Extended FOGI-FLL Based Seamless Control of Grid Synchronized BES-PV Fed Water Pump System

A battery energy storage (BES) and photovoltaic (PV) array powered grid-connected water pump system (WPS) becomes an island during outage of the grid. On the grid recovery, it is necessary to synchronize WPS to the grid to achieve advantages of grid-integration like increased system utilization and prolonged water pumping. Hence, a frequency locked-loop (FLL) based on extended fourth-order generalized integrator (eFOGI) to facilitate reconnection of WPS to the grid is developed in this work. The developed eFOGI-FLL eliminates DC-offset along with dominant low-order harmonics unlike existing generalized integrator based FLL. The eFOGI-FLL, consisting of two cascaded notch-filters, is tuned to fundamental, fifth and seventh harmonic frequencies, and thus, it passes fundamental component and blocks two harmonics. Besides, eFOGI based quadrature signal generator (QSG) is used to implement control for grid-interfaced converter in grid-connected and islanded modes. While eFOGI-QSG based sensorless control of permanent magnet synchronous motor, which is used to operate WPS, is also developed to eliminate position sensor. The benefits of eFOGI-FLL are highlighted by performing its in-depth analysis. Experimental behavior of WPS in several operating scenarios are reported to show effectiveness of developed control techniques.