A junction temperature optimization method for hybrid device type three-level ANPC inverter

Abstract

The present application provides a junction temperature optimization method for a hybrid device type three-level ANPC inverter, characterized in that it includes: obtaining the current junction temperature value of the first inner tube or the second inner tube; judging whether the current junction temperature value exceeds the junction temperature threshold; if so, obtaining the current AC side current, and determining the range of the AC side current in the set current threshold interval, wherein the set current threshold interval includes the first current threshold and the second current threshold or the first current threshold, and the first current threshold is less than the second current threshold; based on the set current threshold interval, adjusting the control mode of the inverter operation; wherein the control mode includes the corresponding modulation strategy and switching mode. Different control modes are used to adjust the operation of the inverter, thereby greatly improving the junction temperature of the inverter.

Description

Technical Field

[0001] The present application relates to the field of electronic devices, and in particular to the field of electronic device junction temperature optimization. Background Art

[0002] The reliability of power devices is an important indicator of power electronic converters. The life of the converter depends on the power device with the shortest life. Therefore, the life of the power device with the shortest life can be extended by reducing the maximum junction temperature between converter devices, thereby increasing the life of the entire converter. The hybrid device in the converter is generally composed of SiC with a small current level and Si IGBT with a large current level in parallel.

[0003] However, the existing methods for improving the junction temperature of converter devices are either poor in the scenario where the junction temperature difference between the high thermal stress SiC and the SiIGBT connected in parallel is large, or poor in the scenario where the junction temperature difference between the high thermal stress SiC and the switch node at other locations is large. Therefore, how to improve the effect of improving the junction temperature in the above scenarios is an urgent problem to be solved. Summary of the invention

[0004] In order to overcome the above technical defects, the present application provides a junction temperature optimization method for a hybrid device type three-level ANPC inverter.

[0005] To achieve the above objectives, this application is implemented according to the following technical solutions:

[0006] The present application provides a junction temperature optimization method for a hybrid device type three-level ANPC inverter, wherein the inverter comprises a first inner tube and a second inner tube, a first outer tube and a second outer tube, a first clamping tube and a second clamping tube, wherein the first inner tube and the second inner tube are formed by connecting a Si IGBT and a SiC MOSFET in parallel, and the first outer tube, the second outer tube, the first clamping tube, and the second clamping tube all adopt Si IGBT, including:

[0007] Acquire a current junction temperature value of the first inner tube or the second inner tube;

[0008] Determining whether the current junction temperature value exceeds a junction temperature threshold;

[0009] If yes, then obtain the current AC side current, and determine the range of the set current threshold interval in which the AC side current is located, wherein the set current threshold interval includes a first current threshold and a second current threshold or the first current threshold, and when the set current threshold interval includes the first current threshold and the second current threshold, the first current threshold is less than the second current threshold;

[0010] Based on the interval range of the set current threshold interval, the control mode of the inverter operation is adjusted; wherein the control mode includes a corresponding modulation strategy and a switching mode.

[0011] Optionally, before the step of obtaining the current junction temperature value of the first inner tube or the second inner tube, the step includes:

[0012] When the inverter is initially operated, the first current threshold and the second current threshold are both set to be greater than the AC current peak value, so that the inverter operates according to the initial control mode.

[0013] Optionally, a specific process of determining the first current threshold and the second current threshold or the first current threshold is as follows:

[0014] Step S301: obtaining a first current adjustment threshold corresponding to the first current threshold, and obtaining a second current adjustment threshold corresponding to the second current threshold;

[0015] Step S302: determining whether a first absolute value of a temperature difference between the SiC MOSFET in the first inner tube and the Si IGBT is greater than or equal to a second absolute value of a temperature difference between the first inner tube SiC MOSFET and the first outer tube Si IGBT;

[0016] Step S303: If yes, determining whether the junction temperature of the SiC MOSFET in the first inner tube is greater than or equal to the junction temperature of the Si IGBT in the first inner tube;

[0017] Step S304: If yes, lower the first current adjustment threshold to obtain a first unset current threshold interval;

[0018] Get the current AC side current at the current moment,

[0019] Determining that the AC side current is within the interval range of the first unset current threshold interval;

[0020] Determining a control mode of the inverter operation based on the interval range of the first interval of the unset current threshold;

[0021] Step S305: determining whether a cycle end condition is met at the current moment, wherein the cycle condition is that the temperature difference between the first inner tube SiC MOSFET and the first inner tube Si IGBT is zero, and the temperature difference between the first inner tube SiC MOSFET and the first outer tube Si IGBT is also zero;

[0022] Step S306: If yes, the lowered first current adjustment threshold is determined as the first current threshold, the second current adjustment threshold is determined as the second current threshold, and the first unadjusted current threshold interval is determined as the adjusted current threshold interval;

[0023] If not, execute step S301.

[0024] Optionally, if the judgment result of step 303 is no, then the first current adjustment threshold is increased to obtain a second unset current threshold interval, and the increased first current adjustment threshold is less than or equal to the second current adjustment threshold;

[0025] Get the current AC side current at the current moment,

[0026] Determining that the AC side current is within the interval range of the second unset current threshold interval;

[0027] Determining a control mode of the inverter based on the interval range of the second unset current threshold interval;

[0028] Determine whether the end-loop condition is met at the current moment;

[0029] If so, determining whether the first current adjustment threshold is equal to the second current adjustment threshold;

[0030] If yes, then set the second current adjustment threshold equal to the first current adjustment threshold, determine the first current adjustment threshold as the first current threshold, and use the second unadjusted current threshold interval as the adjusted current threshold interval;

[0031] If the first current adjustment threshold is less than the second current adjustment threshold;

[0032] Then the first current adjustment threshold is determined as the first current threshold, the second current adjustment threshold is determined as the second current threshold; the second unadjusted current adjustment threshold interval is determined as the adjusted current threshold interval;

[0033] If the loop end condition is not met at the current moment, step S301 is executed.

[0034] Optionally, the step 302 includes:

[0035] If a first absolute value of a temperature difference between the SiC MOSFET and the Si IGBT in the first inner tube is smaller than a second absolute value of a temperature difference between the first inner tube SiC MOSFET and the first outer tube Si IGBT;

[0036] Then, it is determined whether the junction temperature at the first inner tube SiC MOSFET is lower than the junction temperature at the first outer tube Si IGBT;

[0037] If yes, then increase the second current adjustment threshold to obtain a third unset current threshold interval;

[0038] Get the AC side current at the current moment;

[0039] Determining that the AC side current is within the interval range of the third unset current threshold interval;

[0040] Determining a control mode of the inverter operation based on an interval range of the third unset current threshold interval;

[0041] Determine whether the end-loop condition is met at the current moment;

[0042] If yes, the first current adjustment threshold is determined as the first current threshold, the second current adjustment threshold is determined as the second current threshold; the third unadjusted current threshold interval is determined as the adjusted current threshold interval;

[0043] If not, execute step S301.

[0044] Optionally, after the step of determining whether the junction temperature of the SiC MOSFET in the first inner tube is lower than the junction temperature of the Si IGBT in the first outer tube, the step further includes:

[0045] If not, lowering the second current adjustment threshold;

[0046] Determining whether the lowered second current adjustment threshold is less than the first current adjustment threshold;

[0047] If yes, the first current adjustment threshold is used as the second current adjustment threshold, and the reduced second current adjustment threshold is used as the first current adjustment threshold to obtain a fourth unset current threshold interval;

[0048] Get the current AC side current at the current moment,

[0049] Determining that the AC side current is within the interval range of the fourth unset current threshold interval;

[0050] Determining a control mode of operation of the inverter based on an interval range of the fourth unset current threshold interval;

[0051] Determine whether the end-loop condition is met at the current moment;

[0052] If yes, the first current adjustment threshold is determined as the first current threshold, the second current adjustment threshold is determined as the second current threshold; the fourth unadjusted current threshold interval is determined as the adjusted current threshold interval;

[0053] If the loop end condition is not met at the current moment, step S301 is executed.

[0054] Optionally, after the step of determining whether the lowered second current adjustment threshold is less than the first current adjustment threshold, the step includes:

[0055] If not, the fifth unset current threshold interval is obtained;

[0056] Get the AC side current at the current moment;

[0057] Determining that the AC side current is within the interval range of the fifth unset current threshold interval;

[0058] Determining a control mode of the inverter operation based on an interval range of the fifth unset current threshold interval;

[0059] Determine whether the end-loop condition is met at the current moment;

[0060] If so, determining whether the lowered second current adjustment threshold is equal to the first current adjustment threshold;

[0061] If yes, then the lowered second current adjustment threshold is set equal to the first current adjustment threshold, the first current adjustment threshold is used as the first current threshold, and the fifth unadjusted current threshold interval is used as the adjusted current threshold interval;

[0062] If not, the first current adjustment threshold is determined as the first current threshold, the second current adjustment threshold is determined as the second current threshold, and the fifth unadjusted current threshold interval is used as the adjusted current threshold interval;

[0063] If the loop end condition is not met at the current moment, step S301 is executed.

[0064] Optionally, adjusting the control mode of the inverter operation based on the set current threshold interval includes:

[0065] The control mode corresponding to the set current threshold interval is determined, and the inverter is operated according to the modulation strategy and switching mode corresponding to the control mode.

[0066] This application has the following beneficial effects:

[0067] The present application obtains the AC side current at the current moment by judging that the junction temperature value at the current moment exceeds the junction temperature threshold, and then determines the control mode corresponding to the interval range according to the current AC side current and the interval range of the set current threshold interval, and then adopts the corresponding modulation strategy and switching mode under the control mode to adjust the working mode of the inverter, so as to optimize the junction temperature of the inverter and reduce the junction temperature of the inverter.

[0068] In addition to the above-described purposes, features and advantages, the present application has other purposes, features and advantages. The present application will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0070] Figure 1 It is a structural diagram of the inverter of this application.

[0071] FIG. 2( a ) is a schematic diagram of a modulation strategy PWMA provided in an embodiment of the present application.

[0072] FIG2( b ) is a schematic diagram of a modulation strategy PWMB provided in an embodiment of the present application.

[0073] FIG3( a ) is a schematic diagram of a switch mode 1 provided in an embodiment of the present application.

[0074] FIG3( b ) is a schematic diagram of switch mode 2 provided in an embodiment of the present application.

[0075] Figure 4 It is a flow chart of a junction temperature optimization method of a hybrid device type three-level ANPC inverter provided in an embodiment of the present application.

[0076] FIG5( a ) is a schematic diagram of a current threshold range and a corresponding control mode provided in an embodiment of the present application.

[0077] FIG5( b ) is a schematic diagram of another current threshold range and corresponding control mode provided in an embodiment of the present application.

[0078] Figure 6 It is a comparison chart of the experimental results of junction temperature optimization in the embodiments of the present application. DETAILED DESCRIPTION

[0079] The embodiments of the present application are described in detail below with reference to the accompanying drawings; however, the present application can be implemented in many different ways as defined and covered by the claims.

[0080] Since the present application is to adjust the junction temperature of the inverter, the inverter structure of the present application is briefly introduced and described. Figure 1 As shown, the main structure of the inverter includes a first outer tube S1, a second outer tube S4, a first inner tube S2, a second inner tube S3, a first clamping tube S5, and a second clamping tube S6. The first inner tube S2 and the second inner tube S3 are hybrid devices (composed of Si IGBT and SiC MOSFET in parallel), and the first outer tube S1, the second outer tube S4, the first inner tube S2, the second inner tube S3, the first clamping tube S5, and the second clamping tube S6 are all composed of Si IGBT.

[0081] In this application, different control modes are used to adjust the junction temperature, and different control modes include corresponding modulation strategies and switching modes. Here, the detailed modulation strategies and switching modes are described in detail:

[0082] Modulation strategy PWMA: PWM, or pulse width modulation, is a method of digitally encoding analog signal levels. As shown in Figure 2 (a), g1, g2, g3, g4, g5, and g6 are the drive signals of S1, S2, S3, S4, S5, and S6, respectively. When OL and OU are in the zero state, the inner tube switches at a high frequency, and the rest switches at a low frequency, which concentrates the switching events on the inner tube, that is, the switching loss and reverse recovery loss are concentrated on the inner tube.

[0083] Modulation strategy PWMB: As shown in Figure 2 (b), g1, g2, g3, g4, g5, and g6 are the driving signals of S1, S2, S3, S4, S5, and S6 respectively. When OU1 and OL1 are in the zero state, the outer tube and the clamping tube switch at a high frequency, and the inner tube switches at a low frequency, and the inner tube only generates conduction loss.

[0084] Switching mode 1: As shown in Figure 3 (a), switching mode 1 can be a driving timing of SiC MOSFET turning on first and then off, using a fixed delay time to make Si IGBT produce soft switching.

[0085] Switching mode 2: As shown in Figure 3 (b), switching mode 2 can be a driving sequence in which the Si IGBT is turned on first and then off, and a fixed delay time is used to make the SiC produce soft switching.

[0086] In order to solve the technical problems mentioned in the above background technology, Figure 4As shown, the present application proposes a junction temperature optimization method for a hybrid device type three-level ANPC inverter, wherein the inverter includes a first inner tube and a second inner tube, a first outer tube and a second outer tube, a first clamping tube and a second clamping tube, wherein the first inner tube and the second inner tube are formed by connecting Si IGBT and SiCMOSFET in parallel, and the first outer tube, the second outer tube, the first clamping tube, and the second clamping tube are all SiIGBTs. The specific steps include:

[0087] Step S101: obtaining a current junction temperature value of the first inner tube or the second inner tube;

[0088] Because the junction temperature optimization method of the present application requires certain triggering working conditions. Therefore, before obtaining the current junction temperature value of the first inner tube S2 or the second inner tube S3, it is necessary to set the specific working conditions of the inverter. Because in this application, the corresponding control mode is selected according to the set current threshold interval of the alternating current. The set current threshold interval includes two different situations, such as the two different situations shown in Figure 5 (a) and Figure 5 (b). In Figure 5 (a), the first current threshold is included. and the second current threshold , Figure 5(b), includes the first current threshold That is to say, the present application includes two different set current threshold intervals, and different set current threshold intervals include different numbers of current thresholds. The specific process of determining the above different current threshold intervals will be described in detail later, which will be omitted here.

[0089] When the inverter in this application needs junction temperature optimization, during the initial operation, the first current threshold is set and the second current threshold , are greater than the peak value of the AC current , so that the inverter operates according to the initial control mode, which can ensure that the inverter will not have too high junction temperature during operation, and then carry out subsequent processing.

[0090] When obtaining the junction temperature, the present application generally obtains the current junction temperature values ​​of the first inner tube S2 and the second inner tube S3 of the inverter, that is, after setting the initial working operation state of the inverter, by analyzing the loss distribution, it is inferred that the device with higher thermal stress is the anti-parallel diode of the SiC MOSFE and Si IGBT of the first inner tube S2, or the anti-parallel diode of the SiC MOSFE and Si IGBT of the second inner tube S3, and the junction temperatures of the two are directly measured or indirectly obtained.

[0091] It should be noted that the specific method for obtaining the current junction temperature in this application is not specifically limited in this document, and any method that can obtain the above-mentioned inner tube junction temperature value is acceptable.

[0092] Step S102: determining whether the current junction temperature value exceeds a junction temperature threshold;

[0093] After obtaining the current junction temperature value, a judgment needs to be made, that is, whether the current junction temperature value exceeds the junction temperature threshold. The junction temperature threshold is determined based on the operation target of the inverter. That is, when the goal is high efficiency and safe and reliable operation, the threshold junction temperature can be set close to the maximum operating junction temperature value given in the data sheet; if the switching device is aimed at operating at a lower temperature, the appropriate threshold temperature can be set according to the actual situation.

[0094] Step S103: If yes, then obtain the current AC side current, and determine the AC side current, the set current threshold interval, wherein the set current threshold interval includes a first current threshold and a second current threshold or the first current threshold, and when the set current threshold interval includes the first current threshold and the second current threshold, the first current threshold is less than the second current threshold;

[0095] If the current junction temperature exceeds the junction temperature threshold, it means that the inverter is operating in an overtemperature state and the junction temperature of the inverter needs to be optimized. , and then determine the current AC side current , which is in the set current threshold interval, and then selects the control mode corresponding to the set current threshold interval, and then adjusts the working mode of the inverter to the control mode, thereby achieving junction temperature optimization.

[0096] The set current threshold interval is a current threshold interval in which the current threshold value has been determined to be relatively accurate. The set current threshold interval includes a first current threshold and a second current threshold or a first current threshold, wherein when the set current threshold interval includes the first current threshold and the second current threshold, that is, if two thresholds appear, the first current threshold is less than the second current threshold. That is to say, the values ​​of the first current threshold and the second current threshold at this time are relatively accurate values, and the value of the first current threshold is less than the value of the second current threshold. Since the relatively accurate values ​​of the first current threshold and the second current threshold in the present application are obtained through repeated tests and adjustments. Therefore, the above-mentioned different current threshold intervals may occur, including the first current threshold and the second current threshold as shown in Figure 5 (a), and also including the situation in Figure 5 (b) where there is only the first current threshold. The following is a detailed description of how to determine the specific situations of Figures 5 (a) and 5 (b):

[0097] Step S301: obtaining a first current adjustment threshold corresponding to the first current threshold, and obtaining a second current adjustment threshold corresponding to the second current threshold;

[0098] In determining the first current threshold and the second current threshold When the first current threshold is set, the present application The corresponding first current adjustment threshold , and the second current threshold The corresponding second current adjustment threshold . The first current threshold and the first current adjustment threshold , and the second current threshold and the second current adjustment threshold , the only difference is that the corresponding values ​​are different. Therefore, in order to avoid confusion, the same letter variables are used here.

[0099] When setting the first current adjustment threshold and the second current adjustment threshold When the first current is adjusted, it needs to be set. The initial setting is the peak value of the AC current of the first preset ratio , the second current adjustment threshold Set to the second preset ratio of the AC current peak , the first preset ratio is less than 1, and the second preset ratio is greater than 1. For example, the first current adjustment threshold Initial value of Set to 0.99 , the second current adjustment threshold The initial value is set to 1.01 Then, the current adjustment threshold value to be adjusted next time is determined according to the current junction temperature. After multiple adjustments, the current threshold value that makes the converter reach a relatively balanced junction temperature state can be found.

[0100] It should be noted that the present application determines the first current threshold and the second current threshold , is determined by the perturbation method using simulation software or hardware experiments.

[0101] First current adjustment threshold and the second current adjustment threshold The above settings are only made during the initial run. Each subsequent change is adjusted based on the latest changes and does not remain unchanged.

[0102] Step S302: determining whether a first absolute value of a temperature difference between the SiC MOSFET in the first inner tube and the Si IGBT in the first inner tube is greater than or equal to a second absolute value of a temperature difference between the first inner tube SiC MOSFET and the first outer tube Si IGBT;

[0103] After determining the first current adjustment threshold , and the second current adjustment threshold After that, combined with Figure 5(a) and Table 1,

[0104] Get the current AC side current , and then determine the current AC side current In the specific interval in FIG5 (a), the control mode corresponding to the interval is adopted, and then the inverter is specifically adjusted according to the modulation strategy and switching mode corresponding to the control mode in Table 1. For example, if the current AC side current is greater than zero but less than the first current regulation threshold When , it can be determined that control mode 1 is required at this time, that is, the modulation strategy PWMA shown in Figure 2 (a) is adopted, and all devices adopt the switching mode 1 shown in Figure 3 (a). The details are as follows:

[0105] If the AC current The absolute value of the current is less than the first current adjustment threshold When , the inverter adopts control mode 1, the modulation strategy adopts PWMA, and the hybrid device adopts switching mode 1 to achieve low loss, so that the SiC device of the inner tube and the anti-parallel diode of the inner tube Si IGBT generate large switching loss and reverse recovery loss respectively.

[0106] If the AC current Greater than or equal to the first current adjustment threshold and is less than or equal to the second current threshold When , the inverter adopts control mode 2, the modulation strategy adopts PWMA, the switching mode of the first inner tube S2 is changed to switching mode 2, and the other hybrid devices still adopt switching mode 1, so that the Si IGBT of the first inner tube S2 and the anti-parallel diode of the Si of the second inner tube S3 generate larger switching loss and reverse recovery loss respectively.

[0107] If the AC current The absolute value of the current is greater than the second current threshold When , the inverter adopts control mode 3, the modulation strategy is PWMB, and the hybrid device adopts switching mode 1, so that the anti-parallel diodes of the Si IGBT of the first outer tube S1 and the first clamp tube S5, or the second outer tube S4 and the Si IGBT of the second clamp tube S6 respectively generate large switching loss and reverse recovery loss.

[0108] If the AC current side Greater than or equal to the second current threshold and is less than or equal to the first current threshold When , the inverter adopts control mode 4, using PWMA, changing the switching mode of the second inner tube S3 to switching mode 2, and the other hybrid devices still use switching mode 1, so that the Si IGBT of the second inner tube S3 and the anti-parallel diode of the Si of the first inner tube S2 generate larger switching loss and reverse recovery loss respectively.

[0109]

[0110] After the specific mode of the current inverter operation is determined, the junction temperature value of the SiC MOSFET of the first inner tube S2 and the junction temperature value of the Si IGBT of the first inner tube S2 are collected respectively, and the first absolute value of the temperature difference between the two can be determined. Then the junction temperature value of the Si IGBT of the first outer tube S1 is collected, and the second absolute value of the temperature difference between the SiC MOSFET of the first inner tube S2 and the Si IGBT of the first outer tube S1 can be determined. Then the first absolute value is compared with the second absolute value for judgment.

[0111] If after comparison, the first absolute value is greater than or equal to the second absolute value, it means that the current hybrid device is not in a junction temperature equilibrium state, and step S303 is executed.

[0112] Step S303: If yes, determining whether the junction temperature of the SiC MOSFET in the first inner tube is greater than or equal to the junction temperature of the Si IGBT in the first inner tube;

[0113] When the first absolute value is greater than the second absolute value, the next step is to determine whether the junction temperature at the first inner tube S2 SiCMOSFET is greater than or equal to the junction temperature at the first inner tube S2 Si IGBT. If yes, step S304 is executed.

[0114] Step S304: If yes, lower the first current adjustment threshold to obtain a first unset current threshold interval;

[0115] Get the current AC side current at the current moment,

[0116] Determining that the AC side current is within the interval range of the first interval of the unset current threshold;

[0117] Determining a control mode of the inverter based on the interval range of the first unset current threshold interval;

[0118] If the junction temperature at the first inner tube S2SiC MOSFET is greater than or equal to the junction temperature at the first inner tube S2 Si IGBT, the first current adjustment threshold is reduced. I xi, and then obtain the first unset current threshold interval. Then, because the current threshold interval has changed at this time, the control mode corresponding to the inverter may change. Therefore, it is necessary to obtain the AC side current at the current moment, and then determine the range of the AC side current in the first unset current threshold interval, and then adjust the control mode of the inverter according to the range. The specific operation process has been described in detail in the previous part of this article, and will not be described in detail here.

[0119] It should be noted that the first current adjustment threshold The reduction range, according to the specific working conditions of the inverter, is generally suitable for adjustment within a small range, and this article does not make specific restrictions on this.

[0120] Step S305: determining whether a cycle end condition is met at the current moment, wherein the cycle condition is that the temperature difference between the first inner tube SiC MOSFET and the first inner tube Si IGBT is zero, and the temperature difference between the first inner tube SiC MOSFET and the first outer tube Si IGBT is also zero;

[0121] After adjusting the first current adjustment threshold After that, it is determined whether the junction temperature between the hybrid devices of the inverter is in a balanced state at the current moment, that is, whether to end the adjustment of the first current adjustment threshold The cycle conditions are as follows: the temperature difference between the SiC MOSFET of the first inner tube S2 and the Si IGBT of the first inner tube S2 is zero, and the temperature difference between the SiC MOSFET of the first inner tube S2 and the Si IGBT of the first outer tube S1 is also zero. The cycle conditions mentioned in the following text are all the cycle conditions mentioned here. In order to avoid repetition, the cycle conditions are only briefly mentioned in the following text for explanation.

[0122] Step S306: If yes, the first current adjustment threshold value after the reduction is determined as the first current threshold value, and the second current adjustment threshold value is determined as the second current threshold value; and the first unadjusted current threshold interval is determined as the adjusted current threshold interval;

[0123] If not, execute step S301.

[0124] If the cycle condition is met, it means that the first current adjustment threshold after the reduction In the first unset current threshold interval, the junction temperature of the inverter is in a balanced state during the hybrid period. At this time, there is no need to adjust the first current adjustment threshold and the second current adjustment threshold. , then the first current adjustment threshold after the reduction is directly Determined as the first current threshold , the second current adjustment threshold Determined as the second current threshold , and then according to the first current threshold and the second current threshold , determine the set current threshold interval, that is, determine the first unset current threshold interval as the set current threshold interval.

[0125] If the loop condition is not met, the first current adjustment threshold is reduced. , as the first current adjustment threshold for the next round of judgment , continue to execute step 301 and repeat the next round of judgment process.

[0126] If the junction temperature at the first inner tube S2 SiC MOSFET is lower than the junction temperature at the first inner tube S2 Si IGBT, that is, if the result of step 303 is no, then the first current adjustment threshold is increased. , and then obtain the increased first current adjustment threshold , and then the second unadjusted current threshold interval can be obtained. It should be noted that each time the first current adjustment threshold is increased When the first current adjustment threshold is increased, it is necessary to ensure Less than or equal to the second current adjustment threshold .

[0127] The AC side current at the current moment is obtained, and it is determined that the AC side current is within the interval range of the second unset current adjustment threshold interval, and then the control mode of the inverter operation is determined according to the interval range of the second unset current threshold interval. Then, it is determined whether the end loop condition is met at the current moment. If the end loop condition is met, since the second current adjustment threshold No change has occurred, therefore, the first current adjustment threshold after the increase The second current regulation threshold may be exceeded , then it is necessary to determine the first current adjustment threshold after the increase Is it less than or equal to the second current adjustment threshold? , if equal, then let the second current adjust the threshold Equal to the first current adjustment threshold , adjust the first current threshold Determined as the first current threshold , then the second unset current adjustment interval is used as the set current threshold interval, as shown in Figure 5 (b), that is, only the first current threshold .

[0128] If the first current adjustment threshold is increased Less than the second current adjustment threshold , then the first current adjustment threshold after the increase Determined as the first current threshold , the second current adjustment threshold Determined as the second current threshold , and determine the second unset current threshold interval as the set current threshold interval.

[0129] If the end cycle condition is not met at this time, the first current adjustment threshold after the increase Determine the first current adjustment threshold for the next acquisition , repeat step 301 to perform a new judgment process.

[0130] If the first absolute value of the temperature difference between the SiC MOSFET and the Si IGBT of the first inner tube S2 is less than the second absolute value of the temperature difference between the first inner tube S2 SiC MOSFET and the first outer tube S1 Si IGBT, then the next step is to determine whether the junction temperature at the first inner tube S2 SiC MOSFET is less than the junction temperature at the first outer tube S1 Si IGBT. If so, the second current adjustment threshold is increased. , and obtain the third unset current threshold interval.

[0131] Then, the AC side current at the current moment is obtained, and it is determined that the AC side current is within the interval range of the third unset current threshold interval. Then, according to the interval range, the control mode of the inverter operation is determined. Then, it is determined whether the end cycle condition is met at the current moment. If so, the first current adjustment threshold is determined as the first current threshold , the increased second current adjustment threshold is determined as the second current threshold , the third unset current threshold interval is determined as the set current threshold interval. If the end loop condition is not met, the increased second current adjustment threshold is used as the second current adjustment threshold to be obtained next time , repeat step S301 to carry out the next round of judgment process.

[0132] If the junction temperature at the first inner tube S2 SiC MOSFET is greater than or equal to the junction temperature at the first outer tube S1 Si IGBT, then the second current adjustment threshold is reduced. At this time, it is necessary to determine whether the lowered second current adjustment threshold is less than the first current adjustment threshold. If so, the first current adjustment threshold is used as the second current adjustment threshold. , the lowered second current adjustment threshold is used as the first current adjustment threshold , a fourth unset current threshold interval is obtained according to the simply adjusted first current adjustment threshold and the second current adjustment threshold.

[0133] Then, the AC side current at the current moment is obtained, and it is determined that the AC side current is within the interval range of the fourth unset current threshold interval, and then the control mode of the inverter operation is determined based on the interval range of the fourth unset current threshold interval. It is determined whether the end loop condition is met at the current moment, and if so, the first current adjustment threshold is determined as the first current threshold , the second current adjustment threshold is determined as the second current threshold , the fourth unset current threshold interval is determined as the set current threshold interval, as shown in FIG5(a).

[0134] If the lowered second current adjustment threshold is greater than or equal to the first current adjustment threshold , then the fifth unset current threshold interval is obtained, and the AC side current at the current moment is obtained to determine whether the AC side current is in the interval range of the fifth unset current threshold interval; then, according to the interval range of the fifth unset current threshold interval, the control mode of the inverter operation is determined.

[0135] Determine whether the end loop condition is met at the current moment. If so, determine whether the lowered second current threshold is equal to the first current adjustment threshold. If so, set the lowered second current adjustment threshold equal to the first current adjustment threshold, and use the first current adjustment threshold as the first current threshold. , the fifth unset current threshold interval is used as the set current threshold interval, and the reduced second current adjustment threshold is determined as the second current threshold The fourth unset current threshold interval is determined as the set current threshold interval, as shown in FIG5(b).

[0136] If the lowered second current adjustment threshold is not equal to the first current adjustment threshold, the first current adjustment threshold is determined as the first current threshold , the second current adjustment threshold is determined as the second current threshold , the fifth unset current threshold interval is used as the set current threshold interval, as shown in FIG5(a).

[0137] If the end-of-cycle condition is not met at the current moment, the lowered second current adjustment threshold As the second current adjustment threshold for the next time , repeat step S301 and repeat the next round of judgment process.

[0138] Step S104: adjusting the control mode of the inverter based on the interval range of the set current threshold interval; wherein the control mode includes a corresponding modulation strategy and a switching mode.

[0139] After the above different current thresholds are determined, two different set current threshold intervals are obtained as shown in FIG5 (a) or FIG5 (b). It should be noted that after the above specific set current threshold intervals are determined, the control mode of the inverter operation is adjusted according to one of the current thresholds.

[0140] For example, if the set current threshold interval of Figure 5 (a) is used, according to Table 1 and the above content, when obtaining the current AC side current After that, if the AC side current Greater than the first current threshold , is less than the second current threshold , then control mode 2 is adopted. According to Table 1, under control mode 2, PWMA modulation strategy is adopted, the first inner tube S2 and the second inner tube S3 adopt switch mode 2, and other devices adopt switch mode 1. At this time, the Si device of the first inner tube S2 generates large switching loss, and the anti-parallel diode of the Si of the second inner tube S3 generates large reverse recovery loss.

[0141] If the set current threshold interval of Figure 5 (b) is used, when the AC side current Greater than the first current threshold When , the control mode 3 is adopted, that is, the PWMB modulation strategy is adopted, and all devices work in the switching mode 1. This will cause the first outer tube S1 device to generate a large switching loss, and the anti-parallel diode Si of the first clamp tube S5 to generate a large reverse recovery loss.

[0142] Simulation verification:

[0143] When the ambient temperature is 25℃ and the heat dissipation environment is good, the threshold temperature is set to 70℃. When the effective value of the AC side current is 29A, the maximum junction temperature can reach 70℃, that is, when the AC side power is greater than 19.2kW, the junction temperature optimization control is performed. Taking the rated power as an example, the junction temperature comparison of different schemes is as follows Figure 6 If the conventional junction temperature optimization method is used to make the maximum junction temperature of S1 close to the maximum junction temperature of S2 SiC MOSFET, the maximum temperature of the converter can be reduced from 82°C to about 60°C. If the method proposed in this application is used, is 49.3A, is 38.8A, Greater than the peak value of the AC current. When changing the switch mode of S2, When the switching mode of S3 is changed, it is changed to the switching mode 2 in FIG5. Then the maximum temperature of the converter can be reduced from 82° C. to about 51° C. The method of the present invention can obtain a lower junction temperature and has a more balanced junction temperature distribution.

[0144] The present application obtains the AC side current at the current moment by judging that the junction temperature value at the current moment exceeds the junction temperature threshold, and then determines the control mode corresponding to the position according to the specific position of the current AC side current in the set current threshold interval, and then adopts the corresponding modulation strategy and switching mode under the control mode to adjust the working mode of the inverter, so as to optimize the junction temperature of the inverter and reduce the junction temperature of the inverter.

[0145] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A junction temperature optimization method for a hybrid device type three-level ANPC inverter, wherein the inverter comprises a first inner tube and a second inner tube, a first outer tube and a second outer tube, a first clamping tube and a second clamping tube, wherein the first inner tube and the second inner tube are formed by connecting Si IGBT and SiC MOSFET in parallel, and the first outer tube, the second outer tube, the first clamping tube and the second clamping tube are all Si IGBT, characterized in that: include: Acquire a current junction temperature value of the first inner tube or the second inner tube; Determining whether the current junction temperature value exceeds a junction temperature threshold; If yes, the current AC side current is obtained, and the range of the set current threshold interval in which the AC side current is located is determined, wherein the set current threshold interval includes a first current threshold and a second current threshold or the first current threshold, and when the set current threshold interval includes the first current threshold and the second current threshold, the first current threshold is less than the second current threshold; Based on the interval range of the set current threshold interval, adjusting the control mode of the inverter operation; wherein the control mode includes a corresponding modulation strategy and a switching mode; The specific process of determining the first current threshold and the second current threshold or the first current threshold is as follows: Step S301: obtaining a first current adjustment threshold corresponding to the first current threshold, and obtaining a second current adjustment threshold corresponding to the second current threshold; Step S302: determining whether a first absolute value of a temperature difference between the SiC MOSFET in the first inner tube and the Si IGBT is greater than or equal to a second absolute value of a temperature difference between the first inner tube SiC MOSFET and the first outer tube Si IGBT; Step S303: If yes, determining whether the junction temperature of the SiC MOSFET in the first inner tube is greater than or equal to the junction temperature of the Si IGBT in the first inner tube; Step S304: If yes, lower the first current adjustment threshold to obtain a first unset current threshold interval; Get the current AC side current at the current moment, Determining that the AC side current is within the interval range of the first unset current threshold interval; Determining a control mode of the inverter based on the interval range of the first unset current threshold interval; Step S305: determining whether a cycle end condition is met at the current moment, wherein the cycle condition is that the temperature difference between the first inner tube SiC MOSFET and the first inner tube Si IGBT is zero, and the temperature difference between the first inner tube SiC MOSFET and the first outer tube Si IGBT is also zero; Step S306: If yes, the lowered first current adjustment threshold is determined as the first current threshold, the second current adjustment threshold is determined as the second current threshold, and the first unadjusted current threshold interval is determined as the adjusted current threshold interval; If not, execute step S301.

2. The method according to claim 1, characterized in that The step of obtaining the current junction temperature value of the first inner tube or the second inner tube includes: When the inverter is initially operated, the first current threshold and the second current threshold are both set to be greater than the AC current peak value, so that the inverter operates according to the initial control mode.

3. The method according to claim 1, characterized in that If the judgment result of step 303 is no, then the first current adjustment threshold is increased to obtain a second unset current threshold interval, and the increased first current adjustment threshold is less than or equal to the second current adjustment threshold; Get the current AC side current at the current moment, Determining that the AC side current is within the interval range of the second unset current threshold interval; Determining a control mode of the inverter based on the interval range of the second unset current threshold interval; Determine whether the end-loop condition is met at the current moment; If so, determining whether the first current adjustment threshold is equal to the second current adjustment threshold; If yes, then set the second current adjustment threshold equal to the first current adjustment threshold, determine the first current adjustment threshold as the first current threshold, and use the second unadjusted current threshold interval as the adjusted current threshold interval; If the first current adjustment threshold is less than the second current adjustment threshold; Then the first current adjustment threshold is determined as the first current threshold, the second current adjustment threshold is determined as the second current threshold; the second unadjusted current threshold interval is determined as the adjusted current threshold interval; If the loop end condition is not met at the current moment, step S301 is executed.

4. The method according to claim 1, characterized in that: The step 302 then includes: If a first absolute value of a temperature difference between the SiC MOSFET and the Si IGBT in the first inner tube is smaller than a second absolute value of a temperature difference between the first inner tube SiC MOSFET and the first outer tube Si IGBT; Then, it is determined whether the junction temperature at the first inner tube SiC MOSFET is lower than the junction temperature at the first outer tube Si IGBT; If yes, then increase the second current adjustment threshold to obtain a third unset current threshold interval; Get the AC side current at the current moment; Determining that the AC side current is within the interval range of the third unset current threshold interval; Determining a control mode of the inverter operation based on an interval range of the third unset current threshold interval; Determine whether the end-loop condition is met at the current moment; If yes, the first current adjustment threshold is determined as the first current threshold, the second current adjustment threshold is determined as the second current threshold; the third unadjusted current threshold interval is determined as the adjusted current threshold interval; If not, execute step S301.

5. The method according to claim 4, characterized in that After the step of determining whether the junction temperature of the SiC MOSFET in the first inner tube is lower than the junction temperature of the Si IGBT in the first outer tube, the method further includes: If not, lowering the second current adjustment threshold; Determining whether the lowered second current adjustment threshold is less than the first current adjustment threshold; If yes, the first current adjustment threshold is used as the second current adjustment threshold, and the reduced second current adjustment threshold is used as the first current adjustment threshold to obtain a fourth unset current threshold interval; Get the current AC side current at the current moment, Determining that the AC side current is within the interval range of the fourth unset current threshold interval; Determining a control mode of operation of the inverter based on an interval range of the fourth unset current threshold interval; Determine whether the end-loop condition is met at the current moment; If yes, the first current adjustment threshold is determined as the first current threshold, the second current adjustment threshold is determined as the second current threshold; the fourth unadjusted current threshold interval is determined as the adjusted current threshold interval; If the loop end condition is not met at the current moment, step S301 is executed.

6. The method according to claim 5, characterized in that: The step of determining whether the lowered second current adjustment threshold is less than the first current adjustment threshold comprises: If not, the fifth unset current threshold interval is obtained; Get the AC side current at the current moment; Determining that the AC side current is within the interval range of the fifth unset current threshold interval; Determining a control mode of the inverter operation based on an interval range of the fifth unset current threshold interval; Determine whether the end-loop condition is met at the current moment; If so, determining whether the lowered second current adjustment threshold is equal to the first current adjustment threshold; If yes, then setting the lowered second current adjustment threshold equal to the first current adjustment threshold, taking the first current adjustment threshold as the first current threshold, and taking the fifth unadjusted current threshold interval as the adjusted current threshold interval; If not, the first current adjustment threshold is determined as the first current threshold, the second current adjustment threshold is determined as the second current threshold, and the fifth unadjusted current threshold interval is used as the adjusted current threshold interval; If the loop end condition is not met at the current moment, step S301 is executed.

7. The method according to claim 1, characterized in that The step of adjusting the control mode of the inverter operation based on the set current threshold interval includes: The control mode corresponding to the set current threshold interval is determined, and the inverter is operated according to the modulation strategy and switching mode corresponding to the control mode.

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