The insulated gate bipolar transistor (IGBT) is the most expensive central component in the converter interior, but it is also one of the most vulnerable to failure. The failure of power electronic system is mainly due to temperature change. Therefore, the accurate extraction of IGBT module junction temperature is the basis of life prediction and reliability evaluation of high-power power conversion equipment. There is a great advantage in the non-invasive process of obtaining junction temperature through the dynamic temperature sensitive electrical parameter method; However, the measurement results are easily interfered with by a single dynamic temperature sensitive electrical parameter method. In this paper, a high-precision IGBT online junction temperature model based on united-parameters is proposed. The single dynamic thermosensitive electrical parameter only considers the change of a certain capacitance or inductance, which leads to the inaccurate measurement. A large number of effective temperature sensitive electrical parameters can be added to the model in order to reduce other disturbances and improve the accuracy and reliability of junction temperature prediction. Firstly, the limitations of each temperature sensitive electrical parameter were determined by comparing the existing temperature sensitive parameter method. Secondly, the appropriate united-parameters can be determined by theoretical analysis and practical verification. Finally, a junction temperature extraction model based on united-parameters was established by multiple linear regression method. Compared with the single dynamic TSEP-junction temperature, the proposed method has advantages in on-line temperature extraction and high precision monitoring.
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