A three-level inverter switching frequency control method, device, medium and equipment

Abstract

The application belongs to the technical field of inverter switch control, and specifically discloses a three-level inverter switch frequency control method, device, medium and equipment. The method comprises the following steps: collecting the actual output current of the output end of the three-level inverter in real time; calculating the instantaneous error of the actual output current and the preset reference current; calculating the rising time and the falling time of the instantaneous error within the hysteresis width to obtain a natural switch period; comparing the actual output current of the output end of the three-level inverter with a set threshold to determine whether the three-level inverter enters an active frequency conversion adjustment mode; and when the active frequency conversion adjustment mode is entered, taking the natural switch period as a reference, dynamically setting the turn-on time and the turn-off time to generate a controlled switch period, so that the active adjustment of the switch frequency of the three-level inverter is realized. By adopting the segmented frequency conversion hysteresis control, the application can improve the operation reliability of the three-level inverter and prolong the service life of the power device.

Description

Technical Field

[0001] This application belongs to the field of inverter switching control technology, specifically relating to a method, device, medium, and equipment for controlling the switching frequency of a three-level inverter. Background Technology

[0002] In traditional hysteresis current control methods, the inverter's switching frequency fluctuates continuously with the load and system state, resulting in a complex output current spectrum, difficult filter design, and severe system electromagnetic interference (EMI). At the same time, switching devices (such as insulated gate bipolar transistors (IGBTs)) are prone to overheating and damage due to frequency instability, which seriously affects system reliability and device lifespan. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the purpose of this application is to provide a method, device, medium, and equipment for controlling the switching frequency of a three-level inverter. This application stabilizes the switching frequency of the three-level inverter within a preset range by actively adjusting the switching cycle. This effectively simplifies filter design, reduces electromagnetic interference, and improves system reliability and device lifespan while retaining the fast dynamic response of hysteresis control.

[0004] To achieve the above objectives, this application provides the following technical solution:

[0005] A method for controlling the switching frequency of a three-level inverter includes: real-time acquisition of the actual output current at the output terminal of the three-level inverter; calculation of the instantaneous error between the actual output current and a preset reference current; calculation of the rise time and fall time of the instantaneous error within the hysteresis width to obtain the natural switching cycle; comparison of the actual output current at the output terminal of the three-level inverter with a set threshold to determine whether the three-level inverter has entered an active frequency conversion regulation mode; when the three-level inverter enters the active frequency conversion regulation mode, the on-time and off-time are dynamically set based on the natural switching cycle to generate a controlled switching cycle, thereby realizing the active regulation of the switching frequency of the three-level inverter.

[0006] Optionally, the calculation of the rise time and fall time of the instantaneous error within the hysteresis width to obtain the natural switching period includes: calculating the ideal terminal voltage of the three-level inverter matched with the reference current based on the reference current; calculating the rise time and fall time of the instantaneous error within the hysteresis width based on the ideal terminal voltage; and calculating the natural switching period based on the rise time and fall time of the instantaneous error within the hysteresis width.

[0007] Optionally, the ideal terminal voltage is calculated based on the following formula:

[0008]

[0009] in, Indicates the ideal terminal voltage; Indicates the value of the filter inductance; Indicates reference current Over time The rate of change; This represents a differential operator.

[0010] Optionally, the rise time and fall time of the instantaneous error within the hysteresis width are calculated based on the following formulas:

[0011]

[0012]

[0013] in, This represents the output voltage of the three-level inverter when the output is at a high level. This indicates the output voltage of the three-level inverter when the output is low. Indicates the ideal terminal voltage; Indicates the value of the filter inductance; Indicates instantaneous error;

[0014] The natural switching period is calculated based on the following formula:

[0015]

[0016] in, Indicates the natural switching period; This represents the rise time of the instantaneous error within the hysteresis width. This indicates the descent time of the instantaneous error within the hysteresis width.

[0017] Optionally, comparing the actual output current at the output terminal of the three-level inverter with a set threshold to determine whether the three-level inverter has entered the active frequency conversion regulation mode includes: if the actual output current at the output terminal of the three-level inverter is greater than the set threshold, then the three-level inverter is determined to have entered the active frequency conversion regulation mode.

[0018] Optionally, the turn-on time and turn-off time are calculated through the following steps: determining the target switching frequency for the next switching cycle based on a preset target frequency range; calculating the frequency error between the target switching frequency and the actual switching frequency; calculating the reference switching cycle based on the natural switching cycle; calculating the total adjustment amount for the reference switching cycle through a closed-loop regulator based on the frequency error; calculating the target switching cycle based on the reference switching cycle and the total adjustment amount; and allocating the target switching cycle to the turn-on time and turn-off time.

[0019] Optionally, after calculating the activation and deactivation times, the method further includes: correcting the activation and deactivation times.

[0020] This application also provides a three-level inverter switching frequency control device, the device comprising: a data acquisition module for real-time acquisition of the actual output current at the output terminal of the three-level inverter; a first calculation module for calculating the instantaneous error between the actual output current and a preset reference current; a second calculation module for calculating the rise time and fall time of the instantaneous error within the hysteresis width to obtain the natural switching cycle; a determination module for comparing the actual output current at the output terminal of the three-level inverter with a set threshold to determine whether the three-level inverter has entered the active frequency conversion regulation mode; and an adjustment module for, when entering the active frequency conversion regulation mode, dynamically setting the turn-on time and turn-off time based on the natural switching cycle to generate a controlled switching cycle, thereby realizing the active adjustment of the switching frequency of the three-level inverter.

[0021] This application also provides a storage medium including instructions that, when executed on a computer, cause the computer to perform the three-level inverter switching frequency control method as described in any of the preceding claims.

[0022] This application also provides an electronic device, the electronic device comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the program, implements the three-level inverter switching frequency control method as described in any of the preceding claims.

[0023] Compared with the prior art, the beneficial effects of this application are as follows:

[0024] This application employs segmented frequency conversion hysteresis control, which effectively limits the switching frequency of the three-level inverter within a predetermined range. This not only simplifies the design of the output filter and reduces electromagnetic interference, but also prevents over-temperature faults in power devices such as IGBTs caused by frequent switching and current spikes by avoiding unstable states due to excessively high or low switching frequencies. As a result, the operational reliability of the three-level inverter is improved, the service life of the power devices is extended, and the system maintains good dynamic response performance. Attached Figure Description

[0025] Figure 1 This is a schematic flowchart of a three-level inverter switching frequency control method provided in one embodiment of this application;

[0026] Figure 2 This is a schematic diagram of the current waveform during a standard switching cycle provided in another embodiment of this application;

[0027] Figure 3This is a schematic diagram of a current waveform for reducing the current spike during turn-on time, provided in another embodiment of this application.

[0028] Figure 4 This is a schematic diagram of the current waveform for increasing the turn-on time and reducing the switching frequency provided in another embodiment of this application;

[0029] Figure 5 This is a schematic diagram of a current waveform for reducing turn-off time and increasing switching frequency provided in another embodiment of this application;

[0030] Figure 6 This is a schematic diagram of the current waveform for increasing the turn-off time and reducing the switching frequency provided in another embodiment of this application;

[0031] Figure 7 This is a schematic diagram of a current waveform that simultaneously reduces turn-on and turn-off times and increases switching frequency, provided in another embodiment of this application.

[0032] Figure 8 This is a schematic diagram of a current waveform provided in another embodiment of this application, which simultaneously increases the turn-on and turn-off times and reduces the switching frequency;

[0033] Figure 9 This is a schematic diagram of the structure of a three-level inverter switching frequency control device provided in another embodiment of this application. Detailed Implementation

[0034] The following will refer to the appendices in the embodiments of this application. Figure 1 To be continued Figure 9 The technical solutions in the embodiments of this application are clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0035] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0036] In this application, unless otherwise expressly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0037] Furthermore, if the embodiments of this application involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed in this application.

[0038] Figure 1 This is a flowchart illustrating a switching frequency control method for a three-level inverter according to an embodiment of this application, as shown below. Figure 1 As shown, the method includes the following steps:

[0039] S100: Real-time acquisition of the actual output current at the output terminal of the three-level inverter. i ;

[0040] S200: Calculate the actual output current i With the preset reference current instantaneous error ,Right now ;

[0041] In this step, the reference current As the command input for the entire control system, it is the desired current waveform pre-calculated by the outer loop controller (such as the harmonic detection loop of an active power filter, the power loop of a photovoltaic grid connection, or the torque loop of a motor drive) based on the functional objectives of the three-level inverter (such as harmonic compensation and outputting specified power). The objective of this application is to drive the power switch of the three-level inverter to operate using the proposed segmented frequency conversion hysteresis method, thereby enabling the actual output current... i It can follow the given reference current in real time and with high precision. At the same time, the switching frequency is dynamically adjusted to solve the frequency fluctuation problem of traditional hysteresis control, thereby improving tracking performance and system reliability.

[0042] S300: Calculate instantaneous error The natural switching period is obtained by measuring the rise and fall times within the hysteresis width. Specifically, it includes:

[0043] First, based on the reference current and circuit parameters (such as filter inductor) L Calculate the reference current Ideal terminal voltage of a matched three-level inverter The specific calculations are as follows:

[0044]

[0045] in, Indicates the value of the filter inductance; Indicates reference current Over time The rate of change of current; This represents a differential operator.

[0046] Secondly, based on ideal terminal voltage Calculate the instantaneous error Within the hysteresis width, it rises from the lower limit to the upper limit (from...). arrive ) required rise time And from the upper limit to the lower limit (from) arrive ) required descent time .

[0047] Among them, the rise time of the instantaneous error within the hysteresis width The calculation is performed using the following formula:

[0048]

[0049] The fall time of the instantaneous error within the hysteresis width The calculation is performed using the following formula:

[0050]

[0051] in, This indicates the output voltage of the three-level inverter when the output is at a high level. This indicates the output voltage of the three-level inverter when the output is at a low level.

[0052] Finally, based on the rise time of the instantaneous error within the hysteresis width... and descent time Calculate the natural switching period :

[0053]

[0054] S400: The actual output current at the output terminal of the three-level inverter With set threshold A comparison is performed to determine whether the three-level inverter has entered the active frequency conversion regulation mode;

[0055] In this step, if If the three-level inverter operates according to traditional hysteresis control, the switch of the three-level inverter will immediately switch the output level state when the error touches the hysteresis boundary in order to achieve current tracking;

[0056] if Then it enters the next stage of active frequency conversion adjustment mode.

[0057] S500: When the three-level inverter enters the active frequency conversion regulation mode, it dynamically sets the turn-on time and turn-off time based on the natural switching cycle to generate a controlled switching cycle and realize the active regulation of the switching frequency of the three-level inverter.

[0058] In this step, under active frequency conversion regulation mode, the controller dynamically calculates the switch-on time through a closed-loop regulator based on the deviation between the current switching frequency and the target frequency. and shutdown time And based on the natural switching cycle, it is allocated to generate a controlled switching cycle, i.e. And by changing the switching cycle T This allows for direct control of the switching frequency.

[0059] It should be noted that the opening time... and shutdown time The calculation is performed using the following steps:

[0060] Step 1: Based on the system's preset frequency target range [ , Based on the current operating status of the three-level inverter (such as temperature, load current, modulation ratio, etc.), determine the target switching frequency for the next switching cycle. Among them, if the actual switching frequency of the switch Below Then let If the actual switching frequency of the switch Higher than Then let .

[0061] Step 2: Calculate the target switching frequency based on the following formula With actual switching frequency frequency error :

[0062]

[0063] Where k represents the current control cycle.

[0064] Step 3: Based on natural switching cycles Calculate the reference switching period :

[0065] Specifically, this step is based on the current natural switching cycle. Based on the previous natural switching cycle, The reference switching cycle of the current control cycle is calculated through weighted smoothing. :

[0066]

[0067] in, represents the weighting coefficient, and k represents the current control period.

[0068] Step 4: Based on frequency error The reference switching cycle is calculated through the closed-loop regulator. Total adjustment :

[0069]

[0070] in, Indicates the sampling period; Indicates proportional gain; Indicates integral gain; Indicates frequency error; n represents the discrete-time index; j represents the cyclic index variable in the summation symbol ∑.

[0071] Step 5: Based on the reference switching period Total Adjustment Calculate the target switching period :

[0072]

[0073] Step 6: Set the target switching cycle Assigned to activation time and shutdown time ,in,

[0074] Opening time Represented as:

[0075] .

[0076] Shutdown time Represented as:

[0077]

[0078] Furthermore, to more accurately track changes in the reference current, this embodiment introduces a reference current-based... rate of change of current Correction coefficient Regarding the opening time and shutdown time Make corrections, the correction factor It is expressed as follows:

[0079]

[0080] in, This indicates that the gain is adjusted.

[0081] The revised opening time and shutdown time They are represented as follows:

[0082]

[0083]

[0084] It should be noted that in traditional hysteresis control, if the turn-on and turn-off times are determined solely by whether the instantaneous error reaches the hysteresis boundary, the switching frequency will fluctuate drastically with the load and system parameters, leading to uneven switching losses, increased electromagnetic interference, and complex filter design. This application introduces a correction mechanism based on the rate of change of current to dynamically adjust the ratio of turn-on to turn-off times. This allows the switching cycle to not only follow the system's natural response trend but also to adjust the switching time in advance when the reference current changes rapidly. This maintains current tracking accuracy while stabilizing the switching frequency within a preset range, effectively suppressing frequency drift, reducing switching losses and temperature rise, and improving the system's dynamic response and operational reliability.

[0085] Furthermore, the controller will adjust the activation time accordingly. and shutdown time A corresponding PWM drive signal is generated, forcing the three-level inverter's switches to complete the entire turn-on and turn-off times before switching states. At this point, even with instantaneous errors... Even if the hysteresis boundary is reached prematurely, the switch state will not change immediately; instead, it will wait for the set activation time. and shutdown time This allows for the breaking of the instantaneous response mode of traditional hysteresis control, where the error is triggered immediately, and enables direct and active control of the switching cycle.

[0086] Furthermore, the system continuously monitors the actual switching frequency. ,Will With the target range (such as [ , The error frequency is obtained by comparing the values ​​of the two components. Then, this error frequency is processed by a closed-loop controller (such as a PI controller), and the on-time in the next switching cycle is dynamically adjusted accordingly. and shutdown time The switching frequency of the three-level inverter Adjustments are made. This closed-loop feedback adjustment ensures the switching frequency of the three-level inverter is maintained. It is stably constrained within a preset target range, thus effectively solving the problem of inconsistent switching frequency in traditional hysteresis control while maintaining good current tracking performance.

[0087] Figure 2 This is a schematic diagram of the current waveform during a standard switching cycle provided in one embodiment of this application. The diagram defines the reference switching cycle of the control method of this application and specifically depicts a complete switching cycle. T Internal current Over time The changing waveform, in which the period From the opening time (interval [ ]) and shutdown time (interval [ Composed of [ ]). During the opening time During this period, the three-level inverter outputs a high level, and the current increases linearly; during the off-time... During this period, the three-level inverter outputs a low level (or negative level), and the current decreases linearly. The peak and trough values ​​of the current are determined by the hysteresis width. Therefore, this diagram can serve as a reference benchmark for all adjustment actions in the entire segmented frequency converter control strategy.

[0088] Figure 3 This is a schematic diagram of a current waveform for reducing the current spike during turn-on time according to an embodiment of this application. The diagram shows the current waveform during the turn-off time. Under the premise of keeping everything unchanged, only the opening time is reduced. The regulatory effect. (Compared to) Figure 2 compared to, Figure 3 Opening time (interval [ Shorten the shutdown time (interval [ The current remains unchanged, but the rise rate during the turn-on phase remains the same, although the rise time is reduced, resulting in a significant reduction in the peak current. This mode is used to suppress excessively high current spikes that may occur due to sudden load changes or rapid changes in the reference current, thereby preventing overcurrent faults and reducing current stress on power devices such as IGBTs, thus protecting the devices.

[0089] Figure 4 This is a schematic diagram of the current waveform provided in one embodiment of this application, illustrating the effect of increasing the turn-on time and reducing the switching frequency. The diagram shows the current waveform during the hold-off time. Under the premise of not changing, increase the opening time. The regulatory effect. For example Figure 4 As shown, opening time The lengthening process increases the duration of the current rise. Furthermore, due to the turn-off time... Fixed, throughout the entire switching cycle Therefore, increasing the switching frequency leads to... The switching frequency is reduced. This mode aims to correct the problem of "too short turn-on pulse" that occurs in traditional hysteresis control under certain operating conditions. By actively extending the turn-on time, the switching frequency is reduced, thereby reducing switching losses and device heat generation, and improving system reliability.

[0090] Figure 5 This is a schematic diagram of a current waveform provided in one embodiment of this application to reduce the turn-off time and increase the switching frequency. The diagram shows the current waveform during the hold-on time. Reduce shutdown time while keeping the current settings unchanged. The adjustment effect. Off time. Time interval [ The time is shortened, the current decrease process is accelerated, and due to the turn-on time Fixed, throughout the entire switching cycle Therefore, the frequency is reduced, resulting in a decrease in the switching frequency. Increase. This mode aims to address the problem of excessively low switching frequency caused by "excessive off-time" by reducing the off-time. It can increase the switching frequency. This optimizes current tracking accuracy and suppresses ripple.

[0091] Figure 6 This is a schematic diagram of the current waveform provided in one embodiment of this application, illustrating the effect of increasing the turn-off time and reducing the switching frequency. The diagram shows the current waveform during the hold-on time. Increase the shutdown time while keeping the current settings unchanged. The regulatory effect. For example Figure 6 As shown, shutdown time Time interval [ The current is stretched, increasing the duration of the current drop process. This leads to a longer switching cycle. Increase the switching frequency Reduce. This mode is used to correct the "too short turn-off pulse" condition, preventing excessively high switching frequencies due to insufficient turn-off time. This is achieved by increasing the turn-off time. This can effectively reduce switching losses and electromagnetic interference, and extend device life.

[0092] Figure 7 This is a schematic diagram of a current waveform provided in one embodiment of the present application, illustrating the simultaneous reduction of turn-on and turn-off times to increase switching frequency. and shutdown time The regulatory effect. (Compared to) Figure 2 compared to, Figure 7 Opening time Time interval [ and shutdown time Time interval [ Both intervals are compressed. This makes the "sawtooth" pattern of current rise and fall more dense, within a single switching cycle. Significantly shortens the time, thereby significantly increasing the switching frequency. This mode is applied to operating conditions where the system requires a fast response or where "long on and long off" conditions result in an overall low frequency. It improves dynamic performance and current tracking by increasing the frequency.

[0093] Figure 8 This is a schematic diagram of the current waveform provided in one embodiment of the present application, illustrating the reduction of switching frequency by simultaneously increasing the turn-on and turn-off times. and shutdown time The adjustment effect. In this figure, the opening time... and shutdown time All of these are extended, and the current change waveform is "widened." This results in the switching cycle... Significantly increased switching frequency Significantly reduced. This mode is designed to address the problem of abnormally high switching frequencies caused by "short turn-on, short turn-off". By extending the overall switching cycle, switching losses and temperature rise can be significantly reduced, thereby protecting power devices from overheating damage.

[0094] In conclusion, Figures 2 to 8 The paper provides an exemplary description of "segmented frequency conversion hysteresis control," visually demonstrating how to control the turn-on time. and shutdown time The independent or combined adjustment of these two key parameters enables precise and flexible control of the switching frequency of the three-level inverter, thereby achieving the comprehensive goals of optimizing performance, suppressing ripple, reducing losses, and protecting devices.

[0095] In another exemplary embodiment, such as Figure 9 As shown, this application also provides a three-level inverter switching frequency control device, the device comprising: a data acquisition module 100 for real-time acquisition of the actual output current at the output terminal of the three-level inverter; a first calculation module 200 for calculating the instantaneous error between the actual output current and a preset reference current; a second calculation module 300 for calculating the rise time and fall time of the instantaneous error within the hysteresis width to obtain the natural switching cycle; a judgment module 400 for comparing the actual output current at the output terminal of the three-level inverter with a set threshold to determine whether the three-level inverter has entered the active frequency conversion regulation mode; and an adjustment module 500 for, when entering the active frequency conversion regulation mode, dynamically setting the turn-on time and turn-off time based on the natural switching cycle to generate a controlled switching cycle, thereby realizing the active adjustment of the switching frequency of the three-level inverter.

[0096] In another exemplary embodiment, this application provides a storage medium including instructions that, when executed on a computer, cause the computer to perform a three-level inverter switching frequency control method as described in any embodiment of this application.

[0097] In another exemplary embodiment, this application also provides an electronic device, the electronic device comprising:

[0098] A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the program, implements a three-level inverter switching frequency control method as described in any embodiment of this application.

[0099] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A method of controlling the switching frequency of a three-level inverter, characterized in that, The method comprises: real-time acquisition of actual output current of the three-level inverter output end; calculation of instantaneous error of the actual output current and preset reference current; calculation of rising time and falling time of the instantaneous error within a hysteresis width to obtain a natural switching period; comparison of the actual output current of the three-level inverter output end with a set threshold to determine whether the three-level inverter enters an active frequency regulation mode; when the three-level inverter enters the active frequency regulation mode, the on-time and off-time are dynamically set based on the natural switching period to generate a controlled switching period, so as to realize active regulation of the switching frequency of the three-level inverter; wherein the on-time and off-time are dynamically set based on the natural switching period to generate the controlled switching period, and the method specifically comprises: based on the current natural switching period and the last natural switching period, the reference switching period of the current control period is calculated through weighted smoothing processing; based on the frequency error, the total adjustment amount of the reference switching period is calculated through a closed-loop regulator; based on the reference switching period and the total adjustment amount, the target switching period is calculated; the target switching period is distributed to the on-time and off-time; a correction coefficient based on the current change rate of the reference current is introduced to correct the on-time and off-time; based on the corrected on-time and off-time, corresponding PWM driving signals are generated, and the switching of the three-level inverter is forced to be completed after the entire on-time and off-time.

2. The three-level inverter switching frequency control method of claim 1, wherein, The calculation of the rising time and falling time of the instantaneous error within the hysteresis width to obtain the natural switching period comprises: calculation of an ideal terminal voltage of the three-level inverter matched with the reference current based on the reference current; calculation of the rising time and falling time of the instantaneous error within the hysteresis width based on the ideal terminal voltage; calculation of the natural switching period based on the rising time and falling time of the instantaneous error within the hysteresis width.

3. The three-level inverter switching frequency control method of claim 2, wherein, The ideal terminal voltage is calculated based on the following formula: wherein, represents an ideal terminal voltage; represents a filter inductance value; represents a reference current represents a rate of change over time represents a rate of change over time represents a differential operator.

4. The three-level inverter switching frequency control method of claim 2, wherein, The rising time and falling time of the instantaneous error within the hysteresis width are calculated based on the following formulas respectively: wherein, VH represents an output voltage when the three-level inverter output is high, VL represents an output voltage when the three-level inverter output is low; Videal represents an ideal terminal voltage; L represents a filter inductance value; e represents a transient error; The natural switching period is calculated based on the following formula: wherein, represents the natural switching period; represents the rise time of the transient error within the hysteresis width, represents the fall time of the transient error within the hysteresis width.

5. The three-level inverter switching frequency control method of claim 1, wherein, The comparison of the actual output current of the three-level inverter output end with the set threshold to determine whether the three-level inverter enters the active frequency regulation mode comprises: if the actual output current of the three-level inverter output end is greater than the set threshold, it is determined that the three-level inverter enters the active frequency regulation mode.

6. The three-level inverter switching frequency control method of claim 1, wherein, The on-time and off-time are calculated through the following steps: determination of the target switching frequency of the next switching period based on a preset frequency target range; calculation of the frequency error of the target switching frequency and the actual switching frequency; calculation of the reference switching period based on the natural switching period; calculation of the total adjustment amount of the reference switching period through a closed-loop regulator based on the frequency error; calculation of the target switching period based on the reference switching period and the total adjustment amount; distribution of the target switching period to the on-time and off-time.

7. The three-level inverter switching frequency control method of claim 6, wherein, After the on-time and off-time are calculated, the method further comprises: correction of the on-time and off-time.

8. A three-level inverter switching frequency control device for implementing the three-level inverter switching frequency control method according to claim 1, characterized by, The device comprises: an acquisition module configured to acquire actual output current of a three-level inverter output end in real time; The first calculation module is configured to calculate an instantaneous error between the actual output current and a preset reference current; The second calculation module is configured to calculate a rising time and a falling time of the instantaneous error within a hysteresis width to obtain a natural switching period; The determination module is configured to compare the actual output current of the three-level inverter output end with a set threshold to determine whether the three-level inverter enters an active frequency conversion adjustment mode; The adjustment module is configured to, when the three-level inverter enters the active frequency conversion adjustment mode, dynamically set the turn-on time and the turn-off time based on the natural switching period to generate a controlled switching period, so as to realize active adjustment of the switching frequency of the three-level inverter.

9. A storage medium, characterized by The computer program comprises instructions which, when executed on a computer, cause the computer to perform the three-level inverter switching frequency control method according to any one of claims 1-7.

10. An electronic device, comprising: The electronic device comprises: a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the three-level inverter switching frequency control method according to any one of claims 1-7.

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