Three-level converter locking method

Abstract

The invention relates to the field of flexible converters, in particular to a three-level converter locking method, a storage medium and electronic equipment, the three-level converter comprises a plurality of three-level bridge arms, and each three-level bridge arm comprises a plurality of switch tube groups formed by connecting at least two switch tubes in series; wherein the two ends of the switching tube are connected in parallel with the voltage-sharing buffer circuit, and the voltage-sharing buffer circuit comprises a capacitor element; the switch tube group is divided into an outer tube group, an inner tube group and a clamping tube group, the outer tube group comprises a first outer tube group and a second outer tube group, the inner tube group comprises a first inner tube group and a second inner tube group, and the clamping tube group comprises a first clamping tube group and a second clamping tube group; the locking method comprises the following steps: locking the outer tube group in a conducting state; all the inner pipe groups and the clamping pipe groups in the locking state are conducted; and all the inner pipe groups and the clamping pipe groups are locked. According to the invention, before all the inner tube groups and the clamping tube groups are locked, all the inner tube groups and the clamping tube groups in the locked state are conducted in a pilot manner, so that the problem of locking overvoltage of the power switch device can be avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible converters, and in particular, to a three-level converter locking method, a storage medium, and an electronic device. Background Art

[0002] The statements in this part merely provide background technical information related to the present invention and do not necessarily constitute prior art.

[0003] A flexible converter is the core equipment of a flexible distribution network, which can realize AC-DC power conversion, and then realize power mutual assistance, reliability improvement, new energy carrying capacity improvement, etc. of the distribution network.

[0004] With the improvement of the power level of the flexible power distribution system, it is required to further improve the power level of the flexible converter. A feasible method is to construct a three-level converter by directly connecting devices in series, so as to improve the single-machine power capacity of the converter. In order to solve the problem of dynamic uneven voltage sharing during the turn-off process of directly connected devices in series, a buffer circuit is usually connected in parallel to the power switch devices. Since the parallel buffer circuit usually contains capacitive elements, the voltage of the power switch devices cannot change suddenly. If the traditional method of directly locking the inner tubes after locking the outer tubes is adopted, device overvoltage will occur. The overvoltage phenomenon during the locking of power devices will cause the power devices to withstand twice the blocking voltage, resulting in overvoltage failure of the power devices. In view of the above defects, the present invention has made improvements. Summary of the Invention

[0005] In order to overcome the deficiencies of the background art, the present invention provides a three-level converter locking method, a storage medium, and an electronic device. The locking method improves the traditional three-level converter locking method. Before locking all the inner tube groups and the clamping tube groups, all the inner tube groups and the clamping tube groups in the locked state are first turned on, which can effectively avoid the problem of overvoltage during the locking of power switch devices.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] In a first aspect, a three-level converter locking method is provided.

[0008] Wherein, the three-level converter includes a plurality of three-level bridge arms, each three-level bridge arm includes a plurality of switch tube groups formed by at least two switch tubes connected in series, and a voltage-sharing buffer circuit is connected in parallel at both ends of the switch tubes. The voltage-sharing buffer circuit includes capacitive elements. The switch tube groups are divided into outer tube groups, inner tube groups, and clamping tube groups. The outer tube groups include a first outer tube group and a second outer tube group. The inner tube groups include a first inner tube group and a second inner tube group. The clamping tube groups include a first clamping tube group and a second clamping tube group.

[0009] The locking method includes:

[0010] The outer tube group in the conducting state is blocked;

[0011] All the inner tube groups and the clamping tube groups in the blocked state are conducted;

[0012] All the inner tube groups and the clamping tube groups are blocked.

[0013] Furthermore,

[0014] After blocking the outer tube group in the conducting state, all the inner tube groups and the clamping tube groups in the blocked state are conducted after a first dead time;

[0015] After conducting all the inner tube groups and the clamping tube groups in the blocked state, all the inner tube groups and the clamping tube groups are blocked after a second dead time.

[0016] Furthermore,

[0017] Both the first dead time and the second dead time are 10 to 20 microseconds.

[0018] Furthermore,

[0019] When blocking one of the switch tube groups, all the series-connected switch tubes in the switch tube group should be blocked simultaneously;

[0020] When conducting one of the switch tube groups, all the series-connected switch tubes in the switch tube group should be conducted simultaneously.

[0021] Furthermore,

[0022] When conducting all the inner tube groups and the clamping tube groups in the blocked state, all the blocked switch tubes in the inner tube groups and the clamping tube groups should be conducted simultaneously;

[0023] When blocking all the inner tube groups and the clamping tube groups, all the switch tubes in the inner tube groups and the clamping tube groups should be blocked simultaneously.

[0024] Furthermore,

[0025] The three-level converter is an ANPC type three-level converter;

[0026] The blocking method is used for blocking in the zero-level output state where the outer tube group of the ANPC type three-level converter is conducting.

[0027] Furthermore,

[0028] The voltage equalizing buffer circuit adopts an RC circuit or an RCD circuit.

[0029] Furthermore,

[0030] The series-connected switching tubes in the switching tube group are IGCTs or IGBTs.

[0031] Based on the same inventive concept, the present invention also provides a computer-readable storage medium storing one or more programs, which when executed can implement the three-level converter locking method as described above.

[0032] Based on the same inventive concept, the present invention also provides an electronic device, including a processor, a communication interface, the computer-readable storage medium as described above, and a communication bus; wherein, the processor, the communication interface, and the computer-readable storage medium communicate with each other through the communication bus; the processor is configured to execute the programs stored in the computer-readable storage medium.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows: The traditional locking method of the three-level converter is improved. Before locking all the inner tube groups and the clamping tube groups, all the inner tube groups and the clamping tube groups in the locked state are turned on first, which can effectively avoid the overvoltage problem of the power switch device during locking.

[0034] Other features and advantages of the present invention will be described in the following specification, and, in part, will be obvious from the specification, or will be understood by implementing the present invention. The objectives and other advantages of the present invention can be realized and obtained by the structures pointed out in the specification, the claims, and the drawings.

[0035] The present invention will be further described below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0037] Figure 1 It is a schematic diagram of a half-bridge structure of a three-level converter based on device series connection according to an embodiment of the present invention;

[0038] Figure 2 It is a schematic flowchart of a three-level converter locking method according to an embodiment of the present invention;

[0039] Figures 3(a) to 3(d) It is a schematic diagram of the commutation process of a three-level converter using the traditional locking method;

[0040] Figures 4(a) to 4(f) It is a schematic diagram of the commutation process of a three-level converter using the optimized locking method according to an embodiment of the present invention;

[0041] Figure 5 It is a terminal voltage test diagram of a three-level converter adopting a traditional locking method;

[0042] Figure 6 It is a terminal voltage test diagram of a three-level converter adopting the optimized locking method of the embodiment of the present invention;

[0043] Figure 7 It is a schematic diagram of an electronic device according to an embodiment of the present invention. Specific embodiments

[0044] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0045] The locking method of the embodiment of the present invention is applicable to a three-level converter based on device series connection. The three-level converter includes a plurality of three-level bridge arms, and each three-level bridge arm includes a plurality of switch tube groups formed by at least two switch tubes connected in series. A voltage-sharing buffer circuit is connected in parallel at both ends of the series-connected switch tubes. The voltage-sharing buffer circuit includes a capacitive element. The switch tube groups are divided into an outer tube group, an inner tube group and a clamping tube group. The outer tube group includes a first outer tube group and a second outer tube group. The inner tube group includes a first inner tube group and a second inner tube group. The clamping tube group includes a first clamping tube group and a second clamping tube group.

[0046] Figure 1 Shown is a schematic diagram of a half-bridge structure of a three-level converter based on device series connection. In the figure, P represents the highest potential point of the upper DC bus, N represents the lowest potential point of the lower DC bus, 0 represents the midpoint potential point, C1 and C2 are the capacitors of the upper DC bus and the lower DC bus respectively, and T1 to T6 are switch tube groups formed by at least two switch tubes connected in series (that is, the plurality of switch tube groups included in each three-level bridge arm mentioned above). Figure 1 Taking the switch tube group T1 as an example only to show the series structure of a plurality of switch tubes (in this embodiment, T1_1 to T1_ n ), and the switch tube groups T2 to T6 refer to the switch tube group T1. D1 to D6 respectively represent the anti-parallel diode groups of T1 to T6. Figure 1Taking D1 as an example only for demonstration, D1_1 to D1_n respectively represent the antiparallel diodes of T1_1 to T1_n, and the antiparallel diode groups D2 to D6 refer to D1. In this embodiment, the DC bus voltage of the three-level topology is composed of the upper bus voltage and the lower bus voltage, and the upper and lower bus capacitors respectively support the upper and lower bus voltages; the antiparallel diodes are used to provide a freewheeling path for the load current.

[0047] Among them, T1 and T4 are called the outer switch tube groups of the bridge arm (i.e., the aforementioned first outer tube group and the second outer tube group), T2 and T3 are called the inner switch tube groups of the bridge arm (i.e., the aforementioned first inner tube group and the second inner tube group), and T5 and T6 are called the clamping switch tube groups (i.e., the aforementioned first clamping tube group and the second clamping tube group).

[0048] The switch tubes in the switch tube groups represented by T1 to T6 can be high-power power semiconductor devices such as IGCT or IGBT. In specific implementation, the models of the power semiconductor devices adopted by T1 to T6 do not have to be all the same, but generally require full-controlled power semiconductor devices with the same voltage and current capacity.

[0049] Figure 1 The switch tube groups (T1 to T6) shown in the main circuit are all composed of multiple switch tubes (i.e., power switch devices) connected in series. At the same time, a voltage-sharing buffer circuit is connected in parallel at both ends of the series switch tubes to achieve voltage sharing of the series devices. Taking the switch tube group T1 as an example, a schematic diagram of the direct series structure of the devices is given in the figure. The number of series devices is greater than or equal to two. The voltage-sharing buffer circuit shown in the figure is an RC circuit. Here, the RC circuit is only taken as an example, and it can also be other types, such as other voltage-sharing circuits such as RCD. In specific implementation, within the same switch tube group, the voltage-sharing buffer circuits connected in parallel at both ends of the series switch tubes must be the same; for different switch groups (such as different outer tube groups, inner tube groups or clamping tube groups), the voltage-sharing buffer circuits adopted within the switch group can be the same or different. The aforementioned three-level converter can be further referred to the existing technology and will not be elaborated here.

[0050] For the above three-level converter based on device series connection, the embodiment of the present invention provides a three-level converter locking method, as Figure 2 shown, the locking method includes:

[0051] S1. Lock the outer tube group in the conducting state;

[0052] S2. Turn on all the inner tube groups and the clamping tube groups in the locked state;

[0053] S3. Lock all the inner tube groups and the clamping tube groups.

[0054] The above technical solution improves the traditional locking method of the three-level converter (that is, first lock the outer tube group, and then directly lock the inner tube group). Before locking all the inner tube groups and the clamping tube groups, first turn on all the inner tube groups and the clamping tube groups in the locked state, which can effectively avoid the problem of overvoltage during the locking of the power switch devices.

[0055] The locking method of the above three-level converter will be described below.

[0056] As a preferred technical solution, the three-level converter is an ANPC type three-level converter; the locking method is used for locking the ANPC type three-level converter in the zero-level output state where the outer tube group is conducting. The ANPC type three-level converter includes six level states: P, 0U1, OU2, 0L1, OL2, and N; the locking method provided in the embodiment of the present invention is used for locking in the level state 0U2 or 0L2 of the ANPC type three-level converter, which can effectively avoid the problem of overvoltage during the locking of the power switch devices. It should be noted that for the ANPC type three-level converter, there is no outer tube conduction state in the level states OU1 and 0L1, and the locking operation can be directly performed in these two states without overvoltage problems; there is an outer tube conduction state in the level states P and N, and the outer tube needs to be turned off first and then the inner tube and the clamping tube are turned off, and no overvoltage problem will occur with this operation; the locking methods for the four states of P, OU1, OL1, and N all belong to the prior art.

[0057] As a preferred technical solution, after locking the outer tube group in the conducting state, all the inner tube groups and the clamping tube groups in the locked state are turned on after a first dead time; after all the inner tube groups and the clamping tube groups in the locked state are turned on, all the inner tube groups and the clamping tube groups are locked after a second dead time. In this embodiment, the first dead time is set to ensure that the outer tube group is fully locked before the clamping tube group is turned on to prevent the occurrence of through-current in the bridge arm; the second dead time is set to make the potential of the inner tube group and the clamping tube group drop to zero after conduction, so as to ensure that the back-end voltage starts to rise from zero potential after the subsequent locking of the inner tube group, and further ensure that the switching tube of the inner tube group does not have overvoltage.

[0058] In some embodiments, both the first dead time and the second dead time are 10 to 20 microseconds. In this embodiment, both the first dead time and the second dead time are preferably 10 to 20 microseconds. When the dead time adopts a value within this range, on the one hand, it ensures the full execution of the transient transition process after the power device performs the turn-on or turn-off operation, and on the other hand, it reduces the occupation of the switching period and reduces the output voltage distortion rate. Specifically, the first dead time and the second dead time do not necessarily have to be the same. The setting of this time is usually determined according to the performance parameters of the specific model of the power device used and the working characteristics of the converter equipment, and it needs to be designed for specific product cases.

[0059] As a preferred technical solution, when blocking one of the switch tube groups, all the series-connected switch tubes in the switch tube group should be blocked simultaneously; when turning on one of the switch tube groups, all the series-connected switch tubes in the switch tube group should be turned on simultaneously. Since the switch tube groups in this embodiment are divided into an outer tube group, an inner tube group, and a clamping tube group, therefore, when blocking one of the outer tube groups, all the series-connected switch tubes in the outer tube group should be blocked simultaneously, when blocking one of the inner tube groups, all the series-connected switch tubes in the inner tube group should be blocked simultaneously, and when blocking one of the clamping tube groups, all the series-connected switch tubes in the clamping tube group should be blocked simultaneously; blocking all the devices in the series group simultaneously can maximize the equal-voltage turn-off characteristic of the series devices. Failing to do so will result in unequal voltage distribution among the series devices, leading to overvoltage damage to the devices; when turning on one of the outer tube groups, all the series-connected switch tubes in the outer tube group should be turned on simultaneously, when turning on one of the inner tube groups, all the series-connected switch tubes in the inner tube group should be turned on simultaneously, and when turning on one of the clamping tube groups, all the series-connected switch tubes in the clamping tube group should be turned on simultaneously; turning on all the devices in the series group simultaneously can maximize the equal-voltage turn-on characteristic of the series devices. Failing to do so will result in unequal voltage distribution among the series devices, leading to overvoltage damage to the devices.

[0060] As a preferred technical solution, when turning on all the locked inner tube groups and clamping tube groups, all the locked switch tubes in the inner tube groups and clamping tube groups should be turned on simultaneously; when blocking all the inner tube groups and clamping tube groups, all the switch tubes in the inner tube groups and clamping tube groups should be blocked simultaneously. In this embodiment, the above method is used to issue turn-on or turn-off commands to the corresponding devices simultaneously, which can simplify the control logic, reduce the burden on the controller, and improve the control efficiency of the converter. It should be noted that whether the inner tube group and the clamping group are turned on or blocked simultaneously has no impact on the final overvoltage suppression effect.

[0061] Next, the technical advantages of the three-level converter blocking method according to the embodiment of the present invention will be further described by comparison.

[0062] The traditional blocking method applied to three-level converters usually turns off the outer switches first and then directly turns off the inner switches. This method has the problem of overvoltage on the inner switches. First, the traditional blocking method and its overvoltage problem will be briefly described below.

[0063] For Figure 1 the three-level converter topology shown, all possible output switch states are shown in Table 1.

[0064] Table 1 All possible output switch states of the ANPC-type three-level converter

[0065] Level state <![CDATA[T1]]> <![CDATA[T2]]> <![CDATA[T3]]> <![CDATA[T4]]> <![CDATA[T5]]> <![CDATA[T6]]> AC port output voltage P 1 1 0 0 0 1 +Udc / 2 OU1 0 1 0 0 1 0 0 OU2 0 1 0 1 1 0 0 OL1 0 0 1 0 0 1 0 OL2 1 0 1 0 0 1 0 N 0 0 1 1 1 0 -Udc / 2

[0066] Taking the blocking of the level state OL2 as an example, the overvoltage problem caused by the traditional blocking method is analyzed.

[0067] (a) When the level state is OL2 and the current is positive, the potential distribution of each device in the three-level topology is shown in Figure 3(a).

[0068] (b) After T1 is blocked, since there is no charging circuit to charge the parallel RC of T1, the voltage at the T1 terminal remains zero, as shown in Figure 3(b).

[0069] (c) According to the conventional blocking process, after blocking T1, T3 and T6 will be directly blocked, as shown in Figure 3(c). After blocking T6, the current flowing through T6 is forced to commutate to the RC6 path, resulting in an increase in the voltage at the T6 terminal. Since UT6 + UT4 = Udc / 2, when RC6 is charged, RC4 discharges and UT4 decreases. At the same time, since UT1 + UT2 + UT3 + UT4 = Udc, when UT4 decreases, UT1 + UT2 will increase, so RC1 and RC2 are charged. Since UT1 + UT5 = Udc / 2, when UT1 increases, UT5 decreases and RC5 discharges.

[0070] (d) When RC6 is charged to Udc / 2, the discharge of RC4 is completed and the voltage at the D4 terminal is zero and it conducts. Since RC2 is charged on the basis of Udc / 2, its final voltage is greater than Udc / 2, resulting in an overvoltage problem, as shown in Figure 3(d).

[0071] In summary, due to the voltage clamping effect of the parallel RC circuit of the outer switch device (such as T1), its potential does not change after being turned off, resulting in the voltage at the inner switch (such as T2) terminal starting to increase from Udc / 2 after all devices are blocked, ultimately leading to overvoltage.

[0072] According to the above description, due to the voltage clamping effect of the parallel RC of the T1 device, its potential does not change after turning off, resulting in the voltage at the T2 terminal increasing from Udc / 2 after all devices are blocked, ultimately leading to overvoltage. Therefore, it is necessary to improve the traditional blocking method and make the voltage at the T2 terminal drop to zero before all devices are blocked. Thus, the three-level converter blocking method of the third embodiment of the present invention is proposed.

[0073] Next, taking the blocking of the level state OL2 as an example, the effect of the blocking method proposed in the embodiment of the present invention will be described.

[0074] (a) When the level state is OL2 and the current is positive, the potential distribution of each device in the three-level topology is shown in Fig. 4(a).

[0075] (b) After the T1 tube is blocked, since there is no charging circuit to charge the parallel RC of T1, the voltage at the T1 tube terminal remains at zero, as shown in Fig. 4(b). This corresponds to the blocking of the outer tube group in the blocking method of the present invention: blocking the outer tube group in the conducting state.

[0076] (c) Turn on T2, T3, T5, and T6 all, and the parallel RC circuits of T5 and T2 discharge, as shown in Fig. 4(c). This corresponds to the blocking of the inner tube group and the clamping tube group in the blocking method of the present invention: turning on all the inner tube groups and the clamping tube groups in the blocked state.

[0077] (d) The parallel RC circuits of T5 and T2 discharge to zero voltage, so that T1 bears the Udc / 2 terminal voltage, as shown in Fig. 4(d).

[0078] (e) Block T2, T3, T5, and T6 all. The parallel RC of T2 and T6 starts to charge from zero voltage, and the parallel RC of T4 starts to discharge from the Udc / 2 voltage, as shown in Fig. 4(e). This corresponds to the blocking of all the inner tube groups and the clamping tube groups in the blocking method of the present invention: blocking all the inner tube groups and the clamping tube groups.

[0079] (f) The parallel RC of T4 discharges to zero, and the parallel RC of T2 and T6 charges to Udc / 2. There is no overvoltage problem with the T2 tube, as shown in Fig. 4(f).

[0080] In summary, for a three-level converter containing a device voltage equalization circuit (i.e., a voltage equalization buffer circuit), the three-level converter blocking method of the third embodiment of the present invention effectively avoids the problem of overvoltage during blocking.

[0081] In addition, a comparative experiment verification was also carried out on the three-level converter blocking method of the third embodiment of the present invention. Through experiments, the terminal voltage test diagrams of T1 to T6 under the traditional blocking method and the optimized blocking method proposed by the present invention were obtained respectively, as shown in Figure 5 and Figure 6As shown, the experimental results indicate that the latching method proposed by the present invention can effectively suppress the latching overvoltage of the device.

[0082] Figure 5 and Figure 6 shows the comparison of the test effects between the traditional latching method and the optimized latching method proposed by the present invention. As can be seen from Figure 5 , when the three-level converter adopts the traditional latching method, it will cause overvoltage of the inner tube (see the annotation). As can be seen from Figure 6 , when the three-level converter adopts the optimized latching method proposed by the present invention, it can effectively avoid overvoltage of the inner tube (see the annotation).

[0083] Based on the same inventive concept, the present invention also provides a computer-readable storage medium storing one or more programs, which when executed, can implement the latching method of the three-level converter as described above.

[0084] Based on the same inventive concept, the present invention also provides an electronic device, as Figure 7 shown, including a processor, a communication interface, the computer-readable storage medium as described above, and a communication bus; wherein, the processor, the communication interface, and the computer-readable storage medium communicate with each other through the communication bus; the processor is used to execute the programs stored in the computer-readable storage medium.

[0085] In the above embodiments, the descriptions of each embodiment have their own focuses. For the parts not detailed in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0086] The parts not involved in the above embodiments are the same as or can be implemented using the prior art, and will not be further described here.

[0087] Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A three-level converter locking method, wherein: The three-level converter comprises a plurality of three-level bridge arms, each of which comprises a plurality of switch tube groups consisting of at least two switch tubes connected in series; wherein both ends of the switch tube are connected in parallel with a voltage-sharing buffer circuit, and the voltage-sharing buffer circuit comprises a capacitor element; the switch tube group is divided into an outer tube group, an inner tube group and a clamp tube group, the outer tube group comprises a first outer tube group and a second outer tube group, the inner tube group comprises a first inner tube group and a second inner tube group, and the clamp tube group comprises a first clamp tube group and a second clamp tube group; characterized in that, The locking method comprises: Locking the outer tube group in the conducting state; Conducting all the inner tube groups and the clamp tube groups in a locked state; Lock all of the inner tube groups and the clamp tube groups.

2. A three-level converter locking method according to claim 1, characterized in that: After locking the outer tube group in the on state, all the inner tube groups and the clamp tube group in the locked state are turned on again after a first dead time; After all the inner tube groups and the clamp tube groups in the locked state are turned on, all the inner tube groups and the clamp tube groups are locked again after a second dead time.

3. A three-level converter locking method according to claim 2, characterized in that: The first dead time and the second dead time are both 10 to 20 microseconds.

4. A three-level converter locking method according to claim 1, characterized in that: When locking one of the switch tube groups, all the switch tubes connected in series in the switch tube group should be locked at the same time; When one of the switch tube groups is turned on, all the switch tubes connected in series in the switch tube group are turned on simultaneously.

5. A three-level converter locking method according to claim 1, characterized in that: When all the inner tube groups and the clamp tube groups in the locked state are turned on, all the switch tubes in the inner tube group and the clamp tube group in the locked state are turned on at the same time; When all of the inner tube groups and the clamp tube groups are locked, all of the switch tubes in the inner tube groups and the clamp tube groups are locked at the same time.

6. A three-level converter locking method according to any one of claims 1 to 5, characterized in that: The three-level converter is an ANPC type three-level converter; The locking method is used for locking the ANPC type three-level converter in a zero-level output state where the outer tube group is turned on.

7. A three-level converter locking method according to claim 1, characterized in that: The voltage-sharing buffer circuit adopts an RC circuit or an RCD circuit.

8. A three-level converter locking method according to claim 1, characterized in that: The switch tubes connected in series in the switch tube group are IGCT or IGBT.

9. A computer-readable storage medium storing one or more programs, characterized in that: When the one or more programs are executed, the three-level converter locking method according to any one of claims 1 to 8 can be implemented.

10. An electronic device comprising a processor, a communication interface, the computer-readable storage medium of claim 9, and a communication bus; wherein: The processor, the communication interface, and the computer-readable storage medium communicate with each other via a communication bus; It is characterized in that The processor is configured to execute a program stored in a computer-readable storage medium.

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