Enhanced Synthetic Inertia Controller for Grid-forming inverter based Virtual Synchronous Condenser

The proliferation of inverter based renewable energy sources (IBR) has inevitably resulted in insufficient inertia within the power system and creates challenges in maintaining stable frequency dynamics. Operating the IBR on maximum power point tracking (MPPT) and relying solely on the energy storage system for emulated inertia is not sufficient to keep the system stable. Despite this, limited efforts have been made to utilize STATCOMs as synchronous condensers, providing one possible approach to emulate the inertia. In response, this article proposes the implementation of a Grid-forming inverter based Virtual Synchronous Condenser (VSCON), which delivers inertia power through the stored energy in the DC-link capacitor and also supports reactive power compensation. The integration of a conventional synthetic inertia controller (SIC) into the VSCON exhibits limitations in handling DC-link dynamics, which can adversely affect overall system performance. To address this, an enhanced synthetic inertia controller (ESIC) is proposed, enabling the sequential handling of multiple frequency events and ensuring stable operation over a wider frequency range without causing over-modulation. Furthermore, the virtual inductor concept is employed to decouple the active and reactive power loops. With an adequate virtual inductance, it also achieves a $29\%$ reduction in the initial RoCoF. Finally, a hardware prototype of a VSCON is developed in the laboratory and validates superiority of the proposed ESIC over the SIC.