Switching frequency control method and device and electronic equipment

Abstract

The invention provides a switching frequency control method and device and electronic equipment, and is applied to a three-phase inverter system comprising an LC filter and a power switch element, and the method comprises the steps: carrying out the sampling of the output current of the power switch element, and obtaining an output current sampling value; performing spectral analysis on the output current sampling value, and extracting a load current component corresponding to the current output frequency of the three-phase inverter system from the output current sampling value; and under the condition that the current output frequency does not reach the preset set output frequency, adjusting the switching frequency of the power switching element according to the load current component and the output current sampling value. Therefore, in the dynamic adjustment stage when the output frequency does not reach the set value, the switching frequency is adaptively adjusted in real time according to the load current component and the output current sampling value, so that the defect that a fixed switching frequency scheme cannot adapt to the dynamic working condition is overcome; and the control robustness and the anti-resonance interference capability of the system in the frequency change process are obviously improved.

Description

Technical Field

[0001] This application belongs to the field of motor inverter technology, and particularly relates to a switching frequency control method, device and electronic equipment. Background Technology

[0002] In high-speed motor inverter systems, inductor-capacitor (LC) filters are often added to the inverter output side to suppress electromagnetic interference caused by high-frequency switching of power devices, reduce the risk of motor insulation failure, and reduce shaft current corrosion. However, the introduction of LC filters can introduce resonant currents, especially in certain topologies. These resonant currents can significantly affect the waveform quality of the output current and even lead to motor runaway, severely restricting the reliability and stability of the system.

[0003] In related technologies, to address the resonant current problem caused by LC filters, the switching frequency of power devices is typically limited to reduce the impact of the resonant current on the system. For example, by setting a fixed, lower switching frequency, the resonant peak region can be avoided, ensuring the basic stable operation of the system.

[0004] However, the single frequency setting cannot adapt to the actual needs of the system under different operating conditions, making it difficult to balance the robustness and overall efficiency of the system when dealing with complex operating conditions, thus limiting the further improvement of system performance. Summary of the Invention

[0005] This application provides a switching frequency control method, apparatus, and electronic device that can prevent motor runaway caused by resonant current and improve the operating efficiency of switching frequency control.

[0006] A first aspect of this application provides a switching frequency control method applied to a three-phase inverter system including an LC filter and power switching elements. The method includes: sampling the output current of the power switching elements to obtain output current sample values; performing spectrum analysis on the output current sample values ​​to extract the load current component corresponding to the current output frequency of the three-phase inverter system from the output current sample values; and adjusting the switching frequency of the power switching elements according to the load current component and the output current sample values ​​when the current output frequency has not reached a preset set output frequency.

[0007] In the technical solution of this application, by dynamically adjusting the switching frequency in real time according to the load current component and the output current sampling value during the dynamic adjustment stage when the output frequency has not reached the set value, the defect of the fixed switching frequency scheme being unable to adapt to dynamic operating conditions is overcome, and the control robustness and anti-resonance interference capability of the system during the frequency change process are significantly improved.

[0008] Optionally, in another possible implementation of the first aspect, adjusting the switching frequency of the power switching element based on the load current component and the output current sample value when the current output frequency has not reached the preset set output frequency includes: determining the real-time ratio of the load current component to the output current sample value when the current output frequency has not reached the set output frequency; and adjusting the switching frequency based on the real-time ratio and a preset first threshold. Thus, by calculating the ratio of the load current component to the total output current in real time during the dynamic adjustment phase, and directly adjusting the switching frequency based on the comparison result of this ratio and the threshold, the influence of the LC filter resonant current on the control loop can be quickly and directly suppressed, effectively preventing the system from losing control during dynamic processes.

[0009] Optionally, in one possible implementation of the first aspect, the method further includes: when the current output frequency reaches a set output frequency, determining a target switching frequency based on a power loss assessment of the power switching element, and switching the switching frequency of the power switching element to the target switching frequency. Thus, by performing online optimization based on power loss assessment to determine and switch to the optimal target switching frequency during the static adjustment phase when the output frequency reaches the set value, the power device losses are minimized and the system operating efficiency is maximized while ensuring system stability.

[0010] Optionally, in another possible implementation of the first aspect, the above-mentioned determination of the target switching frequency based on the power loss assessment of the power switching element when the current output frequency reaches the set output frequency, and switching the switching frequency of the power switching element to the target switching frequency, includes: increasing the switching frequency to a preset maximum frequency when the current output frequency reaches the set output frequency; performing a loss assessment step when the switching frequency is at the maximum frequency to determine the current power loss value of the power switching element at the maximum frequency; decreasing the switching frequency by a preset step size and repeating the loss assessment step to obtain the current power loss value corresponding to each reduced switching frequency; determining the minimum current power loss value from the current power loss values ​​corresponding to each switching frequency, and determining the switching frequency corresponding to the minimum current power loss value as the target switching frequency. Thus, by first increasing the switching frequency to a preset maximum value during the static adjustment phase, and then gradually decreasing it in a step-by-step manner while simultaneously assessing the power loss at each frequency point, the optimal switching frequency point that minimizes the total power loss can be systematically searched and located, thereby maximizing efficiency under steady-state operation.

[0011] Optionally, in another possible implementation of the first aspect, the aforementioned loss assessment steps include: determining, for a reference switching frequency, a reference output current sample value and a reference load current component corresponding to the reference switching frequency, wherein the reference switching frequency is any switching frequency; determining a reference real-time ratio between the reference load current component and the reference output current sample value; and determining the current power loss value of the power switching element at the reference switching frequency based on the reference real-time ratio and the reference switching frequency. Thus, by calculating the corresponding load current component proportion (i.e., the reference real-time ratio) for each switching frequency to be assessed, and using this proportion along with the switching frequency as the basis for assessing power loss, the combined impact of resonant current variations on device conduction and switching losses at different switching frequencies can be more accurately reflected.

[0012] Optionally, in another possible implementation of the first aspect, determining the current power loss value of the power switching element at the reference switching frequency based on the reference real-time ratio and the reference switching frequency includes: determining the switching loss and conduction loss of the power switching element at the reference switching frequency based on the reference switching frequency and the operating parameters of the power switching element; and determining the sum of the switching loss and conduction loss as the current power loss value. Thus, by specifically calculating the total loss of the power switching element at a specific switching frequency as the sum of its switching loss and conduction loss, a clear and quantifiable calculation basis is provided for loss-based switching frequency optimization, making the process of finding the optimal efficiency point more accurate and reliable.

[0013] Optionally, in another possible implementation of the first aspect, before determining the minimum current power loss value from the current power loss values ​​corresponding to each switching frequency, the method further includes: for a reference switching frequency, determining an estimated junction temperature of the power switching element at the reference switching frequency based on the current power loss value corresponding to the reference switching frequency and the thermal resistance parameter of the power switching element; determining the minimum current power loss value from the current power loss values ​​corresponding to each switching frequency includes: determining the minimum current power loss value as the current power loss value whose estimated junction temperature satisfies a preset temperature condition. Thus, by introducing an estimation of the junction temperature of the power switching element when determining the minimum loss frequency, and using this as a constraint, it is ensured that the selected optimal switching frequency not only reduces system losses but also ensures that the power device operates within a safe temperature range, preventing thermal failure and improving the long-term reliability of the system.

[0014] Optionally, in another possible implementation of the first aspect, the aforementioned spectral analysis of the output current sampling values ​​to extract the load current component corresponding to the current output frequency of the three-phase inverter system includes: performing Fourier analysis on the output current sampling values ​​to extract the current component with the same frequency as the current output frequency, which is then used as the load current component. Therefore, by performing Fourier analysis on the output current sampling values ​​and accurately extracting the current component with the same frequency as the current output frequency as the load current component, the fundamental load current can be effectively separated from harmonics and resonant currents, providing an accurate data basis for subsequent current ratio calculations and state judgments.

[0015] A second aspect of this application provides a switching frequency control device, comprising: The current sampling module is used to sample the output current of the power switching element and obtain the output current sample value.

[0016] The spectrum analysis module is used to perform spectrum analysis on the output current sample values ​​and extract the load current component corresponding to the current output frequency of the three-phase inverter system from the output current sample values.

[0017] The first control module is used to adjust the switching frequency of the power switching element according to the load current component and the output current sampling value when the current output frequency has not reached the preset set output frequency.

[0018] A third aspect of this application provides an electronic device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the switching frequency control method of the first aspect described above.

[0019] A fourth aspect of this application provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the switching frequency control method of the first aspect described above.

[0020] The fifth aspect of this application provides a computer program product that, when run on an electronic device, causes the electronic device to execute the switching frequency control method of the first aspect described above.

[0021] It is understood that the beneficial effects of the second to fifth aspects mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of a three-phase motor inverter with a floating capacitor neutral point provided in an embodiment of this application; Figure 2 This is a schematic diagram of a three-phase motor inverter with DC introduced through a capacitor neutral point, provided in an embodiment of this application. Figure 3 This is a schematic flowchart of a switching frequency control method provided in an embodiment of this application; Figure 4 This is a flowchart illustrating the dynamic adjustment stage provided in an embodiment of this application; Figure 5 This is a flowchart illustrating the static adjustment stage provided in an embodiment of this application; Figure 6 This is a schematic diagram of the structure of a switching frequency control device provided in an embodiment of this application; Figure 7 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application. Detailed Implementation

[0024] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0025] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0026] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0027] As used in this application specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if detected [the described condition or event]" may be interpreted, depending on the context, as meaning "once determined," "in response to determination," "once detected [the described condition or event]," or "in response to detection [the described condition or event]."

[0028] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0029] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0030] It should be understood that the sequence number of each step in this embodiment does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of this application embodiment.

[0031] In related technologies, to address the resonant current problem caused by LC filters, the switching frequency of power devices is typically limited to reduce the impact of resonant current on the system. For example, by setting a fixed, lower switching frequency, the resonant peak region can be avoided, ensuring the basic stable operation of the system. However, using a single frequency setting cannot adapt to the actual needs of the system under different operating conditions. As a result, when dealing with complex operating conditions, it is difficult to balance the robustness and overall efficiency of the system, limiting further improvements in system performance.

[0032] Two types of LC filters for three-phase high-speed motor inverters, such as Figure 1 and Figure 2 As shown, where, Figure 1 A schematic diagram of a three-phase motor inverter with a floating capacitor neutral point is shown. Figure 2 A schematic diagram of a three-phase motor inverter with DC introduced at the capacitor neutral point is shown. According to Kirchhoff's current law, Figure 1Obey the following equation: ; in, This is the sampled value of the inverter's output current. The capacitor current flowing through the filter capacitor, This represents the load current component flowing through the motor.

[0033] Figure 2 Obey the following equation: ; It should be noted that since the inverter's overcurrent protection targets the power switching elements, the current sampling position is set to... From the two formulas above, we can see that the collected output current sampling value... Not the actual load current component Instead, it is superimposed with capacitive current. The result is that when the inductor and capacitor in the filter resonate, problems are likely to occur. > In such cases, the control system will be unable to accurately sense and adjust the actual load current, until the load becomes uncontrollable. Specifically, in... Figure 2 In the topology shown where the capacitor neutral point is introduced on the DC side, because the potential at one end of the capacitor is clamped to the positive or negative voltage of the DC bus, its capacitive current will vary under the same operating conditions. Compare Figure 1 The suspended topology shown is larger, which makes the system more prone to going out of control.

[0034] In view of this, embodiments of this application provide a switching frequency control method, apparatus, and electronic device, applied to a three-phase inverter system including an LC filter and power switching elements. The method first samples the output current of the power switching elements to obtain output current sample values; then, it performs spectral analysis on the output current sample values ​​to extract the load current component corresponding to the current output frequency of the three-phase inverter system; finally, when the current output frequency has not reached a preset set output frequency, the switching frequency of the power switching elements is adjusted according to the load current component and the output current sample value. Thus, by adaptively adjusting the switching frequency in real time based on the load current component and the output current sample value during the dynamic adjustment phase when the output frequency has not reached the set value, the shortcomings of fixed switching frequency schemes in adapting to dynamic operating conditions are overcome, significantly improving the system's control robustness and anti-resonance interference capability during frequency changes.

[0035] To illustrate the technical solution of this application, specific embodiments are described below.

[0036] Reference Figure 3This diagram illustrates a flow chart of a switching frequency control method provided in an embodiment of this application. This switching frequency control method can be executed by a three-phase inverter system or a switching frequency control device, etc. Figure 3 As shown, the switching frequency control method may include the following steps: Step 301: Sample the output current of the power switching element to obtain the output current sample value.

[0037] In this embodiment, the output current sampling operation is the foundation for all subsequent analysis and control. Specifically, the output current sample value... This refers to the real-time current signal directly acquired at the output terminal of the three-phase inverter bridge, i.e., at the emitter or source connection point of the power switching elements, through a current sensor (such as a Hall current sensor or a sampling resistor). The choice of sampling location is crucial because the overcurrent protection of the inverter system directly targets these power switching elements to prevent damage due to excessive current. Therefore, the output current sampling value... It directly reflects the total current flowing through the power switching element.

[0038] It should be noted that you can continue to refer to this. Figure 1 and Figure 2 Output current sampling value It is not directly equal to the actual current consumed by the motor load. Output current sampling value. It contains the load current component. With one or more capacitor currents The synthesized quantity. When the system operates at certain frequencies, causing the LC filter to resonate, the capacitor current... It may increase dramatically, even far exceeding the load current component. At this point, if the control system only uses If current regulation is used as feedback, the feedback signal will be severely distorted, making it impossible to effectively control the actual load current component. This could ultimately lead to motor malfunction. The subsequent spectrum analysis and adaptive frequency modulation strategy in the embodiments of this application are precisely aimed at synthesizing this... Accurately separated from And eliminate accordingly The adverse effects it brings.

[0039] In the embodiments of this application, the power switching elements are typically organized into a three-phase half-bridge or full-bridge topology. Therefore, output current sampling is usually performed on all three phases to obtain the three-phase output current sample values. The sampling process needs to ensure sufficient bandwidth and accuracy to accurately capture the current waveform containing switching frequency harmonic components, providing a reliable data foundation for subsequent spectrum analysis.

[0040] Step 302: Perform spectrum analysis on the output current sample value and extract the load current component corresponding to the current output frequency of the three-phase inverter system from the output current sample value.

[0041] In this embodiment of the application, the purpose of step 302 is to synthesize a material containing resonant current interference. In this process, the fundamental current component, which reflects the actual load condition of the motor, is precisely separated, i.e., the load current component. The current output frequency refers to the frequency of the fundamental voltage currently output by the three-phase inverter, which directly corresponds to the real-time operating speed (synchronous speed) of the motor. Since the effective torque generated by the motor is only related to the component of the current that is in phase and has the same frequency as this fundamental voltage, accurately obtaining the load current component is crucial. It is a prerequisite for precise control and condition assessment.

[0042] In one embodiment, an efficient and accurate method for achieving spectrum analysis and component extraction is to employ Fourier analysis. Specifically, Fourier analysis of the output current sample values ​​can be performed in real time within a digital controller (such as a digital signal processor or microcontroller) using the Fast Fourier Transform (FFT) algorithm. The controller processes continuously sampled data... The discrete sequence is transformed from the time domain to the frequency domain using FFT, resulting in a spectrum containing the amplitude and phase information of each frequency component. The current component with the same frequency as the current output frequency is extracted as the load current component. In other words, within the calculated spectrum, the spectral line whose frequency coordinates equal the currently known or real-time fundamental output frequency obtained through circuits such as phase-locked loops is found. The complex number (including amplitude and phase) represented by this spectral line is defined. The sinusoidal quantity. Through this frequency domain filtering, it is possible to... From the mixture of switching harmonics and resonant frequency components (manifested as capacitor current) ) and other noise It was cleanly separated from the middle.

[0043] It should be noted that, by utilizing the linearity of the Fourier transform, the time-domain signal is decomposed into a sum of sinusoidal components of different frequencies, from which the component corresponding to the desired frequency is selected. This precise separation is crucial because subsequent calculations, whether for real-time ratios in the dynamic phase or loss assessment in the static phase, rely on an accurate and pure [equation / sample]. The value is used as input. Inaccurate separation will directly lead to misjudgment by the adaptive algorithm. Therefore, by performing Fourier analysis on the output current sample value and accurately extracting the current component with the same frequency as the current output frequency as the load current component, the fundamental load current, harmonic and resonant currents can be effectively separated, providing an accurate data basis for subsequent current ratio calculation and state judgment.

[0044] Furthermore, the implementation of spectrum analysis requires consideration of both real-time performance and accuracy. For example, appropriate sampling window lengths (integrated with the fundamental period to reduce spectral leakage) and window functions (such as the Hanning window) need to be selected. Simultaneously, the current output frequency may be a changing value, especially during dynamic adjustment. Therefore, the spectrum analysis module needs to be closely synchronized with the system's frequency setpoint or observation unit to ensure it can always track and extract the frequency corresponding to the instantaneous output frequency. This dynamic tracking spectrum analysis can adapt to all operating conditions of the motor under variable speed operation, providing continuous and accurate load current information for subsequent adaptive frequency adjustment.

[0045] Step 303: If the current output frequency does not reach the preset output frequency, adjust the switching frequency of the power switching element according to the load current component and the output current sampling value.

[0046] In this embodiment of the application, after successfully extracting the load current component... Then, the core control stage is entered: determining the system's operating phase and executing the corresponding switching frequency adjustment strategy. Specifically, the current output frequency can be continuously monitored and compared with a preset output frequency. Compare. Set the output frequency. This represents the target operating frequency that the motor control system expects to achieve, such as the electrical frequency corresponding to the rated speed. If the current output frequency is less than the set output frequency... If the system is in a dynamic adjustment phase, then the primary control objective is to ensure its dynamic stability and robustness during frequency changes, preventing loss of control due to LC filter resonance. Therefore, it is necessary to ensure that the current output frequency does not reach the preset set output frequency. In this case, the switching frequency of the power switching element is adjusted according to the load current component and the output current sampling value. Therefore, by adaptively adjusting the switching frequency in real time based on the load current component and the output current sampling value during the dynamic adjustment phase when the output frequency has not reached the set value, the shortcomings of the fixed switching frequency scheme in adapting to dynamic operating conditions are overcome, and the control robustness and anti-resonance interference capability of the system during frequency changes are significantly improved.

[0047] In one embodiment, if the current output frequency does not reach a preset output frequency, the real-time ratio of the load current component to the output current sample value can be determined; the switching frequency can then be adjusted based on the real-time ratio and a preset first threshold. Thus, by calculating the ratio of the load current component to the total output current in real time during the dynamic adjustment phase, and directly adjusting the switching frequency based on the comparison between this ratio and the threshold, the influence of the LC filter resonant current on the control loop can be quickly and directly suppressed, effectively preventing the system from losing control during dynamic processes.

[0048] It should be noted that you can refer to, for example Figure 4 The flowchart shown illustrates the dynamic adjustment phase. This adjustment process can be concretized as a closed-loop control algorithm based on real-time current ratios. The core is calculating a key indicator and using it as the criterion: determining the load current component. With output current sampling value The real-time ratio, i.e. This ratio directly reflects the proportion of load current in the total output current, while its reciprocal implies the capacitor current. The degree of impact. Additionally, a first threshold needs to be preset. First threshold This represents the minimum percentage of load current required to maintain the robustness of the control system. It is an empirical value set based on the system's stability margin, typically around 10%. Based on this real-time ratio... With the first threshold The comparison is performed, and a direct frequency adjustment command is executed.

[0049] Specifically, the switching frequency can be increased when the real-time ratio is less than or equal to a first threshold. That is, when When, it means the capacitor current The proportion is too high (may be close to or meet the requirements). > The resonance phenomenon is significant, posing a risk of output current turbulence and motor runaway. In this case, increasing the switching frequency is necessary. It can change the harmonic spectrum of the inverter output voltage, causing the system operating point to deviate from the resonant peak frequency of the LC filter, thereby effectively suppressing the resonant current. The amplitude makes The proportion has rebounded.

[0050] If the real-time ratio exceeds a first threshold, reduce the switching frequency. That is, when... When, it indicates the load current. When the system is in a dominant position and operating in a relatively stable state, the risk of resonance is low. At this point, actively reducing the switching frequency is recommended. It has two advantages: first, it can immediately reduce the switching losses of power switching elements caused by high-frequency switching operations; second, it reserves upward adjustment to cope with the risk of resonance that may recur in the future. The space allows the adjustment process to have a dynamic range.

[0051] Therefore, by calculating the ratio of the load current component to the total output current in real time during the dynamic adjustment phase, and directly adjusting the switching frequency based on the comparison result of this ratio with the threshold, the influence of the LC filter resonant current on the control loop can be suppressed quickly and directly, effectively preventing the system from going out of control during the dynamic process.

[0052] It should be noted that the aforementioned dynamic adjustment mechanism is a rapid, continuous, closed-loop process. For example... Figure 4 As shown, in each sampling, calculation and adjustment Afterwards, the system will immediately return, re-collect the latest output frequency and current information, and re-perform calculations and judgments, thereby achieving [the desired result]. Real-time, adaptive control. This is achieved through real-time current ratio... This application employs a direct adjustment strategy for the core feedback quantity. During dynamic frequency changes (such as motor starting and speed regulation), the switching frequency can be automatically and rapidly maintained near the minimum necessary level to suppress LC resonance. Its primary objective is to maximize the dynamic robustness of the system and prevent runaway, while also considering preliminary optimization of switching losses when conditions permit. This strategy effectively overcomes the shortcomings of fixed switching frequency schemes, which cannot cope with resonance changes during dynamic processes and are prone to instability.

[0053] In one possible implementation, after step 302, the switching frequency control method may further include: step 304, when the current output frequency reaches the set output frequency, determining the target switching frequency based on the power loss assessment of the power switching element, and switching the switching frequency of the power switching element to the target switching frequency.

[0054] In this embodiment of the application, during system operation, when the current output frequency is detected to have reached and stabilized at a preset output frequency... When the system enters the static adjustment phase, the motor has reached the target speed and is operating in a steady state. The control objective shifts from prioritizing dynamic robustness to optimizing system efficiency and reducing total losses while ensuring stability. Therefore, given that the current output frequency has reached the set output frequency, it is necessary to determine the target switching frequency based on a power loss assessment of the power switching components and switch the power switching components to the target switching frequency. Thus, by performing online optimization based on power loss assessment during the static adjustment phase when the output frequency reaches the set value to determine and switch to the optimal target switching frequency, the system achieves both minimum power device losses and maximum system operating efficiency while ensuring system stability.

[0055] In one embodiment, reference can be made to, for example Figure 5 The diagram illustrates the static adjustment phase. This static optimization process can be concretized as a systematic, online algorithm for searching the optimal efficiency point. The algorithm begins its search with a known boundary condition: given that the current output frequency has reached the set output frequency, the switching frequency is increased to the preset maximum frequency. . This is based on the safe operating upper limit determined by hardware design (such as power device switching characteristics, drive circuit capabilities, and electromagnetic compatibility limitations). This initial operation aims to explore from the high-frequency end of the spectrum most favorable for suppressing resonant current. Subsequently, the system enters an iterative search loop, the core of which is to perform a loss assessment step to determine the power switching elements at the current switching frequency (initially...). The corresponding current power loss value To find the point of minimum total loss, the system performs a gradient descent search: the switching frequency is decreased in preset steps (e.g., 1 kHz or 2 kHz each time), and the loss assessment steps are repeated to obtain a series of values ​​from the minimum value. The current power loss value corresponding to each of the gradually decreasing switching frequency points. The search process terminates when a termination condition is met (e.g., load current percentage). Below a certain minimum threshold When the frequency drops to a certain lower limit (indicating an increased risk of resonance), the iteration stops. Finally, the system determines the minimum current power loss value from the current power loss values ​​corresponding to each switching frequency. The switching frequency corresponding to this minimum value is then determined as the target switching frequency. Ultimately, the controller switches the switching frequency of the power switching elements to the target switching frequency. Therefore, by first increasing the switching frequency to a preset maximum value during the static adjustment phase, and then gradually reducing it in a step-by-step manner while simultaneously evaluating the power loss at each frequency point, the optimal switching frequency point that minimizes the total power loss can be systematically searched and located, thereby maximizing efficiency under steady-state operation.

[0056] In one embodiment, the loss assessment step needs to be performed specifically for each reference switching frequency being assessed. First, the system needs to operate stably at the reference switching frequency for a short period to collect the corresponding reference output current sample value, and obtain the reference load current component at that frequency through spectrum analysis. Next, the reference real-time ratio of the reference load current component to the reference output current sample value is determined. This ratio is a key intermediate variable for evaluating the resonance suppression effect and the magnitude of the conduction current at that frequency. Then, based on the reference real-time ratio and the reference switching frequency, the current power loss value of the power switching element at the reference switching frequency is determined. Therefore, by calculating the corresponding load current component proportion (i.e., the reference real-time ratio) for each switching frequency to be assessed, and using this proportion along with the switching frequency as the basis for power loss assessment, the combined impact of resonant current variations on device conduction and switching losses at different switching frequencies can be more accurately reflected.

[0057] Furthermore, based on the reference switching frequency and the operating parameters of the power switching element (such as switching energy and on-state resistance provided in the device datasheet), the switching loss and conduction loss of the power switching element at the reference switching frequency can be determined. The switching loss is typically proportional to the switching frequency and the DC bus voltage; the conduction loss is proportional to the square of the effective value of the current flowing through the device and the on-state resistance. The effective value of the current can be estimated from the current components derived from the reference output current sampling value and the reference real-time ratio. The sum of the switching loss and the conduction loss is determined as the current power loss value. Therefore, by specifically calculating the total loss of the power switching element at a specific switching frequency as the sum of its switching loss and conduction loss, a clear and quantifiable calculation basis is provided for loss-based switching frequency optimization, making the process of finding the optimal efficiency point more accurate and reliable.

[0058] In one embodiment, to ensure that the optimized switching frequency is not only highly efficient but also guarantees the thermal safety of the power devices, a junction temperature constraint is introduced during the search process. Specifically, for a reference switching frequency, the estimated junction temperature of the power switching element at the reference switching frequency is determined based on its corresponding current power loss value and the thermal resistance parameters of the power switching element. This can be estimated in real time using a thermal resistance model. When finally determining the minimum loss point, the following is performed: from the current power loss values ​​corresponding to each switching frequency, the current power loss value with the smallest estimated junction temperature that satisfies the preset temperature condition is determined as the minimum current power loss value. The preset temperature condition is typically not exceeding the maximum allowable junction temperature of the device and leaving a safety margin. Thus, by introducing the estimation of the junction temperature of the power switching element when determining the minimum loss frequency, and using this as a constraint, it is ensured that the selected optimal switching frequency not only reduces system losses but also ensures that the power devices operate within a safe temperature range, preventing thermal failure and improving the long-term reliability of the system.

[0059] In this embodiment, through the above-described systematic loss assessment and online search strategy in the static stage, the optimal switching frequency point that minimizes the total power switching loss can be automatically found during steady-state operation of the motor. This effectively reduces system energy consumption and improves the power density and efficiency of the inverter; on the other hand, because this frequency meets... > The search is conducted under stability constraints, which inherently ensures that the resonant current is suppressed within the allowable range, thus achieving a balance between robustness and high efficiency in steady state.

[0060] The switching frequency control method disclosed in the above embodiments of this application first samples the output current of the power switching element to obtain the output current sample value; then, it performs spectrum analysis on the output current sample value to extract the load current component corresponding to the current output frequency of the three-phase inverter system; next, if the current output frequency has not reached the preset set output frequency, it adjusts the switching frequency of the power switching element according to the load current component and the output current sample value; finally, if the current output frequency has reached the set output frequency, it determines the target switching frequency based on the power loss assessment of the power switching element and switches the switching frequency of the power switching element to the target switching frequency. Thus, by dynamically distinguishing and employing two different adaptive switching frequency adjustment strategies based on whether the inverter output frequency has reached the set value—namely, current-based adjustment in the dynamic adjustment stage and loss assessment-based adjustment in the static adjustment stage—it avoids motor runaway due to resonant current and achieves both optimized operating efficiency and robust system control across the entire operating range.

[0061] See Figure 6The diagram shows a schematic of a switching frequency control device provided in an embodiment of this application. For ease of explanation, only the parts related to the embodiment of this application are shown.

[0062] The switching frequency control device may specifically include the following modules: The current sampling module 601 is used to sample the output current of the power switching element to obtain the output current sampling value.

[0063] The spectrum analysis module 602 is used to perform spectrum analysis on the output current sample value and extract the load current component corresponding to the current output frequency of the three-phase inverter system from the output current sample value.

[0064] The first control module 603 is used to adjust the switching frequency of the power switching element according to the load current component and the output current sampling value when the current output frequency has not reached the preset set output frequency.

[0065] The switching frequency control device disclosed in the above embodiments of this application first samples the output current of the power switching element to obtain the output current sample value; then, it performs spectrum analysis on the output current sample value to extract the load current component corresponding to the current output frequency of the three-phase inverter system; finally, when the current output frequency has not reached the preset set output frequency, it adjusts the switching frequency of the power switching element according to the load current component and the output current sample value. Therefore, by adaptively adjusting the switching frequency in real time according to the load current component and the output current sample value during the dynamic adjustment phase when the output frequency has not reached the set value, the device overcomes the shortcomings of fixed switching frequency schemes that cannot adapt to dynamic operating conditions, significantly improving the system's control robustness and anti-resonance interference capability during frequency changes.

[0066] Furthermore, in one possible implementation of this application embodiment, the first control module 603 may specifically include the following units: The first determining unit is used to determine the real-time ratio of the load current component to the output current sample value when the current output frequency has not reached the preset set output frequency.

[0067] The first adjustment unit is used to adjust the switching frequency according to the real-time ratio and the preset first threshold.

[0068] Therefore, by calculating the ratio of the load current component to the total output current in real time during the dynamic adjustment phase, and directly adjusting the switching frequency based on the comparison result of this ratio with the threshold, the influence of the LC filter resonant current on the control loop can be suppressed quickly and directly, effectively preventing the system from going out of control during the dynamic process.

[0069] Furthermore, in another possible implementation of this application embodiment, the switching frequency control device may further include the following modules: The second control module 604 is used to determine the target switching frequency based on the power loss assessment of the power switching element when the current output frequency reaches the set output frequency, and to switch the switching frequency of the power switching element to the target switching frequency.

[0070] Therefore, by performing online optimization based on power loss assessment during the static adjustment phase when the output frequency reaches the set value, the optimal target switching frequency is determined and switched to, thereby minimizing power device losses and maximizing system operating efficiency while ensuring system stability.

[0071] Furthermore, in another possible implementation of this application embodiment, the second control module 604 may specifically include the following units: The second adjustment unit is used to increase the switching frequency to the preset maximum frequency when the current output frequency reaches the set output frequency.

[0072] The first control unit is used to perform a loss assessment step when the switching frequency is at its highest frequency, in order to determine the current power loss value of the power switching element at the highest frequency.

[0073] The third adjustment unit is used to reduce the switching frequency by a preset step size and repeatedly perform the loss assessment step to obtain the current power loss value corresponding to the reduced switching frequency each time.

[0074] The second determining unit is used to determine the minimum current power loss value from the current power loss values ​​corresponding to each switching frequency, and to determine the switching frequency corresponding to the minimum current power loss value as the target switching frequency.

[0075] Therefore, by first increasing the switching frequency to a preset maximum value during the static adjustment phase, and then gradually reducing it in a step-by-step manner while simultaneously evaluating the power loss at each frequency point, it is possible to systematically search for and locate the optimal switching frequency point that minimizes the total power loss, thereby maximizing efficiency under steady-state operation.

[0076] Furthermore, in another possible implementation of this application embodiment, the third adjustment unit may specifically include the following sub-units: The first determining subunit is used to determine the reference output current sampling value and the reference load current component corresponding to the reference switching frequency, wherein the reference switching frequency is any switching frequency.

[0077] The second determining subunit is used to determine the reference real-time ratio between the reference load current component and the reference output current sample value.

[0078] The third determining subunit is used to determine the current power loss value of the power switching element at the reference switching frequency based on the reference real-time ratio and the reference switching frequency.

[0079] Therefore, by calculating the corresponding load current component ratio (i.e., the reference real-time ratio) for each switching frequency to be evaluated, and using this ratio together with the switching frequency as the basis for evaluating power loss, it is possible to more accurately reflect the combined impact of resonant current variation on device conduction and switching losses at different switching frequencies.

[0080] Furthermore, in another possible implementation of the embodiments of this application, the third determining subunit may be used to: determine the switching loss and conduction loss of the power switching element at the reference switching frequency based on the reference switching frequency and the operating parameters of the power switching element; and determine the sum of the switching loss and conduction loss as the current power loss value.

[0081] Therefore, by specifically calculating the total loss of power switching elements at a specific switching frequency as the sum of their switching loss and conduction loss, a clear and quantifiable calculation basis is provided for loss-based switching frequency optimization, making the process of finding the optimal efficiency point more accurate and reliable.

[0082] Furthermore, in another possible implementation of this application embodiment, the above-mentioned switching frequency control device may further include the following modules: The junction temperature estimation module is used to determine the estimated junction temperature of the power switching element at the reference switching frequency based on the current power loss value and the thermal resistance parameter of the power switching element at the reference switching frequency.

[0083] Correspondingly, the second determining unit may specifically include the following sub-units: The fourth determining subunit is used to determine the minimum current power loss value from the current power loss values ​​corresponding to each switching frequency, which has the lowest estimated junction temperature value that meets the preset temperature condition.

[0084] Therefore, by estimating the junction temperature of the power switching element when determining the minimum loss frequency, and using this as a constraint, it is ensured that the selected optimal switching frequency not only reduces system losses, but also ensures that the power device operates within a safe temperature range, preventing thermal failure and improving the long-term reliability of the system.

[0085] Furthermore, in another possible implementation of this application embodiment, the spectrum analysis module 602 may specifically include the following units: The analysis and extraction unit is used to perform Fourier analysis on the output current sample value and extract the current component with the same frequency as the current output frequency as the load current component.

[0086] Therefore, by performing Fourier analysis on the output current sampling value and accurately extracting the current component with the same frequency as the current output frequency as the load current component, the fundamental load current and harmonic and resonant currents can be effectively separated, providing an accurate data basis for subsequent current ratio calculation and state judgment.

[0087] The switching frequency control device provided in this application embodiment can be applied in the foregoing method embodiment. For details, please refer to the description of the above method embodiment, which will not be repeated here.

[0088] Figure 7 This is a schematic diagram of the structure of the electronic device provided in an embodiment of this application. For example... Figure 7 As shown, the electronic device 700 of this embodiment includes: at least one processor 710 ( Figure 7 The diagram shows only one processor, a memory 720, and a computer program 721 stored in the memory 720 and executable on the at least one processor 710. When the processor 710 executes the computer program 721, it implements the steps in the above-described embodiments of the switching frequency control method.

[0089] The electronic device 700 can be a desktop computer, laptop, handheld computer, cloud server, or other computing device. This electronic device may include, but is not limited to, a processor 710 and a memory 720. Those skilled in the art will understand that... Figure 7 This is merely an example of electronic device 700 and does not constitute a limitation on electronic device 700. It may include more or fewer components than shown, or combine certain components, or different components. For example, it may also include input / output devices, network access devices, etc.

[0090] The processor 710 may be a Central Processing Unit (CPU), or it may be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0091] In some embodiments, the memory 720 may be an internal storage unit of the electronic device 700, such as a hard disk or memory of the electronic device 700. In other embodiments, the memory 720 may be an external storage device of the electronic device 700, such as a plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, etc., equipped on the electronic device 700. Furthermore, the memory 720 may include both internal and external storage units of the electronic device 700. The memory 720 is used to store the operating system, applications, boot loader, data, and other programs, such as the program code of the computer program. The memory 720 can also be used to temporarily store data that has been output or will be output.

[0092] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0093] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0094] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0095] In the embodiments provided in this application, it should be understood that the disclosed devices / electronic devices and methods can be implemented in other ways. For example, the device / electronic device embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual couplings or direct couplings or communication connections may be through some interfaces; indirect couplings or communication connections between devices or units may be electrical, mechanical, or other forms.

[0096] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0097] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0098] If the integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. It should be noted that the content included in the computer-readable medium can be appropriately added or removed according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electrical carrier signals and telecommunication signals.

[0099] The implementation of all or part of the processes in the methods of the above embodiments can also be accomplished by a computer program product. When the computer program product is run on an electronic device, the electronic device can implement the steps in the various method embodiments described above.

[0100] The embodiments described above are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A switching frequency control method, characterized by, The method, applied to a three-phase inverter system including an LC filter and power switching elements, comprises: The output current of the power switching element is sampled to obtain the output current sample value; Perform spectrum analysis on the output current sample value, and extract the load current component corresponding to the current output frequency of the three-phase inverter system from the output current sample value; If the current output frequency does not reach the preset output frequency, the switching frequency of the power switching element is adjusted according to the load current component and the output current sampling value.

2. The method according to claim 1, characterized in that, When the current output frequency does not reach the preset output frequency, adjusting the switching frequency of the power switching element according to the load current component and the output current sampling value includes: If the current output frequency does not reach the set output frequency, determine the real-time ratio of the load current component to the output current sample value; The switching frequency is adjusted based on the real-time ratio and a preset first threshold.

3. The method of claim 1, wherein, The method further includes: When the current output frequency reaches the set output frequency, a target switching frequency is determined based on the power loss assessment of the power switching element, and the switching frequency of the power switching element is switched to the target switching frequency.

4. The method of claim 3, wherein, When the current output frequency reaches the set output frequency, determining a target switching frequency based on a power loss assessment of the power switching element, and switching the switching frequency of the power switching element to the target switching frequency, includes: If the current output frequency reaches the set output frequency, the switching frequency is increased to the preset maximum frequency; When the switching frequency is the highest frequency, a loss assessment step is performed to determine the current power loss value of the power switching element at the highest frequency. The switching frequency is reduced by a preset step size, and the loss assessment step is repeated to obtain the current power loss value corresponding to the reduced switching frequency each time. From the current power loss values ​​corresponding to each switching frequency, determine the minimum current power loss value, and determine the switching frequency corresponding to the minimum current power loss value as the target switching frequency.

5. The method of claim 4, wherein, The loss assessment steps include: For a reference switching frequency, determine the reference output current sampling value and the reference load current component corresponding to the reference switching frequency, wherein the reference switching frequency is any switching frequency; Determine the reference real-time ratio of the reference load current component to the reference output current sample value; Based on the reference real-time ratio and the reference switching frequency, the current power loss value of the power switching element at the reference switching frequency is determined.

6. The method of claim 5, wherein, The step of determining the current power loss value of the power switching element at the reference switching frequency based on the reference real-time ratio and the reference switching frequency includes: Based on the reference switching frequency and the operating parameters of the power switching element, determine the switching loss and conduction loss of the power switching element at the reference switching frequency; The sum of the switching loss and the conduction loss is determined as the current power loss value.

7. The method of claim 4, wherein, Before determining the minimum current power loss value from the current power loss values ​​corresponding to each switching frequency, the method further includes: For a reference switching frequency, the estimated junction temperature of the power switching element at the reference switching frequency is determined based on the current power loss value corresponding to the reference switching frequency and the thermal resistance parameter of the power switching element. Determining the minimum current power loss value from the current power loss values ​​corresponding to each switching frequency includes: From the current power loss values ​​corresponding to each switching frequency, the current power loss value that satisfies the preset temperature condition and is the smallest is determined as the minimum current power loss value.

8. The method of claim 1, wherein, The step of performing spectral analysis on the output current sample values ​​and extracting the load current component corresponding to the current output frequency of the three-phase inverter system from the output current sample values ​​includes: Fourier analysis is performed on the output current sample value to extract the current component with the same frequency as the current output frequency, which is then used as the load current component.

9. A switching frequency control device, characterized by comprising: The device, applicable to a three-phase inverter system including an LC filter and power switching elements, comprises: The current sampling module is used to sample the output current of the power switching element to obtain the output current sample value; The spectrum analysis module is used to perform spectrum analysis on the output current sampling value and extract the load current component corresponding to the current output frequency of the three-phase inverter system from the output current sampling value, wherein the current output frequency is the frequency of the fundamental voltage currently output by the three-phase inverter. The first control module is used to adjust the switching frequency of the power switching element according to the load current component and the output current sampling value when the current output frequency does not reach the preset set output frequency.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method as described in any one of claims 1 to 8.

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