Research On Quasi-online Thermal Network Parameter Identification Method Of IGBT

Advances in power conversion technology have enabled power converters widely using in various industrial fields. However, the survey research of industry shows that the reliability of power device in converter system is increasingly prominent. Further studies show that, no matter the condition monitor and state control, both of them are closely related to the thermal network parameters of the power device, so identifying the thermal network parameters online or quasi online is essential. This paper is manly focusing on quasi-online thermal network parameters identification of IGBT.Firstly, this paper research on quasi-online thermal network parameters identification of IGBT and propose the identification method relying on cooling junction temperature when the converter cuts off at two different cooling conditions. Converting the thermal parameter identification to the electrical parameter identification according to electrical-thermal analogy and analyzing the relationship between the time constants of cooling junction temperature and thermal parameters in equivalent Cauernetwork, we can conclude that the thermal parameters cannot be identified with only one junction temperature curve. On this basis, regarding the real converter system as background, in order to achieve quasi-online identification, we can get more information about thermal network parameters and time constants of junction temperature by changing the cooling condition before the converter shuts off. The theoretical analysis shows that: With two junction temperature curves at different cooling conditions after the converter cuts off, if the thermal resistance parameter of heatsink in cooling conditions can be test, the Cauer-network quasi-online thermal parameter identification can be achieved.Secondly, considering the aging factors of heatsink, this paper propose the method of quasi-online thermal parameter identification relying on cooling junction temperature curves when the converter cuts off at three different cooling conditions. Industry survey suggest that aging and degradation factors is existed in heatsink during the working process of converter and the thermal parameters will be changed comparing to the initial value. So, on the premise of heatsink thermal parameters are unpredictable,this paper analyses the relationship between the thermal network parameters identifiability and the time constants of junction temperature curves at different cooling conditions and then proposes the identification method relying on cooling junction temperature when the converter cuts off at three different cooling conditions. The theoretical analysis shows that: for the 3th-order thermal network Cauer type, this method could realize quasi-online thermal parameter identification considering the effects of aging.Finally, in order to verify the above theory, experimental analysis has be carried on in this article. In this regard, we choose the half-bridge modules of Infineon and select one of IGBT as experimental subject and design the equivalent measurement circuit. According to the theory presented above, parameters identification are carried out and analysis the results viewing the JESD51-14 as the benchmarking. Experimental results show that: the proposed method could achieve the quasi-online thermal network parameters identification of power device.