Cascaded SOGI In-Loop Comb Based Enhanced Phase Estimation Control for a Battery Less Grid-Tied SPVS During Abnormal Grid Conditions

Solar photovoltaic (PV) energy conversion systems are built with an aim to sell solar power to grid and earn excess revenue. With existing economics considering levelized cost and payback period, batteries are still an expensive option which makes choice for systems with energy storage a secondary option. Connected local loads may have distortions, which demeans system power quality performance and increase harmonic losses. It also reduces system power transfer capability for a given rating specification. Moreover, the grid voltage abnormalities like sag/ swell, phase angle jump, distorted/ unbalanced voltages and possible frequency fluctuations also degrades performance of grid connected microgrid applications. System performance can be robustified through proper control of grid tied inverter responsible for renewable energy conversion. Sinusoidal fundamental component extraction helps in achieving accurate control action despite persistent load current/ grid voltage irregularities, and thereby improves power quality indices of renewable energy systems. Accurate estimation of frequency and phase angle also enhances harmonic component filtering ability of filters used for generating reference currents to linearize grid currents. Hence, this work presents a cascaded second order generalized integrator (C-SOGI) with enhanced phase estimation loop with embedded modifications through an in-loop comb (ILC) structure within phase-locked loop (PLL). System performance is compared and verified by simulation results.