Active Thermal Control of Grid-Forming Converters Based on DC-link Voltage Synchronization

Grid-forming control, as a key technology for building new power systems, enables inertia and damping characteristics of converters to actively support grid frequency and voltage. However, GFM-based converters are often required to generate short-circuit currents in excess of the rated value to support grid voltage recovery during transient faults, which poses a greater challenge to their electro-thermal stresses. At the same time, the over-issuance of short-circuit current will lead to the aggravation of junction temperature fluctuation, which will shorten the lifetime of the power devices and bring new challenges to their reliability. Based on the above problems, this paper firstly establishes a corresponding electrothermal coupling model for the GFM converter synchronized based on DC voltage. Subsequently, an active thermal control technique based on the adaptive adjustment of switching frequency is proposed, which can not only reduce the junction temperature of the power device under the same short-circuit current amplitude, but also further reduce the junction temperature fluctuation of the power device. Finally, the corresponding circuit as well as thermal circuit models are established by simulation software to verify the effectiveness of the strategy.