Power Management and Control of Single-Stage, Grid-Tied, Self Supportive PVEG-BES System

This paper presents a three-phase, four-wire, single-stage, utility-connected, photovoltaic energy generation-battery energy storage (PVEG-BES) system with smooth auto-changeover capabilities between on-grid and off-grid conditions for power assurance to connected critical loads. A modified voltage and current based perturbation algorithm track maximum power point promptly even on simultaneous/separate changes in load and irradiance. In grid following mode, power requirements of load are satisfied by PV, BES and grid in accordance with the power management algorithm depending on the level of irradiation ensuring that the surplus/deficit power is fed to/drawn as active power from the utility side. The voltage source converter functions as a multifunctional device which also provides reactive power demand of non-linear loads locally and compensates for current harmonics through the neutral line to keep the grid current sinusoidal. Variable step size gradient descent total least square (VSS-GDTLS) method is used to extract fundamental weight component of load current. In the event of fault occurrence at the utility end, PVEG-BES system immediately separates itself from the utility end through a smart controller taking the system goes into grid-forming mode. Modified reduced-order generalised integratorsuper twisting algorithm-frequency locked loop (MROGI-STAFLL) effectively measures amplitude, frequency and phase in accordance to IEEE-1547 and ensures system islanding and auto re-synchronisation with three-phase, AC mains. A proper power management methodology is incorporated in this investigation to prevent BES system from being overcharged/deep discharged. The complete system along with control algorithm is validated under various operating conditions in MATLAB environment and the total harmonic distortion (THD) of grid current and voltage at the common point of interconnection of utility, load and PVEG-BES system is within range as per IEEE-1547 respectively.