Research on the None-Inner-Loop Synchronverter Control Based on the Cascaded H-Bridge (CHB) Converter

To ensure the stable operation of the power system with a high proportion of new energy, grid-forming (GFM) converters have gradually become the research hotspot. The cascaded H-bridge (CHB) converter has a certain research value due to its modular structure that allows flexible capacity expansion and avoids the resonance issues caused by the parallel operation in traditional grid-connected converters. This paper mainly focuses on the none-inner-loop synchronverter control strategy based on the CHB converter and demonstrates that, compared with the mainstream virtual synchronous generator (VSG) control strategy based on the conventional two-level converter, the circuit structure is closer to the stator electrical characteristics of a synchronous generator. It exhibits better small-signal stability within a wide range of grid short circuit ratios (SCR) and superior grid-supporting performance under grid voltage disturbances. Finally, the simulation verifications of stability and grid-supporting performance are completed through Matlab/Simulink.