Electro-Thermal Modeling and Thermal Analysis of High-Inertia Synchronous Condenser Converters

High-inertia energy storage synchronous condenser (HI-ES-SC) is operated through rotor-excited variable-speed mechanisms to provide grid power support. Power devices are exposed to alternating electro-thermal stresses, with significant implications for system reliability. Therefore, an electro-thermal modeling approach is developed for the converter of HI-ES-SC during power support operation. Switching dynamics and conduction states are incorporated in the model. A theoretical framework is established to analyze loss mechanisms and junction temperature evolution. A coupled electro-thermal model is constructed, accounting for temperature-dependent thermal network parameters. A numerical solution is proposed to enable co-simulation of condenser–converter systems. The simulation results indicate that the error in thermal parameter estimation remains below 10%. Key findings are summarized as follows: Under active power support, the peak junction temperature is observed to reach 81.69 °C during synchronous speed crossing, accompanied by notable low-frequency thermal accumulation. The derived operational-thermal correlation provides critical guidance for optimal thermal design and device selection.