A freely configurable structure of virtual synchronous generator for grid-forming converters

The provision of system support services by converter-interfaced generation (CIG), which were previously assigned to the conventional synchronous generation, is a challenging task extremely necessary for the stable operation and control of modern power systems. The most promising solution in this direction is the application of grid-forming control strategies for the CIG. This paper proposes a CIG' control system based on a freely configurable structure of a virtual synchronous generator (FC-VSG). In this control system, different levels of the inverter control are implemented in parallel, and in order to improve the transient performance and damping properties of CIG, the inertial and governor response are coupled at the inner control level, a voltage regulator is added at the outer control level, as well as the combined use of a virtual damper winding and power system stabilizer is applied. Such solutions made it possible not only to mimic the behavior of a conventional rotating machines, but also to significantly improve the transients' dynamics. To show the effectiveness of the proposed control system, time-domain simulations and experimental case studies have been performed. In addition, the qualitative and quantitative assessment of the dynamic response of the FC-VSG in comparison with both the conventional voltage-controlled VSG structure and the dynamics of a practical synchronous machine have been carried out.