Estimation and Validation of Junction Temperature of IGBT for Grid-Connected PV Applications

Recent advances in power electronics have led to increased use of electricity from renewable energy systems, such as photovoltaic (PV) as well as wind energy systems. Developments in power semiconductor technology, i.e. a wide band gap, have increased the conversion efficiency of power electronics to more than 98%, however the dependability with power electronics is becoming a major concern. Junction Temperature is the primary parameter that affects this same reliability of the IGBT. Mission profile (Solar Irradiance & Ambient Temperature) variation throughout junction temperature tends to lead to mechanical failure (Bond wire lift off, solder fatigue etc.). Therefore, in order to assess reliability, the junction temperature needs to be estimated. But the junction temperature cannot be calculated directly, it requires an indirect method of estimation and validation. The 3 kW grid connected to the PV Inverter is however discussed in this paper. PV Inverter consists of four IGW30N60H3 IGBTs from the Infineon manufacturer. Annual mission profile data is logged in Hyderabad, India. Foster electro thermal modeling (ETM) is held out for junction temperature evaluation. Validation for the estimated junction temperature is required as estimated by indirect method. Finally, the estimated junction temperature is validated by correlation with annual solar irradiance, ambient temperature and case temperature.