The last decade has witnessed a growing demand for replacing conventional generation by power plants based on renewable energy sources, which are connected to the grid through converting devices (inverters). A distinctive feature of such devices that the inertia moment notion is not applicable to them. In addition, some of their components were not originally meant for full-valued participation in emergency control. In view of these circumstances, the integration of such power plants into the grid may entail degradation of both the power system stability and power supply reliability level. Using the example of 10 types of 600 A IGBT modules commercially available from three manufacturers [Infineon Technologies AG (Neubiberg, Germany), Elektrovypryamitel JSC (Saransk, Russia), and Fuji Electric (Tokyo, Japan)], the limit transistor collector current loads at which the semiconductor thermal destruction occurs as a consequence of its inadmissible overheating caused by conductivity heat release are estimated. The thermoelectric analysis was carried out in the Matlab/Simulink environment based on IGBT thermoelectric models. The performed simulation has shown a high degree of IGBT safety margin in terms of collector current (on average 275% of its maximum continuous value). If necessary, this value can be increased further by upgrading (forcing) the cooling system or shifting to a higher gate--emitter voltage, which allows the load range to be widened by about 30–50 percentage points. The study results have shown a high IGBT overload capacity in terms of heating the transistors by the current passing through them (a power source connected to the grid through an inverter can experience overloads, in terms of its thermal operation mode, commensurable with those of standard generating equipment). In view of the high IGBT overload capacity in terms of heating, other restrictions will be the governing ones, in particular, for the transistor safe operation range, which should be taken into consideration when initially choosing, if necessary, transistors for a higher collector current.