Converter layered overvoltage protection method suitable for three-phase alternating current power grid

Abstract

The invention discloses a converter layered overvoltage protection method suitable for a three-phase AC power grid, and the method comprises the steps: connecting a target filter between the input end of a converter and a relay board, the target filter comprises a first-stage differential mode filtering and a two-stage common mode filtering, and forming a first layer of overvoltage protection, the first-stage differential mode filtering in the target filter is used for reducing the peak value of the instantaneous high voltage passing through the three-phase alternating-current power grid by half; an external auxiliary source board is adopted to control the on-off of the relay board, and the relay board is connected with the main power module to form a second layer of overvoltage protection; setting a multi-stage overvoltage protection threshold value of the main power module according to the operation data of the three-phase AC power grid, the multi-stage overvoltage protection threshold value including an instantaneous overvoltage value and an effective value overvoltage value, and forming a third layer of overvoltage protection; and triggering and starting one of the first layer of overvoltage protection, the second layer of overvoltage protection and the third layer of protection according to the input voltage and the duration time of the three-phase alternating current power grid to carry out overvoltage protection.

Description

Technical Field

[0001] The present application relates to the technical field of electrical equipment, and more specifically, to a hierarchical overvoltage protection method for a converter applicable to a three-phase AC power grid. Background Art

[0002] A converter is a power electronic device that can change the voltage, frequency, number of phases, and other electrical quantities or characteristics of a power supply system. It is widely used in multiple fields such as power transmission and distribution systems, new energy power stations, industrial production, and transportation.

[0003] Hierarchical overvoltage protection of a converter refers to multi-stage or procedural overvoltage protection measures implemented in the converter, aiming to ensure effective protection of the device at different voltage levels. Common methods include setting multi-stage protection thresholds: according to the voltage range that the converter can withstand, multiple protection thresholds are set. When the voltage exceeds a certain threshold, corresponding protection measures are triggered, such as reducing the voltage, disconnecting the power supply, etc. Using overvoltage protection devices: such as lightning arresters, varistors, surge arresters, etc. These devices can quickly respond when the voltage rises abnormally and limit the overvoltage within a safe range.

[0004] However, each of these has its own deficiencies. For example, when encountering an instantaneous grid overvoltage, lightning arresters and the like resist it relying on their own performance. When the multi-stage protection thresholds encounter an excessively high transient voltage, they cannot guarantee that the main power circuit devices will not be damaged. Summary of the Invention

[0005] In view of at least one defect or improvement requirement of the prior art, the present invention provides a hierarchical overvoltage protection method for a converter applicable to a three-phase AC power grid, which solves the problem that the main power circuit devices may be damaged when encountering an excessively high transient voltage. A suitable filter is added to the input end of the converter to suppress the microsecond-level overvoltage surge at the input end; at the same time, an external auxiliary power source and a relay board are used to separate the main power and the auxiliary power supply. When overvoltage occurs, the power supply of the main power module can be cut off, so as to achieve the function of overvoltage fault isolation; and different overvoltage protection thresholds are set in the main power module to achieve self-recoverable overvoltage protection with different thresholds.

[0006] To achieve the above object, according to the first aspect of the present invention, a converter hierarchical overvoltage protection method applicable to a three-phase AC power grid is provided. The method includes: connecting a target filter between the input end of the converter and the relay board, where the target filter includes first-order differential-mode filtering and two-stage common-mode filtering to form the first layer of overvoltage protection. Among them, the first-order differential-mode filtering in the target filter is used to reduce the peak value of the instantaneous high voltage of the three-phase AC power grid passing through by half; using an external auxiliary power board to control the opening and closing of the relay board, and the relay board is connected to the main power module to form the second layer of overvoltage protection; setting multi-level overvoltage protection thresholds of the main power module according to the operation data of the three-phase AC power grid, where the multi-level protection thresholds include an instantaneous overvoltage value and an effective value overvoltage value to form the third layer of overvoltage protection; triggering and starting one of the first layer of overvoltage protection, the second layer of overvoltage protection, and the third layer of protection according to the input voltage and duration of the three-phase AC power grid for overvoltage protection.

[0007] In an exemplary embodiment, the using an external auxiliary power board to control the opening and closing of the relay board, and the relay board is connected to the main power module to form the second layer of overvoltage protection includes: the three-phase AC power grid enters the auxiliary power board after passing through the target filter, and after rectification, it generates low-voltage direct current to control the relay board to turn on and control the AC input of the main power module; in the case of instantaneous overvoltage of the three-phase AC power grid, control the auxiliary power board to cut off the power, cut off the relay board, and disconnect the AC input of the main power module.

[0008] In an exemplary embodiment, the setting multi-level overvoltage protection thresholds of the main power module according to the operation data of the three-phase AC power grid, where the multi-level protection thresholds include an instantaneous overvoltage value and an effective value overvoltage value to form the third layer of overvoltage protection includes: setting the first protection threshold, the second protection threshold, and the third protection threshold in the multi-level overvoltage protection thresholds of the main power module according to the operation data of the three-phase AC power grid; converting the instantaneous overvoltage value of the input voltage of the three-phase AC power grid sampled according to the operation data of the three-phase AC power grid from the three-phase stationary abc coordinate system to the two-phase rotating dq coordinate system; determining the d-axis component of the two-phase rotating dq coordinate system as the instantaneous value of the input voltage.

[0009] In an exemplary embodiment, after setting the first protection threshold, the second protection threshold, and the third protection threshold in the multi-level overvoltage protection threshold of the main power module according to the operation data of the three-phase AC power grid, the method further includes: when the input voltage of the three-phase AC power grid is greater than the effective value overvoltage value, less than the first protection threshold, and the duration is less than the response time of the auxiliary source board, starting the first-layer overvoltage protection; when the input voltage of the three-phase AC power grid is greater than the third protection threshold, less than the second protection threshold, and the duration is not less than the response time of the auxiliary source board, starting the second-layer overvoltage protection.

[0010] In an exemplary embodiment, after setting the first protection threshold, the second protection threshold, and the third protection threshold in the multi-level overvoltage protection threshold of the main power module according to the operation data of the three-phase AC power grid, the method further includes: when the input voltage of the three-phase AC power grid is greater than the instantaneous overvoltage value, less than the third protection threshold, and the duration is not less than T / k seconds, starting the third-layer overvoltage protection, where T is the period of the three-phase AC power grid and k is a positive integer; when the input voltage of the three-phase AC power grid is greater than the effective value overvoltage value, less than the instantaneous overvoltage value, and the duration is not less than n*T seconds, starting the third-layer overvoltage protection, where T is the period of the three-phase AC power grid and n is a positive integer.

[0011] In an exemplary embodiment, after setting the first protection threshold, the second protection threshold, and the third protection threshold in the multi-level overvoltage protection threshold of the main power module according to the operation data of the three-phase AC power grid, the method further includes: when it is detected that the input voltage of the three-phase AC power grid is greater than the effective value overvoltage value, less than the instantaneous overvoltage value, and the duration is greater than n*T seconds; or when it is detected that the input voltage of the three-phase AC power grid is greater than the instantaneous overvoltage value, less than the third protection threshold, and the duration is greater than T / k seconds, after alarming, entering the fault state and shutting down, and then performing self-recovery restart, where T is the period of the three-phase AC power grid, and n and k are positive integers.

[0012] In an exemplary embodiment, after setting the first protection threshold, the second protection threshold, and the third protection threshold in the multi-level overvoltage protection threshold of the main power module according to the operation data of the three-phase AC power grid, the method further includes: when it is detected that the input voltage of the three-phase AC power grid is less than the effective value overvoltage value and the duration is greater than the preset time, enabling self-recovery restart.

[0013] According to the second aspect of the present invention, there is also provided a converter hierarchical overvoltage protection device applicable to a three-phase AC power grid, which includes: a first protection unit for connecting a target filter between the input end of the converter and the relay board, the target filter including first-order differential mode filtering and two-order common mode filtering to form a first layer of overvoltage protection. Among them, the first-order differential mode filtering in the target filter is used to reduce the peak value of the instantaneous high voltage of the three-phase AC power grid passing through by half; a second protection unit for controlling the opening and closing of the relay board by using an external auxiliary source board, the relay board is connected to the main power module to form a second layer of overvoltage protection; a third protection unit for setting multi-level overvoltage protection thresholds of the main power module according to the operation data of the three-phase AC power grid, the multi-level protection thresholds including an instantaneous overvoltage value and an effective value overvoltage value to form a third layer of overvoltage protection; a start protection unit for triggering and starting one of the first layer of overvoltage protection, the second layer of overvoltage protection and the third layer of protection for overvoltage protection according to the input voltage and duration of the three-phase AC power grid.

[0014] According to the third aspect of the present invention, there is also provided a computer-readable storage medium, in which a computer program is stored. Among them, the computer program is set to execute the above-mentioned converter hierarchical overvoltage protection method applicable to a three-phase AC power grid when running.

[0015] According to the fourth aspect of the present invention, there is also provided an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. Among them, the above-mentioned processor executes the above-mentioned converter hierarchical overvoltage protection method applicable to a three-phase AC power grid through the computer program.

[0016] Generally speaking, compared with the prior art through the above technical solutions conceived by the present invention, the following beneficial effects can be achieved: (1) The present invention provides a converter hierarchical overvoltage protection method applicable to a three-phase AC power grid. By adding a suitable filter at the input end of the converter, the microsecond-level instantaneous high voltage of the power grid passes through the differential mode filtering of the filter, and the voltage peak value is reduced to half of the original. An external auxiliary source board and a relay board that are easy to replace are provided. When the power grid has an instantaneous overvoltage, the auxiliary source board will first power off, thereby cutting off the relay board and disconnecting the AC input of the main power module, so that the main power module is protected from the impact of the power grid instantaneous overvoltage. Even if the power grid has an instantaneous overvoltage, only the easily replaceable auxiliary source board will be damaged, improving the maintainability of the entire converter.

[0017] (2) Since the present invention provides instantaneous overvoltage protection and effective value overvoltage protection, the instantaneous overvoltage protection uses the d-axis component Ud in the dq coordinate system for instantaneous overvoltage protection, which improves the timeliness of overvoltage protection of the main power module. The effective value overvoltage protection takes the average value over multiple cycles, avoiding frequent triggering of overvoltage protection when the instantaneous input voltage does not reach the instantaneous overvoltage protection value but exceeds the effective value overvoltage protection value, which affects the stable operation of the converter and improves the stable operation ability of the main power module in the face of a fluctuating power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figure 1 It is a schematic flowchart of a hierarchical overvoltage protection method for a converter applicable to a three-phase AC power grid provided by an embodiment of the present application; Figure 2 It is a schematic block diagram of a hierarchical overvoltage protection structure provided by an embodiment of the present application; Figure 3 It is a schematic overall effect diagram of hierarchical overvoltage provided by an embodiment of the present application; Figure 4 It is a schematic diagram of a simulation model for overvoltage suppression effect of a π-shaped filter provided by an embodiment of the present application; Figure 5 It is a schematic diagram of reporting an input overvoltage warning signal provided by an embodiment of the present application; Figure 6 It is a software flowchart of input overvoltage warning provided by an embodiment of the present application; Figure 7 It is a schematic structural diagram of a hierarchical overvoltage protection device for a converter applicable to a three-phase AC power grid provided by an embodiment of the present application; Figure 8 It is a schematic structural diagram of an electronic device provided by an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further details the present invention with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0021] In the description, claims and above-mentioned drawings of this application, the terms "first", "second", "third", etc. are used to distinguish different objects rather than to describe a specific order. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally further include steps or units not listed, or may optionally further include other steps or units inherent to these processes, methods, products or devices.

[0022] According to one aspect of the embodiments of the present application, a converter hierarchical overvoltage protection method applicable to a three-phase AC power grid is provided. The following combines Figure 1 to describe the converter hierarchical overvoltage protection method provided by the embodiments of the present application.

[0023] Figure 1 is a schematic flow chart of an optional converter hierarchical overvoltage protection method provided by the embodiments of the present application. As Figure 1 shown, the flow of this method may include the following steps: S102, connect a target filter between the input end of the converter and the relay board. The target filter includes first-order differential mode filtering and two-stage common mode filtering to form the first layer of overvoltage protection. Among them, the first-order differential mode filtering in the target filter is used to reduce the peak value of the instantaneous high voltage of the three-phase AC power grid passing through by half; S104, use an external auxiliary source board to control the opening and closing of the relay board. The relay board is connected to the main power module to form the second layer of overvoltage protection; S106, set multi-level overvoltage protection thresholds for the main power module according to the operation data of the three-phase AC power grid. The multi-level protection thresholds include instantaneous overvoltage values and effective value overvoltage values to form the third layer of overvoltage protection; S108, trigger and start one of the first layer of overvoltage protection, the second layer of overvoltage protection and the third layer of protection for overvoltage protection according to the input voltage and duration of the three-phase AC power grid.

[0024] The converter hierarchical overvoltage protection method provided by the present application can be applied to the scenario where the entire converter realizes hierarchical overvoltage protection.

[0025] Exemplarily, Figure 2 is an optional block diagram of a hierarchical overvoltage protection structure provided by the embodiments of the present application. As Figure 2As shown, the hierarchical overvoltage protection structure mainly includes four parts. The first part is the filter, the second part is the auxiliary power board, the third part is the relay board, and the fourth part is the main power board. The hierarchical overvoltage protection method proposed in this application includes: Layer I overvoltage protection (the first layer overvoltage protection): The target filter (i.e., the filter schematically shown in Figure 2 ) serves as the Layer I overvoltage protection, reducing the input voltage peak from the input source, filtering out the high-frequency interference generated during the operation of the converter with the target filter, and suppressing the microsecond-level overvoltage surge at the input end, thereby reducing the input voltage peak; Layer II overvoltage protection (the second layer overvoltage protection): A separate auxiliary power board controls the external relay (i.e., the relay board schematically shown in Figure 2 ). When encountering external high voltage, the auxiliary power supply is first cut off, and then the relay is turned off to protect the safety of the main power module (i.e., the main power board schematically shown in Figure 2 ); The auxiliary power board and the relay board serve as the Layer II overvoltage protection. When the power grid is overvoltage, the auxiliary power board first cuts off the power supply due to overvoltage protection, and then disconnects the relay board to cut off the input of the main power module, thereby protecting the main power module; Layer III overvoltage protection (the third layer overvoltage protection): Multiple protection thresholds are adopted inside the main power module, and protection is carried out according to the effective value overvoltage value or the instantaneous overvoltage value of the input voltage. The instantaneous overvoltage value protection and the effective value overvoltage value protection inside the main power module serve as the Layer III overvoltage protection to prevent the main power module devices from being burned out due to power grid overvoltage.

[0026] Optionally, in the embodiment of this application, a suitable filter is added at the input end of the converter. The filter has one-stage differential mode filtering and two-stage common mode filtering. The instantaneous overvoltage appears as interference in the differential mode. For this, in the differential mode filter circuit, for the instantaneous overvoltage problem, the differential mode inductor L uses a composite magnetic core to mainly suppress the voltage interference in the 2KHz - 1MHz frequency band of the instantaneous pulse interference.

[0027] Furthermore, multiple overvoltage protection thresholds of the main power module are set according to the operation data of the three-phase AC power grid. Here, the multiple protection thresholds include the instantaneous overvoltage value and the effective value overvoltage value, and then the specific overvoltage protection type is determined according to the input voltage and the duration of the three-phase AC power grid for overvoltage protection.

[0028] Through the above steps S102 to S108, by connecting a target filter between the input end of the converter and the relay board, the target filter includes first-order differential mode filtering and two-order common mode filtering, forming a first-layer overvoltage protection. Among them, the first-order differential mode filtering in the target filter is used to reduce the peak value of the instantaneous high voltage of the three-phase AC power grid passing through by half; an external auxiliary source board is used to control the opening and closing of the relay board, and the relay board is connected to the main power module, forming a second-layer overvoltage protection; according to the operating data of the three-phase AC power grid, multi-level overvoltage protection thresholds of the main power module are set, and the multi-level protection thresholds include instantaneous overvoltage values and effective value overvoltage values, forming a third-layer overvoltage protection; according to the input voltage and duration of the three-phase AC power grid, one of the first-layer overvoltage protection, the second-layer overvoltage protection, and the third-layer protection is triggered to start overvoltage protection, solving the problem that the main power circuit devices may be damaged when encountering too high transient voltage, adding a suitable filter at the input end of the converter to suppress the microsecond-level overvoltage surge at the input end; at the same time, the external auxiliary source and the relay board separate the main power and the auxiliary power supply, and the main power module power supply can be cut off during overvoltage, so as to achieve the function of overvoltage fault isolation; and different overvoltage protection thresholds are set in the main power module to achieve self-recoverable overvoltage protection with different thresholds.

[0029] In an exemplary embodiment, the use of an external auxiliary source board to control the opening and closing of the relay board, and the relay board is connected to the main power module, forming a second-layer overvoltage protection includes: S11, the three-phase AC power grid enters the auxiliary source board after passing through the target filter, and after rectification, it generates low-voltage direct current to control the relay board to turn on and control the AC input of the main power module; S12, in the case of instantaneous overvoltage of the three-phase AC power grid, control the auxiliary source board to cut off the power, cut off the relay board, and disconnect the AC input of the main power module.

[0030] In this embodiment, as Figure 2 shown, the auxiliary source is placed outside the converter at a position convenient for replacement, and at the same time, a relay board is added. The three-phase AC power grid enters the auxiliary source board after passing through the filter, and after rectification, it generates low-voltage direct current to control the relay board to turn on, thereby controlling the AC input of the main power module.

[0031] Through this embodiment, from the perspective of the composition structure of the converter, the auxiliary source board and the relay board play a role in isolating the input overvoltage from the main power module. When the power grid has an instantaneous overvoltage, the auxiliary source board first performs overvoltage protection, disconnects the relay board, and cuts off the input of the main power module, preventing the main power module devices from being damaged by overvoltage.

[0032] In an exemplary embodiment, setting the multi-level overvoltage protection thresholds of the main power module according to the operating data of the three-phase AC power grid, the multi-level protection thresholds include an instantaneous overvoltage value and an effective value overvoltage value, and forming the third layer of overvoltage protection includes: S21. Set the first protection threshold, the second protection threshold, and the third protection threshold in the multi-level overvoltage protection thresholds of the main power module according to the operating data of the three-phase AC power grid; S22. Convert the instantaneous overvoltage value of the input voltage of the three-phase AC power grid sampled according to the operating data of the three-phase AC power grid from the three-phase stationary abc coordinate system to the two-phase rotating dq coordinate system; S23. Determine the d-axis component of the two-phase rotating dq coordinate system as the instantaneous value of the input voltage.

[0033] In this embodiment, as Figure 3 shown, set the first protection threshold (Va), the second protection threshold (Vb), and the third protection threshold (Vc) in the multi-level overvoltage protection thresholds of the main power module according to the operating data of the three-phase AC power grid.

[0034] Exemplarily, in the main power module, multi-level overvoltage protection points of the instantaneous overvoltage value Vd and the effective value overvoltage value Ve are designed. For the instantaneous overvoltage, the instantaneous values of the three-phase input voltage obtained by sampling are converted from the three-phase stationary abc coordinate system to the two-phase rotating dq coordinate system, and the d-axis component Ud is the instantaneous value of the input voltage, and Ud is used for instantaneous input overvoltage protection. For the effective value overvoltage protection, the average value is taken over multiple cycles, and the relationship between the two is Vd > Ve.

[0035] Through this embodiment, for the instantaneous overvoltage protection and the effective value overvoltage protection, the instantaneous overvoltage protection uses the d-axis component Ud of the dq coordinate system for instantaneous overvoltage protection, which improves the timeliness of the overvoltage protection of the main power module. The effective value overvoltage protection takes the average value over multiple cycles, avoiding frequent triggering of overvoltage protection when the instantaneous input voltage does not reach the instantaneous overvoltage protection value but exceeds the effective value overvoltage protection value, which affects the stable operation of the converter, and improves the stable operation ability of the main power module in the face of a fluctuating power grid.

[0036] In an exemplary embodiment, after setting the first protection threshold, the second protection threshold, and the third protection threshold in the multi-level overvoltage protection thresholds of the main power module according to the operating data of the three-phase AC power grid, the method further includes: S31. When the input voltage of the three-phase AC power grid is greater than the effective value overvoltage value, less than the first protection threshold, and the duration is less than the response time of the auxiliary source board, start the first layer of overvoltage protection; S32. When the input voltage of the three-phase AC power grid is greater than the third protection threshold, less than the second protection threshold, and the duration is not less than the response time of the auxiliary source board, start the second-layer overvoltage protection.

[0037] In this embodiment, as Figure 3 shown, for the overall effect of the hierarchical overvoltage protection of the converter, the input voltage V satisfies Ve < V < Va, that is, greater than the effective value overvoltage value and less than the first protection threshold, and the duration is less than T1 seconds. The first-layer overvoltage protection is started to reduce the input voltage peak value and protect the devices at the back end of the filter. The input voltage V satisfies Vc < V < Vb, that is, greater than the third protection threshold and less than the second protection threshold, and the action time is not less than T1 seconds. T1 is the response time of the auxiliary source board module. The second-layer overvoltage protection is started, which can cut off the auxiliary source power supply, thereby cutting off the AC input of the main power module and protecting the main power module.

[0038] As Figure 4 shown, from the aspect of converter overvoltage suppression, the differential-mode filtering part of the filter can reduce the peak value of different microsecond-level power grid overvoltage signals by half. The interference source is Figure 4 V1 in, U1 is a switching power supply, and the line-to-line differential-mode inductor is equivalent to Figure 4 the inductor L2 in; the high-frequency resistance of the inductor L2 under pulsed high current is set to 2 ohms. The line-to-line differential-mode capacitance is simulated by the resistor R1, and the line-to-line metal oxide varistor (MOV) is simulated by the capacitor C1 + resistor R7 and the capacitor C4 + resistor R8. The equivalent model under high-frequency pulse conditions is the switching power supply U2 + resistor R4 or the switching power supply U3 + resistor R5, and the equivalent input impedance of the ACDC (AC-DC conversion) is the resistor R3. In addition, the simulation experiment shows that in the double-exponential pulse waveform, the first curve is a double-exponential voltage signal with a peak value of 410V and a pulse width of 120uS, and the second curve is the voltage signal applied to the load end after being attenuated by the filter circuit, with an actual peak value of about 200V and an attenuation amount close to half. In the square-wave pulse waveform, the first curve is a square-wave interference voltage signal with a peak value of 410V and a pulse width of 120uS, and the second curve is the voltage signal applied to the load end after being attenuated by the filter circuit, with an actual peak value of about 230V and an attenuation amount close to 45%.

[0039] Through this embodiment, from the aspect of converter overvoltage suppression, the differential-mode filtering part of the filter can reduce the peak value of different power grid overvoltage signals within microseconds by half. From the perspective of the converter structure composition, the fault point caused by the power grid overvoltage is transferred to the auxiliary source board that is easy to replace, improving the maintainability of the entire converter. From the perspective of the timeliness of the converter main power module, instantaneous overvoltage protection is added on the basis of the traditional effective value overvoltage protection, and its protection time for instantaneous high voltage is greatly shortened.

[0040] In an exemplary embodiment, after setting the first protection threshold, the second protection threshold, and the third protection threshold of the multi-level overvoltage protection threshold of the main power module according to the operation data of the three-phase AC power grid, the method further includes: S41. When the input voltage of the three-phase AC power grid is greater than the instantaneous overvoltage value, less than the third protection threshold, and the duration is not less than T / k seconds, activate the third-layer overvoltage protection, where T is the period of the three-phase AC power grid and k is a positive integer; S42. When the input voltage of the three-phase AC power grid is greater than the effective value overvoltage value, less than the instantaneous overvoltage value, and the duration is not less than n*T seconds, activate the third-layer overvoltage protection, where T is the period of the three-phase AC power grid and n is a positive integer.

[0041] In this embodiment, the input voltage V satisfies Vd < V < Vc, that is, greater than the instantaneous overvoltage value, less than the third protection threshold, and the action time is not less than T / k seconds. The instantaneous overvoltage protection of the third-layer overvoltage protection is activated, and the drive of the main power module can be turned off to protect the related devices of the main power module. The input voltage V satisfies Ve < V < Vd, that is, greater than the effective value overvoltage value, less than the instantaneous overvoltage value, and the action time is not less than n*T seconds. The effective value overvoltage protection of the third-layer overvoltage protection is activated, and the drive of the main power module can be turned off to protect the related devices of the main power module. Here, n is an integer value, n ≥ 1, and k is an integer value, generally taking 2 to 6.

[0042] Through this embodiment, from the perspective of the timeliness of the main power module of the converter, the response time of the instantaneous overvoltage protection is greatly shortened compared with the traditional overvoltage protection time. In order to generate input overvoltage protection within a time less than one switching period of the input voltage fluctuation, the instantaneous values of the three-phase input voltage obtained by sampling are converted from the three-phase stationary abc coordinate system to the two-phase rotating dq coordinate system. The d-axis component Ud is the instantaneous value of the input voltage, and Ud is used for instantaneous input overvoltage protection.

[0043] In an exemplary embodiment, after setting the first protection threshold, the second protection threshold, and the third protection threshold of the multi-level overvoltage protection threshold of the main power module according to the operation data of the three-phase AC power grid, the method further includes: S51. When it is detected that the input voltage of the three-phase AC power grid is greater than the effective value overvoltage value, less than the instantaneous overvoltage value, and the duration is greater than n*T seconds; or S52. When it is detected that the input voltage of the three-phase AC power grid is greater than the instantaneous overvoltage value, less than the third protection threshold, and the duration is greater than T / k seconds, after alarming, enter the fault state for shutdown, and perform self-recovery restart, where T is the period of the three-phase AC power grid, and n and k are positive integers.

[0044] In this embodiment, in combination with Figure 5 and Figure 6 as shown, by using the AC / DC high-voltage power supply module 1 (AC / DC conversion high-voltage power supply module 1) and the AC / DC high-voltage power supply module 2 (AC / DC conversion high-voltage power supply module), the internal input overvoltage alarm reporting process of the main power module is as follows: The input voltage inside the main power module first passes through Hall voltage sampling and operational amplifier processing and then enters the rectifier control board. If "AC input overvoltage" is triggered after calculation, the alarm is generated by the rectifier control board, transmitted to the conversion board control board through inter-board communication, then transmitted to the communication control board through the internal CAN (internal controller area network), and finally reported to the backend through the external CAN (external controller area network).

[0045] It should be noted that the sampling ratio of Hall voltage sampling can be 2.5:1. UA, UB, and UC are phase voltages. Specifically, UA is the voltage of phase A relative to the neutral point, UB is the voltage of phase B relative to the neutral point, and UC is the voltage of phase C relative to the neutral point; UAB, UBC, and UCA are line voltages between three phases. Specifically, UAB is the voltage between phase A and phase B, UBC is the voltage between phase B and phase C, and UCA is the voltage between phase C and phase A.

[0046] When it is detected that the input voltage V satisfies Ve < V < Vd (that is, greater than the effective value overvoltage value and less than the instantaneous overvoltage value) and the duration is greater than n*T seconds, or the input voltage V satisfies Vd < V < Vc (that is, greater than the instantaneous overvoltage value and less than the third protection threshold) and the duration is greater than T / k seconds, "AC input overvoltage" is alarmed, and it enters the fault state and stops, the fault light is on, and it can be self-recovered, where T is the period of the AC power grid, n is an integer value, n ≥ 1, and k is an integer value, generally taking 2 to 6.

[0047] Through this embodiment, from the perspective of the stable operation ability in the face of a fluctuating power grid, the effective value overvoltage protection takes the average value of the input voltage in multiple switching cycles. In this way, when the input voltage Ve < V < Vd but the duration does not exceed n*T seconds, the input overvoltage alarm will not be triggered, thus improving the stability of the converter in the face of a fluctuating power grid.

[0048] In an exemplary embodiment, after setting the first protection threshold, the second protection threshold, and the third protection threshold of the multi-level overvoltage protection threshold of the main power module according to the operation data of the three-phase AC power grid, the method further includes: S61, when it is detected that the input voltage of the three-phase AC power grid is less than the effective value overvoltage value and the duration is greater than the preset time, start self-recovery restart.

[0049] In this embodiment, when it is detected that the input voltage is less than Ve and the duration is greater than a preset time, for example, after 10s, it will restart with self-recovery.

[0050] In this embodiment, when the third-layer overvoltage protection is enabled, the specific operating software process is as follows: the input voltage is detected. When it is detected that the input voltage is less than the effective value overvoltage value and the duration is greater than 10 seconds, self-recovery can be started and then restarted. The effective value overvoltage protection adopts the average value of multiple cycles, which avoids frequent triggering of overvoltage protection when the instantaneous input voltage does not reach the instantaneous overvoltage protection value but exceeds the effective value overvoltage protection value, affecting the stable operation of the converter, and improves the stable operation ability of the main power module in the face of a fluctuating power grid.

[0051] According to another aspect of the embodiments of the present application, there is also provided an overvoltage protection device for implementing the above-mentioned converter hierarchical overvoltage protection method applicable to a three-phase AC power grid. Figure 7 It is a schematic structural diagram of an optional converter hierarchical overvoltage protection device according to the embodiments of the present application, as Figure 7 shown. The device may include: A first protection unit 702, configured to connect a target filter between the input end of the converter and the relay board. The target filter includes first-order differential mode filtering and two-stage common mode filtering to form the first layer of overvoltage protection. Among them, the first-order differential mode filtering in the target filter is used to reduce the peak value of the instantaneous high voltage of the three-phase AC power grid passing through by half; A second protection unit 704, configured to control the opening and closing of the relay board by using an external auxiliary source board. The relay board is connected to the main power module to form the second layer of overvoltage protection; A third protection unit 706, configured to set multi-level overvoltage protection thresholds for the main power module according to the operation data of the three-phase AC power grid. The multi-level protection thresholds include an instantaneous overvoltage value and an effective value overvoltage value to form the third layer of overvoltage protection; A start protection unit 708, configured to trigger and start one of the first layer of overvoltage protection, the second layer of overvoltage protection, and the third layer of protection for overvoltage protection according to the input voltage and duration of the three-phase AC power grid.

[0052] It should be noted that the first protection unit 702 in this embodiment can be used to execute the above step S102, the second protection unit 704 in this embodiment can be used to execute the above step S104, the third protection unit 706 in this embodiment can be used to execute the above step S106, and the start protection unit 708 in this embodiment can be used to execute the above step S108.

[0053] Through the above-mentioned module, by connecting a target filter between the input end of the converter and the relay board, the target filter includes first-order differential mode filtering and two-order common mode filtering, forming a first-layer overvoltage protection. Among them, the first-order differential mode filtering in the target filter is used to reduce the peak value of the instantaneous high voltage of the passing three-phase AC power grid by half; an external auxiliary source board is used to control the opening and closing of the relay board, and the relay board is connected to the main power module to form a second-layer overvoltage protection; according to the operating data of the three-phase AC power grid, multi-level overvoltage protection thresholds of the main power module are set, and the multi-level protection thresholds include an instantaneous overvoltage value and an effective value overvoltage value, forming a third-layer overvoltage protection; according to the input voltage and duration of the three-phase AC power grid, one of the first-layer overvoltage protection, the second-layer overvoltage protection, and the third-layer protection is triggered to perform overvoltage protection, solving the problem that the main power circuit devices may be damaged when encountering too high transient voltage, adding a suitable filter at the input end of the converter to suppress the microsecond-level overvoltage surge at the input end; at the same time, the external auxiliary source and the relay board separate the main power and the auxiliary power supply, and the main power module power supply can be cut off during overvoltage, so as to achieve the function of overvoltage fault isolation; and different overvoltage protection thresholds are set in the main power module to achieve self-recoverable overvoltage protection with different thresholds.

[0054] In an exemplary embodiment, the second protection unit includes: A first control module, configured to enable the three-phase AC power grid to enter the auxiliary source board after passing through the target filter, generate low-voltage direct current after rectification to control the relay board to turn on, and control the AC input of the main power module; A second control module, configured to control the auxiliary source board to cut off power, cut off the relay board, and disconnect the AC input of the main power module in the case of instantaneous overvoltage of the three-phase AC power grid.

[0055] In an exemplary embodiment, the third protection unit includes: A setting module, configured to set a first protection threshold, a second protection threshold, and a third protection threshold in the multi-level overvoltage protection thresholds of the main power module according to the operating data of the three-phase AC power grid; A conversion module, configured to convert the instantaneous overvoltage value of the input voltage of the three-phase AC power grid sampled according to the operating data of the three-phase AC power grid from the three-phase stationary abc coordinate system to the two-phase rotating dq coordinate system; A determination module, configured to determine the d-axis component of the two-phase rotating dq coordinate system as the instantaneous value of the input voltage.

[0056] In an exemplary embodiment, the device further includes: A first starting unit, configured to start the first-layer overvoltage protection when the input voltage of the three-phase AC power grid is greater than the effective value overvoltage value, less than the first protection threshold, and the duration is less than the response time of the auxiliary source board; A second starting unit, configured to start the second-layer overvoltage protection when the input voltage of the three-phase AC power grid is greater than the third protection threshold, less than the second protection threshold, and the duration is not less than the response time of the auxiliary source board.

[0057] In an exemplary embodiment, the device further includes: A third starting unit, configured to start the third-layer overvoltage protection when the input voltage of the three-phase AC power grid is greater than the instantaneous overvoltage value, less than the third protection threshold, and the duration is not less than T / k seconds, where T is the period of the three-phase AC power grid and k is a positive integer; A fourth starting unit, configured to start the third-layer overvoltage protection when the input voltage of the three-phase AC power grid is greater than the effective value overvoltage value, less than the instantaneous overvoltage value, and the duration is not less than n*T seconds, where T is the period of the three-phase AC power grid and n is a positive integer.

[0058] In an exemplary embodiment, the device further includes: An alarm unit, configured to: when it is detected that the input voltage of the three-phase AC power grid is greater than the effective value overvoltage value, less than the instantaneous overvoltage value, and the duration is greater than n*T seconds; or when it is detected that the input voltage of the three-phase AC power grid is greater than the instantaneous overvoltage value, less than the third protection threshold, and the duration is greater than T / k seconds, after giving an alarm, enter the fault state and stop, and perform self-recovery restart, where T is the period of the three-phase AC power grid, and n, k are positive integers.

[0059] In an exemplary embodiment, the device further includes: A restart unit, configured to start self-recovery restart when it is detected that the input voltage of the three-phase AC power grid is less than the effective value overvoltage value and the duration is greater than a preset time.

[0060] It should be noted here that the examples and scenarios implemented by the above modules and the corresponding steps are the same, but are not limited to the content disclosed in the above embodiments. It should be noted that the above modules, as part of the device, can run in a hardware environment, can be implemented by software, or can be implemented by hardware, where the hardware environment includes a network environment.

[0061] According to another aspect of the embodiments of the present application, a storage medium is further provided. Optionally, in this embodiment, the above storage medium may be used to execute the program code of any one of the above converter hierarchical overvoltage protection methods applicable to a three-phase AC power grid in the embodiments of the present application.

[0062] Optionally, in this embodiment, the storage medium is configured to store program code for performing the following steps: S1. Connect a target filter between the input end of the converter and the relay board. The target filter includes first-order differential-mode filtering and two-stage common-mode filtering to form the first layer of overvoltage protection. Among them, the first-order differential-mode filtering in the target filter is used to reduce the peak value of the instantaneous high voltage of the three-phase AC power grid passing through by half; S2. Use an external auxiliary power board to control the opening and closing of the relay board. The relay board is connected to the main power module to form the second layer of overvoltage protection; S3. Set multi-level overvoltage protection thresholds for the main power module according to the operation data of the three-phase AC power grid. The multi-level protection thresholds include instantaneous overvoltage values and effective value overvoltage values to form the third layer of overvoltage protection; S4. Trigger and start one of the first layer of overvoltage protection, the second layer of overvoltage protection, and the third layer of protection for overvoltage protection according to the input voltage and duration of the three-phase AC power grid.

[0063] Optionally, specific examples in this embodiment may refer to the examples described in the above embodiments, and will not be elaborated herein.

[0064] Among them, the computer-readable storage medium may include, but is not limited to, any type of disk, including floppy disks, optical disks, DVDs, CD-ROMs, microdrives, and magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, DRAMs, VRAMs, flash memory devices, magnetic cards or optical cards, nano-systems (including molecular memory ICs), or any type of medium or device suitable for storing instructions and / or data.

[0065] According to another aspect of the embodiments of the present application, an electronic device for implementing the above converter hierarchical overvoltage protection method applicable to a three-phase AC power grid is further provided. The electronic device may be a server, a terminal, or a combination thereof.

[0066] Figure 8 is a schematic structural diagram of an optional electronic device according to the embodiments of the present application. As Figure 8 shown, it includes a processor 802, a communication interface 804, a memory 806, and a communication bus 808. Among them, the processor 802, the communication interface 804, and the memory 806 communicate with each other through the communication bus 808. Among them, A memory 806 for storing computer programs; A processor 802, when executing the computer programs stored on the memory 806, implements the following steps: S1. Connect a target filter between the input end of the converter and the relay board. The target filter includes first-order differential-mode filtering and two-order common-mode filtering to form a first-layer overvoltage protection. Among them, the first-order differential-mode filtering in the target filter is used to reduce the peak value of the instantaneous high voltage of the three-phase AC power grid passing through by half; S2. Use an external auxiliary source board to control the opening and closing of the relay board. The relay board is connected to the main power module to form a second-layer overvoltage protection; S3. Set multi-level overvoltage protection thresholds of the main power module according to the operation data of the three-phase AC power grid. The multi-level protection thresholds include an instantaneous overvoltage value and an effective value overvoltage value to form a third-layer overvoltage protection; S4. Trigger and start one of the first-layer overvoltage protection, the second-layer overvoltage protection, and the third-layer protection for overvoltage protection according to the input voltage and duration of the three-phase AC power grid.

[0067] Optionally, the communication bus can be a PCI (Peripheral Component Interconnect) bus, an EISA (Extended Industry Standard Architecture) bus, etc. The communication bus can be divided into an address bus, a data bus, a control bus, etc. For the convenience of representation, Figure 8 only a thick line is used to represent it in the figure, but it does not mean that there is only one bus or one type of bus. The communication interface is used for communication between the above-mentioned electronic device and other devices.

[0068] The memory may include a RAM, and may also include a non-volatile memory, for example, at least one disk memory. Optionally, the memory may also be at least one storage device located far from the aforementioned processor.

[0069] As an example, the above memory 806 may but is not limited to include the first protection unit 702, the second protection unit 704, the third protection unit 706, and the start protection unit 708 in the above converter hierarchical overvoltage protection device applicable to a three-phase AC power grid. In addition, it may also include but is not limited to other module units in the above converter hierarchical overvoltage protection device applicable to a three-phase AC power grid, which will not be elaborated in this example.

[0070] The above-mentioned processor can be a general-purpose processor, including but not limited to: CPU (Central Processing Unit, central processing unit), NP (Network Processor, network processor), etc.; it can also be a DSP (Digital Signal Processing, digital signal processor), ASIC (Application Specific Integrated Circuit, application-specific integrated circuit), FPGA (Field-Programmable Gate Array, field-programmable gate array) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components.

[0071] Optionally, the specific examples in this embodiment may refer to the examples described in the above embodiments, and will not be elaborated herein.

[0072] It should be noted that, for the foregoing method embodiments, for simplicity of description, they are all expressed as a series of action combinations. However, those skilled in the art should know that this application is not limited by the described action sequence, because according to this application, certain steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily essential to this application.

[0073] In the above embodiments, the descriptions of the various embodiments have their own emphases. For the parts not detailed in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0074] In several embodiments provided by this application, it should be understood that the disclosed device can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed coupling or direct coupling or communication connection between each other can be through some service interfaces. The indirect coupling or communication connection of the device or unit can be in an electrical or other form.

[0075] The units described as separate components may or may not be physically separated. The components displayed as units may or may not be physical units, that is, they can be located in one place, or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0076] In addition, in each embodiment of the present application, each functional unit can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of a software functional unit.

[0077] If the above-mentioned integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable memory. Based on such an understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a memory and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in each embodiment of the present application. The aforementioned memory includes: various media such as USB flash drives, read-only memories (ROMs), random access memories (RAMs), external hard drives, magnetic disks, or optical discs that can store program codes.

[0078] Those of ordinary skill in the art can understand that all or part of the steps in the various methods of the above embodiments can be completed by instructing relevant hardware through a program. This program can be stored in a computer-readable memory, and the memory can include: flash drives, read-only memories (ROMs), random access memories (RAMs), magnetic disks, or optical discs, etc.

[0079] The above are only exemplary embodiments of the present disclosure, and the scope of the present disclosure cannot be limited thereby. That is, any equivalent changes and modifications made in accordance with the teachings of the present disclosure still fall within the scope covered by the present disclosure. After considering the specification and practicing the disclosure herein, those skilled in the art will readily conceive of other embodiments of the present disclosure. The present application aims to cover any variations, uses, or adaptations of the present disclosure, which follow the general principles of the present disclosure and include common general knowledge or conventional technical means in the technical field not recorded in the present disclosure. The specification and embodiments are only regarded as exemplary, and the scope and spirit of the present disclosure are defined by the claims.

[0080] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered that the scope described in this specification is covered.

[0081] Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A hierarchical overvoltage protection method for a converter applicable to a three-phase AC power grid, characterized in that, Including: Connect a target filter between the input end of the converter and the relay board. The target filter includes first-order differential mode filtering and two-stage common mode filtering to form the first-layer overvoltage protection. Among them, the first-order differential mode filtering in the target filter is used to reduce the peak value of the instantaneous high voltage of the three-phase AC power grid passing through by half; Use an external auxiliary source board to control the opening and closing of the relay board. The relay board is connected to the main power module to form the second-layer overvoltage protection; Set multi-level overvoltage protection thresholds of the main power module according to the operation data of the three-phase AC power grid. The multi-level protection thresholds include instantaneous overvoltage values and effective value overvoltage values to form the third-layer overvoltage protection; Trigger and start one of the first-layer overvoltage protection, the second-layer overvoltage protection, and the third-layer protection for overvoltage protection according to the input voltage and duration of the three-phase AC power grid.

2. The converter hierarchical overvoltage protection method applicable to a three-phase AC power grid according to claim 1, characterized in that, The step of using an external auxiliary source board to control the opening and closing of the relay board, and the relay board is connected to the main power module to form the second-layer overvoltage protection includes: The three-phase AC power grid enters the auxiliary source board after passing through the target filter, and after rectification, it generates low-voltage direct current to control the relay board to turn on and control the AC input of the main power module; In the case of instantaneous overvoltage of the three-phase AC power grid, control the auxiliary source board to cut off the power, cut off the relay board, and disconnect the AC input of the main power module.

3. The converter hierarchical overvoltage protection method applicable to a three-phase AC power grid according to claim 1, wherein The step of setting multi-level overvoltage protection thresholds of the main power module according to the operation data of the three-phase AC power grid, and the multi-level protection thresholds include instantaneous overvoltage values and effective value overvoltage values to form the third-layer overvoltage protection includes: Set the first protection threshold, the second protection threshold, and the third protection threshold in the multi-level overvoltage protection thresholds of the main power module according to the operation data of the three-phase AC power grid; Convert the instantaneous overvoltage value of the input voltage of the three-phase AC power grid sampled according to the operation data of the three-phase AC power grid from the three-phase stationary abc coordinate system to the two-phase rotating dq coordinate system; Determine the d-axis component of the two-phase rotating dq coordinate system as the instantaneous value of the input voltage.

4. The converter hierarchical overvoltage protection method applicable to a three-phase AC power grid according to claim 3, wherein After setting the first protection threshold, the second protection threshold, and the third protection threshold in the multi-level overvoltage protection thresholds of the main power module according to the operation data of the three-phase AC power grid, the method further includes: In the case where the input voltage of the three-phase AC power grid is greater than the effective value overvoltage value, less than the first protection threshold, and the duration is less than the response time of the auxiliary source board, start the first-layer overvoltage protection; In the case where the input voltage of the three-phase AC power grid is greater than the third protection threshold, less than the second protection threshold, and the duration is not less than the response time of the auxiliary source board, start the second-layer overvoltage protection.

5. The converter hierarchical overvoltage protection method applicable to a three-phase AC power grid according to claim 3, wherein After setting the first protection threshold, the second protection threshold, and the third protection threshold in the multi-level overvoltage protection thresholds of the main power module according to the operation data of the three-phase AC power grid, the method further includes: When the input voltage of the three-phase AC power grid is greater than the instantaneous overvoltage value, less than the third protection threshold, and the duration is not less than T / k seconds, the third-layer overvoltage protection is started, where T is the period of the three-phase AC power grid and k is a positive integer; When the input voltage of the three-phase AC power grid is greater than the effective value overvoltage value, less than the instantaneous overvoltage value, and the duration is not less than n*T seconds, the third-layer overvoltage protection is started, where T is the period of the three-phase AC power grid and n is a positive integer.

6. The converter hierarchical overvoltage protection method applicable to a three-phase AC power grid according to claim 3, characterized in that, After setting the first protection threshold, the second protection threshold, and the third protection threshold of the multi-level overvoltage protection threshold of the main power module according to the operation data of the three-phase AC power grid, the method further includes: When it is detected that the input voltage of the three-phase AC power grid is greater than the effective value overvoltage value, less than the instantaneous overvoltage value, and the duration is greater than n*T seconds; or When it is detected that the input voltage of the three-phase AC power grid is greater than the instantaneous overvoltage value, less than the third protection threshold, and the duration is greater than T / k seconds, after alarming, enter the fault state and stop, and perform self-recovery restart, where T is the period of the three-phase AC power grid, and n and k are positive integers.

7. The converter hierarchical overvoltage protection method applicable to a three-phase AC power grid according to claim 3, characterized in that, After setting the first protection threshold, the second protection threshold, and the third protection threshold of the multi-level overvoltage protection threshold of the main power module according to the operation data of the three-phase AC power grid, the method further includes: When it is detected that the input voltage of the three-phase AC power grid is less than the effective value overvoltage value and the duration is greater than the preset time, the self-recovery restart is enabled.

8. A converter hierarchical overvoltage protection device applicable to a three-phase AC power grid, characterized in that, Including: The first protection unit is used to connect a target filter between the input end of the converter and the relay board. The target filter includes first-order differential mode filtering and second-order common mode filtering to form the first-layer overvoltage protection. Among them, the first-order differential mode filtering in the target filter is used to reduce the peak value of the instantaneous high voltage of the three-phase AC power grid passing through by half; The second protection unit is used to control the opening and closing of the relay board by using an external auxiliary source board. The relay board is connected to the main power module to form the second-layer overvoltage protection; The third protection unit is used to set the multi-level overvoltage protection threshold of the main power module according to the operation data of the three-phase AC power grid. The multi-level protection threshold includes the instantaneous overvoltage value and the effective value overvoltage value to form the third-layer overvoltage protection; The start protection unit is used to trigger and start one of the first-layer overvoltage protection, the second-layer overvoltage protection, and the third-layer protection for overvoltage protection according to the input voltage and duration of the three-phase AC power grid.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a stored program. When the program runs, it executes the method according to any one of claims 1 to 7.

10. An electronic device, comprising a memory and a processor, characterized in that, A computer program is stored in the memory, and the processor is configured to execute the method according to any one of claims 1 to 7 through the computer program.

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