CC‐ROGI‐FLL based control for grid‐tied photovoltaic system at abnormal grid conditions

Abstract

This study presents a single stage grid-interfaced solar photovoltaic (SPV) system using a multifunctional complex coefficient reduced ordered generalised integrator (CC-ROGI) based frequency-locked loop (FLL) control. The main contributions of this study, include (i) the extrication of fundamental active components from load currents using CC-ROGI-FLLbased control to generate the reference grid currents for voltage source converter (VSC) switching, (ii) VSC works as a distribution static compensator, which performs multi-functions like harmonics mitigation, reactive power compensation, unity power factor operation and grid currents balancing, (iii) this CC-ROGI-FLL also extricates the fundamental grid voltages component even under grid voltage harmonic distortion and grid voltages unbalancing. Moreover, SPV power feed-forward component is assimilated in this control to reduce the oscillations in grid currents under variable irradiance. Simulated and experimental results show satisfactory behaviour of the system at different conditions like load unbalancing, variable solar irradiance and abnormal grid conditions. The comparative performance of CC-ROGI-FLL control with other FLL and phaselocked loop controls are shown in this study. This CC-ROGI-FLL control has manifested a good steady state performance and dynamic response. The total harmonic distortions of grid currents are found well within the limits of the IEEE-519 standard, even under abnormal grid conditions.