With the improvement of electronic equipment integration, the thermal management of key power devices such as IGBT in grid-connected energy storage converter has become an urgent problem to be solved in related design. Based on the transient thermal simulation technology, this paper uses COMSOL software to study the temperature distribution under overload conditions for the three-level grid-structured energy storage converter, and simulates the temperature field change process of the converter under different overload multiples and overload durations. The temperature distribution characteristics and variation laws of key areas such as power devices and heat dissipation structures are analyzed. The research results reveal the dynamic evolution mechanism of the internal temperature of the converter cabinet under overload conditions, and clarify the location and causes of temperature hot spots, which provides theoretical basis and data support for the optimization of heat dissipation design, overload capacity improvement and safe operation of the three-level grid-connected energy storage converter cabinet.