A Seamless Enhancing Grid Stiffness Control Strategy for Harmonic Compensation and Power Ripple Mitigation in Grid-Tied Virtual Synchronous Generator System

Grid-forming inverters (GFMIs) are crucial for grids experiencing higher penetration of photovoltaics. Uncertainties in the utility grid make the GFMI system unstable. Thus, using a virtual synchronous generator (VSG) enhances system stability and grid stiffness by reducing the rate of change of frequency (RoCoF). Thus to deal with harmonics and oscillations caused by various uncertainties in the system, this article proposes an elevated adaptive integrated control strategy (EAICS) for a three-phase grid-tied VSG (TPGTVSG) system, which integrates a modified proportional resonant current (MPRC) controller and a phase-corrected reference current (PCRC) generator to further improve overall system performance. The MPRC controller also includes an adaptive power control for the VSG, which helps to reduce the injected grid current harmonics and dampens the power and frequency oscillations under distorted/unbalanced grid voltage conditions. Whereas, the PCRC serves the purpose of synchronization without a dedicated synchronization unit, thereby making the TPGTVSG self-synchronizing and thus reducing the computational burden and complexity. Furthermore, the grid frequency adaptability of the TPGTVSG system is enhanced by suitably modifying the control coefficients used in the VSG power control loop, thereby stabilizing the power oscillations. Additionally, the article also presents a small signal modeling analysis of VSG to examine how parameter perturbations affect power and system frequency. Finally, the suggested EAICS controller response to the system is examined experimentally using a laboratory prototype.