Research On The Thermal Network Parameters Identification Method Of SiC MOSFET Module

With the development of power electronics,the application area of power inverters is growing wider.For the new generation,the SiC wide bandgap semiconduct devices led by SiC MOSFET are gradually replacing the traditional Si devices and occupy the market and technology frontier.However,together with efficiency,the issue about reliability of SiC MOSFET devices has also attracted attention.Besdies the failure of the SiC chip itself,the traditional packages designed for Si devices also limit the performance of SiC devices.SiC itself is designed for high-temperature environments.However,the package results in higher thermal stress and therefore SiC MOSFET modules will face serious reliability issues.For this reason,this paper proposes a thermal network parameter identification method based on node temperature information to identify the thermal network parameters of SiC MOSFET modules.The main contents are as follows:Firstly,the paper analyzes the package structure and heat flow path of the SiC MOSFET module.Based on the electro-thermal analogy,thermal analysis is able to be performed by electrical means.A one-dimensional Cauer thermal network model is selected to characterize the heat flow path of the SiC MOSFET module.Then a state space expression of the Cauer thermal network model is established,and the observability of the node temperature to the system is analyzed and verified.Finally,through the calculation in the complex frequency domain,the relationship between the parameters of the Cauer thermal network model and the time constant of the cooling curve of the node is derived.The results show that the Cauer thermal network model parameters of the SiC MOSFET module can be directly calculated and obtained by using the cooling curve of the node.Secondly,by analyzing the temperature measurement points that can be easily observed in the SiC MOSFET module,it is found that the anti-parallel SiC SBD chip and the bottom case temperature of the SiC MOSFET module can be used as the temperature measurement node.Then based on these two nodes,suitable Cauer thermal network models are established respectively.The equations are solved by adding cooling curves under different cooling conditions,and the Cauer thermal network parameter model of the SiC MOSFET module is calculated.Finally,the effects of aging of the cooling system are analyzed and taken into account.The results show that the Cauer thermal network parameters of the SiC MOSFET module can be identified based on the cooling curve of the junction temperature of the SiC SBD chip and the case temperature of the SiC MOSFET module.Finally,in order to verify the above theories and methods,experimental analysis is performed in this paper.By designing the circuit and experiments,based on the Cauer thermal network parameter identification method of the SiC MOSFET module proposed in this paper,the experimental results are obtained.The experimental results are compared with other standard methods,and the simulated aging experiments and the junction temperature estimation comparison experiments are designed.The results show that the proposed method can identify the Cauer thermal network parameters of SiC MOSFET modules.