Abstract: A method to extract the equivalent thermal resistance parameters of double-sided water-cooled

heatsink was proposed. Based on this method，the real-time calculation of junction temperature and overtemperature protection of integrated gate commutation transistor（IGCT）power device were implemented by the water-cooled cooling system. The direct thermal resistance and coupling thermal resistance of the front and back sides of the heatsink were calculated based on the data of heat dissipation power and temperature rise obtained from the simulation or experiment results of the thermal design software. The direct thermal resistance，coupling thermal resistance，power device power consumption and internal thermal resistance of water-cooled heat sink were substituted into the model of water-cooled cooling system，and the power consumption and temperature rise of each power device could be calculated independently in real time. This method takes into account the real-time variation of the heating power of the power device and the thermal coupling effect of the water-cooled heatsink in the application of multi-stage series pressing system，can accurately estimate the junction temperature of power device.

      Key words: integrated gate commutation transistor（IGCT）；thermal model；junction temperature calculation；water-cooled heatsink