Full-State Virtual Oscillator Control for Grid-forming PVs to Endure Solar Radiation and Grid Disturbances

Abstract

Oscillator-based grid-forming (GFM) methods are getting focused for the global synchronization potential. However, existing methods like dispatchable virtual oscillator control (dVOC) are two-state oscillators, which cannot smoothly handle large disturbances from the primary source or the power grid. This paper presents a full-state virtual oscillator control (fVOC) strategy with frequency and voltage magnitude as extended oscillator states from the dc voltage. Both the theoretical analysis and experimental tests show that the GFM photovoltaic (PV) with fVOC can robustly withstand large disturbances and provide elastic grid support during the fluctuations of solar irradiance, load change or short-circuit fault that result in dc-link power imbalances. The nonlinear model considering primary dynamics is derived to illustrate the enhanced large-signal dc voltage stability of fVOC based PVs. The validity of the proposed method is verified by both numerical simulations and hardware tests.