Junction Temperature Estimation Based on Updating RC Network for Different Liquid Cooling Conditions

The failure of power converters and inverters due to thermal stress can threaten the safety and reliability of electrical vehicles (EVs). Junction temperature estimation for power devices is the key factor to maintain safe operation and to extend power device lifetime. This paper proposes a detailed transient Foster thermal model with updating RC parameters at 216 cooling conditions based on coolant flowrate (5L/min to 10.5L/min) and coolant temperature (5°C to 90°C) since the liquid coolant is the major heat dissipating path in the module. The vehicle controller can store and keep updating these 216 RC values based on the coolant temperature and coolant flowrate measurements to provide accurate online IGBT junction temperature estimation. Test data from supplier is used to validate the model at selected operating points.