A hybrid MMC fault clearing control method and device with low full-bridge ratio

Abstract

This invention proposes a hybrid MMC fault clearing control method and apparatus with a low full-bridge ratio. The invention includes: when a DC fault is detected, the DC controller of the sending-end converter switches to fault mode, generates a fault DC internal potential through proportional control, and applies negative limiting to cut off the fault current; the AC controller switches to fault mode, adjusts the energy storage reference value of the full-bridge submodule, and generates an AC frequency deviation; the grid-side converter of the wind turbine sets the AC power reference value to zero, generates a wind turbine frequency deviation based on the power deviation, and updates the voltage phase; after the fault current returns to zero, each controller switches back to normal mode to restore power transmission. This method can quickly cut off the fault current, stabilize wind turbine operation, and ensure system fault ride-through and reliable recovery.

Description

Technical Field

[0001] This invention relates to the field of control technology, and in particular to a hybrid MMC fault clearing control method and apparatus with a low full-bridge ratio. Background Technology

[0002] Hybrid modular multilevel converters, as core equipment in new energy islanded DC transmission systems, are widely used in long-distance overhead power transmission projects. With the development of flexible DC technology, a topology system with self-clearing capability for DC faults has been constructed through the coordinated operation of full-bridge and half-bridge sub-modules. Specifically, this technical solution covers the entire process from fault detection to negative voltage injection, including key aspects such as converter valve lockout, energy dissipation, and current suppression, effectively solving the problems of slow tripping of traditional AC circuit breakers and high cost of DC circuit breakers.

[0003] However, in practical applications, existing hybrid full-bridge and half-bridge topologies typically employ a high proportion of full-bridge submodules to ensure reliable fault clearing, without fully exploring the control potential of low-proportion full-bridge modules under capacitor voltage rise mechanisms. This design leads to a significant increase in converter valve construction costs, a substantial rise in operating losses, and the occupation of a large amount of valve hall space. Due to the lack of optimized control strategies for low full-bridge ratios, the system struggles to achieve the optimal balance between economy and technology while ensuring rapid fault current interruption, severely hindering the promotion efficiency of large-scale renewable energy DC transmission projects. Summary of the Invention

[0004] The present invention aims to at least partially solve one of the technical problems in the related art.

[0005] Therefore, the first objective of this invention is to propose a hybrid MMC fault clearing control method with a low full-bridge ratio.

[0006] Another object of the present invention is to provide a hybrid MMC fault clearing control device with a low full-bridge ratio.

[0007] The third objective of this invention is to provide a computer device.

[0008] A fourth objective of this invention is to provide a non-transitory computer-readable storage medium.

[0009] To achieve the above objectives, a first aspect of the present invention proposes a hybrid MMC fault clearing control method with a low full-bridge ratio, comprising:

[0010] S1, when a DC fault is detected, the DC controller of the sending-end converter switches to fault mode, compares the measured value of DC current with zero value and generates a fault DC internal potential through proportional control, and applies a negative limit based on the full-bridge submodule ratio and boost factor to the fault DC internal potential to cut off the fault current. S2, when a DC fault is detected, the AC controller of the sending-end converter switches to fault mode, adjusts the energy storage reference value of the full-bridge submodule from the rated energy storage value to a preset multiple of the rated energy storage value, and generates an AC frequency deviation based on the deviation between the actual energy storage value of the full-bridge submodule and the adjusted energy storage reference value. S3, when the grid-side converter of the wind turbine detects a DC fault, it forces the AC power reference value to zero, and generates the wind turbine frequency deviation based on the deviation between the zeroed AC power reference value and the actual AC power value, thereby updating the wind turbine voltage phase. S4, after confirming that the DC fault current has been controlled to zero, switches the control strategies of the AC controller and DC controller of the sending-end converter and the grid-side converter of the wind turbine from the fault mode back to the normal operation mode in order to restore system power transmission.

[0011] In one embodiment of the present invention, S1 includes: The DC current measurement value is obtained and the difference between it and zero is used to obtain the current deviation. The current deviation is then input into a proportional controller to calculate the preliminary fault DC internal potential. The initial fault DC internal potential is limited between the DC voltage rating and the negative limiting value; The output fault DC internal potential, after being limited, is used to control the sending-end converter to block the fault current.

[0012] In one embodiment of the present invention, limiting the initial fault DC internal potential between the DC voltage rating and the negative limiting value includes: The ratio of the number of full-bridge submodules in each bridge arm to the total number of all submodules is collected in real time as the full-bridge submodule ratio. ; The ratio of the actual voltage to the rated voltage of the full-bridge submodule is calculated in real time and used as the boost factor of the full-bridge submodule. ; Based on the full-bridge submodule ratio and the boost coefficient of the full-bridge submodule Execute formula The dynamic negative limiting threshold is obtained through calculation; The initial fault DC internal potential is clamped between the dynamic negative limiting threshold and the rated DC voltage using a hard limiting circuit. The final fault DC internal potential is generated within the defined interval. .

[0013] In one embodiment of the present invention, S2 includes: When a DC fault signal is detected, the energy storage reference value of the full-bridge submodule is changed from the rated energy storage value. Switch to ,in This is a preset multiple of the rated energy storage. Collect actual values ​​of energy storage in the full-bridge submodule And calculate with the The difference is used to obtain the energy storage deviation. The energy storage deviation is input as a proportional coefficient. The proportional controller calculates the frequency deviation under fault modes. ; The frequency deviation With frequency rating Add them together to get the actual value of the frequency. And the voltage phase is generated by time integration. .

[0014] In one embodiment of the present invention, S3 includes: When a DC fault detection signal is received, the AC power reference value of the wind turbine grid-side converter is forcibly set to zero. Obtain the actual AC power value of the grid-side converter of the wind turbine and calculate the power deviation by measuring the difference between the zero value and the actual AC power value. The power deviation is input into the proportional controller to calculate the fan frequency deviation. The fan frequency is obtained by adding the fan frequency deviation to the rated frequency and updating the fan voltage phase by integrating over time.

[0015] In one embodiment of the present invention, the power deviation input proportional coefficient is: The proportional controller calculates the fan frequency deviation. include: Read the preset scaling factor And execute the formula The frequency deviation of the fan under fault conditions was calculated. ; The calculated fan frequency deviation With rated frequency The frequency of the fan is obtained by performing cumulative calculation. ; For the frequency of the wind turbine Perform integration operations Generating the fan voltage phase for dq decoupling control and pulse width modulation .

[0016] In one embodiment of the present invention, S4 includes: Real-time monitoring of the DC current measurement value of the sending-end converter and determination of whether it remains at zero value to confirm that the DC fault has been cleared; After confirming that the DC fault has been cleared, the energy storage reference value of the full-bridge submodule of the AC controller of the sending-end converter will be adjusted from... Restored to rated energy storage value The current reference value generation logic of the DC controller is restored to PI control based on the total energy storage deviation of the capacitor; During the fault preparation and recovery phase, the AC power reference value of the wind turbine grid-side converter is switched from the forced zero value back to the normal reference value generated by the maximum power point tracking control in order to restore system power transmission.

[0017] To achieve the above objectives, a second aspect of the present invention provides a hybrid MMC fault clearing control device with a low full-bridge ratio, comprising: The DC fault current limiting control module is used to switch the DC controller of the sending-end converter to fault mode when a DC fault is detected. It compares the measured value of DC current with zero value and generates a fault DC internal potential through proportional control. It also applies a negative limit based on the full-bridge submodule ratio and boost factor to the fault DC internal potential to cut off the fault current. The AC-side fault energy storage adjustment module is used to switch the AC controller of the sending-end converter to fault mode when a DC fault is detected, adjust the energy storage reference value of the full-bridge submodule from the rated energy storage value to a preset multiple of the rated energy storage value, and generate the AC frequency deviation based on the deviation between the actual energy storage value of the full-bridge submodule and the adjusted energy storage reference value. The wind turbine fault power suppression module is used to force the AC power reference value to zero when the wind turbine grid-side converter detects a DC fault, and generate the wind turbine frequency deviation based on the deviation between the zeroed AC power reference value and the actual AC power value, thereby updating the wind turbine voltage phase. The system fault recovery control module is used to switch the control strategies of the AC controller and DC controller of the sending-end converter and the grid-side converter of the wind turbine back from the fault mode to the normal operation mode after confirming that the DC fault current has been controlled to zero, so as to restore the system power transmission.

[0018] The present invention discloses a hybrid MMC fault clearing control method and apparatus with a low full-bridge ratio, which can significantly reduce the configuration ratio of full-bridge submodules in the hybrid MMC while ensuring rapid clearing of DC faults, thereby effectively reducing the cost of converter valves, floor space and operating losses.

[0019] To achieve the above objectives, a third aspect of this application provides a computer device comprising a processor and a memory; wherein the processor runs a program corresponding to the executable program code stored in the memory, for implementing a hybrid MMC fault clearing control method with a low full-bridge ratio as described in the first aspect embodiment.

[0020] To achieve the above objectives, a fourth aspect of this application provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements a hybrid MMC fault clearing control method with a low full-bridge ratio as described in the first aspect embodiment.

[0021] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0022] Figure 1 This is a flowchart of a hybrid MMC fault clearing control method with a low full-bridge ratio according to an embodiment of the present invention; Figure 2 This is an architecture diagram of a low-proportion full-bridge hybrid MMC fault clearing control method according to an embodiment of the present invention; Figure 3 This is a structural diagram of a hybrid MMC fault clearing control device with a low full-bridge ratio according to an embodiment of the present invention; Figure 4 It is a computer device according to an embodiment of the present invention. Detailed Implementation

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0024] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0025] The following description, with reference to the accompanying drawings, describes a hybrid MMC fault clearing control method and apparatus with a low full-bridge ratio according to an embodiment of the present invention.

[0026] Figure 1 This is a flowchart of a hybrid MMC fault clearing control method with a low full-bridge ratio according to an embodiment of the present invention, such as... Figure 1 As shown, it includes: S1, when a DC fault is detected, the DC controller of the sending-end converter switches to fault mode, compares the measured value of DC current with zero value and generates a fault DC internal potential through proportional control, and applies a negative limit based on the full-bridge submodule ratio and boost factor to the fault DC internal potential to cut off the fault current. S2, when a DC fault is detected, the AC controller of the sending-end converter switches to fault mode, adjusts the energy storage reference value of the full-bridge submodule from the rated energy storage value to a preset multiple of the rated energy storage value, and generates an AC frequency deviation based on the deviation between the actual energy storage value of the full-bridge submodule and the adjusted energy storage reference value. S3, when the grid-side converter of the wind turbine detects a DC fault, it forces the AC power reference value to zero, and generates the wind turbine frequency deviation based on the deviation between the zeroed AC power reference value and the actual AC power value, thereby updating the wind turbine voltage phase. S4, after confirming that the DC fault current has been controlled to zero, switches the control strategies of the AC controller and DC controller of the sending-end converter and the grid-side converter of the wind turbine from the fault mode back to the normal operation mode in order to restore system power transmission.

[0027] This invention proposes a hybrid MMC fault clearing control method with a low proportion of full-bridge components, the control strategy of which is as follows: Figure 2 As shown, it mainly consists of three parts: the send-end MMC (wind farm-side MMC, WFMMC) controller, the wind turbine-side converter controller, and the wind turbine grid-side converter controller. The receiver-end MMC (grid-side MMC, GSMMC) controller is consistent with conventional control, that is, it maintains a constant DC voltage during normal operation, and outputs a negative DC voltage to control the DC current to zero during a fault, thus clearing the fault. Among them: WFMMC controllers are available in both AC and DC versions. During normal operation, the outer loop of the DC controller stores the rated total energy of the MMC capacitors. W MMCN Subtract total energy storage W MMC The DC current reference value is obtained through an outer-loop proportional-integral (PI) controller. i dc :

[0028] Reference value of DC current i dc and measured values i dc The difference is calculated, and the deviation of the DC internal potential is obtained through the inner loop proportional-integral controller:

[0029] This deviation is related to the DC voltage measurement value. u dc By subtracting the values, we obtain the DC internal potential. edc :

[0030] Actual energy storage value of the full-bridge submodule in normal mode of the AC controller W MMCF Subtract the rated value W MMCFN And through a proportional controller (proportional coefficient is...) k pc ), to obtain the frequency deviation Δ ω MMC :

[0031] Frequency deviation Δ ω MMC and frequency ratings ω N Add them together to get the actual value of the frequency. ω MMC :

[0032] The actual value of the frequency ω MMC Integrating yields the voltage phase. θ MMC :

[0033] voltage amplitude E MMC Then it is directly equal to the rated voltage. U MMCN The AC internal potential is obtained through a double closed-loop voltage and current circuit. e a , e b , e c Upon detecting a DC fault, the DC controller switches from normal mode to fault mode. In fault mode, the DC current measurement is subtracted from 0, and this difference is processed by the proportional controller (proportional coefficient is...). k pdc ), to obtain the DC internal potential under fault mode:

[0034] The internal potential is limited by a hard limit, the maximum limit of which is the rated DC voltage. U dcN The minimum amplitude limit is –(2) η F k F – 1)U dcN ,in η F This indicates the proportion of the full-bridge submodule in each bridge arm to all submodules. k F This represents the boost factor of the full-bridge submodule, which is equal to the ratio of the actual voltage of the full-bridge submodule to its rated voltage.

[0035] After a DC fault was detected AC controller It also switches from normal mode to fault mode. In fault mode, the energy storage reference value of the full-bridge submodule changes from the rated energy storage value. W MMCFN Switch to rated energy storage k up times (i.e.) k up W MMCFN The frequency deviation under fault mode becomes:

[0036] Correspondingly, the actual frequency is:

[0037] Therefore, the phase satisfies:

[0038] The voltage amplitude remains unchanged. E MMC = U MMCN Then, an AC internal potential is generated by dual closed-loop control. e a , e b , e c .

[0039] After the MMC detects that the fault has been cleared (i.e., the DC current has been controlled to 0), it switches the AC controller's fault mode back to normal mode. When preparing to recover from a fault, it switches the DC controller's fault mode back to normal mode.

[0040] Furthermore, the wind turbine grid-side converter controller is divided into a voltage controller and a phase controller. For the phase controller, during normal operation, it is based on the current wind turbine speed... Ω m And with Maximum Power Point Tracking (MPPT) control, an AC power reference value is obtained. P ac Then, the AC power reference valueP ac and actual value P ac The difference is calculated and processed by a proportional controller (proportional coefficient is...). k pp ), to obtain the fan frequency deviation Δ ω g :

[0041] frequency deviation Δ ω g With rated frequency ω N Making and obtaining the frequency of the fan ω g :

[0042] Finally, the fan frequency ω g Integrating to obtain the wind turbine voltage phase θ g :

[0043] After detecting a fault, the fan will adjust the AC power reference value. P ac Setting it to 0 will set the fan frequency to 0. ω g It becomes:

[0044] Finally, the fan frequency ω g Integrating to obtain the wind turbine voltage phase θ g :

[0045] When preparing to restore from a fault, the AC power reference value will be used. P ac Reverting to normal mode is generated by MPPT.

[0046] In voltage controllers, the reactive power reference value of the converter Q g Subtract the actual value Q g After passing through the proportional controller (proportional coefficient is...) k pq After that, the AC rated voltage of the converter is... UgN By performing the above steps, the reference value of the AC voltage amplitude of the grid-side converter of the wind turbine can be obtained. U g Therefore, we have:

[0047] AC voltage amplitude reference value U g and phase θ g After further decoupling control (dq), reference voltages for the d-axis and q-axis are obtained respectively. u gd and u gq Finally, the phase generated by the phase controller... θ g The three-phase AC modulation wave of the converter is obtained and controlled by pulse width modulation (PWM).

[0048] Furthermore, the wind turbine-side converter, specifically the outer loop of the q-axis controller, uses DC voltage control, meaning the actual DC voltage value... u dcW Subtract the rated value u dcWN Afterwards, through proportional-integral control, the reference value of the q-axis inner loop current is obtained. i sq :

[0049] d-axis inner loop current reference value i sd The value is always 0. Using the inner current loop control, the d-axis and q-axis reference voltages of the machine-side converter are obtained. u sd , u sq Then, it is transformed back to the abc coordinate system for modulation.

[0050] By making reasonable use of the capacitor voltage boosting mechanism, the hybrid MMC in this embodiment of the invention can significantly reduce the proportion of full-bridge sub-modules while maintaining fault clearing speed, thus achieving an optimal balance between fault clearing capability and system cost.

[0051] To achieve the above embodiments, such as Figure 3 As shown, this embodiment also provides a hybrid MMC fault clearing control device 10 with a low full-bridge ratio, comprising: The DC fault current limiting control module is used to switch the DC controller of the sending-end converter to fault mode when a DC fault is detected. It compares the measured value of DC current with zero value and generates a fault DC internal potential through proportional control. It also applies a negative limit based on the full-bridge submodule ratio and boost factor to the fault DC internal potential to cut off the fault current. The AC-side fault energy storage adjustment module is used to switch the AC controller of the sending-end converter to fault mode when a DC fault is detected, adjust the energy storage reference value of the full-bridge submodule from the rated energy storage value to a preset multiple of the rated energy storage value, and generate the AC frequency deviation based on the deviation between the actual energy storage value of the full-bridge submodule and the adjusted energy storage reference value. The wind turbine fault power suppression module is used to force the AC power reference value to zero when the wind turbine grid-side converter detects a DC fault, and generate the wind turbine frequency deviation based on the deviation between the zeroed AC power reference value and the actual AC power value, thereby updating the wind turbine voltage phase. The system fault recovery control module is used to switch the control strategies of the AC controller and DC controller of the sending-end converter and the grid-side converter of the wind turbine back from the fault mode to the normal operation mode after confirming that the DC fault current has been controlled to zero, so as to restore the system power transmission.

[0052] The present invention discloses a hybrid MMC fault clearing control device with a low full-bridge ratio, which can significantly reduce the configuration ratio of full-bridge submodules in the hybrid MMC while ensuring rapid clearing of DC faults, thereby effectively reducing the cost of converter valves, floor space and operating losses.

[0053] To implement the methods of the above embodiments, the present invention also provides a computer device, such as... Figure 4 As shown, the computer device 600 includes a memory 601 and a processor 602; wherein, the processor 602 reads the executable program code stored in the memory 601 to run a program corresponding to the executable program code, so as to implement the various steps of the hybrid MMC fault clearing control method with low full-bridge ratio described above.

[0054] To implement the above embodiments, this application also proposes a non-transitory computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements a hybrid MMC fault clearing control method with a low full-bridge ratio as described in the foregoing embodiments.

[0055] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0056] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

Claims

1. A hybrid MMC fault clearing control method with low full-bridge ratio, characterized in that, include: S1, when a DC fault is detected, the DC controller of the sending-end converter switches to fault mode, compares the measured value of DC current with zero value and generates a fault DC internal potential through proportional control, and applies a negative limit based on the full-bridge submodule ratio and boost factor to the fault DC internal potential to cut off the fault current. S2, when a DC fault is detected, the AC controller of the sending-end converter switches to fault mode, adjusts the energy storage reference value of the full-bridge submodule from the rated energy storage value to a preset multiple of the rated energy storage value, and generates an AC frequency deviation based on the deviation between the actual energy storage value of the full-bridge submodule and the adjusted energy storage reference value. S3, when the grid-side converter of the wind turbine detects a DC fault, it forces the AC power reference value to zero, and generates the wind turbine frequency deviation based on the deviation between the zeroed AC power reference value and the actual AC power value, thereby updating the wind turbine voltage phase. S4, after confirming that the DC fault current has been controlled to zero, switches the control strategies of the AC controller and DC controller of the sending-end converter and the grid-side converter of the wind turbine from the fault mode back to the normal operation mode in order to restore system power transmission.

2. The method as described in claim 1, characterized in that, S1 includes: The DC current measurement value is obtained and the difference between it and zero is used to obtain the current deviation. The current deviation is then input into a proportional controller to calculate the preliminary fault DC internal potential. The initial fault DC internal potential is limited between the DC voltage rating and the negative limiting value; The output fault DC internal potential, after being limited, is used to control the sending-end converter to block the fault current.

3. The method as described in claim 2, characterized in that, Limiting the initial fault DC internal potential between the rated DC voltage and the negative limiting value includes: The ratio of the number of full-bridge submodules in each bridge arm to the total number of all submodules is collected in real time as the full-bridge submodule ratio. ; The ratio of the actual voltage to the rated voltage of the full-bridge submodule is calculated in real time and used as the boost factor of the full-bridge submodule. ; Based on the full-bridge submodule ratio and the boost coefficient of the full-bridge submodule Execute formula The dynamic negative limiting threshold is obtained through calculation; The initial fault DC internal potential is clamped between the dynamic negative limiting threshold and the rated DC voltage using a hard limiting circuit. The final fault DC internal potential is generated within the defined interval. .

4. The method as described in claim 1, characterized in that, S2 includes: When a DC fault signal is detected, the energy storage reference value of the full-bridge submodule is changed from the rated energy storage value. Switch to ,in This is a preset multiple of the rated energy storage. Collect the actual value of energy storage of the full-bridge submodule And calculate with the The difference is used to obtain the energy storage deviation. The energy storage deviation is input as a proportional coefficient. The proportional controller calculates the frequency deviation under fault modes. ; The frequency deviation With frequency rating Add them together to get the actual value of the frequency. And the voltage phase is generated by time integration. .

5. The method as described in claim 1, characterized in that, The S3 includes: When a DC fault detection signal is received, the AC power reference value of the wind turbine grid-side converter is forcibly set to zero. Obtain the actual AC power value of the grid-side converter of the wind turbine and calculate the power deviation by measuring the difference between the zero value and the actual AC power value. The power deviation is input into the proportional controller to calculate the fan frequency deviation. The fan frequency is obtained by adding the fan frequency deviation to the rated frequency and updating the fan voltage phase by integrating over time.

6. The method as described in claim 5, characterized in that, The power deviation is input as a proportional coefficient. The proportional controller calculates the fan frequency deviation. include: Read the preset scaling factor And execute the formula The fan frequency deviation under fault conditions was calculated. ; The calculated fan frequency deviation With rated frequency The frequency of the fan is obtained by performing cumulative calculation. ; For the frequency of the wind turbine Perform integration operations Generating the fan voltage phase for dq decoupling control and pulse width modulation .

7. The method as described in claim 1, characterized in that, The S4 includes: Real-time monitoring of the DC current measurement value of the sending-end converter and determination of whether it remains at zero value to confirm that the DC fault has been cleared; After confirming that the DC fault has been cleared, the energy storage reference value of the full-bridge submodule of the AC controller of the sending-end converter will be adjusted from... Restored to rated energy storage value The current reference value generation logic of the DC controller is restored to PI control based on the total energy storage deviation of the capacitor; During the fault preparation and recovery phase, the AC power reference value of the wind turbine grid-side converter is switched from the forced zero value back to the normal reference value generated by the maximum power point tracking control in order to restore system power transmission.

8. A hybrid MMC fault clearing control device with low full-bridge ratio, characterized in that, include: The DC fault current limiting control module is used to switch the DC controller of the sending-end converter to fault mode when a DC fault is detected. It compares the measured value of DC current with zero value and generates a fault DC internal potential through proportional control. It also applies a negative limit based on the full-bridge submodule ratio and boost factor to the fault DC internal potential to cut off the fault current. The AC-side fault energy storage adjustment module is used to switch the AC controller of the sending-end converter to fault mode when a DC fault is detected, adjust the energy storage reference value of the full-bridge submodule from the rated energy storage value to a preset multiple of the rated energy storage value, and generate the AC frequency deviation based on the deviation between the actual energy storage value of the full-bridge submodule and the adjusted energy storage reference value. The wind turbine fault power suppression module is used to force the AC power reference value to zero when the wind turbine grid-side converter detects a DC fault, and generate the wind turbine frequency deviation based on the deviation between the zeroed AC power reference value and the actual AC power value, thereby updating the wind turbine voltage phase. The system fault recovery control module is used to switch the control strategies of the AC controller and DC controller of the sending-end converter and the grid-side converter of the wind turbine back from the fault mode to the normal operation mode after confirming that the DC fault current has been controlled to zero, so as to restore the system power transmission.

9. A computer device, characterized in that, Including processor and memory; The processor reads executable program code stored in the memory to run a program corresponding to the executable program code, so as to implement a hybrid MMC fault clearing control method with low full-bridge ratio as described in any one of claims 1-7.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements a hybrid MMC fault clearing control method with a low full-bridge ratio as described in any one of claims 1-7.

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