A modified line-commutated inverter for grid-connected photovoltaic systems with voltage-based maximum power point tracking method

Abstract

This paper presents a new structure based on a line-commutated inverter (LCI) for photovoltaic (PV) applications. The proposed LCI circuit is able to inject the DC power to the grid at the unity power factor and with reduced harmonic levels. The proposed circuit with voltage-based maximum power point tracking (MPPT) is implemented in grid-connected PV system. The experimental results show that proposed system can extract the maximum power from PV array under varying irradiation levels. Besides, the power factor can be adjusted by modifying firing angle of SCRs. The modified LCI injects sinusoidal currents into the grid, thus the total harmonic distortion (THD) of the grid currents is about 5% or less, which is meet IEEE 1547 grid-connected standard. The results were obtained without any harmonic compensation or filter equipment when compared with the conventional LCI and current source inverter (CSI).