Change of terminal characteristics of a Voltage-source-inverter (VSI) due to semiconductor device degradation

In this paper, physics-based IGBT and diode models are used to simulate two 3-phase VSI systems using different power modules in SABER. The device parameters for two standard SEMIKRON power modules, the 1200 V/75 A single chip module and the 1200 V/300 A multi-chip module, are extracted following parameterization procedure. The effects of three typical degradations are considered, including solder fatigue, gate aging and sub-chip loss resulting from bond wire lift-off, which have different impacts on the device internal parameters and external characteristics. Device parameters, e.g. R_th, V_th and chip active area are changed correspondingly in the simulation to represent the aging effects and a series of simulation runs are performed for an inverter system. Four aspects of converter terminal characteristics are investigated to identify any measurable signature used for condition monitoring (CM): the module case temperature, the output current harmonics, the phase-leg resistance and the dv/dt values associated with the rising and falling edges of the PWM output voltage. Theoretical analyses backed by simulation results are presented regarding the possibility of a practical CM scheme.