Electro-thermal Coupling Researches On High Power Inverters Based On The IGBT Switching Dynamic Performance Offline Test System

The electro-thermal coupling researches on high power inverters can play an important role in the device selection and application, heatsink design, inverter structure optimization, and benefit the inverter system stability. So the paper covers electrical and thermal fields, establishes high power inverter loss model and the thermal characteristic equivalent network, and obtains the systematic electro-thermal coupling model.In electrical fields, the medium and high voltage power IGBT switching dynamic performance offline test system can provide the device switching dynamic performances under different working conditions, such as blocking voltages, collector currents, device junction temperatures, loop circuit stray inductances and drive voltages/resistances. So based on the offline test system, on one hand, the paper establishes a multi-dimensional IGBT switching dynamic performance database to provide precise data for the loss calculation; on the other hand, it analyzes different topology commutation modes, modulation methods and loads under the inverter’s actual working conditions to simulate the device working condition more accurately, At last, the device and circuit level researches are combined in a quasi-online way, and the switching energy losses in real inverter operations are calculated. The quasi-online modeling gets fairly good consistency with the measured loss, which proves the validity of the modeling method.In thermal fields, the structure and material’s thermal characteristics of IGBT module package and heatsink are also investigated. Through the Finite Element Method (FEM), the IGBT module and heatsink’s transient thermal impedance curves are obtained, which are similar to the ones in the manufacturer’s datasheets. And the curve comparisons under different ambient temperatures and power losses clarify its stability and versatility. Exacting the transient thermal impedance can help to set up the thermal characteristic equivalent network. Based on the medium and high voltage power IGBT offline test system,"instantaneous loss" model is obtained. After the derivation of the thermal resistance and capacitance of the IGBT module and heatsink, the thermal characteristic equivalent network is set up. At last, the electro-thermal coupling model can be established. The model can predict the device dynamic junction temperature under different working conditions, and ensure the system safe and stable operation.