Heterogeneous hybrid switch unit thermal reliability optimization method based on safe operation area

Abstract

The invention belongs to the technical field of thermal management and reliability optimization, and particularly discloses a heterogeneous hybrid switch unit thermal reliability optimization method based on a safe operation area, and the method comprises the following steps: S1, obtaining a corresponding two-dimensional safe operation area projection under a rated parameter according to the safe operation area of a heterogeneous hybrid switch unit, extracting a current maximum value Imax20 according to the regional projection; s2, acquiring a current load current IF, comparing the size of Imax20 with the size of IF, if Imax20 is greater than or equal to IF, performing S3, and if Imax20lt, performing S3; when IF, performing S4; s3, single parameter adjustment is carried out; s4, carrying out two-parameter adjustment; and S5, inputting the target optimization parameters into a PWM signal generation module, and generating SiC-based device and Si-based device driving signals corresponding to the target switching frequency and the SiC interruption proportion through cooperative work of the DSP and the FPGA, thereby expanding the safe operation area of the hybrid switch unit. The over-temperature risk of the hybrid switch unit is avoided, and the reliability of the hybrid switch unit is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal management and reliability optimization, and relates to a thermal reliability optimization method for a heterogeneous hybrid switch unit based on a safe operating area. Background Art

[0002] Heterogeneous hybrid switch cells, consisting of SiC-based and Si-based devices connected in parallel, can achieve high performance approaching that of wide-bandgap devices while significantly reducing overall costs. This provides a practical solution for breaking through development bottlenecks in the power electronics field. To achieve a balance between cost and performance, heterogeneous hybrid switch cells typically consist of high-current Si-based devices and low-current SiC-based devices. Because SiC-based devices bear the majority of switching losses and have a larger thermal resistance due to their smaller chip area, their junction temperature is often higher than that of Si-based devices. Under heavy load conditions, SiC-based devices face a greater risk of overheating. Therefore, reliability optimization of hybrid switch cells is particularly necessary to improve their operational reliability and stability.

[0003] Reliability optimization for existing hybrid switch units is typically achieved through mode switching. Under light load conditions, the hybrid switch unit uses a switching mode where the SiC-based device is turned on first and then off to ensure high conversion efficiency. Under heavy load or overload conditions, the switching sequence is altered, with the Si-based device turning on first and then off, aiming to reduce the junction temperature of the SiC-based device and alleviate overheating issues. However, this mode switching method is relatively simple and lacks sufficient flexibility. With only two fixed mode switches, overregulation may occur when the load increases slightly. This increases device losses and reduces overall system efficiency. Therefore, existing reliability optimization methods cannot achieve flexible adjustment based on operating conditions, compromising reliability while maintaining efficiency. Summary of the Invention

[0004] To address this technical issue, the present invention designs a thermal reliability optimization method for heterogeneous hybrid switch units based on a safe operating region. This method utilizes the safe operating region of the hybrid switch unit and calculates target optimization parameters in real time to achieve optimal regulation of the switching frequency and SiC interruption ratio. This ensures that the hybrid switch unit avoids overheating risks under different operating conditions while maintaining both reliability and efficiency.

[0005] The technical solution adopted in the present invention is:

[0006] A thermal reliability optimization method for a heterogeneous hybrid switch unit based on a safe operating region includes the following steps:

[0007] S1: According to the safe operation area of ​​the heterogeneous hybrid switch unit, the corresponding two-dimensional safe operation area projection under the rated parameters is obtained, and the current maximum value I is extracted according to the area projection. max_20 ;

[0008] S2: Get the current load current I F , compare I max_20 with I F The size of max_20 ≥I F When S3 is performed, if I max_20 F When , proceed to S4;

[0009] S3: Perform single parameter adjustment. Under the condition of rated switching frequency of 20kHz, adjust the operating point to the boundary of the safe operating area by adjusting the SiC interruption ratio.

[0010] S4: Perform dual parameter adjustments to reduce the switching frequency so that the maximum value of the safe operating region of the heterogeneous hybrid switch unit just covers the current load current, and then adjust the SiC interruption ratio to the value corresponding to the maximum point;

[0011] S5: Input the target optimization parameters into the PWM signal generation module. Through the collaborative work of DSP and FPGA, the SiC-based device and Si-based device drive signals corresponding to the target switching frequency and SiC interruption ratio are generated, thereby expanding the safe operating area of ​​the hybrid switch unit and avoiding the risk of overheating of the hybrid switch unit.

[0012] Furthermore, the specific contents of S1 include: obtaining the corresponding two-dimensional r under rated parameters according to the safe operation area of ​​the heterogeneous hybrid switch unit break -f safe operating area projection. As the SiC interruption ratio decreases, the maximum safe operating current value of the heterogeneous hybrid switch unit first increases and then decreases, so the current maximum value I can be extracted max_20 .

[0013] Furthermore, the specific contents of S3 include: the numerical value of the SiC interruption ratio is obtained by interpolation, based on the projection boundary data of the two-dimensional safe operating area, with the current load current as a known input parameter, and a linear or other interpolation function is used to inversely solve the corresponding SiC device interruption conduction ratio value.

[0014] Preferably, a linear interpolation function is used to reversely solve the corresponding SiC device interruption and conduction ratio value. It is known that the current load current I F As well as the data points (I1, r1) and (I2, r2) of the projection boundary of the two-dimensional safe operation area of ​​the adjacent current, the corresponding target SiC interruption ratio r is calculated. break : ​

[0015]

[0016] Where I1 and I2 are the currents of adjacent data points; r1 and r2 are the SiC interruption ratios of adjacent data points.

[0017] Furthermore, the specific contents of S4 include: when the load current increases, the load current exceeds the current maximum safe operating current, and also exceeds the maximum value I of the maximum safe operating current at the switching frequency of 20kHz max_20 , perform dual parameter adjustment, by reducing the switching frequency so that the maximum value of the safe operation area of ​​the heterogeneous hybrid switch unit just covers the current load current, and then adjust the SiC interruption ratio to the value corresponding to the maximum point.

[0018] The beneficial effects of the present invention are:

[0019] 1) When the load current exceeds the safe operating area corresponding to the current parameters, the reliability of the hybrid switch unit is improved and the risk of device overheating is avoided by comprehensively adjusting the switching frequency and SiC interruption ratio.

[0020] 2) A calculation process for the target optimization parameters was designed, which enabled real-time calculation of the required switching frequency and SiC interruption ratio, enabling more accurate control of the junction temperature of the hybrid switch unit within 150°C.

[0021] 3) The proposed adaptive reliability optimization method maintains the rated operating parameters unchanged when the load is small, takes action when the load current exceeds the safe operating area, and adjusts the parameters based on the minimum adjustment amplitude of the switching frequency and SiC interruption ratio to ensure the reliability and work efficiency of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 It is a safe operating area diagram of the hybrid switch unit;

[0024] Figure 2 It is a two-dimensional projection diagram of the safe operating area when a single parameter is adjusted;

[0025] Figure 3 It is a two-dimensional projection diagram of the safe operating area when dual parameters are adjusted;

[0026] Figure 4It is the target optimization flow chart;

[0027] Figure 5 is the experimental load profile;

[0028] Figure 6 This is the experimental junction temperature waveform of the hybrid switch unit before optimization;

[0029] Figure 7 This is the experimental junction temperature waveform of the optimized hybrid switch unit;

[0030] Figure 8 It is the adjustment curve of the switching frequency during the reliability optimization process;

[0031] Figure 9 It is the adjustment curve of SiC interruption ratio in the reliability optimization process. DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] like Figure 4 As shown, the present invention designs a hybrid switch unit reliability optimization operation process, which can dynamically optimize the switching frequency and SiC interruption ratio parameters in real time according to the current load current, thereby effectively improving the thermal reliability of the hybrid switch unit. It includes the following steps:

[0034] 1) According to the safe operation area of ​​the heterogeneous hybrid switch unit, obtain the corresponding two-dimensional r under rated parameters break -f safe operating area projection. As the SiC interruption ratio decreases, the maximum safe operating current value of the heterogeneous hybrid switch unit first increases and then decreases, so the current maximum value I can be extracted max_20 .

[0035] 2) Get the current load current I F , and compare I max_20 with I F According to I max_20 with I F Based on the comparison results, the switching frequency and SiC interruption ratio are adjusted in the following two cases.

[0036] 3) When I max_20 ≥I F, a single parameter adjustment is performed. At this time, there is no need to adjust the switching frequency. Under the condition of a rated switching frequency of 20kHz, the load current requirement can be met by adjusting the SiC interruption ratio. Since the heterogeneous hybrid switch unit is a parallel structure, the smaller the SiC interruption ratio, the smaller the overall conduction loss of the hybrid switch unit, and the higher the inverter efficiency. Therefore, it is sufficient to adjust the operating point to the boundary of the safe operating area. The value of the required SiC interruption ratio is obtained by interpolation. Based on the projection boundary data of the two-dimensional safe operating area, with the current load current as the known input parameter, a linear or other interpolation function is used to inversely solve the corresponding SiC device interruption conduction ratio value. Taking linear interpolation as an example, the calculation formula is as follows:

[0037] The current load current I is known F , and the data points (I1, r1) and (I2, r2) of the projection boundary of the two-dimensional safe operation area of ​​the adjacent current, calculate the corresponding target SiC interruption ratio r break

[0038]

[0039] 4) When I max_20 F When the load current reaches a certain level, dual parameter adjustments are performed. In this case, the switching frequency needs to be adjusted to expand the safe operating range to meet the load current requirements. By reducing the switching frequency until the maximum value of the safe operating range of the heterogeneous hybrid switch unit just covers the current load current, the SiC interruption ratio is adjusted to the value corresponding to the maximum value.

[0040] 5) Finally, the target optimization parameters are input into the PWM signal generation module. Through the collaborative work of the DSP and FPGA, drive signals for the SiC- and Si-based devices corresponding to the target switching frequency and SiC interruption ratio are generated, thereby expanding the safe operating range of the hybrid switch unit and avoiding the risk of overheating of the hybrid switch unit.

[0041] It should be noted that the safe operating area of ​​the hybrid switch unit is as follows: Figure 1 As shown, it can be seen that its boundary is related to the switching frequency (f) and the SiC interruption ratio (r break ) is closely related. Therefore, from the perspective of parameter adjustment, two scenarios can be categorized: single parameter adjustment, and dual parameter adjustment that coordinates the switching frequency and SiC interruption ratio. The following will provide a detailed analysis of these two scenarios.

[0042] (1) Single parameter adjustment

[0043] The inverter initially operates under rated conditions (switching frequency is 20kHz), and the corresponding safe operating area boundary of the heterogeneous hybrid switch unit is as follows: Figure 2 ​As shown in the figure. For ease of analysis, the figure is projected onto a two-dimensional coordinate plane composed of the load current and the SiC interruption ratio. The filled-in square area in the figure corresponds to the safe operating area of ​​the heterogeneous hybrid switch unit. To reduce the conduction loss of the heterogeneous hybrid switch unit and improve the operating efficiency of the inverter, the SiC interruption ratio is typically set to 0. In this case, the maximum operating current boundary of the heterogeneous hybrid switch unit is at point a1. Assuming that when the load increases, the operating point of the heterogeneous hybrid switch unit changes from point a1 to point b1, the load current will exceed the safe operating area as shown in the figure. If active regulation is not implemented at this time, the SiC-based devices within the heterogeneous hybrid switch unit will face the risk of overheating.

[0044] The trend in the safe operating area boundary indicates that reducing the switching frequency and increasing the SiC interruption ratio can help expand the maximum safe operating area. However, changes in the switching frequency affect the inverter's output power quality, while adjusting the SiC interruption ratio does not affect the overall modulation signal generation. Therefore, prioritizing the SiC interruption ratio is a more appropriate approach. As shown in the figure, as the SiC interruption ratio increases, the operating point of the heterogeneous hybrid switch unit moves from point b1 to point c1, at which point the operating point returns to the boundary of the safe operating area. This operating point ensures safe and reliable operation of the heterogeneous hybrid switch unit while minimizing the adjustment range of the SiC interruption ratio, avoiding additional losses in the hybrid switch unit.

[0045] (2) Dual parameter adjustment

[0046] from Figure 2 The two-dimensional safe operating area at a switching frequency of 20kHz can be seen. As the SiC interruption ratio decreases, the maximum safe operating current value of the heterogeneous hybrid switch unit first increases and then decreases, and there is a maximum value I max_20 When the load current exceeds I max_20 When the SiC interruption ratio is adjusted, the safe operating area cannot be further expanded to cover the current load current. Figure 1 The safe operating area shown in the figure shows that as the switching frequency decreases, the maximum value of the safe operating current tends to expand. Therefore, by projecting the two-dimensional safe operating area at different switching frequencies to the same coordinate, we can get Figure 3 . Figure 3 The filled-in area in the lower center corresponds to the two-dimensional safe operation of the heterogeneous hybrid switch unit at a switching frequency of 20kHz. When the SiC interruption ratio is 0, the maximum safe operating point of the corresponding heterogeneous hybrid switch unit is at point a2. When the load current increases and the heterogeneous hybrid switch unit moves from operating point a2 to b2, the load current exceeds the current maximum safe operating current and also exceeds the maximum value of the maximum safe operating current at a switching frequency of 20kHz, Imax_20 At this time, it is necessary to reduce the switching frequency to further expand the safe operating area of ​​the heterogeneous hybrid switch unit to meet the load requirements. By reducing the switching frequency, the safe operating area of ​​the heterogeneous hybrid switch unit is expanded to Figure 3 The dotted fill area shown clearly shows a significant increase in the maximum value compared to the 20kHz switching frequency. The maximum value in this area perfectly covers the increased load current, and the switching frequency adjustment amplitude corresponding to the extreme value is minimal, indicating the smallest impact on output power quality. The SiC interruption ratio corresponding to the maximum value point c2 differs from that corresponding to point a2. Therefore, further adjustment of the SiC interruption ratio is required to shift the operating point of the heterogeneous hybrid switch unit from point b2 to point c2, thereby returning it to the safe operating range.

[0047] The above-mentioned adaptive reliability optimization operation concept is aimed at the working condition of increasing load current. When the load current decreases, the concept of parameter adjustment is similar, that is, to ensure that the switching frequency and SiC interruption ratio deviate from the rated value to the minimum, among which the switching frequency has a higher priority. When the load current decreases, the thermal stress of the switch unit decreases. If the parameters continue to deviate from the rated value, it will cause unnecessary losses. Therefore, it is necessary to ensure the efficiency of the device by adjusting the parameters while keeping the junction temperature within the limit. If the load current is less than or equal to I max_20 , then keep the switching frequency at the rated value of 20kHz and calculate the required SiC interruption ratio by interpolation; if the load current is greater than I max_20 , dual parameter adjustment is required, that is, adjusting the switching frequency and SiC interruption ratio at the same time.

[0048] Experimental verification:

[0049] In order to verify the reliability of the proposed hybrid switch unit adaptive reliability optimization operation strategy based on the safe operation area in the face of continuous adjustment under complex working conditions, the hybrid switch unit adaptive reliability optimization operation experiment was carried out for the designed multi-segment load fluctuation working conditions. The designed load profile is as follows Figure 5 The load power switching sequence is as follows: 5.8kW→7.42kW→8.4kW→7.8kW→6kW→6.5kW. The switching frequency is kept at 20kHz and the SiC interruption ratio is 0. The junction temperature waveform of the heterogeneous hybrid switch unit before optimization is shown as follows: Figure 6 shown.

[0050] from Figure 6The junction temperature curves for the heterogeneous hybrid switch unit show that the junction temperatures of SiC-based devices are consistently higher than those of Si-based devices. Furthermore, when the load power is switched to heavy loads of 7.42kW, 8.4kW, and 7.8kW, the junction temperature of the SiC-based devices fluctuates by more than 150°C. In these conditions, the SiC-based devices face a significant risk of overheating, threatening the overall reliability of the heterogeneous hybrid switch unit.

[0051] After adopting the adaptive reliability optimization operation strategy proposed in this invention, the experimental waveform of the junction temperature of the heterogeneous hybrid switch unit under the same load fluctuation conditions is as follows: Figure 7 shown.

[0052] By comparing the junction temperature experimental waveforms of the heterogeneous hybrid switch unit before and after optimization, it can be seen that through the coordinated regulation of switching frequency and SiC interruption ratio, the safe operating area of ​​the hybrid switch unit is expanded, so that the junction temperature of SiC-based devices and Si-based devices are both controlled within 150°C, effectively alleviating the reliability of SiC-based devices.

[0053] The switching frequency and SiC interruption ratio parameter control curves corresponding to each load condition of the load profile are as follows: Figure 8 and 9 As shown in the figure, when the load increases from 5.8kW to 7.42kW, f is kept at 20kHz and only r is adjusted. break When the load increases from 7.42kW to 8.4kW, it is only necessary to actively reduce f to 12.1kHz to maintain r break When the load drops from 8.4kW to 7.8kW, f needs to be restored to 19.3kHz, r break To 0.4, to ensure the output power quality while avoiding overheating. When the load is reduced from 7.8kW to 6kW, f and r break The load requirements can be met by returning to 20kHz and 0, respectively. When the load increases from 6kW to 6.5kW, the rated parameters remain unchanged because the load current is still within the safe operating area.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention are included in the scope of protection of the present invention.

Claims

1. A thermal reliability optimization method for heterogeneous hybrid switch units based on a safe operating area, characterized in that: The following steps are involved: S1: According to the safe operation area of ​​the heterogeneous hybrid switch unit, the corresponding two-dimensional safe operation area projection under the rated parameters is obtained, and the current maximum value I is extracted according to the area projection. max_20 ; S2: Get the current load current I F , compare I max_20 with I F The size of max_20 ≥I F When S3 is performed, if I max_20 F When , proceed to S4;​ S3: Perform single parameter adjustment. Under the condition of rated switching frequency of 20kHz, adjust the operating point to the boundary of the safe operating area by adjusting the SiC interruption ratio. S4: Perform dual parameter adjustments to reduce the switching frequency so that the maximum value of the safe operating region of the heterogeneous hybrid switch unit just covers the current load current, and then adjust the SiC interruption ratio to the value corresponding to the maximum point; S5: Input the target optimization parameters into the PWM signal generation module. Through the collaborative work of DSP and FPGA, the SiC-based device and Si-based device drive signals corresponding to the target switching frequency and SiC interruption ratio are generated, thereby expanding the safe operating area of ​​the hybrid switch unit and avoiding the risk of overheating of the hybrid switch unit.

2. The method for optimizing thermal reliability of heterogeneous hybrid switch units based on safe operating area according to claim 1, characterized in that: The specific contents of S1 include: depicting the safe operating area based on the electrothermal coupling model of the hybrid switch unit, extracting the current maximum value I according to the two-dimensional coordinate plane composed of the inverter load current and SiC interruption ratio max_20 .

3. The method for optimizing thermal reliability of heterogeneous hybrid switch units based on safe operating area according to claim 1, characterized in that: The specific contents of S3 include: the numerical value of the SiC interruption ratio is obtained by interpolation. Based on the projection boundary data of the two-dimensional safe operating area, the current load current is used as a known input parameter, and a linear or other interpolation function is used to inversely solve the corresponding SiC device interruption-on ratio value.

4. The method for optimizing thermal reliability of heterogeneous hybrid switch units based on safe operating area according to claim 3, characterized in that: Use the linear interpolation function to reversely solve the corresponding SiC device interruption and conduction ratio value, given the current load current I F As well as the data points (I1, r1) and (I2, r2) of the projection boundary of the two-dimensional safe operation area of ​​the adjacent current, the corresponding target SiC interruption ratio r is calculated. break : Where I1 and I2 are the currents of adjacent data points; r1 and r2 are the SiC interruption ratios of adjacent data points.

5. The method for optimizing thermal reliability of heterogeneous hybrid switch units based on safe operating area according to claim 1, characterized in that: The specific contents of S4 include: When the load current increases, the load current exceeds the current maximum safe working current, and also exceeds the maximum value I of the maximum safe working current at the switching frequency of 20kHz max_20 , perform dual parameter adjustment, by reducing the switching frequency so that the maximum value of the safe operation area of ​​the heterogeneous hybrid switch unit just covers the current load current, and then adjust the SiC interruption ratio to the value corresponding to the maximum point.

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