is incorporated into this application by reference.

Technical field

This application relates to the field of flexible direct current transmission, for example, to a method and system for redundant configuration of sub-modules of a modular multilevel converter.

Background technique

Modular multilevel converter (MMC) has the advantages of high degree of modularity, low switching frequency, low harmonic content, flexible and independent control of active and reactive power, etc. It has a wide range of applications in the field of medium and high voltage DC transmission , Is an important technical plan for building the future power grid and delivering clean energy.

A single bridge arm of the high-voltage and large-capacity MMC contains hundreds of power sub-modules. The output voltage of the bridge arm is superimposed by the output voltage of each sub-module. In order to ensure the uninterrupted operation of the MMC when the sub-module fails and improve the operational reliability, it is configured in the project Redundant sub-module, once a sub-module fails, the bypass switch action will remove it, and then put in the redundant module to replace the failed module to run. In the high-voltage and large-capacity MMC projects of related technologies, redundant sub-modules ranging from 6% to 15% are configured to enable the MMC to operate normally after a sub-module bypass failure. The sub-modules in the related technology are redundant. The configuration methods are adopted: during the period of no fault, the redundant module only participates in the voltage equalization switching of the capacitor, without increasing the maximum output level of the system; when a sub-module failure occurs, the redundant module will replace the failed module to participate in the maximum level construction , So the redundant modules are not fully utilized.

Summary of the invention

The embodiment of the application provides a method and system for redundant configuration of sub-modules of a modular multilevel converter, which solves the problem of overvoltage damage and redundancy of capacitive equipment caused by the total input power of the system in the related art because the total input power of the system is greater than the output power of the system. The problem that the module is not fully utilized.

This application provides the following technical solutions:

The embodiment of the present application provides a sub-module redundancy configuration method of a modular multi-level converter, including the following steps: determining the number of faulty sub-modules in the modular multi-level converter; The number of sub-modules is calculated to obtain the capacitance reference voltage of the sub-module of the modular multilevel converter; the target output voltage of the upper bridge arm and the target output of the lower bridge arm of the modular multilevel converter are obtained Voltage; using the capacitor reference voltage and the target output voltage of the upper bridge arm to determine the number of sub-modules invested in the upper bridge arm, and using the capacitor reference voltage and the target output voltage of the lower bridge arm to determine The number of sub-modules put into the lower bridge arm.

The embodiment of the present application provides a sub-module redundancy configuration system of a modular multi-level converter, which includes a module for determining the number of faulty sub-modules, configured to determine the faulty sub-modules in the modular multi-level converter. The number of modules; a calculation module, configured to calculate the capacitance reference voltage of the sub-modules of the modular multilevel converter based on the number of the faulty sub-modules; an acquisition module, configured to acquire the modular multilevel The target output voltage of the upper bridge arm of the converter and the target output voltage of the lower bridge arm; the input sub-module number determining module is set to use the capacitor reference voltage and the target output voltage of the upper bridge arm to determine the The number of sub-modules invested in the upper bridge arm is determined by using the capacitor reference voltage and the target output voltage of the lower bridge arm to determine the number of sub-modules invested in the lower bridge arm.

An embodiment of the present application provides an electronic device, including: at least one processor, and a memory communicatively connected with the at least one processor, where the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor , So that at least one processor executes the sub-module redundancy configuration method of the modular multilevel converter described in any embodiment of the present application.

The embodiment of the present application provides a computer-readable storage medium. The computer-readable storage medium stores computer instructions. The computer instructions are used to make the computer execute the redundant sub-modules of the modular multilevel converter described in any embodiment of the present application. I configuration method.

Description of the drawings

In order to describe the technical solutions in the embodiments of the present application or related technologies, the following will briefly introduce the drawings used in the embodiments of the present application or related technologies.

FIG. 1 is a flowchart of an example of a redundant configuration method for sub-modules of a modular multilevel converter provided by an embodiment of the application;

Fig. 2 is a topological structure diagram of a modular multilevel converter provided by an embodiment of the application;

FIG. 3 is a flowchart of an example of obtaining a target output voltage according to an embodiment of the application;

FIG. 4 is a flowchart of an example of calculating a capacitor reference voltage provided by an embodiment of the application;

FIG. 5 is a flowchart of an example of calculating the number of redundant sub-modules put into use according to an embodiment of the application;

Fig. 6a is the simulation result diagram of the capacitor voltage waveform of the sub-module when the conventional redundant configuration method is adopted;

FIG. 6b is a diagram showing the simulation result of the capacitor voltage waveform of the sub-module when the redundant configuration method of the sub-module of the modular multi-level converter provided by the embodiment of the present application is adopted;

Fig. 7a is a simulation result diagram of the device loss of the sub-module under the rectification condition when the conventional redundant configuration method is adopted;

Figure 7b is a simulation result diagram of the device loss of the sub-module under inverter conditions when the conventional redundant configuration method is adopted;

FIG. 7c is a diagram showing the simulation results of device loss of sub-modules under rectification conditions when the sub-module redundancy configuration method of the modular multi-level converter provided by the embodiment of the present application is adopted;

FIG. 7d is a diagram showing the simulation results of the device loss of the sub-modules under inverter operating conditions when the sub-module redundancy configuration method of the modular multi-level converter according to the embodiment of the present application is adopted;

FIG. 8 is a diagram of a simulation result of a fault ride-through waveform of a sub-module of a conventional redundant configuration method provided by an embodiment of the application;

FIG. 9 is a simulation result diagram of a sub-module fault ride-through waveform of a sub-module redundancy configuration method of a modular multi-level converter provided by an embodiment of the application;

10 is a schematic diagram of a redundant configuration system for sub-modules of a modular multilevel converter provided by an embodiment of the application;

FIG. 11 is a composition diagram of an example of an electronic device provided by an embodiment of the application.

Detailed ways

The technical solution of the present application will be described below in conjunction with the accompanying drawings. The described embodiments are a part of the embodiments of the present application, rather than all of the embodiments.

In the description of this application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. The indicated orientation or positional relationship is based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the application and simplifying the description, and does not indicate or imply that the pointed device or element must have a specified orientation or a specified orientation. The structure and operation cannot therefore be understood as a limitation of this application. In addition, the terms "first", "second", and "third" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance.

In the description of this application, it should be noted that the terms "installation", "connection", and "connection" should be understood in a broad sense, unless otherwise clearly specified and limited. For example, it can be a fixed connection or a detachable connection. Connected or integrally connected; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be the internal connection of the two components, it can be a wireless connection, or it can be a wired connection connect. For those of ordinary skill in the art, the meaning of the above terms in this application can be understood according to actual conditions.

Example 1

The embodiment of the present application provides a sub-module redundancy configuration method of a modular multi-level converter, as shown in FIG. 1, including the following steps:

Step S110: Determine the number of faulty sub-modules in the modular multilevel converter.

In the embodiment of this application, as shown in Figure 2, a single bridge arm of the modular multilevel converter contains hundreds of power sub-modules. The structure of the sub-modules can be divided into half-H bridge type, full-H bridge type and There are three types of dual-clamp sub-modules. Once a sub-module fails, the bypass switch will act to remove the faulty sub-module, and then put the redundant sub-module to replace the failed sub-module. The system can pass the fault detector to The sub-module detects, if the sub-module fails, the fault detector adds 1 to the statistical number of the failed sub-module and feeds back the statistical result to the system to determine the number of failed sub-modules in the modular multi-level converter . The fault detector can be a chip or an actual detection program, and this application is not limited to this.

Step S120: Calculate the capacitor reference voltage of the sub-module of the modular multilevel converter based on the number of the faulty sub-modules.

In the embodiment of the present application, the capacitor reference voltage of the sub-module is calculated by dividing the DC terminal voltage of the converter by the total number of sub-modules in normal operation. The total number of sub-modules in normal operation can be the sum of the number of regular sub-modules and the number of redundant sub-modules, or the sum of the number of regular sub-modules and the number of redundant sub-modules minus the number of faulty sub-modules. The number can also be the number of sub-modules obtained by adding a base number or weighting to the sum of the number of regular sub-modules and the number of redundant sub-modules, or the number of sub-modules obtained after the number of regular sub-modules and The sum of the number of sub-modules minus the number of faulty sub-modules is added with a base or the total number of sub-modules after weighting. In practical applications, the proportion of each sub-module in the weighting process can be determined according to the actual needs of the system. After making corresponding adjustments, this application is not limited to this.

In practical applications, each sub-module of the modular multi-level converter has a capacitor, and the capacitors of multiple sub-modules do not interfere with each other. The sub-modules of the modular multi-level converter are calculated based on the number of faulty sub-modules. Capacitor reference voltage, when the converter is working, it is impossible to accurately control the continuous charging and discharging process of the sub-modules. In addition, problems such as operating loss will cause voltage imbalances between the capacitors of multiple sub-modules and cause abnormal operation of the converter. Therefore, it is necessary to pay attention to and maintain the sub-module capacitor voltage in real time. Only when the sub-module capacitor voltage is balanced and stable can the converter operate normally.

Step S130: Obtain the target output voltage of the upper bridge arm and the target output voltage of the lower bridge arm of the modular multilevel converter.

In the embodiment of the present application, the target output voltage of the upper bridge arm and the target output voltage of the lower bridge arm of the modular multilevel converter are determined according to the AC terminal voltage and the DC terminal voltage preset by the system. The target output voltage is obtained through preset parameters, and the target output voltage also determines the adjustment of subsequent modules and the calculation of the number of input sub-modules. In practical applications, the target output voltage of the upper bridge arm and the target output voltage of the lower bridge arm of the converter are set according to the actual needs of the system, and the application is not limited thereto.

Step S140: Use the capacitor reference voltage and the target output voltage of the upper bridge arm to determine the number of sub-modules input to the upper bridge arm, and use the capacitor reference voltage and the target output voltage of the lower bridge arm to determine the number of sub-modules input to the lower bridge arm .

In the embodiment of this application, the number of sub-modules invested in the upper bridge arm is the ratio of the target output voltage of the upper bridge arm to the capacitor reference voltage, and the round[] function is rounded to obtain the integer. The number of sub-modules invested in the lower bridge arm is the lower bridge arm. The ratio of the target output voltage to the capacitor reference voltage is rounded by the round[] function. The round[] function returns a value, which is the result of the rounding operation according to the specified number of decimal places. For the calculation of the number of sub-modules invested in the upper bridge arm and the number of sub-modules invested in the lower bridge arm, other rounding functions can also be selected, such as the round-down function, which can be used to return a decimal integer value. For example, 4.323, return 4, it is not rounding, but rounding method, even 4.987, it also returns 4; there are also round-up functions, etc., in practical applications, you can select the corresponding function according to the requirements of system accuracy. This application does not Not limited to this.

Optionally, the number of sub-modules input to the upper bridge arm and the number of sub-modules input to the lower bridge arm can be determined by the following formula using the capacitor reference voltage and the target output voltage of the upper bridge arm:

In formula (1), N _pa (t) represents the number of sub-modules input by the bridge arm at the current time t, N _na (t) represents the number of sub-modules input by the bridge arm at the current time t, and round[] represents rounding Function, u _pa (t) represents the target output voltage of the upper bridge arm at the current time t, u _na (t) represents the target output voltage of the lower bridge arm at the current time t, and u _c * represents the capacitor reference voltage of the sub-module.

The redundant configuration method for the sub-modules of the modular multi-level converter provided in this application calculates the capacitance reference voltage of the sub-modules of the modular multi-level converter through the number of faulty sub-modules, and then uses the capacitance reference voltage and the upper The target output voltage of the bridge arm determines the number of sub-modules input in the upper bridge arm, and the capacitor reference voltage and the target output voltage of the lower bridge arm are used to determine the number of sub-modules input in the lower bridge arm, so that the capacitor reference voltage of the sub-module is reduced. , The loss of the converter valve is reduced; when the number of faulty modules is greater than the number of redundant modules, the system will also retain the maximum voltage output capacity by increasing the capacitor voltage, so that it will not produce violent oscillations, and it can still operate stably, which enhances Fault ride-through capability; and make full use of redundant modules, not only participate in voltage equalization, but also increase the number of system levels, thereby reducing the output voltage harmonic content, and improving the operating performance of the modular multi-level converter.

In an embodiment, as shown in FIG. 3, obtaining the target output voltage of the upper bridge arm and the target output voltage of the lower bridge arm of the modular multilevel converter includes the following steps:

Step S1310: Obtain the DC terminal voltage and the AC terminal voltage of the modular multilevel converter.

In the embodiments of the present application, inverters can be divided into two types: rectifiers and inverters. The rectifier converts alternating current into direct current, and the inverter converts direct current into alternating current. Assuming that the converter of the embodiment of the present application is a rectifier, the input terminal is an AC voltage, then the AC terminal voltage is a known input voltage, and the output terminal DC voltage is determined according to the internal structure of the converter and system requirements . In the embodiments of this application, the converter is only exemplified as a rectifier. In actual applications, it can also be other types of converters, and the output terminal voltage can also be adjusted according to the actual needs of the system. This application is not limited to this. .

Step S1320: Calculate the target output voltage of the upper bridge arm and the target output voltage of the lower bridge arm by using the DC terminal voltage and the AC terminal voltage.

In the embodiment of the present application, the target output voltage of the upper bridge arm can be a base multiple of the DC terminal voltage minus the AC terminal voltage, or a base multiple of the DC terminal voltage minus a base multiple of the AC terminal voltage; The target output voltage can be a base multiple of the DC terminal voltage plus the AC terminal voltage, or a base multiple of the DC terminal voltage plus a base multiple of the AC terminal voltage, minus the AC terminal voltage or plus the DC terminal voltage is It is determined according to the preset current flow direction, and this application is not limited to this.

Optionally, use the DC terminal voltage and the AC terminal voltage to calculate the target output voltage of the upper bridge arm and the target output voltage of the lower bridge arm through the following formulas:

In formula (2), u _pa (t) represents the target output voltage of the upper bridge arm at the current time t, u _na (t) represents the target output voltage of the lower bridge arm at the current time t, U _dc represents the DC terminal voltage, u _sa ( t) represents the AC terminal voltage at the current time t.

In one embodiment, as shown in FIG. 4, calculating the capacitor reference voltage of the submodule of the modular multilevel converter based on the number of faulty submodules includes the following steps:

Step S1210: Obtain the number of regular sub-modules and the total number of redundant sub-modules put in.

The number of regular sub-modules is the minimum number of sub-modules required to maintain the normal operation of the system without failure, and the total number of redundant sub-modules is the number of all redundant sub-modules set in advance.

In the embodiment of the present application, the system will pre-set the number of conventional sub-modules that need to be invested and the total number of redundant sub-modules in the system, so that after a module failure occurs, the failure adjustment can be adjusted and replaced in a timely manner. The number of conventional sub-modules is the number of sub-modules that are normally put into use without failure, and the total number of redundant sub-modules is the number of all redundant sub-modules set in advance. In practical applications, the number of conventional sub-modules and The total number of redundant sub-modules is set according to actual needs, and this application is not limited to this.

Step S1220: Calculate the capacitor reference voltage by using the number of regular submodules, the total number of redundant submodules, and the number of faulty submodules.

In the embodiment of this application, the capacitor reference voltage of the sub-module is calculated by dividing the DC terminal voltage of the converter by the total number of sub-modules in normal operation. The total number of sub-modules in normal operation can be the sum of the number of regular sub-modules and redundant sub-modules. It is the total number of sub-modules when no sub-module fails; the total number of sub-modules in normal operation can also be the sum of the number of regular sub-modules and the number of redundant sub-modules minus the number of failed sub-modules It can also be based on the different performance and parameters of multiple sub-modules, adding a base or weighted number of sub-modules to the sum of the number of regular sub-modules and the number of redundant sub-modules, or the number of sub-modules in the regular sub-modules. The sum of the number of modules and the number of redundant sub-modules minus the number of faulty sub-modules plus a base or weighted number of sub-modules. In actual applications, the proportion of each sub-module in the weighting process can be adjusted according to the actual needs of the system, and the application is not limited to this. The number of failed modules changes with time t.

Optionally, the capacitor reference voltage of the sub-module is calculated by the following formula:

In formula (3), u _c * represents the capacitor reference voltage of the sub-module, U _dc represents the DC terminal voltage, N represents the number of regular sub-modules, N _r represents the total number of redundant sub-modules, and N _f (t) represents the current Number of faulty sub-modules at time t. In practical applications, the capacitor reference voltage of the conventional redundant configuration method is a fixed constant, U _dc /N, which may cause the capacitor reference voltage to become more and more unstable as the number of faulty sub-modules increases. The loss of the converter valve makes the system more and more unstable; however, the capacitor reference voltage of the redundant configuration method for the sub-modules of the modular multi-level converter proposed in the embodiment of this application increases with the number of faulty modules N _f (t ) The dynamic adjustment ensures the stability of the capacitor reference voltage, thereby reducing the loss of the converter valve and ensuring the stability and safety of the system operation.

In the embodiment of this application, after analysis, it can be known that when the device is running without failure (N _f (t) = 0), when the sub-module redundancy configuration method of the modular multi-level converter proposed in the embodiment of this application is adopted, the sub-module The capacitance reference voltage of the module is U _dc /(N+Nr), and when the conventional redundant configuration method is adopted, the capacitance reference voltage of the sub-module is U _dc /N. Therefore, the embodiment of the application proposes a modular multilevel converter After the redundant configuration method of the sub-module, the capacitor reference voltage of the sub-module is reduced, and the loss of the converter valve is reduced; in addition, the maximum number of output levels of the conventional redundant configuration method is N+1, and the embodiment of the application proposes a modular After the redundant configuration method of the sub-modules of the multi-level converter, the number of output levels is N+Nr+1, the number of levels increases, and the harmonic content of the output voltage decreases. Therefore, when a sub-module bypass failure occurs in the system, the embodiment of the present application proposes a sub-module redundancy configuration method of a modular multi-level converter that dynamically adjusts the value of the capacitor reference voltage _{according to the number of failed modules N f (t), so that} The capacitor voltage is increased accordingly, so that the output capability of the maximum voltage is not affected, and fault ride-through is realized.

In one embodiment, as shown in Figure 5, the capacitor reference voltage and the target output voltage of the upper bridge arm are used to determine the number of sub-modules invested in the upper bridge arm, and the capacitor reference voltage and the target output voltage of the lower bridge arm are used to determine After the number of sub-modules invested in the lower bridge arm, the following steps are also included:

Step S150: Calculate the number of redundant submodules to be put into use by using the number of submodules inputted in the upper bridge arm, the number of submodules inputted in the lower bridge arm, and the number of failed submodules.

In practical applications, the parameters are set according to the simulation model parameters in Table 1, and the simulation calculation is performed. The waveform diagrams of the capacitor voltage obtained by the simulation are shown in Figure 6a and Figure 6b. Referring to Fig. 6a, when the conventional redundant configuration method is adopted, the average value of the sub-module capacitor voltage is about 1.6kV; refer to Fig. 6b, the sub-module redundancy configuration method of the modular multi-level converter proposed by the embodiment of the application is The average value of the module capacitor voltage is about 1.45kV, and the sub-module capacitor voltage drops.

Table 1 Key parameters of the simulation model

Tab.1 Key parameters of the simulation model

In the embodiment of the present application, the aforementioned model parameters are used for simulation calculation, and the device loss histogram obtained by the simulation is shown in Figs. 7a to 7d. Refer to Figure 7a, when the conventional redundant configuration method is used, the sub-module (SM) has an average loss of 2094W under rectification conditions; refer to Figure 7b, when the conventional redundant configuration method is used, the sub-module (SM) is under inverter operating conditions. The average lower loss is 3068W; see Fig. 7c, when the sub-module redundancy configuration method of the modular multilevel converter proposed in the embodiment of this application, the average loss of the sub-module (SM) under the rectification condition is 2016W, see Fig. 7d, adopt The embodiment of this application proposes a sub-module redundancy configuration method of a modular multi-level converter. When the sub-module (SM) has an average loss of 2887 W under inverter conditions; it can be seen that the embodiment of the present application proposes a modular multi-level converter. After the redundant configuration method of the sub-module of the inverter, the loss of the sub-module is reduced, and the decrease is greater in the inverter working condition.

In the embodiment of the application, the above-mentioned model parameters are used for simulation calculation, and when the conventional redundant configuration method is adopted, the obtained sub-module fault ride-through waveform diagram is shown in FIG. 8. The embodiment of the application proposes a modular multilevel converter When the sub-module redundancy configuration method is adopted, the obtained sub-module fault ride-through waveform diagram is shown in Figure 9. When the system encounters a sub-module bypass fault, the fault is relatively light in the T1 interval, and the number of bypass faulted modules is small. At this time, the conventional redundant configuration method and the embodiment of the present application propose the sub-module of the modular multi-level converter All redundant configuration methods can achieve fault ride-through. When a serious sub-module bypass fault is encountered, a large number of sub-modules are bypassed in the T2 interval. After that, when the conventional redundant configuration method is adopted, the system has severe oscillations, and the system crashes with overvoltage and overcurrent; and When the sub-module redundancy configuration method of the modular multi-level converter proposed by the embodiment of the present application is adopted, the system retains the maximum voltage output capacity by increasing the capacitor voltage of the sub-module, and the system can continue to operate.

Example 2

The embodiment of the present application provides a sub-module redundancy configuration system of a modular multi-level converter, as shown in FIG. 10, including:

The number of faulty sub-modules determining module 1 is set to determine the number of faulty sub-modules in the modular multi-level converter; this module executes the method described in step S110 in the embodiment 1, which will not be repeated here.

The calculation module 2 is set to calculate the capacitance reference voltage of the sub-modules of the modular multi-level converter based on the number of the faulty sub-modules; this module executes the method described in step S120 in embodiment 1, which will not be repeated here .

The obtaining module 3 is configured to obtain the target output voltage of the upper bridge arm and the target output voltage of the lower bridge arm of the modular multilevel converter; this module executes the method described in step S130 in embodiment 1, which is not here. Go into details again.

The number of input sub-modules determining module 4 is set to use the capacitor reference voltage and the target output voltage of the upper bridge arm to determine the number of sub-modules input to the upper bridge arm, and use the capacitor reference voltage and the target output voltage of the lower bridge arm to determine the next The number of sub-modules invested by the bridge arm; this module executes the method described in step S140 in Embodiment 1, and will not be repeated here.

In one embodiment, the acquisition module 3 is configured to acquire the DC terminal voltage and the AC terminal voltage of the modular multilevel converter; the target output voltage of the upper bridge arm and the lower bridge arm are calculated by using the DC terminal voltage and the AC terminal voltage. The target output voltage.

In an embodiment, the obtaining module 3 is configured to calculate the target output voltage of the upper bridge arm and the target output voltage of the lower bridge arm by the following formula:

In formula (4), u _pa (t) represents the target output voltage of the upper bridge arm at the current time t, u _na (t) represents the target output voltage of the lower bridge arm at the current time t, U _dc represents the DC terminal voltage, u _sa ( t) represents the AC terminal voltage at the current time t.

In one embodiment, the calculation module 2 is set to obtain the number of regular sub-modules and the total number of redundant sub-modules that have been put into use. The total number is the number of all redundant sub-modules set in advance; the capacitor reference voltage is calculated by using the number of regular sub-modules, the total number of redundant sub-modules and the number of faulty sub-modules.

In an embodiment, the calculation module 2 is configured to calculate the sub-module capacitance reference voltage by using the following formula:

In formula (5), u _c * represents the capacitor reference voltage of the sub-module, U _dc represents the DC terminal voltage, N represents the number of regular sub-modules, N _r represents the total number of redundant sub-modules, and N _f (t) represents the current Number of faulty sub-modules at time t.

In an embodiment, the sub-module redundancy configuration system of the modular multi-level converter further includes: a redundancy sub-module number determining module, which is set to use the number of sub-modules invested by the upper bridge arm and the lower bridge The number of sub-modules put into use by the arm and the number of faulty sub-modules calculate the number of redundant sub-modules to be put into use.

In an embodiment, the number of input submodules determining module 4 is configured to calculate the number of input submodules of the upper bridge arm and the number of input submodules of the lower bridge arm through the following formula:

In formula (6), N _pa (t) represents the number of sub-modules input by the bridge arm at the current time t, N _na (t) represents the number of sub-modules input by the bridge arm at the current time t, and round[] represents rounding Function, u _pa (t) represents the target output voltage of the upper bridge arm at the current time t, u _na (t) represents the target output voltage of the lower bridge arm at the current time t, and u _c * represents the capacitor reference voltage of the sub-module.

The sub-module redundancy configuration system of the modular multilevel converter provided by this application calculates the capacitor reference voltage of the sub-module of the modular multilevel converter through the number of faulty sub-modules, and then uses the capacitor reference voltage and the upper The target output voltage of the bridge arm determines the number of sub-modules input in the upper bridge arm, and the capacitor reference voltage and the target output voltage of the lower bridge arm are used to determine the number of sub-modules input in the lower bridge arm, so that the capacitor reference voltage of the sub-module is reduced. , The loss of the converter valve is reduced; when the number of faulty modules is greater than the number of redundant modules, the system will also retain the maximum voltage output capacity by increasing the capacitor voltage, so that it will not produce violent oscillations, and it can still operate stably, which enhances Fault ride-through capability; and make full use of redundant modules, not only participate in voltage equalization, but also increase the number of system levels, thereby reducing the output voltage harmonic content, and improving the operating performance of the modular multi-level converter.

Example 3

An embodiment of the present application provides an electronic device, as shown in FIG. 11, including: at least one processor 401, such as a central processing unit (CPU), at least one communication interface 403, a memory 404, and at least one communication bus 402 . The communication bus 402 is configured to realize connection and communication between these components. The communication interface 403 may include a display (Display) and a keyboard (Keyboard). Optionally, the communication interface 403 may also include a standard wired interface and a wireless interface. The memory 404 may be a high-speed random access memory (Ramdom Access Memory, RAM), or a non-volatile memory (non-volatile memory), such as at least one disk memory. Optionally, the memory 404 may also be at least one storage device located far away from the aforementioned processor 401. The processor 401 may be configured to execute the sub-module redundancy configuration method of the modular multilevel converter of the first embodiment. The memory 404 is configured to store a set of program codes, and the processor 401 is configured to call the program codes stored in the memory 404 to execute the sub-module redundancy configuration method of the modular multilevel converter of the first embodiment.

The communication bus 402 may be a peripheral component interconnect standard (PCI) bus or an extended industry standard architecture (EISA) bus, etc. The communication bus 402 can be divided into an address bus, a data bus, a control bus, and so on. For ease of presentation, only one line is used to represent in FIG. 11, but it does not mean that there is only one bus or one type of bus.

The memory 404 may include a volatile memory (volatile memory), such as RAM; the memory may also include a non-volatile memory (non-volatile memory), such as flash memory (flash memory), hard disk drive (HDD) or Solid-State Drive (SSD); the storage 404 may also include a combination of the aforementioned types of storage.

The processor 401 may be a CPU, a network processor (Network Processor, NP), or a combination of CPU and NP.

The processor 401 may further include a hardware chip. The aforementioned hardware chip may be an application-specific integrated circuit (ASIC), a programmable logic device (Programmable Logic Device, PLD), or a combination thereof. The above-mentioned PLD may be a complex programmable logic device (Complex Programmable Logic Device, CPLD), a field programmable logic gate array (Field-Programmable Gate Array, FPGA), a general array logic (Generic Array Logic, GAL) or any combination thereof.

Optionally, the memory 404 is also configured to store program instructions. The processor 401 is configured to call program instructions to implement the sub-module redundancy configuration method of the modular multi-level converter in Embodiment 1 of the present application.

The embodiment of the present application also provides a computer-readable storage medium. The computer-readable storage medium stores computer-executable instructions. The computer-executable instructions can execute the redundant sub-modules of the modular multilevel converter of Embodiment 1. I configuration method. The storage medium may be a magnetic disk, an optical disc, a read-only memory (Read-Only Memory, ROM), RAM, Flash Memory, HDD, or SSD, etc.; the storage medium may also include a combination of the foregoing types of memories.

Claims

A redundant configuration method for sub-modules of a modular multilevel converter includes:

Determining the number of faulty sub-modules in the modular multilevel converter;

Calculating the capacitance reference voltage of the sub-module of the modular multilevel converter based on the number of the faulty sub-modules;

Obtaining the target output voltage of the upper bridge arm and the target output voltage of the lower bridge arm of the modular multilevel converter;

The capacitor reference voltage and the target output voltage of the upper bridge arm are used to determine the number of sub-modules invested in the upper bridge arm, and the capacitor reference voltage and the target output voltage of the lower bridge arm are used to determine the The number of sub-modules put into the lower bridge arm.
The method according to claim 1, wherein said obtaining the target output voltage of the upper bridge arm and the target output voltage of the lower bridge arm of the modular multilevel converter comprises:

Obtaining the DC terminal voltage and the AC terminal voltage of the modular multilevel converter;

The target output voltage of the upper bridge arm and the target output voltage of the lower bridge arm are calculated by using the DC terminal voltage and the AC terminal voltage.
The method according to claim 2, wherein the target output voltage of the upper bridge arm and the target output voltage of the lower bridge arm are calculated by the following formulas:

Where u pa (t) represents the target output voltage of the upper bridge arm at the current time t, u na (t) represents the target output voltage of the lower bridge arm at the current time t, U dc represents the DC terminal voltage, u sa (t) represents the AC terminal voltage at the current time t.
The method according to claim 2, wherein said calculating the capacitance reference voltage of the sub-modules of the modular multilevel converter based on the number of the faulty sub-modules comprises:

Obtain the number of regular sub-modules invested and the total number of redundant sub-modules, where the number of regular sub-modules is the minimum number of sub-modules required to maintain the normal operation of the system without failure, and the redundant sub-modules The total number is the number of all redundant sub-modules set in advance;

The capacitor reference voltage is calculated by using the number of regular submodules, the total number of redundant submodules, and the number of faulty submodules.
The method according to claim 4, wherein the capacitance reference voltage of the sub-module is calculated by the following formula:

Wherein, u c * represents the capacitance reference voltage of the sub-module, U dc represents the DC terminal voltage, N represents the number of the regular sub-modules, N r represents the total number of the redundant sub-modules, N f ( t) represents the number of faulty sub-modules at the current time t.
The method according to claim 4, after determining the number of sub-modules invested by the upper bridge arm by using the capacitor reference voltage and the target output voltage of the upper bridge arm, using the capacitor reference voltage and the lower bridge arm After the target output voltage of the bridge arm determines the number of sub-modules invested in the lower bridge arm, it also includes:

Calculate the number of redundant sub-modules to be put into use by using the number of sub-modules put in by the upper bridge arm, the number of sub-modules put in the lower bridge arm, and the number of failed sub-modules.
The method according to claim 1, wherein the number of sub-modules invested in the upper bridge arm and the number of sub-modules invested in the lower bridge arm are calculated by the following formula:

Among them, N pa (t) represents the number of sub-modules invested in the upper bridge arm at the current time t, N na (t) represents the number of sub-modules invested in the lower bridge arm at the current time t, round[] represents rounding Function, u pa (t) represents the target output voltage of the upper bridge arm at the current time t, u na (t) represents the target output voltage of the lower bridge arm at the current time t, and u c * represents the capacitance of the sub-module Reference voltage.
A redundant configuration system for sub-modules of modular multilevel converters, including:

A determining module for the number of faulty sub-modules is set to determine the number of faulty sub-modules in the modular multilevel converter;

A calculation module configured to calculate the capacitance reference voltage of the sub-module of the modular multilevel converter based on the number of the faulty sub-modules;

An obtaining module, configured to obtain the target output voltage of the upper bridge arm and the target output voltage of the lower bridge arm of the modular multilevel converter;

The input sub-module number determining module is configured to determine the number of input sub-modules of the upper bridge arm by using the capacitor reference voltage and the target output voltage of the upper bridge arm, and use the capacitor reference voltage and the lower The target output voltage of the bridge arm determines the number of sub-modules invested in the lower bridge arm.
A computer-readable storage medium storing computer instructions, which, when executed by a processor, implement the sub-module redundant configuration of the modular multilevel converter according to any one of claims 1-7 method.
An electronic device including:

A memory and a processor, the memory and the processor are in communication connection with each other, the memory is configured to store computer instructions, and the processor is configured to execute the computer instructions to execute as in claims 1-7 Any one of the sub-module redundant configuration methods of the modular multilevel converter.