Trigger detection method and system for flexible direct current converter valve energy release branch action

Abstract

The invention relates to a trigger detection method and system for the action of an energy release branch of a flexible direct current converter valve, and belongs to the technical field of direct current power transmission. Comprising the following steps: carrying out the following trigger detection on an energy discharge branch of a sub-module in each bridge arm according to a set number sequence: when the capacitor voltage of the sub-module is greater than or equal to a capacitor voltage set value in an energy discharge branch trigger detection interval of the sub-module corresponding to the current number, applying a trigger pulse to the energy discharge branch, detecting whether the energy discharge branch has a fault or not, after the detection of the energy discharge branch is completed, adding 1 to a trigger detection number, and entering an energy discharge branch trigger detection interval of a sub-module corresponding to a next number after a set time; and when the trigger detection number is greater than the number corresponding to the maximum sub-module, ending the trigger detection. According to the method, the energy discharge branches of one bridge arm are triggered and detected one by one in sequence, and actions are triggered for the energy discharge branches of all sub-modules on the premise of not influencing the operation characteristics of the system.

Description

Technical Field

[0001] The invention relates to a trigger detection method and system for the action of a flexible DC converter valve energy discharge branch, belonging to the technical field of DC power transmission. Background Art

[0002] Flexible DC transmission technology can provide AC power support for passive systems. It is an ideal solution for large-scale new energy bases in deserts, Gobi, and wasteland areas in my country, as well as large-scale wind farms in the deep sea. However, when the AC power grid or DC transmission line at the receiving end fails, the power transmission capacity of this type of transmission system is severely limited, and the power response speed of the new energy station is slow, resulting in serious power surplus in the flexible DC converter valve at the sending end or both the sending and receiving ends. The power surplus will cause the flexible DC converter valve submodule to overvoltage quickly, which is very likely to trigger the overvoltage protection, resulting in the serious consequence of system shutdown. Therefore, AC and DC energy dissipation devices are often used in engineering to actively dissipate surplus power.

[0003] AC energy-consuming devices are usually installed on the AC side of the converter valve at the sending end of the system, occupying a large area. In addition, when the receiving-end AC system or the remote DC line fails, the sending end may be unable to respond in time due to slow fault perception due to transmission delay. Therefore, it is not applicable to offshore wind power and ultra-long-distance onshore new energy base flexible DC island transmission systems.

[0004] In current engineering applications, DC energy-consuming devices are usually constructed separately from flexible DC converter valves and arranged as an important device on the DC side of the receiving-end converter valve. Therefore, they have the disadvantages of large size, high cost and complex structure.

[0005] Therefore, some scholars have proposed a flexible DC converter valve with energy discharge function. An energy discharge branch consisting of a fully controlled power electronic switch and a resistor in series is integrated at both ends of the sub-module capacitor of the flexible DC converter valve. The sub-module voltage is autonomously adjusted downward as needed to avoid overvoltage lockout or damage, thereby making the processing of surplus power more direct and flexible, and the system structure is compact and economical.

[0006] However, for the flexible DC converter valve with energy discharge function, the energy discharge branches of all its submodules are always in an inactive state during normal operation. There is currently no relevant solution on how to automatically, efficiently, conveniently and reliably realize the trigger detection of the energy discharge branches of all submodules without affecting the system operation characteristics. Summary of the invention

[0007] The purpose of the present invention is to provide a trigger detection method and system for the action of the energy discharge branch of a flexible DC converter valve, so as to solve the problem of how to trigger the action of the energy discharge branches of all submodules of the flexible DC converter valve without affecting the system operation characteristics.

[0008] To achieve the above object, the solution of the present invention includes:

[0009] A trigger detection method for the action of a flexible DC converter valve energy discharge branch of the present invention comprises:

[0010] Triggering and detecting the energy discharge branches of the submodules in each bridge arm of the flexible DC converter valve with energy discharge function in a set numbering sequence;

[0011] The trigger detection includes: when the energy discharge branch of the submodule corresponding to the current number is in the trigger detection interval, and the capacitor voltage of the submodule is greater than or equal to the capacitor voltage setting value, a trigger pulse is applied to the energy discharge branch of the submodule, and the energy discharge branch of the submodule is detected to see if it is faulty. After the detection of the energy discharge branch of the submodule is completed, the trigger detection number is increased by 1, and the energy discharge branch trigger detection interval of the submodule corresponding to the next number is entered after the set time; when the trigger detection number is greater than the number corresponding to the largest submodule of the bridge arm, the trigger detection ends.

[0012] Furthermore, setting the numbering sequence refers to the numbering sequence of the submodules obtained by numbering the submodules in the bridge arm according to the electrical connection sequence of the submodules in the bridge arm, or the numbering sequence of the energy discharge branches obtained by numbering the energy discharge branches corresponding to the submodules in the bridge arm according to the electrical connection sequence of the submodules in the bridge arm.

[0013] Furthermore, the electrical connection sequence of the submodules in the bridge arm refers to from the DC side to the AC side of the bridge arm, or from the AC side to the DC side of the bridge arm.

[0014] Furthermore, the calculation formula of the capacitor voltage setting value is as follows:

[0015] u Cset =U sm0 (1+k*P / P0)

[0016] In the formula, u Cset is the capacitor voltage setting value, U sm0 is the rated operating voltage of the submodule, k∈[0,0.05], P is the current actual operating power of the submodule, and P0 is the rated active power of the submodule.

[0017] Furthermore, the width of the trigger pulse ranges from 2 to 10 control cycles.

[0018] Furthermore, the method for detecting whether the energy discharge branch of the submodule is faulty includes:

[0019] 1) After a trigger pulse with a width of T1 is applied to the energy discharge branch of the submodule for the first time, the initial value of the number of trigger faults of the energy discharge branch action of the submodule is set to 0;

[0020] 2) Detecting the resistance voltage of the energy discharge branch of the submodule;

[0021] 3) If the resistor voltage is continuously less than the resistor voltage setting value within T1, the number of fault triggering is increased by 1, and the process goes to step 4); otherwise, it is considered that the energy discharge branch of the submodule is in normal state, and the energy discharge branch of the submodule completes the trigger detection;

[0022] 4) If the number of consecutive trigger faults of the energy discharge branch of the submodule is less than the set number N, a trigger pulse with a width of T1 is applied again, and steps 2) and 3) are repeated; if the number of consecutive trigger faults of the energy discharge branch of the submodule is equal to N, the energy discharge branch of the submodule is considered to be in a fault state, and the energy discharge branch of the submodule completes the trigger detection.

[0023] Furthermore, the resistance voltage setting value is greater than or equal to 50 volts; and the value range of N is 1 to 3.

[0024] Furthermore, the setting time ranges from 0 to 20 control cycles.

[0025] Furthermore, all bridge arms of the flexible DC converter valve are triggered and detected simultaneously or in a set order.

[0026] Furthermore, after obtaining the detection result of the energy discharge branch of the submodule, the detection result is reported to the upper-layer monitoring system.

[0027] A trigger detection system for the action of an energy discharge branch of a flexible DC converter valve of the present invention comprises a processor, and the processor is used to execute a computer program to implement the steps of the trigger detection method for the action of an energy discharge branch of a flexible DC converter valve as described above.

[0028] Beneficial effects of the present invention:

[0029] The present invention is a pioneering invention, which provides a trigger detection method and system for the action of the energy discharge branch of a flexible DC converter valve. By performing a round of trigger detection on the energy discharge branches of the submodules in each bridge arm of the flexible DC converter valve with energy discharge function in a set numbering sequence, the energy discharge branches of the submodules in one bridge arm are triggered and detected in sequence. Under the premise of not affecting the system operation characteristics, the energy discharge branches of all submodules of the flexible DC converter valve with energy discharge function are triggered to act, so that the trigger detection of the action of the energy discharge branches of all submodules of the flexible DC converter valve with energy discharge function can be automatically, efficiently, conveniently and reliably realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a topological structure diagram of a flexible DC converter valve with energy discharge function;

[0031] Figure 2 It is a trigger detection flow chart for the action of the energy discharge branch of the flexible DC converter valve;

[0032] Figure 3 It is a flow chart for detecting whether the energy discharge branch of the submodule is faulty;

[0033] Figure 4 It is a simulation waveform diagram of a flexible DC converter valve obtained based on a trigger detection method for the action of an energy discharge branch of a flexible DC converter valve. DETAILED DESCRIPTION

[0034] In order to solve the problem in the background technology, the present invention performs a round of trigger detection on the energy discharge branch of the submodule in each bridge arm of the flexible DC converter valve with energy discharge function according to the set number sequence, so that the energy discharge branches of the submodules in one bridge arm are triggered one by one in sequence, and only one energy discharge branch of a submodule in one bridge arm is triggered. Under the premise of not affecting the system operation characteristics, the energy discharge branches of all submodules of the flexible DC converter valve with energy discharge function are triggered, so that the trigger detection of the energy discharge branch action of all submodules of the flexible DC converter valve with energy discharge function can be realized automatically, efficiently, conveniently and reliably.

[0035] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0036] An embodiment of a trigger detection method for a flexible DC converter valve energy discharge branch action:

[0037] A trigger detection method for the action of a flexible DC converter valve energy discharge branch comprises the following steps:

[0038] Triggering and detecting the energy discharge branches of the submodules in each bridge arm of the flexible DC converter valve with energy discharge function in a set numbering sequence;

[0039] The trigger detection includes: when the energy discharge branch of the submodule corresponding to the current number is in the trigger detection interval, and the capacitor voltage of the submodule is greater than or equal to the capacitor voltage setting value, a trigger pulse is applied to the energy discharge branch of the submodule, and the energy discharge branch of the submodule is detected to see if it is faulty. After the detection of the energy discharge branch of the submodule is completed, the trigger detection number is increased by 1, and the energy discharge branch trigger detection interval of the submodule corresponding to the next number is entered after the set time; when the trigger detection number is greater than the number corresponding to the largest submodule of the bridge arm, the trigger detection ends.

[0040] Among them, setting the numbering sequence refers to the numbering sequence of the submodules obtained by numbering the submodules in the bridge arm according to the electrical connection sequence of the submodules in the bridge arm, or the numbering sequence of the energy discharge branches obtained by numbering the energy discharge branches corresponding to the submodules in the bridge arm according to the electrical connection sequence of the submodules in the bridge arm.

[0041] The electrical connection sequence of the submodules in the bridge arm refers to from the DC side to the AC side of the bridge arm, or from the AC side to the DC side of the bridge arm.

[0042] Specifically, all bridge arms of the flexible DC converter valve are triggered and detected simultaneously or in a set order.

[0043] Specifically, after obtaining the detection result of the energy discharge branch of the submodule, the detection result is reported to the upper-layer monitoring system.

[0044] Specifically, a trigger detection method for the action of the energy discharge branch of the flexible DC converter valve is provided. Figure 2 As shown, the steps include:

[0045] S1: numbering the submodules in each bridge arm of the flexible DC converter valve with energy discharge function;

[0046] S2: In each bridge arm, trigger detection is performed on the energy discharge branches of each submodule in sequence according to the numbering order of the submodules;

[0047] S3: In the trigger detection interval of the energy discharge branch action of the current numbered submodule, when the capacitor voltage u C Greater than or equal to the capacitor voltage setting value u Cset ( Figure 2 is the voltage setting value u Cset ), a trigger pulse with a width of T1 is applied to the energy discharge branch of the submodule;

[0048] That is, when it is the turn of the energy discharge branch of the submodule with the current number to be triggered and detected, when the capacitor voltage of the submodule with the current number is greater than or equal to the capacitor voltage setting value, a trigger pulse with a width of T1 is applied to the energy discharge branch of the submodule;

[0049] S4: Detect whether the energy discharge branch of the submodule is faulty, and report the detection result to the upper-layer monitoring system;

[0050] S5: After completing the energy discharge branch state detection of the current numbered submodule, the trigger detection number is increased by 1, and after waiting for T2 time, the trigger detection interval of the energy discharge branch action of the next numbered submodule is entered;

[0051] S6: When the trigger detection number is greater than the maximum submodule number of the bridge arm, the trigger detection ends.

[0052] In S1, the submodules in each bridge arm are numbered, specifically, the submodules are numbered in sequence according to the electrical connection sequence of the submodules in the bridge arm.

[0053] The electrical connection sequence of the submodules in the bridge arm is from the DC side to the AC side of the bridge arm, or from the AC side to the DC side of the bridge arm.

[0054] That is, the submodules in each bridge arm may be numbered in sequence from the DC side to the AC side of the bridge arm in S1, or may be numbered in sequence from the AC side to the DC side of the bridge arm.

[0055] As another implementation, a trigger detection method for the action of the energy discharge branch of the flexible DC converter valve includes the following steps:

[0056] S1: numbering the energy discharge branches corresponding to the submodules in each bridge arm of the flexible DC converter valve with energy discharge function;

[0057] S2: triggering and detecting each energy discharge branch in turn in the order of the numbering of the energy discharge branches in each bridge arm;

[0058] S3: In the trigger detection interval of the energy discharge branch action of the current number, when the capacitor voltage u C Greater than or equal to the capacitor voltage setting value u Cset When , a trigger pulse with a width of T1 starts to be applied to the energy discharge branch;

[0059] That is, when it is the turn of the currently numbered energy discharge branch to be triggered and detected, when the capacitor voltage of the submodule to which the currently numbered energy discharge branch belongs is greater than or equal to the capacitor voltage setting value, a trigger pulse with a width of T1 is applied to the energy discharge branch;

[0060] S4: Detect whether the energy discharge branch is faulty and report the detection result to the upper monitoring system;

[0061] S5: After completing the state detection of the energy discharge branch of the current number, the trigger detection number is increased by 1, and after waiting for T2 time, the trigger detection interval of the action of the energy discharge branch of the next number is entered;

[0062] S6: When the trigger detection number is greater than the maximum submodule number of the bridge arm, the trigger detection ends.

[0063] In S1, the energy discharge branches corresponding to the submodules in each bridge arm are numbered, specifically, they are numbered in sequence according to the electrical connection sequence of the submodules to which the energy discharge branches in the bridge arm belong.

[0064] The electrical connection sequence of the submodules belonging to the energy discharge branch in the bridge arm is from the DC side to the AC side of the bridge arm, or from the AC side to the DC side of the bridge arm.

[0065] That is, the energy discharge branches corresponding to the sub-modules in each bridge arm in S1 may be numbered sequentially from the DC side to the AC side of the bridge arm, or may be numbered sequentially from the AC side to the DC side of the bridge arm.

[0066] The present invention can automatically, efficiently, conveniently and reliably realize the state detection of the discharge branches of all submodules of the flexible DC converter valve with energy discharge function without affecting the normal operation characteristics of the system.

[0067] Among them, the calculation formula of the capacitor voltage setting value in S3 is as follows:

[0068] u Cset =U sm0 (1+k*P / P0)

[0069] In the formula, u Cset is the capacitor voltage setting value, U sm0 is the rated operating voltage of the submodule, k is a constant, k∈[0,0.05], P is the current actual operating power of the submodule, and P0 is the rated active power of the submodule.

[0070] Among them, T1 of S3 is determined as small as possible under the premise of satisfying the state detection of the submodule energy discharge branch, and it is recommended to take 2 to 10 control cycles. That is, the value range of the trigger pulse width T1 is 2 to 10 control cycles.

[0071] Among them, Figure 3 As shown, the detection method for detecting whether the energy discharge branch of the submodule is faulty in S4 specifically includes:

[0072] 1) After a trigger pulse with a width of T1 is applied to the energy discharge branch of the submodule for the first time, the initial value of the trigger fault number of the energy discharge branch action of the submodule is set to 0;

[0073] 2) Detect the resistance voltage u of the energy discharge branch of the submodule R ;

[0074] 3) If u R The voltage is continuously less than the resistance voltage setting value u during T1 period. Rset , then the number of trigger faults of the energy discharge branch action of the submodule is increased by 1, and the process goes to step 4); otherwise, it is determined that the energy discharge branch state of the submodule is normal, and the energy discharge branch trigger detection of the submodule ends;

[0075] 4) If the number of consecutive trigger faults of the energy discharge branch of the submodule is less than the set number N, a trigger pulse with a width of T1 is applied again, and steps 2) and 3) are repeated; if the number of consecutive trigger faults of the energy discharge branch of the submodule is equal to N, the energy discharge branch of the submodule is judged to be faulty, and the energy discharge branch trigger detection of the submodule is terminated.

[0076] Among them, u in step 3) Rset ≥50V(volts).

[0077] In step 4), it is recommended that N be 1 to 3.

[0078] Among them, S5 as the setting time T2 is set according to the actual operation requirements, and it is recommended to take 0 to 20 control cycles; when T2 is set to 0, it is a continuous trigger detection of the action of the sub-module energy discharge branch in each bridge arm of the flexible DC converter valve with energy discharge function.

[0079] The topological structure of the flexible DC converter valve with energy discharge function of the present invention is as follows: Figure 1 As shown, the flexible DC converter valve includes 6 bridge arms, each bridge arm is composed of several sub-modules SM connected in series, and the sub-modules can all be half-bridge topology, all full-bridge topology or other sub-module topology, or a mixed series structure of half-bridge, full-bridge, or other topology sub-modules. The capacitors of each sub-module are connected in parallel with an energy discharge branch composed of a fully controlled power electronic switch and a resistor in series, which can actively discharge energy when the capacitor voltage is too high, thereby reducing the capacitor voltage and ensuring the safety of the sub-module.

[0080] For example, the rated capacity of the flexible DC converter valve with energy discharge function is 2000MW (megawatt), the rated voltage on the DC side is ±500kV (kilovolts), the rated voltage on the AC side is 520kV, the number of single bridge arm sub-modules is 454, the rated working voltage of the sub-module is 2203V, the sub-module capacitance is 9mF (millifarad), and the energy discharge branch resistance is 2Ω (ohm).

[0081] The present invention is a flow chart of a trigger detection method for the energy discharge branch action of a flexible DC converter valve with energy discharge function, as shown in FIG. Figure 2 As shown, the following steps are included:

[0082] 1. Number the submodules in each bridge arm of the flexible DC converter valve with energy discharge function.

[0083] The submodules in the bridge arm are numbered in sequence according to the electrical connection sequence. The first numbering method is to number them from the DC side to the AC side of the bridge arm, and the second numbering method is to number them from the AC side to the DC side of the bridge arm.

[0084] In this embodiment, the submodules in each bridge arm are numbered 1 to 454 according to the electrical connection sequence from the DC side to the AC side of the bridge arm.

[0085] 2. In each bridge arm, the energy discharge branch actions of each submodule are triggered and detected in sequence according to the numbering order.

[0086] In this embodiment, the energy discharge branch actions of the submodules in each bridge arm are triggered and detected in sequence from 1 to 454.

[0087] 3. In the energy discharge branch trigger detection interval of the current numbered submodule, when the capacitor voltage u C Greater than or equal to the voltage setting value u Cset When , a trigger pulse with a width of T1 starts to be applied to the energy discharge branch of the submodule.

[0088] Among them, u Cset The calculation formula is as follows:

[0089] u Cset =U sm0 (1+k*P / P0)

[0090] In the formula, u Cset is the capacitor voltage setting value, U sm0 is the rated operating voltage of the submodule, k is a constant, k∈[0,0.05], P is the current actual operating power of the submodule, and P0 is the rated active power of the submodule.

[0091] In this embodiment, U sm0=2203V, P0 = 2000MW, when the system is running at full power, therefore P = 2000MW, take k = 0.05, and calculate u Cset =U sm0 (1+k*P / P0)≈2313V.

[0092] Wherein, T1 is determined based on the principle of being as small as possible under the premise of satisfying the state detection of the submodule energy discharge branch, and it is recommended to take 2 to 10 control cycles. In this embodiment, the control cycle is 50 μs, and T1=100 μs (microseconds).

[0093] 4. Check whether the energy discharge branch of the submodule is faulty and report the detection result to the upper-level monitoring system.

[0094] Among them, the specific detection method of whether the submodule energy discharge branch is faulty is as follows: Figure 3 As shown, the following steps are included:

[0095] (1) After the trigger pulse is applied for the first time, the initial value of the number of trigger faults of the energy discharge branch of the submodule is set to 0;

[0096] (2) Detect the resistance voltage u of the energy discharge branch of the submodule R ;

[0097] (3)If u R The voltage is continuously less than the set value u during T1 period. Rset , the number of times the submodule energy discharge branch triggers a fault is increased by 1, and the process goes to step (4); otherwise, the energy discharge branch is judged to be normal, and the submodule energy discharge branch trigger detection process ends;

[0098] (4) If the number of consecutive trigger faults of the submodule energy discharge branch is less than N, a trigger pulse with a width of T1 is applied again, and steps (2) and (3) are repeated; if the number of consecutive trigger faults of the submodule energy discharge branch is equal to N, the submodule energy discharge branch is judged to be faulty, and the submodule energy discharge branch trigger detection process ends.

[0099] Among them, u Rset ≥50V; In this embodiment, take u Rset =1000V.

[0100] It is recommended that N is 1 to 3; in this embodiment, N is 1.

[0101] 5. After completing the energy discharge branch state detection of the current numbered submodule, the trigger detection number is increased by 1, and after waiting for T2 time, it enters the trigger detection interval of the next numbered submodule.

[0102] Among them, T2 is set according to the actual operation requirements, and it is recommended to take 0 to 20 control cycles. When T2 is set to 0, it is continuous trigger detection. In this embodiment, T2=0 is set, that is, the continuous trigger detection mode is adopted.

[0103] Among them, the trigger detection process of the 6 bridge arms can be carried out simultaneously or in sequence.

[0104] In this embodiment, the trigger detection processes of the six bridge arms are performed simultaneously.

[0105] 6. When the trigger detection number is greater than the maximum submodule number, the trigger detection process ends.

[0106] In this embodiment, the number of single bridge arm submodules is 454. When the trigger detection numbers of the six bridge arms are all equal to 455, the trigger detection process of the energy discharge branch action of the flexible DC converter valve with energy discharge function is completed.

[0107] The simulation waveform of the flexible DC converter valve obtained by the trigger detection method for the energy discharge branch action of the flexible DC converter valve with energy discharge function provided by the present invention is as follows: Figure 4 As shown in the figure, the system is set to operate normally at full power in the simulation, and the trigger detection process starts at 2s (seconds). The waveforms of the columns from top to bottom in the figure are the DC port voltage ( Figure 4 The waveform of the 6 bridge arm currents, the average voltage of the 6 bridge arm submodules ( Figure 4 The waveform of the submodule voltage) and the DC side inflow current ( Figure 4 The waveform of the trigger detection number of the energy discharge branch of the 6 bridge arm submodules and the maximum current of the 6 bridge arm energy discharge branch ( Figure 4 It can be seen from the simulation waveform that based on the trigger detection method for the energy discharge branch action of the flexible DC converter valve, the system automatically and quickly completes the entire trigger detection process within 320ms (milliseconds) without affecting the system operation characteristics.

[0108] An embodiment of a trigger detection system for a flexible DC converter valve energy discharge branch action:

[0109] A trigger detection system for the action of a flexible DC converter valve energy discharge branch includes a processor, and the processor is used to execute a computer program to implement the steps of a trigger detection method for the action of a flexible DC converter valve energy discharge branch. Among them, a trigger detection method for the action of a flexible DC converter valve energy discharge branch has been described in detail in an embodiment of a trigger detection method for the action of a flexible DC converter valve energy discharge branch, and will not be repeated here.

Claims

1. A trigger detection method for the action of the energy discharge branch of a flexible DC converter valve, characterized in that: include: Triggering and detecting the energy discharge branches of the submodules in each bridge arm of the flexible DC converter valve with energy discharge function in a set numbering sequence; The trigger detection includes: when the energy discharge branch of the submodule corresponding to the current number is in the trigger detection interval, and the capacitor voltage of the submodule is greater than or equal to the capacitor voltage setting value, applying a trigger pulse to the energy discharge branch of the submodule, and detecting whether the energy discharge branch of the submodule is faulty, after the detection of the energy discharge branch of the submodule is completed, the trigger detection number is increased by 1, and after the set time, the energy discharge branch trigger detection interval of the submodule corresponding to the next number is entered; When the trigger detection number is greater than the number corresponding to the largest submodule of the bridge arm, the trigger detection ends.

2. The trigger detection method for the action of the energy discharge branch of the flexible DC converter valve according to claim 1 is characterized in that: The set numbering sequence refers to the numbering sequence of the submodules obtained by numbering the submodules in the bridge arm according to the electrical connection sequence of the submodules in the bridge arm, or the numbering sequence of the energy discharge branches obtained by numbering the energy discharge branches corresponding to the submodules in the bridge arm according to the electrical connection sequence of the submodules in the bridge arm.

3. The trigger detection method for the action of the energy discharge branch of the flexible DC converter valve according to claim 2 is characterized in that: The electrical connection sequence of the submodules in the bridge arm refers to from the DC side to the AC side of the bridge arm, or from the AC side to the DC side of the bridge arm.

4. The trigger detection method for the action of the energy discharge branch of the flexible DC converter valve according to claim 1, characterized in that: The calculation formula of the capacitor voltage setting value is as follows: in Cset =U sm0 (1+k*P / P0) In the formula, u Cset is the capacitor voltage setting value, U sm0 is the rated operating voltage of the submodule, k∈[0,0.05], P is the current actual operating power of the submodule, and P0 is the rated active power of the submodule.

5. The trigger detection method for the action of the energy discharge branch of the flexible DC converter valve according to claim 1, characterized in that: The width of the trigger pulse ranges from 2 to 10 control cycles.

6. The trigger detection method for the action of the energy discharge branch of the flexible DC converter valve according to claim 1, characterized in that: The method for detecting whether the energy discharge branch of the submodule is faulty includes: 1) After the trigger pulse with a width of T1 is applied to the energy discharge branch of the submodule for the first time, the initial value of the number of trigger faults of the energy discharge branch action of the submodule is set to 0; 2) Detecting the resistance voltage of the energy discharge branch of the submodule; 3) If the resistor voltage is continuously less than the resistor voltage setting value within the T1 time, the number of triggered faults is increased by 1, and the process proceeds to step 4); otherwise, it is considered that the energy discharge branch of the submodule is in a normal state, and the energy discharge branch of the submodule completes the trigger detection; 4) If the number of consecutive trigger faults of the energy discharge branch of the submodule is less than the set number N, a trigger pulse with a width of T1 is applied again, and steps 2) and 3) are repeated; if the number of consecutive trigger faults of the energy discharge branch of the submodule is equal to the N, the energy discharge branch of the submodule is considered to be in a fault state, and the energy discharge branch of the submodule completes the trigger detection.

7. The trigger detection method for the action of the energy discharge branch of the flexible DC converter valve according to claim 6 is characterized in that: The resistance voltage setting value is greater than or equal to 50 volts; the value range of N is 1 to 3.

8. The trigger detection method for the action of the energy discharge branch of the flexible DC converter valve according to claim 1, characterized in that: The setting time has a value range of 0 to 20 control cycles.

9. The trigger detection method for the action of the energy discharge branch of the flexible DC converter valve according to claim 1, characterized in that: The trigger detection is performed on all bridge arms of the flexible DC converter valve simultaneously or in a set order.

10. A trigger detection system for the action of a flexible DC converter valve energy discharge branch, comprising a processor, characterized in that: The processor is used to execute a computer program to implement the steps of the trigger detection method for the action of the energy discharge branch of the flexible DC converter valve as described in any one of claims 1 to 9.

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