Method and system for online monitoring of health status of insulated-gate bipolar transistor module

Abstract

A method and a system for online monitoring of a health status of an insulated-gate bipolar transistor (IGBT) module are provided, which belong to the field of IGBT status monitoring. In order to overcome the inability to real-time monitor health statuses of existing IGBT modules, the method of the disclosure includes the following steps. A current sensor is used to measure a collector current of each IGBT module. A collected current value is substituted into a simulation model to obtain a current imbalance rate. A failure module is located according to the current imbalance rate and temperature to achieve the objective of monitoring an IGBT health status.

Claims

1. A method for online monitoring of a health status of a plurality of insulated-gate bipolar transistor (IGBT) modules coupled in parallel, each IGBT module comprising at least one IGBT, the method comprising: determining an abnormal IGBT module from the IGBT modules according to a collector current value of each IGBT module among the IGBT modules; extracting the collector current value of the abnormal IGBT module to be compared with a maximum value among measured collector current values of normal IGBT modules determined from the IGBT modules to obtain a current imbalance rate of the abnormal IGBT module; determining a type of abnormality of the abnormal IGBT module according to a case temperature of each IGBT module among the IGBT modules; and substituting for the current imbalance rate and the case temperature of the abnormal IGBT module into a parallel IGBT health status detection model for the abnormal IGBT module, and determining whether the abnormal IGBT module fails according to the type of abnormality of the abnormal IGBT module.

2. The method according to claim 1, wherein the step of determining the abnormal IGBT module from the IGBT modules according to the collector current value of each IGBT module among the IGBT modules comprises: comparing the collector current value of each IGBT module among the IGBT modules, and regarding the IGBT module with the collector current value less than a preset current value as the abnormal IGBT module; and the step of determining the type of abnormality of the abnormal IGBT module according to the case temperature of each IGBT module among the parallel IGBT modules comprises: comparing the case temperature of the abnormal IGBT module, regarding the abnormal IGBT module with the case temperature less than a preset case temperature value as an abnormal bonding wire IGBT module, and regarding the abnormal IGBT module with the case temperature equal to the preset case temperature value as an abnormal solder layer IGBT module.

3. The method according to claim 2, wherein the current imbalance rate of the abnormal IGBT module is determined from $\alpha =\frac{I_C^{\prime }}{I_C},$ where I.sub.C is the maximum value among the measured collector current values of the normal IGBT modules, and I.sub.C′ is the collector current value of the abnormal IGBT module.

4. The method according to claim 3, wherein the parallel IGBT health status detection model is: $\frac{I_C^{\prime }}{I_C}=\frac{\left[V_{\mathrm{dc}}-\left(V_o+\Delta V\right)\right]R-\left(n-1\right).Math.R_{\mathrm{load}}.Math.\Delta V}{\left(V_{\mathrm{dc}}-V_o\right)\left(R+\Delta R+\Delta R^{\prime }\right)+R_{\mathrm{load}}.Math.\Delta V}$ $if\Delta V=0,\mathrm{then}\alpha =\frac{R}{R+\Delta R+\Delta R^{\prime }}$ $\{\begin{array}{c}\Delta V=\frac{V_o^{\max }-V_o^{typ}}{T^{\max }-T^{typ}}\left(T_j-T^{typ}\right)+V_o^{typ}=k_1\Delta T_j+b_1\\ \Delta R=\frac{R^{\max }-R^{typ}}{T^{\max }-T^{typ}}\left(T_j-T^{typ}\right)+R^{typ}=k_2\Delta T_j+b_2\end{array}{T}_j=P_{loss}.Math.r_{jc}+T_C=\left(P_{sw}+P_{\mathrm{cond}}\right).Math.r_{jc}+T_C\Delta T_j=P_{loss}.Math.\Delta r_{jc}+T_C=\left(P_{sw}+P_{\mathrm{cond}}\right).Math.\Delta r_{jc}+T_C$ wherein V.sub.dc is an external voltage of a main circuit, V.sub.o is an on voltage of the IGBT module when a temperature is at a room temperature of 25° C., R is an on resistance of the IGBT module when the temperature is at the room temperature of 25° C., ΔV is an increment of the on voltage at different temperatures, ΔR is an increment of the on resistance at different temperatures, ΔR′ is an increment of the on resistance when a bonding wire within the IGBT module is broken, R.sub.load is a load resistance, v.sub.o.sup.max is an on voltage value at a maximum temperature T.sup.max given in a data sheet, V.sub.o.sup.typ is the on voltage value at a typical temperature T.sup.typ given in the data sheet, R.sup.max is an on resistance value at the maximum temperature T.sup.max given in the data sheet, R.sup.typ is the on resistance value at the typical temperature T.sup.typ given in the data sheet, T.sub.j is a real-time working temperature of an internal chip of the IGBT module, n represents a coefficient corresponding to a format of how the IGBT modules are coupled in parallel, k.sub.1 and b.sub.1 represent function coefficients of the on voltage changing with temperature, k.sub.2 and b.sub.2 represent function coefficients of the on resistance changing with temperature, ΔT.sub.j represents an increment of a junction temperature caused by different failure processes, P.sub.loss represents a power loss of the IGBT module, which comprises a switching power loss P.sub.sw and a conduction power loss P.sub.cond, r.sub.jc represents a thermal resistance of the IGBT module from a chip to a case, T.sub.C represents the case temperature of the IGBT module, and Δr.sub.jc represents an increment of the thermal resistance caused by different failure processes.

5. The method according to claim 4, wherein the step of determining whether the abnormal IGBT module fails according to the type of abnormality of the abnormal IGBT module comprises: obtaining the increment of the on resistance of the abnormal IGBT module at different temperatures from the parallel IGBT health status detection model in a case where the type of abnormality of the abnormal IGBT module is a bonding wire breakage abnormality, and determining whether the increment of the on resistance of the abnormal IGBT module at different temperatures is greater than a preset resistance increment value; wherein if the increment of the on resistance is greater than the preset resistance increment value, it is determined that the abnormal IGBT module fails due to bonding wire breakage, or otherwise, it is determined that the abnormal IGBT module does not fail; and obtaining the increment of the thermal resistance of the abnormal IGBT module from the parallel IGBT health status detection model in a case where the type of abnormality of the abnormal IGBT module is a solder layer aging abnormality, and determining whether the increment of the thermal resistance of the abnormal IGBT module is greater than a preset thermal resistance increment value, wherein if the increment of the thermal resistance is greater than the preset thermal resistance increment value, it is determined that the IGBT module fails due to solder layer aging, or otherwise, it is determined that the IGBT module does not fail.

6. The method according to claim 1, wherein the current imbalance rate of the abnormal IGBT module is determined from $\alpha =\frac{I_C^{\prime }}{I_C},$ where I.sub.C is the maximum value among the measured collector current values of the normal IGBT modules, and I.sub.C′ is the collector current value of the abnormal IGBT module.

7. The method according to claim 6, wherein the parallel IGBT health status detection model is: $\frac{I_C^{\prime }}{I_C}=\frac{\left[V_{\mathrm{dc}}-\left(V_o+\Delta V\right)\right]R-\left(n-1\right).Math.R_{\mathrm{load}}.Math.\Delta V}{\left(V_{\mathrm{dc}}-V_o\right)\left(R+\Delta R+\Delta R^{\prime }\right)+R_{\mathrm{load}}.Math.\Delta V}$ $if\Delta V=0,\mathrm{then}\alpha =\frac{R}{R+\Delta R+\Delta R^{\prime }}$ $\{\begin{array}{c}\Delta V=\frac{V_o^{\max }-V_o^{typ}}{T^{\max }-T^{typ}}\left(T_j-T^{typ}\right)+V_o^{typ}=k_1\Delta T_j+b_1\\ \Delta R=\frac{R^{\max }-R^{typ}}{T^{\max }-T^{typ}}\left(T_j-T^{typ}\right)+R^{typ}=k_2\Delta T_j+b_2\end{array}{T}_j=P_{loss}.Math.r_{jc}+T_C=\left(P_{sw}+P_{\mathrm{cond}}\right).Math.r_{jc}+T_C\Delta T_j=P_{loss}.Math.\Delta r_{jc}+T_C=\left(P_{sw}+P_{\mathrm{cond}}\right).Math.\Delta r_{jc}+T_C$ wherein V.sub.dc is an external voltage of a main circuit, V.sub.o is an on voltage of the IGBT module when a temperature is at a room temperature of 25° C., R is an on resistance of the IGBT module when the temperature is at the room temperature of 25° C., ΔV is an increment of the on voltage at different temperatures, ΔR is an increment of the on resistance at different temperatures, ΔR′ is an increment of the on resistance when a bonding wire within the IGBT module is broken, R.sub.load is a load resistance, v.sub.o.sup.max is an on voltage value at a maximum temperature T.sup.max given in a data sheet, V.sub.o.sup.typ is the on voltage value at a typical temperature T.sup.typ given in the data sheet, R.sup.max is an on resistance value at the maximum temperature T.sup.max given in the data sheet, R.sup.typ is the on resistance value at the typical temperature T.sup.typ given in the data sheet, T.sub.j is a real-time working temperature of an internal chip of the IGBT module, n represents a coefficient corresponding to a format of how the IGBT modules are coupled in parallel, k.sub.1 and b.sub.1 represent function coefficients of the on voltage changing with temperature, k.sub.2 and b.sub.2 represent function coefficients of the on resistance changing with temperature, ΔT.sub.j represents an increment of a junction temperature caused by different failure processes, P.sub.loss represents a power loss of the IGBT module, which comprises a switching power loss P.sub.sw and a conduction power loss P.sub.cond, r.sub.jc represents a thermal resistance of the IGBT module from a chip to a case, T.sub.C represents the case temperature of the IGBT module, and Δr.sub.jc represents an increment of the thermal resistance caused by different failure processes.

8. The method according to claim 7, wherein the step of determining whether the abnormal IGBT module fails according to the type of abnormality of the abnormal IGBT module comprises: obtaining the increment of the on resistance of the abnormal IGBT module at different temperatures from the parallel IGBT health status detection model in a case where the type of abnormality of the abnormal IGBT module is a bonding wire breakage abnormality, and determining whether the increment of the on resistance of the abnormal IGBT module at different temperatures is greater than a preset resistance increment value; wherein if the increment of the on resistance is greater than the preset resistance increment value, it is determined that the abnormal IGBT module fails due to bonding wire breakage, or otherwise, it is determined that the abnormal IGBT module does not fail; and obtaining the increment of the thermal resistance of the abnormal IGBT module from the parallel IGBT health status detection model in a case where the type of abnormality of the abnormal IGBT module is a solder layer aging abnormality, and determining whether the increment of the thermal resistance of the abnormal IGBT module is greater than a preset thermal resistance increment value, wherein if the increment of the thermal resistance is greater than the preset thermal resistance increment value, it is determined that the IGBT module fails due to solder layer aging, or otherwise, it is determined that the IGBT module does not fail.

9. A system for online monitoring of a health status of a plurality of IGBT modules coupled in parallel, each IGBT module comprising at least one IGBT, the system comprising: a memory storing a program code; and a controller configured to access the program code for executing: an abnormality determination module, configured to determine an abnormal IGBT module from the IGBT modules according to a collector current value of each IGBT module among the IGBT modules; a current imbalance rate calculation module, configured to extract the collector current value of the abnormal IGBT module to be compared with a maximum value among measured collector current values of normal IGBT modules determined from the IGBT modules to obtain a current imbalance rate of the abnormal IGBT module; an abnormal type determination module, configured to determine a type of abnormality of the abnormal IGBT module according to a case temperature of each IGBT module among the IGBT modules; and a failure determination module, configured to substituting for the current imbalance rate and the case temperature of the abnormal IGBT module into a parallel IGBT health status detection model for the abnormal IGBT module, and determine whether the abnormal IGBT module fails according to the type of abnormality of the abnormal IGBT module.

10. The system according to claim 9, wherein the controller is configured to execute: the abnormality determination module for comparing the collector current value of each IGBT module among the IGBT modules, and regarding the IGBT module with the collector current value less than a preset current value as the abnormal IGBT module; and the abnormal type determination module for comparing the case temperature of the abnormal IGBT module, regarding the abnormal IGBT module with the case temperature less than a preset case temperature value as an abnormal bonding wire IGBT module, and regarding the abnormal IGBT module with the case temperature equal to the preset case temperature value as an abnormal solder layer IGBT module.

11. The system according to claim 10, wherein the current imbalance rate of the module is determined from $\alpha =\frac{I_C^{\prime }}{I_C},$ where I.sub.C is the maximum value among the measured collector current values of the normal IGBT modules, and I.sub.C′ is the collector current value of the abnormal IGBT module.

12. The system according to claim 11, wherein the parallel IGBT health status detection model is: $\frac{I_C^{\prime }}{I_C}=\frac{\left[V_{\mathrm{dc}}-\left(V_o+\Delta V\right)\right]R-\left(n-1\right).Math.R_{\mathrm{load}}.Math.\Delta V}{\left(V_{\mathrm{dc}}-V_o\right)\left(R+\Delta R+\Delta R^{\prime }\right)+R_{\mathrm{load}}.Math.\Delta V}$ $if\Delta V=0,\mathrm{then}\alpha =\frac{R}{R+\Delta R+\Delta R^{\prime }}$ $\{\begin{array}{c}\Delta V=\frac{V_o^{\max }-V_o^{typ}}{T^{\max }-T^{typ}}\left(T_j-T^{typ}\right)+V_o^{typ}=k_1\Delta T_j+b_1\\ \Delta R=\frac{R^{\max }-R^{typ}}{T^{\max }-T^{typ}}\left(T_j-T^{typ}\right)+R^{typ}=k_2\Delta T_j+b_2\end{array}{T}_j=P_{loss}.Math.r_{jc}+T_C=\left(P_{sw}+P_{\mathrm{cond}}\right).Math.r_{jc}+T_C\Delta T_j=P_{loss}.Math.\Delta r_{jc}+T_C=\left(P_{sw}+P_{\mathrm{cond}}\right).Math.\Delta r_{jc}+T_C$ where V.sub.dc is an external voltage of a main circuit, V.sub.o is an on voltage of the IGBT module when a temperature is at a room temperature of 25° C., R is an on resistance of the IGBT module when the temperature is at the room temperature of 25° C., ΔV is an increment of the on voltage at different temperatures, ΔR is an increment of the on resistance at different temperatures, ΔR′ is an increment of the on resistance when a bonding wire within the IGBT module is broken, R.sub.load is a load resistance, V.sub.o.sup.max is an on voltage value at a maximum temperature T.sup.max given in a data sheet, V.sub.o.sup.typ is the on voltage value at a typical temperature T.sup.typ given in the data sheet, R.sup.max is an on resistance value at the maximum temperature T.sup.max given in the data sheet, R.sup.typ is the on resistance value at the typical temperature T.sup.typ given in the data sheet, T.sub.j is a real-time working temperature of an internal chip of the IGBT module, n represents a coefficient corresponding to a format of how the IGBT modules are coupled in parallel, k.sub.1 and b.sub.1 represent function coefficients of the on voltage changing with temperature, k.sub.2 and b.sub.2 represent function coefficients of the on resistance changing with temperature, ΔT.sub.j represents an increment of a junction temperature caused by different failure processes, P.sub.loss represents a power loss of the IGBT module, which comprises a switching power loss P.sub.sw and a conduction power loss P.sub.cond, r.sub.jc represents a thermal resistance of the IGBT module from a chip to a case, T.sub.C represents the case temperature of the IGBT module, and Δr.sub.jc represents an increment of the thermal resistance caused by different failure processes.

13. The system according to claim 12, wherein the controller is configured to execute the failure determination module for obtaining the increment of the on resistance of the abnormal IGBT module at different temperatures from the parallel IGBT health status detection model in a case where the type of abnormality of the abnormal IGBT module is a bonding wire breakage abnormality, and determine whether the increment of the on resistance of the abnormal IGBT module at different temperatures is greater than a preset resistance increment value; wherein if the increment of the on resistance is greater than the preset resistance increment value, it is determined that the abnormal IGBT module fails due to bonding wire breakage, or otherwise, it is determined that the abnormal IGBT module does not fail; and in a case where the type of abnormality of the abnormal IGBT module is a solder layer aging abnormality, the increment of the thermal resistance of the abnormal IGBT module is obtained from the parallel IGBT health status detection model, and whether the increment of the thermal resistance of the abnormal IGBT module is greater than a preset thermal resistance increment value is determined, wherein if the increment of the thermal resistance is greater than the preset thermal resistance increment value, it is determined that the IGBT module fails due to solder layer aging, or otherwise, it is determined that the IGBT module does not fail.

14. The system according to claim 9, wherein the current imbalance rate of the module is determined from $\alpha =\frac{I_C^{\prime }}{I_C},$ where I.sub.C is the maximum value among the measured collector current values of the normal IGBT modules, and I.sub.C′ is the collector current value of the abnormal IGBT module.

15. The system according to claim 14, wherein the parallel IGBT health status detection model is: $\frac{I_C^{\prime }}{I_C}=\frac{\left[V_{\mathrm{dc}}-\left(V_o+\Delta V\right)\right]R-\left(n-1\right).Math.R_{\mathrm{load}}.Math.\Delta V}{\left(V_{\mathrm{dc}}-V_o\right)\left(R+\Delta R+\Delta R^{\prime }\right)+R_{\mathrm{load}}.Math.\Delta V}$ $if\Delta V=0,\mathrm{then}\alpha =\frac{R}{R+\Delta R+\Delta R^{\prime }}$ $\{\begin{array}{c}\Delta V=\frac{V_o^{\max }-V_o^{typ}}{T^{\max }-T^{typ}}\left(T_j-T^{typ}\right)+V_o^{typ}=k_1\Delta T_j+b_1\\ \Delta R=\frac{R^{\max }-R^{typ}}{T^{\max }-T^{typ}}\left(T_j-T^{typ}\right)+R^{typ}=k_2\Delta T_j+b_2\end{array}{T}_j=P_{loss}.Math.r_{jc}+T_C=\left(P_{sw}+P_{\mathrm{cond}}\right).Math.r_{jc}+T_C\Delta T_j=P_{loss}.Math.\Delta r_{jc}+T_C=\left(P_{sw}+P_{\mathrm{cond}}\right).Math.\Delta r_{jc}+T_C$ where V.sub.dc is an external voltage of a main circuit, V.sub.o is an on voltage of the IGBT module when a temperature is at a room temperature of 25° C., R is an on resistance of the IGBT module when the temperature is at the room temperature of 25° C., ΔV is an increment of the on voltage at different temperatures, ΔR is an increment of the on resistance at different temperatures, ΔR′ is an increment of the on resistance when a bonding wire within the IGBT module is broken, R.sub.load is a load resistance, v.sub.o.sup.max is an on voltage value at a maximum temperature T.sup.max given in a data sheet, V.sub.o.sup.typ is the on voltage value at a typical temperature T.sup.typ given in the data sheet, R.sup.max is an on resistance value at the maximum temperature T.sup.max given in the data sheet, R.sup.typ is the on resistance value at the typical temperature T.sup.typ given in the data sheet, T.sub.j is a real-time working temperature of an internal chip of the IGBT module,n represents a coefficient corresponding to a format of how the IGBT modules are coupled in parallel, k.sub.1 and b.sub.1 represent function coefficients of the on voltage changing with temperature, k.sub.2 and b.sub.2 represent function coefficients of the on resistance changing with temperature, ΔT.sub.j represents an increment of a junction temperature caused by different failure processes, P.sub.loss represents a power loss of the IGBT module, which comprises a switching power loss P.sub.sw and a conduction power loss P.sub.cond, r.sub.jc represents a thermal resistance of the IGBT module from a chip to a case, T.sub.C represents the case temperature of the IGBT module, and Δr.sub.jc represents an increment of the thermal resistance caused by different failure processes.

16. The system according to claim 15, wherein the controller is configure to execute the failure determination module for obtaining the increment of the on resistance of the abnormal IGBT module at different temperatures from the parallel IGBT health status detection model in a case where the type of abnormality of the abnormal IGBT module is a bonding wire breakage abnormality, and determining whether the increment of the on resistance of the abnormal IGBT module at different temperatures is greater than a preset resistance increment value; wherein if the increment of the on resistance is greater than the preset resistance increment value, it is determined that the abnormal IGBT module fails due to bonding wire breakage, or otherwise, it is determined that the abnormal IGBT module does not fail; and in a case where the type of abnormality of the abnormal IGBT module is a solder layer aging abnormality, the increment of the thermal resistance of the abnormal IGBT module is obtained from the parallel IGBT health status detection model, and whether the increment of the thermal resistance of the abnormal IGBT module is greater than a preset thermal resistance increment value is determined, wherein if the increment of the thermal resistance is greater than the preset thermal resistance increment value, it is determined that the IGBT module fails due to solder layer aging, or otherwise, it is determined that the IGBT module does not fail.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic flowchart of a method according to an embodiment of the disclosure.

(2) FIG. 2 is an equivalent circuit diagram of parallel modules according to an embodiment of the disclosure.

(3) FIG. 3 is a schematic diagram of changes in each branch of a parallel current distribution according to an embodiment of the disclosure.

(4) FIG. 4A is a simulation diagram of the current distribution of each module when 2 bonding wires fall off.

(5) FIG. 4B is a simulation diagram of the current distribution of each module when 4 bonding wires fall off.

(6) FIG. 4C is a simulation diagram of the current distribution of each module when 6 bonding wires fall off.

(7) FIG. 5 is an experimental verification diagram of the collector current distributions of the faulty module and the normal module according to an embodiment of the disclosure, where the left drawing shows the current value of 9.7 A of a module with 6 bonding wires fallen off, and the right drawing shows the current value of 10.8 A of the normal module.

(8) FIG. 6 is a block diagram of a system according to an embodiment of the disclosure.

DETAILED DESCRIPTION OF DISCLOSED EMBODIMENTS

(9) In order for the objectives, technical solutions, and advantages of the disclosure to be clearer, the disclosure is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the disclosure, but not to limit the disclosure. In addition, the technical features involved in the various embodiments of the disclosure described below may be combined with each other as long as there is no conflict therebetween.

(10) FIG. 1 is a schematic flowchart of a method according to an embodiment of the disclosure. The method shown in FIG. 1 includes the following steps.

(11) Step S1: An abnormal IGBT module is determined according to a collector current value of each IGBT module among parallel IGBT modules.

(12) In the embodiment of the disclosure, after all the current values of each IGBT module are measured, the current value of the abnormal module will be less than the current value of a normal module. The module with the smaller current value is the abnormal module.

(13) Specifically, through comparing the collector current value of each IGBT module among the parallel IGBT modules, an IGBT module with the collector current value less than a preset current value is regarded as the abnormal IGBT module.

(14) The preset current value may be determined according to actual requirements, and is not uniquely limited by the embodiment of the disclosure.

(15) Step S2: A collector current value I.sub.c′ of each abnormal IGBT module is extracted and compared with a maximum value I.sub.c among measured collector current values of normal IGBT modules to obtain a current imbalance rate α.

(16) Step S3: An abnormal type of an IGBT module is determined according to a case temperature of each IGBT module among the parallel IGBT modules.

(17) Through comparing the case temperature of each IGBT module among the parallel IGBT modules, an IGBT module with the case temperature less than a preset case temperature value is regarded as an abnormal bonding wire IGBT module, and an IGBT module with the case temperature equal to the preset case temperature value is regarded as an abnormal solder layer IGBT module.

(18) The preset case temperature value may be determined according to actual requirements, and is not uniquely limited by the embodiment of the disclosure.

(19) Step S4: For any abnormal IGBT module, the current imbalance rate and the case temperature of the abnormal IGBT module are brought into a parallel IGBT health status detection model, and whether the abnormal IGBT module fails is determined according to the abnormal type of the abnormal IGBT module.

(20) If the abnormal IGBT module fails, an IGBT device is replaced. If the abnormal IGBT module does not fail, according to the aging method of the abnormal IGBT module, heat dissipation is required to be increased for a solder layer failure, and derating is required for bonding wire breakage.

(21) In the embodiment of the disclosure, a calculation method of the current imbalance rate in Step S2 is:

(22) $\alpha =\frac{I_C^{\prime }}{I_C},$

(23) where I.sub.C is the maximum value among the measured collector current values of the normal IGBT modules, and I.sub.C′ is the collector current of the abnormal IGBT module.

(24) In the embodiment of the disclosure, the parallel IGBT health status detection model in Step S4 is as follows:

(25) $\frac{I_C^{\prime }}{I_C}=\frac{\left[V_{\mathrm{dc}}-\left(V_o+\Delta V\right)\right]R-\left(n-1\right).Math.R_{\mathrm{load}}.Math.\Delta V}{\left(V_{\mathrm{dc}}-V_o\right)\left(R+\Delta R+\Delta R^{\prime }\right)+R_{\mathrm{load}}.Math.\Delta V}$$\mathrm{If}\Delta V=0,\mathrm{then}\alpha =\frac{R}{R+\Delta R+\Delta R^{\prime }}$$\{\begin{array}{c}\Delta V=\frac{V_o^{\max }-V_o^{typ}}{T^{\max }-T^{typ}}\left(T_j-T^{typ}\right)+V_o^{typ}=k_1\Delta T_j+b_1\\ \Delta R=\frac{R^{\max }-R^{typ}}{T^{\max }-T^{typ}}\left(T_j-T^{typ}\right)+R^{typ}=k_2\Delta T_j+b_2\end{array}{T}_j=P_{loss}.Math.r_{jc}+T_C=\left(P_{sw}+P_{\mathrm{cond}}\right).Math.r_{jc}+T_C\Delta T_j=P_{loss}.Math.\Delta r_{jc}+T_C=\left(P_{sw}+P_{\mathrm{cond}}\right).Math.\Delta r_{jc}+T_C$

(26) where V.sub.dc is the external voltage of the main circuit, V.sub.o is the on voltage of the IGBT module when the temperature is at a room temperature of 25° C., R is the on-resistance of the IGBT module when the temperature is at a room temperature of 25° C., ΔV is the increment of the on voltage at different temperatures, ΔR is the increment of the on-resistance at different temperatures, ΔR′ is the increment of the on-resistance when a bonding wire within the IGBT module is broken, R.sub.load is the load resistance, V.sub.o.sup.max is the on voltage value at a maximum temperature T.sup.max given in a data sheet, V.sub.o.sup.typ is the on voltage value at a typical temperature T.sup.typ (room temperature is normally taken as 25° C.) given in the data sheet, R.sup.max is the on-resistance value at the maximum temperature T.sup.max given in the data sheet, R.sup.typ is the on-resistance value at the typical temperature T.sup.typ (room temperature is normally taken as 25° C.) given in the data sheet, T.sub.j is the real-time working temperature of the internal chip of the IGBT module, n represents the parallel module format, k.sub.1 and b.sub.1 represent the function coefficients of the on voltage changing with temperature, k.sub.2 and b.sub.2 represent the function coefficients of the on-resistance changing with temperature, ΔT.sub.j represents the increment of the junction temperature caused by different failure processes, P.sub.loss represents the power loss of the IGBT module, which includes a switching power loss P.sub.sw and a conduction power loss P.sub.cond, r.sub.jc represents the thermal resistance of the IGBT module from the chip to the case, T.sub.C represents the case temperature of the IGBT module, and Δr.sub.jc represents the increment of the thermal resistance caused by different failure processes. According to current manufacturing processes, the ΔV of most IGBT modules may be considered to be equal to zero.

(27) The data book in the embodiment of the disclosure refers to the data book corresponding to the IGBT module used.

(28) In the embodiment of the disclosure, Step S4 of determining whether the abnormal IGBT module fails according to the abnormal type of the abnormal IGBT module may be implemented through the following manner.

(29) If the abnormal type of the abnormal IGBT module is bonding wire breakage abnormality, the increment of the on-resistance of the abnormal IGBT module at different temperatures is obtained from the parallel IGBT health status detection model. Whether the increment of the on-resistance of the abnormal IGBT module at different temperatures is greater than a preset increment value is determined. If the increment is greater than the preset increment value, it is determined that the abnormal IGBT module fails due to bonding wire breakage. Otherwise, it is determined that the abnormal IGBT module does not fail.

(30) If the abnormal type of the abnormal IGBT module is solder layer aging abnormality, the increment of the thermal resistance of the abnormal IGBT module is obtained from the parallel IGBT health status detection model. Whether the increment of the thermal resistance of the abnormal IGBT module is greater than a preset increment value is determined. If the increment is greater than the preset increment value, it is determined that the IGBT module fails due to solder layer aging. Otherwise, it is determined that the IGBT module does not fail.

(31) The IGBT device failure standard is based on the general standard of the IGBT industry. The increment of the thermal resistance or the on-resistance of each abnormal IGBT module at different temperatures may be obtained from the parallel IGBT health status detection model, and the thermal resistance or conduction of each abnormal IGBT module can be determined. Whether the increment of the thermal resistance or the on-resistance of each abnormal IGBT module is greater than the preset increment value is determined. If the increment is greater than the preset increment value, it is determined that the current IGBT module fails according to the abnormal type. Otherwise, it is determined that the current IGBT module does not fail.

(32) The preset increment value may be determined according to actual requirements, and is not uniquely limited by the embodiment of the disclosure. At present, according to relevant standards: it may be determined that the IGBT module fails if the thermal resistance or the on-resistance increases by 20% (that is, when the thermal resistance or the on-resistance increases to 1.2 times the original resistance value). It may be inferred that the device fails when the current imbalance rate is less than 83%.

(33) The equivalent circuit of each branch in parallel is as shown in FIG. 2. The electrical characteristics of each IGBT module may be represented by a resistor and a voltage source respectively simulating the on-resistance and on voltage drop, and the bonding wires may be represented by multiple resistors in parallel. When one of the bonding wires falls off, the total resistance of the branch thereof rises, causing uneven current distribution, which is the basic principle of the disclosure.

(34) The principle of parallel current distribution is as shown in FIG. 3. When the solder layer melts, the junction temperature rises. Due to the positive temperature effect of the module, the collector current decreases, which causes the current of other modules to increase, resulting in unbalanced current distribution. The decreased current weakens the effect of the junction temperature rise, thereby forming a dynamic balance in the negative feedback. The falling off of the bonding wire directly causes the on-resistance to rise, thereby decreasing the collector current of the corresponding branch.

(35) FIGS. 4A-4C are simulation result diagrams of collector current distributions of a faulty module and a normal module according to an embodiment of the disclosure. Specifically, FIG. 4A is the simulation diagram of the current distribution of each module when 2 bonding wires fall off. FIG. 4B is the simulation diagram of the current distribution of each module when 4 bonding wires fall off. FIG. 4C is the simulation diagram of the current distribution of each module when 6 bonding wires fall off. FIG. 5 is an experimental verification diagram of the collector current distributions of the faulty module and the normal module according to an embodiment of the disclosure, where the left drawing shows the current value of 9.7 A of a module with 6 bonding wires fallen off, and the right drawing shows the current value of 10.8 A of the normal module. In FIG. 4 and FIG. 5, the falling off of different numbers of bonding wires is used to simulate different degrees of aging of the modules.

(36) As shown in FIG. 6, in another embodiment of the disclosure, a system for online monitoring of a health status of an IGBT module is also provided, which includes the following.

(37) An abnormality determination module 201 is configured to determine an abnormal IGBT module according to a collector current value of each IGBT module among parallel IGBT modules.

(38) A current imbalance rate calculation module 202 is configured to extract the collector current value of each abnormal IGBT module to be compared with a maximum value among measured collector current values of normal IGBT modules to obtain a current imbalance rate of each abnormal IGBT module.

(39) An abnormal type determination module 203 is configured to determine an abnormal type of an IGBT module according to a case temperature of each IGBT module among the parallel IGBT modules.

(40) A failure determination module 204 is configured to bring the current imbalance rate and the case temperature of the abnormal IGBT module into a parallel IGBT health status detection model for any abnormal IGBT module, and determine whether the abnormal IGBT module fails according to the abnormal type of the abnormal IGBT module.

(41) For the specific implementation of each module, reference may be made to the descriptions of the foregoing embodiment of the method, and the embodiment of the disclosure will not be reiterated.

(42) In another embodiment of the disclosure, a computer-readable storage medium stored with a program instruction is also provided. When the program instruction is executed by a processor, the method for online monitoring of the health status of the IGBT module as described above is implemented.

(43) Through real-time current monitoring, the health status of each module may be effectively evaluated. At the potential failure stage, the health status of the device is real-time monitored to prevent the loss of the entire system due to the device failure.

(44) The disclosure is simple to implement, has relatively high monitoring precision, has relatively high monitoring sensitivity especially for falling off of internal bonding wires of a module, has relatively good real-time performance, and can online monitor the health status of the IGBT.

(45) It should be pointed out that according to the implementation requirements, each step/component described in the present application may be split into more steps/components, or two or more steps/components or partial operations of a step/component may be combined into a new step/component to implement the objectives of the disclosure.

(46) The method according to the disclosure may be implemented in hardware or firmware, implemented as software or computer code that may be stored in a recording medium (such as CD ROM, RAM, floppy disk, hard disk, or magneto-optical disk), or implemented as computer code that is originally stored in a remote recording medium or a non-transitory machine-readable medium that is downloaded through the network and is stored in a local recording medium, so that the method may be stored in such software processing on a recording medium using a general-purpose computer, a special-purpose processor, or a programmable or special-purpose hardware (such as an application-specific integrated circuit, ASIC or field programmable gate array, FPGA). It may be understood that a computer, processor, microprocessor controller, or programmable hardware includes a storage assembly (such as RAM, ROM, flash memory, etc.) that may store or receive software or computer code. When the software or computer code is accessed and executed by the computer, processor, or hardware, the processing method described here is implemented. In addition, when a general-purpose computer accesses the code for implementing the processing shown here, the execution of the code converts the general-purpose computer into a special-purpose computer for executing the processing shown here.

(47) Persons skilled in the art may easily understand that the above descriptions are only preferred embodiments of the disclosure and are not intended to limit the disclosure. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the disclosure should be included in the protection scope of the disclosure.