An inductance-sense-adaptive inverter triangular current modulation method

Abstract

The application provides an inductance adaptive inverter triangular current modulation method, which first performs inductance design and obtains a reference inductance curve, dynamically selects a modulation path by judging whether frequency correction is needed for a current working condition, generates a target variable frequency track based on an ideal inductance if correction is not needed, generates a corrected variable frequency track by substituting an actual inductance obtained according to the actual working condition into a switching frequency formula if correction is needed, and finally outputs the target or corrected variable frequency track as a TCM signal to drive a power conversion circuit. The application overcomes problems such as a wide variable frequency range, low current precision and large loss caused by a fixed inductance in a traditional TCM scheme, optimizes output current precision by real-time correction of the switching frequency, reduces conduction loss, allows the use of a smaller inductance, and improves the overall performance and power density of the inverter.

Description

Technical Field

[0001] This invention belongs to the field of power electronic converter technology and relates to a novel triangular current modulation strategy (TCM) suitable for inverters, specifically a triangular current modulation method for inverters based on inductance adaptiveness. Background Technology

[0002] Traditional full-bridge inverter topologies such as Figure 1 As shown, U in This is the input voltage. Figure 2 This illustrates the basic working principle of TCM modulation used in existing full-bridge inverter topologies. Qualitatively, the TCM modulation strategy uses a large current ripple to enable the switching transistor to turn on when the inductor current drops to a negative current, achieving zero-voltage turn-on and reducing system switching losses. Since the switching timing is determined by the current zero-crossing condition, the system switching frequency of this modulation strategy exhibits a wide range of variable characteristics depending on the load and input voltage.

[0003] Traditional TCM modulation schemes typically assume a constant inductance value and calculate the frequency variation curve required for zero-voltage turn-on based on this fixed inductance, which limits their effectiveness. The frequency curve calculated using a fixed inductance for soft switching has a large range of variation, while the actual inductance varies with the output current. This results in a suboptimal frequency curve calculated using a fixed inductance, affecting output current accuracy. Secondly, inverters often use high-frequency inductors made of ferrite materials, which are prone to core saturation under high current conditions. To suppress saturation, the core cross-sectional area or air gap is often increased, leading to a larger inductor size. Simultaneously, the large current ripple introduced by TCM significantly increases system conduction losses, impacting overall efficiency. Therefore, it is necessary to further improve existing TCM modulation strategies, optimize output current flow, reduce the size of magnetic components, and lower overall losses.

[0004] To address the above problems, this invention proposes an inverter triangular current modulation method based on adaptive inductance. Summary of the Invention

[0005] The purpose of this invention is to address the limitations of existing technologies by proposing a triangular current modulation method for inverters based on adaptive inductance.

[0006] The present invention adopts the following technical solution: An inverter triangular current modulation method based on inductance adaptive modulation includes the following steps: S1: Inductor Design and Initial Curve Acquisition: Perform inductor design for the circuit topology; based on the inductor design, acquire the curve data of the inductance of the inductor as a function of power, and record it as the reference inductor curve; S2: Frequency correction judgment: Determine whether frequency correction is required for the current operation; if not, proceed to step S3; if yes, proceed to step S21. S21: Inductance Update and Trajectory Correction: Update the reference inductance curve with actual inductance based on actual operating parameters to obtain updated inductance characteristic data; Based on the updated inductance characteristic data, correct the current frequency converter trajectory to obtain a corrected frequency converter trajectory. S3: Frequency Conversion Trajectory Generation: Generate the target frequency conversion trajectory based on the reference inductance curve; S4: TCM signal output: The target frequency conversion trajectory or the corrected frequency conversion trajectory is output as the final timing control modulation TCM signal to drive the subsequent power conversion circuit.

[0007] Furthermore, in S21, updating the reference inductance curve with actual inductance based on actual operating parameters to obtain updated inductance characteristic data includes: applying different currents across the inductor and measuring the inductance in real time to obtain a relationship curve between the inductance and the effective value of the inductor current; and then obtaining a relationship curve between the inductance and the phase of the output voltage based on the relationship curve between the inductance and the effective value of the current.

[0008] Furthermore, in TCM modulation, the formula for calculating the bipolar modulation switching frequency is as follows:

[0009] Where f s V is the switching frequency. dc For the input DC voltage, V acp The output is a sinusoidal voltage peak value, ω is the power frequency, ωt represents the current voltage output phase, R is the load resistance, L is the inductance, and I... zvs The negative current or zero current required for zero-voltage switching.

[0010] Furthermore, in S21, the step of correcting the current frequency conversion trajectory based on the updated inductor characteristic data to obtain the corrected frequency conversion trajectory includes: obtaining the actual inductance based on the current output voltage phase and the curve of the actual inductance changing with the voltage phase, and setting the deviation threshold to 10%; when the actual inductance L and the preset ideal inductance Lref satisfy (Lref-L) / Lref≤10%, Lref is directly substituted as L into the switching frequency formula to generate the frequency conversion trajectory.

[0011] Furthermore, in S21, the step of correcting the current frequency conversion trajectory based on the updated inductance characteristic data to obtain the corrected frequency conversion trajectory also includes: when the actual inductance L and the ideal inductance Lref satisfy (Lref-L) / Lref>10%, substituting the actual inductance L as the updated inductance L into the switching frequency formula to generate the corrected frequency conversion trajectory, and finally outputting the TCM signal.

[0012] Furthermore, the preset ideal inductance Lref is the initial inductance. As the inductor current changes (output voltage phase changes), the actual inductance will change.

[0013] The beneficial effects achieved by this invention are: 1. This invention combines the characteristics of actual TCM operation, updates the actual inductance of the output voltage in real time by changing the phase of the output voltage, and updates the frequency change curve in real time, thereby improving the accuracy of the output current, reducing the overall loss, and making it suitable for smaller inductors.

[0014] 2. This invention can correct the switching frequency curve under the TCM modulation strategy online, better adapt to real-time changing load conditions, improve output current accuracy, reduce conduction loss, and optimize the size of magnetic components.

[0015] To further understand the features and technical content of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings provided are for reference and illustration only and are not intended to limit the present invention. Attached Figure Description

[0016] Figure 1 This is a diagram of the traditional single-phase full-bridge inverter topology of the present invention; Figure 2 The present invention includes the conventional TCM modulation switching frequency variation curve and inductor current waveform. Figure 3 This is the curve showing the change in inductance of the present invention as a function of voltage phase; Figure 4 The inductor current waveform is shown in the TCM modulation strategy for adaptive inductance proposed in this invention. Figure 5 This is a block diagram of the TCM modulation strategy of the present invention; Figure 6 The curves showing the current output voltage phase and actual inductance as a function of voltage phase are shown in this embodiment of the invention. Detailed Implementation

[0017] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can understand the advantages and effects of the present invention from the content disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the spirit of the present invention. Furthermore, the accompanying drawings of the present invention are for simple illustrative purposes only and are not depictions of actual dimensions; this is stated in advance. The following embodiments will further describe the relevant technical content of the present invention in detail, but the disclosed content is not intended to limit the scope of protection of the present invention.

[0018] Example 1: Figure 2 The diagram shows the frequency conversion curve and operating waveform of the traditional TCM modulation method. In the operating waveform, the red waveform represents the inductor current, the black waveform represents the inductor current envelope, and the blue waveform represents the output current. TCM modulation uses a large inductor current ripple to turn on the switching transistor when the inductor current is 0 or negative, thus significantly reducing the system's turn-on losses. However, the large current ripple further increases the conduction losses. IZVS is the negative current required for the switching transistor to achieve zero-voltage turn-on in TCM modulation, i.e., IZVS in the switching frequency calculation formula. When the inductor current drops to the negative current -IZVS, the switching transistor performs the turn-on action, thus achieving zero-voltage turn-on. is,a is the inductor current waveform, ig,a is the output current waveform. For a purely resistive load, the output current waveform is consistent with the effective value waveform of the inductor current. isa,env is the upper envelope of the inductor current. Considering the operating characteristics of TCM, when the inverter output is a real-time changing sine wave, depending on the specific output voltage, such as... Figure 3 The actual inductance value shown changes with the output voltage. Although the change in actual inductance value with inductor current (or output voltage) is an inherent property of the inductor, existing technologies do not take this property into account. Using a constant inductance value to calculate the switching frequency range would result in a large frequency conversion range and reduced output current accuracy. The modulation strategy proposed in this embodiment updates the inductance value in real time based on the phase of the output voltage and corrects the frequency conversion curve, thereby effectively reducing the frequency conversion range, improving output current accuracy, and reducing conduction losses.

[0019] like Figure 5 As shown, this embodiment provides a method for inverter triangular current modulation based on inductance adaptive modulation, including the following steps: S1: Inductor Design and Initial Curve Acquisition: Perform inductor design for the circuit topology; based on the inductor design, acquire the curve data of the inductance of the inductor as a function of power, and record it as the reference inductor curve; S2: Frequency correction judgment: Determine whether frequency correction is required for the current operation; if not, proceed to step S3; if yes, proceed to step S21. S21: Inductance Update and Trajectory Correction: Update the reference inductance curve with actual inductance based on actual operating parameters to obtain updated inductance characteristic data; Based on the updated inductance characteristic data, correct the current frequency converter trajectory to obtain a corrected frequency converter trajectory. S3: Frequency Conversion Trajectory Generation: Generate the target frequency conversion trajectory based on the reference inductance curve; S4: TCM signal output: The target frequency conversion trajectory or the corrected frequency conversion trajectory is output as the final timing control modulation TCM signal to drive the subsequent power conversion circuit.

[0020] Furthermore, in S21, updating the reference inductance curve with actual inductance based on actual operating parameters to obtain updated inductance characteristic data includes: applying different currents across the inductor and measuring the inductance in real time to obtain a curve showing the relationship between the inductance and the effective value of the inductor current; and then obtaining a curve showing the relationship between the inductance and the phase of the output voltage based on the curve showing the relationship between the inductance and the effective value of the current.

[0021] After designing the inductor, the inductance change curve is obtained, and based on this, the inductance versus power curve is established: Furthermore, in TCM modulation, the formula for calculating the bipolar modulation switching frequency is as follows:

[0022] Where f s V is the switching frequency. dc For the input DC voltage, V acp The output is a sinusoidal voltage peak value, ω is the power frequency, ωt represents the current voltage output phase, R is the load resistance, L is the inductance, and I... zvs The negative current or zero current required for zero-voltage switching.

[0023] The inductance decreases as the effective value of the current flowing through the inductor decreases. Therefore, by applying different currents across the inductor and measuring the inductance in real time, the relationship curve between the inductance and the effective value of the inductor current can be obtained. For an inverter, the output voltage (current) is a regular sine wave. Therefore, given the output voltage phase and load, the effective value of the current flowing through the inductor can be obtained, and thus the relationship curve between the inductance and the output voltage phase can be obtained from the relationship curve between the inductance and the effective value of the inductor current. The switching frequency calculated using the switching frequency calculation formula for each phase constitutes the frequency conversion curve over the entire cycle, such as... Figure 6 As shown.

[0024] Furthermore, in S21, the step of correcting the current frequency conversion trajectory based on the updated inductor characteristic data to obtain the corrected frequency conversion trajectory includes: obtaining the actual inductance based on the current output voltage phase and the curve of the actual inductance changing with the voltage phase, and setting the deviation threshold to 10%; when the actual inductance L and the preset ideal inductance Lref satisfy (Lref-L) / Lref≤10%, Lref is directly substituted as L into the switching frequency formula to generate the frequency conversion trajectory.

[0025] Furthermore, in S21, the step of correcting the current frequency conversion trajectory based on the updated inductance characteristic data to obtain the corrected frequency conversion trajectory also includes: when the actual inductance L and the ideal inductance Lref satisfy (Lref-L) / Lref>10%, substituting the actual inductance L as the updated inductance L into the switching frequency formula to generate the corrected frequency conversion trajectory, and finally outputting the TCM signal.

[0026] Furthermore, the preset ideal inductance Lref is the initial inductance.

[0027] like Figure 4 As shown, under ideal conditions, the inductance is constant, and the inductor current is represented by the blue waveform. The actual inductance decreases as the output voltage increases. Without updating the inductance in the frequency change curve calculation, the inductor current is represented by the yellow waveform. Compared to the ideal inductor current, the actual inductance decreases with increasing output voltage, resulting in a larger ripple in the actual inductor current over the same switching cycle. This increases the system's conduction losses and affects the output current accuracy. The red waveform represents the current waveform with variable inductance after frequency correction. Based on the output voltage phase, the TCM modulation frequency conversion trajectory is corrected in real time to match the actual inductor current waveform with the ideal inductor current waveform, further reducing system conduction losses and improving output current accuracy. Furthermore, in this embodiment, since frequency correction technology is added to correct the frequency deviation caused by changes in inductance in real time, the inverter using TCM modulation no longer requires the inductance to remain constant. When designing magnetic components, inductors with appropriate nonlinear characteristics can be selected to significantly reduce the inductor volume and reduce the core loss in the low-frequency band, thereby improving the power density and overall efficiency of the inverter.

[0028] The above analysis of inverter operation shows that the advantages of the inverter triangular current modulation method proposed in this embodiment are mainly reflected in: Compared with traditional TCM modulation strategies, this embodiment can optimize output current accuracy; Compared with the traditional TCM modulation strategy, this embodiment can reduce conduction loss; Compared with the traditional TCM modulation strategy, this embodiment allows the inverter to use inductors with smaller size and lower core losses, thereby reducing the overall size and losses.

[0029] Example 2: This example should be understood to include all the features of any of the foregoing examples.

[0030] In TCM modulation, TCM modulation is used to generate the PWM modulation wave for frequency conversion. The formula for calculating the bipolar modulation switching frequency is used to calculate the frequency conversion trajectory. Both the target frequency conversion trajectory and the corrected frequency conversion trajectory of S4 are obtained based on this formula. The difference is: when the deviation between the actual inductance and the ideal inductance of the current phase does not exceed 10%, L in the formula is a fixed value Lref, and there is no correction; when the deviation between the actual inductance and the ideal inductance of the current phase exceeds 10%, L in the formula is replaced by the actual inductance of the current phase, and the corrected switching frequency is calculated, which is the corrected frequency conversion curve.

[0031] For example, such as Figure 3 When the phase is 30°, assuming the actual inductance L = 0.9Lref, that is, when the phase is < 30° (i.e., (Lref - L) / Lref ≤ 10%), the switching frequency can be directly calculated using the fixed value Lref in the formula. When the phase is > 30°, it is necessary to calculate based on... Figure 3 By calculating the inductance versus the output voltage phase curve, we can obtain the actual inductance L for the current phase. Then, we substitute this into the switching frequency calculation formula to obtain the corrected switching frequency. Based on this, we can obtain the corrected frequency conversion trajectory.

[0032] The relationship curve between the output voltage phase and the actual inductance is shown in the figure. Figure 3 As shown, this curve needs to be measured beforehand. In actual operation, for example, if the initial inductance is 500, when the voltage phase is 0.1, the actual inductance is 480 according to the relationship curve between the output voltage phase and the actual inductance. At this time, (Lref-L) / Lref≤10%, so no correction is required. When the voltage phase is 0.5, the actual inductance is 250 according to the relationship curve between the output voltage phase and the actual inductance. At this time, (Lref-L) / Lref>10%, so correction is required.

[0033] This embodiment, through specific examples and numerical descriptions, intuitively demonstrates the triggering conditions and calculation process of the correction mechanism, enabling those skilled in the art to implement the invention without any doubt, thus enhancing the clarity and operability of the technical solution.

[0034] The content disclosed above is only a preferred and feasible embodiment of the present invention, and is not intended to limit the scope of protection of the present invention. Therefore, all equivalent technical changes made based on the content of the present invention specification and drawings are included within the scope of protection of the present invention. Furthermore, the elements therein can be updated as technology develops.

Claims

1. A method for inverter triangular current modulation based on inductance adaptive modulation, characterized in that, Includes the following steps: S1: Inductor Design and Initial Curve Acquisition: Perform inductor design for the circuit topology; based on the inductor design, acquire the curve data of the inductance of the inductor as a function of power, and record it as the reference inductor curve; S2: Frequency correction judgment: Determine whether frequency correction is required for the current operation; if not, proceed to step S3; if yes, proceed to step S21. S21: Inductance Update and Trajectory Correction: Update the reference inductance curve with actual inductance based on actual operating parameters to obtain updated inductance characteristic data; Based on the updated inductance characteristic data, correct the current frequency converter trajectory to obtain a corrected frequency converter trajectory. S3: Frequency Conversion Trajectory Generation: Generate the target frequency conversion trajectory based on the reference inductance curve; S4: TCM signal output: The target frequency conversion trajectory or the corrected frequency conversion trajectory is output as the final timing control modulation TCM signal to drive the subsequent power conversion circuit.

2. A method for inverter triangular current modulation based on inductance adaptive modulation as described in claim 1, characterized in that, In S21, updating the reference inductance curve with actual inductance based on actual operating parameters to obtain updated inductance characteristic data includes: applying different currents across the inductor and measuring the inductance in real time to obtain a relationship curve between the inductance and the effective value of the inductor current; and then obtaining a relationship curve between the inductance and the phase of the output voltage based on the relationship curve between the inductance and the effective value of the current.

3. A method for inverter triangular current modulation based on inductance adaptive modulation as described in claim 2, characterized in that, In TCM modulation, the formula for calculating the bipolar modulation switching frequency is as follows: Where f s V is the switching frequency. dc For the input DC voltage, V acp The output is a sinusoidal voltage peak value, ω is the power frequency, ωt represents the current voltage output phase, R is the load resistance, L is the inductance, and I... zvs The negative current or zero current required for zero-voltage switching.

4. A method for inverter triangular current modulation based on inductance adaptive modulation as described in claim 3, characterized in that, In S21, the step of correcting the current frequency conversion trajectory based on the updated inductor characteristic data to obtain the corrected frequency conversion trajectory includes: obtaining the actual inductance based on the current output voltage phase and the curve of the actual inductance changing with the voltage phase, and setting the deviation threshold to 10%; when the actual inductance L and the preset ideal inductance Lref satisfy (Lref-L) / Lref≤10%, Lref is directly substituted as L into the switching frequency formula to generate the frequency conversion trajectory.

5. A method for inverter triangular current modulation based on inductance adaptive modulation as described in claim 4, characterized in that, In S21, the step of correcting the current frequency conversion trajectory based on the updated inductance characteristic data to obtain the corrected frequency conversion trajectory further includes: when the actual inductance L and the ideal inductance Lref satisfy (Lref-L) / Lref>10%, substituting the actual inductance L as the updated inductance L into the switching frequency formula to generate the corrected frequency conversion trajectory, and finally outputting the TCM signal.

6. A method for inverter triangular current modulation based on inductance adaptive modulation as described in claim 5, characterized in that, The preset ideal inductance value Lref is the initial inductance value.

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