Power module junction temperature estimation method

Abstract

The invention discloses a power module junction temperature estimation method, which comprises the following steps of: calculating the total loss of a power component based on input three-phase current, three-phase duty ratio, bus voltage, sector position and carrier frequency; according to the obtained total loss and the DBC temperature collected in real time, the cooling water flow is estimated through a temperature difference method; based on the obtained total loss, the cooling water flow and the real-time DBC temperature, the cooling water estimated temperature of the corresponding phase is calculated; calculating the junction temperature by using the obtained total loss, the thermal resistance value corresponding to the cooling water flow and the obtained estimated temperature of the cooling water; and after the obtained three-phase junction temperature is maximized, a compensation table is selected according to the working condition of the motor to carry out compensation correction, and the high-precision estimated junction temperature is output. According to the method, cooling parameters are dynamically obtained through a collaborative estimation process, compensation is carried out according to working conditions, and high-precision junction temperature estimation without a direct temperature sensor is achieved.

Description

Technical Field

[0001] This invention relates to the field of spot welding diagnostic and evaluation technology, and in particular to a method for estimating the junction temperature of a power module. Background Technology

[0002] In existing technologies, power module junction temperature estimation primarily relies on complex model calculations and extensive parameter calibration. While these methods are relatively accurate under steady-state conditions, their accuracy drops significantly under complex operating conditions (such as fluctuating or completely stopping coolant flow). For example, some OEMs use an average loss model based on a fixed coolant flow rate to estimate junction temperature, which can predict the junction temperature relatively accurately when the flow rate is stable. However, when the coolant flow rate suddenly decreases or even stops completely, this traditional model will severely underestimate the junction temperature, thus affecting the safe operation of the power module. Furthermore, although some OEMs have proposed compensation strategies for low or zero flow rates, these strategies either rely on tabular lookup methods based on measured data or on complex correction calculations, both of which have room for improvement in practical applications, especially the accuracy issue under complex operating conditions, which has not yet been completely resolved. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the existing technology. To achieve the above objective, a power module junction temperature estimation method is adopted to solve the problems mentioned in the background technology.

[0004] A method for estimating the junction temperature of a power module includes the following steps:

[0005] S1. Calculate the total loss of power components based on the input three-phase current, three-phase duty cycle, bus voltage, sector position, and carrier frequency.

[0006] S2. Based on the total loss and the real-time collected DBC temperature, estimate the cooling water flow rate using the temperature difference method;

[0007] S3. Based on the obtained total loss, cooling water flow rate, and real-time DBC temperature, calculate the estimated cooling water temperature for the corresponding phase.

[0008] S4. Using the total loss, the thermal resistance value corresponding to the cooling water flow rate, and the estimated cooling water temperature, calculate the junction temperature.

[0009] S5. After taking the maximum value of the obtained three-phase junction temperature, select the compensation table according to the motor operating conditions for compensation and correction, and output a high-precision estimated junction temperature.

[0010] As a further technical solution of the present invention: the total loss of power components includes IGBT loss and diode loss, wherein the IGBT loss is the sum of IGBT conduction loss and IGBT switching loss, and the diode loss is the sum of diode conduction loss and diode reverse recovery loss.

[0011] As a further technical solution of the present invention: the temperature difference method includes:

[0012] Normal mode: Estimate the flow rate based on the coefficient relationship table between the calibrated total loss and the temperature difference between the UW phase DBC, and input the absolute value of the rotational speed and the current value from the table;

[0013] Locked rotor mode: When the absolute value of the phase current V phase is the largest, select the coefficient relationship between the total loss of phase UV or phase VW and the corresponding DBC temperature difference and look up the table. The input for the lookup table is the phase V current value.

[0014] When the absolute value of the U-phase current is at its maximum, it represents the coefficient relationship between the total loss and the temperature difference between the UW-phase DBC and the U-phase current. The U-phase current value is then entered by referring to the table.

[0015] When the absolute value of the W-phase current is at its maximum, it represents the coefficient relationship between the total loss and the temperature difference between the UW-phase DBC and the W-phase current. The W-phase current value is then entered from the table.

[0016] As a further technical solution of the present invention: the flow estimation of the stall mode is specifically as follows: when the absolute value of the V phase current is the largest, the UV / VW phase parameters are looked up in the table; otherwise, the UW phase parameters are looked up in the table. The input for the table lookup is the absolute value of the U phase or W phase current.

[0017] As a further technical solution of the present invention: the estimated temperature of the cooling water is calculated by the following formula:

[0018] T_cool=T_DBC-Σ(P_component×R_th);

[0019] Where T_cool is the estimated temperature of the cooling water, T_DBC is the real-time collected DBC temperature, P_component is the power loss of each power component, and R_th is the corresponding thermal resistance.

[0020] As a further technical solution of the present invention: the thermal resistance value is obtained by referring to the pre-calibrated thermal resistance-flow rate relationship table by the cooling water flow rate obtained in step S2.

[0021] As a further technical solution of the present invention: the motor operating conditions include normal operating conditions and stalled operating conditions, wherein the normal operating conditions include electric mode and generator mode, and each mode corresponds to an independent compensation table.

[0022] As a further technical solution of the present invention: the compensation table lookup input under normal operating conditions is the absolute value of the rotational speed and the current value.

[0023] As a further technical solution of the present invention: the compensation table lookup input for the stalled rotor condition is the current value of the phase with the largest absolute value among the three-phase currents.

[0024] As a further technical solution of the present invention: the IGBT switching loss includes turn-on loss and turn-off loss, and the diode reverse recovery loss includes turn-off loss.

[0025] Compared with the prior art, the present invention has the following technical advantages:

[0026] The above technical solution utilizes three-phase current, duty cycle, and other electronic control parameters to calculate IGBT and diode losses in real time; it also employs a combination of loss estimation and DBC temperature difference method to dynamically estimate flow rate; it separates water temperature from DBC temperature using a thermal resistance model; it performs initial junction temperature calculation based on losses, thermal resistance, and water temperature; and it uses a compensation table selected according to motor mode to correct the maximum value of the three-phase junction temperature. By compensating and calibrating the junction temperature values ​​under different operating conditions, the accuracy of junction temperature estimation can be greatly improved. The performance of the power module can be fully utilized and will not be damaged under various complex operating conditions. Attached Figure Description

[0027] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings:

[0028] Figure 1 This is a schematic diagram illustrating the steps of the junction temperature estimation method according to an embodiment of this application;

[0029] Figure 2 This is a flowchart illustrating the junction temperature estimation method according to an embodiment of this application. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Please refer to Figure 1 and Figure 2 In this embodiment of the invention, a method for estimating the junction temperature of a power module includes the following steps:

[0032] S1. Calculate the total loss of power components based on the input three-phase current, three-phase duty cycle, bus voltage, sector position, and carrier frequency.

[0033] The power loss of the current power components can be calculated based on the current input parameters.

[0034] In this embodiment, the total loss of power components includes IGBT loss and diode loss, where IGBT loss is the sum of IGBT conduction loss and IGBT switching loss, and diode loss is the sum of diode conduction loss and diode reverse recovery loss.

[0035] In this embodiment, the IGBT switching loss includes turn-on loss and turn-off loss, and the diode reverse recovery loss includes turn-off loss.

[0036] Specifically, the losses of power components in the first step include IGBT losses and diode losses.

[0037] P = P IGBT +P FWD

[0038] In the formula, P represents the power loss of the power components. IGBT For the losses of IGBT, P FWD This represents the diode's loss.

[0039] IGBT losses include IGBT conduction losses and IGBT switching losses:

[0040] P IGBT =P ic +P is

[0041] In the formula, P IGBT For the losses of IGBT, P ic For the conduction loss of the IGBT, P is For the switching losses of the IGBT;

[0042] Diode losses include diode conduction losses and diode reverse recovery losses:

[0043] P FWD =P dc +P dr

[0044] In the formula, P FWD For the diode loss, P dc For diode conduction loss, P dr This represents the reverse recovery loss of the diode.

[0045] S2. Based on the total loss and the real-time collected DBC temperature, estimate the cooling water flow rate using the temperature difference method;

[0046] Based on the collected DBC temperature and the power component losses calculated in the previous step, the estimated flow rate of cooling water is calculated.

[0047] In this embodiment, the temperature difference method includes:

[0048] Normal mode: Estimate the flow rate based on the coefficient relationship table between the calibrated total loss and the temperature difference between the UW phase DBC, and input the absolute value of the rotational speed and the current value from the table;

[0049] Locked rotor mode: When the absolute value of the phase current V phase is the largest, select the coefficient relationship between the total loss of phase UV or phase VW and the corresponding DBC temperature difference and look up the table. The input for the lookup table is the phase V current value.

[0050] When the absolute value of the U-phase current is at its maximum, it represents the coefficient relationship between the total loss and the temperature difference between the UW-phase DBC and the U-phase current. The U-phase current value is then entered by referring to the table.

[0051] When the absolute value of the W-phase current is at its maximum, it represents the coefficient relationship between the total loss and the temperature difference between the UW-phase DBC and the W-phase current. The W-phase current value is then entered from the table.

[0052] In this embodiment, the flow estimation of the stall mode is specifically as follows: when the absolute value of the V phase current is the largest, the UV / VW phase parameters are looked up in the table; otherwise, the UW phase parameters are looked up in the table. The input for the table lookup is the absolute value of the U phase or W phase current.

[0053] Specifically, in the second step, based on the power component losses obtained in the first step and the collected DBC temperature, the estimated flow rate is obtained using the temperature difference method. This can be divided into normal mode and locked-rotor mode. In normal mode, the estimated flow rate is obtained by calibrating a coefficient relationship table between the total losses of the three-phase power components and the DBC temperature difference between the U and W phases. The input for the coefficient relationship table is the rotational speed and current. In locked-rotor mode, the three-phase currents are first compared. If the absolute value of the V phase current is the largest, a coefficient relationship table between the total losses of the UV (which can be switched to VW) two-phase power components and the DBC temperature difference between the UV (which can be switched to VW) two-phase power components is calibrated. The coefficient relationship table is a lookup table for the V phase current. Otherwise, a coefficient relationship table between the total losses of the three-phase power components and the DBC temperature difference between the U and W phases is calibrated. The coefficient relationship table is a lookup table for the U (when the absolute value of the U phase current is the largest) or W (when the absolute value of the W phase current is the largest) phase current is calibrated.

[0054] S3. Based on the obtained total loss, cooling water flow rate, and real-time DBC temperature, calculate the estimated cooling water temperature for the corresponding phase.

[0055] Based on the collected DBC temperature, power component losses, and estimated cooling water flow rate, the estimated cooling water temperature for the corresponding phase can be obtained.

[0056] Specifically, in the third step, the estimated cooling water temperature of the corresponding phase can be obtained based on the power device losses obtained in the first step, the estimated cooling water flow rate in the second step, and the collected DBC temperature. The DBC temperature is mainly affected by the cooling water temperature and the temperature rise caused by the power device losses. Therefore, the temperature rise of the cooling water is obtained by subtracting the temperature rise caused by the power device losses from the DBC temperature. The temperature rise is calculated by multiplying the losses of different components by the sum of their corresponding thermal resistances.

[0057] S4. Using the total loss, the thermal resistance value corresponding to the cooling water flow rate, and the estimated cooling water temperature, calculate the junction temperature.

[0058] The estimated junction temperature is obtained by estimating the flow rate and temperature of the power components and the cooling water.

[0059] In this embodiment, the estimated temperature of the cooling water is calculated using the following formula:

[0060] T_cool=T_DBC-Σ(P_component×R_th);

[0061] Where T_cool is the estimated temperature of the cooling water, T_DBC is the real-time collected DBC temperature, P_component is the power loss of each power component, and R_th is the corresponding thermal resistance.

[0062] In this embodiment, the thermal resistance value is obtained by referring to the pre-calibrated thermal resistance-flow rate relationship table using the cooling water flow rate obtained in step S2.

[0063] Specifically, in the fourth step, the power component losses obtained in the first step, the thermal resistance obtained by estimating the cooling water flow rate in the second step, and the cooling water temperature obtained in the third step are used. The power component losses are multiplied by the thermal resistance to obtain the temperature rise relative to the cooling water temperature. Then, the estimated cooling water temperature is added to obtain the junction temperature.

[0064] S5. After taking the maximum value of the obtained three-phase junction temperature, select the compensation table according to the motor operating conditions for compensation and correction, and output a high-precision estimated junction temperature.

[0065] Specifically, different compensation methods are selected according to different motor operating conditions. When the motor is in normal operating condition, the maximum value of the three-phase junction temperature is taken and then compensated and corrected. When the motor is in stalled operating condition, the junction temperature of the three phases is first compensated and corrected and then the maximum value is taken to output a high-precision estimated junction temperature.

[0066] In this embodiment, the motor operating conditions include normal operating conditions and stalled operating conditions. The normal operating conditions include electric mode and generator mode, each with its own independent compensation table. The stalled operating conditions include three independent compensation tables for the U, V, and W phases.

[0067] In this embodiment, the input for the compensation table lookup under normal operating conditions is the absolute value of the rotational speed and the current value.

[0068] In this embodiment, the compensation table for the stalled rotor condition consists of three compensation tables for phases U, V, and W, and the input for looking up the tables is the corresponding phase current value.

[0069] Specifically, in step five, different compensation methods are selected based on different motor operating conditions to obtain more accurate estimated junction temperatures. When the motor is in normal operating condition, the maximum value of the three-phase junction temperature is processed and then compensated to output the final junction temperature. In normal operating condition, two different compensation tables are used to distinguish between motor mode and generator mode, with the axis of the table being the absolute value of the speed and the current. When the motor is in stalled operating condition, the junction temperatures of the U, V, and W phases are first compensated and corrected, and then the maximum value is taken as the final junction temperature output. In stalled operating condition, there are three compensation tables, corresponding to the U, V, and W phases respectively, with the axis of the table being the corresponding phase current.

[0070] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention. The scope of the invention is defined by the appended claims and their equivalents, all of which should be included within the scope of protection of the invention.

Claims

1. A method for estimating the junction temperature of a power module, characterized in that, Includes the following steps: S1. Calculate the total loss of power components based on the input three-phase current, three-phase duty cycle, bus voltage, sector position, and carrier frequency. S2. Based on the total loss and the real-time collected DBC temperature, estimate the cooling water flow rate using the temperature difference method; S3. Based on the obtained total loss, cooling water flow rate, and real-time DBC temperature, calculate the estimated cooling water temperature for the corresponding phase. S4. Using the total loss, the thermal resistance value corresponding to the cooling water flow rate, and the estimated cooling water temperature, calculate the junction temperature. S5. After taking the maximum value of the obtained three-phase junction temperature, select the compensation table according to the motor operating conditions for compensation and correction, and output a high-precision estimated junction temperature.

2. The method for estimating the junction temperature of a power module according to claim 1, characterized in that, The total losses of the power components include IGBT losses and diode losses, where IGBT losses are the sum of IGBT conduction losses and IGBT switching losses, and diode losses are the sum of diode conduction losses and diode reverse recovery losses.

3. The method for estimating the junction temperature of a power module according to claim 1, characterized in that, The temperature difference method includes: Normal mode: Estimate the flow rate based on the coefficient relationship table between the calibrated total loss and the temperature difference between the UW phase DBC, and input the absolute value of the rotational speed and the current value from the table; Locked rotor mode: When the absolute value of the phase current V phase is the largest, select the coefficient relationship between the total loss of phase UV or phase VW and the corresponding DBC temperature difference and look up the table. The input for the lookup table is the phase V current value. When the absolute value of the U-phase current is at its maximum, it represents the coefficient relationship between the total loss and the temperature difference between the UW-phase DBC and the U-phase current. The U-phase current value is then entered by referring to the table. When the absolute value of the W-phase current is at its maximum, it represents the coefficient relationship between the total loss and the temperature difference between the UW-phase DBC and the W-phase current. The W-phase current value is then entered from the table.

4. The method for estimating the junction temperature of a power module according to claim 3, characterized in that, The flow estimation in the stall mode is as follows: when the absolute value of the V phase current is the largest, the UV / VW phase parameters are looked up in the table; otherwise, the UW phase parameters are looked up in the table. The input for the table lookup is the absolute value of the U phase or W phase current.

5. The method for estimating the junction temperature of a power module according to claim 1, characterized in that, The estimated temperature of the cooling water is calculated using the following formula: T_cool=T_DBC-Σ(P_component×R_th); Where T_cool is the estimated temperature of the cooling water, T_DBC is the real-time collected DBC temperature, P_component is the power loss of each power component, and R_th is the corresponding thermal resistance.

6. The method for estimating the junction temperature of a power module according to claim 1, characterized in that, The thermal resistance value is obtained by referring to the pre-calibrated thermal resistance-flow rate relationship table using the cooling water flow rate obtained in step S2.

7. The method for estimating the junction temperature of a power module according to claim 1, characterized in that, The motor operating conditions include normal operating conditions and stalled operating conditions. The normal operating conditions include electric mode and generator mode, and each mode corresponds to an independent compensation table.

8. The method for estimating the junction temperature of a power module according to claim 7, characterized in that, Under normal operating conditions, the input for the compensation table lookup is the absolute value of the rotational speed and the current value.

9. The method for estimating the junction temperature of a power module according to claim 7, characterized in that, The compensation table for stalled rotor operation is entered by looking up the current value of the phase with the largest absolute value among the three-phase currents.

10. The method for estimating the junction temperature of a power module according to claim 2, characterized in that, The IGBT switching loss includes turn-on loss and turn-off loss, and the diode reverse recovery loss includes turn-off loss.

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