An efficient technique for controlling power flow in a single stage grid-connected photovoltaic system

Abstract

Compared to multistage grid-connected photovoltaic system (GCPVS), complexity in monitoring and controlling scheme in a single-stage GCPVS is much increased as maximum power point tracking and power sharing with the grid need to be considered simultaneously in the same stage. An efficient technique, for performing aforementioned functions simultaneously, in a single stage system by adjustment of voltage phasor of a voltage source inverter is presented. Active and reactive power flow from inverter is regulated by adjustment of amplitude and phase angle of inverter output voltage with respect to grid voltage. An algorithm is also developed for automatic active and reactive powers sharing for the intended applications in the single stage GCPVSs. A typical 2.8 kWp, 368 V (DC) nominal photovoltaic array based GCPVS is modeled and simulated to analyze proper load matching for different ambient and grid voltage conditions. Performances like efficiency of the inverter, total harmonic distortion of inverter output voltage and current are studied with the variation of ambient conditions and modulation index of sinusoidal pulse width modulation of the IGBT based inverter. Simulation results have been included to show the feasibility of the proposed technique.