Design and analysis of different PLLs as load compensation techniques in 1-Ø grid-tied PV system

摘要

This paper discusses the design, modelling and analysis of a single-phase grid-tied photovoltaic (PV) system feeding a variety of loads. Normally, the phase-locked loop (PLL) circuits are used for synchronisation purposes and generation of in-phase and quadrature templates. However, this paper presents an interesting application of PLLs for achieving load compensation for power quality improvement as well as estimation of phase and frequency. Three PLL algorithms are considered which include the conventional Delay PLL, Enhanced PLL and Second-Order Generalised Integrator Frequency-Locked Loop (SOGI-FLL). Design and modelling of controllers using these PLLs for achieving power quality improvement is also presented in the paper. Suitable comparisons are drawn to investigate the performance of different PLLs for two purposes viz. grid synchronisation and achieving compensation in a single-phase grid-tied PV system. Finally, the application of SOGI-FLL for control of a 5 kW PV interfaced single-phase compensator for power quality improvement is presented. Appropriate experimental results are shown along with simulation results for suitable comparison.