MMC multi-tube open-circuit fault rapid diagnosis method and system

Abstract

The invention provides an MMC multi-tube open-circuit fault rapid diagnosis method and system, and relates to the technical field of open-circuit fault diagnosis, and the specific scheme comprises the steps: obtaining the operation data of a to-be-diagnosed MMC, including a capacitor voltage, an MMC DC side voltage, a power grid voltage, a power grid current, a power grid resistance, an MMC bridge arm inductance, a power grid inductance and a control signal; calculating expected values of common-mode and differential-mode voltages of the MMC bridge arm based on the operation data, subtracting the expected values from corresponding actual values to obtain a bridge arm voltage residual error, judging whether the bridge arm has a fault by using the bridge arm voltage residual error, and calculating the number of fault sub-modules in the fault bridge arm; calculating an expected value of the capacitive current of the sub-module in the fault bridge arm, subtracting the expected value from a corresponding actual value to obtain a capacitive current residual error of the sub-module, and positioning the fault sub-module by using the capacitive current residual error; according to the invention, fault diagnosis is carried out by using mismatching between an actual value and an expected value without increasing cost investment; the diagnosis speed and the accuracy are high.

Description

Technical Field

[0001] The invention belongs to the technical field of open circuit fault diagnosis, and in particular relates to a method and system for quickly diagnosing MMC multi-tube open circuit faults. Background Art

[0002] For a long time, energy resources and load demand have been distributed inversely. DC transmission is the key technology to solve this contradiction between energy supply and demand. The flexible direct current transmission system with Modulus Converter (MMC) as the core energy conversion equipment has obvious advantages in large-capacity and long-distance transmission, and has become a hot spot for the development of the energy industry; the sub-module (SM) is the basic component unit of the MMC, and the switching device is the core device of the SM, and its reliability directly determines the stability and economic benefits of the MMC operation; in the flexible direct current transmission system, the switching device (such as IGBT) works in a high-frequency switching state (large loss and high heat generation) for a long time, and the influence of complex working conditions such as high voltage, large current, limited heat dissipation, and mechanical vibration leads to a high failure rate of the device; according to the industrial power electronic converter equipment failure investigation report, the proportion of switch device and welding line detachment failure is as high as 34%, and the MMC converter station usually contains thousands of SMs (for example, the MMC of the Zhangbei Flexible Direct Current-Kangbao Converter Station contains a total of 1584 SMs), which makes the difficulty and cost of operation and inspection of the converter valve and its switching devices increase sharply.

[0003] Sudden failures of switching devices mainly include short-circuit failures and open-circuit failures. The protection hardware design for short-circuit failures has been very complete, but the processing mechanism for open-circuit failures is still immature. Open-circuit failures will cause the voltage of the faulty SM capacitor of the MMC to continue to rise. If the faulty SM is not isolated in time, the SM capacitor will break down and cause secondary failures, and even cause the MMC to crash. Therefore, rapid detection and positioning of open-circuit failures of switching devices is crucial to improving the reliability of MMC.

[0004] At present, the detection methods for open-circuit faults of MMC SM switching devices are divided into two categories: hardware methods and software methods. The hardware-based methods focus on adding additional sensors, such as adding bridge arm voltage sensors. Although the diagnosis speed is fast, it increases the SM cost and introduces new potential fault points, and the application scenarios are limited. The software-based methods focus on extracting fault characteristics from existing voltage and current quantities, such as SM capacitor voltage, bridge arm current, grid-connected current, etc. However, the open-circuit fault diagnosis method of detecting, locating and isolating faulty SM by setting SM capacitor voltage thresholds in existing projects is slow, which is not conducive to improving the reliability of MMC. Summary of the invention

[0005] In order to overcome the deficiencies of the above-mentioned prior art, the present invention provides a method and system for rapid diagnosis of MMC multi-tube open circuit faults, which utilizes the mismatch between actual values ​​and expected values ​​to perform fault diagnosis without increasing cost investment; the diagnosis speed is fast and the accuracy is high.

[0006] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions:

[0007] A first aspect of the present invention provides a method for rapid diagnosis of MMC multi-tube open circuit faults.

[0008] A method for quickly diagnosing a multi-tube open-circuit fault of an MMC, comprising:

[0009] Obtaining the operating data of the MMC to be diagnosed, including capacitor voltage, MMC DC side voltage, grid voltage, grid current, grid resistance, MMC bridge arm inductance, grid inductance and control signal;

[0010] Based on the operation data, the expected values ​​of the common-mode and differential-mode voltages of the MMC bridge arm are calculated, and the expected values ​​are subtracted from the corresponding actual values ​​to obtain the bridge arm voltage residual. The bridge arm voltage residual is used to determine whether the bridge arm is faulty and calculate the number of faulty submodules in the faulty bridge arm.

[0011] The expected value of the submodule capacitance current in the faulty bridge arm is calculated and subtracted from the corresponding actual value to obtain the capacitance current residual of the submodule. The capacitance current residual is used to locate the faulty submodule.

[0012] Furthermore, each phase of the MMC includes two bridge arms, an upper bridge arm and a lower bridge arm, each bridge arm includes a plurality of series-connected half-bridge sub-modules, and each half-bridge sub-module includes two switch devices.

[0013] Furthermore, the bridge arm voltage residual is composed of the bridge arm common mode and differential mode voltage residuals, and the calculation formula is:

[0014]

[0015]

[0016] in, They are the common mode and differential mode voltage differences of the j-phase bridge arm, are the true values ​​of the common-mode and differential-mode voltages of phase j respectively; are the expected values ​​of the common-mode and differential-mode voltages of phase j, are the capacitor voltages of the i-th submodule of the upper and lower bridge arms of phase j respectively; V dc is the DC side voltage of MMC; is the j-phase grid voltage; v on is the voltage difference between the DC side neutral point o and the grid neutral point n; are the j-phase grid current and the MMC internal current respectively; L arm , L g are the MMC bridge arm inductance and the grid inductance respectively; R g is the grid resistance; are the control signals of the upper tube of the i-th submodule of the upper and lower bridge arms of phase j respectively; N is the number of submodules of a single bridge arm of MMC; T s is the sampling time.

[0017] Furthermore, the determination of whether a bridge arm fault occurs is achieved by comparing the bridge arm voltage with a preset bridge arm voltage residual threshold.

[0018] Furthermore, the calculation of the number of faulty submodules in the faulty bridge arm is obtained by solving the relationship between the bridge arm voltage residual and the faulty bridge arm, the bridge arm current direction, and the number of faulty submodules.

[0019] Furthermore, the capacitor current residual is calculated as follows:

[0020]

[0021] in, is the residual capacitance current of the i-th submodule of the j-phase x-bridge arm, are the true value and expected value of the capacitor current of the i-th submodule of the j-phase x-bridge arm, respectively; is the capacitor voltage of the ith submodule of the j-phase x-bridge arm; is the j-phase x-bridge arm current; C SM is the submodule capacitance; is the control signal of the upper tube of the i-th submodule of the j-phase x bridge arm; T s is the sampling time.

[0022] Furthermore, the fault locating submodule determines whether a submodule fails by comparing the value with a preset capacitor current residual threshold.

[0023] A second aspect of the present invention provides a MMC multi-tube open circuit fault rapid diagnosis system.

[0024] A MMC multi-tube open circuit fault rapid diagnosis system, including an operation data acquisition module, a bridge arm fault judgment module and a submodule fault location module:

[0025] The operation data acquisition module is configured to: acquire the operation data of the MMC to be diagnosed, including capacitor voltage, MMC DC side voltage, grid voltage, grid current, grid resistance, MMC bridge arm inductance, grid inductance and control signal;

[0026] The bridge arm fault judgment module is configured to: calculate the expected values ​​of the common mode and differential mode voltages of the MMC bridge arm based on the operation data, and make a difference with the corresponding actual values ​​to obtain the bridge arm voltage residual, use the bridge arm voltage residual to judge whether the bridge arm fails, and calculate the number of faulty submodules in the faulty bridge arm;

[0027] The submodule fault location module is configured to: calculate the expected value of the submodule capacitor current in the faulty bridge arm, and subtract it from the corresponding actual value to obtain the capacitor current residual of the submodule, and use the capacitor current residual to locate the faulty submodule.

[0028] The third aspect of the present invention provides a computer-readable storage medium having a program stored thereon, which, when executed by a processor, implements the steps of a method for rapid diagnosis of MMC multi-tube open circuit faults as described in the first aspect of the present invention.

[0029] The fourth aspect of the present invention provides an electronic device, including a memory, a processor, and a program stored in the memory and executable on the processor. When the processor executes the program, the steps in the MMC multi-tube open circuit fault rapid diagnosis method as described in the first aspect of the present invention are implemented.

[0030] One or more of the above technical solutions have the following beneficial effects:

[0031] The present invention utilizes the mismatch between actual values ​​and expected values, calculates the bridge arm voltage and capacitor current residuals based on control signals, locates the faulty bridge arm through the bridge arm voltage residuals and calculates the number of faulty sub-modules SM on the bridge arm, locates the faulty SM through the capacitor current residuals, does not require the addition of additional hardware devices, does not require increased cost investment, has fast diagnosis speed and high accuracy, achieves rapid diagnosis of the entire MMC multi-tube open circuit fault, and provides guidance for subsequent fault tolerance and maintenance work.

[0032] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0034] Figure 1 This is the MMC topology diagram of the first embodiment.

[0035] Figure 2 This is a diagram showing the change in SM current path before and after the switching device fails in the first embodiment.

[0036] Figure 3This is a flow chart of the fault diagnosis algorithm of the first embodiment. DETAILED DESCRIPTION

[0037] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0038] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0039] Embodiment 1

[0040] In one embodiment of the present disclosure, a method for rapid diagnosis of MMC multi-tube open circuit faults is provided, comprising the following steps:

[0041] Step S1: Acquire the operating data of the MMC to be diagnosed, including capacitor voltage, MMC DC side voltage, grid voltage, grid current, grid resistance, MMC bridge arm inductance, grid inductance and control signal.

[0042] Furthermore, each phase of the MMC includes two bridge arms, an upper bridge arm and a lower bridge arm, each bridge arm includes a plurality of series-connected half-bridge sub-modules, and each half-bridge sub-module includes two switch devices.

[0043] Step S2: Based on the operation data, the expected values ​​of the common-mode and differential-mode voltages of the MMC bridge arm are calculated, and the expected values ​​are subtracted from the corresponding actual values ​​to obtain the bridge arm voltage residual. The bridge arm voltage residual is used to determine whether the bridge arm is faulty and calculate the number of faulty submodules in the faulty bridge arm.

[0044] Furthermore, the bridge arm voltage residual is composed of the bridge arm common mode and differential mode voltage residuals, and the calculation formula is:

[0045]

[0046] in, They are the common mode and differential mode voltage differences of the j-phase bridge arm, are the true values ​​of the common-mode and differential-mode voltages of phase j respectively; are the expected values ​​of the common-mode and differential-mode voltages of phase j, are the capacitor voltages of the i-th submodule of the upper and lower bridge arms of phase j respectively; V dc is the DC side voltage of MMC; is the j-phase grid voltage; v on is the voltage difference between the DC side neutral point o and the grid neutral point n; are the j-phase grid current and the MMC internal current respectively; L arm , L g are the MMC bridge arm inductance and the grid inductance respectively; R g is the grid resistance; are the control signals of the upper tube of the i-th submodule of the upper and lower bridge arms of phase j respectively; N is the number of submodules of a single bridge arm of MMC; T s is the sampling time.

[0047] Furthermore, the determination of whether a bridge arm fault occurs is achieved by comparing the bridge arm voltage with a preset bridge arm voltage residual threshold.

[0048] Furthermore, the calculation of the number of faulty submodules in the faulty bridge arm is obtained by solving the relationship between the bridge arm voltage residual and the faulty bridge arm, the bridge arm current direction, and the number of faulty submodules.

[0049] Step S3: Calculate the expected value of the submodule capacitance current in the faulty bridge arm, and subtract it from the corresponding actual value to obtain the capacitance current residual of the submodule, and use the capacitance current residual to locate the faulty submodule.

[0050] Furthermore, the capacitor current residual is calculated as follows:

[0051]

[0052] in, is the residual capacitance current of the i-th submodule of the j-phase x-bridge arm, are the true value and expected value of the capacitor current of the i-th submodule of the j-phase x-bridge arm, respectively; is the capacitor voltage of the ith submodule of the j-phase x-bridge arm; is the j-phase x-bridge arm current; C SM is the submodule capacitance; is the control signal of the upper tube of the i-th submodule of the j-phase x bridge arm; T s is the sampling time.

[0053] Furthermore, the fault locating submodule determines whether a submodule fails by comparing the value with a preset capacitor current residual threshold.

[0054] The following describes in detail the implementation process of a method for rapidly diagnosing multi-tube open-circuit faults in MMC in this embodiment from three major aspects: MMC topological structure, MMC discrete mathematical model, and a method for rapidly diagnosing open-circuit faults based on voltage and capacitance residuals.

[0055] 1.MMC topology

[0056] The topology of three-phase MMC for grid connection is as follows: Figure 1 As shown, each phase of the converter includes two bridge arms, an upper bridge arm and a lower bridge arm, and each bridge arm includes N series-connected half-bridge submodules SM and a bridge arm inductor L arm ; Each half-bridge SM contains two switching devices Two anti-parallel diodes and a capacitor C SM .

[0057] The SM output voltage is determined by the control signal, which has only two states: 0 means the switch is off, and 1 means the switch is on. i =1, V SM =V C ; When S i =0, V SM =0. In addition, the DC side voltage of MMC is V dc , the AC side passes through the filter resistor (R g )、Inductance(L g ) and then connected to a three-phase balanced AC grid with a grid voltage of

[0058] 2.MMC Discrete Mathematical Model

[0059] The discrete mathematical model of MMC can be expressed as:

[0060]

[0061] in, They are the MMC j-phase grid-connected current and the bridge arm internal current respectively; is the submodule capacitor voltage of the i-th submodule of the j-phase x-bridge arm; are the voltage of the bridge arm of phase j x; V dc is the DC side grid voltage; is the j-phase grid voltage; is the voltage difference between the DC side neutral point o and the grid neutral point n; R g , L eq =L arm / 2+L g are the grid resistance and equivalent inductance respectively; C SM is the submodule capacitance; is the control signal of the upper tube of the i-th submodule of the j-phase x bridge arm; T s is the sampling time.

[0062] 3. Rapid diagnosis method of multi-tube open circuit fault based on voltage and capacitance residual

[0063] 3.1 Open circuit fault analysis

[0064] like Figure 2 As shown in Figure 2, there are two types of open circuit faults that may occur in each SM, namely, upper tube fault and down tube failure Figure 2 (a) and (b) are the changes in the current path before and after the open-circuit fault of the upper and lower tubes of the SM, respectively. The blue color represents the current path before the fault, and the red color represents the current path after the fault. Table 1 shows the differences in the operating characteristics of the faulty SM under the two open-circuit faults.

[0065] Table 1 Operation characteristics of SM under different open circuit fault conditions

[0066]

[0067] It can be seen from Table 1 that in the two types of open circuit situations, the operating state, output voltage, and capacitor voltage of the faulty SM will change. Based on the above characteristics, this embodiment proposes a multi-tube open circuit fault rapid diagnosis method based on voltage and capacitance residuals. Figure 3 It is a flow chart of a method for rapid diagnosis of multi-tube open circuit faults.

[0068] 3.2 Determine whether the bridge arm is faulty

[0069] like Figure 3 As shown in the red part, the bridge arm voltage residual is used to determine whether the bridge arm is faulty.

[0070] is the actual voltage value at time k, is the expected value of voltage at time k, and the actual value and expected value of the bridge arm voltage are as follows:

[0071]

[0072] in, are the true values ​​of the common-mode and differential-mode voltages of phase j respectively; are the expected values ​​of the common-mode and differential-mode voltages of phase j, are the capacitor voltages of the i-th submodule of the upper and lower bridge arms of phase j respectively; V dc is the DC side voltage of MMC; is the j-phase grid voltage; v on is the voltage difference between the DC side neutral point o and the grid neutral point n; are the j-phase grid current and the MMC internal current respectively; L arm , L g are the MMC bridge arm inductance and the grid inductance respectively; R g is the grid resistance; are the control signals of the upper tube of the i-th submodule of the upper and lower bridge arms of phase j respectively; N is the number of submodules of a single bridge arm of MMC; T s is the sampling time.

[0073] The bridge arm voltage residuals are:

[0074]

[0075] in, They are the common-mode and differential-mode voltage differences of the j-phase bridge arm respectively.

[0076] In order to simplify the analysis, it is assumed that the voltage of each SM capacitor is completely balanced. In order to make the proposed method independent of the capacitor voltage and improve the applicability of the method, the bridge arm voltage residual can be further normalized as:

[0077]

[0078] in, are the common mode and differential mode voltage residuals of the j-phase bridge arm, V dc is the DC side voltage of MMC, and N is the number of submodules of a single bridge arm of MMC.

[0079] The bridge arm voltage residual is compared with the preset bridge arm voltage residual threshold ε th Compare the size to determine whether the bridge arm has failed. For example, when the faulty SM upper tube should conduct current, according to formula (10-11), the bridge arm voltage residuals are For example, when When , it is determined that the j-phase bridge arm is faulty.

[0080] 3.3 Calculate the number of faulty submodules in the faulty bridge arm

[0081] The relationship between the bridge arm voltage residual and the faulty bridge arm, bridge arm current direction, and the number of faulty sub-modules is shown in Table 2.

[0082] Table 2 Voltage residual characteristics under different open circuit fault conditions

[0083]

[0084] According to Table 2, when a bridge arm is detected to have a fault, the number of faulty submodules on the upper and lower bridge arms can be solved, specifically:

[0085] After obtaining the common-mode and differential-mode voltage residuals of the j-phase bridge arm Under the premise of , substitute the following formula in Table 2:

[0086]

[0087] in, are the number of faulty submodules in the upper bridge arm and lower bridge arm of phase j, are the j-phase grid current and internal current respectively, and sgn is the sign function.

[0088] 3.4 Locating the faulty submodule SM

[0089] like Figure 3 As shown in the yellow part, the capacitor current residual is used to locate the fault SM.

[0090] is the actual value of the capacitor current at time k, is the expected value of the capacitor current at time k, and the actual value and expected value of the capacitor current are as follows:

[0091]

[0092] in, are the true value and expected value of the i-th SM capacitor current of the j-phase x-bridge arm, respectively; is the voltage of the SM capacitor of the i-th bridge arm of phase j; is the j-phase x-bridge arm current; C SM is the submodule capacitance; is the control signal of the upper tube of the i-th submodule of the j-phase x bridge arm; T s is the sampling time.

[0093] The capacitor current residual is:

[0094]

[0095] in, is the residual current of the capacitor of the i-th submodule of the j-phase x-bridge arm.

[0096] In order to make the proposed method overcome the influence of load changes and improve the applicability of the method, the capacitor current residual can be normalized as:

[0097]

[0098] in, is the j-phase x-bridge arm current.

[0099] Capacitor current residual of submodule By comparing with the preset capacitor current residual threshold τ th By comparing the size of , we can determine whether the i-th submodule of the j-phase x-bridge arm has a fault. Taking the upper tube open circuit fault as an example, when the upper tube of the faulty SM should conduct current, according to formula (15), the residual of the capacitor current of the faulty SM is For example, when When , it is determined that the i-th SM of the j-phase x-bridge arm fails and should be isolated.

[0100] When the number of isolated SMs is equal to the total number of faulty submodules N f When they are equal, the fault SM isolation is completed and the fault diagnosis algorithm ends.

[0101] This embodiment proposes a fast and accurate diagnosis method for the open circuit fault of MMCSM switching device, which provides a new idea for the open circuit fault diagnosis of MMC switching device; it can be combined with the fault-tolerant control technology of MMC to further improve the reliability of the equipment; in addition, it is not only suitable for power device fault detection in power electronic equipment, but can also be extended to the field of relay protection in the power grid, using the residual between the predicted current or voltage and the actual current or voltage for fault detection as a trigger signal for the relay protection device.

[0102] Embodiment 2

[0103] In one embodiment of the present disclosure, a MMC multi-tube open circuit fault rapid diagnosis system is provided, including an operation data acquisition module, a bridge arm fault judgment module and a submodule fault location module:

[0104] The operation data acquisition module is configured to: acquire the operation data of the MMC to be diagnosed, including capacitor voltage, MMC DC side voltage, grid voltage, grid current, grid resistance, MMC bridge arm inductance, grid inductance and control signal;

[0105] The bridge arm fault judgment module is configured to: calculate the expected values ​​of the common mode and differential mode voltages of the MMC bridge arm based on the operation data, and make a difference with the corresponding actual values ​​to obtain the bridge arm voltage residual, use the bridge arm voltage residual to judge whether the bridge arm fails, and calculate the number of faulty submodules in the faulty bridge arm;

[0106] The submodule fault location module is configured to: calculate the expected value of the submodule capacitor current in the faulty bridge arm, and subtract it from the corresponding actual value to obtain the capacitor current residual of the submodule, and use the capacitor current residual to locate the faulty submodule.

[0107] Embodiment 3

[0108] The purpose of this embodiment is to provide a computer-readable storage medium.

[0109] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of a method for rapid diagnosis of MMC multi-tube open circuit faults as described in the first embodiment of the present disclosure.

[0110] Embodiment 4

[0111] The purpose of this embodiment is to provide an electronic device.

[0112] An electronic device includes a memory, a processor, and a program stored in the memory and executable on the processor. When the processor executes the program, the steps in a method for rapid diagnosis of MMC multi-tube open circuit faults as described in Embodiment 1 of the present disclosure are implemented.

[0113] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for rapid diagnosis of MMC multi-tube open circuit faults, characterized in that: include: Obtaining the operating data of the MMC to be diagnosed, including capacitor voltage, MMC DC side voltage, grid voltage, grid current, grid resistance, MMC bridge arm inductance, grid inductance and control signal; Based on the operation data, the expected values ​​of the common-mode and differential-mode voltages of the MMC bridge arm are calculated, and the expected values ​​are subtracted from the corresponding actual values ​​to obtain the bridge arm voltage residual. The bridge arm voltage residual is used to determine whether the bridge arm is faulty and calculate the number of faulty submodules in the faulty bridge arm. The expected value of the submodule capacitance current in the faulty bridge arm is calculated and subtracted from the corresponding actual value to obtain the capacitance current residual of the submodule. The capacitance current residual is used to locate the faulty submodule.

2. A MMC multi-tube open circuit fault rapid diagnosis method as claimed in claim 1, characterized in that: Each phase of the MMC comprises two bridge arms, an upper bridge arm and a lower bridge arm, each bridge arm comprises a plurality of series-connected half-bridge sub-modules, and each half-bridge sub-module comprises two switch devices.

3. A MMC multi-tube open circuit fault rapid diagnosis method as claimed in claim 1, characterized in that: The bridge arm voltage residual is composed of the bridge arm common mode and differential mode voltage residuals, and the calculation formula is: in, They are the common mode and differential mode voltage differences of the j-phase bridge arm, are the true values ​​of the common-mode and differential-mode voltages of phase j respectively; are the expected values ​​of the common-mode and differential-mode voltages of phase j, are the capacitor voltages of the i-th submodule of the upper and lower bridge arms of phase j respectively; is the DC side voltage of the MMC; is the voltage of the j-phase grid; is the voltage difference between the DC side neutral point o and the grid neutral point n; are the j-phase grid current and the MMC internal current respectively; and are the MMC bridge arm inductance and grid inductance respectively; and are the grid resistance; are the control signals of the upper tube of the i-th submodule of the upper and lower bridge arms of phase j respectively; N is the number of submodules of a single bridge arm of the MMC; is the sampling time.

4. A MMC multi-tube open circuit fault rapid diagnosis method as claimed in claim 1, characterized in that: The determination of whether a bridge arm fault occurs is achieved by comparing the bridge arm voltage with a preset bridge arm voltage residual threshold.

5. A MMC multi-tube open circuit fault rapid diagnosis method as claimed in claim 1, characterized in that: The calculation of the number of faulty submodules in the faulty bridge arm is obtained by solving the relationship between the bridge arm voltage residual and the faulty bridge arm, the bridge arm current direction, and the number of faulty submodules.

6. A MMC multi-tube open circuit fault rapid diagnosis method as claimed in claim 1, characterized in that: The capacitance current residual is calculated as follows: in, is the residual capacitance current of the i-th submodule of the j-phase x-bridge arm, are the true value and expected value of the capacitor current of the i-th submodule of the j-phase x-bridge arm, respectively; is the capacitor voltage of the ith submodule of the j-phase x-bridge arm; is the j-phase x-bridge arm current; C SM is the submodule capacitance; is the control signal of the upper tube of the i-th submodule of the j-phase x-bridge arm; is the sampling time.

7. A MMC multi-tube open circuit fault rapid diagnosis method as claimed in claim 1, characterized in that: The fault locating submodule determines whether a submodule fails by comparing the value with a preset capacitor current residual threshold.

8. A MMC multi-tube open circuit fault rapid diagnosis system, characterized in that: It includes operation data acquisition module, bridge arm fault judgment module and submodule fault location module: The operation data acquisition module is configured to: acquire the operation data of the MMC to be diagnosed, including capacitor voltage, MMC DC side voltage, grid voltage, grid current, grid resistance, MMC bridge arm inductance, grid inductance and control signal; The bridge arm fault judgment module is configured to: calculate the expected values ​​of the common mode and differential mode voltages of the MMC bridge arm based on the operation data, and make a difference with the corresponding actual values ​​to obtain the bridge arm voltage residual, use the bridge arm voltage residual to judge whether the bridge arm fails, and calculate the number of faulty submodules in the faulty bridge arm; The submodule fault location module is configured to: calculate the expected value of the submodule capacitor current in the faulty bridge arm, and subtract it from the corresponding actual value to obtain the capacitor current residual of the submodule, and use the capacitor current residual to locate the faulty submodule.

9. An electronic device, comprising: a memory for non-transitory storage of computer readable instructions; a processor for executing the computer-readable instructions; Wherein, when the computer-readable instructions are executed by the processor, the method according to any one of claims 1 to 7 is executed.

10. A storage medium, characterized in that: The computer-readable instructions are non-transitorily stored, wherein when the computer-readable instructions are executed by a computer, the method of any one of claims 1 to 7 is performed.

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