Influence of IGBT Current Rating on the Thermal Cycling Lifetime of a Power Electronic Active Rectifier in a Direct Wave Energy Converter

Direct Wave Energy Converters offer high reliability potential, which is a key factor in offshore environments, yet their electrical power produced is strongly pulsating. The thermal cycling of their power electronic switches (considered here to be Insulated Gate Bipolar Transistors, IGBT) may reduce the lifetime of the power electronic converter. This study proposes a generic design method for choosing both the IGBT current rating and the heatsink thermal resistance in order to satisfy a reliability constraint. A parametric electro-thermal model has thus been developed to determine the junction temperature time series. Moreover, a rainflow cycle counting method is introduced for the reliability analysis and lifetime prediction using two aging models, one for wire bonds, the other for the solder joint of the chip.