CN115903948A - Protection and control method, device, frequency conversion controller, and storage medium for power devices - Google Patents

Abstract

The present invention proposes a protection control method, device, frequency conversion controller, and storage medium for a power device. The protection control method includes: obtaining the working parameters of the power device; determining the instantaneous junction temperature of the power device according to the working parameters and the average junction temperature within the target time period; obtain the difference between the instantaneous junction temperature/or the average junction temperature and a preset junction temperature, and adjust the control signal of the power device according to the difference, so that all Neither the instantaneous junction temperature nor the average junction temperature is higher than the preset junction temperature. The invention can take into account the instantaneous junction temperature and 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 working temperature of the power device within the normal working range.

Description

Protection and control method, device, frequency conversion controller, and storage medium for power devices

technical field

The present invention relates to the technical field of electronic devices, in particular to a protection and control method, device, frequency conversion controller and storage medium for power devices.

Background technique

At present, in electrical systems, electrical control equipment is usually controlled by power devices, but the overload resistance of power devices is usually low, and power devices are easily damaged by overload. In related technologies, only the current value flowing through the power device is used as the protection basis to control the power device to be turned off, but the control accuracy of the power device is not high enough, the response is slow, and the protection is not timely or over-protected only relying on the current value flowing through. This makes the system unable to operate normally and stably, causing premature aging and even damage of power devices. Therefore, how to quickly protect the power devices while the stable system is running normally has become an urgent problem to be solved.

Contents of the invention

The present invention aims to solve at least one of the technical problems existing in the prior art. For this reason, the present invention proposes a protection control method, device, frequency conversion controller and storage medium of a power device, which can speed up the protection response speed, quickly adjust the power device under the normal operation of the stable system, and improve the stability of the power device. sex.

In a first aspect, an embodiment of the present invention provides a protection control method for a power device, the protection control method comprising:

Obtaining operating parameters of the power device;

determining the instantaneous junction temperature of the power device and the average junction temperature within a target time period according to the operating parameters;

Obtaining 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 according to the difference, so that neither the instantaneous junction temperature nor the average junction temperature above the preset junction temperature.

According to the protection control method provided by the embodiment of the present invention, at least the following beneficial effects are obtained: by detecting the operating parameters of the power device, and calculating the instantaneous junction temperature of the power device at the current moment, and the average junction temperature within the target time period . By comparing the difference between the instantaneous junction temperature and the preset junction temperature, it is possible to judge the instantaneous working state of the power device at the current moment, and by comparing the difference between the average junction temperature and the preset junction temperature, it is possible to judge the average operation of the power device within the target time period state. The average working state can be characterized as the synthesis of multiple instantaneous working states within the target time period. Both the instantaneous working state and the average working state can reflect whether the temperature of the power device is adjusted, and the size of the difference can determine the adjustment required for the control signal Amplitude, so that the instantaneous junction temperature and average junction temperature of power devices can be quickly adjusted below the preset junction temperature range. Compared with the technical solution in the related art that only relies on the current value flowing through to control the power device, the present invention uses the difference between the instantaneous junction temperature of the power device and/or the difference between the average junction temperature and the preset junction temperature to control the power device The signal is adjusted to improve the response speed of the protection of the power device and the stability of the power device, taking into account the instantaneous junction temperature and the average junction temperature of the power device, and quickly and stably suppress the operating temperature of the power device within the preset junction temperature range , to avoid the overheating of power devices caused by untimely protection or system shutdown caused by overprotection.

In the above protection control method, the preset junction temperature includes a first preset junction temperature and a second preset junction temperature, and the first preset junction temperature and the second preset junction temperature are the same or different.

Due to the temperature rise caused by pulses in a short period of time, it is easy to cause the instantaneous temperature of the power device to exceed the preset junction temperature, but if the power device is in an overheated state for a long time, it will cause damage to the power device. The junction temperature requirements can be the same or different, so that the first preset junction temperature and the second preset junction temperature can be set respectively for the instantaneous junction temperature and the average junction temperature, and 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.

In the above protection control method, the acquisition of the difference between the instantaneous junction temperature/or the average junction temperature and a preset junction temperature, and adjusting the control signal of the power device according to the difference includes:

According to the difference between the instantaneous junction temperature and the preset junction temperature, determine the limit value of the conduction duty cycle of the power device;

According to the difference between the average junction temperature and the preset junction temperature, determine the conduction duty cycle required by the power device in the next cycle;

The conduction duty cycle of the control signal of the power device is adjusted according to the limit value of the conduction duty cycle of the power device and the required conduction duty cycle of the power device in the next cycle.

By adjusting the conduction duty cycle of the control signal, the heat generation of the power device is changed, thereby adjusting the temperature of the power device. Therefore, the limit value of the conduction duty cycle of the power device is characterized as the corresponding upper limit duty cycle adjustment parameter for the real-time temperature of the power device, because the limit value of the conduction duty cycle of the power device is determined according to the instantaneous junction temperature, and the instantaneous junction temperature Real-time detection, so that the limit value of the conduction duty cycle of the power device is updated in real time, and the conduction time of the power device can be suppressed in time to protect the power device. The conduction duty cycle required by the power device in the next cycle is characterized by the average junction temperature of the power device and the conduction duty cycle required for the required power in the next cycle, so that the limit value of the conduction duty cycle of the power device can be compared to The conduction duty cycle required by the power device in the next cycle is adjusted to maintain the average junction temperature and instantaneous junction temperature of the power device within the target time period within the preset junction temperature.

In the above protection control method, the conduction duty of the control signal of the power device is adjusted according to the conduction duty ratio limit value of the power device and the required conduction duty ratio of the power device in the next cycle. adjustments, including:

In response to the conduction duty cycle limit value of the power device being less than the required conduction duty cycle of the power device in the next cycle, the conduction of the control signal of the power device is performed using the power device conduction duty cycle limit value The duty cycle is adjusted;

In response to the conduction duty cycle limit value of the power device being equal to the conduction duty cycle required by the power device in the next cycle, adopting the conduction duty cycle limit value of the power device or the power device in the next cycle The conduction duty ratio of the control signal of the power device is required to adjust the conduction duty ratio;

In response to the conduction duty cycle limit value of the power device being greater than the required conduction duty cycle of the power device in the next cycle, the control signal of the power device is controlled by using the conduction duty cycle required by the power device in the next cycle The conduction duty cycle is adjusted.

By comparing the limit value of the conduction duty cycle of the power device with the required conduction duty cycle of the power device in the next cycle, the limit value of the conduction duty cycle of the power device is used to limit the required conduction duty cycle of the power device in the next cycle Amplitude suppression can quickly suppress the conduction working time of the power device and suppress the heat generation, so as to quickly reduce the junction temperature, avoid the sharp increase in the heat generation caused by the rapid extension of the conduction work time, and improve the temperature stability of the power device.

In the above protection control method, the limit value of the conduction duty cycle of the power device is determined according to the difference between the instantaneous junction temperature and the preset junction temperature, including:

Responding to a difference between the instantaneous junction temperature and the preset junction temperature being greater than zero, gradually reducing the conduction duty cycle limit value of the power device through control adjustment;

or,

In response to the difference between the instantaneous junction temperature and the preset junction temperature being less than zero, gradually increase the conduction duty cycle limit value of the power device through control adjustment.

When the difference between the instantaneous junction temperature and the preset junction temperature is greater than or equal to zero, it can be considered that the power device is overheated. Therefore, by gradually reducing the limit value of the power device conduction duty cycle at the previous moment of the control signal, the The limit value of the conduction duty cycle of the power device is updated to quickly shorten the conduction working time of the power device, quickly reduce heat generation, and thereby reduce the operating temperature of the power device in time. When the difference between the instantaneous junction temperature and the preset junction temperature is less than zero, it can be considered that the power device is in a normal working state, so that the power device conduction duty cycle limit value of the control signal can be gradually adjusted according to the actual power demand. The increase can quickly increase the operating power of the system.

In the above protection control method, according to the difference between the average junction temperature and the preset junction temperature, the conduction duty cycle required by the power device in the next cycle is determined, including:

determining a conduction current limit value of a power device according to the difference between the average junction temperature and the preset junction temperature;

According to the conduction current limit value of the power device, the current required by the system in the next cycle and the conduction current of the current actual power device, the required conduction duty cycle of the power device in the next cycle is obtained.

According to the difference between the average junction temperature and the preset junction temperature, the current value that needs to be changed when the average junction temperature is adjusted to the preset junction temperature is judged, so as to determine the maximum current flowing through the power device, that is, the conduction current limit value of the power device , and then obtain the corresponding turn-on duty cycle of the power device in the next cycle, so as to determine the maximum allowable turn-on time through the maximum allowable current value flowing through the power device, and maintain the average temperature of the power device.

In the above-mentioned protection control method, the conduction duty cycle required by the power device in the next cycle is obtained according to the limit value of the conduction current of the power device, the current required by the system in the next cycle, and the conduction current of the current actual power device, including:

Responding to the fact that the current limit value of the power device is greater than or equal to the current required by the system in the next cycle, the current required by the system in the next cycle is used as the current required by the power device in the next cycle, and then according to the current required by the power device in the next cycle The required current and the conduction current of the current actual power device obtain the conduction duty cycle required by the power device in the next cycle;

In response to the limit value of the conduction current of the power device being less than the current required by the system in the next cycle, the limit value of the conduction current of the power device is used as the current required by the power device in the next cycle, and then according to the current required by the power device in the next cycle The required current and the conduction current of the current actual power device are used to obtain the conduction duty cycle required by the power device in the next cycle.

After determining the limit value of the conduction current of the power device based on the difference between the average junction temperature and the preset junction temperature, compare the limit value of the conduction current of the power device with the current required by the system in the next cycle, and the current required by the system in the next cycle It is characterized by the current value required for the system to operate at the target power, and the smaller value of the two is used to adjust the current value, so as to avoid overloading the power device due to excessive current value and protect the power device.

In the above protection control method, the working parameters include the instantaneous case temperature, instantaneous thermal impedance and instantaneous power loss of the power device at the current moment;

The determining the instantaneous junction temperature of the power device according to the operating parameters includes:

Obtaining the instantaneous temperature increment of the power device according to the product of the instantaneous power loss and the instantaneous thermal impedance;

According to the sum of the instantaneous temperature increment and the instantaneous case temperature, the instantaneous junction temperature of the power device is obtained.

Since the actual temperature of the semiconductor is higher than the temperature of the casing during the working process of the power device, and the actual temperature of the semiconductor is difficult to measure, the power device dissipated by combining the instantaneous thermal impedance and instantaneous power loss of the power device is calculated. Combined with the instantaneous case temperature of the power device at the current moment, the instantaneous junction temperature of the power device at the current moment can be calculated, and multiple operating parameters of the power device can be integrated to accurately judge the real-time working status of the power device and protect the power in time. device.

In the above protection control method, the working parameters include the average case temperature, steady-state thermal impedance and average power loss of the power device within the target time period;

The determining the average junction temperature of the power device within the target time period according to the operating parameters includes:

Obtaining the average temperature increment of the power device according to the product of the average power loss and the steady-state thermal impedance;

According to the sum of the average temperature increment and the average case temperature, the average junction temperature of the power device is obtained.

The heat dissipated by the power device within the target time period is determined by the average power loss of the power device within the target time period and the steady-state thermal resistance of the power device, that is, the difference between the average junction temperature and the average case temperature of the power device within the target time period The difference, so that the average junction temperature of the power device can be determined. By integrating multiple operating parameters of the power device within the target time, the working state of the power device within the target time can be judged, and the stability of the operating temperature of the power device can be maintained.

In the above protection control method, the target duration is the duration for the instantaneous thermal impedance of the power device to reach a stable value from an initial value in a preset thermal impedance-duration proportional relationship.

Thermal impedance is an inherent physical property of power devices. Power devices usually start to generate heat when they are powered on, and the thermal impedance begins to rise. After a certain period of time, it tends to be stable, and the rate of temperature change is unstable. Therefore, you can use the preset thermal impedance- The proportional relationship of the time length determines the time required for the thermal impedance of the power device to reach stability, and the measurement of the working parameters by using the target time length can reduce the error caused by the fluctuation of the thermal impedance.

In the second aspect, an embodiment of the present invention provides an operation control device, including a memory, a processor, and a computer program stored on the memory and operable on the processor. When the processor executes the computer program, The protection and control method described in the embodiment of the first aspect above is realized.

The operation control device provided according to the embodiment of the present invention has at least the following beneficial effects: by detecting the operating parameters of the power device, and calculating the instantaneous junction temperature of the power device at the current moment, and the average junction temperature within the target time period . By comparing the difference between the instantaneous junction temperature and the preset junction temperature, it is possible to judge the instantaneous working state of the power device at the current moment, and by comparing the difference between the average junction temperature and the preset junction temperature, it is possible to judge the average operation of the power device within the target time period state. The average working state can be characterized as the synthesis of multiple instantaneous working states within the target time period. Both the instantaneous working state and the average working state can reflect whether the temperature of the power device is adjusted, and the size of the difference can determine the adjustment required for the control signal Amplitude, so that the instantaneous junction temperature and average junction temperature of power devices can be quickly adjusted below the preset junction temperature range. Compared with the technical solution in the related art that only relies on the current value flowing through to control the power device, the present invention uses the difference between the instantaneous junction temperature of the power device and/or the difference between the average junction temperature and the preset junction temperature to control the power device The signal is adjusted to improve the response speed of the protection of the power device and the stability of the power device, taking into account the instantaneous junction temperature and the average junction temperature of the power device, and quickly and stably suppress the operating temperature of the power device within the preset junction temperature range , to avoid the overheating of power devices caused by untimely protection or system shutdown caused by overprotection.

In a third aspect, an embodiment of the present invention provides a frequency conversion controller, including the operation control device described in the embodiment of the second aspect above.

The frequency conversion controller provided according to the embodiment of the present invention has at least the following beneficial effects: by detecting the operating parameters of the power device, and calculating the instantaneous junction temperature of the power device at the current moment, and the average junction temperature within the target time period . By comparing the difference between the instantaneous junction temperature and the preset junction temperature, it is possible to judge the instantaneous working state of the power device at the current moment, and by comparing the difference between the average junction temperature and the preset junction temperature, it is possible to judge the average operation of the power device within the target time period state. The average working state can be characterized as the synthesis of multiple instantaneous working states within the target time period. Both the instantaneous working state and the average working state can reflect whether the temperature of the power device is adjusted, and the size of the difference can determine the adjustment required for the control signal Amplitude, so that the instantaneous junction temperature and average junction temperature of power devices can be quickly adjusted below the preset junction temperature range. Compared with the technical solution in the related art that only relies on the current value flowing through to control the power device, the present invention uses the difference between the instantaneous junction temperature of the power device and/or the difference between the average junction temperature and the preset junction temperature to control the power device The signal is adjusted to improve the response speed of the protection of the power device and the stability of the power device, taking into account the instantaneous junction temperature and the average junction temperature of the power device, and quickly and stably suppress the operating temperature of the power device within the preset junction temperature range , to avoid the overheating of power devices caused by untimely protection or system shutdown caused by overprotection.

In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, the computer-readable storage medium stores computer-executable instructions, and the computer-executable instructions are used to make a computer perform the above-mentioned first aspect embodiment. protection control method.

The computer-readable storage medium provided according to the embodiments of the present invention has at least the following beneficial effects: by detecting the operating parameters of the power device, and calculating the instantaneous junction temperature of the power device at the current moment, and the average junction temperature within the target time period junction temperature. By comparing the difference between the instantaneous junction temperature and the preset junction temperature, it is possible to judge the instantaneous working state of the power device at the current moment, and by comparing the difference between the average junction temperature and the preset junction temperature, it is possible to judge the average operation of the power device within the target time period state. The average working state can be characterized as the synthesis of multiple instantaneous working states within the target time period. Both the instantaneous working state and the average working state can reflect whether the temperature of the power device is adjusted, and the size of the difference can determine the adjustment required for the control signal Amplitude, so that the instantaneous junction temperature and average junction temperature of power devices can be quickly adjusted below the preset junction temperature range. Compared with the technical solution in the related art that only relies on the current value flowing through to control the power device, the present invention uses the difference between the instantaneous junction temperature of the power device and/or the difference between the average junction temperature and the preset junction temperature to control the power device The signal is adjusted to improve the response speed of the protection of the power device and the stability of the power device, taking into account the instantaneous junction temperature and the average junction temperature of the power device, and quickly and stably suppress the operating temperature of the power device within the preset junction temperature range , to avoid the overheating of power devices caused by untimely protection or system shutdown caused by overprotection.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description as well as the appended drawings.

Description of drawings

Below in conjunction with accompanying drawing and embodiment the present invention is further described;

FIG. 1 is a flowchart of a protection control method for a power device provided by an embodiment of the present invention;

Fig. 2 is the specific flowchart of step S103 in Fig. 1;

Fig. 3 is the specific flowchart of step S203 in Fig. 2;

Fig. 4 is the specific flowchart of step S201 in Fig. 2;

Fig. 5 is the specific flowchart of step S202 in Fig. 2;

Fig. 6 is the specific flowchart before step S502 in Fig. 5;

Fig. 7 is the specific flowchart of step S102 in Fig. 1;

Fig. 8 is the specific flowchart of step S102 in Fig. 1;

FIG. 9 is a schematic diagram of a preset thermal impedance-duration proportional relationship;

FIG. 10 is a schematic flowchart of a protection control method for a power device of the present invention;

Fig. 11 is a schematic structural diagram of an operation control device provided by an embodiment of the present invention.

Detailed ways

This part will describe the specific embodiment of the present invention in detail, and the preferred embodiment of the present invention is shown in the accompanying drawings. Each technical feature and overall technical solution of the invention, but it should not be understood as a limitation on the protection scope of the present invention.

It should be understood that in the description of the embodiments of the present invention, if there are descriptions of "first", "second", etc., it is only for the purpose of distinguishing technical features, and should not be understood as indicating or implying relative importance or implicitly indicating The number of indicated technical features or implicitly indicates the order of the indicated technical features. "At least one" means one or more, and "plurality" 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 items or plural items.

In addition, unless otherwise clearly stipulated and limited, the term "connected/connected" should be understood in a broad sense, for example, it can be fixed or movable, detachable or non-detachable, or integrally connected; it can be A mechanical connection can also be an electrical connection or can communicate with each other; it can be a direct connection or an indirect connection through an intermediary.

In describing embodiments of the present invention, reference is made to the terms "one embodiment/implementation", "another embodiment/embodiment" or "certain embodiments/embodiments", "in the foregoing embodiments/embodiments", etc. The description means that the specific features, structures, materials or characteristics described in conjunction with the embodiments or examples are included in at least two embodiments or implementations of the present disclosure. In this disclosure, schematic representations of the above terms do not necessarily refer to the same example or implementation. It should be noted that although a logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than in the flowchart.

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 constitute conflicts with each other.

Embodiments of the present invention provide a protection control method, device, frequency conversion controller, and storage medium for a power device, using the difference between the instantaneous junction temperature of the power device and/or the difference between the average junction temperature and the preset junction temperature to control the power device The signal is adjusted to improve the response speed of the protection of the power device and the stability of the power device, taking into account the instantaneous junction temperature and the average junction temperature of the power device, and quickly and stably suppress the average junction temperature and the instantaneous junction temperature of the power device at the preset In the range of junction temperature, it is avoided that the working temperature of the power device is too high due to untimely protection or the system shutdown caused by over-protection.

The embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

Referring to FIG. 1, FIG. 1 is a flow chart of a protection and control method for a power device provided by an embodiment of the present invention. The protection and control method for a power device includes but is not limited to the following steps:

Step S101, obtaining the working parameters of the power device;

Step S102, determining the instantaneous junction temperature of the power device and the average junction temperature within the target time period according to the working parameters;

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 neither the instantaneous junction temperature nor the average junction temperature is higher than the preset junction temperature.

It can be understood that the safe and reliable operation of power devices is the key to the stable operation of electrical systems. Since the current flows through the power device, the temperature of the power device will rise, and the temperature of the power device will be damaged if the temperature is too high. However, the temperature sensor in the related art cannot directly measure the junction temperature of the semiconductor inside the power device, and can only measure the temperature of the outer shell of the power device. The temperature of the casing, and the actual temperature of the semiconductor of the power device will be higher than the temperature of the casing of the power device, and it is not accurate to use the temperature sensor to detect the working temperature of the power device.

In addition, the temperature of the environment where the power device is located, the heat dissipation conditions of the power device, the voltage applied to the power device, and the thermal impedance of the power device will all affect the operating temperature of the power device, that is, affect the working state of the power device.

Therefore, the working parameters of the power device are detected in real time, and the detected working parameters can be recorded, and the working parameters of the power device within the target time period are kept. The current operating temperature of the power device is analyzed by using the current operating parameters to determine the instantaneous junction temperature of the power device, that is, 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 by using the operating parameters within the target time period. The average junction temperature can be expressed by the average value of multiple instantaneous junction temperatures within the target time period. Therefore, the control signal of the power device can be adjusted only by using the difference between the instantaneous junction temperature and the preset junction temperature. When the instantaneous junction temperature Suppressed within the preset junction temperature range, the average junction temperature can also be suppressed within the preset junction temperature range, so that both the instantaneous junction temperature and the average junction temperature can be within the range below the preset junction temperature. In addition, only the difference between the average junction temperature and the preset junction temperature can be used to adjust the control signal of the power device. When the average junction temperature is suppressed within the preset junction temperature range, it can be considered that the power device has not been exposed to excessive temperature for a long time. Temperature state, and each instantaneous junction temperature may exceed the preset junction temperature within the target time period, but it is still within the acceptable range of power devices, and by reducing the average junction temperature, the instantaneous junction temperature can also be reduced at the same time, and the instantaneous junction temperature can also be reduced. lower than or equal to the preset junction temperature. In addition, according to the difference between the instantaneous junction temperature and the preset junction temperature, and the difference between the average junction temperature and the preset junction temperature, the control signal of the power device can be adjusted comprehensively, and the average junction temperature and the instantaneous junction temperature can be suppressed at the preset value. set within the range below the junction temperature.

Among them, since the average junction temperature needs to be obtained through the working parameters within the target time period, within one cycle, that is, within the target time period, the obtained average junction temperature is a stable value, and the instantaneous junction temperature is calculated through real-time updated working parameters Therefore, the obtained instantaneous junction temperature changes in real time, the update frequency of the instantaneous junction temperature is higher than that of the average junction temperature, the difference obtained by comparing the instantaneous junction temperature with the preset junction temperature, and the average The difference obtained by comparing the junction temperature with the preset junction temperature can determine the amount of change that needs to be adjusted in the current state of the power device, that is, the calorific value that needs to be reduced or the calorific value that can be increased. The larger the difference, the power The more heat the device needs to reduce, therefore, the real-time adjustment of the control signal of the power device through the difference can control the average junction temperature and instantaneous junction temperature below the preset junction temperature, maintain the stability of the power device temperature, and at the same time Taking into account the real-time performance of the instantaneous junction temperature, the rapid response of temperature protection can be achieved, the temperature of the power device can be controlled in multiple cycles, the power device can be quickly adjusted, and the stability of the power device can be maintained.

In addition, the target duration can be updated in real time. For example, the target duration can be a fixed-length window, and the end of the window is the current moment, so that the window keeps sliding with the current moment, and the target duration is updated in real time. Therefore, using the working parameters within the target duration The update frequency of the determined average junction temperature is the same as that of the instantaneous junction temperature, which can reflect the temperature situation of the power device in a target time period in the past and the temperature situation at the current moment in real time. Therefore, the control signal of the power device can be adjusted in real time according to the average junction temperature/or the instantaneous junction temperature, the temperature of the power device can be quickly adjusted, and the temperature of the power device can be stably maintained.

By comparing the average junction temperature and the preset junction temperature of the power device, it can be judged whether the power device is in an over-temperature state within the target time period, or by comparing the instantaneous junction temperature and the preset junction temperature of the power device, it can be judged whether the power device is in an over-temperature state at the current moment. warm state. When the power device is in an over-temperature state, it can be considered that it is necessary to cool down the power device, adjust the control signal of the power device to change the working state of the power device, reduce the heat generation of the power device, thereby reducing the junction temperature of the power device, making the instantaneous junction temperature The average junction temperature does not exceed the preset junction temperature to prevent overheating of power devices.

In related technologies, the current value flowing through the power device is used as the protection basis for the power device. When the current flowing through the power device exceeds the protection threshold, the power device is turned off until the current drops below the protection threshold, or the control signal is blocked to turn off the power device. Until the blocking time reaches the preset time and the current threshold drops below the protection threshold. Since the current flows through the power device, the temperature of the power device will rise, and switching the power device multiple times in a short period of time will increase the power loss of the power device, and the temperature will rise rapidly. If the temperature is too high, the aging and damage of the power device will be accelerated. However, if the control signal is blocked for a long time and the power device is turned off, the system cannot continue to operate stably. Therefore, using the instantaneous junction temperature and average junction temperature of the power device as the basis for protection can accurately judge the working state of the power device, achieve accurate and timely protection of the power device, and stabilize the temperature of the power device to avoid excessive protection and continue to work normally in a stable system. Protect power devices in time under running conditions.

It should be noted that the working parameters may include the case temperature of the power device, power loss, thermal impedance, and the working voltage and current of the power device. Among them, the casing temperature of the power device can be directly measured by the temperature sensor, or can be calculated by using other operating parameters of the power device, such as the ambient temperature; the operating current and operating voltage loaded on the power device can be obtained through the voltage and current detection circuit It can be detected or calculated by other working parameters.

It should be noted that due to the temperature rise caused by pulses in a short period of time, it is easy to cause the instantaneous temperature of the power device to exceed the preset junction temperature, but if the power device is in an overheated state for a long time, it will cause damage to the power device. Therefore, the power device The requirements for the instantaneous junction temperature and the average junction temperature can be the same or different, so that the first preset junction temperature and the second preset junction temperature can be set respectively for the instantaneous junction temperature and the average junction temperature, and the first preset junction temperature can be used as the instantaneous junction temperature. The upper limit of the temperature, and the second preset junction temperature can be used as the upper limit of the average junction temperature.

It should be noted that adjusting the control signal of the power device to change the working state of the power device may be to directly control the actual operating parameters of the control signal, such as at least one of the operating current, operating voltage and conduction duty cycle. It can also control the upper limit value of the operating parameter of the control signal, thereby indirectly adjusting the actual operating parameter of the power device, such as at least one of the upper limit value of the current, the upper limit value of the voltage and the upper limit value of the duty cycle kind. Therefore, the working state of the power device can be judged in real time by the difference between the instantaneous junction temperature/or the average junction temperature and the preset junction temperature, and then the control signal of the power device can be adjusted in real time to change the operating parameters of the power device so that the operating temperature of the power device be quickly controlled. 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 on-duty ratio of the control signal can be adjusted so that the on-time duration of the power device is shortened and reduced in time. The calorific value of the power device can quickly reduce the junction temperature of the power device. It can also adjust the duty cycle limit value of the control signal, limit the conduction duty cycle of the control signal, shorten the maximum conduction working time of the power device, and suppress The heat generation of power devices can reduce the junction temperature of power devices. 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 conduction duty cycle of the control signal of the power device is adjusted in real time, Accurately adjust the calorific value of the power device during the on-time operation, so as to accurately adjust the working temperature of the power device, improve the response speed to the protection of the power device, and protect the power device in time. Since the on-duty cycle of the control signal takes up a relatively short time, the real-time control of the on-duty cycle of the control signal can quickly change the working state of the power device, quickly change the junction temperature of the power device, and achieve fast protection responding speed.

Referring to FIG. 2, FIG. 2 is a specific flowchart of step S103 in FIG. 1. In the example of FIG. 2, step S103 includes but is not limited to the following steps:

Step S201, according to the difference between the instantaneous junction temperature and the preset junction temperature, determine the limit value of the conduction duty ratio of the power device;

Step S202, according to the difference between the average junction temperature and the preset junction temperature, determine the conduction duty cycle required by the power device in the next cycle;

Step S203, adjusting the conduction duty cycle of the control signal of the power device according to the limit value of the conduction duty cycle of the power device and the required conduction duty cycle of the power device in the next cycle.

It can be understood that when the power device is turned on, the temperature of the power device will rise after the current flows through the power device. Therefore, the temperature of the power device can be adjusted by controlling the conduction time of the power device to control the heat generation of the power device. The power device is controlled by its corresponding control signal, and the power device conducts conduction work according to the control signal, so that by adjusting the conduction duty cycle of the control signal, the conduction duration of the power device can be controlled, and the temperature of the power device can be quickly adjusted. Effect.

Comparing the real-time instantaneous junction temperature and the preset junction temperature of the power device to obtain the difference between the two, wherein the instantaneous junction temperature can be compared with the first preset junction temperature, and it is judged that the real-time temperature of the power device at the current moment needs to be adjusted The temperature variable determines the power device conduction duty cycle limit value based on the instantaneous junction temperature, that is, the maximum allowable conduction time of the power device based on the instantaneous junction temperature, and then controls the control signal through the power device conduction duty cycle limit value The on-duty ratio of the control signal is limited and adjusted, and the on-duty ratio of the control signal is prohibited from exceeding the limit value of the on-duty ratio of the power device, so as to reduce the on-time length of the power device. When the instantaneous junction temperature is higher than the preset junction temperature, the determined conduction duty cycle limit value of the power device is smaller, so that the maximum allowable conduction working time of the power device is reduced, thereby suppressing the conduction working time of the power device, Reduce the heat generation of power devices in time, so as to quickly reduce the junction temperature of power devices. When the preset junction temperature is higher than the instantaneous junction temperature, the determined conduction duty cycle limit value of the power device is larger, so the conduction duty cycle of the control signal can be adjusted according to the actual use requirements and will not exceed the duty cycle The ratio limit value makes the system run according to the actual use demand. Therefore, based on the comparison between the instantaneous junction temperature and the preset junction temperature, the limit value of the conduction duty cycle of the power device is determined, so that the conduction duty cycle of the control signal of the power device can be controlled by using the limit value of the conduction duty cycle of the power device. The ratio is adjusted in real time to suppress the heat generated by the power device during the on-time operation, so as to suppress the operating temperature of the power device, improve the response speed to the protection of the power device, and protect the power device in time. Since the on-duty cycle of the control signal takes up a relatively short time, the real-time control of the on-duty cycle of the control signal can quickly change the working state of the power device, quickly change the junction temperature of the power device, and achieve fast protection responding speed.

In addition, the difference between the average junction temperature and the preset junction temperature of the power device within the target time period is compared, wherein the average junction temperature can be compared with the second preset junction temperature, and the second preset junction temperature can be compared with the second preset junction temperature The first preset junction temperature is the same or different, and the temperature variable that needs to be adjusted for the average temperature of the power device within the target time period is determined. Since the average junction temperature is stable within the same target time period, the average junction temperature can be determined. Find the conduction duty cycle required by the power device in the next cycle, that is, determine the conduction time required by the power device in the next cycle based on the average junction temperature or target power, and then use the conduction duty cycle required by the power device in the next cycle The conduction duty ratio of the control signal is compared to adjust, so that the power device can operate according to the target power or the average junction temperature of the power device can be stabilized within a range below the preset junction temperature. Wherein, the next cycle may be the next target duration, or multiple subsequent target durations.

Correspondingly, when the average junction temperature is higher than the preset junction temperature, and the difference is larger, the determined turn-on duty cycle of the power device in the next cycle is smaller, so the turn-on time of the power device is shorter, and the The heat is quickly suppressed and the temperature of the power device is quickly reduced.

Therefore, the conduction duty cycle of the control signal is comprehensively adjusted according to the limit value of the conduction duty cycle of the power device and the required conduction duty cycle of the power device in the next cycle, so that the conduction duty cycle cannot exceed the conduction duty cycle of the power device. The duty cycle limit value or update according to the conduction duty cycle required by the power device in the next cycle, suppress the conduction time of the power device, reduce the calorific value, achieve both real-time operating temperature and long-term operating temperature of the power device, and increase the temperature of the power device The response speed of the protection, while ensuring the stability of the long-term operating temperature of the power device.

It should be noted that the conduction duty ratio of the control signal at the next moment of the power device can be adjusted separately by using the required conduction duty ratio of the power device in the next cycle, that is, the required conduction duty ratio of the power device in the next cycle The duty cycle is only adjusted corresponding to one conduction duty cycle of the control signal, so as to achieve real-time and accurate suppression of the conduction working time of the power device and accurate control of the junction temperature of the power device. In addition, the update period of the average junction temperature corresponds to multiple pulse periods of the control signal, that is, the conduction duty cycle required by the power device in the next cycle corresponds to the multiple conduction duty cycles in the control signal, and then a next cycle The conduction duty cycle required by the periodic power device can be adjusted for multiple conduction duty cycles. Since the instantaneous junction temperature is updated in real time, the limit value of the conduction duty cycle of the power device is also updated in real time, and the conduction duty cycle of the control signal at the next moment can be individually limited and adjusted through the limit value of the conduction duty cycle of the power device. Using the instantaneous junction temperature at the current moment and the average junction temperature in the target period, one or more conduction duty cycles of the power device control signal in the next cycle can be adjusted, that is, each conduction duty cycle can be preset according to the instantaneous junction temperature The relationship between the junction temperature and the relationship between the average junction temperature and the preset junction temperature is changed to achieve the effect of accurately protecting the power device and improving the reliability of the system operation.

It should be noted that, according to the limit value of the conduction duty cycle of the power device and the conduction duty cycle required by the power device in the next cycle, the conduction duty cycle of the control signal of the power device can be adjusted, which can be set to the transient control Period and steady-state control period, in the transient control period, the conduction duty ratio of the control signal of the power device is adjusted by using the power device conduction duty ratio limit value, while in the steady-state control period, the power device of the next cycle is used The conduction duty cycle required by the device is adjusted to the conduction duty cycle of the control signal of the power device, wherein the transient control cycle and the steady state control cycle are replaced according to a preset ratio, such as the transient control cycle and the steady state control cycle Cycles are rotated in turn, or two transient control cycles are set in the interval between two steady-state control cycles.

It should be noted that, it can be understood that, by comparing the instantaneous junction temperature and the preset junction temperature, a difference between the two is obtained, that is, a first difference. The amount of calorific value that needs to be reduced by the power device in the current state can be determined through the first difference, or the power device in the current state can support an increase in temperature rise caused by increasing the operating power. The first difference is the difference between the instantaneous junction temperature minus the preset junction temperature. When the first difference is positive, it means that the instantaneous junction temperature is higher than the preset junction temperature, that is, the power device needs to reduce the conduction time Lower the temperature, and the first difference is the calorific value that the power device needs to reduce. The larger the first difference is, the greater the calorific value that the power device needs to reduce, the shorter the maximum allowable conduction time, and the power device is turned on. The smaller the duty cycle limit value, the faster the operating temperature of the power device is reduced. When the first difference is negative, it means that the instantaneous junction temperature is lower than the preset junction temperature, and the power device is in a normal state. The first difference is the increment that supports the temperature rise of the power device. The smaller the first difference, the power device The greater the range of temperature rise, the greater the maximum allowable conduction working time, and the greater the limit value of the conduction duty cycle of the power device. Therefore, by comparing the difference between the instantaneous junction temperature and the preset junction temperature as the basis for the adjustment of the limit value of the conduction duty cycle of the power device, the junction temperature of the power device can be controlled more accurately and quickly, and the power device can be protected in time. device.

It should be noted that, through the first difference between the instantaneous junction temperature and the preset junction temperature, the power device conduction duty ratio limit value can be calculated by the PID (Proportional Integral Derivative, proportional integral derivative) control system, or can be The limit value of the conduction duty cycle of the power device is determined by a proportional-integral controller. The ratio between the first difference and the instantaneous junction temperature is calculated to determine the temperature range to be adjusted based on the current instantaneous junction temperature, that is, the ratio to be adjusted. For example, if the instantaneous junction temperature is 100°C and the preset junction temperature is 120°C, then the first difference is -20°C, indicating that the limit value of the conduction duty cycle of the power device can be increased to make the instantaneous junction temperature increase The range is 20°C. The corresponding proportion to be adjusted is 20%, that is, it can be considered that under the control of the control signal of the current on-duty ratio, the junction temperature of the power device is 100°C, and there is a temperature rise range of 20% based on the current state. Therefore, the The current limit value of the conduction duty cycle of the power device is increased by 20%, that is, the adjusted limit value of the conduction duty cycle of the power device is 120% of the current limit value of the conduction duty cycle of the power device. As another example, when the instantaneous junction temperature is 160°C, the preset junction temperature is 120°C, and the first difference is 40°C, it means that the temperature of the power device needs to be lowered by more than 30°C, and the corresponding proportion to be adjusted is 25%, that is, at the current In the case of the limit value of the conduction duty cycle of the power device, a 25% cooling range is required based on the current instantaneous junction temperature. Therefore, the current conduction duty cycle is reduced by 25%, that is, the adjusted conduction duty cycle limit of the power device The value is 75% of the limit value of the conduction duty cycle of the current power device, so that the adjusted temperature is reduced to 120°C, and the instantaneous junction temperature does not exceed the preset junction temperature. The ratio to be adjusted is used to adjust the conduction duty ratio limit value of the power device corresponding to the current instantaneous junction temperature, so as to adjust the corresponding temperature range, and the effect of accurately and timely temperature adjustment can be achieved.

Referring to FIG. 3, FIG. 3 is a specific flowchart of step S203 in FIG. 2. In the example of FIG. 3, step S203 includes but is not limited to the following steps:

Step S301, in response to the conduction duty cycle limit value of the power device being less than the required conduction duty cycle of the power device in the next cycle, using the power device conduction duty cycle limit value to the conduction duty cycle of the control signal of the power device make adjustments;

Step S302, in response to the conduction duty cycle limit value of the power device is equal to the conduction duty cycle required by the power device in the next cycle, adopt the conduction duty cycle limit value of the power device or the conduction duty cycle required by the power device in the next cycle Adjusting the conduction duty cycle of the control signal of the power device;

Step S303, in response to the conduction duty cycle limit value of the power device being greater than the required conduction duty cycle of the power device in the next cycle, using the conduction duty cycle required by the power device in the next cycle to conduct the control signal of the power device The duty cycle is adjusted.

It can be understood that the limit value of the conduction duty cycle of the power device is characterized as an adjustment parameter for the maximum allowable duty cycle corresponding to the real-time temperature of the power device, that is, when the conduction duty cycle exceeds the limit value of the conduction duty cycle of the power device, Then the instantaneous junction temperature of the power device will exceed the first preset junction temperature. Since the limit value of the conduction duty cycle of the power device is determined according to the instantaneous junction temperature, and the instantaneous junction temperature is detected in real time, the limit value of the conduction duty cycle of the power device is updated in real time, and the power device can be adjusted in time to protect the power device. The turn-on duty cycle required by the power device in the next cycle is characterized by the turn-on duty cycle of the next cycle corresponding to the average temperature or target power of the power device within the target period, that is, when the next cycle power of the control signal in the next cycle The on-duty cycle required by the device and the control of the power device can make the power device reach the target power or the average junction temperature of the next target time can be stabilized within the range below the preset junction temperature.

The smaller the limit value of the conduction duty cycle of the power device, the shorter the maximum allowable conduction time, the less heat generated by the power device, and the overheated junction temperature can be quickly suppressed, so that the limit value of the conduction duty cycle of the power device The magnitude of the instantaneous junction temperature and the average junction temperature that needs to be adjusted can be judged by the conduction duty cycle required by the power device in the next cycle.

Take the smaller value of the conduction duty cycle limit value of the power device and the conduction duty cycle required by the power device in the next cycle to adjust the conduction duty cycle so that the instantaneous junction temperature and the average junction temperature cannot exceed the preset value. Set junction temperature. When the limit value of the conduction duty cycle of the power device is less than the required conduction duty cycle of the power device in the next cycle, it can be considered 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, the adjustment range required for the instantaneous junction temperature at the current moment is greater than the adjustment range required for the average junction temperature, therefore, the power device conduction duty cycle limit value is used to control the signal The conduction duty cycle of the device is adjusted, and the instantaneous junction temperature is given priority as the protection basis to quickly reduce or slowly increase the temperature of the power device, so that the instantaneous junction temperature can be quickly suppressed within the range below the preset junction temperature or the first preset junction temperature within, or avoid the instantaneous junction temperature being higher than the preset junction temperature or the first preset junction temperature during the process of increasing the operating power of the power device.

When the conduction duty cycle required by the power device in the next cycle is less than the limit value of the conduction duty cycle of the power device, it can be considered that for the instantaneous junction temperature and average junction temperature, the adjustment range required for the average junction temperature at the current moment is greater than the adjustment required for the instantaneous junction temperature , that is, 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 smaller than the difference between the average junction temperature and the second preset junction temperature, so the power device of the next cycle is used The required on-duty ratio is used to adjust the on-duty ratio of the control signal, and the average junction temperature is used as the protection basis to maintain the stability of the operating temperature of the power device. At the same time, the operating frequency of the power device is stabilized at the target power. The average junction temperature is quickly suppressed within the range below the preset junction temperature or the second preset junction temperature, and at the same time, the average junction temperature is prevented from being too high during the process of increasing the operating power of the power device.

When the conduction duty cycle required by the power device in the next cycle is equal to the limit value of the power device conduction duty cycle, it can be considered that the instantaneous temperature at the current moment is equal to the average temperature, or the difference between the instantaneous junction temperature and the first preset junction temperature is equal to the average The difference between the junction temperature and the second preset junction temperature, that is, the required adjustment range of the average junction temperature is equal to the required adjustment range of the instantaneous junction temperature. Therefore, the conduction duty cycle required by the power device in the next cycle can be used, or The limit value of the conduction duty ratio of the power device is used to adjust the conduction duty ratio of the control signal of the power device.

Referring to FIG. 4, FIG. 4 is a specific flowchart of step S201 in FIG. 2. In the example of FIG. 4, step S201 includes but is not limited to the following steps:

Step S401, in response to the difference between the instantaneous junction temperature and the preset junction temperature being greater than zero, gradually reducing the conduction duty cycle limit value of the power device through control adjustment;

Step S402, in response to the difference between the instantaneous junction temperature and the preset junction temperature being less than zero, gradually increasing the conduction duty ratio limit value of the power device through control and adjustment.

It can be understood that when the instantaneous junction temperature is greater than the preset junction temperature, that is, the difference between the instantaneous junction temperature and the preset junction temperature is greater than zero, the power device is in an overtemperature state, and the heat generation of the power device needs to be reduced. Therefore, By gradually reducing the limit value of the conduction duty cycle of the power device at the previous moment of the control signal, the limit value of the conduction duty cycle of the power device is updated, the pulse current is suppressed in time, and the maximum allowable conduction working time of the power device is gradually reduced , Gradually reduce the calorific value of the power device, can quickly reduce the temperature of the power device, and can avoid the unstable operation of the system caused by greatly reducing the conduction working time of the power device. Wherein, the conduction duty cycle limit value of the power device can also be obtained by gradually reducing the required conduction time of the power device in the previous cycle or the required conduction time of the power device in the next cycle.

Wherein, the proportions of gradually decreasing limit values of conduction duty cycle of power devices may be the same or different, for example, the proportions of gradually decreasing limit values of conduction duty cycles of power devices may all be 50%. The limit value of the conduction duty ratio of the power device in one cycle is 0.5, the limit value of the conduction duty cycle of the power device in the second cycle is 0.25, and the limit value of the conduction duty cycle of the power device in the third cycle is 0.125. As another example, the ratio of the gradually decreasing limit value of the conduction duty cycle of the power device can be different. The limit value of the conduction duty cycle of the power device in the first cycle is 0.5, and the limit value of the conduction duty cycle of the power device in the second cycle is 0.4, then the duty cycle limit value of the power device in the third cycle is 0.2. By gradually limiting the conduction duty cycle limit value of the power device at the previous moment of the control signal, the limit value of the power device conduction duty cycle is determined, and then the conduction duty cycle of the control signal is gradually limited, and the power can be gradually reduced. The temperature of the device, while maintaining the stable operation of the variable frequency controller, to avoid greatly reducing the on-time of the power device and affecting the normal operation of the system.

When the instantaneous junction temperature is lower than the preset junction temperature, it can be considered that the power device is in a normal working state, and the operating power of the system can be increased by increasing the maximum allowable on-time duration of the power device according to actual use requirements, and in order to avoid a large increase The maximum allowable conduction working time of the power device will cause the power device to heat up too fast and burn the power device. The power device conduction duty cycle limit value of the control signal is adjusted gradually to limit the power device conduction duty cycle. The value is increased to the preset limit value that meets the actual use requirements. It can detect the temperature rise and junction temperature of the power device after increasing the limit value of the conduction duty cycle of the power device in real time, so as to avoid the overheating of the power device and protect it in time. power component.

When the instantaneous junction temperature is equal to the preset junction temperature, the power device conduction duty cycle limit value of the current control signal can be maintained, and the power device conduction duty cycle limit value of the current control signal can also be reduced according to actual use requirements value, suppressing the instantaneous junction temperature below the preset junction temperature.

It should be noted that the adjustment process of gradually adjusting the limit value of the conduction duty cycle of the power device of the control signal can be continuously multiple times, that is, in the process of gradually reducing the limit value of the conduction duty cycle of the power device of the control signal , when 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 reducing the limit value of the power device conduction duty cycle of the control signal can still be maintained, so that The instantaneous junction temperature can be rapidly reduced, and the instantaneous junction temperature is suppressed below the preset junction temperature. In the process of gradually increasing the limit value of the power device conduction duty cycle of the control signal, when the real-time instantaneous junction temperature is higher than the preset junction temperature, the limit value of the power device conduction duty cycle of the control signal can be terminated. Gradually increase the adjustment operation, and timely reduce the power device conduction duty cycle limit value of the control signal, and then suppress the conduction duty cycle of the control signal in time.

Referring to FIG. 5, FIG. 5 is a specific flowchart of step S202 in FIG. 2. In the example of FIG. 5, step S202 includes but is not limited to the following steps:

Step S501, determine the conduction current limit value of the power device according to the difference between the average junction temperature and the preset junction temperature;

Step S502 , according to the conduction current limit value of the power device, the current required by the system in the next cycle, and the current actual conduction current of the power device, the required conduction duty ratio of the power device in the next cycle is obtained.

It can be understood that since the power device generates heat when the current flows, the greater the value of the current flowing, the more heat generated per unit time. Therefore, by controlling the current value flowing through the power device, the heat generated by the power device can be changed, thereby controlling the temperature of the power device. The working parameters include the average current, and the average current can be obtained by detecting the working current within the target duration in real time and taking the average value. Operating parameters also include the average voltage of the power device over the target time period. The current variation can be determined by the average junction temperature and the second preset junction temperature, and the current variation can be calculated according to the following formula:

ΔT=(U×ΔI)×R _th

Among them, 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 amount of current change; U represents the average voltage of the power device within the target duration, and R _th represents the power device at The thermal impedance over the target duration, where the thermal impedance is at a steady value. The amount of current change can be divided into current overload and current margin according to the relationship between the average junction temperature and the preset junction temperature. Set the junction temperature difference, average voltage and thermal impedance to calculate the current overload of the power device, and subtract the current overload from the average current to get the current limit value of the power device conduction current. The limit value of the power device conduction current can be Expressed as an approximate estimate of the maximum current allowed by the power device at the current moment. When the current value flowing through the power device is greater than the conduction current limit value of the power device, it is easy to cause the power device to be in an over-temperature and overload state, and damage the power device.

Wherein, the amount of current change can be calculated by calculating the difference between the average junction temperature and the preset junction temperature, that is, the second difference. Using the ratio between the second difference and the average junction temperature, the current adjustment ratio is determined, and the temperature range to be adjusted based on the current average junction temperature is determined. By calculating the product of the current adjustment ratio and the average current, the conduction current limit value of the power device is obtained. For example, if the average junction temperature is 100°C and the preset junction temperature is 120°C, then the second difference is -20°C, indicating that the range in which the average junction temperature can be increased by increasing the average current is 20°C. The corresponding current adjustment ratio is 20%. That is to say, when the current average current flows through the power device, the junction temperature of the power device is 100°C. Based on the current state, there is a 20% temperature rise. Therefore, the current average The current increases by 20%, that is, the adjusted average current is 120% of the current average current.

When the average junction temperature is less than the preset junction temperature, the current change value 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 Current margin, the current limit value of the power device conduction current of the power device can be obtained; when the average junction temperature is equal to the preset junction temperature, the limit value of the power device conduction current can be approximately equal to the average current.

After obtaining the current limit value of the power device conduction current of the power device, it needs to be adjusted based on the current required by the system in the next cycle and the conduction current of the current actual power device. The required current determines the current required by the power device in the next cycle, and then through the difference between the current required by the power device in the next cycle and the conduction current of the current actual power device, the current that flows through the power device at the current moment needs to be adjusted. The amount of change is the third difference. Therefore, according to the relationship between the value of the current flowing through the power device and the duty cycle parameter, the turn-on duty cycle required by the power device in the next period corresponding to the third difference can be determined.

Wherein, according to the ratio of the third difference to the current conduction current of the actual power device, the current amplitude that needs to be adjusted based on the current conduction current of the actual power device can be determined, that is, the current adjustment ratio. By obtaining the conduction duty cycle parameter at the current moment, the product of the current adjustment ratio and the conduction duty cycle parameter is calculated to obtain the conduction duty cycle required by the power device in the next cycle, so that the corresponding current amplitude can be adjusted, accurately Quickly adjust current.

It should be noted that, using the difference between the average junction temperature and the preset junction temperature, the limit value of the conduction current of the power device can be calculated by the PID control system, and the limit value of the conduction current of the power device can also be determined by the proportional integral controller. value, and then determine the conduction duty cycle required by the power device in the next cycle through the conduction current limit value of the power device.

Referring to FIG. 6, FIG. 6 is a specific flowchart before step S502 in FIG. 5. In the example in FIG. 6, steps before step S502 include but are not limited to the following steps:

Step S601, in response to the fact that the current limit value of the power device is greater than or equal to the current required by the system in the next cycle, the current required by the system in the next cycle is used as the current required by the power device in the next cycle, and then according to the current required by the power device in the next cycle The current conduction current of the actual power device is used to obtain the conduction duty cycle required by the power device in the next cycle;

Step S602, in response to the power device on-current limit value being less than the current required by the system in the next cycle, the power device on-current limit value is used as the current required by the power device in the next cycle, and then according to the current required by the power device in the next cycle and The conduction current of the current actual power device obtains the conduction duty cycle required by the power device in the next cycle.

It can be understood that the power device is installed in the variable frequency controller. According to the operating power required by the power device, the current value flowing through the power device within the target time corresponds to the current required by the system in the next cycle, and the current required by the system in the next cycle The current is set by the variable frequency controller according to the current work needs. According to the average junction temperature and preset junction temperature of the power device within the target time, the limit value of the conduction current of the power device is determined, and the current value flowing through the power device is suppressed below the limit value of the conduction current of the power device, which can average the power device The junction temperature is suppressed within the preset junction temperature range.

In the case that the limit value of the conduction current of the power device is greater than or equal to the current required by the system in the next cycle, it means that the current required by the system in the next cycle is safe for the power device at this time, and the current required by the power device in the next cycle of the power device can be controlled Adjust to the current required by the system in the next cycle, so that the power device operates according to the target power and will not be damaged due to overcurrent; when the limit value of the conduction current of the power device is less than the current required by the system in the next cycle, it means that if The current value flowing through the power device is the current required by the system in the next cycle, which will cause the power device to be in a current overload state or the heat generated is too high to cause an overheating state, so the current required by the power device in the next cycle should be controlled as The power device conduction current limit value, so that the average junction temperature of the power device is not higher than the preset junction temperature, and try to meet the working needs of the variable frequency controller, and reduce the current margin of the power device.

In addition, after determining the required current of the power device in the next cycle, the difference between the required current of the power device in the next cycle and the conduction current of the current actual power device can be used to determine the required turn-on current of the power device in the next cycle. The specific method of obtaining the turn-on duty cycle required by the power device in the next cycle has been explained in detail in the above-mentioned embodiment, and will not be repeated here in this embodiment.

Referring to FIG. 7, FIG. 7 is a specific flowchart of step S102 in FIG. 1. In the example of FIG. 7, step S102 includes but is not limited to the following steps:

Step S701, according to the product of the instantaneous power loss and the instantaneous thermal impedance, the instantaneous temperature increment of the power device is obtained;

Step S702, according to the sum of the instantaneous temperature increment and the instantaneous case temperature, the instantaneous junction temperature of the power device is obtained.

It can be understood that since the actual operating temperature of the power device semiconductor is higher than the housing temperature of the power device, by calculating the temperature difference between the semiconductor and the housing, the actual operating temperature of the semiconductor is calculated using the temperature difference and the instantaneous housing temperature , the instantaneous junction temperature. The temperature difference between the semiconductor and the housing can be calculated from the power device heating power and thermal resistance. The power loss of the power device is the heating power. Therefore, the product of the instantaneous power loss of the power device and the instantaneous thermal impedance can be used to determine the temperature difference between the semiconductor and the housing at the current moment, that is, the instantaneous temperature increase of the power device. In this way, the instantaneous temperature increment of the power device and the instantaneous case temperature are calculated together, and the instantaneous junction temperature of the power device can be accurately determined, so as to accurately protect the power device in time and stabilize the normal operation of the system.

It should be noted that the operating parameters include the conduction current of the current actual power device and the conduction voltage of the current actual power device of the power device, the conduction current of the current actual power device flowing through the current power device, and the current actual power device loaded on the power The conduction voltage of the current actual power device on the device is multiplied, and the instantaneous power loss of the power device under the current pulse can be obtained, so that the real-time power loss of the power device can be determined, and the instantaneous junction temperature of the power device can be calculated more accurately. , to improve the accuracy of protection control.

It should be noted that the instantaneous power loss can also be calculated from at least two parameters in the operating current, operating voltage and resistance value of the power device. For example, the instantaneous power loss can be calculated according to the square value of the operating current and the resistance value of the power device It can also be obtained from the product between the working voltage and the resistance value of the power device. In addition, the instantaneous power loss can also be calculated according to other factors such as the ambient temperature and the operating conditions of the power device, or it can be a fixed parameter value set externally.

Referring to FIG. 8, FIG. 8 is a specific flowchart of step S102 in FIG. 1. In the example of FIG. 8, step S102 includes but is not limited to the following steps:

Step S801, according to the product of the average power loss and the steady-state thermal impedance, the average temperature increment of the power device is obtained;

In step S802, the average junction temperature of the power device is obtained according to the sum of the average temperature increment and the average case temperature.

It can be understood that since the actual operating temperature of the semiconductor of the power device is higher than the casing temperature of the power device, by calculating the temperature difference between the semiconductor and the casing within the target time period, the temperature difference and the average casing temperature are used to calculate the temperature of the semiconductor. The actual operating temperature, that is, the average junction temperature. The average temperature increment is determined according to the average power loss and the steady-state thermal impedance of the power device, where the average temperature increment is the difference between the average junction temperature and the average case temperature of the power device within the target time period, that is, ΔT _jc = P×R _th =T _j -T _c , where ΔT _jc represents the average temperature increment of the power device within the target duration, P represents the average power loss of the power device within the target duration, R _th represents the thermal impedance of the power device, and T _j represents the power The average junction temperature of the device within the target time period, _Tc is expressed as the average case temperature of the power device within the target time period. Therefore, the average junction temperature of the power device can be accurately determined, so as to accurately protect the power device in time and stabilize the normal operation of the system.

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 based on other factors such as ambient temperature and operating conditions of power devices. The working parameters include the average current and average voltage of the power device within the target time period. By multiplying the average current flowing through the current power device and the average voltage loaded on the power device, the average value of the power device within the target time period can be obtained. Power loss, so that the heating power of the power device within the target time can be determined, the average junction temperature of the power device can be calculated more accurately, and the accuracy of protection control can be improved.

Referring to FIG. 9 , FIG. 9 shows a schematic diagram of a preset thermal impedance-duration ratio relationship. Among them, the abscissa data in the schematic diagram is the transient conduction time, and the ordinate data is the thermal impedance. It can be seen from Fig. 9 that the instantaneous thermal impedance increases with the increase of the transient conduction time, which can be passed through the transient The conduction time corresponds to determine the instantaneous thermal impedance, which tends to be stable after a certain period of time.

It can be understood that the target duration is the time for the instantaneous thermal impedance of the power device to reach a stable value from the initial value in the preset thermal impedance-duration proportional relationship, and the thermal impedance-duration proportional relationship is an inherent physical property of the power device. Wherein, the initial value may refer to the thermal impedance of the power device during non-conduction working time, and may also 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 the thermal resistance is less than one-thousandth in the following 1 ms, or it can refer to the time when the instantaneous thermal resistance reaches 99% of the steady-state thermal resistance value. The embodiment does not specifically limit the target time length, as long as it can represent the time when the instantaneous thermal resistance of the power device tends to a stable value. The junction-to-case thermal impedance of the power device can tend to be stable within the target time period, so that the average junction temperature of the power device can be calculated through the steady-state thermal impedance, which can make the calculation result more accurate and the error smaller.

It should be noted that the target duration can be equal to the time when the instantaneous thermal impedance of the power device tends to stabilize, or it can be longer than the time when the instantaneous thermal impedance of the power device tends to stabilize, as long as it can reduce the calculation error of the average junction temperature. Within the protection scope of this embodiment.

It can be understood that the control signal of the power device includes a preset pulse period and a corresponding conduction duty cycle, and the duty cycle refers to the ratio of the conduction time to the total cycle time within a pulse cycle period. ratio, which is equivalent to the pulse width. Therefore, the conduction time of the power device in a pulse cycle period, that is, the transient conduction time of the power device, can be determined through the conduction duty cycle and the pulse period. Power devices usually start to generate heat from the time of power-on, and the thermal resistance begins to rise, and tends to be stable after a certain period of time. The thermal impedance corresponding to different transient conduction times may be different, so you can use the preset thermal impedance - The proportional relationship of the time length determines the instantaneous thermal impedance corresponding to the current transient conduction time. At the same time, the corresponding steady-state thermal impedance can be determined through the target duration.

It should be noted that the time for the instantaneous thermal impedance of a power device to stabilize is usually short, and the transient on-time is shorter than the target duration, so the duty cycle of the control signal is adjusted by the average junction temperature and instantaneous junction temperature. Adjustment, the response time is short, and the working state of the power device can be adjusted in time when the power device is over-current and over-temperature, so as to avoid the damage of the power device due to over-current and over-temperature to a certain extent, and improve the stability of the system.

为功率器件的第一预设结温，ΔT_{jc_pluse}为功率器件的瞬时温度增量，D_th为功率器件的功率器件导通占空比限制值，D_set为功率器件的下一周期功率器件所需导通占空比；P_{Loss_ave}为功率器件的平均损耗功率，Z_{thjc_ave}为功率器件的稳态热阻抗，T_{j_ave}为功率器件的平均结温，T_{c_ave}为功率器件的平均壳体温度，

为功率器件的第二预设结温，ΔT_{jc_ave}为功率器件的平均温度增量，i_th为功率器件的待调整电流量，i_set为功率器件的下一周期系统所需电流。Referring to FIG. 10 , FIG. 10 is a schematic flowchart of a protection control method for a power device of the present invention. Among them, v _ce is the conduction voltage of the current actual power device of the power device, _ic is the conduction current of the current actual power device of the power device, P _{Loss_pulse} is the instantaneous power loss of the power device, Z _{thjc_pulse} is the instantaneous heat dissipation of the power device Impedance, T _{j_pulse} is the instantaneous junction temperature of the power device, T _c is the instantaneous case temperature of the power device,

is the first preset junction temperature of the power device, ΔT _{jc_pluse} is the instantaneous temperature increment of the power device, D _th is the limit value of the power device conduction duty cycle of the power device, and D _set is the power device setting of the next cycle of the power device The conduction duty cycle is required; P _{Loss_ave} is the average power loss of the power device, Z _{thjc_ave} is the steady-state thermal impedance of the power device, T _{j_ave} is the average junction temperature of the power device, T _{c_ave} is the average case temperature of the power device,

is the second preset junction temperature of the power device, ΔT _{jc_ave} is the average temperature increment of the power device, i _th is the current to be adjusted of the power device, and i _set is the current required by the system for the next cycle of the power device.

Real-time detection of the conduction current of the current actual power device, the conduction voltage of the current actual power device, and the instantaneous case temperature of the power device, and the loss is performed using the conduction voltage of the current actual power device and the conduction current of the current actual power device Calculate the power to get the instantaneous power loss. The average power loss within the target time period is determined through the instantaneous power loss and the target time period. The instantaneous temperature increment of the power device can be calculated by combining the product of the instantaneous power loss and the instantaneous thermal impedance, and then the instantaneous junction temperature of the power device can be determined by using the sum of the instantaneous case temperature and the instantaneous temperature increment. Correspondingly, the product of the integrated average power loss and the steady-state thermal impedance can be used to calculate the average temperature increase of the power device, and then use the sum of the average case temperature and the average temperature increase to determine the average junction temperature of the power device. By comparing the difference between the first preset junction temperature and the instantaneous junction temperature, the limit value of the conduction duty cycle of the power device is determined. By comparing the second preset junction temperature with the average junction temperature, the limit value of the conduction current of the power device is determined. After obtaining the limit value of the conduction current of the power device, compare the limit value of the conduction current of the power device with the current required by the system in the next cycle, and judge whether the current required by the system in the next cycle is too high, and if it is too high, select the power device The conduction current limit value is used as the current required by the power device in the next cycle, and then the current required by the power device in the next cycle is compared with the conduction current of the current actual power device to determine the actual required change in the current, thus obtaining the following One-cycle power device required conduction duty cycle. The conduction duty cycle required by the power device in the next cycle is compared with the limit value of the conduction duty cycle of the power device, and the smaller value of the two is taken as the conduction duty cycle of the control signal. The conduction duty cycle of the control signal is adjusted by using the conduction duty cycle required by the power device in the next cycle and the limit value of the power device conduction duty cycle, and the conduction duty cycle required by the power device in the next cycle does not exceed the power In the case of the limit value of the device conduction duty cycle, the power device operates at the required conduction duty cycle of the power device in the next cycle, and the required conduction duty cycle of the power device exceeds the limit value of the power device conduction duty cycle in the next cycle In the case of the value, the power device operates at the limit value of the conduction duty cycle of the power device, so as to realize the control of the power device by taking into account the average junction temperature and the instantaneous junction temperature. Therefore, the instantaneous junction temperature and average junction temperature of the power device are determined through the case temperature, power loss, and thermal impedance. Taking the instantaneous junction temperature and average junction temperature as the control target, combined with the difference between the instantaneous junction temperature and average junction temperature and their respective corresponding junction temperature thresholds, the control signal of the power device is comprehensively adjusted to improve the response to the protection of the power device The speed and the stability of power devices can quickly and stably suppress the operating temperature of power devices within the normal operating range, avoiding excessive operating temperature of power devices caused by untimely protection or system shutdown caused by excessive protection, and can quickly and promptly protect power devices , improve the stability of power devices.

Referring to FIG. 11 , FIG. 11 is a schematic structural diagram of an operation control device 1100 provided by an embodiment of the second aspect of the present invention, wherein the operation control device 1100 includes: a memory 1110 , a processor 1120 and stored in the memory 1110 and can The computer program running on the processor 1120, when the processor 1120 executes the computer program, realizes the protection and control method of the power device as in the above-mentioned embodiments.

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 protection and control methods for power devices in the above embodiments of the present invention. The processor 1120 executes the non-transitory software programs and instructions stored in the memory 1110 to implement the protection and control method for the power device in the above-mentioned embodiments of the present invention.

The memory 1110 may include a program storage area and a data storage area, wherein the program storage area may store an operating system and an application program required by at least one function; data etc. In addition, the memory 1110 may include a high-speed random access memory 1110, and may also include a non-transitory memory 1110, such as at least one magnetic disk storage device, flash memory device, or other non-transitory solid-state storage devices. It should be noted that the storage 1110 may optionally include storages 1110 that are set remotely relative to the processor 1120, and these remote storages 1110 may be connected to the terminal through a network. Examples of the aforementioned networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

The non-transitory software programs and instructions required to realize the protection and control method of the power device in the above embodiment are stored in the memory, and when executed by one or more processors, the protection and control method of the power device in the above embodiment is executed , for example, execute method steps S101 to step S103 in Fig. 1 described above, method steps S201 to step S203 in Fig. 2 , method steps S301 to step S303 in Fig. 3 , method steps S401 to step S402 in Fig. 4 , the method steps S501 to S502 in FIG. 5 , the method steps S601 to S602 in FIG. 6 , the method steps S701 to S702 in FIG. 7 , and the method steps S801 to S802 in FIG. 8 .

The embodiment of the third aspect of the present invention provides a frequency conversion controller, and the frequency conversion controller includes the operation control device 1100 as provided in the embodiment of the second aspect. By detecting the working parameters of the power device, and calculating the instantaneous junction temperature of the power device at the current moment, and the average junction temperature within the target time period. By comparing the difference between the instantaneous junction temperature and the preset junction temperature, it is possible to judge the instantaneous working state of the power device at the current moment, and by comparing the difference between the average junction temperature and the preset junction temperature, it is possible to judge the average operation of the power device within the target time period state. The average working state can be characterized as the synthesis of multiple instantaneous working states within the target time period. Both the instantaneous working state and the average working state can reflect whether the temperature of the power device is adjusted, and the size of the difference can determine the adjustment required for the control signal Amplitude, so that the instantaneous junction temperature and average junction temperature of power devices can be quickly adjusted below the preset junction temperature range. Compared with the technical solution in the related art that only relies on the current value flowing through to control the power device, the present invention uses the difference between the instantaneous junction temperature of the power device and/or the difference between the average junction temperature and the preset junction temperature to control the power device The signal is adjusted to improve the response speed of the protection of the power device and the stability of the power device, taking into account the instantaneous junction temperature and the average junction temperature of the power device, and quickly and stably suppress the operating temperature of the power device within the preset junction temperature range , to avoid the overheating of power devices caused by untimely protection or system shutdown caused by overprotection.

It should be noted that the protection and control method of power devices can be applied to frequency conversion controllers, and can also be applied to products using power devices as switching tubes, such as air conditioners, washing machines, refrigerators and elevators.

The embodiment of the fourth aspect of the present invention provides a computer-readable storage medium, the computer-readable storage medium stores computer-executable instructions, and the computer-executable instructions can be used to make the computer perform the protection of the power device in the embodiment of the first aspect above. The control method, for example, executes the method steps S101 to S103 in FIG. 1 described above, the method steps S201 to S203 in FIG. 2 , the method steps S301 to S303 in FIG. 3 , and the method steps S401 to S401 in FIG. 4 Step S402, method steps S501 to S502 in FIG. 5 , method steps S601 to S602 in FIG. 6 , method steps S701 to S702 in FIG. 7 , and method steps S801 to S802 in FIG. 8 .

Those skilled in the art can understand that all or some of the steps and systems in the methods disclosed above can be implemented as software, firmware, hardware and an appropriate combination thereof. Some or all of the physical components may 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 may be distributed on computer readable media, which may include computer storage media or non-transitory media and communication media or transitory media. As is well known to those of ordinary skill in the art, the term computer storage media includes both volatile and nonvolatile, Removable and non-removable media. Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disk DVD or other optical disk storage, magnetic cartridges, tape, magnetic disk storage or other magnetic storage devices, or can be used in Any other medium that stores desired information and that can be accessed by a computer. In addition, as is well known to those of ordinary skill in the art, communication media typically embodies computer readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transport mechanism, and may include any information delivery media .

The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made without departing from the gist of the present invention within the scope of knowledge of those skilled in the art .

Claims (13)

1. A protection control method of a power device is characterized by comprising the following steps:

acquiring working parameters of the power device;

determining the instantaneous junction temperature of the power device and the average junction temperature within a target time length according to the working parameters;

and acquiring a difference value between the instantaneous junction temperature and/or the average junction temperature and a preset junction temperature, and adjusting a control signal of the power device according to the difference value so as to enable the instantaneous junction temperature and the average junction temperature not to be higher than the preset junction temperature.

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

3. The protection control method according to claim 1, wherein the obtaining 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 according to the difference comprises:

determining a power device conduction duty ratio limit value according to the difference value of the instantaneous junction temperature and the preset junction temperature;

determining the required conduction duty ratio of the power device in the next period according to the difference value of the average junction temperature and the preset junction temperature;

and adjusting the conduction duty ratio of the control signal of the power device according to the conduction duty ratio limit value of the power device and the conduction duty ratio required by the power device in the next period.

4. The protection control method according to claim 3, wherein the adjusting the on duty cycle of the control signal of the power device according to the power device on duty cycle limit value and the on duty cycle required by the power device in the next period comprises:

in response to that the power device conduction duty ratio limit value is smaller than the conduction duty ratio required by the power device in the next period, adjusting the conduction duty ratio of a control signal of the power device by adopting the power device conduction duty ratio limit value;

in response to that the power device on duty ratio limit value is equal to the on duty ratio required by the power device in the next period, adjusting the on duty ratio of the control signal of the power device by adopting the power device on duty ratio limit value or the on duty ratio required by the power device in the next period;

and in response to the fact that the power device conduction duty ratio limiting value is larger than the conduction duty ratio required by the power device in the next period, adopting the conduction duty ratio required by the power device in the next period to adjust the conduction duty ratio of the control signal of the power device.

5. The protection control method according to claim 3, wherein the determining a power device turn-on duty cycle limit value according to the difference between the instantaneous junction temperature and the preset junction temperature includes:

in response to the difference value between the instantaneous junction temperature and the preset junction temperature being larger than zero, gradually reducing the conduction duty ratio limit value of the power device through control and adjustment;

or,

and responding to the difference value between the instantaneous junction temperature and the preset junction temperature being less than zero, and gradually increasing the power device conduction duty ratio limit value through control and adjustment.

6. The protection control method according to claim 3, wherein the determining a required on-duty ratio of the power device in the next period according to the difference between the average junction temperature and the preset junction temperature includes:

determining a power device conduction current limit value according to the difference value of the average junction temperature and the preset junction temperature;

and obtaining the required conduction duty ratio of the power device in the next period according to the conduction current limit value of the power device, the current required by the system in the next period and the current conduction current of the actual power device.

7. The protection control method according to claim 6, wherein the obtaining the on-duty ratio required by the power device in the next period according to the on-current limit value of the power device, the current required by the system in the next period, and the on-current of the current actual power device comprises:

in response to the fact that the limiting value of the conduction current of the power device is larger than or equal to the current required by the system in the next period, the current required by the system in the next period is used as the current required by the power device in the next period, and then the conduction duty ratio required by the power device in the next period is obtained according to the current required by the power device in the next period and the conduction current of the current actual power device;

and in response to the fact that the conduction current limit value of the power device is smaller than the current required by the system in the next period, taking the conduction current limit value of the power device as the current required by the power device in the next period, and obtaining the conduction duty ratio required by the power device in the next period according to the current required by the power device in the next period and the current conduction current of the actual power device.

8. The protection control method according to claim 1, wherein the operating parameters include an instantaneous case temperature, an instantaneous thermal impedance, and an instantaneous loss power of the power device at a present time;

the determining the instantaneous junction temperature of the power device according to the operating parameter comprises:

obtaining the instantaneous temperature increment of the power device according to the product of the instantaneous loss power and the instantaneous thermal impedance;

and obtaining the instantaneous junction temperature of the power device according to the sum of the instantaneous temperature increment and the instantaneous shell temperature.

9. The protection control method of claim 1, wherein the operating parameters further include an average case temperature, a steady-state thermal impedance, and an average power loss of the power device over the target time period;

the determining an average junction temperature over a target time period according to the operating parameter includes:

obtaining the average temperature increment of the power device according to the product of the average power loss and the steady-state thermal impedance;

and obtaining the average junction temperature of the power device according to the sum of the average temperature increment and the average shell temperature.

10. The protection control method according to any one of claims 1 to 9, wherein the target time period is a time period during which the instantaneous thermal impedance of the power device tends from an initial value to a stable value in a preset thermal impedance-time period proportional relationship.

11. An operation control apparatus comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, the processor implementing the protection control method of the power device according to any one of claims 1 to 10 when executing the computer program.

12. A variable frequency controller comprising the operation control device according to claim 11.

13. A computer-readable storage medium storing computer-executable instructions for causing a computer to execute the protection control method for a power device according to any one of claims 1 to 10.

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