Junction Temperature Analysis of Press-Pack IG-BTs of Modular Multilevel Converter Based on Electro-Thermal Coupling Model

Press- pack insulated gate bipolar transistor (PP-IGBT) has been being widely used in modular multilevel converter based high voltage direct current (MMC-HVDC) systems. However, after a long-term cyclic thermal stress, the material of the PP-IGBT will gradually encounter fatigue failure, which will affect the reliability of the device. Therefore, information of junction temperature fluctuation is vital for lifetime evaluation of PP-IGBT and stable operation of MMC. In this paper, the power loss of IGBT in the sub-module (SM) of MMC is analyzed firstly, then the thermal network model of PP-IGBT is proposed and established in Simulink. Based on the model, junction temperature characteristics of PP-IGBT are simulated in combination with specific MMC system. Finally, the finite element method (FEM) model is built in COM-SOL to verify the results. The simulation results show that the non-continuous sinusoidal current flowing through IGBT leads to the fluctuation of the junction temperature. The rise rate, transient time, steady-state value and fluctuation range of junction temperature in IGBT are positively correlated with the current flowing through the IGBT. The temperature fluctuation characteristics of the FEM model verify the correctness and effectiveness of thermal network model established in this paper.