Thermal management method and device for power devices in a power converter

Abstract

Embodiments of the present invention relate to the field of power electronics and its measurement technologies, and particularly to a thermal management method and device for power devices in a power converter. The method includes: collecting the stable value of the bus voltage and the AC current values of each phase of the power converter to obtain the operating voltage and current values of each power device, and obtaining the limited value of the switching frequency of the power device based on the voltage and current values; calculating the real-time junction temperature of each power device according to the stable value of the bus voltage and the AC current values of each phase; calculating the bridge arm switching frequency value according to the junction temperature, and inputting the bridge arm switching frequency value into a limiter for limiting according to the limited value; adjusting the switching frequency of the power device according to the switching frequency value output by the limiter. The technical solution of the embodiments of the present invention solves the problems of suppressing high-frequency fluctuations of device temperature and temperature imbalance between devices in the converter through the thermal management of power devices in the power converter.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of power electronics and its measurement, and particularly to a thermal management method and device for power devices in a power converter. Background Art

[0002] Power converters have a wide range of applications in industry and life. With the rapid development of power electronics technology, new energy systems centered on power electronic converters have gradually become a new driving force for economic development and industrial revolution, attracting extensive attention. According to the reliability research report of power electronic systems, the failure rate of power electronic converters is the highest in various application scenarios such as wind power generation, photovoltaic power generation, hybrid electric vehicles, and EMU traction converters. The operation reliability of power electronic converters directly affects the safe and stable operation of the entire system. Power electronic devices are the core components of power converters and are also the components most likely to fail in converters. The failure of power electronic devices will directly lead to the failure of the converter, and their reliability directly affects the safe and stable operation of the converter.

[0003] Thermal stress is the main factor affecting the failure degradation of power electronic devices and the safe operation of the system. Among various failure factors, about 55% of the failures of power electronic systems are mainly induced by temperature factors, and thermal stress is the most prominent part of the stress borne by power electronic devices. The on-state loss and switching loss generated by power electronic devices during actual operation will cause the devices to suffer frequent thermal stress.

[0004] Taking IGBT devices as an example, with the power fluctuation and the change of the external environment, the IGBT devices are subjected to frequent thermal cycle shocks and temperature fluctuations, which are important reasons for the failure of power devices. The thermal stress borne by IGBT devices mainly includes the average junction temperature and the junction temperature fluctuation. Existing research shows that the life of IGBT devices is more affected by the junction temperature fluctuation. The multi-layer structure inside the IGBT device module and the mismatch of the thermal expansion coefficients between different materials will cause alternating thermal stress. Long-term exposure to stress will cause the IGBT module to age, and thus the life is shortened. The greater the temperature fluctuation, the faster the device ages, and there is a certain cumulative effect. On the other hand, a converter usually contains multiple IGBT devices. For a three-phase converter, the load of each phase is relatively independent, which inevitably leads to unbalanced three-phase loads. In addition, for the IGBT modules of the three-phase bridge arms of a three-phase converter, their thermal resistances are very difficult to be exactly the same. The unbalanced three-phase loads and the uneven thermal resistances cause differences in the thermal stress of the three-phase IGBT half-bridge modules, resulting in the thermal short-board effect of the system. Summary of the Invention

[0005] Based on the above situation of the prior art, the purpose of the embodiments of the present invention is to provide a thermal management method and device for power devices in a power converter. By performing thermal management on power electronic devices, especially by suppressing the fluctuation of the junction temperature and eliminating the thermal short - board effect in the converter system to make the system thermal stress tend to be balanced, the service life of power electronic power devices is extended, and the reliability of the power converter is improved.

[0006] To achieve the above - mentioned purpose, according to one aspect of the present invention, there is provided a thermal management method for power devices in a power converter, and the method includes:

[0007] S102. Collect the stable value of the bus voltage of the power converter and the AC current values of each phase, so as to obtain the working voltage values and current values of each power device, and obtain the limited amplitude value of the switching frequency of the power device according to the voltage value and current value;

[0008] S104. Calculate the real - time junction temperature of each power device according to the stable value of the bus voltage and the AC current values of each phase;

[0009] S106. Judge whether the amplitude fluctuation of the junction temperature of each power device exceeds a first threshold. If it exceeds, calculate a first switching frequency value; at the same time, judge whether the difference between the maximum junction temperature and the minimum junction temperature of the power devices in each phase bridge arm exceeds a second threshold. If it exceeds, calculate a second switching frequency value;

[0010] S108. Obtain the bridge - arm switching frequency value according to the first switching frequency value and the second switching frequency value, and input the bridge - arm switching frequency value into a limiter to perform limiting according to the limited amplitude value;

[0011] S110. Adjust the switching frequency of the power device according to the switching frequency value output by the limiter.

[0012] Further, obtaining the limited amplitude value of the switching frequency of the power device according to the voltage value and current value includes:

[0013] Obtain the limited amplitude value of the switching frequency of the power device by looking up a table according to the voltage value and current value.

[0014] Further, the following steps are adopted to calculate the real - time junction temperature of each power device:

[0015] Determine the junction - temperature monitoring moment according to the direction of each - phase current and the initial state and secondary state of the half - bridge arm where it is located;

[0016] Monitor the DC bus voltage at the junction - temperature monitoring moment as the DC - bus ringing peak voltage corresponding to the power device;

[0017] Determine the junction temperature of the power device based on the DC - bus ringing peak voltage, the stable value of the DC bus voltage, and the phase current.

[0018] Further, the following method is adopted to calculate the amplitude of the junction temperature fluctuation of the power device:

[0019] The amplitude of the junction temperature fluctuation of the power device is obtained by subtracting the minimum value of the junction temperature from the maximum value of the junction temperature of the power device within a predetermined period; and,

[0020] The difference between the maximum junction temperature and the minimum junction temperature of the power devices of each phase leg is compared using a hysteresis loop.

[0021] Further, step S106 further includes:

[0022] If the amplitude of the junction temperature fluctuation of each power device exceeds the first threshold, the PID method is used to calculate the switching frequency value at different load currents as the first switching frequency value;

[0023] If the amplitude of the junction temperature fluctuation of each power device does not exceed the first threshold, return to step S104 to continue the calculation.

[0024] Further, step S106 further includes:

[0025] If the difference between the maximum junction temperature and the minimum junction temperature of the power devices of each phase leg exceeds the second threshold, the PID method is used to calculate the switching frequency value of each phase leg as the second switching frequency value;

[0026] If the difference between the maximum junction temperature and the minimum junction temperature of the power devices of each phase leg does not exceed the second threshold, return to step S104 to continue the calculation.

[0027] Further, the switching frequency value of the phase leg is calculated according to the following formula :

[0028]

[0029] Wherein, is the relative multiple of the first switching frequency value, is the relative multiple of the second switching frequency value, is the base frequency.

[0030] Further, adjusting the switching frequency of the power device according to the switching frequency value output by the limiter further includes:

[0031] When the junction temperature difference of the power device exceeds the second threshold, the switching frequency of the high-temperature power device is preferentially reduced;

[0032] When reducing the switching frequency of the high-temperature power device causes the total harmonic distortion THD of the output current to be greater than the third threshold, the switching frequency of the low-temperature power device is increased.

[0033] According to a second aspect of the present invention, there is provided a thermal management device for power devices in a power converter, comprising:

[0034] A voltage and current acquisition module for acquiring the stable value of the bus voltage of the power converter and the AC current values of each phase, so as to obtain the working voltage values and current values of each power device;

[0035] A limit value calculation module for calculating the limit value of the switching frequency of the power device according to the voltage value and the current value;

[0036] A real-time junction temperature calculation module for obtaining the real-time junction temperature of each power device according to the stable value of the bus voltage and the AC current values of each phase;

[0037] A switching frequency value calculation module for determining whether the fluctuation amplitude of the junction temperature of each power device exceeds a first threshold. If it exceeds, a first switching frequency value is obtained through calculation; at the same time, it is determined whether the difference between the maximum junction temperature and the minimum junction temperature of the power devices of each phase leg exceeds a second threshold. If it exceeds, a second switching frequency value is obtained through calculation;

[0038] A limiting module for obtaining the leg switching frequency value according to the first switching frequency value and the second switching frequency value, and inputting the leg switching frequency value into a limiter to perform limiting according to the limit value;

[0039] A switching frequency adjustment module for adjusting the switching frequency of the power device according to the switching frequency value output by the limiter.

[0040] According to a third aspect of the present invention, there is provided an electronic device, comprising:

[0041] A processor; and

[0042] A memory having executable code stored thereon, and when the executable code is executed by the processor, the method described in the first aspect of the present invention is executed.

[0043] In summary, the embodiments of the present invention provide a method and device for thermal management of power devices in a power converter. The method includes: collecting the stable value of the bus voltage of the power converter and the AC current values of each phase, so as to obtain the working voltage values and current values of each power device, and obtaining the limited value of the switching frequency of the power device according to the voltage value and current value; calculating the real-time junction temperature of each power device according to the stable value of the bus voltage and the AC current values of each phase; judging whether the fluctuation amplitude of the junction temperature of each power device exceeds a first threshold, if it exceeds, calculating a first switching frequency value through calculation; at the same time, judging whether the difference between the maximum junction temperature and the minimum junction temperature of the power devices of each phase bridge arm exceeds a second threshold, if it exceeds, calculating a second switching frequency value through calculation; obtaining the bridge arm switching frequency value according to the first switching frequency value and the second switching frequency value, and inputting the bridge arm switching frequency value into a limiter to perform limiting according to the limited value; adjusting the switching frequency of the power device according to the switching frequency value output by the limiter. The technical solution of the embodiments of the present invention solves the problems of suppressing high-frequency fluctuations of device temperatures in the converter and temperature imbalance between devices through thermal management of power devices in the power converter. By comprehensively monitoring the temperatures of each power device in the converter, and then based on the temperature information of all power devices, evaluating the thermal stress situation in the converter. And by adjusting the switching frequency of the power device, that is, the method of active thermal management, the temperature of the power device is adjusted, so as to achieve high-frequency suppression of the temperature fluctuation of the power device, balance the temperatures of each power device, improve the short-board effect of thermal stress, and improve the reliability of the converter system. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a schematic topological structure diagram of a three-phase half-bridge inverter;

[0045] Figure 2 is a schematic diagram of IGBT power loss of an IGBT module at different switching frequencies;

[0046] Figure 3 is a flowchart of the method for thermal management of power devices in the power converter provided by the embodiments of the present invention;

[0047] Figure 4 is the SPWM carrier waveform after suppressing high-frequency fluctuations of the junction temperature and adjusting;

[0048] Figure 5 is the SPWM carrier waveform after adjusting to improve the temperature consistency of each phase bridge arm;

[0049] Figure 6 is a block diagram of the composition of the device for thermal management of power devices in the power converter provided by the embodiments of the present invention;

[0050] Figure 7It is a schematic structural diagram of an electronic device provided by an embodiment of the present invention. Detailed implementation manners

[0051] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the detailed implementation manners and with reference to the accompanying drawings. It should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily obscuring the concepts of the present invention.

[0052] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in one or more embodiments of the present invention should be the ordinary meanings understood by those of ordinary skill in the art to which the present disclosure belongs. The terms "first", "second" and similar terms used in one or more embodiments of the present invention do not denote any order, quantity or importance, but are only used to distinguish different components. The terms such as "including" or "comprising" mean that the elements or items appearing before this term cover the elements or items listed after this term and their equivalents, without excluding other elements or items. The terms such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect.

[0053] Thermal management methods can be mainly divided into internal thermal management and external thermal management according to their control objects. Taking IGBT power devices as an example, the main idea of internal thermal management is to actively change the losses of the IGBT module to regulate the junction temperature of the IGBT. Typical thermal management methods include changing the switching frequency, regulating the IGBT dynamic process, and changing the system modulation, etc. The control method of regulating the junction temperature by changing the switching frequency is usually used for suppressing the junction temperature fluctuation, but mainly considers the second-level fluctuation and lacks technical solutions for higher-frequency temperature fluctuations. Regulating the IGBT dynamic process mainly refers to controlling the switching losses by regulating the switching process, and then controlling the junction temperature of the device. However, this method requires a complex gate drive circuit and has an impact on the electromagnetic interference of the circuit. The thermal management method of changing the system modulation scheme is mainly aimed at converters with redundant control strategies and is not applicable to all converters. The main idea of the external thermal management method is to control the junction temperature of the IGBT by regulating the external heat dissipation conditions. By regulating the external heat dissipation conditions to smooth the low-frequency junction temperature fluctuation caused by load fluctuation during the operation of the IGBT, the results show that when the load current fluctuates within the range of 60%-100% of the rated value, reducing the junction temperature fluctuation by about 60% can increase the life of the IGBT by about 69 times. However, the method of realizing thermal management by controlling the heat dissipation conditions is difficult to suppress the high-frequency temperature fluctuation of the system.

[0054] Existing thermal management methods still have some deficiencies. In terms of smoothing the junction temperature fluctuations of IGBTs, most current research remains at the level of suppressing low-frequency fluctuations, and there is a lack of research on suppressing high-frequency temperature fluctuations. In an actual converter, during the operation of the device module, the temperature fluctuation frequency is affected by the load current. For example, when dealing with a load current with power frequency fluctuations, the junction temperature fluctuation frequency is the same as the power frequency. However, the existing technology has not yet targeted the suppression of junction temperature fluctuations at power frequency (50 Hz). In addition, for an actual converter, it is very difficult to ensure that the thermal stresses of each device are exactly the same. On the one hand, it is very difficult to make the processing power of each device exactly the same throughout the cycle, such as the operating conditions under unbalanced loads. On the other hand, the heat dissipation conditions of different devices in the same converter cannot be exactly the same, especially the obvious disadvantage of poor temperature uniformity performance of liquid-cooled radiators. If there is a large temperature difference between IGBTs, it will cause stress imbalance in the entire converter, accelerate the aging of some devices, resulting in a decrease in the overload capacity of the entire converter, an increase in the risk of failure, and a decrease in reliability. However, there is currently little research on thermal management for the unbalanced thermal stress situation of each IGBT. The thermal management method provided by the embodiments of the present invention solves the problems of suppressing high-frequency temperature fluctuations of devices in the converter and temperature imbalance between devices.

[0055] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings. In the embodiments of the present invention, a three-phase half-bridge inverter including 6 IGBT devices is taken as an example for illustration. Figure 1 The schematic diagram of the topology structure of the three-phase half-bridge inverter is shown. And this exemplary embodiment is only used for illustrative explanation or interpretation of the principle of the present invention. The present invention can also be applied to other forms of power converters and power devices, including but not limited to single-phase or three-phase PWM rectifiers, single-phase or three-phase PWM inverters, half-bridge topologies, full-bridge topologies, bipolar power devices, MOSFET power devices, etc.

[0056] As Figure 1 shown, the three-phase half-bridge inverter composed of 6 IGBTs has a DC input. The driving signals of each IGBT are controlled by SPWM to generate three-phase alternating current, and then connected to an induction motor load. For IGBT devices, their losses mainly include turn-on losses, turn-off losses, and conduction losses. The power device passes through tens of amperes or even hundreds or thousands of amperes of current in the conduction state, and the conduction loss is extremely large. The voltage-current overlap during switching indicates that it passes through the amplification region, and certain switching losses will also be formed. The switching losses of IGBTs operating in the hard-switching mode are more prominent. Therefore, the higher the switching frequency, the greater the corresponding IGBT switching loss, and thus the greater the total loss; the lower the switching frequency, the smaller the corresponding IGBT switching loss, and thus the smaller the total loss. The losses of the power device can be expressed as:

[0057]

[0058] Among them, is the switching frequency, is the loss during each turn-on process, is the loss during each turn-off process. is the on-state loss power of the device. Among them is mainly affected by the load current. can be expressed as:

[0059]

[0060] can be expressed as:

[0061]

[0062] Among them represents the start time of the device turn-on process, represents the end time of the device turn-on process; represents the start time of the device turn-off process, represents the end time of the device turn-off process.

[0063] For a three-phase converter, the switching frequency is adjusted. Through frequency sweep simulation using thermal simulation software, the operating conditions are set as a bus voltage of 400 V and a rms line current of 100 A. The IGBT power losses of the IGBT module at different switching frequencies are as Figure 2 shown. From Figure 2 it can be seen that the turn-on loss of the IGBT shows a linear relationship with the turn-off loss and the switching frequency, and the on-state loss is not affected by the switching frequency. Therefore, by changing the switching frequency of the device, the switching loss power of the device can be changed, and thus the linear control of the device power loss can be achieved. The linear relationship between the power loss and the switching frequency makes the thermal management method based on switching frequency adjustment more robust.

[0064] Based on the above analysis, the present invention proposes a converter thermal management method based on switching frequency adjustment, Figure 3 is a flowchart of a thermal management method 100 for power devices in a power converter provided by an embodiment of the present invention, as Figure 3 shown, and the method includes the following steps:

[0065] S102. Collect the stable value of the bus voltage of the power converter and the AC current values of each phase, so as to obtain the operating voltage values and current values of each power device, and calculate the limit value of the switching frequency of the power device according to the voltage value and current value. First, monitor the voltage values and current values of the power converter and its power devices. Since adjusting the switching frequency of the bridge arm will affect the total harmonic distortion (hereinafter referred to as "THD") of the converter output, and the degree of influence is closely related to the voltage and current of the converter, therefore, after obtaining the voltage values and current values of the power converter and its power devices, first obtain the limit value of the switching frequency, and the result can be reserved for subsequent switching frequency adjustment. The calculation expression of the limit value can be expressed as:

[0066]

[0067]

[0068] Wherein, represents the maximum allowable switching frequency, represents the minimum allowable switching frequency. The minimum allowable switching frequency depends on the cut-off frequency setting of the filter and the output performance of the system (the spectrum of the output signal); the maximum allowable switching frequency depends on the IGBT device performance and the stray parameters of the circuit, etc. Since the operating voltage and operating current of the power device will affect the loss of the device, on the premise of ensuring that the device operates within the safe operating area, generally, the greater the operating voltage and operating current of the power device, the smaller the allowable maximum limit value (for example, inversely proportional to the product of the operating voltage and current), and the specific limit value can be obtained by looking up a table.

[0069] S104. Calculate the real-time junction temperature of each power device according to the stable value of the bus voltage and the AC current values of each phase. The following steps can be used for the calculation:

[0070] Determine the junction temperature monitoring moment according to the direction of each phase current and the initial state and secondary state of the half-bridge arm where it is located;

[0071] Monitor the DC bus voltage at the junction temperature monitoring moment as the peak voltage of the DC bus ringing corresponding to the power device;

[0072] Determine the junction temperature of the power device based on the peak voltage of the DC bus ringing, the stable value of the DC bus voltage, and the phase current.

[0073] The specific calculation method of the real-time junction temperature in this step has been published in the applicant's prior Chinese patent (CN202110373619.7), and the authorization announcement number is CN113098314B, and its repeated description will be omitted here.

[0074] S106. Determine whether the temperature fluctuation amplitude of each power device exceeds a first threshold. If it exceeds, calculate a first switching frequency value through calculation. At the same time, determine whether the difference between the maximum junction temperature and the minimum junction temperature of the power devices in each phase arm exceeds a second threshold. If it exceeds, calculate a second switching frequency value through calculation. If the temperature fluctuation amplitude of each power device exceeds the first threshold, use the PID method to calculate the switching frequency value under different load currents as the first switching frequency value. If the temperature fluctuation amplitude of each power device does not exceed the first threshold, return to step S104 to continue the calculation. If the difference between the maximum junction temperature and the minimum junction temperature of the power devices in each phase arm exceeds the second threshold, use the PID method to calculate the switching frequency value of each phase arm as the second switching frequency value. If the difference between the maximum junction temperature and the minimum junction temperature of the power devices in each phase arm does not exceed the second threshold, return to step S104 to continue the calculation.

[0075] After obtaining the junction temperatures of each device in the power converter, calculate two thermal stresses. One is the temperature fluctuation amplitude of a single IGBT, and the other is the difference between the maximum junction temperature and the minimum junction temperature among the device temperatures of each phase arm. A hysteresis loop is introduced for comparison. The temperature fluctuation amplitude of a single IGBT can be calculated in the following way: Subtract the minimum junction temperature from the maximum junction temperature of the power device within a predetermined period to obtain the temperature fluctuation amplitude of the power device. This predetermined period can be set according to actual needs. Compare the difference between the maximum junction temperature and the minimum junction temperature of the power devices in each phase arm using a hysteresis loop. Introducing a hysteresis loop comparison can reduce the problem of frequent switching of the switching frequency and increase the system stability.

[0076] On the one hand, if the temperature fluctuation amplitude of a single IGBT does not exceed a preset first threshold, continue to monitor the junction temperature. When the temperature fluctuation amplitude of a single IGBT exceeds the preset first threshold, calculate the switching frequency value under different load currents through the PID algorithm (expressed in relative multiples) to achieve the switching frequency adjustment corresponding to the load current fluctuation. The adjustment principle is that the larger the load current, the lower the switching frequency; the smaller the load current, the higher the switching frequency, so as to suppress the temperature fluctuation. Adjust the switching frequency by adjusting the SPWM triangular wave carrier frequency. The adjusted SPWM carrier waveform is as Figure 4 shown, Figure 4 where the sine curve represents the modulation wave consistent with the output fundamental frequency, and the triangular wave curve represents the carrier consistent with the switching frequency. On the other hand, compare the maximum and minimum values of the junction temperatures of each IGBT, and then introduce a hysteresis loop for comparison. If the difference between the maximum junction temperature and the minimum junction temperature of the power devices in each phase arm does not exceed a preset second threshold, continue to monitor the junction temperature. If the difference between the maximum junction temperature and the minimum junction temperature of the power devices in each phase arm exceeds the preset second threshold, calculate the switching frequency value of each phase arm through the PID algorithm (expressed in relative multiples) (indicated), to achieve improvement in temperature consistency based on switching frequency regulation. Among them, the first threshold and the second threshold can be determined by the switching frequency switching frequency, for example, can be set to 5% of the maximum temperature difference of the system. For example, the temperature of the IGBT in phase B is lower than that in phases A and C. To improve the temperature consistency of each phase leg, the switching frequency of phase B is adjusted to , and the adjusted SPWM carrier waveform is as Figure 5 shown.

[0077] S108. Obtain the leg switching frequency value according to the first switching frequency value and the second switching frequency value, and input the leg switching frequency value into a limiter to perform limiting according to the limit value. The limit value of the limiter is obtained by the calculation in step S102. The switching frequency of each leg is determined by the relative multiple under the suppression of the junction temperature fluctuation and the relative multiple to improve the temperature consistency of the leg jointly determined, and the relative multiple can be obtained by dividing the first switching frequency value by the base frequency; the relative multiple can be obtained by dividing the second switching frequency value by the base frequency; where the base frequency is the carrier frequency without thermal management and switching frequency regulation, for example, generally taken as 10 kHz. Therefore, the leg switching frequency value can be calculated according to the following formula:

[0078]

[0079] where, is the relative multiple of the first switching frequency value, is the relative multiple of the second switching frequency value, is the base frequency.

[0080] S110. Adjust the switching frequency of the power device according to the switching frequency value output by the limiter. Adjust the switching frequency of the actual power device to the switching frequency value after limiting, so as to achieve the suppression of the junction temperature fluctuation of a single power device and the improvement of the temperature consistency of power devices in different phases. During the adjustment process, when there is a temperature difference in the IGBT, it is preferred to consider reducing the switching frequency of the high-temperature IGBT, which can reduce the power loss of the entire converter; when reducing the switching frequency of the high-temperature IGBT makes the system output performance deteriorate, consider increasing the switching frequency of the low-temperature IGBT. "The system output performance deteriorates" means that the total harmonic distortion THD of the output current becomes larger. For example, when the total harmonic distortion THD of the output current is greater than the third threshold, it is regarded as the system output performance deteriorating. Generally speaking, the total harmonic distortion THD is required not to exceed 10%.

[0081] After that, it is possible to return to step S102 to continue monitoring data such as the voltage value and current value of the power converter, and perform the next round of thermal management.

[0082] An embodiment of the present invention further provides a thermal management device for power devices in a power converter. Figure 6 The block diagram of the thermal management device is shown in FIG. The device includes:

[0083] A voltage and current acquisition module 601, configured to acquire the stable value of the bus voltage and the AC current values of each phase of the power converter, so as to obtain the working voltage values and current values of each power device;

[0084] A limit value calculation module 602, configured to obtain the limit value of the switching frequency of the power device according to the voltage value and the current value;

[0085] A real-time junction temperature calculation module 603, configured to calculate the real-time junction temperature of each power device according to the stable value of the bus voltage and the AC current values of each phase;

[0086] A switching frequency value calculation module 604, configured to determine whether the fluctuation amplitude of the junction temperature of each power device exceeds a first threshold. If it exceeds, a first switching frequency value is obtained through calculation; at the same time, it is determined whether the difference between the maximum junction temperature and the minimum junction temperature of the power devices in each phase arm exceeds a second threshold. If it exceeds, a second switching frequency value is obtained through calculation;

[0087] A limiting module 605, configured to obtain the arm switching frequency value according to the first switching frequency value and the second switching frequency value, and input the arm switching frequency value into a limiter to perform limiting according to the limit value;

[0088] A switching frequency adjustment module 606, configured to adjust the switching frequency of the power device according to the switching frequency value output by the limiter.

[0089] The specific process of each module in the thermal management device provided by this embodiment of the present invention to implement its functions is the same as each step of the thermal management method provided by the above embodiment of the present invention. Therefore, the repeated description thereof will be omitted here.

[0090] Figure 7 The structural schematic diagram of an electronic device provided by an embodiment of the present invention is shown. As Figure 7 shown, the electronic device 700 includes: one or more processors 701 and a memory 702; and computer program instructions stored in the memory 702, and when the computer program instructions are run by the processor 701, the processor 701 is caused to execute the thermal management method as described in any of the above embodiments. The processor 701 may be a central processing unit (CPU) or other forms of processing units with data processing capabilities and / or instruction execution capabilities, and may control other components in the electronic device to perform desired functions.

[0091] The memory 702 may include one or more computer program products, and the computer program products may include various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. Volatile memory may include, for example, random access memory (RAM) and / or cache memory, etc. Non-volatile memory may include, for example, read-only memory (ROM), hard disk, flash memory, etc. One or more computer program instructions may be stored on the computer-readable storage medium, and the processor 701 may run the program instructions to implement the steps in the thermal management methods of the various embodiments of the present invention described above and / or other desired functions.

[0092] In some embodiments, the electronic device 700 may further include: an input device 703 and an output device 704, and these components are interconnected through a bus system and / or other forms of connection mechanisms ( Figure 7 not shown in the figure). For example, when the electronic device is a stand-alone device, the input device 703 may be a communication network connector for receiving the collected input signals from an external removable device. In addition, the input device 703 may further include, for example, a keyboard, a mouse, a microphone, etc. The output device 704 may output various information to the outside, and may include, for example, a display, a speaker, a printer, and a communication network and its connected remote output devices, etc.

[0093] In addition to the above methods and devices, an embodiment of the present invention may also be a computer program product, including computer program instructions, and when the computer program instructions are run by a processor, the processor is caused to execute the steps in the thermal management method of any of the above embodiments.

[0094] The computer program product may be written in any combination of one or more programming languages to write program code for performing the operations of the embodiments of the present invention. The programming languages include object-oriented programming languages, such as Java, C++, etc., and also include conventional procedural programming languages, such as the "C" language or similar programming languages. The program code may be executed entirely on the user's computing device, partially on the user's device, executed as an independent software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server.

[0095] In addition, an embodiment of the present invention may also be a computer-readable storage medium, on which computer program instructions are stored, and when the computer program instructions are run by a processor, the processor is caused to execute the steps in the thermal management methods of the various embodiments of the present invention.

[0096] A computer-readable storage medium may adopt any combination of one or more readable media. The readable media may be a readable signal medium or a readable storage medium. The readable storage medium may include, for example, but is not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination of the above. More specific examples (a non-exhaustive list) of the readable storage medium include: an electrical connection having one or more wires, a portable disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above.

[0097] It should be understood that the processor in the embodiments of the present invention may be a central processing unit (CPU), and this processor may also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or this processor may also be any conventional processor, etc.

[0098] In summary, the embodiments of the present invention relate to a thermal management method and device for power devices in a power converter. The method includes: collecting the stable value of the bus voltage and the AC current values of each phase of the power converter to obtain the operating voltage values and current values of each power device, and obtaining the limited value of the switching frequency of the power device according to the voltage value and current value; calculating the real-time junction temperature of each power device according to the stable value of the bus voltage and the AC current values of each phase; determining whether the fluctuation amplitude of the junction temperature of each power device exceeds a first threshold. If it exceeds, a first switching frequency value is obtained through calculation; at the same time, it is determined whether the difference between the maximum junction temperature and the minimum junction temperature of the power devices of each phase leg exceeds a second threshold. If it exceeds, a second switching frequency value is obtained through calculation; obtaining the switching frequency value of the phase leg according to the first switching frequency value and the second switching frequency value, and inputting the switching frequency value of the phase leg into a limiter to perform limiting according to the limited value; adjusting the switching frequency of the power device according to the switching frequency value output by the limiter. The technical solution of the embodiments of the present invention solves the problem of high-frequency fluctuation of the junction temperature of devices in the power converter, especially the junction temperature fluctuation at the industrial frequency of 50 Hz. In addition, it also solves the problem of unbalanced thermal stress of the power devices of the entire power converter, reduces the failure risk of the converter, verifies the life of the converter and the devices, and enhances the reliability of the converter. The technical solution of the embodiments of the present invention has very little impact on the performance of the system output current when switching the switching frequency. There is no ringing or obvious transient process at the moment of switching the switching frequency of the output current, which is very smooth and natural. The use of asynchronous switching frequencies has less impact on the steady-state output THD of the system.

[0099] It should be understood that the discussion of any above embodiments is only exemplary and is not intended to imply that the scope of the present invention (including the claims) is limited to these examples. Under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of one or more embodiments of the present invention as described above. For the sake of brevity, they are not provided in detail. The above specific embodiments of the present invention are only used for exemplary illustration or explanation of the principle of the present invention, and do not constitute a limitation to the present invention. Therefore, any modifications, equivalent replacements, improvements, etc. made without departing from the spirit and scope of the present invention shall be included within the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modification examples falling within the scope and boundary of the appended claims, or equivalent forms of such scope and boundary.

Claims

1. A thermal management method for power devices in a power converter, characterized in that, The method includes: S102. Collect the stable value of the bus voltage of the power converter and the AC current values of each phase, so as to obtain the working voltage values and current values of each power device, and obtain the limit value of the switching frequency of the power device according to the voltage value and the current value; S104. Calculate the real-time junction temperature of each power device according to the stable value of the bus voltage and the AC current values of each phase, including: Determine the junction temperature monitoring moment according to the direction of each phase current and the initial state and secondary state of the corresponding half-bridge arm; Monitor the DC bus voltage at the junction temperature monitoring moment as the peak voltage of the DC bus ringing corresponding to the power device; Determine the junction temperature of the power device based on the peak voltage of the DC bus ringing, the stable value of the DC bus voltage, and the phase current; S106. Judge whether the fluctuation range of the junction temperature of each power device exceeds the first threshold. If it exceeds, calculate the first switching frequency value through calculation; at the same time, judge whether the difference between the maximum junction temperature and the minimum junction temperature of the power devices of each phase bridge arm exceeds the second threshold. If it exceeds, calculate the second switching frequency value through calculation; If the fluctuation range of the junction temperature of each power device exceeds the first threshold, use the PID method to calculate the switching frequency value under different load currents as the first switching frequency value; If the fluctuation range of the junction temperature of each power device does not exceed the first threshold, return to step S104 to continue the calculation; If the difference between the maximum junction temperature and the minimum junction temperature of the power devices of each phase bridge arm exceeds the second threshold, use the PID method to calculate the switching frequency value of each phase bridge arm as the second switching frequency value; If the difference between the maximum junction temperature and the minimum junction temperature of the power devices of each phase bridge arm does not exceed the second threshold, return to step S104 to continue the calculation; S108. Obtain the bridge arm switching frequency value according to the first switching frequency value and the second switching frequency value, and input the bridge arm switching frequency value into the limiter for limiting according to the limit value; calculate the bridge arm switching frequency value f according to the following formula: f = a·b·f s where a is the relative multiple of the first switching frequency value, b is the relative multiple of the second switching frequency value, and f s is the base frequency; S110. Adjust the switching frequency of the power device according to the switching frequency value output by the limiter.

2. The method according to claim 1, characterized in that Obtain the limit value of the switching frequency of the power device according to the voltage value and the current value, including: Obtain the limit value of the switching frequency of the power device by looking up a table according to the voltage value and the current value.

3. The method according to claim 2, wherein Adopt the following method to calculate the fluctuation range of the junction temperature of the power device: Obtain the fluctuation range of the junction temperature of the power device by subtracting the minimum junction temperature from the maximum junction temperature of the power device within a predetermined period; and Adopt a hysteresis loop to compare the difference between the maximum junction temperature and the minimum junction temperature of the power devices of each phase bridge arm.

4. The method according to claim 3, wherein Adjust the switching frequency of the power device according to the switching frequency value output by the limiter, and further include: When the junction temperature difference of the power device exceeds the second threshold, preferentially reduce the switching frequency of the high-temperature power device; When reducing the switching frequency of the high-temperature power device causes the total harmonic distortion THD of the output current to be greater than the third threshold, increase the switching frequency of the low-temperature power device.

5. A thermal management device for power devices in a power converter, characterized in that, Include: A voltage and current acquisition module for collecting the stable value of the bus voltage of the power converter and the AC current values of each phase, so as to obtain the working voltage values and current values of each power device; The limit value calculation module is used to calculate the limit value of the switching frequency of the power device according to the voltage value and the current value; The real-time junction temperature calculation module obtains the real-time junction temperature of each power device according to the stable value of the bus voltage and the AC current values of each phase, including: Determining the junction temperature monitoring moment according to the direction of each phase current and the initial state and secondary state of the corresponding half-bridge arm; Monitoring the DC bus voltage at the junction temperature monitoring moment as the peak voltage of the DC bus ringing corresponding to the power device; Determining the junction temperature of the power device based on the peak voltage of the DC bus ringing, the stable value of the DC bus voltage, and the phase current; The switching frequency value calculation module is used to judge whether the fluctuation amplitude of the junction temperature of each power device exceeds a first threshold. If it exceeds, a first switching frequency value is obtained through calculation; at the same time, it is judged whether the difference between the maximum junction temperature and the minimum junction temperature of the power devices of each phase arm exceeds a second threshold. If it exceeds, a second switching frequency value is obtained through calculation; Among them, if the fluctuation amplitude of the junction temperature of each power device exceeds the first threshold, the PID method is used to calculate the switching frequency value under different load currents as the first switching frequency value; If the fluctuation amplitude of the junction temperature of each power device does not exceed the first threshold, return to the real-time junction temperature calculation module to continue the calculation; If the difference between the maximum junction temperature and the minimum junction temperature of the power devices of each phase arm exceeds the second threshold, the PID method is used to calculate the switching frequency value of each phase arm as the second switching frequency value; If the difference between the maximum junction temperature and the minimum junction temperature of the power devices of each phase arm does not exceed the second threshold, return to the real-time junction temperature calculation module to continue the calculation; The limiting module is used to obtain the switching frequency value of the phase arm according to the first switching frequency value and the second switching frequency value, input the switching frequency value of the phase arm into the limiter to perform limiting according to the limit value; calculate the switching frequency value f of the phase arm according to the following formula: f = a·b·f s where a is the relative multiple of the first switching frequency value, b is the relative multiple of the second switching frequency value, and f s is the base frequency; The switching frequency adjustment module is used to adjust the switching frequency of the power device according to the switching frequency value output by the limiter.

6. An electronic device, characterized in that, Including: A processor; And A memory, on which executable code is stored. When the executable code is executed by the processor, the method described in any one of claims 1-4 is executed.

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