Temperature estimation method of direct current bus capacitor, storage medium and driving control circuit board

Abstract

The invention relates to a temperature estimation method for a direct current bus capacitor, which comprises the following steps: acquiring at least one working parameter of a motor, and inputting the acquired at least one working parameter into a pre-calibrated lookup table to determine the power loss Ploss of the direct current bus capacitor; measuring at least one reference temperature around the DC bus capacitor; obtaining the current rotating speed of the motor, and determining a thermal network model of the DC bus capacitor based on the current rotating speed of the motor; and estimating the temperature condition of the DC bus capacitor based on the thermal network model according to the determined power loss Ploss of the DC bus capacitor and the at least one reference temperature. The invention also relates to a computer readable storage medium and a driving control circuit board comprising the computer readable storage medium.

Description

Technical Field

[0001] The present application relates to the field of motor control, and more specifically, to a temperature estimation method for a DC bus capacitor, a computer-readable storage medium, and a drive control circuit board including the computer-readable storage medium. Background Art

[0002] DC link capacitors are widely used electronic components in power electronic systems, usually for storing electrical energy and smoothing DC voltage. They are designed to store charge and release it when needed to meet the transient power requirements of electronic equipment.

[0003] For example, in electric vehicles, DC bus capacitors play an important role. Their main function is to provide stable DC voltage in, for example, the motor drive control circuit, reduce voltage fluctuations and noise in the DC bus, and ensure the normal operation of load devices (such as motors). The motor drive control circuit of electric vehicles needs to manage and control the flow of high-power electrical energy in order to transfer electrical energy from the battery to the motor to drive the vehicle. In this process, the DC bus capacitor is used to smooth and stabilize the DC voltage provided by the battery to ensure the normal operation of the motor and the motor drive control system.

[0004] Generally, as the operating temperature of the DC bus capacitor increases, the performance of the dielectric (usually an electrolyte or polymer film) inside the capacitor decreases, which leads to a decrease in the capacitor's capacitance and makes it unable to provide sufficient current stability for the motor, which ultimately affects the motor's operating efficiency and performance. In addition, excessively high operating temperatures accelerate the loss and damage of the electrolyte inside the capacitor, which may cause capacitor failure and shorten the service life of the capacitor, thereby affecting the reliability and maintenance cost of the entire motor drive control system. Therefore, monitoring the temperature of the DC bus capacitor is essential to maintaining the performance and life of the motor drive control system.

[0005] Conventional temperature monitoring methods for DC bus capacitors can only use external temperature sensors to obtain the external shell temperature of the capacitor, but cannot accurately obtain the internal temperature of the capacitor. Summary of the invention

[0006] In order to accurately monitor the temperature of the DC bus capacitor, the present application proposes a temperature estimation method for the DC bus capacitor. The method can reliably estimate the hotspot temperature inside the DC-Link capacitor based on the characteristics of the motor (for example, an air-cooled BSG motor) using a software model, thereby solving the problem that traditional methods cannot accurately estimate the internal temperature of the DC-Link capacitor.

[0007] According to a first aspect of the present application, a method for estimating the temperature of a DC bus capacitor is provided. The DC bus capacitor is provided on a drive control circuit board of a motor. The drive control circuit board further includes a power stage circuit and a heat dissipation device provided near the power stage circuit. The power stage circuit is used to convert a DC signal provided by an external power supply into an AC signal for driving the motor. The DC bus capacitor is connected across a positive DC bus and a negative DC bus connected to the external power supply. The method includes the following steps:

[0008] Obtain at least one operating parameter of the motor, and input the obtained at least one operating parameter into a pre-calibrated lookup table to determine the power loss P of the DC bus capacitor. loss ;

[0009] measuring at least one reference temperature around the DC bus capacitor;

[0010] Acquiring a current rotation speed of the motor, and determining a thermal network model of the DC bus capacitor based on the current rotation speed of the motor; and

[0011] Based on the thermal network model, the power loss P of the DC bus capacitor is determined. loss and the at least one reference temperature to estimate the temperature condition of the DC bus capacitor.

[0012] Advantageously, the at least one reference temperature comprises the surface temperature T pcb , the surface temperature T of the heat sink cooler and the ambient air temperature T of the DC bus capacitor ambient .

[0013] Advantageously, the thermal network model includes a first thermal resistance and a first thermal capacitance between the DC bus capacitor and the surrounding environment, a second thermal resistance and a second thermal capacitance between the DC bus capacitor and the heat sink, and a third thermal resistance and a third thermal capacitance between the DC bus capacitor and the drive control circuit board.

[0014] Advantageously, the temperature condition of the DC bus capacitor includes an internal temperature T N , Shell temperature T ref And the internal temperature T N With the shell temperature T ref The temperature difference T Δ .

[0015] Advantageously, the method further comprises:

[0016] Based on the first to third thermal resistances, the surface temperature T of the driving control circuit board pcb , the surface temperature T of the heat sink coolerand the ambient air temperature T of the DC bus capacitor ambient To calculate the shell temperature T of the DC bus capacitor ref .

[0017] Advantageously, the method further comprises:

[0018] The power loss P based on the first to third thermal resistances, the first to third thermal capacitances and the DC bus capacitor loss To calculate the internal temperature T of the DC bus capacitor N .

[0019] Advantageously, the method further comprises performing a derating operation on the motor when any one of the following conditions is met:

[0020] The internal temperature T N is above a first threshold; and

[0021] The internal temperature T N With the shell temperature T ref The temperature difference T Δ is higher than the second threshold.

[0022] Advantageously, the at least one operating parameter comprises at least one of a phase current, a phase angle, a modulation factor and a switching frequency of the motor.

[0023] According to a second aspect of the present application, a computer-readable storage medium is further provided, on which a computer program is stored. The computer program includes program instructions. Advantageously, when the program instructions are executed by a processor, the various steps of the temperature estimation method described above are implemented.

[0024] According to a third aspect of the present application, a drive control circuit board for a motor is also provided. Advantageously, the drive control circuit board includes:

[0025] A power stage circuit, the power stage circuit is used to convert a DC signal provided by an external power source into an AC signal for driving the motor;

[0026] a heat sink, the heat sink being arranged near the power stage circuit;

[0027] A DC bus capacitor connected between a positive DC bus and a negative DC bus connected to the external power source; and

[0028] A control unit, the control unit is configured to control the operating state of each switch tube in the power stage circuit, wherein the control unit includes:

[0029] A computer readable storage medium as described above; and

[0030] A processor is configured to execute program instructions stored in the computer-readable storage medium to estimate a temperature condition of the DC bus capacitor.

[0031] According to the temperature estimation method of the DC bus capacitor of the present application, not only the shell temperature of the capacitor can be estimated, but also its Hotspot temperature can be estimated, so that the motor can be timely derated by combining the estimated results of the shell temperature, Hotspot temperature and the internal and external temperature difference. The temperature estimation method can realize the accurate estimation of the Hotspot temperature by using the existing external temperature sensors (Cooler temperature, PCB temperature and air temperature) without increasing the BOM cost. In addition, the method uses the motor speed as the key determining factor affecting the thermal resistance and thermal capacity in the thermal network model of the capacitor, and can accurately detect the hotspot temperature of the capacitor within the full speed range of the motor, so as to take protective measures in time, such as adjusting the motor current or improving the heat dissipation function of the radiator, so as to ensure that the capacitor works within a safe temperature range, which helps to extend the service life of the bus capacitor and ensure the reliable operation of the motor, reducing the maintenance cost of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] By incorporating the accompanying drawings and Figure 1 With reference to the specific embodiments used to illustrate certain principles of the present invention, other features and advantages of the method of the present invention will become clear or be described in more detail.

[0033] Figure 1 The figure shows the structure of a conventional motor drive control circuit board.

[0034] Figure 2 A flow chart of a method for estimating the temperature of a DC bus capacitor according to an exemplary embodiment of the present application is shown.

[0035] Figure 3 shows the power loss P of the DC bus capacitor according to an exemplary embodiment of the present application. loss Schematic diagram of the determination process.

[0036] Figure 4 A schematic diagram of a thermal network model of a DC bus capacitor according to an exemplary embodiment of the present invention is shown. DETAILED DESCRIPTION

[0037] The temperature estimation method of the DC bus capacitor according to the present application will be described below with reference to the accompanying drawings and by way of example. In the following description, many specific details are set forth so that a person skilled in the art can more fully understand the present application. However, it is obvious to a person skilled in the art that the present application may be implemented without some of these specific details. Instead, it may be considered to implement the present application with any combination of the following features and elements, regardless of whether they relate to different embodiments. Therefore, the following aspects, features, embodiments and advantages are for illustrative purposes only and should not be regarded as elements or limitations of the claims.

[0038] Figure 1 FIG. 1 shows a structural diagram of a conventional motor drive control circuit board. Figure 1 As shown in the figure, the DC bus bars T40 and T41 are respectively connected to the positive and negative poles of an external DC power supply (which may be, for example, a power battery). The power from the external DC power supply is further transmitted to the DC bus capacitor (also called "DC-Link capacitor") arranged on the drive control circuit board after passing through the EMC filter to remove electromagnetic interference and filtering. The DC bus capacitor is connected across the positive DC bus bar T40 and the negative DC bus bar T41.

[0039] During the operation of the motor, the DC bus capacitor can be used to smooth and stabilize the DC voltage provided by the battery, reduce the fluctuation and noise of the voltage transmitted in the DC bus, and ensure the normal operation of the motor and its drive control system. The power processed by the DC-Link capacitor is further transmitted to the power stage circuit (i.e., inverter), where the DC signal after filtering and smoothing is converted into an AC signal for driving the motor. The on and off of each switch tube in the power stage circuit can be controlled by the controller ECU.

[0040] In addition, in order to prevent the operating temperature of each electronic component in the circuit board from being too high, a heat dissipation device ( Figure 1 The heat sink is usually arranged close to the heating element on the circuit board (for example, arranged near the power stage circuit) so as to effectively dissipate the heat generated by the heating element to the surrounding environment, thereby preventing the circuit board from overheating and maintaining the normal operation of various electronic components on the circuit board.

[0041] When the operating temperature of the circuit board (especially the DC bus capacitor therein) is too high, the heat sink cannot meet the heat dissipation requirements of the circuit board. At this time, it is necessary to implement a torque limiting / derating control strategy for the motor to protect the components in the circuit from high temperature damage.

[0042] In the conventional capacitor temperature monitoring method, the approximate capacitor shell temperature is obtained by mounting a temperature sensor near the DC-Link capacitor, and the output power of the inverter is adjusted directly through the temperature sensor information to protect the capacitor from high temperature damage. However, this monitoring method cannot accurately obtain the Hotspot temperature of the capacitor. Only the shell temperature outside the capacitor can be obtained using an external temperature sensor. Compared with the Hotspot temperature, the shell temperature response is slow and lagging. Under instantaneous large current pulses, the shell temperature cannot respond to current changes in time, which in turn causes the control circuit board to be unable to execute the corresponding capacitor protection strategy in time. Since the temperature difference between the inside and outside of the capacitor cannot be calculated, when the system has a large ripple current that will affect the life of the capacitor, the capacitor cannot be protected in time. In addition, in order to achieve the purpose of protecting the capacitor, a large temperature margin needs to be reserved, resulting in the inability to exert the peak current performance of the controller.

[0043] In view of the above-mentioned defects in the conventional temperature monitoring method of the DC bus capacitor, the present application proposes a new temperature estimation method for the DC bus capacitor, which can use the software model to reliably estimate the hotspot temperature inside the DC-Link capacitor based on the characteristics of the motor (for example, an air-cooled BSG motor), thereby solving the problem of inaccurate internal temperature estimation of the traditional DC-Link capacitor. When the motor controller outputs transient power, the calculation response speed of the software model is much faster than that of the external temperature sensor. Therefore, the subsequent overheating protection measures can be quickly started according to the capacitor temperature estimated by the software, and the protection of the capacitor is more timely. In addition, the method can also calculate the internal and external temperature difference of the DC-Link capacitor in order to identify the working conditions that may affect the life of the capacitor (for example, the ripple current exceeds the capacitor's tolerance range), thereby achieving maximum protection for the capacitor.

[0044] Specifically, according to the temperature estimation method of the present application, the power loss of the capacitor is first determined by pre-calibrating the working parameters of the motor (phase current, phase deviation angle, etc.), and then the thermal network model of the DC-Link capacitor is determined based on the power loss and the motor speed. The thermal network model has corresponding thermal capacitance and thermal resistance parameters. Finally, the temperature condition of the DC-Link capacitor can be calculated based on these parameters.

[0045] Here, the temperature condition of the DC bus capacitor involves two important temperature parameters: "hotspot temperature (also called hot spot temperature or internal temperature)" and "shell temperature". Among them, "hotspot temperature" refers to the actual temperature of the point or area with the highest temperature inside the capacitor. In a DC-Link capacitor, when current flows through the capacitor, energy loss occurs, which causes heat inside the capacitor. Inside the capacitor, there may be some hot spots, that is, places with higher temperatures than other parts. These hot spot temperatures may be much higher than the shell temperature of the capacitor. Therefore, "hotspot temperature" is the most direct and effective means to evaluate the temperature performance of the capacitor when it is subjected to transient current. When the hotspot temperature is too high, it means that the capacitor is overheated, and the motor needs to be derated to avoid damage to the capacitor components and performance degradation.

[0046] "Case temperature" refers to the temperature outside the DC-Link capacitor, which usually refers to the surface temperature of the capacitor's outer shell or external package. The case temperature is usually transmitted to the outside by the hot spot area inside the capacitor, and can also be affected by the external ambient temperature. The case temperature is very important for the operating environment of the capacitor because it can affect other components and equipment around the capacitor. When the case temperature is too high, it may have a thermal impact on the equipment around the capacitor and even cause safety problems. Therefore, in practical applications, it is also necessary to try to ensure that the case temperature of the capacitor is within an acceptable range.

[0047] According to the temperature estimation method of the present application, both the shell temperature of the DC-Link capacitor and its hotspot temperature can be estimated, so that the motor can be derated in a timely manner by combining the estimation results of the two.

[0048] Figure 2 FIG. 1 is a flow chart showing a method for estimating the temperature of a DC bus capacitor according to an exemplary embodiment of the present application. Figure 1 This article introduces the location of the DC bus capacitor in the motor drive control circuit board. Figure 2 To introduce the various operation steps of the temperature estimation method in detail.

[0049] First, obtain at least one working parameter of the motor, including the phase current, phase deviation angle, modulation coefficient, and switching frequency of the motor, and input the obtained at least one working parameter into a pre-calibrated lookup table to determine the power loss P of the DC bus capacitor. loss The "lookup table" here can be predetermined by calibrating the motor's operating parameters such as phase current, phase deviation angle, modulation factor, and switching frequency through experiments, and its function is to determine the capacitance current value and equivalent capacitance resistance of the motor under different working conditions.

[0050] The power loss P of the DC bus capacitor is determined using a pre-calibrated lookup table based on the motor's operating parameters. loss The detailed process is in Figure 3 Specifically, the corresponding current coefficient can be determined based on the phase deviation angle and modulation coefficient of the motor, and the effective value of the current of the DC-Link capacitor I can be obtained by multiplying the current coefficient with the effective value of the motor phase current actually measured. At the same time, the corresponding equivalent capacitor current frequency can be determined based on the modulation coefficient and switching frequency of the motor, and the equivalent resistance value R of the DC-Link capacitor can be further determined by continuing to look up the table using this frequency. Using the power loss formula P loss =I 2 R, which ultimately determines the power loss P of the capacitor loss .

[0051] Back to Figure 2 , and determine the power loss P of the DC bus capacitor loss Simultaneously or subsequently to the step of measuring at least one reference temperature around the DC bus capacitor, the reference temperature may include, for example, the surface temperature of the control circuit board (also referred to as "PCB temperature") T pcb , the surface temperature of the heat sink on the circuit board (also called "heat sink temperature") T cooler And the air temperature T of the surrounding environment of the DC bus capacitor ambient .

[0052] In addition, the method also includes the step of obtaining the current speed of the motor, and based on the current speed of the motor, a thermal network model of the DC bus capacitor (also called "DC-Link capacitor") can be further determined, especially various thermal resistance and thermal capacitance parameters in the thermal network model. Based on the thermal network model, the power loss P of the DC bus capacitor determined loss The measured reference temperature can be used to estimate the temperature condition of the DC bus capacitor, including the internal temperature T N , Shell temperature T ref and the temperature difference T between the inside and outside temperatures Δ .

[0053] Figure 4 A schematic diagram of a thermal network model of a DC bus capacitor according to an exemplary embodiment of the present invention is shown. The thermal network model particularly includes a first thermal resistor R1 and a first thermal capacitor C1 between the DC bus capacitor and the surrounding environment, a second thermal resistor R2 and a second thermal capacitor C2 between the DC bus capacitor and the heat sink, and a third thermal resistor R3 and a third thermal capacitor C3 between the DC bus capacitor and the drive control circuit board.

[0054] exist Figure 4 In, T Nrepresents the hotspot temperature inside the capacitor, T1 represents the node between the air temperature and the hotspot inside the capacitor, T2 represents the node between the cooler temperature and the hotspot, and T3 represents the node between the PCB temperature and the hotspot. The thermal capacitance C between each node 11 ~C 32 and thermal resistance R 11 ~R 32 Can be determined based on the motor speed.

[0055] The above nodes T1, T2, T3, T N The temperature calculation formula is as follows:

[0056]

[0057] Where, heat capacity C, reference temperature (i.e., measurement / input temperature T input ), power loss P, estimated temperature (i.e., output temperature) T out And the calculation matrices I and D are defined as follows:

[0058]

[0059]

[0060] In the above heat capacity definition formula C, C ges =C 11 +C 21 +C 31 In particular, the internal temperature of the DC link capacitor, T N The power loss P of the first to third thermal resistors R1 to R3, the first to third thermal capacitors C1 to C3 and the DC bus capacitor can be calculated based on the power loss P of the first to third thermal resistors R1 to R3, the first to third thermal capacitors C1 to C3 and the DC bus capacitor. loss To calculate.

[0061] based on Figure 4 The thermal network model in the DC-LINK capacitor case temperature T ref The surface temperature T of the circuit board can be controlled based on the first to third thermal resistances R1 to R3 and the pcb , the surface temperature of the heat sink T cooler And the air temperature T of the surrounding environment of the DC bus capacitor ambient To calculate, the calculation formula is as follows:

[0062]

[0063] In the above formula:

[0064] R1=R 11 +R 12 , R2=R 21 +R 22 , R3=R31 +R 32 .

[0065] Based on Hotspot temperature T N and shell temperature T ref The internal and external temperature difference of the DC-LINK capacitor can be further calculated:

[0066] T Δ =T N -T ref .

[0067] When the hotspot temperature of the DC-LINK capacitor is T N Higher than the first threshold, and / or the internal and external temperature difference T Δ When the voltage is higher than the second threshold, the output power of the inverter is adjusted to perform a derating operation on the motor.

[0068] According to the temperature estimation method of the DC bus capacitor of the present application, not only the shell temperature of the capacitor can be estimated, but also its Hotspot temperature can be estimated, so that the motor can be timely derated by combining the estimated results of the shell temperature, Hotspot temperature and the internal and external temperature difference. The temperature estimation method can realize the accurate estimation of the Hotspot temperature by using the existing external temperature sensors (Cooler temperature, PCB temperature and air temperature) without increasing the BOM cost. In addition, the method uses the motor speed as the key determining factor affecting the thermal resistance and thermal capacity in the thermal network model of the capacitor, and can accurately detect the hotspot temperature of the capacitor within the full speed range of the motor, so as to take protective measures in time, such as adjusting the motor current or improving the heat dissipation function of the radiator, so as to ensure that the capacitor works within a safe temperature range, which helps to extend the service life of the bus capacitor and ensure the reliable operation of the motor, reducing the maintenance cost of the motor.

[0069] In another exemplary embodiment of the present application, a computer-readable storage medium is provided on which a computer program is stored. The program includes executable program instructions, which can implement the various steps of the temperature estimation method described in any embodiment of the present invention when executed by, for example, a processor.

[0070] In another exemplary embodiment of the present application, a drive control circuit board for a motor is also provided, which includes: a power stage circuit, which is used to convert a DC signal provided by an external power supply into an AC signal for driving the motor; a heat dissipation device, which is arranged near the power stage circuit; a DC bus capacitor, which is connected across the positive DC bus and the negative DC bus of the external power supply; and a control unit, which is configured to control the operating state of each switching tube in the power stage circuit, wherein the control unit includes: a computer-readable storage medium as described in any embodiment of the present invention; and a processor, which is configured to execute program instructions stored in the computer-readable storage medium to estimate the temperature condition of the DC bus capacitor.

[0071] It will be appreciated by those skilled in the art that the method steps described in the present application can be performed in a given order. However, it should be noted that different orders are also possible. The method may include additional method steps that are not listed. In addition, two or more of the method steps may be performed simultaneously or in a temporally overlapping manner. In addition, it will be appreciated by those skilled in the art that the example implementations herein may be implemented by software or by software combined with necessary hardware. Therefore, the technical solution according to the implementation of the present application may be embodied in the form of a software product, which may be stored in a non-volatile storage medium or on a network, and includes a number of instructions to enable a computing device to perform a temperature estimation method according to the implementation of the present application.

[0072] Although the present application has been disclosed as above with preferred embodiments, the present application is not limited thereto. Any changes and modifications made by any person skilled in the art without departing from the spirit and scope of the present application should be included in the protection scope of the present application, and therefore the protection scope of the present application should be subject to the scope defined by the claims.

Claims

1. A method for estimating the temperature of a DC bus capacitor, wherein the DC bus capacitor is arranged on a drive control circuit board of a motor, the drive control circuit board further comprises a power stage circuit and a heat dissipation device arranged near the power stage circuit, the power stage circuit is used to convert a DC signal provided by an external power supply into an AC signal for driving the motor, the DC bus capacitor is connected across a positive DC bus and a negative DC bus connected to the external power supply, characterized in that: The method comprises the following steps: Obtain at least one operating parameter of the motor, and input the obtained at least one operating parameter into a pre-calibrated lookup table to determine the power loss P of the DC bus capacitor. loss ; measuring at least one reference temperature around the DC bus capacitor; Acquire the current speed of the motor, and determine the thermal network model of the DC bus capacitor based on the current speed of the motor; as well as Based on the thermal network model, the power loss P of the DC bus capacitor is determined. loss and the at least one reference temperature to estimate the temperature condition of the DC bus capacitor.

2. The method for estimating the temperature of a DC bus capacitor according to claim 1, characterized in that: The at least one reference temperature includes the surface temperature T of the driving control circuit board pcb , the surface temperature T of the heat sink cooler and the ambient air temperature T of the DC bus capacitor ambient .

3. The method for estimating the temperature of a DC bus capacitor according to claim 2, characterized in that: The thermal network model includes a first thermal resistance and a first thermal capacitance between the DC bus capacitor and the surrounding environment, a second thermal resistance and a second thermal capacitance between the DC bus capacitor and the heat sink, and a third thermal resistance and a third thermal capacitance between the DC bus capacitor and the drive control circuit board.

4. The method for estimating the temperature of a DC bus capacitor according to claim 3, characterized in that: The temperature condition of the DC bus capacitor includes the internal temperature T of the DC bus capacitor. N , Shell temperature T ref And the internal temperature T N With the shell temperature T ref The temperature difference T Δ .

5. The method for estimating the temperature of a DC bus capacitor according to claim 4, characterized in that: The method further comprises: Based on the first to third thermal resistances, the surface temperature T of the driving control circuit board pcb , the surface temperature T of the heat sink cooler and the ambient air temperature T of the DC bus capacitor ambient To calculate the shell temperature T of the DC bus capacitor ref .

6. The method for estimating the temperature of a DC bus capacitor according to claim 5, characterized in that: The method further comprises: The power loss P based on the first to third thermal resistances, the first to third thermal capacitances and the DC bus capacitor loss To calculate the internal temperature T of the DC bus capacitor N .

7. The method for estimating the temperature of a DC bus capacitor according to claim 6, characterized in that: The method further includes performing a derating operation on the motor when any of the following conditions is met: The internal temperature T N is above a first threshold; and The internal temperature T N With the shell temperature T ref The temperature difference T Δ is higher than the second threshold.

8. The method for estimating the temperature of a DC bus capacitor according to any one of claims 1 to 5, characterized in that: The at least one operating parameter includes at least one of a phase current, a phase deviation angle, a modulation factor, and a switching frequency of the motor.

9. A computer-readable storage medium having a computer program stored thereon, the computer program comprising program instructions, characterized in that: When the program instructions are executed by a processor, the steps of the temperature estimation method according to any one of claims 1 to 8 are implemented.

10. A drive control circuit board for a motor, characterized in that: The drive control circuit board includes: A power stage circuit, the power stage circuit is used to convert a DC signal provided by an external power source into an AC signal for driving the motor; a heat sink, the heat sink being arranged near the power stage circuit; A DC bus capacitor connected between a positive DC bus and a negative DC bus connected to the external power source; and A control unit, the control unit is configured to control the operating state of each switch tube in the power stage circuit, wherein the control unit includes: - A computer readable storage medium according to claim 9; and - a processor configured to execute program instructions stored in the computer-readable storage medium to estimate a temperature condition of the DC bus capacitor.

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