Inertia Synthesis for AHO Controlled Converters in Smart Transformer Based Distribution Systems

The smart transformer (ST)-based low-voltage distribution systems have lower inertia, primarily due to the lack of rotating machines. This characteristic becomes critical when integrating high levels of renewable-based distributed generation (DG) units. The grid-forming (GFM) control mode in low voltage (LV) converters can apply either virtual synchronous generator or, droop control to coordinate with DGs. However, these control strategies are based on the phasor-domain, and synchronous steady-state needs to be well defined. On the other hand, the virtual oscillator (VO) control is a time-domain based decentralized GFM converter control technique and globally asymptotic stable. In this paper, a virtual inertia (VI)-VO control equipped with a proportional-derivative (PD) controller is pro-posed to generate a response comparable to that of a synchronous generator (SG) inertia. The impact of adjusting the equivalent VO control inertia constant is evaluated through simulation in MATLAB/Simulink software. The simulation and experimental results demonstrate that the proposed VI-VO control enhances frequency characteristics like the rate of change of frequency (RoCoF) and frequency nadir.