Power device protection control method, device, frequency conversion controller and storage medium

Abstract

This invention proposes a protection and control method, device, frequency converter, and storage medium for power devices. The protection and control method includes: acquiring the operating parameters of the power device; determining the instantaneous junction temperature and the average junction temperature over a target time period of the power device based on the operating parameters; acquiring the difference between the instantaneous junction temperature and / or the average junction temperature and a preset junction temperature; and adjusting the control signal of the power device based on the difference to ensure that both the instantaneous junction temperature and the average junction temperature are not higher than the preset junction temperature. This invention can balance the instantaneous junction temperature and the average junction temperature of the power device, improve the protection response speed and the stability of the power device, and quickly and stably suppress the operating temperature of the power device within the normal operating range.

Description

Technical Field

[0001] This invention relates to the field of electronic device technology, and in particular to a protection and control method, device, frequency converter, and storage medium for power devices. Background Technology

[0002] Currently, in electrical systems, electrical control equipment typically uses power devices for control. However, power devices generally have low overload resistance and are prone to damage from overloads. Related technologies rely solely on the current flowing through the power device as the basis for protection, controlling its shutdown. However, relying solely on the current value results in insufficient control precision, slow response, and a tendency for untimely or over-protection, leading to system instability, premature aging, or even damage to the power devices. Therefore, how to quickly protect power devices while ensuring stable system operation is a pressing issue that needs to be addressed. Summary of the Invention

[0003] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a protection and control method, device, frequency converter, and storage medium for power devices, which can accelerate the protection response speed, quickly adjust the power devices under stable system operation, and improve the stability of the power devices.

[0004] In a first aspect, embodiments of the present invention provide a protection control method for a power device, the protection control method comprising:

[0005] Obtain the operating parameters of the power device;

[0006] The instantaneous junction temperature and the average junction temperature over the target duration of the power device are determined based on the operating parameters.

[0007] The difference between the instantaneous junction temperature and / or the average junction temperature and the preset junction temperature is obtained, and the control signal of the power device is adjusted according to the difference so that the instantaneous junction temperature and the average junction temperature are not higher than the preset junction temperature.

[0008] The protection and control method provided by the embodiments of the present invention has at least the following beneficial effects: by detecting the operating parameters of the power device, the instantaneous junction temperature of the power device at the current moment and the average junction temperature over a target duration are calculated. By comparing the difference between the instantaneous junction temperature and the preset junction temperature, the instantaneous operating state of the power device at the current moment can be determined, and by comparing the difference between the average junction temperature and the preset junction temperature, the average operating state of the power device over the target duration can be determined. The average operating state can be characterized as a combination of multiple instantaneous operating states over the target duration. Both the instantaneous operating state and the average operating state can reflect whether the temperature of the power device has been adjusted, and the magnitude of the difference can determine the adjustment range required by the control signal, so that the instantaneous junction temperature and the average junction temperature of the power device can be quickly adjusted to below the preset junction temperature range. Compared to related technologies that rely solely on the current flowing through the device for control, this invention utilizes the difference between the instantaneous junction temperature and / or average junction temperature of the power device and a preset junction temperature to adjust the control signal of the power device. This improves the response speed and stability of the power device protection, taking into account both the instantaneous and average junction temperatures. It quickly and stably suppresses the operating temperature of the power device within the preset junction temperature range, avoiding untimely protection that could lead to excessively high operating temperatures of the power device or over-protection that could cause system shutdown.

[0009] In the above-described protection and control method, the preset junction temperature includes a first preset junction temperature and a second preset junction temperature, wherein the first preset junction temperature and the second preset junction temperature are the same or different.

[0010] Because the temperature rise caused by a short-term pulse can easily cause the instantaneous temperature of the power device to exceed the preset junction temperature, but if the power device is in an over-temperature state for a long time, it will damage the power device. Therefore, the requirements for the instantaneous junction temperature and the average junction temperature of the power device can be the same or different. Thus, a first preset junction temperature and a second preset junction temperature can be set for the instantaneous junction temperature and the average junction temperature, respectively. The first preset junction temperature can be used as the upper limit of the instantaneous junction temperature, and the second preset junction temperature can be used as the upper limit of the average junction temperature.

[0011] In the above-described protection and control method, the step of obtaining the difference between the instantaneous junction temperature and / or the average junction temperature and the preset junction temperature, and adjusting the control signal of the power device based on the difference, includes:

[0012] The duty cycle limit value of the power device is determined based on the difference between the instantaneous junction temperature and the preset junction temperature.

[0013] Based on the difference between the average junction temperature and the preset junction temperature, the required duty cycle of the power device in the next cycle is determined.

[0014] The duty cycle of the control signal for the power device is adjusted based on the duty cycle limit of the power device and the required duty cycle of the power device in the next cycle.

[0015] The power device's temperature is adjusted by changing the heat generation of the power device through adjusting the duty cycle of the control signal. Therefore, the power device's duty cycle limit is a parameter representing the upper limit of the duty cycle adjustment corresponding to the real-time temperature of the power device. Since the power device's duty cycle limit is determined based on the instantaneous junction temperature, and the instantaneous junction temperature is detected in real time, the power device's duty cycle limit is updated in real time, enabling timely suppression of the power device's on-time and protecting the power device. The required duty cycle for the power device in the next cycle is represented by the duty cycle required for the power device's average junction temperature and the required power in the next cycle. Thus, the power device's duty cycle limit can be used to adjust the required duty cycle for the power device in the next cycle, maintaining the average and instantaneous junction temperatures within the preset junction temperature range for the target duration.

[0016] In the above-described protection and control method, adjusting the duty cycle of the control signal for the power device based on the duty cycle limit value of the power device and the required duty cycle of the power device in the next cycle includes:

[0017] In response to the power device duty cycle limit value being less than the power device duty cycle required for the next cycle, the power device duty cycle limit value is used to adjust the duty cycle of the control signal of the power device.

[0018] In response to the power device duty cycle limit value being equal to the power device duty cycle required for the next cycle, the duty cycle of the control signal for the power device is adjusted using the power device duty cycle limit value or the power device duty cycle required for the next cycle.

[0019] In response to the power device's duty cycle limit being greater than the power device's required duty cycle for the next cycle, the duty cycle of the control signal for the power device is adjusted using the power device's required duty cycle for the next cycle.

[0020] By comparing the duty cycle limit of the power device with the duty cycle required by the power device in the next cycle, the duty cycle limit of the power device is used to limit and suppress the required duty cycle of the power device in the next cycle. This can quickly suppress the on-time of the power device, suppress heat generation, thereby rapidly reducing the junction temperature. It can also avoid a surge in heat generation due to a rapid extension of the on-time, and improve the temperature stability of the power device.

[0021] In the above-described protection and control method, determining the power device's duty cycle limit value based on the difference between the instantaneous junction temperature and the preset junction temperature includes:

[0022] In response to the difference between the instantaneous junction temperature and the preset junction temperature being greater than zero, the duty cycle limit value of the power device is gradually reduced by control adjustment;

[0023] or,

[0024] In response to the difference between the instantaneous junction temperature and the preset junction temperature being less than zero, the duty cycle limit value of the power device is gradually increased by control adjustment.

[0025] When the difference between the instantaneous junction temperature and the preset junction temperature is greater than or equal to zero, the power device can be considered overheated. Therefore, by gradually decreasing the power device's duty cycle limit value in the control signal from the previous moment and updating the duty cycle limit value, the on-time of the power device can be quickly shortened, heat generation can be rapidly reduced, and the operating temperature of the power device can be lowered in a timely manner. Conversely, when the difference between the instantaneous junction temperature and the preset junction temperature is less than zero, the power device can be considered to be in normal operating condition. Therefore, the power device's duty cycle limit value in the control signal can be gradually increased according to the actual power demand, which can quickly improve the system's operating power.

[0026] In the above-described protection and control method, determining the required duty cycle of the power device for the next cycle based on the difference between the average junction temperature and the preset junction temperature includes:

[0027] The on-current limit value of the power device is determined based on the difference between the average junction temperature and the preset junction temperature.

[0028] The required duty cycle of the power device in the next cycle is obtained based on the power device's on-current limit, the system's required current in the next cycle, and the current actual on-current of the power device.

[0029] By measuring the difference between the average junction temperature and the preset junction temperature, the required change in current when the average junction temperature is adjusted to the preset junction temperature is determined. This determines the maximum current flowing through the power device, i.e., the power device's on-state current limit. Consequently, the required on-state duty cycle of the power device for the next cycle is obtained. Thus, the maximum allowable on-state duration is determined by measuring the maximum allowable current flowing through the power device, thereby maintaining the average temperature of the power device.

[0030] In the aforementioned protection and control method, obtaining the required duty cycle of the power device in the next cycle based on the power device's on-current limit, the system's required current for the next cycle, and the current actual on-current of the power device includes:

[0031] In response to the power device on-current limit being greater than or equal to the system current required in the next cycle, the system current required in the next cycle is taken as the power device current required in the next cycle, and the required on-duty cycle of the power device in the next cycle is obtained based on the power device current required in the next cycle and the current actual on-current of the power device.

[0032] In response to the fact that the power device's on-current limit is less than the current required by the system in the next cycle, the power device's on-current limit is taken as the current required by the power device in the next cycle. Then, the required duty cycle of the power device in the next cycle is obtained based on the current required by the power device in the next cycle and the current actual on-current of the power device.

[0033] After determining the power device on-current limit based on the difference between the average junction temperature and the preset junction temperature, the power device on-current limit is compared with the current required by the system in the next cycle. The current required by the system in the next cycle is characterized as the current value required for the system to operate at the target power. The smaller of the two values ​​is taken to adjust the current value, thereby avoiding excessive current value that could cause power device overload and protecting the power device.

[0034] In the above-described protection and control method, the operating parameters include the instantaneous casing temperature, instantaneous thermal resistance, and instantaneous power loss of the power device at the current moment.

[0035] Determining the instantaneous junction temperature of the power device based on the operating parameters includes:

[0036] The instantaneous temperature increment of the power device is obtained by multiplying the instantaneous power loss and the instantaneous thermal impedance.

[0037] The instantaneous junction temperature of the power device is obtained by summing the instantaneous temperature increment and the instantaneous casing temperature.

[0038] Because the actual temperature of the semiconductor in a power device is higher than the temperature of its casing during operation, and the actual temperature of the semiconductor is difficult to measure, the heat dissipated by the power device can be calculated by combining the instantaneous thermal impedance and instantaneous power loss of the power device. Combined with the instantaneous casing temperature of the power device at the current moment, the instantaneous junction temperature of the power device at the current moment can be calculated. By integrating multiple operating parameters of the power device, the real-time operating status of the power device can be accurately determined, and the power device can be protected in a timely manner.

[0039] In the above-described protection and control method, the operating parameters include the average casing temperature, steady-state thermal resistance, and average power loss of the power device during the target duration.

[0040] Determining the average junction temperature of the power device within the target duration based on the operating parameters includes:

[0041] The average temperature increment of the power device is obtained by multiplying the average power loss and the steady-state thermal impedance.

[0042] The average junction temperature of the power device is obtained by summing the average temperature increment and the average case temperature.

[0043] The heat dissipated by the power device within the target duration is determined by the average power loss and steady-state thermal resistance of the power device within the target duration. This is the difference between the average junction temperature and the average case temperature of the power device within the target duration. Thus, the average junction temperature of the power device can be determined. By combining multiple operating parameters of the power device within the target duration, the operating state of the power device within the target duration can be judged, and the stability of the operating temperature of the power device can be maintained.

[0044] In the above protection and control method, the target duration is the time it takes for the instantaneous thermal impedance of the power device to reach a stable value from its initial value in the preset thermal impedance-duration ratio relationship.

[0045] Thermal resistance is an inherent physical property of power devices. Power devices typically start to heat up from the moment they are powered on, and their thermal resistance begins to rise. After a certain period of time, it tends to stabilize. The rate of temperature change is unstable. Therefore, by using a pre-set ratio of thermal resistance to time, the required time for the thermal resistance of the power device to stabilize can be determined. Using the target time to measure the operating parameters can reduce the error caused by thermal resistance fluctuations.

[0046] In a second aspect, embodiments of the present invention provide an operation control device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the protection control method described in the first aspect embodiment above.

[0047] The operation control device provided by the embodiments of the present invention has at least the following beneficial effects: by detecting the operating parameters of the power device, the instantaneous junction temperature of the power device at the current moment and the average junction temperature over a target duration are calculated. By comparing the difference between the instantaneous junction temperature and the preset junction temperature, the instantaneous operating state of the power device at the current moment can be determined, and by comparing the difference between the average junction temperature and the preset junction temperature, the average operating state of the power device over the target duration can be determined. The average operating state can be characterized as a combination of multiple instantaneous operating states over the target duration. Both the instantaneous operating state and the average operating state can reflect whether the temperature of the power device has been adjusted, and the magnitude of the difference can determine the adjustment range required by the control signal, so that the instantaneous junction temperature and the average junction temperature of the power device can be quickly adjusted to below the preset junction temperature range. Compared to related technologies that rely solely on the current flowing through the device for control, this invention utilizes the difference between the instantaneous junction temperature and / or average junction temperature of the power device and a preset junction temperature to adjust the control signal of the power device. This improves the response speed and stability of the power device protection, taking into account both the instantaneous and average junction temperatures. It quickly and stably suppresses the operating temperature of the power device within the preset junction temperature range, avoiding untimely protection that could lead to excessively high operating temperatures of the power device or over-protection that could cause system shutdown.

[0048] Thirdly, embodiments of the present invention provide a frequency converter controller, including the operation control device described in the second aspect of the embodiments above.

[0049] The frequency converter provided by the embodiments of the present invention has at least the following beneficial effects: by detecting the operating parameters of the power device, the instantaneous junction temperature of the power device at the current moment and the average junction temperature over a target duration are calculated. By comparing the difference between the instantaneous junction temperature and the preset junction temperature, the instantaneous operating state of the power device at the current moment can be determined, and by comparing the difference between the average junction temperature and the preset junction temperature, the average operating state of the power device over the target duration can be determined. The average operating state can be characterized as a combination of multiple instantaneous operating states over the target duration. Both the instantaneous operating state and the average operating state can reflect whether the temperature of the power device has been adjusted, and the magnitude of the difference can determine the adjustment range required by the control signal, so that the instantaneous junction temperature and the average junction temperature of the power device can be quickly adjusted to below the preset junction temperature range. Compared to related technologies that rely solely on the current flowing through the device for control, this invention utilizes the difference between the instantaneous junction temperature and / or average junction temperature of the power device and a preset junction temperature to adjust the control signal of the power device. This improves the response speed and stability of the power device protection, taking into account both the instantaneous and average junction temperatures. It quickly and stably suppresses the operating temperature of the power device within the preset junction temperature range, avoiding untimely protection that could lead to excessively high operating temperatures of the power device or over-protection that could cause system shutdown.

[0050] Fourthly, embodiments of the present invention provide a computer-readable storage medium storing computer-executable instructions for causing a computer to perform the protection and control method described in the first aspect of the embodiments above.

[0051] The computer-readable storage medium provided according to embodiments of the present invention has at least the following beneficial effects: by detecting the operating parameters of the power device, the instantaneous junction temperature of the power device at the current moment and the average junction temperature over a target duration are calculated. By comparing the difference between the instantaneous junction temperature and the preset junction temperature, the instantaneous operating state of the power device at the current moment can be determined, and by comparing the difference between the average junction temperature and the preset junction temperature, the average operating state of the power device over the target duration can be determined. The average operating state can be characterized as a combination of multiple instantaneous operating states over the target duration. Both the instantaneous operating state and the average operating state can reflect whether the temperature of the power device has been adjusted, and the magnitude of the difference can determine the adjustment range required by the control signal, so that the instantaneous junction temperature and the average junction temperature of the power device can be quickly adjusted to below the preset junction temperature range. Compared to related technologies that rely solely on the current flowing through the device for control, this invention utilizes the difference between the instantaneous junction temperature and / or average junction temperature of the power device and a preset junction temperature to adjust the control signal of the power device. This improves the response speed and stability of the power device protection, taking into account both the instantaneous and average junction temperatures. It quickly and stably suppresses the operating temperature of the power device within the preset junction temperature range, avoiding untimely protection that could lead to excessively high operating temperatures of the power device or over-protection that could cause system shutdown.

[0052] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description and the drawings. Attached Figure Description

[0053] The present invention will be further described below with reference to the accompanying drawings and embodiments;

[0054] Figure 1 This is a flowchart of a protection and control method for power devices provided in an embodiment of the present invention;

[0055] Figure 2 yes Figure 1 The detailed flowchart of step S103;

[0056] Figure 3 yes Figure 2 The detailed flowchart of step S203;

[0057] Figure 4 yes Figure 2 The detailed flowchart of step S201;

[0058] Figure 5 yes Figure 2 The detailed flowchart of step S202;

[0059] Figure 6 yes Figure 5 Detailed flowchart before step S502;

[0060] Figure 7 yes Figure 1 The detailed flowchart of step S102;

[0061] Figure 8 yes Figure 1 The detailed flowchart of step S102;

[0062] Figure 9 This is a schematic diagram illustrating the preset thermal resistance-time ratio;

[0063] Figure 10 This is a schematic flowchart of the protection and control method for the power device of the present invention;

[0064] Figure 11 This is a schematic diagram of the operation control device provided in an embodiment of the present invention. Detailed Implementation

[0065] This section will describe in detail specific embodiments of the present invention. Preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and overall technical solution of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0066] It should be understood that in the description of the embodiments of the present invention, the use of terms such as "first" and "second" is only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of technical features indicated, or implicitly indicating the order of the technical features indicated. "At least one" means one or more, and "more than one" means two or more. "At least one of the following" and similar expressions refer to any combination of these items, including any combination of single or multiple items.

[0067] Furthermore, unless otherwise explicitly specified and limited, the term "connection / linkage" should be interpreted broadly, for example, it can be a fixed connection or a movable connection, a detachable connection or a non-detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection or a connection that can communicate with each other; it can be a direct connection or an indirect connection through an intermediate medium.

[0068] In the description of the embodiments of the present invention, the terms "one embodiment / implementation," "another embodiment / implementation," or "some embodiments / implementations," "in the above embodiments / implementations," etc., refer to specific features, structures, materials, or characteristics described in conjunction with embodiments or examples that are included in at least two embodiments or implementations of this disclosure. In this disclosure, the illustrative expressions of the above terms do not necessarily refer to the same illustrative embodiment or implementation. It should be noted that although a logical order is shown in the flowcharts, in some cases, the steps shown or described may be performed in a different order than that shown in the flowcharts.

[0069] It should be noted that the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0070] This invention provides a protection and control method, device, frequency converter, and storage medium for power devices. By utilizing the difference between the instantaneous junction temperature and / or average junction temperature of the power device and a preset junction temperature, the control signal of the power device is adjusted to improve the response speed and stability of the power device protection. It takes into account both the instantaneous and average junction temperatures of the power device, and quickly and stably suppresses the average and instantaneous junction temperatures of the power device within the preset junction temperature range, avoiding untimely protection that leads to excessively high operating temperatures of the power device or over-protection that causes system shutdown.

[0071] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0072] Reference Figure 1 , Figure 1 This is a flowchart of a protection and control method for a power device provided in an embodiment of the present invention. The protection and control method for the power device includes, but is not limited to, the following steps:

[0073] Step S101: Obtain the operating parameters of the power device;

[0074] Step S102: Determine the instantaneous junction temperature and the average junction temperature within the target duration of the power device based on the operating parameters.

[0075] Step S103: Obtain the difference between the instantaneous junction temperature and / or the average junction temperature and the preset junction temperature, and adjust the control signal of the power device according to the difference so that the instantaneous junction temperature and the average junction temperature are not higher than the preset junction temperature.

[0076] Understandably, the safe and reliable operation of power devices is crucial for the stable operation of electrical systems. Since current flowing through power devices causes their temperature to rise, excessively high temperatures can damage them. However, temperature sensors in related technologies cannot directly measure the junction temperature of the semiconductor inside the power device; they can only measure the temperature of the device's casing. The actual temperature of the semiconductor inside the power device is higher than the temperature of its casing, making it inaccurate to use only temperature sensors to detect the operating temperature of the power device.

[0077] In addition, the ambient temperature of the power device, the heat dissipation conditions of the power device, the voltage applied to the power device, and the thermal resistance of the power device all affect the operating temperature of the power device, that is, affect the operating state of the power device.

[0078] Therefore, the operating parameters of the power device can be monitored in real time and recorded, retaining the operating parameters of the power device within the target time period. The operating temperature of the power device at the current moment is analyzed using the operating parameters at the current moment to determine the instantaneous junction temperature of the power device, i.e., the actual operating temperature of the semiconductor in the power device. Correspondingly, the average junction temperature of the power device within the target time period can be determined using the operating parameters within the target time period. The average junction temperature can be represented by the average of multiple instantaneous junction temperatures within the target time period. Therefore, the control signal of the power device can be adjusted using only the difference between the instantaneous junction temperature and the preset junction temperature. When the instantaneous junction temperature is suppressed within the preset junction temperature range, the average junction temperature can also be suppressed within the preset junction temperature range, thus ensuring that both the instantaneous junction temperature and the average junction temperature are below the preset junction temperature. Alternatively, the control signal for the power device can be adjusted using only the difference between the average junction temperature and the preset junction temperature. When the average junction temperature is kept within the preset junction temperature range, it can be assumed that the power device has not been in an overheated state for an extended period. While the instantaneous junction temperature may exceed the preset junction temperature within the target duration, it remains within the acceptable range for the power device. Furthermore, reducing the average junction temperature can simultaneously reduce the instantaneous junction temperature, ensuring that the instantaneous junction temperature is below or equal to the preset junction temperature. Additionally, the control signal for the power device can be comprehensively adjusted based on both the difference between the instantaneous junction temperature and the preset junction temperature, as well as the difference between the average junction temperature and the preset junction temperature, to suppress both the average and instantaneous junction temperatures below the preset junction temperature.

[0079] Since the average junction temperature is obtained from the operating parameters within the target duration, it is a stable value within one cycle, i.e., the target duration. The instantaneous junction temperature, however, is calculated using real-time updated operating parameters, resulting in real-time changes. The update frequency of the instantaneous junction temperature is higher than that of the average junction temperature. The difference between the instantaneous junction temperature and the preset junction temperature, as well as the difference between the average junction temperature and the preset junction temperature within the target duration, determines the amount of adjustment required for the current state of the power device—that is, the amount of heat generation that needs to be reduced or increased. A larger difference indicates a greater reduction in heat generation. Therefore, by adjusting the control signal of the power device in real time using this difference, the average and instantaneous junction temperatures can be controlled below the preset junction temperature, maintaining the stability of the power device's temperature. Simultaneously, the real-time nature of the instantaneous junction temperature is considered, achieving rapid response for temperature protection. This enables multi-cycle temperature control of the power device, allowing for rapid adjustment and maintaining its stability.

[0080] Furthermore, the target duration can be updated in real time. For example, the target duration can be a fixed-length window, with the current time as the end of the window. The window slides continuously with the current time, and the target duration is updated in real time. Therefore, the average junction temperature determined using the operating parameters within the target duration has the same update frequency as the instantaneous junction temperature, reflecting the temperature of the power device over the past target duration and its current temperature. Consequently, the control signal for the power device can be adjusted in real time based on the average junction temperature and / or the instantaneous junction temperature, enabling rapid temperature adjustment and stable temperature maintenance.

[0081] By comparing the average junction temperature and the preset junction temperature of a power device, it can be determined whether the power device is in an over-temperature state within a target time period. Alternatively, by comparing the instantaneous junction temperature and the preset junction temperature, it can be determined whether the power device is currently in an over-temperature state. When a power device is in an over-temperature state, it can be assumed that the power device needs to be cooled down. The control signal of the power device is adjusted to change the operating state of the power device, reduce the heat generation of the power device, and thus lower the junction temperature of the power device, ensuring that neither the instantaneous junction temperature nor the average junction temperature exceeds the preset junction temperature, thereby preventing the power device from over-temperature.

[0082] In related technologies, the current flowing through a power device is used as the basis for its protection. When the current exceeds a protection threshold, the power device is shut down until the current drops below the threshold, or the control signal is blocked to shut down the device until the blocking time reaches a preset duration and the current threshold drops below the protection threshold. Since current flowing through a power device causes its temperature to rise, and repeatedly switching the device on and off in a short period increases power loss and leads to a rapid temperature rise, excessively high temperatures accelerate the aging and damage of the device. Conversely, prolonged blocking of the control signal causing the device to shut down can disrupt the system's stable operation. Therefore, using the instantaneous junction temperature and average junction temperature of the power device as the basis for protection allows for accurate assessment of its operating status, enabling timely and accurate protection. Furthermore, it stabilizes the device's temperature, avoids over-protection, and ensures timely protection of the power device while maintaining stable and continuous system operation.

[0083] It should be noted that operating parameters may include the power device's casing temperature, power loss, thermal impedance, and operating voltage and current. The power device's casing temperature can be directly measured by a temperature sensor or calculated using other operating parameters, such as ambient temperature. The operating current and voltage applied to the power device can be detected by a voltage and current detection circuit or calculated from other operating parameters.

[0084] It should be noted that the temperature rise caused by the short-term pulse can easily cause the instantaneous temperature of the power device to exceed the preset junction temperature. However, if the power device is in an over-temperature state for a long time, it will be damaged. Therefore, the requirements for the instantaneous junction temperature and the average junction temperature of the power device can be the same or different. Thus, a first preset junction temperature and a second preset junction temperature can be set for the instantaneous junction temperature and the average junction temperature, respectively. The first preset junction temperature can be used as the upper limit of the instantaneous junction temperature, and the second preset junction temperature can be used as the upper limit of the average junction temperature.

[0085] It should be noted that adjusting the control signal of a power device to change its operating state can be achieved by directly controlling the actual operating parameters of the control signal, such as at least one of the operating current, operating voltage, and duty cycle; or by controlling the upper limit of the operating parameters of the control signal, thereby indirectly adjusting the actual operating parameters of the power device, such as at least one of the upper limit of current, upper limit of voltage, and upper limit of duty cycle. Therefore, by judging the operating state of the power device in real time by the difference between the instantaneous junction temperature and / or the average junction temperature and the preset junction temperature, the control signal of the power device can be adjusted in real time to change the operating parameters of the power device, thereby enabling rapid control of the operating temperature of the power device. For example, when the instantaneous junction temperature is higher than the first preset junction temperature or the average junction temperature is higher than the second preset junction temperature, the duty cycle of the control signal can be adjusted to reduce the on-time of the power device, thereby reducing the heat generation of the power device and rapidly lowering the junction temperature. Alternatively, the duty cycle limit value of the control signal can be adjusted to limit the on-time of the control signal, shortening the maximum on-time of the power device, suppressing the heat generation of the power device, and achieving the effect of lowering the junction temperature of the power device. Therefore, based on the comparison between the difference between the instantaneous junction temperature and the first preset junction temperature, and the difference between the average junction temperature and the second preset junction temperature, the duty cycle of the control signal for the power device is adjusted in real time. This accurately adjusts the heat generated by the power device during its on-time operation, thereby precisely adjusting the operating temperature of the power device, improving the response speed of power device protection, and ensuring timely protection of the power device. Because the duty cycle of the control signal is short, real-time control of the duty cycle can quickly change the operating state of the power device and its junction temperature, achieving a rapid protection response speed.

[0086] Reference Figure 2 , Figure 2 yes Figure 1 The detailed flowchart of step S103 is as follows: Figure 2 In the example, step S103 includes, but is not limited to, the following steps:

[0087] Step S201: Determine the duty cycle limit value of the power device based on the difference between the instantaneous junction temperature and the preset junction temperature;

[0088] Step S202: Determine the required duty cycle of the power device in the next cycle based on the difference between the average junction temperature and the preset junction temperature.

[0089] Step S203: Adjust the duty cycle of the control signal of the power device according to the duty cycle limit value of the power device and the duty cycle required by the power device in the next cycle.

[0090] It is understandable that when a power device is turned on, the current flowing through it causes its temperature to rise. Therefore, the heat generated by the power device can be controlled by adjusting its on-time, thus regulating its temperature. The power device is controlled by its corresponding control signal, and it operates according to this signal. By adjusting the duty cycle of the control signal, the on-time of the power device can be controlled, achieving the effect of rapidly adjusting its temperature.

[0091] The difference between the real-time instantaneous junction temperature and the preset junction temperature of the power device is calculated. The instantaneous junction temperature can be compared with the first preset junction temperature to determine the temperature variable that needs to be adjusted for the current real-time temperature of the power device. This determines the power device's duty cycle limit based on the instantaneous junction temperature, which is the maximum allowable on-time of the power device set based on the instantaneous junction temperature. The duty cycle of the control signal is then limited and adjusted according to this duty cycle limit, preventing the control signal's duty cycle from exceeding the power device's duty cycle limit, thus reducing the power device's on-time. When the instantaneous junction temperature is higher than the preset junction temperature, the determined power device duty cycle limit is smaller, resulting in a reduction in the maximum allowable on-time of the power device, thereby suppressing the power device's on-time, reducing heat generation, and rapidly lowering the power device's junction temperature. When the preset junction temperature is higher than the instantaneous junction temperature, the determined duty cycle limit for the power device is larger. Therefore, the duty cycle of the control signal can be adjusted according to actual usage requirements without exceeding the duty cycle limit, allowing the system to operate according to actual needs. Thus, based on a comparison of the instantaneous and preset junction temperatures, the duty cycle limit for the power device is determined. This allows for real-time adjustment of the duty cycle of the control signal for the power device, suppressing heat generation during the power device's on-time operation, thereby controlling the operating temperature of the power device, improving the response speed of power device protection, and ensuring timely protection. Because the duty cycle of the control signal is short, real-time control of the duty cycle can quickly change the operating state of the power device and its junction temperature, achieving a rapid protection response speed.

[0092] Furthermore, the difference between the average junction temperature and the preset junction temperature of the power device within the target duration is calculated. The average junction temperature can be compared with a second preset junction temperature, which may be the same as or different from a first preset junction temperature. This determines the temperature variable that needs adjustment for the average temperature of the power device within the target duration. Since the average junction temperature remains stable within the same target duration, the required duty cycle of the power device in the next cycle can be determined using the average junction temperature. In other words, the required conduction time of the power device in the next cycle based on the average junction temperature or the target power can be determined. Therefore, the duty cycle of the control signal can be adjusted using the required duty cycle of the power device in the next cycle, so that the power device can operate according to the target power or the average junction temperature of the power device can be stabilized below the preset junction temperature. The next cycle can be the next target duration or multiple subsequent target durations.

[0093] Correspondingly, when the average junction temperature is higher than the preset junction temperature, and the larger the difference, the smaller the duty cycle required for the power device in the next cycle. Therefore, the conduction time of the power device is shorter, the heat generation can be quickly suppressed, and the temperature of the power device can be quickly reduced.

[0094] Therefore, the duty cycle of the control signal is comprehensively adjusted based on the duty cycle limit of the power device and the duty cycle required by the power device in the next cycle. This ensures that the duty cycle does not exceed the duty cycle limit of the power device or is updated according to the duty cycle required by the power device in the next cycle. This suppresses the conduction time of the power device, reduces heat generation, and achieves a balance between the real-time operating temperature and the long-term operating temperature of the power device. It also improves the response speed of the power device temperature protection and ensures the stability of the long-term operating temperature of the power device.

[0095] It should be noted that the required duty cycle of the power device in the next cycle can be used to individually adjust the duty cycle of the control signal for the power device at the next moment. That is, the required duty cycle of the power device in the next cycle corresponds to only one duty cycle of the control signal, allowing for real-time and accurate suppression of the power device's on-time and precise control of its junction temperature. Furthermore, the update cycle of the average junction temperature corresponds to multiple pulse cycles of the control signal, meaning that the required duty cycle of the power device in the next cycle corresponds to multiple duty cycles in the control signal. Therefore, the required duty cycle of the power device in the next cycle can be used to adjust multiple duty cycles. Since the instantaneous junction temperature is updated in real time, the power device's duty cycle limit is also updated in real time, allowing for individual adjustment of the control signal's duty cycle at the next moment using the power device's duty cycle limit. By utilizing the instantaneous junction temperature at the current moment and the average junction temperature over the target duration, one or more duty cycles of the control signal for the power device in the next cycle can be adjusted. That is, each duty cycle can be changed according to the relationship between the instantaneous junction temperature and the preset junction temperature, as well as the relationship between the average junction temperature and the preset junction temperature, to achieve accurate protection of the power device and improve the reliability of system operation.

[0096] It should be noted that the duty cycle of the power device's control signal is adjusted based on the power device's duty cycle limit and the required duty cycle for the power device in the next cycle. This can be achieved by setting a transient control period and a steady-state control period. During the transient control period, the duty cycle of the power device's control signal is adjusted using the power device's duty cycle limit. During the steady-state control period, the duty cycle of the power device's control signal is adjusted using the required duty cycle for the power device in the next cycle. The transient control period and the steady-state control period are alternated according to a preset ratio, such as alternating between the transient and steady-state control periods, or setting two transient control periods in the interval between two steady-state control periods.

[0097] It should be noted that, understandably, the difference between the instantaneous junction temperature and the preset junction temperature is obtained, i.e., the first difference. This first difference determines the amount of heat the power device needs to reduce in the current state, or the incremental temperature rise that the power device can support by increasing its operating power in the current state. The first difference is the difference between the instantaneous junction temperature and the preset junction temperature. When the first difference is positive, it indicates that the instantaneous junction temperature is higher than the preset junction temperature, meaning the power device needs to reduce its operating time to lower the temperature. The larger the first difference, the more heat the power device needs to reduce, the shorter the maximum allowable operating time, and the smaller the duty cycle limit, thus rapidly reducing the operating temperature of the power device. When the first difference is negative, it indicates that the instantaneous junction temperature is lower than the preset junction temperature, and the power device is in a normal state. The first difference represents the incremental temperature rise that the power device can support. The smaller the first difference, the greater the temperature rise that the power device can achieve, the longer the maximum allowable operating time, and the larger the duty cycle limit. Therefore, by comparing the difference between the instantaneous junction temperature and the preset junction temperature, and using this difference as the basis for adjusting the duty cycle limit of the power device, the junction temperature of the power device can be controlled more accurately and quickly, thus protecting the power device in a timely manner.

[0098] It should be noted that the first difference between the instantaneous junction temperature and the preset junction temperature can be used to calculate the duty cycle limit of the power device through a PID (Proportional Integral Derivative) control system, or it can be determined by a proportional-integral controller. The ratio of this first difference to the instantaneous junction temperature determines the required temperature adjustment range based on the current instantaneous junction temperature, i.e., the adjustment ratio. For example, if the instantaneous junction temperature is 100℃ and the preset junction temperature is 120℃, the first difference is -20℃, indicating that the duty cycle limit of the power device can be increased so that the instantaneous junction temperature rises by 20℃. The corresponding adjustment ratio is 20%, meaning that under the control signal of the current duty cycle, the junction temperature of the power device is 100℃. Based on the current state with a 20% temperature rise range, the current duty cycle limit of the power device can be increased by 20%, i.e., the adjusted duty cycle limit of the power device is 120% of the current duty cycle limit. For example, if the instantaneous junction temperature is 160℃ and the preset junction temperature is 120℃, the first difference is 40℃, indicating that the power device needs to be cooled by more than 30℃. The corresponding adjustment ratio is 25%. This means that given the current duty cycle limit of the power device, a 25% temperature reduction is required based on the current instantaneous junction temperature. Therefore, the current duty cycle is reduced by 25%, meaning the adjusted duty cycle limit is 75% of the current limit, resulting in a temperature reduction to 120℃, ensuring the instantaneous junction temperature does not exceed the preset junction temperature. By adjusting the duty cycle limit of the power device corresponding to the current instantaneous junction temperature using the adjustment ratio, the corresponding temperature range can be adjusted, achieving accurate and timely temperature control.

[0099] Reference Figure 3 , Figure 3 yes Figure 2 The detailed flowchart of step S203 is as follows: Figure 3 In the example, step S203 includes, but is not limited to, the following steps:

[0100] Step S301: In response to the power device duty cycle limit value being less than the power device duty cycle required for the next cycle, the power device duty cycle limit value is used to adjust the power device control signal duty cycle.

[0101] Step S302: In response to the power device duty cycle limit value being equal to the power device duty cycle required for the next cycle, the duty cycle of the control signal of the power device is adjusted using the power device duty cycle limit value or the power device duty cycle required for the next cycle.

[0102] Step S303: In response to the power device duty cycle limit value being greater than the power device duty cycle required for the next cycle, the duty cycle of the control signal of the power device is adjusted using the power device duty cycle required for the next cycle.

[0103] Understandably, the power device's duty cycle limit is a parameter representing the maximum allowable duty cycle adjustment corresponding to the power device's real-time temperature. That is, when the duty cycle exceeds the limit, the instantaneous junction temperature will exceed the first preset junction temperature. Since the duty cycle limit is determined based on the instantaneous junction temperature, and this temperature is monitored in real-time, the duty cycle limit is updated continuously, allowing for timely adjustment and protection of the power device. The required duty cycle for the next cycle represents the duty cycle for the next cycle corresponding to the average temperature or target power within the target duration. That is, when the control signal uses the required duty cycle for the next cycle, the power device can be controlled to achieve the target power or maintain a stable average junction temperature below the preset junction temperature within the next target duration.

[0104] The smaller the duty cycle limit of the power device, the shorter the maximum allowable conduction time, the less heat the power device generates, and the faster the junction temperature can be suppressed. Thus, by using the duty cycle limit of the power device and the duty cycle required by the power device in the next cycle, the adjustment range of both instantaneous junction temperature and average junction temperature can be determined.

[0105] The duty cycle of the power device is adjusted by taking the smaller of the power device's duty cycle limit and the required duty cycle for the next cycle, ensuring that neither the instantaneous junction temperature nor the average junction temperature exceeds the preset junction temperature. If the power device's duty cycle limit is less than the required duty cycle for the next cycle, it can be assumed that the instantaneous junction temperature is higher than the average junction temperature, or the difference between the instantaneous junction temperature and the first preset junction temperature is greater than the difference between the average junction temperature and the second preset junction temperature. Therefore, the required adjustment range for the instantaneous junction temperature is greater than that for the average junction temperature. Thus, the duty cycle of the control signal is adjusted using the power device's duty cycle limit, prioritizing the instantaneous junction temperature as the protection basis. The temperature of the power device is rapidly reduced or slowly increased, ensuring that the instantaneous junction temperature is quickly suppressed below the preset junction temperature or the first preset junction temperature, or preventing the instantaneous junction temperature from exceeding the preset junction temperature or the first preset junction temperature during the increase of the power device's operating power.

[0106] When the required duty cycle of the power device in the next cycle is less than the duty cycle limit of the power device, it can be assumed that the adjustment range of the average junction temperature at the current moment is greater than the adjustment range of the instantaneous junction temperature, i.e., the instantaneous junction temperature is lower than the average junction temperature, or the difference between the instantaneous junction temperature and the first preset junction temperature is less than the difference between the average junction temperature and the second preset junction temperature. Therefore, the duty cycle of the control signal is adjusted by using the required duty cycle of the power device in the next cycle, prioritizing the average junction temperature as the protection basis to maintain the stability of the operating temperature of the power device, while stabilizing the operating frequency of the power device at the target power, and quickly suppressing the average junction temperature to a range below the preset junction temperature or the second preset junction temperature, while avoiding excessively high average junction temperature during the process of increasing the operating power of the power device.

[0107] When the required duty cycle of the power device in the next cycle is equal to the duty cycle limit of the power device, it can be assumed that the instantaneous temperature and the average temperature at the current moment are equal, or the difference between the instantaneous junction temperature and the first preset junction temperature is equal to the difference between the average junction temperature and the second preset junction temperature. That is, the adjustment range of the average junction temperature is equal to the adjustment range of the instantaneous junction temperature. Therefore, the duty cycle of the control signal of the power device can be adjusted by using the required duty cycle of the power device in the next cycle or the duty cycle limit of the power device.

[0108] Reference Figure 4 , Figure 4 yes Figure 2 The detailed flowchart of step S201 is in Figure 4 In the example, step S201 includes, but is not limited to, the following steps:

[0109] Step S401: In response to the difference between the instantaneous junction temperature and the preset junction temperature being greater than zero, the duty cycle limit value of the power device is gradually reduced by control adjustment.

[0110] In step S402, in response to the difference between the instantaneous junction temperature and the preset junction temperature being less than zero, the duty cycle limit value of the power device is gradually increased by control adjustment.

[0111] It is understandable that when the instantaneous junction temperature exceeds the preset junction temperature (i.e., the difference between the instantaneous and preset junction temperatures is greater than zero), the power device is in an overheated state, requiring a reduction in its heat generation. Therefore, by gradually decreasing the power device's duty cycle limit value from the previous control signal, updating the duty cycle limit value, and promptly suppressing pulse current, the maximum allowable on-time of the power device is gradually reduced, thus gradually decreasing the heat generation and rapidly lowering the power device's temperature. This avoids system instability caused by drastically reducing the power device's on-time. Alternatively, the duty cycle limit value can be obtained by gradually reducing the required on-time of the power device in either the previous or next cycle.

[0112] The percentage decrease in the duty cycle limit of the power device can be the same or different. For example, the percentage decrease can be 50% for all cycles. If the duty cycle limit is 0.5 in the first cycle and 0.25 in the second cycle, then the duty cycle limit in the third cycle will be 0.125. Alternatively, the percentage decrease can be different. If the duty cycle limit is 0.5 in the first cycle and 0.4 in the second cycle, then the duty cycle limit in the third cycle will be 0.2. By gradually limiting the duty cycle limit of the power device from the previous moment, the duty cycle limit is determined. This gradual limitation of the control signal's duty cycle can gradually reduce the power device's temperature while maintaining stable operation of the frequency converter, avoiding a significant reduction in the power device's on-time that could affect the system's normal operation.

[0113] When the instantaneous junction temperature is lower than the preset junction temperature, the power device can be considered to be in normal working condition. The system's operating power can be increased by increasing the maximum allowable on-time of the power device according to actual usage requirements. However, in order to avoid the power device burning out due to excessively rapid temperature rise caused by drastically increasing the maximum allowable on-time of the power device, the power device's duty cycle limit value of the control signal is adjusted in a gradual manner. The power device's duty cycle limit value is increased to the preset limit value that meets the actual usage requirements. The temperature rise and junction temperature of the power device can be detected in real time after increasing the power device's duty cycle limit value, so as to avoid the power device overheating and protect the power device in time.

[0114] When the instantaneous junction temperature is equal to the preset junction temperature, the duty cycle limit of the power device in the current control signal can be maintained, or the duty cycle limit of the power device in the current control signal can be reduced according to actual usage requirements, so as to suppress the instantaneous junction temperature below the preset junction temperature.

[0115] It should be noted that the adjustment process of gradually reducing the duty cycle limit of the power device in the control signal can be repeated multiple times. That is, during the process of gradually decreasing the duty cycle limit of the power device in the control signal, if the instantaneous junction temperature changes from a state higher than the preset junction temperature to a state lower than the preset junction temperature, the adjustment operation of gradually decreasing the duty cycle limit of the power device in the control signal can still be maintained, so that the instantaneous junction temperature can be quickly reduced and suppressed below the preset junction temperature. Conversely, during the process of gradually increasing the duty cycle limit of the power device in the control signal, if the real-time instantaneous junction temperature is higher than the preset junction temperature, the adjustment operation of gradually increasing the duty cycle limit of the power device in the control signal can be terminated, and the duty cycle limit of the power device in the control signal can be reduced in time, thereby suppressing the duty cycle of the control signal in a timely manner.

[0116] Reference Figure 5 , Figure 5 yes Figure 2 The detailed flowchart of step S202 is in Figure 5 In the example, step S202 includes, but is not limited to, the following steps:

[0117] Step S501: Determine the power device on-current limit value based on the difference between the average junction temperature and the preset junction temperature.

[0118] Step S502: Obtain the required duty cycle of the power device in the next cycle based on the power device's on-current limit, the system's required current in the next cycle, and the current actual on-current of the power device.

[0119] It is understandable that power devices generate heat during current flow, and the greater the current, the more heat is generated per unit time. Therefore, the temperature of the power device can be controlled by changing the amount of heat generated, thereby controlling the current flowing through it. Operating parameters include the average current, which can be obtained by real-time monitoring of the operating current over a target duration and averaging the values. Operating parameters also include the average voltage of the power device over the target duration. The current change can be determined using the average junction temperature and a second preset junction temperature, and the current change can be calculated using the following formula:

[0120] ΔT=(U×ΔI)×R th

[0121] Where ΔT represents the absolute value of the difference between the average junction temperature and the preset junction temperature, which is a positive value; ΔI represents the change in current; U represents the average voltage of the power device over the target duration; and R... th This represents the thermal impedance of the power device over a target time period, where the thermal impedance is at a stable value. The change in current can be categorized into current overload and current margin based on the relationship between the average junction temperature and the preset junction temperature. When the average junction temperature is greater than the preset junction temperature, the change in current represents the current overload. The current overload of the power device can be calculated using the difference between the average and preset junction temperatures, the average voltage, and the thermal impedance. Subtracting the current overload from the average current yields the current limit of the power device, which can be considered an approximate estimate of the maximum allowable current at the current moment. When the current flowing through the power device exceeds the current limit, it can easily lead to an over-temperature and overload state, damaging the power device.

[0122] The change in current can be calculated by measuring the difference between the average junction temperature and the preset junction temperature, known as the second difference. The ratio of this second difference to the average junction temperature determines the current adjustment ratio, thus determining the required temperature adjustment range based on the current average junction temperature. The power device's on-state current limit is obtained by multiplying the current adjustment ratio by the average current. For example, if the average junction temperature is 100°C and the preset junction temperature is 120°C, the second difference is -20°C, indicating that increasing the average current will raise the average junction temperature by 20°C. The corresponding current adjustment ratio is 20%, meaning that with the current average current flowing through the power device, the junction temperature is 100°C. Based on this 20% temperature rise, the current average current can be increased by 20%, resulting in an adjusted average current of 120% of the current average current.

[0123] When the average junction temperature is less than the preset junction temperature, the change in current represents the current margin. The current margin of the power device can be calculated by the difference between the preset junction temperature and the average junction temperature, the average voltage, and the thermal impedance. The average current plus the current margin gives the current on-state current limit of the power device. When the average junction temperature is equal to the preset junction temperature, the current on-state current limit of the power device can be approximately equal to the average current.

[0124] After obtaining the current on-state current limit of the power device, adjustments need to be made based on the system's required current for the next cycle and the current actual on-state current of the power device. The required current for the power device in the next cycle is determined by comparing the current limit with the system's required current. Then, the difference between the required current and the current actual on-state current allows us to determine the change in current flowing through the power device at the current moment—the third difference. Therefore, by understanding the relationship between the current flowing through the power device and the duty cycle parameter, the required duty cycle for the power device in the next cycle, corresponding to the third difference, can be determined.

[0125] Specifically, the ratio of the third difference to the current actual conduction current of the power device can be used to determine the required current adjustment range, i.e., the current adjustment ratio. By obtaining the current duty cycle parameter, the current adjustment ratio is multiplied by the duty cycle parameter to calculate the required duty cycle of the power device in the next cycle, thereby enabling the adjustment of the corresponding current amplitude and accurate and rapid current adjustment.

[0126] It should be noted that the difference between the average junction temperature and the preset junction temperature can be used to calculate the power device on-current limit value through the PID control system, or the power device on-current limit value can be determined through the proportional-integral controller. Then, the required duty cycle of the power device in the next cycle can be determined based on the power device on-current limit value.

[0127] Reference Figure 6 , Figure 6 yes Figure 5 The detailed flowchart before step S502 is in Figure 6 In the example, the steps preceding step S502 include, but are not limited to, the following steps:

[0128] Step S601: In response to the power device on-current limit being greater than or equal to the system current required in the next cycle, the system current required in the next cycle is used as the power device current required in the next cycle. Then, the required on-duty cycle of the power device in the next cycle is obtained based on the power device current required in the next cycle and the current actual on-current of the power device.

[0129] In step S602, in response to the fact that the power device on-current limit is less than the current required by the system in the next cycle, the power device on-current limit is taken as the current required by the power device in the next cycle, and the required duty cycle of the power device in the next cycle is obtained based on the current required by the power device in the next cycle and the current actual on-current of the power device.

[0130] Understandably, the power devices are installed in the frequency converter. Based on the required operating power of the power devices, the current flowing through them within a target duration corresponds to the current required by the system in the next cycle. The current required by the system in the next cycle is set by the frequency converter according to the current operating requirements. Based on the average junction temperature and preset junction temperature of the power devices within the target duration, a power device on-current limit is determined. By suppressing the current flowing through the power devices below this limit, the average junction temperature of the power devices can be kept within the preset junction temperature range.

[0131] If the power device's on-current limit is greater than or equal to the system's required current in the next cycle, it indicates that the system's required current in the next cycle is safe for the power device. The power device's required current in the next cycle can be adjusted to match the system's required current, ensuring the power device operates according to the target power without being damaged by overcurrent. If the power device's on-current limit is less than the system's required current in the next cycle, it indicates that if the current flowing through the power device is equal to the system's required current in the next cycle, the power device will be in an overload state or generate excessive heat, leading to an overtemperature state. Therefore, the power device's required current in the next cycle should be controlled to match the power device's on-current limit to ensure that the power device's average junction temperature does not exceed the preset junction temperature and to meet the inverter controller's operating requirements as much as possible, reducing the power device's current margin.

[0132] In addition, after determining the current required by the power device in the next cycle, the required duty cycle of the power device in the next cycle can be determined by the difference between the required current of the power device in the next cycle and the current actual conduction current of the power device. The specific method for obtaining the required duty cycle of the power device in the next cycle has been explained in detail in the above embodiments, and will not be repeated here.

[0133] Reference Figure 7 , Figure 7 yes Figure 1 The detailed flowchart of step S102 is as follows: Figure 7 In the example, step S102 includes, but is not limited to, the following steps:

[0134] Step S701: Obtain the instantaneous temperature increment of the power device based on the product of instantaneous power loss and instantaneous thermal resistance.

[0135] Step S702: Obtain the instantaneous junction temperature of the power device based on the sum of the instantaneous temperature increment and the instantaneous casing temperature.

[0136] Understandably, since the actual operating temperature of the semiconductor in a power device is higher than the temperature of its casing, the actual operating temperature of the semiconductor, i.e., the instantaneous junction temperature, is calculated by determining the temperature difference between the semiconductor and the casing, and then using this temperature difference and the instantaneous casing temperature. The temperature difference between the semiconductor and the casing can be calculated using the power device's heat dissipation power and thermal resistance. The power loss of the power device is its heat dissipation power; therefore, the temperature difference between the semiconductor and the casing at the current moment, i.e., the instantaneous temperature increment of the power device, can be determined by multiplying the instantaneous power loss power and the instantaneous thermal resistance. By adding the instantaneous temperature increment of the power device to the instantaneous casing temperature, the instantaneous junction temperature of the power device can be accurately determined, enabling timely and accurate protection of the power device and ensuring the stable normal operation of the system.

[0137] It should be noted that the operating parameters include the current actual on-state current and the current actual on-state voltage of the power device. By multiplying the current actual on-state current flowing through the power device and the current actual on-state voltage applied to the power device, the instantaneous power loss of the power device under the current pulse can be obtained. This allows for the determination of the real-time power loss of the power device, enabling more accurate calculation of the instantaneous junction temperature of the power device and improving the accuracy of protection and control.

[0138] It should be noted that instantaneous power loss can also be calculated using at least two of the following parameters: the operating current, operating voltage, and resistance of the power device. For example, instantaneous power loss can be calculated by multiplying the square of the operating current by the resistance of the power device, or by quotienting the square of the operating voltage by the resistance of the power device. Furthermore, instantaneous power loss can also be calculated based on other factors such as ambient temperature and the operating conditions of the power device, or it can be a fixed parameter value set externally.

[0139] Reference Figure 8 , Figure 8 yes Figure 1 The detailed flowchart of step S102 is as follows: Figure 8 In the example, step S102 includes, but is not limited to, the following steps:

[0140] Step S801: Obtain the average temperature increment of the power device based on the product of the average power loss and the steady-state thermal resistance.

[0141] Step S802: The average junction temperature of the power device is obtained based on the sum of the average temperature increment and the average case temperature.

[0142] Understandably, since the actual operating temperature of the semiconductor in a power device is higher than its case temperature, the actual operating temperature of the semiconductor, i.e., the average junction temperature, is calculated by determining the temperature difference between the semiconductor and the case over a target duration. This temperature difference, along with the average case temperature, is then used to calculate the actual operating temperature of the semiconductor. The average temperature increment is determined based on the average power loss and the steady-state thermal resistance of the power device. This average temperature increment is the difference between the average junction temperature and the average case temperature of the power device over the target duration, denoted as ΔT. jc =P×R th =T j -T c , where ΔT jc R represents the average temperature increment of the power device over the target duration, P represents the average power loss of the power device over the target duration, and R represents the average temperature increment of the power device over the target duration. th T represents the thermal resistance of a power device. j T represents the average junction temperature of the power device over the target duration. c This represents the average case temperature of the power device over the target duration. Therefore, the average junction temperature of the power device can be accurately determined, enabling timely and accurate protection of the power device and ensuring stable system operation.

[0143] It should be noted that the average power loss can be calculated based on the instantaneous power loss and the target duration, and can also be calculated using other factors such as ambient temperature and the operating conditions of the power devices. Operating parameters include the average current and average voltage of the power devices within the target duration. By multiplying the average current flowing through the power device and the average voltage applied to it, the average power loss of the power device within the target duration can be obtained. This allows for the determination of the heat generated by the power device within the target duration, enabling a more accurate calculation of the average junction temperature of the power device and improving the accuracy of protection and control.

[0144] Reference Figure 9 , Figure 9 A schematic diagram illustrating the preset thermal impedance-time ratio is shown. In this diagram, the horizontal axis represents the transient conduction time, and the vertical axis represents the thermal impedance. Figure 9 As can be seen, the instantaneous thermal impedance increases with the increase of the transient conduction time. The instantaneous thermal impedance can be determined by the transient conduction time and tends to stabilize after a certain period of time.

[0145] It is understandable that the target duration is the time it takes for the instantaneous thermal resistance of the power device to reach a stable value within a preset thermal resistance-time ratio, and the thermal resistance-time ratio is an inherent physical property of the power device. The initial value can refer to the thermal resistance of the power device during its non-conducting operation time, or it can be set according to actual usage conditions. The time point when the instantaneous thermal resistance reaches a stable value can refer to the time when the rate of change of thermal resistance within the following 1ms is less than one-thousandth, or it can refer to the time when the instantaneous thermal resistance reaches 99% of the steady-state thermal resistance value. This embodiment does not specifically limit the target duration, as long as it represents the time when the instantaneous thermal resistance of the power device tends to a stable value. Within the target duration, the junction-case thermal resistance of the power device can tend to stabilize, thus allowing for the calculation of the average junction temperature of the power device through steady-state thermal resistance, resulting in more accurate calculation results with smaller errors.

[0146] It should be noted that the target duration can be equal to or greater than the time it takes for the instantaneous thermal impedance of the power device to stabilize, as long as the calculation error of the average junction temperature can be reduced. All of these are within the protection scope of this embodiment.

[0147] It is understandable that the control signal for a power device includes a pre-set pulse period and a corresponding duty cycle. The duty cycle refers to the proportion of the on-time relative to the total cycle time within one pulse cycle, equivalent to the pulse width. Therefore, the on-time of the power device within one pulse cycle, i.e., the transient on-time, can be determined by the duty cycle and pulse period. Power devices typically begin to heat up from the moment of on-time, and their thermal resistance starts to rise, stabilizing after a certain period. The thermal resistance corresponding to different transient on-times may be different. Therefore, the instantaneous thermal resistance corresponding to the current transient on-time can be determined using a pre-set thermal resistance-time ratio. Simultaneously, the corresponding steady-state thermal resistance can be determined by the target duration.

[0148] It should be noted that the instantaneous thermal impedance of power devices usually stabilizes in a short time, and the transient conduction time is even shorter than the target duration. Therefore, by adjusting the duty cycle of the control signal through the average junction temperature and instantaneous junction temperature, the response time is short, which can promptly adjust the operating state of the power device when it is overcurrent or overtemperature, thereby avoiding damage to the power device due to overcurrent or overtemperature to a certain extent and improving the stability of the system.

[0149] Reference Figure 10 , Figure 10 This is a schematic flowchart of the protection and control method for the power device of the present invention. Wherein, v ce i is the current actual on-state voltage of the power device. cP is the current actual on-state current of the power device. Loss_pulse Z represents the instantaneous power loss of the power device. thjc_pulse T represents the instantaneous thermal impedance of the power device. j_pulse T represents the instantaneous junction temperature of the power device. c This refers to the instantaneous casing temperature of the power device. The first preset junction temperature for the power device, ΔT jc_pluse D represents the instantaneous temperature increment of the power device. th D is the duty cycle limit value for the power device. set P represents the required duty cycle of the power device in the next cycle. Loss_ave Z represents the average power loss of the power device. thjc_ave T is the steady-state thermal impedance of the power device. j_ave T represents the average junction temperature of the power device. c_ave The average case temperature of the power device. The second preset junction temperature for the power device, ΔT jc_ave i represents the average temperature increment of the power device. th i represents the adjustable current of the power device. set This is the current required by the system for the next cycle of the power device.

[0150] The system monitors the current on-state current, on-state voltage, and instantaneous case temperature of the power device in real time. It calculates the instantaneous power loss using the current on-state voltage and current, and then determines the average power loss within the target duration. The instantaneous temperature increment of the power device is calculated by combining the instantaneous power loss and the instantaneous thermal impedance. The instantaneous junction temperature is then determined by summing the instantaneous case temperature and the instantaneous temperature increment. Similarly, the average temperature increment of the power device is calculated by combining the average power loss and the steady-state thermal impedance. The average junction temperature is then determined by summing the average case temperature and the average temperature increment. The duty cycle limit is determined by comparing the difference between the first preset junction temperature and the instantaneous junction temperature. Finally, the on-state current limit is determined by comparing the second preset junction temperature and the average junction temperature. After obtaining the power device's on-current limit, this limit is compared with the system's required current for the next cycle. It is then determined whether the required current is too high. If so, the power device's on-current limit is taken as the required current for the next cycle. This required current is then compared with the current actual on-current of the power device to determine the actual change in current, thus obtaining the required duty cycle for the power device in the next cycle. Finally, the required duty cycle is compared with the power device's duty cycle limit, and the smaller of the two is taken as the duty cycle of the control signal. The duty cycle of the control signal is adjusted by using the required duty cycle of the power device in the next cycle and the duty cycle limit of the power device. If the required duty cycle of the power device in the next cycle does not exceed the duty cycle limit, the power device operates within the required duty cycle of the next cycle. If the required duty cycle of the power device in the next cycle exceeds the duty cycle limit, the power device operates within the duty cycle limit. This achieves a balance between average junction temperature and instantaneous junction temperature for power device control. Therefore, the instantaneous junction temperature and average junction temperature of the power device are determined by the case temperature, power loss, and thermal impedance. Using instantaneous junction temperature and average junction temperature as control targets, and combining the differences between instantaneous junction temperature and average junction temperature and their respective junction temperature thresholds, the control signals of power devices are comprehensively adjusted to improve the response speed and stability of power device protection. This allows the operating temperature of power devices to be quickly and stably suppressed within the normal operating range, avoiding untimely protection that could lead to excessively high operating temperatures of power devices or over-protection that could cause system shutdown. This enables timely and rapid protection of power devices and improves their stability.

[0151] refer to Figure 11 , Figure 11The present invention provides a schematic diagram of the structure of the operation control device 1100 according to a second aspect embodiment of the present invention. The operation control device 1100 includes: a memory 1110, a processor 1120 and a computer program stored in the memory 1110 and executable on the processor 1120. When the processor 1120 executes the computer program, it implements the protection control method for power devices as described in the above embodiment.

[0152] The memory 1110, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs and non-transitory computer-executable programs, such as the power device protection and control method in the above embodiments of the present invention. The processor 1120 implements the power device protection and control method in the above embodiments of the present invention by running the non-transitory software program and instructions stored in the memory 1110.

[0153] The memory 1110 may include a program storage area and a data storage area. The program storage area may store the operating system and application programs required for at least one function; the data storage area may store data required for executing the protection and control method of the power device in the above embodiments. Furthermore, the memory 1110 may include high-speed random access memory 1110, and may also include non-transitory memory 1110, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. It should be noted that the memory 1110 may optionally include memory 1110 remotely located relative to the processor 1120, and these remote memories 1110 can be connected to the terminal via a network. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0154] The non-transient software program and instructions required to implement the power device protection and control method in the above embodiments are stored in memory. When executed by one or more processors, the power device protection and control method in the above embodiments is executed, for example, the method described above is executed. Figure 1 Method steps S101 to S103, Figure 2 Method steps S201 to S203, Figure 3 Method steps S301 to S303, Figure 4 Method steps S401 to S402, Figure 5 Method steps S501 to S502, Figure 6 Method steps S601 to S602, Figure 7 Method steps S701 to S702 and Figure 8 The method steps S801 to S802.

[0155] A third aspect embodiment of the present invention provides a frequency converter controller, which includes an operation control device 1100 as provided in the second aspect embodiment. By detecting the operating parameters of a power device, the instantaneous junction temperature of the power device at the current moment and the average junction temperature over a target duration are calculated. By comparing the difference between the instantaneous junction temperature and the preset junction temperature, the instantaneous operating state of the power device at the current moment can be determined, and by comparing the difference between the average junction temperature and the preset junction temperature, the average operating state of the power device over the target duration can be determined. The average operating state can be characterized as a combination of multiple instantaneous operating states over the target duration. Both the instantaneous operating state and the average operating state can reflect whether the temperature of the power device has been adjusted, and the magnitude of the difference can determine the adjustment range required by the control signal, so that the instantaneous junction temperature and the average junction temperature of the power device can be quickly adjusted to below the preset junction temperature range. Compared to related technologies that rely solely on the current flowing through the device for control, this invention utilizes the difference between the instantaneous junction temperature and / or average junction temperature of the power device and a preset junction temperature to adjust the control signal of the power device. This improves the response speed and stability of the power device protection, taking into account both the instantaneous and average junction temperatures. It quickly and stably suppresses the operating temperature of the power device within the preset junction temperature range, avoiding untimely protection that could lead to excessively high operating temperatures of the power device or over-protection that could cause system shutdown.

[0156] It should be noted that the protection and control methods for power devices can be applied to frequency converters, as well as to products that use power devices as switching transistors, such as air conditioners, washing machines, refrigerators, and elevators.

[0157] A fourth aspect of the present invention provides a computer-readable storage medium storing computer-executable instructions that can be used to cause a computer to perform the protection control method for a power device as described in the first aspect above, for example, performing the above-described... Figure 1 Method steps S101 to S103, Figure 2 Method steps S201 to S203, Figure 3 Method steps S301 to S303, Figure 4 Method steps S401 to S402, Figure 5 Method steps S501 to S502, Figure 6 Method steps S601 to S602, Figure 7 Method steps S701 to S702 and Figure 8 The method steps S801 to S802.

[0158] It will be understood by those skilled in the art that all or some of the steps and systems in the methods disclosed above can be implemented as software, firmware, hardware, and suitable combinations thereof. Some or all of the physical components can be implemented as software executed by a processor, such as a central processing unit, digital signal processor, or microprocessor, or as hardware, or as an integrated circuit, such as an application-specific integrated circuit. Such software can be distributed on a computer-readable medium, which may include computer storage media or non-transitory media and communication media or transient media. As is known to those skilled in the art, the term computer storage media includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information such as computer-readable instructions, data structures, program modules, or other data. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technologies, CD-ROM, digital versatile disc DVD or other optical disc storage, magnetic cartridges, magnetic tape, disk storage or other magnetic storage devices, or any other medium that can be used to store desired information and is accessible to a computer. Furthermore, as is known to those skilled in the art, communication media typically contain computer-readable instructions, data structures, program modules, or other data in modulated data signals such as carrier waves or other transmission mechanisms, and may include any information delivery medium.

[0159] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A protection and control method for power devices, characterized in that, include: The instantaneous casing temperature, instantaneous thermal resistance, and instantaneous power loss of the power device at the current moment are obtained, as well as the average casing temperature, steady-state thermal resistance, and average power loss over the target duration. The instantaneous temperature increment of the power device is obtained by multiplying the instantaneous power loss and the instantaneous thermal impedance. The instantaneous junction temperature of the power device is obtained by summing the instantaneous temperature increment and the instantaneous casing temperature. The average temperature increment of the power device is obtained by multiplying the average power loss and the steady-state thermal impedance. The average junction temperature of the power device is obtained by summing the average temperature increment and the average case temperature. The duty cycle limit value of the power device is determined based on the difference between the instantaneous junction temperature and the preset junction temperature. Based on the difference between the average junction temperature and the preset junction temperature, the required duty cycle of the power device in the next cycle is determined. Based on the duty cycle limit of the power device and the required duty cycle of the power device in the next cycle, the duty cycle of the control signal of the power device is adjusted so that the instantaneous junction temperature and the average junction temperature are not higher than the preset junction temperature.

2. The protection and control method according to claim 1, characterized in that, The preset junction temperature includes a first preset junction temperature and a second preset junction temperature, wherein the first preset junction temperature and the second preset junction temperature may be the same or different.

3. The protection and control method according to claim 1, characterized in that, The step of adjusting the duty cycle of the control signal of the power device according to the duty cycle limit value of the power device and the required duty cycle of the power device in the next cycle includes: In response to the power device duty cycle limit value being less than the power device duty cycle required for the next cycle, the power device duty cycle limit value is used to adjust the duty cycle of the control signal of the power device. In response to the power device duty cycle limit value being equal to the power device duty cycle required for the next cycle, the duty cycle of the control signal for the power device is adjusted using the power device duty cycle limit value or the power device duty cycle required for the next cycle. In response to the power device's duty cycle limit being greater than the power device's required duty cycle for the next cycle, the duty cycle of the control signal for the power device is adjusted using the power device's required duty cycle for the next cycle.

4. The protection and control method according to claim 1, characterized in that, The step of determining the power device duty cycle limit value based on the difference between the instantaneous junction temperature and the preset junction temperature includes: In response to the difference between the instantaneous junction temperature and the preset junction temperature being greater than zero, the duty cycle limit value of the power device is gradually reduced by control adjustment; or, In response to the difference between the instantaneous junction temperature and the preset junction temperature being less than zero, the duty cycle limit value of the power device is gradually increased by control adjustment.

5. The protection and control method according to claim 1, characterized in that, The step of determining the required duty cycle of the power device in the next cycle based on the difference between the average junction temperature and the preset junction temperature includes: The on-current limit value of the power device is determined based on the difference between the average junction temperature and the preset junction temperature. The required duty cycle of the power device in the next cycle is obtained based on the power device's on-current limit, the system's required current in the next cycle, and the current actual on-current of the power device.

6. The protection and control method according to claim 5, characterized in that, The process of obtaining the required duty cycle of the power device in the next cycle based on the power device's on-current limit, the system's required current in the next cycle, and the current actual on-current of the power device includes: In response to the power device on-current limit being greater than or equal to the system current required in the next cycle, the system current required in the next cycle is taken as the power device current required in the next cycle, and the required on-duty cycle of the power device in the next cycle is obtained based on the power device current required in the next cycle and the current actual on-current of the power device. In response to the fact that the power device's on-current limit is less than the current required by the system in the next cycle, the power device's on-current limit is taken as the current required by the power device in the next cycle. Then, the required duty cycle of the power device in the next cycle is obtained based on the current required by the power device in the next cycle and the current actual on-current of the power device.

7. The protection and control method according to any one of claims 1 to 6, characterized in that, The target duration is the time it takes for the instantaneous thermal impedance of the power device to approach a stable value from its initial value within the preset thermal impedance-time ratio.

8. An operation control device, characterized in that, It includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the protection control method for the power device as described in any one of claims 1 to 6.

9. A frequency converter, characterized in that, Includes the operation control device as described in claim 8.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-executable instructions for causing a computer to perform the protection control method for the power device as described in any one of claims 1 to 6.

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