Control of a Grid-Tied Battery-Less Two-Stage Solar PV System With Seamless Transition and Autonomous Dispatch Capability
Subhadip Chakraborty, Gaurav Modi, Bhim Singh, Bijaya Ketan Panigrahi
Abstract
This article presents an enhanced fourth order generalized integrator (EFOGI) filter-based control for a grid-tied dual stage solar photovoltaic system (SPVS) with seamless mode transition and autonomous dispatch capability. The SPVS supplies uninterrupted power to the load by automatically regulating the DC link voltage during islanded operation (IO). A modified frequency locked loop (MFLL) is proposed, which reduces the frequency overshoot because of sudden phase angle jump in load voltage during synchronization process. The MFLL also reduces the second harmonic ripple present in the estimated frequency during distorted grid conditions and enables efficient estimation of the frequency. Hence, the MFLL reduces the number of false tripping of the power electronic switch (PES) and helps the SPVS to achieve smooth synchronization with the grid. The EFOGI-MFLL algorithm ensures efficient filtering of the load currents and improves the power quality of the SPVS in presence of nonlinearity or load current unbalance, without compromising the dynamic performance of the SPVS. During IO, the EFOGI filter ensures that the point of interconnection (PIC) voltages are linear, making the SPVS immune to any distortions in load currents. Furthermore, it blocks the DC offsets present in the sensed signals, which enhances its filtering ability. A comparative analysis demonstrates the advantages of the EFOGI-MFLL algorithm compared to other generalized integrator (GI) control algorithms. Performance of the SPVS with the presented control is shown with simulation and experimental results.